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Background: In preclinical studies, multiple myeloma (MM) cells are sensitive to selective inhibition of the pro-survival protein BCL-2 by venetoclax (VEN). Resistance to VEN in these models was mediated through BCL-XL and MCL-1, and MCL-1 mediated resistance was neutralized by co-treatment with the proteasome inhibitor bortezomib (BTZ). MM cells harboring the t(11;14) translocation have a higher ratio of BCL-2 relative to MCL-1 mRNA and increased sensitivity to VEN alone, compared to cells with other cytogenetic abnormalities, suggesting that MM subgroups with a favorable BCL-2 family profile might be particularly sensitive to VEN. Clinically, VEN has shown activity in CLL, a disease typically expressing high BCL-2 and low BCL-XL and MCL-1 expression. In MM, VEN is being evaluated as a single agent (NCT01794520) and in combination with BTZ and dexamethasone (Dex) (NCT01794507, NCT02755597) in relapsed/refractory (R/R) patients. As a single agent, improved objective response rates were observed in patients with R/R t(11;14) MM (40% in t(11;14) vs 6% in non-t(11;14)-). In the BTZ/Dex combination study, patients with high BCL-2 expression had an increased objective response rate. Thus, BCL-2 family profiling may explain increased susceptibility of certain MM subgroups to antitumor activity of VEN both as a single agent and in combination. We analyzed MM subgroups for expression of BCL-2 family members to better understand and identify the patient population that can benefit with VEN. Methods: We used publically available data (GSE4581; GSE9782) to analyze BCL-2 family mRNA expression within molecular/cytogenetic defined subgroups among newly diagnosed (NDMM n=414), and R/R (n=264) MM patients, and in comparison to other hematological malignancies (genealogic database). Results: BCL-2, BCL-XL and MCL-1 expression was assessed in MM and compared with 12 major hematologic malignancies. Based on median expression, BCL-2 in MM ranked 6th of 12 tested, with highest BCL-2 expression observed in small lymphocytic leukemia and mantle cell lymphoma. In MM, BCL-2 expression varied significantly across molecular and cytogenetic subgroups. Highest expression was among patients with t(11;14) molecular subtypes (CD1, CD2), in addition to subtypes that are not enriched with t(11;14) like the hyperdiploid and low bone disease subtypes, and lowest in the high-risk subtypes (proliferation, MMSET, MAF/MAFB) (p=0.0001), both in NDMM and R/R MM. BCL-XL and MCL-1 were highly expressed in MM relative to other hematologic malignancies. Expression of BCL-XL and MCL-1 were lowest in the t(11;14) MM population (both p Conclusions: Our analysis suggests that MM subgroups are associated with distinct BCL-2 family expression profiles, and the t(11;14) subgroup amongst MM subgroups may be particularly suited for single agent VEN activity due to a high BCL-2/MCL-1 and BCL-2/BCL-XL ratio. In the non-t(11;14) MM subgroups, VEN treatment in earlier lines of therapy, as well as combination strategies with agents that will down-modulate BCL-XL and/or MCL-1, such as BTZ, may enable maximum VEN activity, and will be further assessed in clinical studies. Disclosures Wu: Genentech: Employment. Ross:AbbVie: Employment, Equity Ownership. Peale:Genentech: Employment, Equity Ownership. Shaughnessy:Signal Genetics: Consultancy, Equity Ownership. Van Laar:Signal Genetics, Inc.: Employment. Morgan:Takeda: Consultancy, Honoraria; Janssen: Research Funding; Bristol Meyers: Consultancy, Honoraria; Univ of AR for Medical Sciences: Employment; Celgene: Consultancy, Honoraria, Research Funding. Venstrom:Genentech: Employment. Punnoose:Genetech, Inc.: Employment.

Inhibiting angiogenesis has become an important therapeutic strategy for cancer treatment but, like other current targeted therapies, benefits experienced for late-stage cancers can be curtailed by inherent refractoriness or by acquired drug resistance, requiring a need for better mechanistic understanding of such effects. Numerous preclinical studies have demonstrated that VEGF pathway inhibitors suppress primary tumour growth and metastasis. However, it has been recently reported that short-term VEGF and VEGFR inhibition can paradoxically accelerate tumour invasiveness and metastasis in certain models. Here we comprehensively compare the effects of both antibody and small molecule receptor tyrosine kinase (RTK) inhibitors targeting the VEGF-VEGFR pathway, using short-term therapy in various mouse models of metastasis. Our findings demonstrate that antibody inhibition of VEGF pathway molecules does not promote metastasis, in contrast to selected small molecule RTK inhibitors at elevated-therapeutic drug dosages. In particular, a multi-targeted RTK inhibitor, sunitinib, which most profoundly potentiated metastasis, also increased lung vascular permeability and promoted tumour cell extravasation. Mechanistically, sunitinib, but not anti-VEGF treatment, attenuated endothelial barrier function in culture and caused a global inhibition of protein tyrosine phosphorylation, including molecules important for maintaining endothelial cell-cell junctions. Together these findings indicate that, rather than a specific consequence of inhibiting the VEGF signalling pathway, pharmacological inhibitors of the VEGF pathway can have dose- and drug class-dependent side-effects on the host vasculature. These findings also advocate for the continued identification of mechanisms of resistance to anti-angiogenics and for therapy development to overcome it.

To examine the potential of combining Bcl-2 family inhibitors with chemotherapy in ovarian cancer, we evaluated a panel of 27 ovarian cancer cell lines for response to the combination of navitoclax (formerly ABT-263) and paclitaxel or gemcitabine. The majority of cell lines exhibited a greater than additive response to either combination, as determined by the Bliss independence model, and more than 50% of the ovarian cell lines exhibited strong synergy for the navitoclax/paclitaxel combination. To identify biomarkers for tumors likely to respond to this combination, we evaluated the protein levels of intrinsic apoptosis pathway components. Bcl-xL seems necessary, but not sufficient, for navitoclax/paclitaxel synergy in vitro, suggesting that exclusion of patients whose tumors have low or undetectable Bcl-xL would enrich for patients responsive to the combination. We evaluated Bcl-xL levels in ovarian cancer tumor tissue from 40 patients (20 taxane responsive and 20 with poor response to taxane) and found that patients with high Bcl-xL were less sensitive to taxane treatment (10 of 12) Bcl-xL positive patients, P = 0.014). These data support the use of navitoclax in combination with taxane-based therapy in ovarian cancer patients with high levels of Bcl-xL. Mol Cancer Ther; 11(4); 1026–35. ©2012 AACR.

The microvascular endothelium in endocrine glands is very permeable to circulating substances and secretory products, reflecting the need for rapid hormone release in response to homeostatic stimuli. Fenestrae, specialized discontinuities of the endothelial plasma membrane, presumably permit high permeability, but their presence does not strictly correlate with the expression of vascular endothelial growth factor (VEGF). The authors have identified a distinct angiogenic mitogen selective for endocrine-gland endothelium. It is very similar biologically to VEGF and is able to induce fenestration in target cells, but it does not exhibit structural homology with the family of VEGF proteins. Expression of this factor, termed endocrine gland-derived VEGF (EG-VEGF), is largely restricted to steroidogenic glands. When a library of purified human secreted proteins was screened for their ability to promote the proliferation of bovine adrenal cortex-derived endothelial (ACE) cells (which respond to VEGF), EG-VEGF was identified as the only one that could induce a reproducibly strong mitogenic response. The increase in ACE cells exposed to EG-VEGF was very similar to that induced by VEGF, and both of these substances induced fenestration of endothelial cells. The expression of EG-VEGF was induced by hypoxia, which strongly promotes angiogenesis under both physiological and pathological conditions. On testing a wide range of human tissues and cell lines, EG-VEGF was found only in ovary, testis, adrenal, placenta, and (to a lesser degree) prostate. Using adenovirus to deliver EG-VEGF locally in a sustained manner, frank angiogenesis was observed with mitotic endothelial cells, edema, and granulation tissue. EG-VEGF protein was produced at a high level in skeletal muscle. Intraovarian delivery of either EG-VEGF or VEGF adenovirus led to marked enlargement of the ovaries, grossly visible blood vessels, and areas of hemorrhage. Microscopy revealed intense angiogenesis at the periphery of ovarian cysts. Steroidogenic glands may have developed highly specific local mechanisms that serve to "fine tune" the action of the VEGF receptors. EG-VEGF is one of a class of highly specific mitogens that help regulate the proliferation and differentiation of vascular endothelium in a tissue-specific manner. Mitogens specific for cardiac or skeletal muscle endothelium might hold great therapeutic potential.

Purpose Mutation in isocitrate dehydrogenase 1 (IDH1) at R132 (IDH1R132MUT) is frequent in low-grade diffuse gliomas and, within glioblastoma (GBM), has been proposed as a marker for GBMs that arise by transformation from lower-grade gliomas, regardless of clinical history. To determine how GBMs arising with IDH1R132MUT differ from other GBMs, we undertook a comprehensive comparison of patients presenting clinically with primary GBM as a function of IDH1R132 mutation status. Patients and Methods In all, 618 treatment-naive primary GBMs and 235 lower-grade diffuse gliomas were sequenced for IDH1R132 and analyzed for demographic, radiographic, anatomic, histologic, genomic, epigenetic, and transcriptional characteristics. Results Investigation revealed a constellation of features that distinguishes IDH1R132MUT GBMs from other GBMs (including frontal location and lesser extent of contrast enhancement and necrosis), relates them to lower-grade IDH1R132MUT gliomas, and supports the concept that IDH1R132MUT gliomas arise from a neural precursor population that is spatially and temporally restricted in the brain. The observed patterns of DNA sequence, methylation, and copy number alterations support a model of ordered molecular evolution of IDH1R132MUT GBM in which the appearance of mutant IDH1 protein is an initial event, followed by production of p53 mutant protein, and finally by copy number alterations of PTEN and EGFR. Conclusion Although histologically similar, GBMs arising with and without IDH1R132MUT appear to represent distinct disease entities that arise from separate cell types of origin as the result of largely nonoverlapping sets of molecular events. Optimal clinical management should account for the distinction between these GBM disease subtypes.

Priming of the organ-specific premetastatic sites is thought to be an important yet incompletely understood step during metastasis. In this study, we show that the metastatic tumors we examined overexpress granulocyte-colony stimulating factor (G-CSF), which expands and mobilizes Ly6G+Ly6C+ granulocytes and facilitates their subsequent homing at distant organs even before the arrival of tumor cells. Moreover, G-CSF–mobilized Ly6G+Ly6C+ cells produce the Bv8 protein, which has been implicated in angiogenesis and mobilization of myeloid cells. Anti–G-CSF or anti-Bv8 antibodies significantly reduced lung metastasis. Transplantation of Bv8 null fetal liver cells into lethally irradiated hosts also reduced metastasis. We identified an unexpected role for Bv8: the ability to stimulate tumor cell migration through activation of one of the Bv8 receptors, prokineticin receptor (PKR)-1. Finally, we show that administration of recombinant G-CSF is sufficient to increase the numbers of Ly6G+Ly6C+ cells in organ-specific metastatic sites and results in enhanced metastatic ability of several tumors.

An “uncorrected” version of the following article was published in the June 2010 issue of MRM. The corrected version of the article is provided here. The publisher regrets the error. Imaging of tumor microvasculature has become an important tool for studying angiogenesis and monitoring antiangiogenic therapies. Ultrasmall paramagnetic iron oxide contrast agents for indirect imaging of vasculature offer a method for quantitative measurements of vascular biomarkers such as vessel size index, blood volume, and vessel density (Q). Here, this technique is validated with direct comparisons to ex vivo micro-computed tomography angiography and histologic vessel measurements, showing significant correlations between in vivo vascular MRI measurements and ex vivo structural vessel measurements. The sensitivity of the MRI vascular parameters is also demonstrated, in combination with a multispectral analysis technique for segmenting tumor tissue to restrict the analysis to viable tumor tissue and exclude regions of necrosis. It is shown that this viable tumor segmentation increases sensitivity for detection of significant effects on blood volume and Q by two antiangiogenic therapeutics [anti-vascular endothelial growth factor (anti-VEGF) and anti-neuropilin-1] on an HM7 colorectal tumor model. Anti-vascular endothelial growth factor reduced blood volume by 36 ± 3% (p < 0.0001) and Q by 52 ± 3% (p < 0.0001) at 48 h post-treatment; the effects of anti-neuropilin-1 were roughly half as strong with a reduction in blood volume of 18 ± 6% (p < 0.05) and a reduction in Q of 33± 5% (p < 0.05) at 48 h post-treatment. Magn Reson Med 63:1637–1647, 2010. © 2010 Wiley-Liss, Inc.

Purpose: Little is known concerning the onset, duration, and magnitude of direct therapeutic effects of anti–vascular endothelial growth factor (VEGF) therapies. Such knowledge would help guide the rational development of targeted therapeutics from bench to bedside and optimize use of imaging technologies that quantify tumor function in early-phase clinical trials. Experimental Design: Preclinical studies were done using ex vivo microcomputed tomography and in vivo ultrasound imaging to characterize tumor vasculature in a human HM-7 colorectal xenograft model treated with the anti-VEGF antibody G6-31. Clinical evaluation was by quantitative magnetic resonance imaging in 10 patients with metastatic colorectal cancer treated with bevacizumab. Results: Microcomputed tomography experiments showed reduction in perfused vessels within 24 to 48 h of G6-31 drug administration (P ≤ 0.005). Ultrasound imaging confirmed reduced tumor blood volume within the same time frame (P = 0.048). Consistent with the preclinical results, reductions in enhancing fraction and fractional plasma volume were detected in patient colorectal cancer metastases within 48 h after a single dose of bevacizumab that persisted throughout one cycle of therapy. These effects were followed by resolution of edema (P = 0.0023) and tumor shrinkage in 9 of 26 tumors at day 12. Conclusion: These data suggest that VEGF-specific inhibition induces rapid structural and functional effects with downstream significant antitumor activity within one cycle of therapy. This finding has important implications for the design of early-phase clinical trials that incorporate physiologic imaging. The study shows how animal data help interpret clinical imaging data, an important step toward the validation of image biomarkers of tumor structure and function. (Clin Cancer Res 2009;15(21):6674–82)

Imaging of the glial activation that occurs in response to central nervous system trauma and inflammation could become a powerful technique for the assessment of several neuropathologies. The selective uptake and metabolism of 2-18F-fluoroacetate (18F-FAC) in glia may represent an attractive strategy for imaging glial metabolism. Methods: We have evaluated the use of 18F-FAC as a specific PET tracer of glial cell metabolism in rodent models of glioblastoma, stroke, and ischemia–hypoxia. Results: Enhanced uptake of 18F-FAC was observed (6.98 ± 0.43 percentage injected dose per gram [%ID/g]; tumor-to-normal ratio, 1.40) in orthotopic U87 xenografts, compared with healthy brain tissue. The lesion extent determined by 18F-FAC PET correlated with that determined by MRI (R2 = 0.934, P = 0.007). After transient middle cerebral artery occlusion in the rat brain, elevated uptake of 18F-FAC (1.00 ± 0.03 %ID/g; lesion-to-normal ratio, 1.90) depicted the ischemic territory and correlated with infarct volumes as determined by 2,3,5-triphenyltetrazolium chloride staining (R2 = 0.692, P = 0.010) and with the presence of activated astrocytes detected by anti–glial fibrillary acidic protein. Ischemia–hypoxia, induced by permanent ligation of the common carotid artery with transient hypoxia, resulted in persistent elevation of 18F-FAC uptake within 30 min of the induction of hypoxia. Conclusion: Our data support the further evaluation of 18F-FAC PET for the assessment of glial cell metabolism associated with neuroinflammation.

Purpose To develop magnetic resonace imaging (MRI) methods for functional assessment of arteriogenesis in a murine model of peripheral artery disease to quantify the influences of vascular endothelial growth factor (VEGF), age, and atherosclerosis. Materials and Methods Reactive hyperemia (RH), which was induced using a device designed for remote and transient occlusion of the aorta and vena cava, was measured by blood-oxygen-level–dependent MRI. Twenty-eight days after femoral artery ligation, peak height (PH) and time to peak (TTP) of the RH response was compared with sham-operated animals in 10-week-old C57Bl6, 9-month-old C57Bl6, and 9-month-old Ldlr−/−Apobec−/− mice. The contribution of VEGF to functional recovery was assessed in young mice. Angiogenesis was quantified using an anti-PECAM1 radioimmunoassay. Results In young animals, angiogenesis was maximal 7 days after ligation, whereas functional recovery took 28 days. Inhibition of VEGF eliminated the angiogenesis seen at 7 days and reduced RH (PH, P < 0.05). At day 28, RH was altered in old (TTP, P < 0.05) and atherosclerotic (PH, P < 0.05; TTP, P < 0.05) animals. RH was different in young, old, and atherosclerotic sham animals. Old and atherosclerotic mice showed reduced angiogenesis. Conclusion The method presented herein can provide a sensitive assay for the functional assessment of arteriogenesis and highlights the contribution of VEGF, age, and atherosclerosis to this process. J. Magn. Reson. Imaging 2008;28:996–1004. © 2008 Wiley-Liss, Inc.

Purpose: Multiple endocrine neoplasia type 1 (MEN1) is defined clinically by the combined occurrence of multiple tumors, typically of the parathyroid glands, pancreatic islet cells, and anterior pituitary gland. A mouse model with a heterozygous deletion of the Men1 gene recapitulates the tumorigenesis of MEN1. We wished to determine the role of vascular endothelial growth factor (VEGF)-A in the vascularization and growth of MEN1-associated tumors, with an emphasis on pituitary adenomas. Experimental Design: To investigate whether tumor growth in Men1+/− mice is mediated by VEGF-A dependent angiogenesis, we carried out a monotherapy with the anti–VEGF-A monoclonal antibody (mAb) G6-31. We evaluated tumor growth by magnetic resonance imaging and assessed vascular density in tissue sections. We also measured hormone levels in the serum. Results: During the treatment with mAb G6-31, a significant inhibition of the pituitary adenoma growth was observed, leading to an increased mean tumor doubling-free survival compared with mice treated with a control antibody. Similarly, the growth of s.c. pituitary adenoma transplants was effectively inhibited by administration of anti–VEGF-A mAb. Serum prolactin was lowered by mAb G6-31 treatment but not by control antibody, potentially providing a new therapeutic approach for treating the hormonal excess in MEN1 patients. Additionally, the vascular density in pancreatic islet tumors was significantly reduced by the treatment. Conclusions: These results suggest that VEGF-A blockade may represent a nonsurgical treatment for benign tumors of the endocrine system.

Bone-marrow-derived cells facilitate tumour angiogenesis, but the molecular mechanisms of this facilitation are incompletely understood. We have previously shown that the related EG-VEGF and Bv8 proteins, also known as prokineticin 1 (Prok1) and prokineticin 2 (Prok2), promote both tissue-specific angiogenesis and haematopoietic cell mobilization. Unlike EG-VEGF, Bv8 is expressed in the bone marrow. Here we show that implantation of tumour cells in mice resulted in upregulation of Bv8 in CD11b+Gr1+ myeloid cells. We identified granulocyte colony-stimulating factor as a major positive regulator of Bv8 expression. Anti-Bv8 antibodies reduced CD11b+Gr1+ cell mobilization elicited by granulocyte colony-stimulating factor. Adenoviral delivery of Bv8 into tumours was shown to promote angiogenesis. Anti-Bv8 antibodies inhibited growth of several tumours in mice and suppressed angiogenesis. Anti-Bv8 treatment also reduced CD11b+Gr1+ cells, both in peripheral blood and in tumours. The effects of anti-Bv8 antibodies were additive to those of anti-Vegf antibodies or cytotoxic chemotherapy. Thus, Bv8 modulates mobilization of CD11b+Gr1+ cells from the bone marrow during tumour development and also promotes angiogenesis locally.

SummaryMetastasis, which commonly uses lymphatics, accounts for much of the mortality associated with cancer. The vascular endothelial growth factor (VEGF)-C coreceptor, neuropilin-2 (Nrp2), modulates but is not necessary for developmental lymphangiogenesis, and its significance for metastasis is unknown. An antibody to Nrp2 that blocks VEGFC binding disrupts VEGFC-induced lymphatic endothelial cell migration, but not proliferation, in part independently of VEGF receptor activation. It does not affect established lymphatics in normal adult mice but reduces tumoral lymphangiogenesis and, importantly, functional lymphatics associated with tumors. It also reduces metastasis to sentinel lymph nodes and distant organs, apparently by delaying the departure of tumor cells from the primary tumor. Our results demonstrate that Nrp2, which was originally identified as an axon-guidance receptor, is an attractive target for modulating metastasis.

VEGF-A is important in tumor angiogenesis, and a humanized anti-VEGF-A monoclonal antibody (bevacizumab) has been approved by the FDA as a treatment for metastatic colorectal and nonsquamous, non-small-cell lung cancer in combination with chemotherapy. However, contributions of both tumor- and stromal-cell derived VEGF-A to vascularization of human tumors grown in immunodeficient mice hindered direct comparison between the pharmacological effects of anti-VEGF antibodies with different abilities to block host VEGF. Therefore, by gene replacement technology, we engineered mice to express a humanized form of VEGF-A (hum-X VEGF) that is recognized by many anti-VEGF antibodies and has biochemical and biological properties comparable with WT mouse and human VEGF-A. The hum-X VEGF mouse model was then used to compare the activity and safety of a panel of VEGF Mabs with different affinities for VEGF-A. Although in vitro studies clearly showed a correlation between binding affinity and potency at blocking endothelial cell proliferation stimulated by VEGF, in vivo experiments failed to document any consistent correlation between antibody affinity and the ability to inhibit tumor growth and angiogenesis in most animal models. However, higher-affinity antibodies were more likely to result in glomerulosclerosis during long-term treatment.

Introduction . Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin lymphoma (NHL). Although more than half of patients are cured with standard immunochemotherapy (R-CHOP) in first-line therapy, the disease relapses or is refractory to R-CHOP in ~40% of cases, with limited options for second-line treatment. Molecular characteristics, including Cell-of-Origin (COO), BCL2 expression and concomitant BCL2/MYC expression, contribute to differences in outcome for DLBCL patients (Alizadeh, Nature 2000, Iqbal Clin Cancer Res. 2011, Johnson JCO. 2012). Understanding these molecular risk factors is potentially of value to guide treatment decisions and optimize therapy. Here, we used assays validated for formalin-fixed, paraffin-embedded (FFPE) specimens to retrospectively assess the prevalence and prognostic value of BCL2 and MYC in patients from MAIN, a Phase III trial that evaluated bevacizumab plus R-CHOP in frontline, CD20-positive DLBCL (NCT00486759). This analysis will help assess markers relevant for risk assessment and may guide use of new investigational agents in DLBCL. Methods . Tissue microarrays (TMAs) from FFPE tumor samples were evaluated using immunohistochemistry (IHC) for BCL2 (clone 124 DAKO), and MYC (clone Y69 Epitomics). FFPE cell pellets from 26 NHL cell lines were also stained as above. BCL2 staining was scored on a 0-3 intensity scale; the BCL2 cutoff was determined by the expression level that conferred sensitivity ( Results . Baseline tissue samples were available from 230/787 (29%) patients from MAIN, with baseline characteristics and survival similar to the overall ITT population. TMAs were available for IHC evaluation in 184/230 (80%) samples, 88/184 (48%) of which were BCL2 positive. BCL2-positivity rates in various sub-sets were: 58% of IPI high, poor prognostic group vs. 41% of IPI low, good prognostic group, and 64% of ABC vs. 40% of GCB samples (Figure 1). BCL2 expression appeared to associate with adverse PFS in the GCB subtype (HR adjusted for IPI, 3.89; 95% CI: 1.30-11.68, Figure 2a) but not in the ABC subtype (HR adjusted for IPI: 0.81; 95% CI: 0.3-2.2, Figure 2b). BCL2 mRNA expression or BCL2 gene rearrangements by FISH showed no association with PFS. Thirty-two of 174 (18%) samples evaluated for MYC and BCL2 by IHC were DP (95% CI: 13%-25%). PFS was similar in non-DP and DP group (HR adjusted by IPI, 0.77; 95% CI: 0.40-1.48), but the DP group appeared to have inferior OS (HR adjusted by IPI, 0.45; 95% CI: 0.22-0.93). These data should be interpreted cautiously due to the small number of PFS/OS events. BCL2 IHC, BCL2 rearrangements and MYC IHC data were available for 40 ABC and 59 GCB samples. DP by IHC was observed in 10/40 (25%) ABC subtype and 10/59 (17%) GCB subtype samples. BCL2 translocations were observed in 6/40 (15%) of ABC, vs. 19/59 (32%) of GCB samples. Conclusions . Using validated assays developed for FFPE tissue testing, we determined the prevalence and prognostic value of BCL2 in a frontline DLBCL population enrolled in a clinical trial. BCL2 expression appeared to be higher in the poor prognostic groups (high IPI and ABC), and appeared to be an independent prognostic factor in the GCB subtype. BCL2 expression, DP and COO may identify patients with DLBCL who could benefit from BCL2 inhibition; the assays employed here are currently in use to evaluate BCL2 as a predictive biomarker for the BCL2 inhibitor venetoclax in lymphoma trials. Figure 2. Figure 2. Disclosures Punnoose: Genentech, Inc.: Employment. Off Label Use: This abstract reports on biomarker analyses using samples taken from previously untreated patients with DLBCL who received bevacizumab in combination with R-CHOP in the MAIN study. Peale:Roche: Equity Ownership; Genentech, Inc.: Employment. Lei:Roche: Employment. Sandmann:F. Hoffmann-La Roche AG: Employment, Equity Ownership. Bourgon:Roche: Equity Ownership; Genentech, Inc.: Employment. Szafer-Glusman:Genentech, Inc.: Employment. Do:Genentech, Inc.: Employment. Salles:Celgene Corporation; Roche: Speakers Bureau; Celgene Corporation; Roche and Gilead Sciences: Research Funding; Calistoga Pharmaceuticals, Inc.; Celgene Corporation; Genentech, Inc.; Janssen Pharmaceutica Products, L.P.; Roche: Consultancy. Seymour:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Speakers Bureau; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Infinity: Honoraria, Membership on an entity's Board of Directors or advisory committees; Phebra: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding, Speakers Bureau; Genentech, Inc.: Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Trneny:Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Munoz:Roche: Employment, Equity Ownership. Mundt:Roche: Employment.

Background MEHD is a novel dual-action humanized IgG1 antibody that blocks ligand binding to EGFR and HER3, inhibiting all major ligand-dependent HER complex signaling. Preclinical and Phase 1a clinical data suggested ligand-driven HER3 signaling as a promising target for therapy in a subset of patients with SCCHN. Results from the MEHGAN study showed comparable objective response rates and PFS for MEHD and Cet (Fayette et al, ESMO 2014). Here we report the results of comprehensive and comparative biomarker analyses from that study. Methods Archival and fresh (as available) tumor tissues were evaluated to characterize the biology of anti-HER therapy in SCCHN, and to identify potential predictive biomarkers for improved outcomes with MEHD compared to Cet, with particular attention to the HER3 ligand NRG1. NRG1 and ERBB3 RNA expression was measured by both ISH (data analysis are ongoing) and qRT-PCR. Additionally, extensive gene expression analyses and HPV detection were performed by qRT-PCR. Results Of 121 randomized patients in MEHGAN, 107 had archival tissues with sufficient tumor content and quality for biomarker analyses. Key findings include: 1) Most patients with CT RECIST responses on either treatment arm had higher (≥ median) tumor expression levels of NRG1 as measured by qRT-PCR 2) EGFR ligands such as amphiregulin were co-expressed with NRG1, consistent with preclinical analysis in an independent panel of SCCHN tumor samples (Genentech data on file). 3) 24 HPV (+) patients (20%) were identified, consistent with published prevalence reports. 4) Higher EGFR and HER3 ligand expression was observed in HPV (-) samples relative to HPV (+) samples and, moreover, no responses were seen in HPV (+) patients. These results are consistent with prior correlative ligand observations and may point to differential roles for HER signaling biology in HPV (-) versus HPV (+) SCCHN. Conclusions NRG1 expression did not predict enhanced responsiveness to MEHD versus Cet or, conversely, resistance to Cet. NRG1 and EGFR ligands appear to have similar expression patterns in SCCHN. Higher levels of NRG1 and EGFR ligands were associated with greater activity for both MEHD and Cet, and were consistently observed in HPV (-) SCCHN versus HPV (+) SCCHN. These data suggest distinct HER signaling biology in these 2 patient groups and warrant further evaluation to potentially inform treatment approaches in SCCHN. * We would like acknowledge and thank all of the MEHGAN study investigators and patients. Citation Format: Elicia Penuel, Amy V. Kapp, An Do, Rachel Tam, Teiko Sumiyoshi, Chaitra Marathe, Susan Sa, Franklin Peale, Mark Lackner, Scott Holden, Tanguy Seiwert, Andrea Pirzkall. Biomarker evaluation in a randomized phase 2 study of MEHD7945A (MEHD) versus cetuximab (Cet) in ≥2 line recurrent/metastatic (R/M) squamous cell carcinomas of the head and neck (SCCHN) [MEHGAN]. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1553. doi:10.1158/1538-7445.AM2015-1553

SummaryThe triglycerides in chylomicrons are hydrolyzed by lipoprotein lipase (LpL) along the luminal surface of the capillaries. However, the endothelial cell molecule that facilitates chylomicron processing by LpL has not yet been defined. Here, we show that glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) plays a critical role in the lipolytic processing of chylomicrons. Gpihbp1-deficient mice exhibit a striking accumulation of chylomicrons in the plasma, even on a low-fat diet, resulting in milky plasma and plasma triglyceride levels as high as 5000 mg/dl. Normally, Gpihbp1 is expressed highly in heart and adipose tissue, the same tissues that express high levels of LpL. In these tissues, GPIHBP1 is located on the luminal face of the capillary endothelium. Expression of GPIHBP1 in cultured cells confers the ability to bind both LpL and chylomicrons. These studies strongly suggest that GPIHBP1 is an important platform for the LpL-mediated processing of chylomicrons in capillaries.

Purpose To quantify spontaneous and therapeutic arteriogenesis in vivo in a murine model of peripheral arterial disease using magnetic resonance angiography. Materials and Methods Male, 8–12-week-old, C57/BL6 mice underwent femoral artery ligation; 21 days later, 2 mg/kg recombinant murine VEGF165, formulated for slow release, was injected into the ipsilateral gastrocnemius. The spontaneous (following ligation) and therapeutic (following vascular endothelial growth factor (VEGF)) formation of collateral vessels was quantified using 3D magnetic resonance angiography on a small-bore 4.7T system. Therapeutically induced angiogenesis and blood flow were quantified using an in situ anti-platelet endothelial cell adhesion molecule (PECAM) 1 radioimmunoassay and radiolabeled microsphere deposition, respectively. Results Spontaneous arteriogenesis was visible in all animals five days after ligation. VEGF treatment doubled the arteriogenic response five days after treatment compared to vehicle (cross-sectional area of vessels: 0.96 vs. 0.46 mm2, P < 0.01). VEGF also induced angiogenesis (PECAM1 levels 191% of vehicle, P < 0.05) and increased blood flow specific to the injection site (57 vs. 7 mL/minute/100 g, P < 0.05). Conclusion The presented methodology allowed in vivo quantification of spontaneous arteriogenesis in a murine model of peripheral arterial disease and demonstrated that therapeutic enlargement of collateral vessels is possible with VEGF. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.

Tissue microarrays enable the rapid histological localization of gene expression in hundreds of archival samples by in situ hybridization. However, the scoring of tissue microarray data may be influenced by intra- and inter-observer variations, and categorizing continuous variables risks discarding potentially meaningful information. Quantitation imposes a greater degree of objectivity, is more reproducible than subjective discriminations, and facilitates the communication and clarity of definitions. Phosphorimaging has been successfully used to quantitate the hybridization signal intensity from arrayed tissues. The process is rapid and has a wide dynamic range, surpassing the densitometric analysis of autoradiograms. This paper presents a detailed method for quantitative isotopic in situ hybridization on formalin-fixed paraffin-embedded tissue microarrays. In addition, the method includes a protocol for the development of synthetic agarose cores to control for the specificity and sensitivity of hybridization.

SummaryNeuropilin-1 (NRP1) guides the development of the nervous and vascular systems. Binding to either semaphorins or VEGF, NRP1 acts with plexins to regulate neuronal guidance, or with VEGFR2 to mediate vascular development. We have generated two monoclonal antibodies that bind to the Sema- and VEGF-binding domains of NRP1, respectively. Both antibodies reduce angiogenesis and vascular remodeling, while having little effect on other VEGFR2-mediated events. Importantly, anti-NRP1 antibodies have an additive effect with anti-VEGF therapy in reducing tumor growth. Vessels from tumors treated with anti-VEGF show a close association with pericytes, while tumors treated with both anti-NRP1 and anti-VEGF lack this organization. We propose that blocking NRP1 function inhibits vascular remodeling, rendering vessels more susceptible to anti-VEGF therapy.

To fully assess the role of VEGF-A in tumor angiogenesis, antibodies that can block all sources of vascular endothelial growth factor (VEGF) are desired. Selectively targeting tumor-derived VEGF overlooks the contribution of host stromal VEGF. Other strategies, such as targeting VEGF receptors directly or using receptor decoys, result in inhibiting not only VEGF-A but also VEGF homologues (e.g. placental growth factor, VEGF-B, and VEGF-C), which may play a role in angiogenesis. Here we report the identification of novel anti-VEGF antibodies, B20 and G6, from synthetic antibody phage libraries, which block both human and murine VEGF action in vitro. Their affinity-improved variants completely inhibit three human tumor xenografts in mice of skeletal muscle, colorectal, and pancreatic origins (A673, HM-7, and HPAC). Avastin, which only inhibits the tumor-derived human VEGF, is approximately 90% effective at inhibiting HM-7 and A673 growth but is50% effective at inhibiting HPAC growth. Indeed, HPAC tumors contain more host stroma invasion and stroma-derived VEGF than other tumors. Thus, the functional contribution of stromal VEGF varies greatly among tumors, and systemic blockade of both tumor and stroma-derived VEGF is sufficient for inhibiting the growth of tumor xenografts.

Bv8 and endocrine-gland-derived VEGF (EG-VEGF), or prokineticins, are two highly related, secreted proteins that we previously described as selective angiogenic mitogens. Here we describe the expression and functional characterization of Bv8 in peripheral blood cells, notably monocytes, neutrophils, and dendritic cells, and in the bone marrow. In human and mouse, the two Bv8 G protein-coupled receptors are expressed in hematopoietic stem cells and specific mature blood cells, including lymphocytes. Bv8 is highly expressed by neutrophils at sites of inflammation and can stimulate migration of monocytes, in a pertussis toxin-sensitive manner. Bv8, or EG-VEGF that shares the same receptors, increased numbers of colony-forming units granulocytic and monocytic in cultures of human or mouse hematopoietic stem cells. Systemic in vivo exposure to Bv8 or EG-VEGF resulted in significant increases in total leukocyte, neutrophil, and monocyte counts. Additionally, adenovirus (Av)Bv8 or AvEG-VEGF delivered just before 5-fluorouracil injury promoted the survival of hematopoietic cells and enhanced progenitor mobilization. In conclusion, Bv8 can promote survival and differentiation of the granulocytic and monocytic lineages. Bv8 potentially modulates growth, survival, and function of cells of the innate and adaptive immune systems, possibly through autocrine or paracrine signaling mechanisms.

Angiogenesis is essential for tumor growth and metastasis. A new human angiogenic mitogen, endocrine gland-derived vascular endothelial growth factor (EG-VEGF), has been recently identified; its expression pattern is restricted to endocrine glands, with the highest expression in testis. We used in situ hybridization and newly generated monoclonal antibodies to investigate the expression of EG-VEGF in normal human prenatal and adult testis and in 48 human testicular tumors of different subtypes. We found that EG-VEGF was expressed from 14 wk until birth in human fetal testis. In the adult testis, EG-VEGF was strongly expressed only in Leydig cells. In testicular tumors, EG-VEGF was expressed specifically in Leydig cell tumors, whereas germ cell-derived neoplasms, including carcinoma in situ, seminoma, and nonseminomatous germ cell tumors, were negative for this antigen. In contrast, VEGF, another powerful angiogenic factor, was expressed in seminoma, but very weakly in Leydig cell tumors. Interestingly, we found that Leydig cell tumors presented vessel surface density 3.2-fold higher than seminoma. These findings argue that human EG-VEGF may play a role in angiogenesis both during the early endocrine development of testis and in the adult testis as well as in Leydig cell tumor growth.

Aims: To measure vascular endothelial growth factor (VEGF-A) mRNA in a large, diverse cohort of tumours and to investigate whether VEGF-A expression is associated with markers of hypoxia, including hypoxia inducible factor 1α (HIF-1α) and carbonic anhydrase IX (CA9). Methods: The expression of VEGF-A and CA9 was assessed in 5067 fresh frozen human tissue samples and 238 cell lines by DNA microarray analysis. In addition, tissue microarrays were constructed from 388 malignancies to investigate the expression of VEGF-A and HIF-1α by in situ hybridisation and immunohistochemistry, respectively. Results: VEGF-A was significantly upregulated in primary malignancies of the breast, cervix, colon and rectum, oesophagus, head and neck, kidney, ovary, skin, urinary system, and white blood cells by DNA microarray analysis. However, VEGF-A expression only correlated with CA9 expression in renal tissues. In the tissue microarrays, HIF-1α positive cores showed a significant increase in VEGF-A expression in lung, ovary, soft tissue, and thyroid malignancies. Conclusions: The expression of VEGF-A is upregulated in a large proportion of human malignancies, and may be associated with markers of hypoxia. VEGF-A expression can be induced in the absence of hypoxia and hypoxia does not always provoke VEGF-A upregulation in tumours.

DNA microarrays were used to measure the time course of gene expression during skeletal muscle damage and regeneration in mice following femoral artery ligation (FAL). We found 1,289 known sequences were differentially expressed between the FAL and control groups. Gene expression peaked on day 3, and the functional cluster “inflammation” contained the greatest number of genes. Muscle function was depressed for 3 days postligation, but returned to normal by day 7. Decreased muscle function was accompanied by reduced expression of genes involved in mitochondrial energy production, muscle contraction, and calcium handling. The induction of MyoD on day 1 denoted the beginning of muscle regeneration and was followed by the reemergence of the embryonic forms of muscle contractile proteins, which peaked at day 7. Transcriptional analysis indicated that the ischemic skeletal muscle may transition through a functional adaptation stage with recovery of contractile force prior to full regeneration. Several members of the insulin-like growth factor axis were coordinately induced in a time frame consistent with their playing a role in the regenerative process.

We conducted an expression analysis of prostate stem cell antigen (PSCA)in normal urogenital tissues, benign prostatic hyperplasia (n = 21), prostatic intraepithelial neoplasia (n = 33), and primary (n = 137) and metastatic (n = 42) prostate adenocarcinoma, using isotopic in situ hybridization on tissue microarrays. In normal prostate, we observe PSCA expression in the terminally differentiated, secretory epithelium; strong expression was also seen in normal urothelium. Forty-eight percent of primary and 64% of metastatic prostatic adenocarcinomas expressed PSCA RNA. Our studies did not confirm a positive correlation between level of PSCA RNA expression and high Gleason grade. We characterized monoclonal anti-PSCA antibodies that recognize PSCA expressed on the surface of live cells, are efficiently internalized after antigen recognition, and kill tumor cells in vitro in an antigen-specific fashion upon conjugation with maytansinoid. Unconjugated anti-PSCA antibodies demonstrated efficacy against PSCA-positive tumors by delaying progressive tumor growth in vivo. Maytansinoid-conjugated antibodies caused complete regression of established tumors in a large proportion of animals. Our results strongly suggest that maytansinoid-conjugated anti-PSCA monoclonal antibodies should be evaluated as a therapeutic modality for patients with advanced prostate cancer.

A mouse model of non-necrotic vascular deficiency in the adult heart was studied using cine-magnetic resonance imaging (MRI) and other techniques. The mice lacked cardiomyocyte-derived vascular endothelial growth factor (VEGF) following a targeted knockout in the ventricular cardiomyocytes. Quantitative endothelial labeling showed that the capillary density was significantly reduced in the hearts of knockout mice. Gene expression patterns suggested that they were hypoxic. Semiautomated MR image analysis was employed to obtain both global and regional measurements of left ventricular function at 10 or more time points through the cardiac cycle. MRI measurements showed a marked reduction in ejection fraction both at rest and under low- and high-dose dobutamine stress. Regional wall thickness, thickening, and displacement were all attenuated in the knockout mice. A prolonged high-dose dobutamine challenge was monitored by MRI. A maximal response was sustained for 90 minutes, suggesting that it did not depend on endogenous glycogen stores.

The analysis of gene expression in specific tissues and physiological processes has evolved over the last 20 years from the painstaking identification of selected genes to the relatively efficient and open-ended surveying of potentially all genes expressed in a tissue. Current art for gene discovery includes the use of large-scale arrays of cDNA sequences or oligonucleotides, and molecular ‘tagging’ techniques such as GeneCalling and SAGE. Common to each of these techniques is a reliance on the increasingly comprehensive databases of human and mouse EST and full-length gene sequences. Early efforts to characterize candidate genes were limited by their narrow scope, while current efforts are confounded by the enormous volume of data returned. Sophisticated software tools are an integral part of the analysis, helping to organize information into coherent groups with temporal or functional similarity. These techniques, in conjunction with the continued analysis of human genetic syndromes, transgenic, and knockout mice, have driven genetic analysis of angiogenesis and vascular development from describing which individual genes are involved to defining the outlines of regulatory networks. Copyright © 2001 John Wiley & Sons, Ltd.

In the present study we have used a novel, comprehensive mRNA profiling technique (GeneCalling) for determining differential gene expression profiles of human endothelial cells undergoing differentiation into tubelike structures. One hundred fifteen cDNA fragments were identified and shown to represent 90 distinct genes. Although some of the genes identified have previously been implicated in angiogenesis, potential roles for many new genes, including OX-40, white protein homolog, KIAA0188, a homolog of angiopoietin-2, ADAMTS-4 (aggrecanase-1), and stanniocalcin were revealed. Support for the biological significance was confirmed by the abrogation of the changes in the expression of angiogenesis inhibitors and in situ hybridization studies. This study has significantly extends the molecular fingerprint of the changes in gene expression that occur during endothelial differentiation and provides new insights into the potential role of a number of new molecules in angiogenesis.

Ionic currents are critical for the functioning of the inner ear auditory sensory epithelium. We set out to identify and molecularly clone the genes encoding the channels responsible for several currents in the chick basilar papilla. Here we describe an inward-rectifying K+ channel, cKir2.3, present in both hair cells and support cells in the apical end of the chick basilar papilla. The biophysical properties of the human ortholog, hKir2.3, are similar to those of an inward-rectifying channel found in the apical end of the chick basilar papilla, suggesting that this channel may contribute to the corresponding current. Additionally, we describe two new members of the Kv6 subfamily of putative regulatory voltage-gated K+ channels, cKv6.2 and cKv6.3. Both are expressed in hair cells in the apical end of the chick basilar papilla; cKv6.2 is also strongly expressed in support cells and in the brain.

Quantifying oxygenation in viable tumor remains a major obstacle toward a better understanding of the tumor microenvironment and improving treatment strategies. Current techniques are often complicated by tumor heterogeneity. Herein, a novel in vivo approach that combines 19 F magnetic resonance imaging ( 19 F-MRI)R 1 mapping with diffusionbased multispectral (MS) analysis is introduced. This approach restricts the partial pressure of oxygen (pO 2 ) measurements to viable tumor, the tissue of therapeutic interest. The technique exhibited sufficient sensitivity to detect a breathing gas challenge in a xenograft tumor model, and the hypoxic region measured by MS 19 F-MRI was strongly correlated with histologic estimates of hypoxia. This approach was then applied to address the effects of antivascular agents on tumor oxygenation, which is a research question that is still under debate. The technique was used to monitor longitudinal pO 2 changes in response to an antibody to vascular endothelial growth factor (B20.4.1.1) and a selective dual phosphoinositide 3-kinase/mammalian target of rapamycin inhibitor (GDC-0980). GDC-0980 reduced viable tumor pO 2 during a 3-day treatment period, and a significant reduction was also produced by B20.4.1.1. Overall, this method provides an unprecedented view of viable tumor pO 2 and contributes to a greater understanding of the effects of antivascular therapies on the tumor's microenvironment.

2503 Background: GDCE0917 is a small molecule that triggers tumor cell apoptosis by selectively antagonizing IAP proteins. Preclinical studies demonstrated antitumor efficacy of GDC-0917 alone or in combination with chemotherapeutic agents. Methods: Oral GDC-0917 was given on Day (d) 1 followed by 2d off and a 2-week (w) on/ 1w off treatment (tx) schedule (21d cycle) starting d4. A modified continual reassessment method was used for dose escalation. Dose-limiting toxicity (DLT, assessed d1-24), PK, adverse events (AEs), pharmacodynamics (PD), and clinical activity were evaluated. Results: 42 pts of age 36-86 (median 60.5) were enrolled in 11 cohorts (5-600 mg) and received 1-15 cycles (median 2) of GDC-0917. One DLT, Grade (G) 3 fatigue, was observed at 450 mg. The maximum tolerated dose was not determined although plasma concentrations of preclinically defined IC90 were reached. The most frequent AEs were diarrhea, fatigue and nausea (26.2% each), vomiting (23.8%), and constipation (19%). The most frequent AEs reported as tx-related were mostly G1-2 and included fatigue and nausea (21.4% each), vomiting (14.3%), rash (11.9%) and pruritus (9.5%). AEs reported as tx-related that were ≥ G3 in > 1 pt were elevated AST and ALT (2 pts, at 450 and 600 mg). AEs reported as tx-related that resulted in tx discontinuation were G3 fatigue, G2 QTc prolongation, G2 drug hypersensitivity, G2 pneumonitis (1 pt each), and G3 pruritus/G2 rash (same pt). GDC-0917 peak concentrations were observed 2-3h post dosing. Exposure was dose-proportional with a mean plasma elimination t1/2of 4-8h and no apparent accumulation at steady state. Rapid down-modulation of cIAP1 was observed in PBMCs at all dose levels. Evaluation of tumor biopsies demonstrated decreases in cIAP1 (2 pts total, at 40 and 200 mg) and increases in activated caspase-3 and cPARP (1 pt at 200 mg). Two pts (4.8%) had a complete response (both unconfirmed, ovarian Ca and MALT lymphoma [PET]); 4 pts (9.5%) had stable disease for ≥ 3 months. Conclusions: GDC-0917 had a favorable safety, PK and PD profile in pts with advanced malignancies. These encouraging results support further clinical evaluation of this agent. Clinical trial information: NCT01226277.

A hallmark feature of cancer is the ability to evade cell death signals induced by stress response cues mediated, in part, by the the Bcl-2 family of pro-apoptotic and pro-survival proteins. ABT-199 is a potent BH3-only mimetic that selectively antagonizes the pro-survival function of Bcl-2. The work presented describes the efficacy of ABT-199 as a single agent and in combination with bortezomib in preclinical models of Multiple Myeloma (MM). Expression of Bcl-2 protein was detected in 95% of MM cell lines (n=21) evaluated and ABT-199 reduced cell viability in a sub-set of these lines (7/21) with EC50 values less than 0.5 μM. Expression of Bcl-xL and Mcl-1 at the mRNA and protein levels were also evaluated to determine predictors of drug sensitivity and resistance to ABT-199. MM lines that expressed higher levels of Bcl-2 relative to Bcl-xL and Mcl-1 were the most sensitive to ABT-199 treatment while those that were less sensitive expressed higher levels of Mcl-1 or Bcl-xL. Other predictors of sensitivity to ABT-199 included higher levels of Bcl-2/Bim complexes and t(11;14) status. Ex vivo, 75% of the MM bone marrow biopsies and aspirates (n=27) had high Bcl-2 levels whereas 50% had high Bcl-xL expression, demonstrating that a subset of patient samples (33%) have a favorable biomarker profile (Bcl-2-high/Bcl-xL-low) that may be predictive of ABT-199 activity. Efficacy of ABT-199 as a single agent and in combination with bortezomib was evaluated in vivo in MM xenograft models that expressed Bcl-2 (OPM-2, KMS-11, RPMI-8226, H929 and MM.1s). Bortezomib treatment alone at maximum tolerated doses resulted in tumor regressions or stasis in all xenograft models tested. ABT-199 at maximum tolerated doses was efficacious as a single agent in xenograft models that expressed higher protein levels of Bcl-2 but relatively lower levels of Bcl-xL. The combination of ABT-199 with bortezomib increased overall response rates, durability of anti-tumor activity and levels of apoptotic markers such as cleaved caspase 3 and PARP when compared to bortezomib alone even in MM xenograft models that also express relatively high levels of Mcl-1. Treatment with bortezomib in vivo increased levels of Noxa; a pro-apoptotic BH3-only protein that selectively antagonizes Mcl-1. Therefore, greater efficacy may be achieved when ABT-199 is combined with bortezomib due to inhibition of Bcl-2 by ABT-199 and neutralization of Mcl-1 by Noxa in tumors that express both pro-survival proteins. Our preclinical data supports the evaluation of ABT-199 as a single agent and in combination with bortezomib in MM patients in which relative expression of the Bcl-2 pro-survival proteins may serve as predictive biomarkers of drug activity. Citation Format: Deepak Sampath, Elizabeth Punnoose, Erwin Boghaert, Lisa Belmont, Franklin Peale, Nguyen Tan, Jun Chen, Walter Darbonne, Peng Yue, Jason Oeh, Leslie Lee, Wayne J. Fairbrother, Andrew J. Souers, Steven W. Elmore, Joel D. Leverson. Expression of Bcl-2 pro-survival family proteins predicts pharmacological responses to ABT-199, a novel and selective Bcl-2 antagonist, in multiple myeloma models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4607. doi:10.1158/1538-7445.AM2013-4607

Abstract 5028 Multiple myeloma (MM) is a hematological malignancy of the bone marrow caused by the dysregulated proliferation of monoclonal antibody producing plasma cells. A hallmark feature of cancer is the ability to evade cell death signals induced by stress response cues. The Bcl-2 family of proteins regulates the intrinsic apoptosis pathways and consists of pro-apoptotic (Bax, Bak, Bad, Bim, Noxa, Puma) and pro-survival (Bcl-2, Bcl-xL, Mcl-1); the balance of which dictates the life or death status of MM tumor cells. Thus, there is a strong rationale to target members of the Bcl-2 proteins for the treatment of MM. ABT-199 is a potent BH3-only mimetic that selectively antagonizes Bcl-2 and is currently in phase I clinical trials for the treatment of hematological malignancies. Therefore, we evaluated the efficacy of ABT-199 as a single agent and in combination with standard of care drugs such as Velcade (bortezomib) in preclinical models of MM. A panel of 21 human MM cell lines was evaluated in vitro for to sensitivity to ABT-199. ABT-199 potently inhibited cell viability in a sub-set of MM cell lines (7/21) with EC50 values less than 1 μM. Expression of Bcl-2, Bcl-xL, Mcl-1, Bim and other Bcl-2 family proteins were evaluated by protein and mRNA. Cell line modeling identified thresholds for expression of Bcl-2, Bcl-xL and Mcl-1 that best predicted sensitivity and resistance to ABT-199 and the dual Bcl-2/Bcl-xL antagonist, navitoclax. Consistent with the target inhibition profile of these drugs, we found that MM lines that were Bcl-2high/Bcl-xLlow/Mcl-1low are the most sensitive to ABT-199 treatment. Whereas cell lines that are Bcl-xLhigh remain sensitive to navitoclax but not ABT-199. MM cell lines that are Mcl-1high are less sensitive to both ABT-199 and navitoclax, suggesting that Mcl-1 is a resistance factor to both drugs. Utilizing a novel Mesoscale Discovery based immunoassay we determined that levels of Bcl-2/Bim complexes also correlated with sensitivity of ABT-199 in the MM cell lines tested. In addition, the t(11;14) status in these cell lines associated with sensitivity to ABT-199. The clinical relevance of the Bcl-2 pro-survival expression pattern in MM cell lines, was determined by a collection of bone marrow biopsies and aspirates (n=27) from MM patients by immunohistochemistry for prevalence of Bcl-2 and Bcl-xL. Similar to our in vitro observations, the majority (75%) of the MM bone marrow biopsies and aspirates had high Bcl-2 levels whereas 50% had high Bcl-xL expression. Therefore, a subset of patient samples (33%) were identified with a favorable biomarker profile (Bcl-2high/Bcl-xLlow) that may predict ABT-199 single agent activity. ABT-199 synergized with bortezomib in decreasing cell viability in the majority of MM cell lines tested in vitro based on the Bliss model of independence analyses (Bliss score range = 10 to 40). However the window of combination activity was reduced due to high degree of sensitivity to bortezomib alone. Therefore, the combination efficacy of ABT-199 and bortezomib was further evaluated in vivo in MM xenograft models that expressed high levels of Bcl-2 protein (OPM-2, KMS-11, RPMI-8226, H929 and MM. 1s). Bortezomib treatment alone at a maximum tolerated dose resulted in tumor regressions or stasis in all xenograft models tested. ABT-199 at a maximum tolerated dose was moderately efficacious (defined by tumor growth delay) as a single agent in xenograft models that expressed high protein levels of Bcl-2 but relatively lower levels of Bcl-xL. However, the combination of ABT-199 with bortezomib significantly increased the overall response rate and durability of anti-tumor activity when compared to bortezomib, resulting in increased cell death in vivo. Treatment with bortezomib increased levels of the pro-apoptotic BH3-only protein, Noxa, in MM xenograft models that expressed high levels of Mcl-1. Given that the induction of Noxa by bortezomib results in neutralization of Mcl-1 pro-survival activity in MM models [Gomez-Bougie et al; Cancer Res. 67:5418–24 (2007)], greater efficacy may be achieved when Bcl-2 is antagonized by ABT-199 thereby inhibiting pro-survival activity occurring through either Bcl-2 or Mcl-1 and increasing cell death. Thus, our preclinical data support the clinical evaluation of ABT-199 in combination with bortezomib in MM patients in which relative expression of the Bcl-2 pro-survival proteins may serve as predictive biomarkers of drug activity. Disclosures: Sampath: Genentech: Employment, Equity Ownership. Punnoose:Genentech: Employment, Equity Ownership. Boghaert:Abbott Pharmaceuticals: Employment, Equity Ownership. Belmont:Genentech: Employment, Equity Ownership. Chen:Abbott Pharmaceuticals: Employment, Equity Ownership. Peale:Genentech: Employment, Equity Ownership. Tan:Genentech: Employment, Equity Ownership. Darbonne:Genentech: Employment, Equity Ownership. Yue:Genentech: Employment, Equity Ownership. Oeh:Genentech: Employment, Equity Ownership. Lee:Genentech: Employment, Equity Ownership. Fairbrother:Genentech: Employment, Equity Ownership. Souers:Abbott Pharmaceuticals: Employment, Equity Ownership. Elmore:Abbott Pharmaceuticals: Employment, Equity Ownership. Leverson:Abbott Pharmaceuticals: Employment, Equity Ownership.

EGFL7 is a secreted protein expressed by proliferating endothelial cells in growing vessels during normal organ development. Though expression is generally restricted to a small subset of vessels in the adult, elevated expression has been observed under physiological conditions requiring new blood vessel growth, such as wound healing, pregnancy and tumor growth. EGFL7 facilitates new blood vessel formation by supporting endothelial cell adhesion and migration. In addition, EGFL7 can protect endothelial cells from stress-induced apoptosis, such as hypoxia or potentially growth factor withdrawal. A blocking antibody to EGFL7 (anti-EGFL7) has demonstrated increased survival benefits in preclinical models when combined with a blocking antibody to the pro-angiogenic growth factor VEGFA. Anti-EGFL7 is currently being investigated in Phase II clinical trials in NSCLC and mCRC in combination with bevacizumab and chemotherapy. We present here a comprehensive assessment of Egfl7 expression in a broad range of human solid tumors using in situ hybridization (BC n=150, CRC n=134, RCC n=8, LC n=62, LN mets predom. BC n=27, OV n=25) and quantitative PCR (BC n=92 primary, n=20 LN mets synchronous collection, n=12 distant matched metastasis sequential collection; CRC n=85 primary, n=9 distant matched metastasis sequential collection; NSCLC n=77 primary, n=3 distant matched metastasis sequential collection). Egfl7 is expressed in all tumor types interrogated. With the methods utilized in this study, expression appears to be limited to endothelial cells, with no appreciable tumor cell expression. This data is supported by co-expression analysis in preclinical and clinical samples, showing correlation with vascular markers (n=91 xenograft models CD31 r=0.85, p Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-312. doi:1538-7445.AM2012-LB-312

Neuropilin-1 (NRP1) is a multi-domain transmembrane receptor that is important for the development of the nervous and vascular systems and has been implicated in modulating various aspects of tumor biology. We have previously shown that an antibody directed against NRP1 inhibits tumor growth and reduces tumor angiogenesis, as a single agent and more potently in combination with anti-VEGF. Currently, anti-NRP1 is in evaluation in early clinical studies. Therefore, understanding the expression pattern of Nrp1 and its relevant ligands in human tumor samples is of critical importance. To this end, we first evaluated the binding of a number of putative ligands that have been suggested to interact with NRP1 in the literature, and furthermore to understand which of these are biochemically or functionally inhibited by our anti-NRP1. We found that members of the semaphorin and VEGF families, but not HGF bind to NRP1. However, only binding and function of specific ligands from the VEGF family are inhibited by anti-NRP1. Additionally, we evaluated the expression pattern of NRP1 in human tumor samples from a number of different tumor types, including breast, colorectal, lung, ovarian, pancreatic, prostate and renal cancer. NRP1 is broadly expressed in the vasculature of most cases of all these tumor types. Additionally, NRP1 is also variably expressed by tumor cells and other stromal elements in a more variable manner that is tumor type dependent. These results suggest that NRP1 is a potentially important therapeutic target in many different tumor types. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1292.

Reproducible, rapid measurement of estrogen receptor (ER) binding to DNA was accomplished in microtiter wells treated so that ER-DNA complexes or DNA bound in preference to free ER. Mixtures of 35S-labeled DNA and [3H]estrogen-charged ER ([3H]ER), incubated to equilibrium in microfuge tubes, were transferred to microtiter wells previously treated with histone followed by gelatin. After binding of the DNA or ER-DNA complex to the treated wells, free ER was removed by washing. Radioactivity retained in each well was measured by placing individual wells from snap-apart microtiter plates directly in scintillation fluid. Binding of DNA was saturable, and ER-DNA complex binding was complete within 2 h at 4 C. The use of 35S-labeled DNA and [3H]ER allowed stoichiometric determination of ER bound to DNA. The amount of ER specifically bound to a consensus estrogen-responsive element (ERE) containing the inverted repeat GGTCAgagTGACC was determined by comparing ER bound to plasmid containing or lacking the ERE. At saturating concentrations of ER, plasmids bearing one, two, and four EREs in tandem bound approximately one, two, and four dimeric ER molecules, respectively. Scatchard analysis of saturation binding data revealed a Kd of 0.15 nM for specific ER binding to a single ERE site. Thus, the assay detects ER retaining both DNA-binding and estrogen-binding functions. ER complexed with DNA in the well was also detected using a monoclonal antibody specific for the receptor. Simple modifications of this method would allow study of other DNA-protein interactions.

Lower assayed levels of heifer uterine estrogen receptor (ER) occur at physiologic ionic strength when ER is separated from [3H]estradiol by Dextran-coated charcoal treatments, or by gel filtration on Sephadex or polyacrylamide resins. The assayed level of charged ER in buffers containing 150–200 mM ionic strength is approximately one-half that of ER levels assayed in buffers either at 0–50 or 400–450 mM ionic strength. Treatment of ER with trypsin or molybdate eliminates this observed reduction. Evidence is presented that the decrease results from a preferential adsorption of ER to the assay resins at 150–200 mM ionic strength. This adsorption is likely to be mediated by a hydrophobic region of the ER, which is removed by trypsin cleavage.

Hepatocyte growth factor activator inhibitor-1 (HAI-1) is a membrane-associated Kunitz-type serine protease inhibitor that regulates cell surface and extracellular serine proteases involved in tissue remodeling and tumorigenesis, such as HGFA, matriptase, prostasin and hepsin. We generated HAI-1-deficient mice, which died in utero due to placental defects. The HAI-1−/− placental labyrinth exhibited a complete failure of vascularization and a compact morphology of the trophoblast layer. Immunofluorescent staining of collagen IV and laminin and electron microscopy analysis revealed that this aberrant labyrinth architecture was associated with disrupted basement membranes located at the interface of chorionic trophoblasts and allantoic mesoderm. Unlike the placental labyrinth, basement membranes and vasculogenesis were normal in embryo and yolk sac. Therefore, basement membrane defects appear to be the underlying cause for the greatly impaired vascularization and trophoblast branching in HAI-1−/− placentas. In wild-type placentas, the expression of matriptase and prostasin co-localized with their physiological inhibitor HAI-1 to the labyrinthine trophoblast cells in proximity to basement membranes. In HAI-1−/− placentas, both the localization and expression of the two proteases remained unchanged, implying uncontrolled proteolytic activities of the two enzymes. Our study demonstrates the important role of HAI-1 in maintaining the integrity of basement membrane most likely by regulating extracellular proteolytic activities during placental development.

Summary Robo4 is an endothelial cell-specific member of the Roundabout axon guidance receptor family. To identify Robo4 binding partners, we performed a protein-protein interaction screen with the Robo4 extracellular domain. We find that Robo4 specifically binds to UNC5B, a vascular Netrin receptor, revealing unexpected interactions between two endothelial guidance receptors. We show that Robo4 maintains vessel integrity by activating UNC5B, which inhibits signaling downstream of vascular endothelial growth factor (VEGF). Function-blocking monoclonal antibodies against Robo4 and UNC5B increase angiogenesis and disrupt vessel integrity. Soluble Robo4 protein inhibits VEGF-induced vessel permeability and rescues barrier defects in Robo4 −/− mice, but not in mice treated with anti-UNC5B. Thus, Robo4-UNC5B signaling maintains vascular integrity by counteracting VEGF signaling in endothelial cells, identifying a novel function of guidance receptor interactions in the vasculature.

Rapid purification of calf uterine estrogen receptor (ER) to near homogeneity has been accomplished by use of sequence-specific DNA affinity resin. Very high selectivity for the estrogen receptor is achieved through the use of DNA-Sepharose containing eight tandem copies of a consensus estrogen response element (ERE) DNA sequence. The highly purified ER prepared by this new scheme may be labeled economically with ligands of high specific activity. This purification scheme selects for intact receptors retaining function in both estrogen-binding and DNA-binding domains. Purified receptor has an electrophoretic mobility consistent with a molecular weight of 68,000, sediments as a 5S species on sucrose gradients, and reacts with antibody specific to the human estrogen receptor.

It has been shown previously that a short sequence from the 5' regulatory region of the Xenopus laevis vitellogenin gene A2, when appropriately placed, can confer estrogen responsiveness to another gene. Using the Xenopus sequence and similar sequences from the 5' regulatory regions of other estrogen-responsive genes, we derived a consensus sequence 38 nucleotides long. The sequence contains an inverted repeat (5' C-A-G-G-T-C-A-G-A-G-T-G-A-C-C-T-G 3') and an A/T-rich region. Plasmids carrying a single copy of the sequence bound 3-fold-more partially purified estrogen receptor (ER) than did control plasmids when assayed by gel filtration. Maximum specificity for ER binding occurs at 100-150 mM ionic strength and pH 7.5-8.0. Plasmids carrying multiple copies of the sequence bound correspondingly more ER. The dissociation constant for ER bound to the sequence is 0.5 nM. This value is lower by a factor of about 400 than the dissociation constant for ER bound to an equivalent length of plasmid DNA. Portions of the consensus sequence were evaluated for binding efficiency. Plasmids containing the inverted repeat alone bound ER, though less efficiently than did plasmids containing the entire sequence. The A/T-rich region alone was ineffective in binding ER. Linearization of the plasmid DNA did not enhance specific binding efficiency for ER. This model system represents an effective tool for characterization of ER binding to DNA sequences involved in the regulation of gene expression.

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