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The NEDD8-activating enzyme is upstream of the 20S proteasome in the ubiquitin/proteasome pathway and catalyzes the first step in the neddylation pathway. NEDD8 modification of cullins is required for ubiquitination of cullin-ring ligases that regulate degradation of a distinct subset of proteins. The more targeted impact of NEDD8-activating enzyme on protein degradation prompted us to study MLN4924, an investigational NEDD8-activating enzyme inhibitor, in preclinical multiple myeloma models. In vitro treatment with MLN4924 led to dose-dependent decrease of viability (EC50 = 25–150 nmol/L) in a panel of human multiple myeloma cell lines. MLN4924 was similarly active against a bortezomib-resistant ANBL-6 subline and its bortezomib-sensitive parental cells. MLN4924 had submicromolar activity (EC50 values + multiple myeloma patient cells and exhibited at least additive effect when combined with dexamethasone, doxorubicin, and bortezomib against MM.1S cells. The bortezomib-induced compensatory upregulation of transcripts for ubiquitin/proteasome was not observed with MLN4924 treatment, suggesting distinct functional roles of NEDD8-activating enzyme versus 20S proteasome. MLN4924 was well tolerated at doses up to 60 mg/kg 2× daily and significantly reduced tumor burden in both a subcutaneous and an orthotopic mouse model of multiple myeloma. These studies provide the framework for the clinical investigation of MLN4924 in multiple myeloma. Mol Cancer Ther; 11(4); 942–51. ©2012 AACR.

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Supplementary Fig. S5 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Fig. S4 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Fig. S2 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Data from Interactions of the Hdm2/p53 and Proteasome Pathways May Enhance the Antitumor Activity of Bortezomib

Supplementary Figure 2 - PDF file 50K, Accessory cells protect MM cells from WT-1 specific CTLs. U266 cells were co-cultured with WT-1 specific T cells in presence and absence of different accessory cells. MM cell viability was determined 24h after addition of T cells by CS-BLI (A). Granzyme B production in the supernatant was determined by ELISA (B). Significance of inhibition of MM cell survival in the presence of accessory cells was tested by unpaired two tailed student's t test. *= p

Members of the inhibitor of apoptosis protein (IAP) family play a role in mediating apoptosis. Studies suggest that these proteins may be a viable target in leukemia because they have been found to be variably expressed in acute leukemias and are associated with chemosensitivity, chemoresistance, disease progression, remission, and patient survival. Another promising therapeutic target, FLT3, is mutated in about one third of acute myelogenous leukemia (AML) patients; promising results have recently been achieved in clinical trials investigating the effects of the protein tyrosine kinase inhibitor PKC412 on AML patients harboring mutations in the FLT3 protein. Of growing concern, however, is the development of drug resistance resulting from the emergence of point mutations in targeted tyrosine kinases used for treatment of acute leukemia patients. One approach to overriding resistance is to combine structurally unrelated inhibitors and/or inhibitors of different signaling pathways. The proapoptotic IAP inhibitor, LBW242, was shown in proliferation studies done in vitro to enhance the killing of PKC412-sensitive and PKC412-resistant cell lines expressing mutant FLT3 when combined with either PKC412 or standard cytotoxic agents (doxorubicin and Ara-c). In addition, in an in vivo imaging assay using bioluminescence as a measure of tumor burden, a total of 12 male NCr-nude mice were treated for 10 days with p.o. administration of vehicle, LBW242 (50 mg/kg/day), PKC412 (40 mg/kg/day), or a combination of LBW242 and PKC412; the lowest tumor burden was observed in the drug combination group. Finally, the combination of LBW242 and PKC412 was sufficient to override stromal-mediated viability signaling conferring resistance to PKC412. [Mol Cancer Ther 2007;6(7):1951–61]

Supplementary Figure Legends from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Fig. S1 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Figure 1 - PDF file 53K, Antigen specific, HLA-restricted and dose-dependent recognition of the MM cell lines U266 and UM9, but not of accessory cells by CD8+ and CD4+ mHag-specific CTLs. The CD4+ (A) and CD8+ (B) CTLs were co-cultured with the luc+ MM cell lines UM9 and U266 in different effector to target ratios. The HLA- and mHag typing of these MM cell lines are indicated. MM cell survival was determined 24 h after addition of T cells by CS-BLI. Results represent the mean values of triplicate cultures (+/- SEM). Results are representative of 3 independent assays. In (C and D) CD4+ (C) and CD8+ (D) CTLs were co-cultured with accessory cells. Accessory cell survival was determined 24h after addition of T cells by FACS annexine V/ propidium iodide staining of CD4 and CD8 negative cells in the co-cultures. Results are depicted as % surviving cells, measured as relative number annexin V/propidium iodide negative cells, compared to no T cells control

Supplementary Figure 3 - PDF file 55K, RGDw reduces adhesion of MM cells to accessory cells. Adherent HS-5 en HUVEC accessory cells were incubated with RGDw or an irrelevant peptide for 1hour. After washing away the unbound peptide, UM9 (A) or U266 (B) cells were added and incubated overnight. Plates were reversely centrifuged to determine adhesion to accessory cells. Results represent the mean values of triplicate cultures (+/- SEM). Differences in adhesion were tested by unpaired two tailed student's t test. *= p

Supplementary Fig. S6 from Stromal-mediated protection of tyrosine kinase inhibitor-treated BCR-ABL-expressing leukemia cells

Supplementary Figure 5 - PDF file 41K, Bortezomib does not improve the CTL mediated lysis of Fas negative L363 cellsL3L3 reactive CD8+CTLs were incubated at the indicated effector to target ratios with luc-transduced L3L3 cells alone or in the presence of various dilutions of bortezomib. The CTL mediated and bortezomib mediated lysis of L3L3 cells was determined after 48 hours by BLI. Results are depicted as % surviving cells using the triplicate cultures without T cells and bortezomib as the 100% survival control

Supplementary Fig. S5 from Stromal-mediated protection of tyrosine kinase inhibitor-treated BCR-ABL-expressing leukemia cells

Supplementary Fig. S6 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Purpose: Cellular immunotherapy frequently fails to induce sustained remissions in patients with multiple myeloma, indicating the ability of multiple myeloma cells to evade cellular immunity. Toward a better understanding and effective therapeutic modulation of multiple myeloma immune evasion mechanisms, we here investigated the role of the tumor microenvironment in rendering multiple myeloma cells resistant to the cytotoxic machinery of T cells.Experimental Design: Using a compartment-specific, bioluminescence imaging-based assay system, we measured the lysis of luciferase-transduced multiple myeloma cells by CD4+ or CD8+ CTLs in the presence versus absence of adherent accessory cells of the bone marrow microenvironment. We simultaneously determined the level of CTL activation by measuring the granzyme B release in culture supernatants.Results: Bone marrow stromal cells from patients with multiple myeloma and healthy individuals, as well as vascular endothelial cells, significantly inhibited the lysis of multiple myeloma cells in a cell–cell contact-dependent manner and without substantial T-cell suppression, thus showing the induction of a cell adhesion-mediated immune resistance (CAM-IR) against CTL lysis. Further analyses revealed that adhesion to accessory cells downregulated Fas and upregulated the caspase-3 inhibitor survivin in multiple myeloma cells. Reconstitution of Fas expression with bortezomib enhanced the CTL-mediated lysis of multiple myeloma cells. Repressing survivin with the small-molecule YM155 synergized with CTLs and abrogated CAM-IR in vitro and in vivo.Conclusion: These results reveal the cell adhesion-mediated induction of apoptosis resistance as a novel immune escape mechanism and provide a rationale to improve the efficacy of cellular therapies by pharmacologic modulation of CAM-IR. Clin Cancer Res; 19(20); 5591–601. ©2013 AACR.

Supplementary Figure Legends - PDF file 73K, Legends for supplementary figures

Supplementary Fig. S1 from Stromal-mediated protection of tyrosine kinase inhibitor-treated BCR-ABL-expressing leukemia cells

Supplementary Fig. S4 from Stromal-mediated protection of tyrosine kinase inhibitor-treated BCR-ABL-expressing leukemia cells

Supplementary Figure 6 - PDF file 74K, Synergistic interaction of YM155 and CTLs. In A, the effect of YM155 on survivin and MCL-1 protein levels of MM cells is shown. The cells were cultured with YM155 during 24h and the western blot assays were carried out as indicated in material methods. Band intensities were quantified using image J software, calculated as relative values to the control protein tubuline and plotted as relative to the expression levels of cells cultured without YM155. In B, the type of interaction between YM155 and CTLs (see figure 5C-D) in the presence of accessory cells was analyzed using Compusyn software (version 1.0, 2004 �). In the plots (A) the CI values corresponding to the doses in figure 5 are shown. A CI value of 1 indicates synergy, additive effects or antagonism, respectively. In C the supernatants of assays as described in Fig 5C-D granzyme B release was measured using ELISA (B). Results are expressed as the mean values of the triplicate cultures. Error bars represent the SEM. Results are representative of 3 independent assays

Supplementary Figure Legends from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Fig. S3 from Stromal-mediated protection of tyrosine kinase inhibitor-treated BCR-ABL-expressing leukemia cells

Supplementary Fig. S2 from Stromal-mediated protection of tyrosine kinase inhibitor-treated BCR-ABL-expressing leukemia cells

Supplementary Table S1 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Fig. S3 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Supplementary Fig. S7 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Purpose: p53 is inactivated in many human malignancies through missense mutations or overexpression of the human homologue of Mdm2 (Hdm2), an E3 ubiquitin ligase that ubiquitinates p53, thereby promoting its proteasomal degradation. The cis-imidazoline nutlin-3 can disrupt the p53-Hdm2 interaction and activate p53, inducing apoptosis in vitro in many malignancies, including multiple myeloma (MM).Experimental Design: We hypothesized that suppression of Hdm2-mediated p53 ubiquitination may augment sequelae of p53 accumulation caused by proteasomal inhibition. We compared the response of MM cells versus several epithelial cancer models to the proteasome inhibitor bortezomib in combination with nutlin-3.Results: The combination of sublethal concentrations of bortezomib plus nutlin-3 induced additive cytotoxicity against bortezomib-sensitive MM cell lines. Importantly, however, in breast, prostate, colon, and thyroid (papillary, follicular, anaplastic, and medullary) carcinoma cell lines, this combination triggered synergistic cytotoxicity, and increased expression of p53, p21, Hdm2, Bax, Noxa, PUMA, and cleavage of caspase-3 and poly ADP ribose polymerase. Coculture with bone marrow stromal cells attenuated MM cell sensitivity to nutlin-3 monotherapy and was associated with evidence of suppression of p53 activity in MM cells, whereas combined bortezomib-nutlin-3 treatment maintained cytotoxicity even in the presence of bone marrow stromal cells.Conclusions: This differential response of MM versus epithelial carcinomas to combination of nutlin-3 with bortezomib sheds new light on the role of p53 in bortezomib-induced apoptosis. Concurrent Hdm2 inhibition with bortezomib may extend the spectrum of bortezomib applications to malignancies with currently limited sensitivity to single-agent bortezomib or, in the future, to MM patients with decreased clinical responsiveness to bortezomib-based therapy. (Clin Cancer Res 2009;15(23):7153–60)

Supplementary Figure 4 - PDF file 219K, FasL upregulation on CTLs upon MM cell recognition is not hampered by presence of accessory cells. CD4+ (A) and CD8+ (B) CTLs were cultured alone (unstimulated) or in the presence of tumor cells and in presence or absence of accessory cells as indicated. After 3 hours of co-incubation CTLs were evaluated for CD178 (Fas ligand) expression. Percentage of FasL expressing cells is indicated

Supplementary Fig. S8 from Potentiation of antileukemic therapies by Smac mimetic, LBW242: effects on mutant FLT3-expressing cells

Clinical studies of patients with chronic myeloid leukemia revealed that a common pattern of response is a dramatic fall in the circulating population of blast cells, with a minimal or delayed decrease in marrow blasts, suggesting a protective environment. These observations suggest that a greater understanding of the interaction of stromal cells with leukemic cells is essential. Here, we present an in vivo system for monitoring relative tumor accumulation in leukemic mice and residual disease in leukemic mice treated with a tyrosine kinase inhibitor and an in vitro system for identifying integral factors involved in stromal-mediated cytoprotection. Using the in vivo model, we observed high tumor burden/residual disease in tissues characterized as significant sources of hematopoiesis-promoting stroma, with bone marrow stroma most frequently showing the highest accumulation of leukemia in untreated and nilotinib-treated mice as well as partial protection of leukemic cells from the inhibitory effects of nilotinib. These studies, which showed a pattern of leukemia distribution consistent with what is observed in imatinib- and nilotinib-treated chronic myeloid leukemia patients, were followed by a more in-depth analysis of stroma-leukemia cell interactions that lead to protection of leukemia cells from nilotinib-induced cytotoxicity. For the latter, we used the human BCR-ABL-positive cell line, KU812F, and the human bone marrow stroma cell line, HS-5, to more closely approximate the bone marrow–associated cytoprotection observed in drug-treated leukemia patients. This in vitro system helped to elucidate stromal-secreted viability factors that may play a role in stromal-mediated cytoprotection of tyrosine kinase inhibitor-treated leukemia cells. [Mol Cancer Ther 2008;7(5):1121–9]

Supplementary Figures 1-7 from Antimyeloma Activity of the Orally Bioavailable Dual Phosphatidylinositol 3-Kinase/Mammalian Target of Rapamycin Inhibitor NVP-BEZ235

Summary Jasmonates, plant stress hormones, have been demonstrated to be effective in killing various types of cancer cells. We therefore tested if methyljasmonate (MJ) has activity against multiple myeloma (MM) in vitro and in vivo. MM cell lines and primary MM tumour cells responded to MJ in vitro at concentrations that did not significantly affect normal haematopoietic cells, without stroma-mediated resistance. Brief MJ exposures of MM cells caused release of Hexokinase 2 (HK2) from mitochondria, rapid ATP depletion, perturbation of major intracellular signalling pathways, and ensuing mainly apoptotic cell death. Sensitivity to MJ correlated with lower cellular glucose consumption and lactate production, as well as lower intracellular protein levels of HK2, phosphorylated Voltage-dependent anion channel 2/3 (pVDAC2/3) and Aldo-keto reductase family 1 member C1 (AKR1C1), which represent potential biomarkers of responsiveness to MJ treatment, especially as AKR1C1 transcript levels also correlate with clinical outcome in bortezomib- or dexamethasone-treated MM patients. Interestingly, MJ synergized with bortezomib in vitro and prolonged survival of immunocompromised mice harbouring diffuse lesions of MM.1S cells compared to vehicle-treated mice (P = 0·0046). These studies indicate that jasmonates represent a new, promising strategy to treat MM.

The use of combination drug regimens has dramatically improved the clinical outcome for patients with multiple myeloma. However, to date, combination treatments have been limited to approved drugs and a small number of emerging agents. Using a systematic approach to identify synergistic drug combinations, combination high-throughput screening (cHTS) technology, adenosine A2A and β-2 adrenergic receptor (β2AR) agonists were shown to be highly synergistic, selective, and novel agents that enhance glucocorticoid activity in B-cell malignancies. Unexpectedly, A2A and β2AR agonists also synergize with melphalan, lenalidomide, bortezomib, and doxorubicin. An analysis of agonists, in combination with dexamethasone or melphalan in 83 cell lines, reveals substantial activity in multiple myeloma and diffuse large B-cell lymphoma cell lines. Combination effects are also observed with dexamethasone as well as bortezomib, using multiple myeloma patient samples and mouse multiple myeloma xenograft assays. Our results provide compelling evidence in support of development of A2A and β2AR agonists for use in multi-drug combination therapy for multiple myeloma. Furthermore, use of cHTS for the discovery and evaluation of new targets and combination therapies has the potential to improve cancer treatment paradigms and patient outcomes. Mol Cancer Ther; 11(7); 1432–42. ©2012 AACR.

Background Isothiocyanates, a family of phytochemicals found in cruciferous vegetables, have cytotoxic effects against several types of tumor cells. Multiple myeloma is a fatal disease characterized by clonal proliferation of plasma cells in the bone marrow. The growing body of preclinical information on the anti-cancer activity of isothiocyanates led us to investigate their anti-myeloma properties.Design and Methods We evaluated the anti-myeloma activity of the isothiocyanates, sulforaphane and phenethyl isothiocyanate, on a panel of human myeloma cell lines as well as primary myeloma tumor cells. Cell viability, apoptosis, cell cycle alterations and cell proliferation were then analyzed in vitro and in a xenograft mouse model in vivo. The molecular sequelae of isothiocyanate treatment in multiple myeloma cells were evaluated by multiplex analyses using bead arrays and western blotting.Results We observed that sulforaphane and phenylethyl isothiocyanate have activity against myeloma cell lines and patients‘ myeloma cells both in vitro and in vivo using a myeloma xenograft mouse model. Isothiocyanates induced apoptotic death of myeloma cells; depletion of mitochondrial membrane potential; cleavage of PARP and caspases-3 and -9; as well as down-regulation of anti-apoptotic proteins including Mcl-1, X-IAP, c-IAP and survivin. Isothiocyanates induced G2/M cell cycle arrest accompanied by mitotic phosphorylation of histone H3. Multiplex analysis of phosphorylation of diverse components of signaling cascades revealed changes in MAPK activation; increased phosphorylation of c-jun and HSP27; as well as changes in the phosphorylation of Akt, and GSK3α/β and p53. Isothiocyanates suppressed proliferation of myeloma cells alone and when co-cultured with HS-5 stromal cells. Sulforaphane and phenylethyl isothiocyanate enhanced the in vitro anti-myeloma activity of several conventional and novel therapies used in multiple myeloma.Conclusions Our study shows that isothiocyanates have potent anti-myeloma activities and may enhance the activity of other anti-multiple myeloma agents. These results indicate that isothiocyanates may have therapeutic potential in multiple myeloma and provide the preclinical framework for future clinical studies of isothiocyanates in multiple myeloma.

Conventional anti-cancer drug screening is typically performed in the absence of accessory cells of the tumor microenvironment, which can profoundly alter anti-tumor drug activity. To address this major limitation, we developed the tumor cell-specific in vitro bioluminescence imaging (CS-BLI) assay. Tumor cells (e.g. myeloma, leukemia and solid tumors) stably expressing luciferase are co-cultured with non-malignant accessory cells (e.g. stromal cells) for selective quantification of tumor cell viability, in presence vs. absence of stromal cells or drug treatment. CS-BLI is high-throughput scalable and identifies stroma-induced chemoresistance in diverse malignancies, including imatinib-resistance in leukemic cells. A stromal-induced signature in tumor cells correlates with adverse clinical prognosis and includes signatures for activated Akt, Ras, NF-κB, HIF-1α, myc, hTERT, and IRF4; signatures for biological aggressiveness and for self-renewal. Unlike conventional screening, CS-BLI can also identify agents with increased activity against tumor cells interacting with stroma. One such compound, reversine, exhibits more potent activity in an orthotopic model of diffuse myeloma bone lesions than in conventional subcutaneous xenografts. Use of CS-BLI, therefore, enables refined screening of candidate anti-cancer agents to enrich preclinical pipelines with potential therapeutics that overcome stroma-mediated drug resistance and can act in a synthetic lethal manner in the context of tumor-stromal interactions.

We investigated the roles of specific subsets of donor APCs purified from bone marrow in donor T cell activation and graft-vs-leukemia (GvL) activity in murine models of hemopoietic stem cell transplantation. Lineage−CD11c+ APC precursors were separated from donor bone marrow based on expression of CD11b. Transplanting lineage−CD11c+CD11b− APC (CD11b− APC) in combination with c-kit+Sca-1+lineage− hemopoietic stem cells (HSC) and congenic donor T cells led to increased donor CD4+ and CD8+ T cell proliferation and higher donor T cell chimerism than with transplanting grafts containing HSC, T cells, and lineage−CD11c+CD11b+ APCs (CD11b+ APC), or grafts containing only HSC and T cells. Transplanting CD11b− APCs induced Th1/type 1 cytotoxic T lymphocyte donor T cell immune polarization and enhanced GvL activity of donor T cells without increased graft-vs-host disease in both MHC- and minor histocompatibility Ag-mismatched murine hemopoietic stem cell transplantation models, whereas CD11b+ APCs led to Th2/type 2 cytotoxic T lymphocyte donor T cell immune polarization. Donor CD11b− APCs were plasmacytoid dendritic cell progenitors (>90% CD317; PDCA-1+) and up-regulated CD80, CD86, and IL-12 during alloantigen presentation, whereas CD11b+ APCs expressed Gr-1 and up-regulated expression of programmed death ligands-1 and 2 after activation. These results are the first to show that manipulation of the content of donor APCs in allogeneic HSC grafts can regulate donor T cell immunity and enhance GvL without increasing graft-vs-host disease activity.

Purpose: p53 is inactivated in many human malignancies through missense mutations or overexpression of the human homologue of Mdm2 (Hdm2), an E3 ubiquitin ligase that ubiquitinates p53, thereby promoting its proteasomal degradation. The cis-imidazoline nutlin-3 can disrupt the p53-Hdm2 interaction and activate p53, inducing apoptosis in vitro in many malignancies, including multiple myeloma (MM). Experimental Design: We hypothesized that suppression of Hdm2-mediated p53 ubiquitination may augment sequelae of p53 accumulation caused by proteasomal inhibition. We compared the response of MM cells versus several epithelial cancer models to the proteasome inhibitor bortezomib in combination with nutlin-3. Results: The combination of sublethal concentrations of bortezomib plus nutlin-3 induced additive cytotoxicity against bortezomib-sensitive MM cell lines. Importantly, however, in breast, prostate, colon, and thyroid (papillary, follicular, anaplastic, and medullary) carcinoma cell lines, this combination triggered synergistic cytotoxicity, and increased expression of p53, p21, Hdm2, Bax, Noxa, PUMA, and cleavage of caspase-3 and poly ADP ribose polymerase. Coculture with bone marrow stromal cells attenuated MM cell sensitivity to nutlin-3 monotherapy and was associated with evidence of suppression of p53 activity in MM cells, whereas combined bortezomib-nutlin-3 treatment maintained cytotoxicity even in the presence of bone marrow stromal cells. Conclusions: This differential response of MM versus epithelial carcinomas to combination of nutlin-3 with bortezomib sheds new light on the role of p53 in bortezomib-induced apoptosis. Concurrent Hdm2 inhibition with bortezomib may extend the spectrum of bortezomib applications to malignancies with currently limited sensitivity to single-agent bortezomib or, in the future, to MM patients with decreased clinical responsiveness to bortezomib-based therapy. (Clin Cancer Res 2009;15(23):7153–60)

The successful clinical development of thalidomide, bortezomib, and lenalidomide not only transformed the therapeutic management of multiple myeloma (MM) but also catalyzed a renewed interest in the development of additional classes of novel agents for this disease. This review focuses on a series of new therapeutics that have shown promising preclinical results, as well as encouraging safety profiles and early evidence of anti-MM activity in clinical studies, either alone or in combination with other, conventional or novel, anti-MM treatments. These agents include second-generation proteasome inhibitors and immunomodulatory agents, as well as members of other therapeutic classes, such as histone deacetylase inhibitors (HDAC), heat shock protein 90 (Hsp90) inhibitors, and the alkylphospholipid Akt inhibitor perifosine.

Clinical studies of patients with chronic myeloid leukemia revealed that a common pattern of response is a dramatic fall in the circulating population of blast cells, with a minimal or delayed decrease in marrow blasts, suggesting a protective environment. These observations suggest that a greater understanding of the interaction of stromal cells with leukemic cells is essential. Here, we present an in vivo system for monitoring relative tumor accumulation in leukemic mice and residual disease in leukemic mice treated with a tyrosine kinase inhibitor and an in vitro system for identifying integral factors involved in stromal-mediated cytoprotection. Using the in vivo model, we observed high tumor burden/residual disease in tissues characterized as significant sources of hematopoiesis-promoting stroma, with bone marrow stroma most frequently showing the highest accumulation of leukemia in untreated and nilotinib-treated mice as well as partial protection of leukemic cells from the inhibitory effects of nilotinib. These studies, which showed a pattern of leukemia distribution consistent with what is observed in imatinib- and nilotinib-treated chronic myeloid leukemia patients, were followed by a more in-depth analysis of stroma-leukemia cell interactions that lead to protection of leukemia cells from nilotinib-induced cytotoxicity. For the latter, we used the human BCR-ABL-positive cell line, KU812F, and the human bone marrow stroma cell line, HS-5, to more closely approximate the bone marrow–associated cytoprotection observed in drug-treated leukemia patients. This in vitro system helped to elucidate stromal-secreted viability factors that may play a role in stromal-mediated cytoprotection of tyrosine kinase inhibitor-treated leukemia cells. [Mol Cancer Ther 2008;7(5):1121–9]

Multiple myeloma (MM) is viewed as a prototypic disease state for the study of how neoplastic cells interact with their local bone marrow (BM) microenvironment. This interaction reflects not only the osteo-tropic clinical behavior of MM and the clinical impact of the lytic bone lesions caused by its tumor cells but also underlines the broadly accepted notion that nonneoplastic cells of the BM can attenuate the activity of cytotoxic chemotherapy and glucocorticoids. This article summarizes the recent progress in characterization, at the molecular and cellular levels, of how the BM milieu interacts with MM cells and modifies their biologic behavior.

Context: The Bcl-2 family of proteins regulates apoptosis in various models and may represent a promising therapeutic target in human malignancies. Objective/Methods: We evaluated the sensitivity of thyroid carcinoma cell lines (two papillary, one follicular, two anaplastic, three medullary) in vitro to BH3I-1 and BH3I-2′, two cell-permeable inhibitors of the Bcl-2 homology (BH)-3 domain-mediated interaction between proapoptotic and antiapoptotic Bcl-2 family members. The thyroid carcinoma cell line FRO was stably transfected with cDNA for Bcl-2 or constitutively active Akt and evaluated for sensitivity to BH3-domain inhibition. Results: BH3-domain inhibition disrupted the mitochondrial membrane potential in thyroid carcinoma cells, induced caspase-dependent apoptosis, and potently sensitized them to sublethal concentrations of doxorubicin and the proteasome inhibitor bortezomib (Velcade). Overexpression of constitutively active Akt suppressed BH3I-1-induced cell death. Bcl-2-overexpressing FRO cells were more resistant to conventional chemotherapeutic agents (such as doxorubicin) but significantly more sensitive to BH3I-1 than control cells and were found to overexpress caspase-9, caspase-8, Bmf, Bok, and Bik transcripts and express less A1, BRaf, and FLIP transcripts. Conclusions: Bcl-2 expression protects thyroid carcinomas against chemotherapy-induced apoptosis. Nevertheless, overexpression of Bcl-2 may result in “oncogene addiction” of the cancer cell, which can be exploited by using BH3-domain inhibitors alone or in combination with other agents, including conventional chemotherapeutics (such as doxorubicin) or novel targeted therapies (such as the proteasome inhibitor bortezomib), for the treatment of aggressive thyroid cancer, including the medullary and anaplastic types.

Members of the inhibitor of apoptosis protein (IAP) family play a role in mediating apoptosis. Studies suggest that these proteins may be a viable target in leukemia because they have been found to be variably expressed in acute leukemias and are associated with chemosensitivity, chemoresistance, disease progression, remission, and patient survival. Another promising therapeutic target, FLT3, is mutated in about one third of acute myelogenous leukemia (AML) patients; promising results have recently been achieved in clinical trials investigating the effects of the protein tyrosine kinase inhibitor PKC412 on AML patients harboring mutations in the FLT3 protein. Of growing concern, however, is the development of drug resistance resulting from the emergence of point mutations in targeted tyrosine kinases used for treatment of acute leukemia patients. One approach to overriding resistance is to combine structurally unrelated inhibitors and/or inhibitors of different signaling pathways. The proapoptotic IAP inhibitor, LBW242, was shown in proliferation studies done in vitro to enhance the killing of PKC412-sensitive and PKC412-resistant cell lines expressing mutant FLT3 when combined with either PKC412 or standard cytotoxic agents (doxorubicin and Ara-c). In addition, in an in vivo imaging assay using bioluminescence as a measure of tumor burden, a total of 12 male NCr-nude mice were treated for 10 days with p.o. administration of vehicle, LBW242 (50 mg/kg/day), PKC412 (40 mg/kg/day), or a combination of LBW242 and PKC412; the lowest tumor burden was observed in the drug combination group. Finally, the combination of LBW242 and PKC412 was sufficient to override stromal-mediated viability signaling conferring resistance to PKC412. [Mol Cancer Ther 2007;6(7):1951–61]

B-Raf is an important mediator of cell proliferation and survival signals transduced via the Ras-Raf-MEK-ERK cascade. BRAF mutations have been detected in several tumors, including papillary thyroid carcinoma, but the precise role of B-Raf as a therapeutic target for thyroid carcinoma is still under investigation. We analyzed a panel of 93 specimens and 14 thyroid carcinoma cell lines for the presence of BRAF mutations and activation of the mitogen-activated protein/ERK kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway. We also compared the effect of a B-Raf small inhibitory RNA construct and the B-Raf kinase inhibitor AAL881 on both B-Raf wild-type and mutant thyroid carcinoma cell lines. We found a high prevalence of the T1799A (V600E) mutation in papillary and anaplastic carcinoma specimens and cell lines. There was no difference in patient age, B-Raf expression, Ki67 immunostaining, or clinical stage at presentation between wild-type and BRAFV600E specimens. Immunodetection of phosphorylated and total forms of MEK and ERK revealed no difference in their phosphorylation between wild-type and BRAFV600E patient specimens or cell lines. Furthermore, a small inhibitory RNA construct targeting the expression of both wild-type B-Raf and B-RafV600E induced a comparable reduction of viability in both wild-type and BRAFV600E mutant cancer cells. Interestingly, AAL881 inhibited MEK and ERK phosphorylation and induced apoptosis preferentially in BRAFV600E-harboring cells than wild-type ones, possibly because of better inhibitory activity against B-RafV600E. We conclude that B-Raf is important for the pathophysiology of thyroid carcinomas irrespective of mutational status. Small molecule inhibitors that selectively target B-RafV600E may provide clinical benefit for patients with thyroid cancer. [Mol Cancer Ther 2007;6(3):1070–8]

In multiple myeloma (MM) protein kinase C (PKC) signaling pathways have been implicated in cell proliferation, survival, and migration. Here we investigated the novel, orally available PKC-inhibitor enzastaurin for its anti-MM activity. Enzastaurin specifically inhibits phorbol ester–induced activation of PKC isoforms, as well as phosphorylation of downstream signaling molecules MARCKS and PKCμ. Importantly, it also inhibits PKC activation triggered by growth factors and cytokines secreted by bone marrow stromal cells (BMSCs), costimulation with fibronectin, vascular endothelial growth factor (VEGF), or interleukin-6 (IL-6), as well as MM patient serum. Consequently, enzastaurin inhibits proliferation, survival, and migration of MM cell lines and MM cells isolated from multidrug-resistant patients and overcomes MM-cell growth triggered by binding to BMSCs and endothelial cells. Importantly, strong synergistic cytotoxicity is observed when enzastaurin is combined with bortezomib and moderate synergistic or additive effects when combined with melphalan or lenalidomide. Finally, tumor growth, survival, and angiogenesis are abrogated by enzastaurin in an in vivo xenograft model of human MM. Our results therefore demonstrate in vitro and in vivo efficacy of the orally available PKC inhibitor enzastaurin in MM and strongly support its clinical evaluation, alone or in combination therapies, to improve outcome in patients with MM.

Purpose: The death receptor Fas is present in thyroid carcinomas, yet fails to trigger apoptosis. Interestingly, Fas has been reported to be actually overexpressed in papillary thyroid carcinomas, suggesting that it may confer a survival advantage. Experimental Design: We investigated the expression and activation status of Fas pathway mediators in thyroid carcinoma cell lines and tumor specimens. Results: All cell lines tested express Fas-associated death domain, procaspase-8, procaspase-9, and procaspase-3; resistance to Fas-mediated apoptosis could not be attributed to lack of any of these apoptosis mediators. Moreover, Fas death domain mutations were not found in our study. The proteasome inhibitors MG132 and PS-341 (bortezomib, Velcade), which lead to accumulation of the nuclear factor κB (NF-κB) inhibitor IκB, did not sensitize SW579 cells to Fas-mediated apoptosis, suggesting that resistance to Fas-mediated apoptosis is not due to proteasome or NF-κB activity. Cross-linking of Fas in vitro induced recruitment of Fas-associated death domain–like interleukin-1β–converting enzyme inhibitory protein (FLIP) instead of procaspase-8. Inhibition of FLIP expression with a FLIP antisense oligonucleotide resulted in significant sensitization to Fas-mediated apoptosis. Fas cross-linking promoted BrdUrd incorporation; activated the mitogen-activated protein kinase/extracellular signal–regulated kinase kinase/extracellular signal–regulated kinase, NF-κB, and activator protein-1 pathways in thyroid carcinoma cells in vitro; and protected cells from tumor necrosis factor–related apoptosis-inducing ligand–induced apoptosis. We also found that good prognosis papillary thyroid carcinoma specimens exhibited higher immunoreactivity for cleaved (activated) caspase-8 than poor prognosis tumors. Conclusions: In thyroid carcinomas, the proteolytic cleavage and activation of caspase-8 depends on the balance between expression levels for procaspase-8 and FLIP and correlates with favorable clinical prognosis. Fas may actually stimulate proliferation and confer a survival advantage to thyroid cancer cells.

Using the cationic polymer, Polybrene, and the anionic polymer, chondroitin sulfate C, we concentrated recombinant retrovirus pseudotyped with an ecotropic envelope, which is susceptible to inactivation by high-speed concentration methods. To evaluate gene marking, murine bone marrow was harvested from C3H mice, transduced with polymer-concentrated GFP virus, and transplanted into lethally irradiated recipients. Total gene marking in mice averaged 30-35% at 8 weeks post-transplant and transgene expression remained stable for over 16 weeks. Using the polymer concentration method, a second retroviral vector encoding the drug resistant variant of dihydrofolate reductase (L22Y-DHFR) was concentrated and tested. Approximately 40% of transduced murine bone marrow progenitor cells were protected against trimetrexate concentrations that completely eliminated the growth of non-modified cells. These results show that anionic and cationic polymers can be combined to rapidly concentrate viruses that are normally difficult to concentrate, and the concentrated virus efficiently transduces hematopoietic stem cells.

BTK is a member of the TEC family of non-receptor tyrosine kinases whose deregulation has been implicated in a variety of B-cell-related diseases. We have used structure-based drug design in conjunction with kinome profiling and cellular assays to develop a potent, selective, and irreversible BTK kinase inhibitor, QL47, which covalently modifies Cys481. QL47 inhibits BTK kinase activity with an IC50 of 7 nM, inhibits autophosphorylation of BTK on Tyr223 in cells with an EC50 of 475 nM, and inhibits phosphorylation of a downstream effector PLCγ2 (Tyr759) with an EC50 of 318 nM. In Ramos cells QL47 induces a G1 cell cycle arrest that is associated with pronounced degradation of BTK protein. QL47 inhibits the proliferation of B-cell lymphoma cancer cell lines at submicromolar concentrations.