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Purpose: To determine the safety and describe the antitumor activity of tipifarnib in patients with myelodysplastic syndrome (MDS) using an alternate-week schedule. Experimental Design: Patients with MDS were given tipifarnib, escalating from 100 mg orally twice daily until the maximum tolerated dose for 8 weeks followed by maintenance therapy (same dose/schedule) for patients with stable disease or better. Results: Sixty-three patients were treated. The most common toxicity was myelosuppression (60% of patients). Twenty percent of patients had no side effects. Nonhematologic toxicities included fatigue (20%), skin rash (9%), diarrhea (16%), increase in liver transaminases (14%) and bilirubin (11%), and nausea (11%). Dose-limiting toxicities of ataxia (n = 1), fatigue (n = 1), nausea (n = 1), and neutropenic fever (n = 2) occurred at tipifarnib doses above 1,200 mg/d. Sixteen of 61 (26%) evaluable patients responded (3 complete remissions and 13 hematologic improvements) with major platelet responses being most common (11 of 16 responders). There was no obvious dose-response relationship. Four of the 16 responders (25%; including a complete responder) were treated at the lowest dose level (100 mg twice daily). Only one responder had a Ras mutation. Giving tipifarnib resulted in potent inhibition of farnesyl transferase (usually more than 75%) in peripheral blood mononuclear cells regardless of dose. Partial farnesyl transferase inhibition persisted during the week off. Conclusions: Alternate-week tipifarnib is active and well tolerated in patients with MDS at doses up to and including 600 mg orally twice daily. The biological activity of tipifarnib is not dependent on dose.

Synthetic chemical probes designed to simultaneously targeting multiple sites of protein surfaces are of interest owing to their potential application as site specific modulators of protein-protein interactions. A new approach toward bivalent inhibitors of mammalian type I geranylgeranyltransferase (GGTase I) based on module assembly for simultaneous recognition of both interior and exterior protein surfaces is reported. The inhibitors synthesized in this study consist of two modules linked by an alkyl spacer; one is the tetrapeptide CVIL module for binding to the interior protein surface (active pocket) and the other is a 3,4,5-alkoxy substituted benzoyl motif that contains three aminoalkyl groups designed to bind to the negatively charged protein exterior surface near the active site. The compounds were screened by two distinct enzyme inhibition assays based on fluorescence spectroscopy and incorporation of a [(3)H]-labeled prenyl group onto a protein substrate. The bivalent inhibitors block GGTase I enzymatic activity with K(i) values in the submicromolar range and are approximately one order of magnitude and more than 150 times more effective than the tetrapeptide CVIL and the methyl benzoate derivatives, respectively. The bivalent compounds 6 and 8 were shown to be competitive inhibitors, suggesting that the CVIL module anchors the whole molecule to the GGTase I active site and delivers the other module to the targeting protein surface. Thus, our module-assembly approach resulted in simultaneous multiple-site recognition, and as a consequence, synergetic inhibition of GGTase I activity, thereby providing a new approach in designing protein-surface-directed inhibitors for targeting protein-protein interactions.

Catalysts based on natural phosphate (NP) are able to catalyze the synthesis of α-hydroxyphosphonates by reaction of dimethyl or diethyl phosphite with aldehydes and ketones at room temperature. This eco-friendly method is more efficient with modified phosphate, either impregnated with KF (KF/NP) or modified with sodium (Na/NP). Excellent yields (89–99%) were obtained with Na/NP in very short reaction times, 1–5 min in the case of aldehydes and 1–1.5 h in the case of ketones, a remarkable activity considering the very low surface area of the solid and the absence of solvent during the synthesis process. This catalyst was fully recoverable after calcination in four consecutive runs., This work was made possible by the generous financial support of the Agencia Española de Cooperación Internacional (Project A/3810/05), the C.I.C.Y.T. (Project CTQ2005-08016) and The Research Center for Studies on Mineral Phosphates (CERPHOS), OCP Group, Morocco.

Stat3 is hyperactivated in many human tumors and represents a valid target for anticancer drug design. We present a novel small-molecule Stat3 inhibitor, S3I-M2001, and describe the dynamics of intracellular processing of activated Stat3 within the context of the biochemical and biological effects of the Stat3 inhibitor. S3I-M2001 is an oxazole-based peptidomimetic of the Stat3 Src homology (SH) 2 domain-binding phosphotyrosine peptide that selectively disrupts active Stat3:Stat3 dimers. Consequently, hyperactivated Stat3, which hitherto occurs as "dotlike" structures of nuclear bodies, undergoes an early aggregation into nonfunctional perinuclear aggresomes and a late-phase proteasome-mediated degradation in malignant cells treated with S3I-M2001. Thus, S3I-M2001 inhibited Stat3-dependent transcriptional regulation of tumor survival genes, such as Bcl-xL. Furthermore, Stat3-dependent malignant transformation, survival, and migration and invasion of mouse and human cancer cells harboring persistently activated Stat3 were inhibited by S3I-M2001. Finally, S3I-M2001 inhibited growth of human breast tumor xenografts. The study identifies a novel Stat3 inhibitor, S3I-M2001, with antitumor cell effects mediated in part through a biphasic loss of functional Stat3. The study represents the first on intracellular Stat3 stability and processing following inhibition by a small molecule that has significant antitumor activity.

HPP1 is a recently discovered gene that is epigenetically silenced in a number of tumor types, suggesting a potential role as a tumor suppressor. However, whether HPP1 has tumor suppressor activity is not clearly known. We have sought to investigate the effects of HPP1 on tumor growth and survival and to identify signaling pathways that mediate HPP1's mechanism of action. Forced expression of HPP1 into HCT116 colon cancer cell lines blocked the ability of HCT116 tumors to grown in vivo in nude mice. In cell culture, ectopic expression of HPP1 induces apoptosis and potently inhibits soft agar colony formation. HPP1 overexpression was also associated with a moderate reduction in in vitro proliferation characterized by an accumulation of cells in the G0/G1 phase of the cell cycle. Microarray analysis revealed that ectopic expression of HPP1 resulted in a dramatic upregulation of STAT1 as well as a large number of associated interferon-inducible genes. RNA interference-mediated abrogation of STAT1 reversed HPP1's antiproliferative effects. We conclude that HPP1 demonstrates tumor suppressive and pro-apoptotic activity, both in vitro and in vivo. Coupled with its inactivation in a number of tumor types, our data provides evidence to support the role of HPP1 as a tumor suppressor gene. Moreover, activation of the STAT1 pathway likely represents the principal mediator of HPP1's tumor suppressive properties.

S3I-201 (NSC 74859) is a chemical probe inhibitor of Stat3 activity, which was identified from the National Cancer Institute chemical libraries by using structure-based virtual screening with a computer model of the Stat3 SH2 domain bound to its Stat3 phosphotyrosine peptide derived from the x-ray crystal structure of the Stat3β homodimer. S3I-201 inhibits Stat3·Stat3 complex formation and Stat3 DNA-binding and transcriptional activities. Furthermore, S3I-201 inhibits growth and induces apoptosis preferentially in tumor cells that contain persistently activated Stat3. Constitutively dimerized and active Stat3C and Stat3 SH2 domain rescue tumor cells from S3I-201-induced apoptosis. Finally, S3I-201 inhibits the expression of the Stat3-regulated genes encoding cyclin D1, Bcl-xL, and survivin and inhibits the growth of human breast tumors in vivo . These findings strongly suggest that the antitumor activity of S3I-201 is mediated in part through inhibition of aberrant Stat3 activation and provide the proof-of-concept for the potential clinical use of Stat3 inhibitors such as S3I-201 in tumors harboring aberrant Stat3.

In this study, we synthesized some natural and semisynthetic prenyloxyphenylpropanoids (e.g., coumarins and cinnamic acid derivatives) and we assessed their in vitro inhibitory activity against farnesyl transferase (FTase) and geranylgeranyl transferase I (GGTase I). No compound was an effective inhibitor of FTase, while farnesyloxycinnamic acids were shown to selectively inhibit GGTase I with IC(50) values ranging from 28 to 39 microM.

Importance: In recent years, several studies have suggested effectiveness of green tea catechins in prostate cancer (PCa) chemoprevention. With the exception of one trial from Italy, this has not been further tested in a randomized trial setting in high-risk men with atypical small acinar proliferation (ASAP) or high grade prostatic intraepithelial neoplasia (HGPIN). Objective: To determine whether the daily consumption of a standardized formulation of green tea catechins (Polyphenon E) supplement for 1 year reduces the rate of progression to PCa in men, diagnosed with HGPIN or ASAP. Additional objectives were to evaluate tolerance, lower urinary tract symptoms (LUTS) and quality of life (QOL). Design, setting and participants: A randomized, double-blinded trial was conducted from September 2008 to March 2014 at medical centers in the US targeting 97 men diagnosed HGPIN or ASAP, randomized to treatment (n=49) or control arm (n=48). Supplement or placebo was initiated within 3 months of initial biopsy and continued for 1 year. Intervention: Participants were block randomized by baseline diagnosis and study site to receive Polyphenon E (PolyE), a decaffeinated, standardized green tea catechin mixture, the main component of which is (−)-epigallocatechin-3-gallate (EGCG) at a dose of 400 mgs EGCG per day (200 mgs twice a day [BID]), or placebo. Main outcomes and measures: Rate of progression to PCa at one year in men treated with PolyE or placebo following diagnosis of HGPIN or ASAP; evaluation of tolerance, LUTS and QOL. Results: Overall, we did not observe a difference in the number of men who progressed to PCa in one year in the Poly E (4/49) arm compared to placebo arm(6/48). Secondary analyses of patients reaching a definitive endpoint revealed that among men with baseline diagnosis of HGPIN, a greater number progressed to ASAP or PCa in the placebo arm (10/25) compared to the PolyE arm (3/26; P Conclusions and Relevance: Daily intake of a standardized, decaffeinated catechin mixture containing 400 mgs EGCG (200 mgs BID) for 1 year is well tolerated and appears to produce chemoprevention effects in the early stages (HGPIN to ASAP) of prostate carcinogenesis. These findings should be confirmed in a phase III clinical trial prior to recommending use in clinical settings. Trial Registration: Clinical Trials.gov Identifier: NCT00596011 Acknowledgement: The research study was funded by the National Institute of Health- National Cancer Institute R01 CA12060-01A1. We acknowledge the contributions of Anthony M. Neuger, Domenico Coppola, Binglin Yue, (Moffitt Cancer Center); Kyle Anderson (Minneapolis VA Medical Center, Minneapolis, MN); Eduard Trabulsi (Jefferson Medical College, Philadelphia, PA); Tajammul Fazili (Overton Brooks VA, Shreveport, LA); Edward Giovanucci (Harvard University); Gregory Zagaja (University of Chicago, Chicago, IL); Shahnjayla Connors (University of Washington, St. Louis, MO); Folake Odedina (University of Florida). External Data Monitoring Board: Omer Kucuk, (Emory University), Phyllis Bowen (Retired), and Steven Clinton (Ohio State University). Citation Format: Nagi B. Kumar, Julio Pow-Sang, Kathleen M. Egan, Philippe A. Spiess, Shohreh Dickinson, Raoul Salup, Mohamed Helal, Jerry McLarty, Christopher R. Williams, Fred Schreiber, Said Sebti, Aslam Kazi, Loveleen Kang, Gwen Quinn, Tiffany Smith, Karen Diaz, Ganna Chornokur, Theresa Crocker, Michael J. Schell. Effect of polyphenon E on progression to prostate cancer after diagnosis of high grade prostatic intraepithelial neoplasia. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr PR06.

Background: Pancreatic cancer, a lethal and aggressive malignancy is the fourth leading cause of cancer-related deaths in the United States. One of the main reasons for this outcome includes the lack of effective prevention strategies for recurrent disease. Pancreatic cancer stem cells (CSCs) have been implicated in the development of pancreatic cancer metastasis, resistance to chemotherapy and its recurrence following surgical extirpation. We have shown that natural vitamin E δ-tocotrienol is the most bioactive tocotrienols against pancreatic cancer in vitro as well as in vivo models. The purpose of this study was to evaluate the effect of δ-tocotrienol on tumor metastatic EMT, migration, invasion, angiogenesis and CSCs signaling in metastatic human pancreatic cancer cells. Methods: Human metastatic pancreatic cancer cells L3.6pl expressing luciferase were orthotopically implanted into pancreas of Athymic nude mice (n = 10) and after one week they were randomized in two groups: 1) vehicle control (ethanol extracted olive oil) and 2) δ-tocotrienol (200 mg/kg, orally twice a day) for 4 weeks. The tumor volume, tumor weight, liver and lung metastasis were recorded. The tumor tissues were analyzed for metastasis markers, epithelial to mesenchymal transition (EMT), and angiogenesis. In vitro L3.6pl cells were treated with δ-tocotrienol (50 μM) and used for migration and invasion assay, isolation of CSCs and spheroid formation, transcription factors and CSCs signaling markers were determined by Western blotting. Results: Vitamin E δ-tocotrienol significantly inhibited the pancreatic tumor growth [tumor volume (50%) and weight (60%)] and metastasis in the liver and lung, CSCs spheroid formation, migration and invasion compared to control. δ-tocotrienol induced apoptosis (PARP1 cleavage and Bax expression) compared to control. δ-tocotrienol also inhibited EMT (E-cadherin to vimentin), metastasis (MMP9), angiogenesis (VEGF), CSCs transcription factors (Nanog, Oct4, Sox2 and KLF4) and oncogenic signaling (Notch-1 and pERK) compared to control. Conclusion: Vitamin E δ-tocotrienol inhibited metastasis of human pancreatic tumor through inhibition of EMT, migration, invasion, angiogenesis, cancer stem cell signaling and induction of apoptosis. Citation Format: Kazim Husain, Said M. Sebti, Mokenge P. Malafa. Vitamin E delta-tocotrienol inhibits metastasis and targets cancer stem cell signaling in human pancreatic cancer. [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 4383. doi:10.1158/1538-7445.AM2015-4383

Although mutant KRas significantly contributes to human oncogenesis and patient tumor resistance to therapy, there are no anticancer drugs directly targeting mt KRas available in clinic. A major effort in our laboratory is to identify novel compounds that bind mt KRas and inhibit potently and selectively KRas-driven malignant transformation. To this end, we have used a mixture-based synthetic combinatorial library (scaffold ranking library) containing over 6 million compounds in a mant-GDP assay to identify chemical scaffolds that inhibit the ability of GTP to displace mant-GDP from mt G12D KRas. Subsequent screening of the positional scanning libraries derived from the hit mixtures led to several individual compound hits with the most potent inhibiting the ability of GTP to displace mant-GDP from mt G12D KRas with IC50 of 61 μM. Current studies are focused on physical characterization of the hits to mt KRas and cellular activities of these hits in mt KRas-dependent and -independent human cancer cell lines. Citation Format: Perry C. Kennedy, Marc C. Guilanotti, Travis LsVoi, Said M. Sebti. Screening of a mixture-based synthetic combinatorial library identifies small molecules that inhibit the ability of GTP to displace mant-GDP from mutant G12D KRas. [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 2580. doi:10.1158/1538-7445.AM2015-2580

Little is known about the contributions of geranylgeranylated proteins to multiple myeloma (MM) malignancy, and whether targeting geranylgeranyltransferase I (GGT-1) is a viable therapeutic approach in myeloma is yet to be explored. In this study, we investigated the effects of GGTI-2418, a GGT-1 inhibitor that has reached phase I clinical trials, on MM malignancy in the 5TMG1 mouse model, where GGTI-2418 effects were assessed in the confines of the bone microenvironment that recapitulates the clinical disease in humans. GGTI-2418 treatment significantly decreased the serum levels of the MM biomarker IgG2B (M-protein) as well as the percentage of MM tumors within the tibia as demonstrated by H&E staining. X-ray and micro-CT analyses also identified that GGTI-2418 prevented MM induced bone disease with significantly lower tumor induced osteolysis and trabecular bone volume loss noted. Furthermore, treatment of mice with GGTI-2418 resulted in a significant activation of caspase 3 (apoptosis induction), accumulation of nuclear p27Kip in MM tumors (a positive prognostic biomarker for MM patients), and reduction of α-SMA levels in myofibroblasts surrounding the sinusoidal vasculature, suggesting decreased vascularization of marrow blood vessels. Importantly, GGTI-2418 treatment resulted in a significant increase in mouse median survival and delay in the onset of limb paralysis. In cell culture studies, GGTI-2417, the methylester pro-drug of GGTI-2418 that is better taken up by cultured cells, inhibited MM proliferation, increased p27kip levels, induced apoptosis and sensitized MM cells to bortezomib. Taken together, our preclinical studies suggest targeting GGT-1 as a viable therapeutic approach in MM, and warrant the investigation of GGTI-2418 in the clinic. Citation Format: Hua Yang, Michael F. Emmons, Christopher Cubitt, Ken Shain, Domenico Coppola, Daniel Sullivan, Conor C. Lynch, Lori Hazlehurst, Said M. Sebti. The geranylgeranyltransferase I inhibitor GGTI-2418 suppresses multiple myeloma malignancy in the 5TMG1 mouse model. [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 2605. doi:10.1158/1538-7445.AM2015-2605

While mutant (mt) KRas has proven to be difficult to target directly, mt KRas-driven cancer cells may gain dependencies on other signal transduction pathways. Therefore, exploring these dependencies may lead to the discovery of pathways and targets whose inhibition may induce synthetic lethality in cancer cells that depend on mt KRas. We have screened a kinase inhibitor library against 7 human cancer cell lines that harbor mt KRas; 4 mt KRas-dependent (A427 and H358 (lung), SW620 and SK-CO-1 (colon)); and 3 mt KRas-independent (HCT116, DLD-1 and HCT-8 (colon)) to identify kinase inhibitors that selectively inhibit the survival of mt KRas-dependent cancer cells. Our results show that 13 of the kinase inhibitors suppressed potently the survival of all 7 human cancer cell lines, 31 inhibited very weakly and 84 inhibited differentially each cell line, and the remaining compounds showed varied activities across cell lines. Importantly, 7 kinase inhibitors inhibited preferentially (p< 0.01) the viability of mt KRas-dependent over -independent human cancer cell lines. These results suggested that the 7 compounds may target kinases whose inhibition preferentially affects mt KRas-dependent cells. Analysis of the kinases that are targeted by these inhibitors revealed that these compounds target predominantly tyrosine kinases suggesting that at least in these cell lines these compounds may disrupt mt KRas “addiction” by inhibiting tyrosine kinase-dependent signaling. Citation Format: Norbert Berndt, Xiaolei Zhang, Rays H.Y. Jiang, Said M. Sebti. Kinome inhibitor screen identifies kinase inhibitors that inhibit selectively the survival of mutant K-Ras-dependent human cancer cells. [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 2153. doi:10.1158/1538-7445.AM2015-2153

Amplification, overexpression, and elevated activation of Akt have been detected in many human malignancies making it an important target for cancer therapy. The Akt substrate-binding site offers a large number of potential interactions to an appropriately designed small molecule and can form the basis for the development of selective inhibitors. Here, we report the progression of GSK3β substrate-mimetic inhibitors towards the development of a potent, small molecule substrate-mimetic inhibitor of Akt.

Recently, we have shown that RhoB suppresses EGFR-, ErbB2-, Ras- and Akt-mediated malignant transformation and metastasis. In this paper, we demonstrate that the novel antitumor agents farnesyltransferase inhibitors (FTIs) and geranylgeranyltransferase I inhibitors (GGTIs) upregulate RhoB expression in a wide spectrum of human cancer cells including those from pancreatic, breast, lung, colon, bladder and brain cancers. RhoB induction by FTI-277 and GGTI-298 occurs at the transcriptional level and is blocked by actinomycin D. Reverse transcription-PCR experiments documented that the increase in RhoB protein levels is due to an increase in RhoB transcription. Furthermore, treatment with FTIs and GGTIs of cancer cells results in HDAC1 dissociation, HAT association and histone acetylation of the RhoB promoter. Thus, promoter acetylation is a novel mechanism by which RhoB expression levels are regulated following treatment with the anticancer agents FTIs and GGTIs.

α-Tocopherol succinate (TS), an analogue of vitamin E, has growth-inhibitory activity in a wide spectrum of in vitro and in vivo cancer models. Here, we report that modulation of oncogenic Ras is associated with TS activity. TS inhibits the proliferation and induces apoptosis of NIH3T3 cells stably transfected with oncogenic K-Ras and H-Ras, but not NIH3T3 cells expressing empty vector. TS treatment resulted in decreased Ras protein levels in oncogenic Ras expressing NIH3T3 cells but not in parental NIH3T3 cells. Treatment with TS suppressed the levels of phospho-Akt and phospho-Erk1/2 in oncogenic Ras expressing NIH3T3 cells. Overexpression of constitutively active phosphoinositide-3-kinase, Akt, and Mek1/2 significantly attenuated TS growth inhibition of oncogenic Ras-transformed NIH3T3 mouse fibroblast cell lines. In addition, transcriptional targets of oncogenic Ras such as c-Myc, cyclin D1, and E2F1 were down-regulated by TS in oncogenic Ras-expressing cells. The above TS effects on oncogenic Ras signaling were also observed in endogenous oncogenic K-Ras expressing HCT 116 (human colon cancer) and MDA-MB-231 (human breast cancer) cells. Taken together, these data show that TS down-regulation of the Ras signaling pathways that are mediated by Mek/Erk and phosphoinositide-3-kinase/Akt plays, at least in part, a critical role in TS inhibition of proliferation and survival of transformed cells. This data supports further investigation of the chemopreventive and therapeutic potential of TS in tumors that are dependent on activated Ras signaling and identifies phosphor-Erk and phosphor-Akt as potential biomarkers of TS activity. [Mol Cancer Ther 2006;5(2):309–16]

Bif-1, a member of the endophilin B protein family, interacts with Bax and promotes interleukin-3 withdrawal-induced Bax conformational change and apoptosis when overexpressed in FL5.12 cells. Here, we provide evidence that Bif-1 plays a regulatory role in apoptotic activation of not only Bax but also Bak and appears to be involved in suppression of tumorigenesis. Inhibition of endogenous Bif-1 expression in HeLa cells by RNA interference abrogated the conformational change of Bax and Bak, cytochrome c release, and caspase 3 activation induced by various intrinsic death signals. Similar results were obtained in Bif-1 knockout mouse embryonic fibroblasts. While Bif-1 did not directly interact with Bak, it heterodimerized with Bax on mitochondria in intact cells, and this interaction was enhanced by apoptosis induction and preceded the Bax conformational change. Moreover, suppression of Bif-1 expression was associated with an enhanced ability of HeLa cells to form colonies in soft agar and tumors in nude mice. Taken together, these findings support the notion that Bif-1 is an important component of the mitochondrial pathway for apoptosis as a novel Bax/Bak activator, and loss of this proapoptotic molecule may contribute to tumorigenesis.

Abnormal dendritic cell differentiation and accumulation of immunosuppressive myeloid cells in cancer is one of the major factors of tumor nonresponsiveness. We have previously shown that hyperactivation of the Janus-activated kinase 2/signal transducers and activators of transcription 3 (JAK2/STAT3) induced by tumor-derived factors (TDF) is responsible for abnormal dendritic cell differentiation. Here, using a novel selective inhibitor of JAK2/STAT3 JSI-124, we investigated the possibility of pharmacologic regulation of dendritic cell differentiation in cancer. Our experiments in vitro have shown that JSI-124 overcomes the differentiation block induced by TDF and promotes the differentiation of mature dendritic cells and macrophages. JSI-124 significantly reduced the presence of immature myeloid cells in vivo and promoted accumulation of mature dendritic cells. In addition to a direct antitumor effect in several animal models, JSI-124 significantly enhanced the effect of cancer immunotherapy. This indicates that pharmacologic inhibition of the JAK2/STAT3 pathway can be an important new therapeutic strategy to enhance antitumor activity of cancer immunotherapy.

Purpose To determine the maximum-tolerated dose (MTD), toxicities, and clinical effect of tipifarnib, a farnesyltransferase (FTase) inhibitor, in patients with recurrent malignant glioma taking enzyme-inducing antiepileptic drugs (EIAEDs). This study compares the pharmacokinetics and pharmacodynamics of tipifarnib at MTD in patients on and off EIAEDs. Patients and Methods Recurrent malignant glioma patients were treated with tipifarnib using an interpatient dose-escalation scheme. Pharmacokinetics and pharmacodynamics were assessed. Results Twenty-three assessable patients taking EIAEDs received tipifarnib in escalating doses from 300 to 700 mg bid for 21 of 28 days. The dose-limiting toxicity was rash, and the MTD was 600 mg bid. There were significant differences in pharmacokinetic parameters at 300 mg bid between patients on and not on EIAEDs. When patients on EIAEDs and not on EIAEDs were treated at MTD (600 and 300 mg bid, respectively), the area under the plasma concentration–time curve (AUC)0-12 hours was approximately two-fold lower in patients on EIAEDs. Farnesyltransferase inhibition was noted at all tipifarnib dose levels, as measured in peripheral-blood mononuclear cells (PBMC). Conclusion Toxicities and pharmacokinetics differ significantly when comparing patients on or off EIAEDs. EIAEDs significantly decreased the maximum concentration, AUC0-12 hours, and predose trough concentrations of tipifarnib. Even in the presence of EIAEDs, the levels of tipifarnib were still sufficient to potently inhibit FTase activity in patient PBMCs. The relevance of these important findings to clinical activity will be determined in ongoing studies with larger numbers of patients.

We describe a general method for the mimicry of one face of an alpha-helix based on a terphenyl scaffold that spatially projects functionality in a manner similar to that of two turns of an alpha-helix. The synthetic scaffold reduces the flexibility and molecular weight of the mimicked protein secondary structure. We have applied this design to the development of antagonists of the alpha-helix binding protein Bcl-x(L). Using a sequential synthetic strategy, we have prepared a library of terphenyl derivatives to mimic the helical region of the Bak BH3 domain that binds Bcl-x(L). Fluorescence polarization assays were carried out to evaluate the ability of terphenyl derivatives to displace the Bcl-x(L)-bound Bak peptide. Terphenyl 14 exhibited good in vitro affinity with a K(i) value of 0.114 muM. These terphenyl derivatives were more selective at disrupting the Bcl-x(L)/Bak over the HDM2/p53 interaction, which involves binding of the N-terminal alpha-helix of p53 to HDM2. Structural studies using NMR spectroscopy and computer-aided docking simulations suggested that the helix binding area on the surface of Bcl-x(L) is the target for the synthetic ligands. Treatment of human embryonic kidney 293 (HEK293) cells with terphenyl derivatives resulted in the disruption of the binding of Bcl-x(L) to Bax in intact cells.

Overexpression or hyperactivation of MDM2 contributes to functional inactivation of wild-type p53 in nearly 50% of tumors. Inhibition of p53 by MDM2 depends on binding between an NH2-terminal (residues 16–28) p53 α-helical peptide and a hydrophobic pocket on MDM2, presenting an attractive target for development of inhibitors against tumors expressing wild-type p53. Here we report that novel p53 α-helical peptide mimics based on a terphenyl scaffold can inhibit MDM2-p53 binding in vitro and activate p53 in vivo. Several active compounds have been identified that inhibit MDM2-p53 binding in an ELISA assay with IC50 of 10 to 20 μmol/L and induce p53 accumulation and activation in cell culture at 15 to 40 μmol/L. These results suggest that p53 α-helical mimetics based on the terphenyl scaffold may be developed into potent p53 activators.

A series of Bcl-x(L)/Bak antagonists, based on a terephthalamide scaffold, was designed to mimic the alpha-helical region of the Bak peptide. These molecules showed favorable in vitro activities in disrupting the Bcl-x(L)/Bak BH3 domain complex (terephthalamides 9 and 26, K(i) = 0.78 +/- 0.07 and 1.85 +/- 0.32 microM, respectively). Extensive structure-affinity studies demonstrated a correlation between the ability of terephthalamide derivatives to disrupt Bcl-x(L)/Bak complex formation and the size of variable side chains on these molecules. Treatment of human HEK293 cells with the terephthalamide derivative 26 resulted in disruption of the Bcl-x(L)/Bax interaction in whole cells with an IC(50) of 35.0 microM. Computational docking simulations and NMR experiments suggested that the binding cleft for the BH3 domain of the Bak peptide on the surface of Bcl-x(L) is the target area for these synthetic inhibitors.

RhoA and RhoB share 86% amino acid sequence identity, yet RhoA promotes whereas RhoB suppresses malignant transformation. Amino acids 29, 100, 116, 123, 129, 140-143, 141, 146, 152, 154, 155, 173, 181, 183-187, 189, 190, 191, 192, and 193 in RhoB were mutated to the corresponding RhoA residues to determine those critical for RhoB tumor-suppressive activity. Of all the mutants made, only the cysteine 192 (one of two palmitoylation sites) and cysteine 193 (the prenylation site) point mutations abolish RhoB functions. In contrast, mutation of the other palmitoylation site, cysteine 189, did not affect RhoB functions. Moving cysteine 192 to position 190 did not affect RhoB function either. Mutation of cysteine 192 to glycine, alanine, or serine blocks the ability of RhoB to suppress transforming growth factor beta type II receptor, p2lwaf, and AP-1 promoter transcriptional activities. Furthermore, mutations of cysteines 192 and 193, but not 189, mislocalize RhoB and prevent RhoB from inhibiting anchorage-dependent and anchorage-independent tumor growth and colony formation as well as prevent it from inducing apoptosis. The cysteine 192 RhoB mutant is farnesylated and geranylgeranylated as efficiently as wild type RhoB. A RhoA-(1-180)/RhoB-(181-196) chimera inhibited tumor cell proliferation and induced apoptosis as efficiently as RhoB. These results demonstrate that the presence of neither cysteine 193 nor cysteine 192 alone is sufficient and that both palmitoylated cysteine 192 and prenylated cysteine 193, but not palmitoylated cysteine 189, are required for RhoB tumor-suppressive and proapoptotic activities.

Several D-ribonucleosides are prepared from 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranoside and trimethylsilylated nucleobases under mild conditions by using natural phosphate doped with KI as catalyst.

Chronic NK lymphoproliferative disease of large granular lymphocytes (LDGL) is characterized by the expansion of activated CD3-, CD16+ or CD56+ lymphocytes. The mechanism of survival of NK cells from LDGL patients is unknown but may be related to antigenic stimulation. There is currently no standard effective therapy for LDGL, and the disease is characteristically resistant to standard forms of chemotherapy. We found evidence of constitutive activation of extracellular-regulated kinase (ERK) in NK cells from 13/13 patients with NK-LDGL (one patient with aggressive and 12 patients with chronic disease). Ablation of ERK activity by inhibitors or a dominant-negative form of MEK, the upstream activator of ERK, reduced the survival of patient NK cells. Ras was also constitutively active in patient NK cells, and exposure of cells to the Ras inhibitor FTI2153 or to dominant-negative-Ras resulted not only in ERK inhibition but also in enhanced apoptosis in both the presence and absence of anti-Fas. Therefore, we conclude that a constitutively active Ras/MEK/ERK pathway contributes to the accumulation of NK cells in patients with NK-LDGL. These findings suggest that strategies to inhibit this signaling pathway may be useful for the treatment of the NK type of LDGL.

A series of novel protein geranylgeranyltransferase-I (PGGTase-I) inhibitors based on a benzoyleneurea scaffold has been synthesized. Using a benzoyleneurea scaffold as a mimetic for the central dipeptide (AA), we have developed CAAX peptidomimetic inhibitors that selectively block the activity of PGGTase-I over the closely related enzyme protein farnesyltransferase. In this new class of PGGTase-I inhibitors, compound (6c) with X=L-phenylalanine, displayed the highest inhibition activity against PGGTase-I with an IC50 value of 170 nM. The inhibitors described in this study represent novel and promising leads for the development of potent and selective inhibitors of mammalian PGGTase-I for potential application as antitumor agents.

We have previously reported that the statin mevastatin (compactin) reversibly inhibits the fusion of TRAP-positive mononuclear preosteoclasts (pOCs) into multinucleated osteoclasts and disrupts the actin ring in mature osteoclasts through the inhibition of protein prenylation. Protein geranylgeranylation, specifically, is known to be required for pOC fusion and for the function and survival of mature osteoclasts. However, it has not been determined whether protein geranylgeranylation is involved in early differentiation of osteoclasts (pOC formation). The current study shows that statins and the geranylgeranyl transferase I inhibitor GGTI-2166 inhibit the pOC formation induced by RANKL or TNF-alpha in cultures of both mouse marrow-derived macrophage-colony-stimulating factor (M-CSF) dependent monocytes (MD cells) and the mouse monocyte cell line RAW 264.7 (RAW cells). Mevastatin, 0.1-0.6 microM, inhibited the formation of pOCs induced by receptor activator of nuclear factor-kappaB ligand (RANKL) or tumor necrosis factor (TNF-alpha) in both cell cultures. The inhibitory effects of mevastatin were overcome by the addition of mevalonate, farnesyl pyrophosphate or geranylgeranyl pyrophosphate. GGTI-2166 inhibited TRAP activity induced by RANKL or TNF-alpha in both cell cultures and prevented the incorporation of [3H]all-trans geranylgeraniol into prenylated proteins in RAW cells. However, the farnesyl transferase inhibitor FTI-2153 did not inhibit TRAP activity although FTI prevented the incorporation of [14C]mevalonate into farnesylated proteins in RAW cells. Clostridium difficile cytotoxin B (toxin B) inhibited pOC formation induced by RANKL or TNF-alpha in both cell cultures. The inhibitory effects of statins and GGTI-2166 on pOC formation may result from the inhibition of the geranylgeranylation of G-proteins, such as Rho or Rac, suggesting that the geranylgeranylation of these proteins is involved in the early differentiation of progenitor cells into pOCs.

Purpose: RhoB is a low molecular weight GTPase belonging to the Ras protein superfamily. Whereas most Rho proteins have been shown to have a positive role in proliferation and malignant transformation, the specific role of RhoB appears more divergent. We reported previously that RhoB inhibits cell proliferation in various human cancer cells. Here, we studied the specific role played by RhoB in human lung cancer. Experimental Design: We analyzed the expression of RhoB protein by immunostaining in human lung tissues ranging from normal to invasive carcinoma from different histological types in two large independent studies of, respectively, 94 and 45 samples. We then studied the cellular effect of RhoB overexpression in a model of lung cancer (A549, adenocarcinoma) and tumorigenicity in nude mice. Results: We showed in both studies that RhoB protein was expressed in normal lung and decreased dramatically through lung cancer progression (P < 0.01). Interestingly, RhoB expression was lost in 96% of invasive tumors and reduced by 86% in poorly differentiated tumors compared with the nonneoplastic epithelium. Moreover, the loss of expression of RhoB correlated significantly with tumor stage and proliferative index, whereas no correlation was found between RhoB and p53 or Bcl-2 expression. We then showed that ectopic expression of RhoB in lung cancer cell line A549 suppressed cell proliferation, anchorage-independent growth, and xenograft tumor growth in nude mice. Conclusions: RhoB loss of expression occurs very frequently in lung carcinogenesis, reinforcing its putative tumor suppressive activity, and raising the value of its potential use in cancer therapy.

The farnesyltransferase inhibitors (FTIs) were designed to inhibit the post-translational processing of Ras proteins, which are mutated in 30% of all human cancers. Recent studies suggest, however, that the target of FTIs may be a protein other than Ras, and that these agents may be more appropriately used to treat tumors with activated wild-type ras signaling. Preliminary results from several phase II and phase III studies have been reported. The FTIs fail to show significant single-agent activity in non-small cell lung cancer, small cell lung cancer, pancreatic cancer, refractory colorectal cancer, and bladder cancer. Activity has been shown in hematologic malignancies (acute myeloid leukemia, chronic myeloid leukemia, myelodysplastic syndrome), breast cancer, and glioma. Several combination studies of FTIs and standard cytotoxic agents are ongoing.

Geranylgeranyltransferase I inhibitors (GGTIs) represent a new class of anticancer drugs. However, the mechanism by which GGTIs inhibit tumor cell growth is still unclear. Here, we demonstrate that GGTI-298 and GGTI-2166 induce apoptosis in both cisplatin-sensitive and -resistant human ovarian epithelial cancer cells by inhibition of PI3K/AKT and survivin pathways. Following GGTI-298 or GGTI-2166 treatment, kinase levels of PI3K and AKT were decreased and survivin expression was significantly reduced. Ectopic expression of constitutively active AKT2 and/or survivin significantly rescue human cancer cells from GGTI-298-induced apoptosis. Previous studies have shown that Akt mediates growth factor-induced survivin, whereas p53 inhibits survivin expression. However, constitutively active AKT2 failed to rescue the GGTIs downregulation of survivin. Further, GGTIs suppress survivin expression and induce programmed cell death in both wild-type p53 and p53-deficient ovarian cancer cell lines. These data indicate that GGTI-298 and GGTI-2166 induce apoptosis by targeting PI3K/AKT and survivin parallel pathways independent of p53. Owing to the fact that upregulation of Akt and survivin as well as inactivation of p53 are frequently associated with chemoresistance, GGTIs could be valuable agents to overcome antitumor drug resistance.

While some low molecular weight GTPases such as Ras and RhoA contribute to malignant transformation, a closely related family member, RhoB, has tumor-suppressive activity, but little is known about its regulation by oncogenes. In this study, we show that H-Ras, N-Ras, K-Ras, EGFR and ErbB2 but not v-Src suppress RhoB promoter transcriptional activity in NIH3T3 cells and human cancer cell lines derived from lung (A-549), pancreatic (Panc-1) and cervical (C33A) tumors. The EGFR and ErbB2 suppression of RhoB promoter activity is mediated by Ras. Furthermore, Ras suppresses basal as well as 5-fluorouracil (5-FU)-induced RhoB promoter activity and RhoB protein levels. Ectopic expression of RhoB, but not the closely related family member RhoA, antagonizes the ability of EGFR, ErbB2, H-Ras, N-Ras and K-Ras but not v-Src to transform NIH3T3 cells. Furthermore, RhoB, but not RhoA, inhibits colony formation and proliferation and induces anoikis in A-549 cells and Ras-transformed NIH3T3 cells. Finally, Ras-mediated resistance to 5-FU-induced apoptosis is reversed by RhoB. These results demonstrate that RhoB expression is negatively regulated by oncogenes that are prevalent in human cancers, and that ectopic expression of RhoB antagonizes the ability of these oncogenes to induce transformation. Taken together the data suggest that certain oncogenes suppress RhoB as one of the critical steps leading to malignant transformation.

R115777 is a potent farnesyltransferase (FTase) inhibitor with substantial antitumor activity in preclinical models. We conducted a phase 1 study (3 + 3 design) of R115777 in patients with myelodysplastic syndrome (MDS). R115777 was administered twice daily (3-weeks-on/1-week-off schedule for 8 weeks) (starting dosage, 300 mg by mouth twice daily; total, 600 mg). Maintenance therapy at the dose/schedule tolerated during induction could be continued until toxicity or lack of benefit. Twenty-one patients with MDS were treated (median age, 66 years). Four (19%) patients had ras mutations (n-ras,3; k-ras, 1). Objective responses (hematologic improvement, 3; partial remission, 2; or complete remission, 1) were seen in 6 of 20 (30%) evaluable patients, only 2 of whom had ras mutations. Response sequences were unusual in some patients who had increases in platelet counts without intervening aplasia. Other responders demonstrated an initial, albeit modest, myelosuppressive effect. The maximum tolerated dose was 400 mg by mouth twice a day. The most frequent side effect was myelosuppression. Dose-limiting toxicities (fatigue and confusion) occurred at 900 mg by mouth total daily dose. R115777 inhibited HDJ-2 prenylation and suppressed the activity of FTase, but not of the related geranylgeranyltransferase I enzyme, in peripheral blood mononuclear cells. Modulation of Akt, Erk, and signal transducer and activator of transcription 3 (STAT3) phosphorylation was variable, and responses occurred even without their down-regulation. Reductions in serum tumor necrosis factor-α (TNF-α) levels by day 7 showed a trend toward correlation with response (P = .09). We conclude that, at doses that are well tolerated, R115777 markedly inhibits the FTase target and has antitumor activity in MDS. (Blood. 2003;102:4527-4534)

Hepatitis delta virus (HDV) can dramatically worsen liver disease in patients coinfected with hepatitis B virus (HBV). No effective medical therapy exists for HDV. The HDV envelope requires HBV surface antigen proteins provided by HBV. Once inside a cell, however, HDV can replicate its genome in the absence of any HBV gene products. In vitro, HDV virion assembly is critically dependent on prenyl lipid modification, or prenylation, of its nucleocapsid-like protein large delta antigen. To overcome limitations of current animal models and to test the hypothesis that pharmacologic prenylation inhibition can prevent the production of HDV virions in vivo, we established a convenient mouse-based model of HDV infection capable of yielding viremia. Such mice were then treated with the prenylation inhibitors FTI-277 and FTI-2153. Both agents were highly effective at clearing HDV viremia. As expected, HDV inhibition exhibited duration-of-treatment dependence. These results provide the first preclinical data supporting the in vivo efficacy of prenylation inhibition as a novel antiviral therapy with potential application to HDV and a wide variety of other viruses.

Activation of estrogen receptors (ERs) by estrogens triggers both ER nuclear transcriptional activity and Src/Ras/Erks pathway-dependent mitogenic activity. The present study implicates prenylated proteins in both estrogenic actions. The farnesyltransferase and geranylgeranyltransferase I inhibitors (FTI-277 and GGTI-298, respectively) antagonize estradiol-stimulated cell cycle progression, progesterone receptor, cyclin D1, and c-Myc expression. In contrast, the inhibitors markedly stimulate transcription from two genes containing estrogen response elements, both in the absence and presence of estradiol. The pure antiestrogen ICI 182,780 inhibits by more than 85% these effects on transcription. We demonstrate that both FTI-277 and GGTI-298 increase the association of steroid receptor coactivator-1 with ER alpha and FTI-277 decreases the association of ER alpha with the histone deacetylase 1, a known transcriptional repressor. In addition, FTI-277 has no marked effect on the association of the two corepressors, nuclear receptor corepressor and silencing mediator of retinoid and thyroid receptor with ER alpha, whereas GGTI-298, similar to tamoxifen, clearly increased these associations. Together, these results demonstrate that prenylated proteins play a role in estradiol stimulation of proliferation and progesterone receptor expression. However, they antagonize the ability of ER alpha to stimulate estrogen response element-dependent transcriptional activity, acting presumably through coregulator complex formation.

Farnesyltransferase inhibitors (FTIs) block the growth of tumor cells in vitro and in vivo with minimal toxicity toward normal cells. In general, inhibition of protein farnesylation results in G0/G1 cell cycle block, G2/M cell cycle arrest, or has no effect on cell cycle progression. One aspect of FTI biology that is poorly understood is the ability of these drugs to induce cancer cell growth arrest at the G2/M phase of cell cycle. In the present study, we investigated the effects of the farnesyltransferase inhibitor FTI-277 on two human liver cancer cell lines, HepG2 and Huh7. Treatment of these cells with FTI-277 inhibited Ras farnesylation in a dose-dependent manner. Both HepG2 and Huh7 cell growth was inhibited by FTI-277 and cells accumulated at the G2/M phase of the cell cycle. In HepG2 and Huh7 cells, FTI-277 induced an up-regulation of the cyclin-dependent kinase inhibitor p27(Kip1) without affecting the cellular levels of p53 and p21(Waf1). This event correlated with reduced activity of the cyclin-dependent kinase 2 and cyclin-dependent kinase 1. Moreover, increased expression of Bcl-2 protein was observed in HepG2 and Huh7 cells treated with FTI-277, and this was coincidental with reduced association between Raf-1 and Bcl-2. Finally, transient transfection of a dominant-negative Ras allele induced Bcl-2 expression and reduced Bcl-2/Raf-1 association demonstrating a requirement for Ras. Taken together, these findings show that increased expression of p27(Kip1) and Bcl-2 is concomitant with altered association between Ras, Raf-1 and Bcl-2 and suggest that this is responsible for the growth-inhibitory properties of FTI-277.

In contrast to Ras small GTPases, which contribute to human malignancy when overexpressed or constitutively activated, convincing evidence for the involvement of Ras homologous (Rho) GTPases in human cancer is still missing. In cell culture and animal models, RhoB antagonizes malignant transformation, but no data are available regarding the expression of RhoB in human tumors. In this study, we have analyzed the status of the RhoB protein and the closely related family member RhoA in human head and neck squamous cell carcinomas.Protein immunoexpression was quantitated by image analysis in the context of tumor invasion and differentiation. To account for possible individual variations, expression levels of RhoB and RhoA were evaluated in the tumor and its adjacent nonneoplastic tissue. Potential gene deletions or mutations were assessed by PCR and RT-PCR.RhoB expression is readily detected in normal epithelium, carcinomas in situ, and well-differentiated tumors, but it becomes weak to undetectable as tumors become deeply invasive and poorly differentiated. In contrast, Ki67 (proliferation marker) and RhoA protein levels increase with tumor progression. Furthermore, whereas in nonneoplastic keratinocytes RhoB is localized mainly in the nucleus, in carcinomas RhoB is predominantly located in the cytoplasm. RhoB gene deletions or mutations were not found.These results give additional support to the notion that RhoB may play a tumor suppressive role in squamous cell carcinomas of the head and neck. The lack of RhoB expression in deeply invasive carcinoma argues against inhibition of RhoB farnesylation as a mediator of farnesyltransferase inhibitors' antitumor activity.

Events that contribute to tumor formation include mutations in the ras gene and loss or inactivation of cell cycle inhibitors such as p21(Cip1) and p27(Kip1). In our previous publication, we showed that mice expressing the MMTV/v-Ha-ras transgene developed tumors earlier and at higher multiplicities in the absence than in the presence of p21(Cip1). To further evaluate the combinatorial role of genetic alterations and loss of cell cycle inhibitors in tumorigenesis, we performed two companion studies. In the first study, wild type and p21(Cip1)-null mice were exposed to the chemical carcinogen, urethane. Similar to its effects in v-Ha-ras mice, loss of p21(Cip1) accelerated tumor onset and increased tumor multiplicity in urethane-treated mice. Lung tumors were the predominant tumor type in urethane-treated mice regardless of p21(Cip1) status. In the second study, tumor formation was monitored in v-Ha-ras mice expressing or lacking p27(Kip1). Unlike p21(Cip1), the absence of p27(Kip1) had no effect on the timing or multiplicity of tumor formation, which was largely restricted to mammary and salivary glands. However, once tumors appeared, they grew faster in p27(Kip1)-null mice than in p27(Kip1)-wild type mice. Increases in growth rate were particularly striking for salivary tumors in ras/p27(-/-) mice. Loss of p21(Cip1), on the other hand, had no effect on tumor growth rate in v-Ha-ras mice. Collectively, our data suggest that p21(Cip1) suppresses tumor formation elicited by multiple agents and that p21(Cip1) and p27(Kip1) suppress tumor formation in different ways.

This paper describes recent progress in the design, synthesis and biological evaluation of inhibitors for the enzyme protein farnesyltransferase (PFTase). This enzyme plays a critical role in the post-translational modification of a range of different intracellular proteins. In particular, PFTase attaches a farnesyl group to the GTPase Ras whose oncogenically mutated form is found in over 30% of human cancers. As a result PFTase inhibitors have been developed as potential cancer therapeutic drugs either by rational design based on the structure of the CAAX carboxyl terminus of Ras or random screening of chemical libraries or natural products. Some of these inhibitors show remarkable inhibition potency against PFTase at subnanomolar concentrations and > 1000-fold selectivity compared to the related enzyme geranylgeranyltransferase-I. Certain of these compounds are highly effective at blocking the growth of human tumors in animal models and are now undergoing clinical trials. However, several issues in the research remain unsolved, including the mechanism by which PFTase inhibitors suppress tumor growth. Although it has been established that PFTase inhibitors block prenylation of Ras in vitro, the results in whole cells and animal studies suggest the possibility that proteins other than Ras are affected.

Geranylgeranylation of RhoA small G-protein is essential for its localization to cell membranes and for its biological functions. Many RhoA effects are mediated by its downstream effector RhoA kinase. The role of protein geranylgeranylation and the RhoA pathway in the regulation of endothelial cell survival has not been elucidated. The hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor lovastatin depletes cellular pools of geranylgeranyl pyrophosphate and farnesol pyrophosphate and thereby inhibits both geranylgeranylation and farnesylation. Human umbilical vein endothelial cells (HUVECs) were exposed to lovastatin (3 microm-30 microm) for 48 h, and cell death was quantitatively determined by cytoplasmic histone-associated DNA fragments as well as caspase-3 activity. The assays showed that lovastatin caused a dose-dependent endothelial cell death. The addition of geranylgeraniol, which restores geranylgeranylation, rescued HUVEC from apoptosis. The geranylgeranyltransferase inhibitor GGTI-298, but not the farnesyltransferase inhibitor FTI-277, induced apoptosis in HUVEC. Cell death was also induced by a blockade of RhoA function by exoenzyme C3. In addition, treatment of HUVEC with the RhoA kinase inhibitors Y-27632 and HA-1077 caused dose-dependent cell death. Y-27632 did not inhibit other well known survival pathways, such as NF-kappa B, ERK, and phosphatidylinositol 3-kinase/Akt. However, there was an increase in p53 protein level concomitant with Y-27632-induced cell death. Unlike the apoptosis induced by TNF-alpha, which occurs only with inhibition of new protein synthesis, apoptosis induced by inhibitors of HMG-CoA reductase, geranylgeranyltransferase, or RhoA kinase was blocked by cycloheximide. Our data indicate that inhibition of protein geranylgeranylation and RhoA pathways induce apoptosis in HUVEC and that induction of p53 or other proapoptotic proteins is required for this process.

STAT3 is a key mediator of inflammation, and is associated with murine auto- and alloreactivity. Germline and somatic activating STAT3 mutations have correlated with human inflammatory disorders, including colitis and polyendocrinopathy. STAT3 phosphorylation is required for pathogenic Th17 differentiation, and antagonizes beneficial Treg development. We show that CD4+ T-cell STAT3 activity is elevated early after allogeneic hematopoietic cell transplantation (HCT) compared with healthy non-HCT controls, and identifies patients at risk of developing grade II-IV acute graft-versus-host disease (GVHD) before the onset of symptoms. Using human in vitro and murine in vivo systems, we demonstrate that STAT3 phosphorylation may be selectively targeted with S3I-201 to suppress the alloresponse while preserving graft-versus-leukemia (GVL). Peripheral blood T-cells were obtained on day +21 from consented HCT recipients lacking any signs of acute GVHD (n=5 non-HCT controls, n=18 HCTs). T-cell STAT3 Y705 activity was stimulated with a pulse of IL-6 (4000 IU/ml, 15 minutes) and measured by flow cytometry. Patients were followed for acute GVHD onset from day +22 to day +100. While resting STAT3 activity was very low in all groups, stimulated CD4+ STAT3 phosphorylation significantly increased among the patients that later developed acute GVHD during the observation period (Fig 1 A: non-HCT control: 8.83%; n=10 grade 0-I: 28.8%; n=8 grade II-IV: 67.6% median pSTAT3+/CD4+; P Disclosures No relevant conflicts of interest to declare.

Inhibition of mutant H-Ras farnesylation with farnesyltransferase inhibitors (FTIs) blocks its binding to membranes and its ability to activate oncogenic signaling. In contrast, inhibition of K-Ras farnesylation with FTIs leads to its prenylation by geranylgeranyltransferase I (GGT-1), and therefore, inhibition of K-Ras prenylation and oncogenic function requires blocking both FT and GGT-1. Furthermore, several proteins downstream of K-Ras that mediate its malignant transforming activity also require farnesylation (e.g.Rheb) or gernaylgeranylation (e.g. Ral). In addition, the ability of mutant K-Ras to induce lung cancer in mouse models is severely hampered when both FT and GGT-1 are conditionally deficient. These observations prompted us to design small molecule dual FT and GGT-1 inhibitors. In this presentation, the development of FGTI-2734 as a novel therapeutic for K-Ras dependent cancers will be described. The presentation will focus on the effect of this dual inhibitor as compared to the selective FTI-2148 and GGTI-2418 on K-ras prenylation, oncogenic signaling and malignant transformation in cancer cells that depend on K-Ras. Citation Format: Kazi Aslamuzzaman, Xiaolei Zhang, Yunting Luo, Ronil Patel, Steven Fletcher, Christopher Cummings, Harshani Lawrence, Andrew Hamilton, Said M. Sebti. Dual inhibitors of FT and GGT-1 as novel therapeutic agents for K-Ras-dependent tumors. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B35. doi: 10.1158/1557-3125.RASONC14-B35

Our ongoing efforts to validate kinases for cancer therapy led to the novel finding that ectopic expression of JAK2 and Aurora A together is more effective than each alone at inducing normal cells to grow in an anchorage-independent manner and to invade. In addition, siRNA silencing or pharmacological inhibition of JAK2 and Aurora A with Ruxolitinib and Alisertib, respectively, is more effective than blocking each kinase alone at suppressing anchorage-dependent and -independent growth and invasion as well as at inducing apoptosis. This led us to develop dual Aurora and JAK inhibitors, AJI-214 and AJI-100, which potently inhibit the activities of Aurora A, Aurora B and JAK2 in vitro. In human cancer cells, these dual inhibitors block the auto-phosphorylation of Aurora A (Thr-288) and the phosphorylation of the Aurora B substrate histone H3 (Ser-10) and the JAK2 substrate STAT3 (Tyr-705). Furthermore, AJI-214 and AJI-100 inhibit anchorage dependent and independent cell growth and invasion and induce G2/M cell cycle accumulation and apoptosis. Finally, the more soluble AJI-100 was effective at inducing tumor regression of human xenografts in mice. Taken together, our genetic and pharmacological studies indicate that targeting Aurora A and JAK2 together is a more effective approach than each alone at inhibiting malignant transformation and warrant further advanced pre clinical investigations of dual Aurora A/JAK2 inhibitors as potential anti tumor agents. Citation Format: Said M. Sebti, Hua Yang, Harshani Lawrence, Aslamuzzaman Kazi, Harsukh Gervaria, Ronil Patel, Yunting Luo, Uwe Rix, Ernst Schonbrunn, Nicholas Lawrence. Combined blockade of Aurora A and JAK2 kinase is highly effective at inhibiting malignant transformation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1750. doi:10.1158/1538-7445.AM2014-1750

The ability of Akt 2 and acid ceramidase (ASAH1) to cooperate and induce malignant transformation is not known. Here we show that in immortalized, non-transformed cells, ectopic co-expression of Akt2 and ASAH1 is significantly more effective than expression of each gene alone at inducing cell invasion and at conferring resistance to apoptosis. Consistent with these observations, siRNA-mediated depletion of both Akt2 and ASAH1 is much more potent than depleting each alone at inhibiting cell viability/proliferation and cell invasion. Furthermore, pharmacological inhibitors of Akt (TCN or MK-2206) and ASAH1 (B13) synergize to inhibit cell viability/proliferation, and combinations of these drugs are more effective than single agent treatments at inhibiting cell invasion. Taken together, the results suggest that these two enzymes cooperate to induce malignant transformation and warrant further preclinical studies to evaluate the potential of combining inhibitors of Akt and ASAH1 to treat cancer. Citation Format: Said M. Sebti, Norbert Berndt, Ronil Patel, Hua Yang, Maria Balasis. Akt2 and acid ceramidase cooperate to induce malignant transformation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4522. doi:10.1158/1538-7445.AM2014-4522

The binding of STAT3 and STAT5 to growth factor and cytokine receptors such as EGFR and the IL-6 receptor gp130 is critical to their activation and ability to contribute to malignant transformation. Therefore, interfering with these biochemical processes could lead to the discovery of novel anti-cancer agents. In this manuscript, we show that the natural product, Withacnistin (Wit) blocks EGF- and IL-6-stimulated binding of STAT3 and STAT5 to EGFR and gp130. Furthermore, Wit inhibits EGF-, PDGF-, IL-6-, IFNβ- and GM-CSF-stimulation of tyrosine phosphorylation of STAT3 and STAT5 but not of EGFR or PDGFR. The inhibition of P-STAT3 and P-STAT5 occurred very rapidly, within minutes of Wit treatment and growth factor stimulation. Wit also inhibits STAT3 nuclear translocation, DNA binding, promoter transcriptional activation, and it suppresses the expression levels of STAT3 target genes such as Bcl-xL and Mcl-1. Finally, Wit induces apoptosis, inhibits anchorage-independent growth and invasion, and causes breast tumor regression in an ErbB2-driven transgenic mouse model. These data warrant further development of Wit as a novel anti-cancer drug for targeting tumors that harbor hyperactivated STAT3 and STAT5. Citation Format: Xiaolei Zhang, Michelle A. Blaskovich, Kara D. Forinash, Said M. Sebti. Withacnistin blocks binding of STAT3 and STAT5 to growth factor and cytokine receptors and induces regression of breast tumors in vivo. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3802. doi:10.1158/1538-7445.AM2014-3802