Identification and characterization of a novel integrin-linked kinase inhibitor

Integrin-linked kinase (ILK) represents a relevant target for cancer therapy in light of its role in promoting oncogenesis and tumor progression. Through the screening of an in-house focused compound library, we identified N-methyl-3-(1-(4-(piperazin-1-yl)phenyl)-5-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-3-yl)propanamide (22) as a novel ILK inhibitor (IC(50), 0.6 μM), which exhibited high in vitro potency against a panel of prostate and breast cancer cell lines (IC(50), 1-2.5 μM), while normal epithelial cells were unaffected. Compound 22 facilitated the dephosphorylation of Akt at Ser-473 and other ILK targets, including glycogen synthase kinase-3β and myosin light chain. Moreover, 22 suppressed the expression of the transcription/translation factor YB-1 and its targets HER2 and EGFR in PC-3 cells, which could be rescued by the stable expression of constitutively active ILK. Evidence indicates that 22 induced autophagy and apoptosis, both of which were integral to its antiproliferative activity. Together, this broad spectrum of mechanisms underlies the therapeutic potential of 22 in cancer treatment, which is manifested by its in vivo efficacy as a single oral agent in suppressing PC-3 xenograft tumor growth.

Liposomes containing (-)-gossypol-enriched cottonseed oil suppress Bcl-2 and Bcl-xL expression in breast cancer cells

PURPOSE

We have demonstrated that (-)-gossypol-enriched cottonseed oil [(-)-GPCSO] can down-regulate Bcl-2 expression in MCF-7 and primary cultured human breast cancer epithelial cells (PCHBCECs). However, this agent has not been evaluated in vivo due to its limited solubility. We aimed to develop liposomes containing (-)-GPCSO to suppress Bcl-2/Bcl-xL expression.

METHODS

(-)-GPCSO liposomes were prepared and evaluated for effects on breast cancer cell viability, MDA-MB-231 xenograft tumor growth, cellular Bcl-2 and Bcl-xL mRNA levels, and chemosensitivity to paclitaxel.

RESULTS

(-)-GPCSO liposomes prepared had excellent stability. Cytotoxicity of (-)-GPCSO liposomes was significantly reduced compared to (-)-GPCSO in culture medium. Bcl-2 and Bcl-xL mRNA expression was down-regulated by (-)-GPCSO in culture medium or (-)-GPCSO liposomes in MDA-MB-231 cells. In PCHBCECs, Bcl-2 and Bcl-xL expression were down-regulated by (-)-GPCSO liposomes. (-)-GPCSO in culture medium induced only a mild reduction in Bcl-xL. In the MDA-MB-231 xenograft tumor model, (-)-GPCSO liposomes exhibited tumor-suppressive activity and significantly reduced intratumoral Bcl-2 and Bcl-xL expression. Cytotoxicity of paclitaxel was increased by pretreatment with (-)-GPCSO liposomes in MDA-MB-231 and PCHBCECs.

CONCLUSIONS

Findings suggest that (-)-GPCSO liposomes warrant continued investigation as a chemosensitizer for breast cancers exhibiting Bcl-2-/Bcl-xL-mediated drug resistance.

Antitumor effects of OSU-2S, a nonimmunosuppressive analogue of FTY720, in hepatocellular carcinoma

Accumulating evidence suggests the therapeutic potential of the immunosuppressive agent FTY720 (fingolimod) in hepatocellular carcinoma (HCC). Based on our previous finding that FTY720 mediates apoptosis in HCC cells by activating reactive oxygen species (ROS)-protein kinase Cδ (PKCδ) signaling independent of effects on sphingosine-1-phosphate (S1P) receptors, we embarked on the pharmacological exploitation of FTY720 to develop a nonimmunosuppressive analogue with antitumor activity. This effort led to the development of OSU-2S, which exhibits higher potency than FTY720 in suppressing HCC cell growth through PKCδ activation. In contrast to FTY720, OSU-2S was not phosphorylated by sphingosine kinase 2 (SphK2) in vitro, and did not cause S1P1 receptor internalization in HCC cells or T lymphocyte homing in immunocompetent mice. Although devoid of S1P1 receptor activity, OSU-2S exhibited higher in vitro antiproliferative efficacy relative to FTY720 against HCC cells without cytotoxicity in normal hepatocytes. Several lines of pharmacological and molecular genetic evidence indicate that ROS-PKCδ-caspase-3 signaling underlies OSU-2S-mediated antitumor effects, and that differences in the antitumor activity between FTY720 and OSU-2S were attributable to SphK2-mediated phosphorylation of FTY720, which represents a metabolic inactivation of its antitumor activity. Finally, OSU-2S exhibited high in vivo potency in suppressing xenograft tumor growth in both ectopic and orthotopic models without overt toxicity.

CONCLUSION

Using the molecular platform of FTY720, we developed OSU-2S, a novel PKCδ-targeted antitumor agent, which is devoid of S1P1 receptor activity and is highly effective in suppressing HCC tumor growth in vivo. These findings suggest that OSU-2S has clinical value in therapeutic strategies for HCC and warrants continued investigation in this regard.

Abstract 3505: Energy restriction-mimetic agents (ERMAs) decrease BRCA1 expression levels in triple-negative breast cancer cells: A rationale for combining ERMAs with poly(ADP ribose) polymerase

Purpose: Triple-negative (ER-negative, PR-negative, HER2/neu-negative) breast cancer (TNBC) is a clinical challenge because of the lack of a specific therapeutic target. Poly (ADP-ribose) polymerase (PARP)-1 is a nuclear enzyme involved in the detection and repair of DNA damage. In DNA repair-defective tumors, inhibition of PARP can cause genomic instability and cell death. Among the PARP inhibitors currently being assessed in clinical trials, recent results showed that, in a randomized phase II clinical trial of TNBC patients, BSI-201 when added to platinum-containing chemotherapy significantly improved the outcome of metastatic breast cancer patients relative to chemotherapy alone. Previously, we reported that the thiazolidinedione family of peroxisome proliferation-activated receptor-γ agonist could induce apoptosis in cancer cells by eliciting cellular responses indicative of energy restriction. Consequently, we used ciglitazone as a scaffold to develop novel energy restriction-mimetic agents (ERMAs) through structural optimization, which has yielded two lead compounds, CG-5 and CG-12. In prostate cancer cells, ERMAs could induce cell death and reduce the expression of BRCA1 protein. BRCA1 helps repair DNA double-stranded breaks through homologous recombination. BRCA1 deficiency has been reported to sensitize cells to PARP inhibition through synthetic lethality. We hypothesize that ERMAs can potentiate the anti-proliferative activity of PARP inhibitors (AZD-2281, AG-014699, ABT-888 and BSI-201) through the down-regulation of BRCA1 expression in TNBC cells.

Methods: TNBC cell lines, MDA-MB-468, MDA-MB-231 and Cal-51 (all of which have functional BRCA1) were obtained from ATCC and DSMZ and maintained in low-glucose complete growth medium. Drug effects on cell viability were assessed by MTT assays. The expression of BRCA1, phosphorylated AMP-activated kinase (AMPK), and PARP cleavage in treated cells were examined by western blotting.

Results: The ERMAs CG-5 and CG-12 exhibited dose-dependent anti-proliferative activity against all TNBC cell lines tested with IC50 values of about 3 and 4 μM, respectively, after 72 h of treatment. These anti-proliferative effects were attributed to apoptosis as both compounds induced the cleavage of PARP. Moreover, AMPK was activated by both drugs indicative of energy restriction. BRCA1 levels were reduced dose-dependently in all three TNBC cell lines after treatment with CG-5 or CG-12.

Conclusion: The ERMAs CG-5 and CG-12 can reduce BRCA1 levels in TNBC cells. These findings provide a rationale for combining the ERMA-mediated ablation of BRCA1 with PARP inhibitors to induce TNBC cell death through synthetic lethality. Further study to address this hypothesis could lead to a new therapeutic approach for TNBC patients for whom available options are limited.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3505. doi:10.1158/1538-7445.AM2011-3505

Abstract 2858: A novel mouse model for cutaneous T-cell lymphoma reveals a role for IL-15 and activity of a new oral HDAC inhibitor

Cutaneous T-cell lymphoma (CTCL) is a type of non-Hodgkin's lymphoma representing a spectrum of diseases composed of malignant clonal CD4 (+) helper T lymphocytes. The etiology of CTCL remains to be elucidated and no animal models for CTCL are known. We quantified expression of IL-15 in patients with CTCL and demonstrated aberrant overexpression of IL-15 compared to normal CD4+ T cells (Fold increase = 7.476 ± 1.788 N=3, P=0.0073), that showed direct correlation with the stage of the disease (Fold increase in IL-15 in Stage I patients vs. Stage III patients = 3.283 ± 0.8246 vs. 7.476 ± 1.788, N=3 each, P=0.02). We engineered a transgenic (tg) mouse to constitutively and globally overexpress murine IL-15. These mice develop alopecia and cutaneous lesions in all mice within 6 weeks of birth, characterized by erythematous plaques/patches, erythroderma, pruritis and early death compared to wild type (WT) controls (49 weeks vs. 100 weeks, P=0.0003). Skin lesions showed an infiltration of atypical lymphocyte in the dermis and throughout the epidermis including the formation of classic Pautrier's microabscesses as seen in human CTCL. Immunophenotypic analysis of the skin T-cells from these mice revealed ∼25 fold increase in CD3+ T-cells compared to WT littermates. Intradermal CD4+ cells from CTCL mice were predominantly CD62L- and significantly higher than WT mice (P=0.007). Immunohistochemistry showed high expression of cutaneous lymphocyte antigen (CLA) and CCR4 on skin sections of CTCL mice, consistent with a skin-specific homing pattern as seen in human CTCL. Cells obtained from the skin of these IL-15tg CTCL mice could be successfully engrafted into skin of SCID recipient mice with reproducible histological lesions. Consistent with human studies, CTCL mice exhibited significantly increased levels of Hdac-1 in CD4+ T cells when compared to their WT counterparts (P = 0.0013). To investigate the importance of IL-15 in this process, we cultured sorted mouse WT (CD3+CD4+) T-cells in medium supplemented with 100ng/ml IL-15 and observed a significant increase in Hdac-1 expression at the mRNA and protein level within 10 days of culture, compared to freshly isolated WT CD4+ T cells (N=3 each, p =0.02). In a randomized, placebo-controlled trial of an orally administered novel HDAC inhibitor, AR-42 (Arno Therapeutics, Inc, Parsippany, NJ; Sargeant AM et al, Cancer Research, 2008) to IL-15 tg mice with CTCL, we observed an improvement in skin lesions and a marked reduction in T-cell dermal infiltrate as early as 12 days post-treatment. In conclusion, we provide evidence for a reproducible in vivo mouse model of spontaneous CTCL that appears to mimic the human condition. Further, we provide evidence for a role of aberrant IL-15 expression in the genesis of both human and experimental CTCL, and alterations in Hdac-1 expression that may to serve as an appropriate target for a novel oral HDAC inhibitor now in clinical trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2858. doi:10.1158/1538-7445.AM2011-2858

OSU-DY7, a novel D-tyrosinol derivative, mediates cytotoxicity in chronic lymphocytic leukaemia and Burkitt lymphoma through p38 mitogen-activated protein kinase pathway

Drug resistance and associated immune deregulation limit use of current therapies in chronic lymphocytic leukaemia (CLL), thus warranting alternative therapy development. Herein we demonstrate that OSU-DY7, a novel D-tyrosinol derivative targeting p38 mitogen-activated protein kinase (MAPK), mediates cytotoxicity in lymphocytic cell lines representing CLL (MEC-1), acute lymphoblastic leukaemia (697 cells), Burkitt lymphoma (Raji and Ramos) and primary B cells from CLL patients in a dose- and time-dependent manner. The OSU-DY7-induced cytotoxicity is dependent on caspase activation, as evidenced by induction of caspase-3 activation and poly (ADP-ribose) polymerase (PARP) cleavage and rescue of cytotoxicity by Z-VAD-FMK. Interestingly, OSU-DY7-induced cytotoxicity is mediated through activation of p38 MAPK, as evidenced by increased phosphorylation of p38 MAPK and downstream target protein MAPKAPK2. Pretreatment of B-CLL cells with SB202190, a specific p38 MAPK inhibitor, results in decreased MAPKAPK2 protein level with concomitant rescue of the cells from OSU-DY7-mediated cytotoxicity. Furthermore, OSU-DY7-induced cytotoxicity is associated with down regulation of p38 MAPK target BIRC5, that is rescued at protein and mRNA levels by SB202190. This study provides evidence for a role of OSU-DY7 in p38 MAPK activation and BIRC5 down regulation associated with apoptosis in B lymphocytic cells, thus warranting development of this alternative therapy for lymphoid malignancies.

Energy restriction-mimetic agents induce apoptosis in prostate cancer cells in part through epigenetic activation of KLF6 tumor suppressor gene expression

Although energy restriction has been recognized as an important target for cancer prevention, the mechanism by which energy restriction-mimetic agents (ERMAs) mediate apoptosis remains unclear. By using a novel thiazolidinedione-derived ERMA, CG-12 (Wei, S., Kulp, S. K., and Chen, C. S. (2010) J. Biol. Chem. 285, 9780-9791), vis-à-vis 2-deoxyglucose and glucose deprivation, we obtain evidence that epigenetic activation of the tumor suppressor gene Kruppel-like factor 6 (KLF6) plays a role in ERMA-induced apoptosis in LNCaP prostate cancer cells. KLF6 regulates the expression of many proapoptotic genes, and shRNA-mediated KLF6 knockdown abrogated the ability of ERMAs to induce apoptosis. Chromatin immunoprecipitation analysis indicates that this KLF6 transcriptional activation was associated with increased histone H3 acetylation and histone H3 lysine 4 trimethylation occupancy at the promoter region. Several lines of evidence demonstrate that the enhancing effect of ERMAs on these active histone marks was mediated through transcriptional repression of histone deacetylases and H3 lysine 4 demethylases by down-regulating Sp1 expression. First, putative Sp1-binding elements are present in the promoters of the affected histone-modifying enzymes, and luciferase reporter assays indicate that site-directed mutagenesis of these Sp1 binding sites significantly diminished the promoter activities. Second, shRNA-mediated knockdown of Sp1 mimicked the repressive effect of energy restriction on these histone-modifying enzymes. Third, ectopic Sp1 expression protected cells from the repressive effect of CG-12 on these histone-modifying enzymes, thereby abolishing the activation of KLF6 expression. Together, these findings underscore the intricate relationship between energy restriction and epigenetic regulation of tumor suppressor gene expression, which has therapeutic relevance to foster novel strategies for prostate cancer therapy.

Novel mechanism by which histone deacetylase inhibitors facilitate topoisomerase IIα degradation in hepatocellular carcinoma cells

Histone deacetylase (HDAC) inhibitors exhibit a unique ability to degrade topoisomerase (topo)IIα in hepatocellular carcinoma (HCC) cells, which contrasts with the effect of topoII-targeted drugs on topoIIβ degradation. This selective degradation might foster novel strategies for HCC treatment in light of the correlation of topoIIα overexpression with the aggressive tumor phenotype and chemoresistance. Here we report a novel pathway by which HDAC inhibitors mediate topoIIα proteolysis in HCC cells. Our data indicate that HDAC inhibitors transcriptionally activated casein kinase (CK)2α expression through increased association of acetylated histone H3 with the CK2α gene promoter. In turn, CK2 facilitated the binding of topoIIα to COP9 signalosome subunit (Csn)5 by way of topoIIα phosphorylation. Furthermore, we identified Fbw7, a Csn5-interacting F-box protein, as the E3 ligase that targeted topoIIα for degradation. Moreover, knockdown of CK2α, Csn5, or Fbw7 reversed HDAC inhibitor-induced topoIIα degradation. Mutational analysis indicates that the (1361) SPKLSNKE(1368) motif plays a crucial role in regulating topoIIα protein stability. This motif contains the consensus recognition sites for CK2 (SXXE), glycogen synthase kinase (GSK)3β (SXXXS), and Fbw7 (SPXXS). This study also reports the novel finding that topoIIα may be a target of GSK3β phosphorylation. Evidence suggests that CK2 serves as a priming kinase, through phosphorylation at Ser1365, for GSK3β-mediated phosphorylation at Ser1361. This double phosphorylation facilitated the recruitment of Fbw7 to the phospho-degron (1361) pSPKLpS(1365) of topoIIα, leading to its ubiquitin-dependent degradation.

CONCLUSION

This study shows a novel pathway by which HDAC inhibitors facilitate the selective degradation of topoIIα, which underlies the complexity of the functional role of HDAC in regulating tumorigenesis and aggressive phenotype in HCC cells.

The effect of phosphorylated Akt inhibition on posterior capsule opacification in an ex vivo canine model

PURPOSE

To evaluate whether inhibition of phosphorylated Akt (pAkt) would reduce or prevent posterior capsule opacification (PCO) in an ex vivo canine lens capsule model.

METHODS

Normal and cataractous lenses (n=6) were evaluated for pAkt via immunohistochemistry and immunoblotting. Primary cultures of lens epithelial cells (LEC) were exposed to ultraviolet light (UV) to induce pAkt. Cultures were then incubated in 0, 2.5, 5, or 10 µM (n=6) of a novel Akt inhibitor (AR-12) for either 8 or 24 h. Cultures were harvested and pAkt expression and telomerase activity examined by immunoblotting and telomeric repeat amplification protocol (TRAP)-enzyme linked immunosorbent assay (ELISA), respectively. Lens capsules were harvested post-sham cataract surgery and exposed to 0, 2.5, 5, 7.5, or 10 μM (n=8) of AR-12 for a total of 14 days treatment. Additional lens capsules (n=6) were exposed to 10 μM of AR-12 for 1 week followed by media alone for 1 week; or exposed to media alone for 1 week followed by 10 μM of AR-12 for 1 week. Histopathology and immunohistochemical staining were performed to evaluate PCO formation. Analysis of telomerase activity on the lens capsules was performed by TRAP-ELISA.

RESULTS

pAkt protein expression was increased in clinical samples of canine cataracts compared to normal lenses. Following exposure to UV, cultures of LEC significantly (p<0.05) increased expression of pAkt and telomerase activity. Treatment with AR-12 for both 8 and 24 h following UV irradiation significantly (p<0.01) decreased pAkt expression. When UV-exposed LEC were allowed to recover in the presence of either 5.0 or 10.0 µM AR-12, there was a significant (p<0.05) decrease in telomerase activity. In the ex vivo model of PCO, within the region of the capsulorhexis, PCO inhibition was maximally achieved with 10 μM of AR-12. A significant decrease in LEC was noted on the posterior capsules containing 5.0, 7.5, and 10 μM AR-12 compared to the control capsules (p<0.01). Telomerase activity decreased in a dose-dependent manner. One week of treatment with 10 μM AR-12, immediately following capsule excision, was sufficient to inhibit PCO formation, while a delay in exposure to AR-12 after 1 week of media incubation alone did not prevent PCO formation.

CONCLUSIONS

pAkt is known to have roles in cell survival, proliferation, and migration, and this study suggests its inhibition immediately following cataract surgery may be a useful approach to prevent PCO.

Histone deacetylase inhibitors stimulate histone H3 lysine 4 methylation in part via transcriptional repression of histone H3 lysine 4 demethylases

This study investigates the mechanism by which histone deacetylase (HDAC) inhibitors up-regulate histone H3 lysine 4 (H3K4) methylation. Exposure of LNCaP prostate cancer cells and the prostate tissue of transgenic adenocarcinoma of the mouse prostate mice to the pan- and class I HDAC inhibitors (S)-(+)-N-hydroxy-4-(3-methyl-2-phenyl-butyrylamino)-benzamide (AR42), N-(2-aminophenyl)-4-[N-(pyridine-3-yl-methoxycarbonyl)-aminomethyl]-benzamide (MS-275), and vorinostat led to differential increases in H3K4 methylation. Chromatin immunoprecipitation shows that this accumulation of methylated H3K4 occurred in conjunction with decreases in the amount of the H3K4 demethylase RBP2 at the promoter of genes associated with tumor suppression and differentiation, including KLF4 and E-cadherin. This finding, together with the HDAC inhibitor-induced up-regulation of KLF4 and E-cadherin, suggests that HDAC inhibitors could activate the expression of these genes through changes in histone methylation status. Evidence indicates that this up-regulation of H3K4 methylation was attributable to the suppressive effect of these HDAC inhibitors on the expression of RBP2 and other JARID1 family histone demethylases, including PLU-1, SMCX, and LSD1, via the down-regulation of Sp1 expression. Moreover, shRNA-mediated silencing of the class I HDAC isozymes 1, 2, 3, and 8, but not that of the class II isozyme HDAC6, mimicked the drug effects on H3K4 methylation and H3K4 demethylases, which could be reversed by ectopic Sp1 expression. These data suggest a cross-talk mechanism between HDACs and H3K4 demethylases via Sp1-mediated transcriptional regulation, which underlies the complexity of the functional role of HDACs in the regulation of histone modifications.

The novel deacetylase inhibitor AR-42 demonstrates pre-clinical activity in B-cell malignancies in vitro and in vivo

Background

While deacetylase (DAC) inhibitors show promise for the treatment of B-cell malignancies, those introduced to date are weak inhibitors of class I and II DACs or potent inhibitors of class I DAC only, and have shown suboptimal activity or unacceptable toxicities. We therefore investigated the novel DAC inhibitor AR-42 to determine its efficacy in B-cell malignancies.

Principal Findings

In mantle cell lymphoma (JeKo-1), Burkitt's lymphoma (Raji), and acute lymphoblastic leukemia (697) cell lines, the 48-hr IC₅₀ (50% growth inhibitory concentration) of AR-42 is 0.61 µM or less. In chronic lymphocytic leukemia (CLL) patient cells, the 48-hr LC₅₀ (concentration lethal to 50%) of AR-42 is 0.76 µM. AR-42 produces dose- and time-dependent acetylation both of histones and tubulin, and induces caspase-dependent apoptosis that is not reduced in the presence of stromal cells. AR-42 also sensitizes CLL cells to TNF-Related Apoptosis Inducing Ligand (TRAIL), potentially through reduction of c-FLIP. AR-42 significantly reduced leukocyte counts and/or prolonged survival in three separate mouse models of B-cell malignancy without evidence of toxicity.

Conclusions/Significance

Together, these data demonstrate that AR-42 has in vitro and in vivo efficacy at tolerable doses. These results strongly support upcoming phase I testing of AR-42 in B-cell malignancies.

Development of novel adenosine monophosphate-activated protein kinase activators

In light of the unique ability of thiazolidinediones to mediate peroxisome proliferator-activated receptor (PPAR)gamma-independent activation of adenosine monophosphate-activated protein kinase (AMPK) and suppression of interleukin (IL)-6 production, we conducted a screening of an in-house, thiazolidinedione-based focused compound library to identify novel agents with these dual pharmacological activities. Cell-based assays pertinent to the activation status of AMPK and mammalian homologue of target of rapamycin (i.e., phosphorylation of AMPK and p70 ribosomal protein S6 kinase, respectively) and IL-6/IL-6 receptor signaling (i.e., IL-6 production and signal transducer and activator of transcription 3 phosphorylation, respectively) in lipopolysaccharide (LPS)-stimulated THP-1 human macrophages were used to screen this compound library, which led to the identification of compound 53 (N-{4-[3-(1-methyl-cyclohexylmethyl)-2,4-dioxo-thiazolidin-5-ylidene-methyl]-phenyl}-4-nitro-3-trifluoro-methyl-benzenesulfonamide) as the lead agent. Evidence indicates that this drug-induced suppression of LPS-stimulated IL-6 production was attributable to AMPK activation. Furthermore, compound 53-mediated AMPK activation was demonstrated in C-26 colon adenocarcinoma cells, indicating that it is not a cell line-specific event.

Energy restriction as an antitumor target of thiazolidinediones

Cancer cells gain growth advantages in the microenvironment by shifting cellular metabolism to aerobic glycolysis, the so-called Warburg effect. There is a growing interest in targeting aerobic glycolysis for cancer therapy by exploiting the differential susceptibility of malignant versus normal cells to glycolytic inhibition, of which the proof-of-concept is provided by the in vivo efficacy of dietary caloric restriction and natural product-based energy restriction-mimetic agents (ERMAs) such as resveratrol and 2-deoxyglucose in suppressing carcinogenesis in animal models. Here, we identified thiazolidinediones as a novel class of ERMAs in that they elicited hallmark cellular responses characteristic of energy restriction, including transient induction of Sirt1 (silent information regulator 1) expression, activation of the intracellular fuel sensor AMP-activated protein kinase, and endoplasmic reticulum stress, the interplay among which culminated in autophagic and apoptotic death. The translational implications of this finding are multifold. First, the novel function of troglitazone and ciglitazone in targeting energy restriction provides a mechanistic basis to account for their peroxisome proliferator-activated receptor gamma-independent effects on a broad spectrum of signaling targets. Second, we demonstrated that Sirt1-mediated up-regulation of beta-transducin repeat-containing protein-facilitated proteolysis of cell cycle- and apoptosis-regulatory proteins is an energy restriction-elicited signaling event and is critical for the antitumor effects of ERMAs. Third, it provides a molecular rationale for using thiazolidinediones as scaffolds to develop potent ERMAs, of which the proof-of-principle is demonstrated by OSU-CG12. OSU-CG12, a peroxisome proliferator-activated receptor gamma-inactive ciglitazone derivative, exhibits 1- and 3-order of magnitude higher potency in eliciting starvation-like cellular responses relative to resveratrol and 2-deoxyglucose, respectively.

3-Phosphoinositide-dependent protein kinase-1/Akt signalling and inhibition in a canine prostate carcinoma cell line

Deregulation of the 3-phosphoinositide-dependent protein kinase-1 (PDK-1)/Akt signalling pathway is associated with prostate cancer development and progression. Inhibition of PDK-1/Akt signalling can be achieved using structurally optimized celecoxib derivatives such as OSU-03012. In this study, we treated the novel canine prostate cancer cell line, Ace-1, with OSU-03012 or dimethyl sulphoxide in vitro. We found that Akt was constitutively phosphorylated in the canine prostate cancer cell line Ace-1 and that there was a dose-dependent decrease in cell viability, and Akt and glycogen synthase kinase-3beta phosphorylation, in response to OSU-03012 treatment. This was accompanied by a dose-dependent increase in apoptosis. These data suggest that Akt signalling pathway inhibition is a potential strategy for the treatment of dogs with prostate cancer and that canine prostate cancer is a relevant large animal model for evaluating Akt pathway inhibitors such as OSU-03012 for use in people.

Eradication of intracellular Francisella tularensis in THP-1 human macrophages with a novel autophagy inducing agent

BACKGROUND

Autophagy has been shown recently to play an important role in the intracellular survival of several pathogenic bacteria. In this study, we investigated the effect of a novel small-molecule autophagy-inducing agent, AR-12, on the survival of Francisella tularensis, the causative bacterium of tularemia in humans and a potential bioterrorism agent, in macrophages.

METHODS AND RESULTS

Our results show that AR-12 induces autophagy in THP-1 macrophages, as indicated by increased autophagosome formation, and potently inhibits the intracellular survival of F. tularensis (type A strain, Schu S4) and F. novicida in macrophages in association with increased bacterial co-localization with autophagosomes. The effect of AR-12 on intracellular F. novicida was fully reversed in the presence of the autophagy inhibitor, 3-methyl adenine or the lysosome inhibitor, chloroquine. Intracellular F. novicida were not susceptible to the inhibitory activity of AR-12 added at 12 h post-infection in THP-1 macrophages, and this lack of susceptibility was independent of the intracellular location of bacteria.

CONCLUSION

Together, AR-12 represents a proof-of-principle that intracellular F. tularensis can be eradicated by small-molecule agents that target innate immunity.

alpha-Tocopheryl succinate as a scaffold to develop potent inhibitors of breast cancer cell adhesion

This study is aimed at the pharmacological exploitation of alpha-tocopheryl succinate (1) to develop potent antiadhesion agents. Considering the structural cooperativity between the phytyl chain and the carboxylic terminus in determining the antiadhesion activity, our structural optimization led to compound 5 ([2-(4,8-dimethyl-non-1-enyl)-2,5,7,8-tetramethyl-chroman-6-yloxy]-acetic acid), which exhibited an-order-of-magnitude higher potency than 1 in blocking the adhesion of 4T1 metastatic breast cancer cells to extracellular matrix proteins (IC(50), 0.6 microM versus 10 microM). Evidence indicates that the ability of compound 5 to block cell adhesion and migration was attributable to its effect on disrupting focal adhesion and actin cytoskeletal integrity by facilitating the degradation of focal adhesion kinase. Interactions between tumor cells and the ECM in the tumor microenvironment have been increasingly recognized as critical modulators of the metastatic potential of tumor cells. Consequently, the ability of compound 5 to block such interactions provides a unique pharmacological tool to shed light onto mechanisms that govern cell adhesion and tumor metastasis.

OSU-A9, a potent indole-3-carbinol derivative, suppresses breast tumor growth by targeting the Akt-NF-kappaB pathway and stress response signaling

The molecular heterogeneity of human tumors challenges the development of effective preventive and therapeutic strategies. To overcome this issue, a rational approach is the concomitant targeting of clinically relevant cellular abnormalities with combination therapy or a potent multi-targeted agent. OSU-A9 is a novel indole-3-carbinol derivative that retains the parent compound's ability to perturb multiple components of oncogenic signaling, but provides marked advantages in chemical stability and antitumor potency. Here, we show that OSU-A9 exhibits two orders of magnitude greater potency than indole-3-carbinol in inducing apoptosis in various breast cancer cell lines with distinct genetic abnormalities, including MCF-7, MDA-MB-231 and SKBR3, with the half maximal inhibitory concentration in the range of 1.2-1.8 microM vis-à-vis 200 microM for indole-3-carbinol. This differential potency was paralleled by OSU-A9's superior activity against multiple components of the Akt-nuclear factor-kappa B (NF-kappaB) and stress response signaling pathways. Notable among these were the increased estrogen receptor (ER)-beta/ERalpha expression ratio, reduced expression of HER2 and CXCR4 and the upregulation of aryl hydrocarbon receptor expression and its downstream target NF-E2 p45-regulated factor (Nrf2). Non-malignant MCF-10A cells were resistant to OSU-A9's antiproliferative effects. Daily oral administration of OSU-A9 at 25 and 50 mg/kg for 49 days significantly inhibited MCF-7 tumor growth by 59 and 70%, respectively, without overt signs of toxicity or evidence of induced hepatic biotransformation enzymes. In summary, OSU-A9 is a potent, orally bioavailable inhibitor of the Akt-NF-kappaB signaling network, targeting multiple aspects of breast tumor pathogenesis and progression. Thus, its translational potential for the treatment or prevention of breast cancer warrants further investigation.

Targeting of the Akt-nuclear factor-kappa B signaling network by [1-(4-chloro-3-nitrobenzenesulfonyl)-1H-indol-3-yl]-methanol (OSU-A9), a novel indole-3-carbinol derivative, in a mouse model of hepatocellular carcinoma

Constitutive activation of Akt and nuclear factor-kappaB (NF-kappaB) represents major cellular abnormalities associated with the development and progression of hepatocellular carcinoma (HCC). Based on the structure of indole-3-carbinol, a chemopreventive phytochemical, we developed a novel derivative, [1-(4-chloro-3-nitrobenzenesulfonyl)-1H-indol-3-yl]-methanol (OSU-A9), that exhibits higher potency in inducing apoptosis by targeting the Akt-NF-kappaB signaling network. This study was aimed at assessing the antitumor activity of OSU-A9 using both in vitro and in vivo models of HCC, a malignancy in which the Akt-NF-kappaB signaling network plays major roles in pathogenesis and therapeutic resistance. Our data show that OSU-A9 was 100 times more potent than indole-3-carbinol in suppressing the viability of Hep3B, Huh7, and PLC5 HCC cells with IC(50) values ranging from 2.8 to 3.2 microM. OSU-A9 interfered with the interplay between Akt- and NF-kappaB-mediated oncogenic signaling, leading to changes in the functional status of diverse signaling effectors involved in cell cycle progression, apoptosis, angiogenesis, and metastasis. The in vivo efficacy of OSU-A9 was assessed in nude mice bearing luciferase-expressing Hep3B xenograft tumors. Daily oral treatments with OSU-A9 at 25 or 50 mg/kg for 56 days suppressed tumor growth by 67 and 80%, respectively, which was correlated with changes in intratumoral biomarkers pertinent to Akt-NF-kappaB signaling, and without apparent toxicity or evidence of hepatic biotransformation enzyme induction. Together, these findings indicate that OSU-A9 is a potent, orally bioavailable inhibitor of the Akt-NF-kappaB signaling network with a broad spectrum of antitumor activity that includes targets regulating multiple aspects of HCC pathogenesis and progression.

alpha-Tocopheryl succinate and derivatives mediate the transcriptional repression of androgen receptor in prostate cancer cells by targeting the PP2A-JNK-Sp1-signaling axis

As part of our effort to understand the mechanism underlying alpha-tocopheryl succinate [vitamin E succinate (VES)]-mediated antitumor effects, we investigated the signaling pathway by which VES suppresses androgen receptor (AR) expression in prostate cancer cells. VES and, to a greater extent, its truncated derivative TS-1 mediated transcriptional repression of AR in prostate cancer cells but not in normal prostate epithelial cells; a finding that underscores the differential susceptibility of normal versus malignant cells to the antiproliferative effect of these agents. This AR repression was attributable to the ability of VES and TS-1 to facilitate the proteasomal degradation of the transcription factor Sp1. This mechanistic link was corroborated by the finding that proteasome inhibitors or ectopic expression of Sp1 protected cells against drug-induced AR ablation. Furthermore, evidence suggests that the destabilization of Sp1 by VES and TS-1 resulted from the inactivation of Jun N-terminal kinases (JNKs) as a consequence of increased phosphatase activity of protein phosphatase 2A (PP2A). Stable transfection of LNCaP cells with the dominant-negative JNK1 plasmid mimicked drug-induced Sp1 repression, whereas constitutive activation of JNK kinase activity or inhibition of PP2A activity by okadaic acid protected Sp1 from VES- and TS-1-induced degradation. From a mechanistic perspective, the ability of VES and TS-1 to activate PP2A activity underscores their broad spectrum of effects on multiple signaling mechanisms, including those mediated by Akt, mitogen-activated protein kinases, nuclear factor kappaB, Sp1 and AR. This pleiotropic effect in conjunction with low toxicity suggests the translational potential for developing TS-1 into potent PP2A-activating agents for cancer therapy.

Thiazolidinediones mimic glucose starvation in facilitating Sp1 degradation through the up-regulation of beta-transducin repeat-containing protein

This study investigated the mechanism by which the transcription factor Sp1 is degraded in prostate cancer cells. We recently developed a thiazolidinedione derivative, (Z)-5-(4-hydroxy-3-trifluoromethylbenzylidene)-3-(1-methylcyclohexyl)-thiazolidine-2,4-dione (OSU-CG12), that induces Sp1 degradation in a manner paralleling that of glucose starvation. Based on our finding that thiazolidinediones suppress beta-catenin and cyclin D1 by up-regulating the E3 ligase SCF(beta-TrCP), we hypothesized that beta-transducin repeat-containing protein (beta-TrCP) targets Sp1 for proteasomal degradation in response to glucose starvation or OSU-CG12. Here we show that either treatment of LNCaP cells increased specific binding of Sp1 with beta-TrCP. This direct binding was confirmed by in vitro pull-down analysis with bacterially expressed beta-TrCP. Although ectopic expression of beta-TrCP enhanced the ability of OSU-CG12 to facilitate Sp1 degradation, suppression of endogenous beta-TrCP function by a dominant-negative mutant or small interfering RNA-mediated knockdown blocked OSU-CG12-facilitated Sp1 ubiquitination and/or degradation. Sp1 contains a C-terminal conventional DSG destruction box ((727)DSGAGS(732)) that mediates beta-TrCP recognition and encompasses a glycogen synthase kinase 3beta (GSK3beta) phosphorylation motif (SXXXS). Pharmacological and molecular genetic approaches and mutational analyses indicate that extracellular signal-regulated kinase-mediated phosphorylation of Thr739 and GSK3beta-mediated phosphorylation of Ser728 and Ser732 were critical for Sp1 degradation. The ability of OSU-CG12 to mimic glucose starvation to activate beta-TrCP-mediated Sp1 degradation has translational potential to foster novel strategies for cancer therapy.

Growth inhibitory and anti-tumour activities of OSU-03012, a novel PDK-1 inhibitor, on vestibular schwannoma and malignant schwannoma cells

BACKGROUND

Vestibular schwannomas (VS) frequently express high levels of activated AKT. Small-molecule inhibitors of AKT signalling may have therapeutic potential in suppressing the growth of benign VS and malignant schwannomas.

METHOD

Primary VS and Schwann cells, human malignant schwannoma HMS-97 cells and mouse Nf2(-/-) Schwann cells and schwannoma cells were prepared to investigate the growth inhibitory and anti-tumour activities of OSU-03012, a celecoxib-derived small-molecule inhibitor of phosphoinositide-dependent kinase-1. Cell proliferation assays, apoptosis, Western blot, in vivo xenograft analysis using SCID mice and immunohistochemistry were performed.

RESULTS

OSU-03012 inhibited cell proliferation more effectively in both VS and HMS-97 cells than in normal human Schwann cells. The IC5) of OSU-03012 at 48h was approximately 3.1 microM for VS cells and 2.6 microM for HMS-97 cells, compared with the IC(50) of greater than 12 microM for human Schwann cells. Similarly, mouse Nf2(-/-) schwannoma and Nf2(-/-) Schwann cells were more sensitive to growth inhibition by OSU-03012 than wild-type mouse Schwann cells and mouse schwannoma cells established from transgenic mice carrying the NF2 promoter-driven SV40 T-antigen gene. Like VS cells, malignant schwannoma HMS-97 cells expressed high levels of activated AKT. OSU-03012 induced apoptosis in both VS and HMS-97 cells and caused a marked reduction of AKT phosphorylation at both the Ser-308 and Thr-473 sites in a dose-dependent manner. In vivo xenograft analysis showed that OSU-03012 was well tolerated and inhibited the growth of HMS-97 schwannoma xenografts by 55% after 9 weeks of oral treatment. The anti-tumour activity correlated with reduced AKT phosphorylation.

CONCLUSION

OSU-03012 is a potential chemotherapeutic agent for VS and malignant schwannomas.

Evaluation of the effects of histone deacetylase inhibitors on cells from canine cancer cell lines

OBJECTIVE

To determine whether exposure of canine cancer cells to histone deacetylase (HDAC) inhibitors S(+)-N-hydroxy-4-(3-methyl-2-phenyl-butyrylamino)benzamide (OSU-HDAC42) or suberoylanilide hydroxamic acid (SAHA) results in increased histone acetylation and decreased cell viability and whether any changes in viability involve induction of apoptosis or alterations in progression of the cell cycle.

SAMPLE POPULATION

9 canine cancer cell lines.

PROCEDURES

Cells from 9 canine cancer cell lines were treated with dimethyl sulfoxide vehicle, OSU-HDAC42, or SAHA, then assays of cell viability were performed. Histone acetylation was assessed by use of western blot analysis. Apoptosis was assessed via ELISA to detect fragmentation of cytoplasmic nucleosomal DNA and western blot analysis to detect cleavage of caspase 3. Cell cycle analysis was performed by use of propidium iodide staining and flow cytometry. RESULTS-Concentrations of OSU-HDAC42 and SAHA required to achieve 50% inhibition of cell viability (IC(50)) were reached in cells of 6 and 4 canine cancer cell lines, respectively, and ranged from approximately 0.4 to 1.3 microM for OSU-HDAC42 and 0.6 to 4.8 microM for SAHA. Cells from T-cell lymphoma, mast cell tumor, osteosarcoma, and histiocytic sarcoma lines were most sensitive to HDAC inhibition, with IC(50)s of < 1 microM for OSU-HDAC42 and < 5 microM for SAHA. Induction of apoptosis was indicated via cleavage of caspase 3 and increases in cytoplasmic nucleosomes and the subG(1) cell population.

CONCLUSIONS AND CLINICAL RELEVANCE

Micromolar concentrations of HDAC inhibitors OSU-HDAC42 and SAHA induced histone acetylation, cytotoxicity, and apoptosis in canine cancer cells. In general, OSU-HDAC42 was more potent than SAHA.

A novel mechanism by which thiazolidinediones facilitate the proteasomal degradation of cyclin D1 in cancer cells

This study identifies a novel mechanism by which thiazolidinediones mediate cyclin D1 repression in prostate cancer cells. Based on the finding that the thiazolidinedione family of peroxisome proliferator-activated receptor gamma (PPARgamma) agonists mediated PPARgamma-independent cyclin D1 degradation, we developed a novel PPARgamma-inactive troglitazone derivative, STG28, with high potency in cyclin D1 ablation. STG28-mediated cyclin D1 degradation was preceded by Thr-286 phosphorylation and nuclear export, which however, were independent of glycogen synthase kinase 3beta. Mutational analysis further confirmed the pivotal role of Thr-286 phosphorylation in STG28-induced nuclear export and proteolysis. Of several kinases examined, inhibition of IkappaB kinase alpha blocked STG28-mediated cytoplasmic sequestration and degradation of cyclin D1. Pulldown of ectopically expressed Cul1, the scaffold protein of the Skp-Cullin-F-box E3 ligase, in STG28-treated cells revealed an increased association of cyclin D1 with beta-TrCP, whereas no specific binding was noted with other F-box proteins examined, including Skp2, Fbw7, Fbx4, and Fbxw8. This finding represents the first evidence that cyclin D1 is targeted by beta-TrCP. Moreover, beta-TrCP expression was up-regulated in response to STG28, and ectopic expression and small interfering RNA-mediated knock-down of beta-TrCP enhanced and protected against STG28-facilitated cyclin D1 degradation, respectively. Because cyclin D1 lacks the DSG destruction motif, mutational and modeling analyses indicate that cyclin D1 was targeted by beta-TrCP through an unconventional recognition site, (279)EEVDLACpT(286), reminiscent to that of Wee1. Moreover, we obtained evidence that this beta-TrCP-dependent degradation takes part in controlling cyclin D1 turnover when cancer cells undergo glucose starvation, which endows physiological relevance to this novel mechanism.