Ketorolac modulates Rac-1/HIF-1α/DDX3/β-catenin signalling via a tumor suppressor prostate apoptosis response-4 (Par-4) in renal cell carcinoma

Renal cell carcinoma (RCC) is the most difficult-to-treat form of kidney cancer with a median 5-year survival of 10% under metastatic setting. In RCC, although cytoreductive nephrectomy is common, approximately 20-30% of patients will develop recurrent cancer after surgery, which highlights the need for an effective therapy. Rho-GTPases viz, Rac-1 and Cdc42 are the central regulators of cancer cell migration and invasion and thus metastasis in multiple cancer types. Hence, we elucidated the role of Ketorolac, a modulator Rho-GTPases against RCC through potentiation of tumor suppressor Par-4. The effect of Ketorolac alone and in combination on proliferation, apoptosis, cell-cycle progression, migration, tumor inhibition and their related markers were studied. Moreover, Ketorolac's impact on metastasis by influencing Rac-1/HIF-1α/DDX3/β-catenin signalling was studied with respect to its ability to modulate the expression of tumor suppressor Par-4, and this mechanism was confirmed by siRNA knockdown studies. Ketorolac induced cytotoxicity in a panel of renal cells including patient derived tumor cells with IC₅₀ 2.8 to 9.02 mM and 0.28 to 3.8 mM in monolayer and anchorage independent clonogenic assays respectively. Ketorolac caused significant down regulation of proliferation (Ki-67, Cyclin D1, pRB and DDX3), migration/invasion (Rac-1, Cdc42, and Tiam1), and angiogenesis (HIF-1α and VEGF) markers as studied by gene and protein expression. Moreover, it caused a significant upregulation of tumor suppressor Par-4 known to be downregulated in RCC. This mechanism was further confirmed by using siRNA knockdown studies where we could demonstrate a negative relation between the expression of Par-4 and Rac-1/Cdc42. Importantly, Ketorolac alone and in combination with Sunitinib showed tumor growth inhibition (TGI) of 73% and 86% respectively in xenograft model. This anti-tumor activity was further corroborated by down regulation of Rac-1/Cdc42/HIF-1α/DDX3/β-catenin signalling. This is the first report which implicates the role of Ketorolac against RCC by acting as a small molecule secretagogue causing upregulation of Par-4 in autocrine and paracrine manner. Consequently, these findings suggest that Par-4 can serve as a valuable therapeutic target and a prognostic marker for the treatment of RCC.

Cink4T, a quinazolinone-based dual inhibitor of Cdk4 and tubulin polymerization, identified via ligand-based virtual screening, for efficient anticancer therapy

Inhibition of cyclin dependent kinase 4 (Cdk4) prevents cancer cells from entering the early G₀/G₁ phase of the cell division cycle whereas inhibiting tubulin polymerization blocks cancer cells' ability to undergo mitosis (M) late in the cell cycle. We had reported earlier that two non-planar and relatively non-toxic fascaplysin derivatives, an indole and a tryptoline, inhibit Cdk4 with IC₅₀ values of 6.2 and 10 μM, respectively. Serendipitously, we had also found that they inhibited tubulin polymerization. The molecules were efficacious in mouse tumor models. We have now identified Cink4T in a 59-compound quinazolinone library, designed on the basis of ligand-based virtual screening, as a compound that inhibits Cdk4 and tubulin. Its IC₅₀ value for Cdk4 inhibition is 0.47 μM and >50 μM for inhibition of Cdk1, Cdk2, Cdk6, Cdk9. Cink4T inhibits tubulin polymerization with an IC₅₀ of 0.6 μM. Molecular modelling studies on Cink4T with Cdk4 and tubulin crystal structures lend support to these observations. Cancer cell cycle analyses confirm that Cink4T blocks cells at both G₀/G₁ and M phases as it should if it were to inhibit both Cdk4 and tubulin polymerization. Our results show, for the very first time, that virtual screening can be used to design novel inhibitors that can potently block two crucial phases of the cell division cycle.

Biphenyl urea derivatives as selective CYP1B1 inhibitors

Herein, we report the discovery of ‘biphenyl ureas’ as selective CYP1B1 inhibitors.

P7170, a novel inhibitor of mTORC1/mTORC2 and Activin receptor-like Kinase 1 (ALK1) inhibits the growth of non small cell lung cancer

BACKGROUND

Lung cancer is the major cause of cancer-related deaths and many cases of Non Small Cell Lung Cancer (NSCLC), a common type of lung cancer, have frequent genetic/oncogenic activation of EGFR, KRAS, PIK3CA, BRAF, and others that drive tumor growth. Some patients though initially respond, but later develop resistance to erlotinib/gefitinib with no option except for cytotoxic therapy. Therefore, development of novel targeted therapeutics is imperative to provide improved survival benefit for NSCLC patients. The mTOR cell survival pathway is activated in naïve, or in response to targeted therapies in NSCLC.

METHODS

We have discovered P7170, a small molecule inhibitor of mTORC1/mTORC2/ALK1 and investigated its antitumor efficacy using various in vitro and in vivo models of human NSCLC.

RESULTS

P7170 inhibited the phosphorylation of AKT, S6 and 4EBP1 (substrates for mTORC2 and mTORC1) levels by 80-100% and growth of NSCLC cells. P7170 inhibited anchorage-independent colony formation of NSCLC patient tumor-derived cells subsistent of disease sub-types. The compound also induced apoptosis in NSCLC cell lines. P7170 at a well-tolerated daily dose of 20 mg/kg significantly inhibited the growth of NSCLC xenografts independent of different mutations (EGFR, KRAS, or PIK3CA) or sensitivity to erlotinib. Pharmacokinetic-pharmacodynamic (PK-PD) analysis showed sub-micro molar tumor concentrations along with mTORC1/C2 inhibition.

CONCLUSIONS

Our results provide evidence of antitumor activity of P7170 in the erlotinib -sensitive and -insensitive models of NSCLC.

Abstract 3437: P276, a cyclin-dependent kinase inhibitor with antitumor activity against high-risk human cervical cancer

Cervical cancer is the third most common cancer worldwide in women. While preventive vaccines have been approved for cervical cancer, treatment options are limited to chemotherapy drugs. An unmet need, thus, exists for the treatment of cervical cancer. High-risk human papilloma viruses (HPVs), type 16 and 18, account for 70% of the cervical cancer. Viral oncoproteins E6 and E7 bind and inhibit the p53 and Rb tumor suppressors, respectively. One attractive strategy for the treatment of cervical cancer is to attenuate the expression of E6 and E7 viral oncoproteins by a pharmacological inhibitor of cyclin-dependent kinases (CDKs). P276 is a CDKs inhibitor with potent activity against CDK4, CDK1 and CDK9 (Joshi et al, Mol. Cancer Ther. 2007; 6:918-25). The therapeutic potential and mechanism of action of P276 in cervical cancer was investigated using high-risk HPV type 16 (SiHa and Caski) and type 18 (HeLa) human cervical cancer cell line. P276 inhibited cell growth with sub-micromolar IC50 values (0.5-0.8 μM), induced cell cycle arrest and apoptosis in cervical cancer lines. E6 negatively regulates p53 protein stability in HPV-infected cervical cancer. P276 downregulated mRNA and protein expression of E6 in SiHa cells with concomitant upregulation of p53 protein and its downstream target p21, indicating activation of the p53 pathway. It also downregulated E7 mRNA expression in SiHa and HeLa cell lines. Further, it is known that hyperphosphorylation of Rb relieves its interaction with E2F, leading to Rb inactivation and E2F activation. Treatment with P276 dephosphorylated Rb at Ser780, indicating Rb activation. P276 demonstrated significant (p<0.01) in vivo efficacy in HPV type 16 SiHa human cervical cancer xenograft model when administered by i.p. route, Treatment with 25 mg/kg of P276 for 21 days induced 59% of tumor growth inhibition without body weight loss in this model. Conclusion: P276, a CDKs inhibitor, is efficacious against high-risk cervical cancer.

Citation Format: Sanjeev Kumar Shangary, Gandhali Deshpande, Vinay Sonawane, Venkatesha Venkatasubbaiah, Archana Jalota-Badhwar, Asavari Joshi, Manoj Mayekar, Nitesh Shirsath, Prashant Pandey, Veena R. Agarwal. P276, a cyclin-dependent kinase inhibitor with antitumor activity against high-risk human cervical cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3437. doi:10.1158/1538-7445.AM2013-3437

Abstract 1822: Novel potent inhibitor of Bcr-Abl mutated imatinib resistant chronic myeloid leukemia cell lines

The hallmark of chronic myeloid leukemia (CML) is the presence of Bcr-Abl oncoprotein that is essential for leukemogenesis and accumulation of neoplastic cells. The Abl tyrosine kinase inhibitor imatinib mesylate (Gleevec) represents the standard treatment for CML. However, a number of CML patients develop imatinib resistance and several mechanisms of resistance have been described. While most mutant forms are sensitive to second-generation tyrosine kinase inhibitors, the T315I mutation remains completely refractory to imatinib, as well as to these agents. Treatment of CML patients harboring T315I mutation is still an unmet medical need in the imatinib and post-imatinib era. We have identified P2745, a novel orally bioavailable small molecule that is effective in imatinib resistant mutations and particularly T315I mutation form to address this unmet medical need. In vitro P2745 showed potent cytotoxicity (IC50 0.8-5 μM) in twelve Bcr-Abl mutated imatinib resistant cell lines including T315I compared to wild type Bcr-Abl cell lines. P2745 did not show cytotoxicity upto 30 μM in normal fibroblasts (MRC-5 and WI-38) and normal human peripheral blood mononuclear cells thus indicating specificity towards cancerous cells. P2745 inhibited pCrkLTyr207 in imatinib-resistant CML cell lines accompanied with down regulation of Bcr-Abl protein levels. Additionally, it up regulated tumor suppressor protein SMAR-1 which resulted in negative regulation TGF-β/SMAD-dependent pathway as demonstrated by low phosphorylated levels of SMAD2 and SMAD3, two key players implicated in the preservation of the malignant progenitor population, and partly responsible for the resistance to treatments targeting Bcr-Abl. P2745 also induced significant apoptosis in imatinib resistant cell lines (Y253F, T315I and E255V) but not in normal MRC-5 cell line. In addition, like imatinib it induced 80-90 % apoptosis in cells derived from CML patients. In vivo studies demonstrated significant (p<0.001), dose dependent efficacy in imatinib resistant T315I cells xenograft in SCID mice. It also demonstrated significant in vivo efficacy in Bcr-Abl wild type imatinib sensitive K-562 (p<0.05) and Ba/F3 (p<0.001) xenografts in SCID mice. PK-PD evaluation in imatinib resistant xenograft experiments indicated that at the efficacious dose, P2745 modulated proteins responsible for CML pathogenesis (60-80 %), which correlates with the levels of P2745 in the tumors. This unique mechanism of action makes P2745 a promising clinical candidate for CML patients harboring T315I mutation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1822. doi:1538-7445.AM2012-1822

A novel inhibitor of hypoxia-inducible factor-1α P3155 also modulates PI3K pathway and inhibits growth of prostate cancer cells

BACKGROUND

Hypoxia-inducible factor-1 (HIF-1) is a master regulator of the transcriptional response to hypoxia. It is essential for angiogenesis and is associated with tumor progression and overexpression of HIF-1α has been demonstrated in many common human cancers. Therefore, HIF-1α is one of the most compelling anticancer targets.

METHODS

To identify HIF-1α inhibitors, luciferase reporter gene assay under hypoxia and normoxia was used. Detailed studies such as western blotting, RT-PCR, immunofluorescence were carried out to elucidate its mechanism of action. Antiangiogenic activity of P3155 was demonstrated by migration assay and tube formation assay. Efficacy study of P3155 was performed on PC-3 xenograft model.

RESULTS

P3155 showed specific HIF-1α inhibition with IC50 of 1.4 μM under hypoxia. It suppressed HIF-1α expression as well as PI3K/Akt pathway and abrogated expression of HIF-1-inducible gene viz. vascular endothelial growth factor (VEGF). P3155 in combination with HIF-1α siRNA showed significant synergistic effect. In addition, it demonstrated significant in vivo efficacy and antiangiogenic potential in prostate cancer cell lines.

CONCLUSION

We have identified a novel HIF-1α inhibitor P3155 that also modulates PI3K/Akt pathway, which may contribute to its significant in vitro and in vivo antitumor activity.

Cyclin-dependent kinase inhibitor, P276-00 induces apoptosis in multiple myeloma cells by inhibition of Cdk9-T1 and RNA polymerase II-dependent transcription

P276-00 is a novel cyclin-dependent kinase inhibitor especially potent for Cdk9-T1, Cdk4-D1 and Cdk1-B. Multiple myeloma (MM) is a B-cell malignancy characterized by the accumulation of malignant plasma cells. Treatment of MM cell lines with P276-00 resulted in apoptosis that correlated with transcription inhibition and a significant decline in Mcl-1 protein levels with the appearance of cleaved PARP in these cells. In vivo studies of P276-00 confirmed antitumor activity in RPMI-8226 xenograft. These results suggest that P276-00 causes multiple myeloma cell death by disrupting the balance between cell survival and apoptosis through inhibition of transcription and downregulation of Mcl-1.

Abstract P6-15-05: A Cyclin-Dependent Kinase Inhibitor P276 Inhibits Growth of Breast Cancer Cell Lines Including Basal-Type/Triple-Negative Alone and in Combination with Chemotherapeutic Drugs

Background: Development of novel agents and drug combinations are urgently needed for the treatment of breast cancer especially triple negative breast cancer (TNBC). P276 is a potent cyclin-dependent kinase inhibitor with excellent antiproliferative activity against various human cancer cell lines. Here, we report the activity of P276, as a single agent and in combination with paclitaxel or gemcitabine/carboplatin in TNBC cell lines.

Material and Methods: In vitro effect of P276 on breast cancer cell lines was determined by cytotoxicity assay, flow cytometry, western blotting and immunofluorescence studies. The antiangiogenic potential of P276 was evaluated using HIF-1 a and VEGF inhibition assay, wound healing and tube formation. In vivo efficacy was studied using human xenograft models in SCID and nude mice.

Results: Human breast cancer cell lines including TNBC, treated with P276 were found to be highly susceptible with IC50 ranging from 0.3 to 1.0 mM. In MCF-7 (Her2-, BRCA+/−) and MDA-MB-231 (ER-, PR-, Her2-). P276 significantly down regulated cell cycle proteins pRbser780, cyclin D1, Cdk4 and antiapoptotic protein Bcl-2 followed by 80-85% apoptosis. P276 treatment also lead to the inhibition of PARP enzyme activity or PARP cleavage depending on the cell type. Interestingly, P276 inhibited the key angiogenic mediators HIF-1 a and VEGF with IC50 of 0.095mM and 0.31mM respectively in reporter gene based assays. These antiangiogenic effects were confirmed by immunofluorescence and migration studies in TNBC cell lines and endothelial tube formation. In breast cancer patient derived tumor cell line MAXF 401 (basal like) xenografts in nude mice, cyclical dosing of P276 showed growth inhibition of 71%. Moreover, combination studies of P276 with paclitaxel or gemcitabine plus carboplatin showed synergistic effect in TNBC cell lines. Discussion: Our studies provide compelling evidence for the clinical development of P276 for the treatment of triple negative breast cancer either as monotherapy or in combination with paclitaxel or gemcitabine/carboplatin.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-15-05.