Abstract 2166: Tolfenamic acid analogs inhibit prostate cancer cell growth and tumor development in orthotopic mice potentially through suppressing specificity protein transcription factors

Developing novel approaches for the treatment of prostate cancer is critical due to limitations in the availability of effective therapeutic options. Specificity protein (Sp) transcription factors mediate the expression of key genes associated with tumorigenesis/metastasis in several cancers. Sp proteins regulate the expression of PSA, c-Met and survivin. Recently, we have reported the anticancer activity of a NSAID, tolfenamic acid (TA) in pancreatic, esophageal and lung cancer models that acts through downregulating the expression of Sp proteins. In this investigation, along with TA, we have screened several TA analogs to evaluate their anticancer activity in prostate cancer model in order to identify robust candidates for the treatment of this devastating disease. TA analogs were selected based on their structural relationship with TA. Human prostate cancer cells (PC-3, DU-145 and LNcaP) were grown in the presence of DMSO (vehicle) or various concentrations (25, 50 and 100 µM) of TA and selected analogs and cell proliferation was measured at 24, 48, and 72 h post-treatment using Cell Titer-Glo kit (Promega). Results showed a significant decrease in cell proliferation that was dose and time dependent. Screening the anti-proliferative activity, we identified at least two TA analogs that inhibited the cell viability more than parental compound TA. Further studies were conducted with the two active TA analogs. PC-3 cells were treated with vehicle or 50 µM TA analogs for 48 h and cell lystaes were prepared and used to evaluate the expression of Sp proteins, c-Met, Akt and survivin through Western blot analysis. Scratch (wound healing) assay was performed to determine the effect of these drugs on PC-3 cell migration. TA and other two active analogs significantly diminished the expression of Sp proteins, c-Met, phospho-Akt and survivin and inhibited cell migration. Interestingly, the effect of two TA analogs tested was greater than TA which was consistent with their higher anti-proliferative activity. Nude mice were injected with PC-3 cells into the right prostate and treated with vehicle or 50 mg/kg of one of the active TA analog/3 times a week and tumor growth was continuously monitored for 4 weeks. Results showed a significant decrease (>50%) in tumor weight/volume after 4 weeks of treatment confirming a strong correlation between in vitro and in vivo results. These results suggest that TA analogs inhibit prostate cancer cell proliferation, downregulate the expression of c-Met and survivin, and disrupt phosphorylation of Akt through suppressing Sp proteins. Targeting key transcription factors such as Sp proteins using small molecules is a new strategy for the treatment of prostate cancer. In this interesting screening test, we have identified a few promising active TA analogs for the potential implications in prostate cancer therapy. 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 2166. doi:10.1158/1538-7445.AM2011-2166