Abstract 2034: A novel therapeutic compound, tolfenamic acid, inhibits ovarian cancer cell growth: Therapeutic implications

Abstract

Abstract Specificity protein (Sp) transcription factors mediate the expression of key genes associated with various human cancers. The aberrant expression of hepatocyte growth factor and its receptor c-Met are associated with aggressive disease and poor prognosis in a variety of human malignancies including ovarian cancer (OC) and survivin is associated with poor response to chemotherapy and radiation therapy. Sp proteins have high relevance in the signaling cascade associated with c-Met activation and regulate the expression of survivin. The non-steroidal anti-inflammatory drug, tolfenamic acid (TA) is known to induce the degradation of Sp proteins in pancreatic, esophageal and lung cancer models. Our aim was to investigate the anti-cancer activity of TA in ovarian cancer model. We developed three OC sub-cell lines (AF1-3) derived from the original OC cell line, SKOV-3. These sub-lines are more resistant to IFNα-2b and more tumorigenic in nude mice than the original SKOV-3 cells. The anti-cancer activity of TA was tested in ES2 and SKOV-3-derived cells. The cells were treated with DMSO (vehicle) or TA (25/50/100µM) and cell viability was measured at 24, 48, and 72 h. Cell lysates were prepared following 48 h treatment (50µM) and evaluated the expression of Sp proteins (Sp1/Sp3/Sp4), c-Met, survivin, Bcl2, and cleaved polyADP-ribose polymerase (c-PARP) through Western blot analysis. Cell cycle distribution and apoptosis were analyzed using BD FACS Calibur flow cytometer. Results showed that TA significantly inhibited the growth of SKOV3 (AF1-3) and ES2 cells. The inhibition was 40-60% within 48 h with 50µM and >90% with 100 µM TA dose. The expression of Sp proteins and c-Met were significantly decreased (40-60%) suggesting that TA could be targeting c-Met through degradation of Sp proteins. TA greatly increased the apoptotic fraction (Annexin V positive) and c-PARP expression (70-80%), decreased Bcl2 expression and also induced G0/G1 cell cycle arrest. These results show that TA has a profound inhibitory effect on OC cells proliferation, induces apoptosis, cell cycle arrest and Sp proteins degradation. TA also inhibited (50-60%) the expression of inhibitor of apoptosis protein family, survivin that is associated with radiation resistance and suggesting that apart from its tumor suppressant effects, TA may also enhance the tumor response to radiotherapy. These striking data clearly show that TA effectively inhibits OC cell growth in vitro even at low/therapeutic concentrations. This study demonstrates a potential role for TA that suppresses OC cells growth, and may enhance tumor response to radiotherapy, and have implications in OC treatment. 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 2034. doi:10.1158/1538-7445.AM2011-2034