Abstract 2937: Expression of osteopontin splicing isoforms in prostate cancer cells resistant to docetaxel

Abstract

Abstract Resistance to chemotherapeutic drugs corresponds to main causes of treatment failure. Total osteopontin (OPN) has been described as a gene product involved on chemoresistance, besides activating several aspects of tumor progression. OPN regulates the expression of P-glycoprotein (P-gp) in prostate cancer (PCa) cells, besides promoting apoptosis evasion induced by chemotherapy using paclitaxel and estramustin. These data point OPN as a potential therapeutic target to approaches that could reduce chemotherapy tumor resistance. However, most of this data are related to total OPN. Once OPN suffers alternative splicing, producing 3 isoforms, further investigation should demostrate their specific involvement on chemoresistance. Recent data from our group indicated that OPNb and OPNc splicing isoforms activate PCa tumor progression features. Besides, PCa cells that overexpress these splice variants are more resistant to apoptosis induced by docetaxel (DXT). The current work aims to investigate the expression pattern of OPN splicing isoforms (OPN-SIs) and their relationships in DXT-PCa resistant cells. Total RNA has been extracted from PCa cell lines resistant to DXT (PC3-D8 and PC3-D12) and PC3 control cells with similar cell passages (PC3-Ag). Then, cDNa has been synthesized. OPN-SI expression levels were analyzed by quantitative real time PCR (qRT-PCR) using SYBR Green and isoform specific oligonucleotides. Relative expression levels were calculated using ΔΔCT method. Among the 3 OPN-SIs, we observed that OPNb and OPNc variants are overexpressed in relation to OPNa in DXT-PCa resistant cells PC3-D8 and PC3-D12, when compared to PC3-Ag. PC3-D12 cell line, resistant to higher DXT concentrations, expresses higher levels of OPNc, when compared to the other cell lines. Overall, our data further evidence that OPNb and OPNc overexpression in DXT-PCa resistant cells could be involved on resistance to DXT. Functional assays will be performed in order to investigate the molecular mechanisms by which these OPN-SIs mediate resistance to this chemotherapeutic drug. Citation Format: Mariana Concentino Menezes, Amanda O’Neil, Isabella Guimaraes, Letícia Rangel, Etel Rodrigues Pereira Gimba. Expression of osteopontin splicing isoforms in prostate cancer cells resistant to docetaxel. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2937.