Abstract 3958: T315, a novel integrin-linked kinase inhibitor, suppresses hypoxia-induced epithelial-to-mesenchymal transition in prostate cancer.

Abstract

Abstract The epithelial-to-mesenchymal transition (EMT) is an early event in metastasis that involves the loss by epithelial cells of many of their distinctive epithelial characteristics and the acquisition of mesenchymal properties. EMT can be induced in cancer cells by several factors, such as hypoxia and TGF-β1, leading to an aggressive and malignant phenotype. In prostate cancer therapy, EMT can be a major clinical challenge as it can contribute to tumor recurrence, therapy resistance, and metastasis. Recently, the integrin-linked kinase (ILK) has been identified as an important protein involved in the process of EMT by inducing the protein expression and activation of Snail, one of the major EMT markers in various cancer cells. The objective of this study was to evaluate the ability of T315, a novel ILK inhibitor developed in our laboratory, to block hypoxia-induced EMT in prostate cancer cells and to validate the role of ILK in hypoxia-induced EMT. Based on our results, the protein expression level of ILK was induced by hypoxia as well as EMT examined by efficiently decreasing the protein expression level of E-cadherin and increasing those of vimentin, Snail, and Zeb1 in PC-3 cells. This ILK induction was due to transcriptional regulation by HIF1α which also could be induced by positively regulating ILK promoter. To elucidate the mechanism of hypoxia-induced EMT in prostate cancer, we used T315 to show its ability to downregulate PKB/Akt and mTOR activities and decrease HIF1α expression. These results showed that hypoxia-induced EMT is driven by HIF1α/ILK positive loop in prostate cancer. Meanwhile, we also demonstrated that YB-1, a DNA/RNA binding protein, plays as a transcriptional factor to negatively regulate the expression of Foxo3a which has been showed as an EMT-related protein to regulate Snail and E-cadherin expression. Our results showed T315 could increase Foxo3a expression by inhibition of YB-1 protein expression. On the other hand, according to a previous study, GSK3β-mediated Snail phosphorylation altered the nuclear sequestration of Snail and caused Snail to undergo proteasomal degradation. Our results also showed that T315 could cause GSK3β dephosphorylation, increase the phosphorylation status of Snail and promote Snail degradation. More importantly, we performed functional assays to observe the inhibition of hypoxia-induced EMT in prostate cancer. T315 showed its ability to inhibit hypoxia-induced cell motility dose-dependently in migration, invasion and 3D culture assays. In conclusion, these results indicate that the inhibition of ILK can block hypoxia-induced EMT in prostate cancer cells as reflected by changes in molecular markers and cell behavior, and that this inhibition can be achieved by treatment with the novel small molecule agent T315, which may have therapeutic benefits for prostate cancer patients with subsequent metastasis. Citation Format: Chih-Chien Chou, Su-Lin Lee, Samuel K. Kulp, Ching-Shih Chen. T315, a novel integrin-linked kinase inhibitor, suppresses hypoxia-induced epithelial-to-mesenchymal transition in prostate 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 3958. doi:10.1158/1538-7445.AM2013-3958