Abstract 3420: Transcriptional regulation is critical in the stabilization of Snail induced by TGFβ
Authors: Jin Hongyan , Zhou Jia Yi , Lu Yilin , Zhou Binhua Peter , Yu Yinhua 
Published: June 2012

Although inflammation has been associated with the progression of ovarian cancer for decades, the molecular mechanisms involved in this process have not been well defined. In our previous study, we have identified that Snail, a key epithelial-mesenchymal transition (EMT) inducer, played a key role in the metastasis in ovarian carcinomas. Expression of Snail correlates with the stage of ovarian cancer and is significantly higher in metastatic lesions compared with that of primary tumors. Knockdown of Snail expression suppresses metastasis of ovarian carcinoma.; We also demonstrated that inflammation factors such as TNFα, TGFβ1, PMA and IL-6 constitute the critical extrinsic inflammatory factors for induction of Snail in mediating invasion and migration of ovarian cancer cells. Among these factors, TGFβ1 seems to be the most important one that not only induces the expression of Snail but also further synergizes Snail stabilization with other inflammation factors; To elucidate the role of TGFβ in ovarian cancer, we detected the secretion of TGFβ in the supernatant of ovarian cancer cell lines, as well as the expression of Smad 2/3, Smad4, TGFβRII in both ovarian cancer cell lines and normal ovarian epithelial cells. We found that TGFβ and its relative molecules were existed in both normal and ovarian carcinoma cell lines. To examine the signaling involved in TGFβ induced stabilization of Snail, firstly, we disrupted the canonical Smad pathway by using SB431542, a pharmacological inhibitor of TGFβRII, and a soluble TGFβ type II receptor, which can bind to three types of TGFβ isoforms and acts as inhibitor of TGFβ, Interestingly, we found that none of them blocked the expression of Snail, indicating that Smad- dependent signaling may not be the major pathway in inducing Snail mediated by TGFβ in ovarian carcinoma cells. We also investigated which no-smad signaling pathways were involved in TGFβ-mediated Snail stabilization, we treated the cells with inhibitor of the p38, MAPK, ERK, PI3K, JNK, Rho, since TGFβ can induce the activation of these pathways. Although TGFβ-mediated Snail stabilization was not affected by these inhibitors, we found that TGFβ-mediated Snail stabilization was completely blocked when cells were pretreated with a transcriptional inhibitor actinomycin D, indicating that an unknown mediator, which is transcriptionally induced by TGFβ but is blocked by ActD, was required for the stabilization of Snail. In addition, we incubated cells with TGFβ for 6 hours and then treated with protein translational inhibitor cycloheximide, and found that the rate of Snail degradation has no difference between TGFβ treated and untreated group. Taken together, these results strongly suggest that a mediator transcriptional induced by TGFβ is required to block the degradation of Snail.

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 3420. doi:10.1158/1538-7445.AM2011-3420