Abstract 5171: EGFR induction of SOX9 is required in a cellular migration program induced by urothelial injury and maintained in cancer

Data from a variety of tissue types and experimental systems indicate that the transcriptional regulator SRY-related HMG box 9 (SOX9) can be induced by injury and promote migration as well as tumor growth. We hypothesize that in cancers associated with chronic injury, such as urothelial carcinoma (UroCa), SOX9 may mediate epithelial injury repair. We found that urothelial SOX9 was induced during times of rapid proliferation during bladder organogenesis and injury repair. High levels of epidermal growth factor (EGF) ligands have been noted in urine and represent a potential trigger for urothelial injury repair programs. Using specific antagonists, we found that EGF receptor activation by cognate ligands heparain binding EGF-like growth factor (HB-EGF) and/or amphiregulin was responsible for Sox9 induction in urothelial cells and tissues. As expected, EGFR activation occurred through the mitogen associated protein kinase (MAPK) pathway. With chronic breaches of urothelial integrity, EGFR-Sox9 stimulation may promote urothelial carcinogenesis, as Sox9 expression was significantly upregulated in invasive human UroCa samples and cell lines. When expressed in established tumors, SOX9 may confer a selective advantage to cancer cells by promoting their ability to invade and colonize new sites. As support for this idea, small interfering RNA inhibition of SOX9 levels abrogated in vitro wound healing and invasion, suggesting a role for SOX9 in tumor spread. These results indicate a potential mechanism for urothelial carcinogenesis through an EGFR-MAPK-SOX9 cascade, and a further function for this axis in established cancers. Future studies will examine the potential mechanisms supporting perseverative SOX9 expression in cancer and opportunities for disrupting this pathway as a therapeutic strategy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5171.