Abstract 2097: Grainyhead-like 2 (GRHL2) regulates epithelial plasticity and stemness in oral cancers

Purpose: Grainyhead-like 2 (GRHL2) is one of the three mammalian homologues of Drosophila Grainyhead involved in epithelial morphogenesis. GRHL2 also controls epithelial cell proliferation and differentiation. Our objective was to evaluate the role of GRHL2 in oral carcinogenesis and the underlying mechanism. Experimental Design: GRHL2 expression was evaluated in multiple oral cancer cell lines and tissues of oral squamous cell carcinomas (OSCCs) by qRT-PCR, western blot assay, immunohistochemistry and laser-captured microdissection assay. The effects of shRNA-mediated GRHL2 knockdown were evaluated by tumor spheroid assay, colony formation assay, gene promoter luciferase assay and immunofluorescent staining and chromatin immunoprecipitation assay. In vivo the effect of GRHL2 loss on cancer cell tumorigenicity was evaluated by tumor xenograft assay. Results: GRHL2 expression was elevated in cells and tissues of oral squamous cell carcinomas (OSCCs) compared with normal counterparts. Knockdown of GRHL2 resulted in the loss of in vivo tumorigenicity, cancer stemness, and epithelial phenotype of oral cancer cells. GRHL2 inhibition decreased oral cancer cell proliferation and colony formation. GRHL2 regulated the expression of miR-200 family and Octamer-binding transcription factor 4 (Oct-4) genes through direct promoter DNA binding. Overexpression of miR-200 genes in the oral cancer cells depleted of GRHL2 partially restored the epithelial phenotype, proliferative rate and cancer stemness. Conclusion: GRHL2 plays pivotal role in the maintenance of the transformed phenotype in OSCCs. Downregulation of GRHL2 leads to the decrease of tumorigenicity, cancer stemness of oral cancer cell, in which miR-200 and Oct-4 genes partially mediate the tumorigenic effects of GRHL2 in OSCC. This study was supported in part by the grants R56DE024593 and Jack Weichman Endowed Fund. Citation Format: Wei Chen, Shebli Mehrazarin, Ki-Hyuk S Shin, Yi-Ling Lin, Reuben H. Kim, No-Hee Park, Mo K. Kang. Grainyhead-like 2 (GRHL2) regulates epithelial plasticity and stemness in oral cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2097. doi:10.1158/1538-7445.AM2015-2097