THU491 GRHL2 Overexpression In Breast Cancer Progression

Disclosure: C. Zheng: None. K.O. Allen: None. R. Reese: None. N.M. Solodin: None. J. Vera: None. S. Mcilwain: None. T. Liu: None. E.T. Alarid: None. Metastasis constitutes the permissive migration and growth of cancerous cells from the primary tumor to a distant location in the body. Epithelial to mesenchymal transition (EMT) is implicated in metastasis as it allows for cells to abandon an epithelial identity, adopt a mesenchymal phenotype, become migratory, and promote tumor progression. Grainyhead-like protein 2 (GRHL2) is a nuclear transcription factor responsible for driving epithelial cell fate. By regulating epithelial differentiation and integrity in estrogen receptor (ER) positive breast cancer, GRHL2 suppresses EMT, and as such, it was long thought to act primarily as a tumor suppressor. However, clinical evidence contradicts its tumor suppressive role in that patients expressing high levels of GRHL2 have a significantly lower probability of long-term recurrence free survival compared to low levels of GRHL2, and high levels of GRHL2 are also associated with high grade tumors. To better understand this discrepancy, a tetracycline (tet) inducible GRHL2 overexpression model in the ER-positive breast cancer MCF7 cell line was developed to assess cancer associated phenotypes and the transition between epithelial and mesenchymal states. Dose response and time course studies were performed to determine optimal GRHL2 induction in our tet-inducible model using immunofluorescent microscopy and Western blot analysis. Gene expression analyses was performed to assess representative genes associated with epithelial and mesenchymal states, and the intermediates between them known as hybrid or partial EMT. Interestingly, immunocytochemistry identified that the overexpression of GRHL2 induces the late EMT marker, vimentin, despite the inhibition of migration in the epithelial dominant MCF7 cell line. Together, these data indicates that GRHL2 overexpression leads to a complex phenotype that cannot be defined by a binary epithelial or mesenchymal state. Further analyses are aimed at understanding the pleiotropic roles GRHL2 plays in ER+ tumor progression. Presentation: Thursday, June 15, 2023