Abstract 5024: Epigenetic regulation of cancer stem cell states in a p53/PTEN inactivated mammary epithelial cells.

Abstract

Abstract Inactivation of the tumor suppressors, TP53 and PTEN in pre-neoplastic lesions has been implicated in tumor progression as well as in regulation of normal and malignant stem cell self-renewal. Down regulation of both p53 and PTEN in non-transformed MCF10A cells synergized to expand the cancer stem cell compartment transforming these cells and generating an EMT phenotype in vitro which generated highly metastatic tumors when injected in NOD/SCID mice. These tumors could be fractionated based on their expression of CD49f and EPCAM. Gene expression analyses of these sub-fractions demonstrate an EMT gene signature in CD49f+/EPCAM- and CD49f-/EPCAM- cell populations. These findings are also supported by DNA methylation analyses. Although CD49f+EPCAM+ cell population express epithelial (MET) gene signature, these cells also generate tumors in mice and give rise to cells with EMT phenotype. Interestingly CD49f+EPCAM+ subpopulation expresses higher ALDH than other two subpopulations with EMT phenotype. Therefore we propose that breast CSCs may exist in two states; EMT state may be represented by CD49f or CD44 and MET state by ALDH expression. Consistent with our hypothesis, ALDH-positive cells compared to ALDH-negative cells within the CD49f+EPCAM+ phenotype have greater capacity to generate CD49f+/EPCAM- phenotype upon IL6 or TGF-b stimulation. Interestingly blocking IL6 and TGF-b in CD49f+/EPCAM- cell population results in MET-CSC phenotype characterized by ALDH expression. It is well known that EMT is characterized by reversible epigenetic changes and therefore we hypothesized that these epigenetic changes might be involved in acquisition of different CSC states. Our results suggest that interplay between genetic and epigenetic changes during malignant transformation of mammary epithelial cells may activate multiple signaling cascades resulting in expansion of stem cells which display an EMT phenotype. Furthermore, these studies provide a strong rationale for the development of alternative therapeutics which are able to target these different states of cancer stem cells. Citation Format: Maria Ouzounova, April Davis, Gwangil Kim, Fayaz Malik, Ahmed A. Quraishi, Shawn G. Clouthier, Max S. Wicha, Hasan Korkaya. Epigenetic regulation of cancer stem cell states in a p53/PTEN inactivated mammary epithelial cells. [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 5024. doi:10.1158/1538-7445.AM2013-5024