Characterization of the function of m6A regulation in breast cancer

Abstract

Breast cancer is currently the most diagnosed cancer in women and classified among the most metastatic cancers. Specifically, breast cancer originates within the epithelial cells of the mammary gland, a highly dynamic and stem cell abundant region that develops extensively through puberty and pregnancy. In recent years, researchers have begun focusing on how mammary stem cells (MaSCs) are regulated during mammary gland development and breast cancer progression. One approach involves investigating the role of internal RNA modifications in regulating breast cancer maintenance. N6-Methyladenosine (M6a) is currently the most abundant internal mRNA modification, however despite being highly conserved, researchers are conflicted over its functional significance in disease. The discovery of m6A regulating proteins has been a significant achievement in this area of study, with recent emphasis being placed on the role of m6A “readers” in embryonic development, regulating proteins that interpret and direct m6a methylated transcripts accordingly. Among the m6A readers, YTHDF2 (DF2) has been recently shown to have irreplaceable importance in the regulation of m6A, yet it remains largely uncharacterized in breast cancer. In this study, we examine the role of DF2 within the context of breast cancer, specifically by testing its effects on tumor cell proliferation, stemness, and metastasis in vitro. We find that upon knockdown of DF2 in human and mouse mammary tumor cells, overall tumor cell proliferation, stemness, and invasion all increase, a finding that was supported by preliminary bioinformatics analysis of m6A expression in clinical breast cancer dataset samples. Additionally, DF2 KD cells showed increased expression of transcription factors essential to maintaining the stem cell phenotype, suggesting a role for DF2 to normally downregulate stem promoting transcripts. Although more research is necessary to determine how DF2 may be regulating processes such as stemness or metastasis, our results suggest a possible tumor suppressor-like role within the context of breast cancer.