Caracterização funcional de uma nova proteína SET humana, SETD4 envolvida na proliferação de células de câncer de mama

Abstract

Cancer is comprised of a multitude of epigenetic abnormalities, including the global loss and regional gain of DNA methylation as well as alterations in histone methylation. Deregulation of some histone methyltransferases has been associated with cancer aggressiveness. In this study, we aim to analyze the expression and functional role of a new human methyltransferase, SETD4 in breast cancer. The SETD4 protein contain a SET domain, highly conserved domain found in histone/lysine methyltransferase. Quantitative real-time PCR (qPCR) analysis showed elevated expression levels of SETD4 in several breast cancer cell lines. SETD4 expression was confirmed by western blot analysis revealing a correlation between high expression of SETD4 and a lack of the estrogen and progesterone receptor in breast tumors. Cell fractionation studies and confocal immunofluorescence microscopy revealed the nuclear and cytoplasmic localization of this new protein. Functional studies found that SETD4 knockdown decreased the ability of the cells to proliferate and form colony. In addition, SETD4 reduction delayed the G1/S cell cycle transition without affecting apoptosis. Furthermore, knockdown of SETD4 showed decreased cyclin D1 expression, suggesting the involvement of SETD4 in cell cycle regulation. In contrast, SETD4 overexpression increased cell proliferation and induced G1/S cell cycle progression. These data indicate that SETD4 plays a crucial role in breast carcinogenesis and could be a novel molecular target for the development of new strategies for the diagnosis and treatment of breast cancer.