Apoptosis-antagonizing transcription factor (AATF) gene silencing: role in induction of apoptosis and down-regulation of estrogen receptor in breast cancer cells.

Apoptosis-antagonizing transcription factor (AATF) is involved in transcriptional regulation, cell cycle control, DNA damage responses and in the execution of cell death programs. It also interacts directly with nuclear hormone receptors to enhance their transactivation. This study highlights the RNomics of AATF gene in the pathogenesis of breast cancer: RNA interference gave 64% reduction in AATF mRNA and 47% decline in AATF protein expression in MCF-7 breast cancer cells. Cell proliferation decreased by 41% after transfection and was accompanied by apoptosis induction in 30% MCF-7 cells. Pro-apoptotic genes (Bax, Bag4, Fas, Faslg, Fadd, Casp5, Casp6, Abl 1, Apaf1, Bcl2l 11, Card4, -6, -8, Bnip2 and Bnip3l) were up-regulated and anti-apoptotic genes (Bcl2, Mcl1dc, TNF, Pycard, Tradd, Bcl2A1 and Birc1) were down-regulated as were estrogen receptor mRNA (42%) and protein expression (30 %). In normal non-malignant mammary epithelial cells (MCF-10A) apoptosis induction was only 18% with a 9% fall in ER protein expression. Thus, AATF-silencing can be used to induce apoptosis and regulate ER expression in breast cancer cells for therapeutic interventions.