Apoptosis Induction through RASSF1A Upregulation of FasL

RASSF1A is a tumor suppressor that has been studied in great detail to determine its role downstream of death receptors. It has been shown that RASSF1A has been silenced by promoter methylation in many tumors and cell lines, including those of lymphoma and leukemia origin; however, studies have not clearly demonstrated its role in regulating apoptosis through enhanced expression of death receptors. Our studies have shown that RASSF1A overexpression, which was achieved through stable and transient transfections of Jurkat cells with RASSF1A DNA, upregulates FasL expression. The secreted FasL binds to the Fas receptor, which induces apoptosis through a biochemical pathway in Jurkat cells, a human leukemia cell line. Transient transfections were achieved through the use of Turbofectin to minimize the amount of unprogrammed cell death. Immobilized α-CD3 antibody plus PMA was used to stimulate the Jurkat cells. In order to measure the amount of increase in apoptosis due to FasL production, we performed immunoblotting with α-PARP antibodies to detect cleavage, and transcriptional reporter/luciferase assays using promoter regions of FasL or transcription factor binding sites. Our experiments have shown that cells transfected with RASSF1A DNA expressed more FasL, and as a consequence induced more apoptosis.