BIS overexpression does not affect the sensitivity of HEK 293T cells against apoptosis

Abstract

BCL-2 interacting cell death suppressor (BIS), also known as BAG3, has been known to function as an anti-stress or anti-apoptotic protein. Due to high levels of BIS expression in most of cancer cell lines, strategies to suppress BIS and any subsequent increased sensitivity to apoptosis are usually employed in conjunction with the pro-survival activity of BIS. To overcome the limitations in verifying a substantial level of expression for BIS, here we established BIS-overexpressing 293T cells following retroviral transfection and subsequent selection under puromycin. In a western assay, BIS expression levels were increased about 2.2-fold in selected cells (BIS-293T) compared with that in control cells (CON-293T). There was no difference in either cell growth rate or in cell cycle progression between the two groups. In addition, the susceptibilities of BIS-293T cells were not noticeably different from those of CON-293T cells following treatment with several apoptotic stimuli: cisplatin, VP-16, hydrogen peroxide, KRIBB11 (HSF1 inhibitor), AT-101 (pan-Bcl-2 inhibitor) or staurosporine (PKC inhibitor). Both cells revealed similar expression profiles of Bcl-2 family proteins, cleaved PARP and lipidation of LC3 upon AT-101 treatment, which indicate that BIS overexpression affect neither apoptosis nor autophagy induction upon AT-101 treatment in 293T cells. We further showed that inhibition of autophagy by chemical inhibitor attenuates AT-101-induced apoptosis, which is inconsistent with previous reports of the cytoprotective effect of autophagy that is induced by AT-101 in several types of cancer cells. Taken together, our results suggest that the cellular phenotypes determined by BIS and AT-101 treatment might be different between cancer cells and non- cancer cells and defining the molecular basis for such differences will require further study.