BAG-1 promotes apoptosis induced by N-(4-hydroxyphenyl)retinamide in human cervical carcinoma cells.

N-(4-hydroxyphenyl)retinamide (4-HPR) is a synthetic apoptosis-inducing retinoid with cancer chemopreventive properties and lower toxicity than all-trans retinoic acid. BAG-1 is an antiapoptotic gene that is overexpressed in cervical and other cancers. In this study, we examined whether BAG-1 can inhibit 4-HPR-induced apoptosis in the C33A cervical carcinoma cell line. Surprisingly, although it inhibited apoptosis induced by five different apoptotic stimuli, overexpression of BAG-1 enhanced apoptosis induced by 4-HPR, producing a 2.5-fold lower IC(50) of 4-HPR. The effects of BAG-1 on 4-HPR-induced apoptosis were mediated by enhancing the caspase-3 activation pathway. Deletion mutation experiments showed that the central ubiquitin homology domain of BAG-1 protein was necessary for its promotion of 4-HPR-induced apoptosis, whereas its C-terminal Hsp70/Hsc70-interacting domain was required for its inhibition of staurosporine-induced apoptosis. These in vitro results suggest that the effectiveness of 4-HPR against the development of malignancy may be due to the overexpression of BAG-1 in cancer cells.