3-m-bromoacetylamino benzoic acid ethyl ester: A new cancericidal agent that activates the apoptotic pathway through caspase-9

The mechanism underlying the cancericidal activity of 3-m-bromoacetylamino benzoic acid ethyl ester (3-BAABE) was investigated. 3-BAABE exerted a stro ng cancericidal effect on human leukemia and lymphoma cells (IC50 < 0.2 <mu >g/mL) and on cell lines of prostate, colon, ductal, and kidney cancer (IC5 0 0.8 to 0.88 IJ mug/mL). Multiple drug resistance (MDR) had no effect on t he susceptibility of human lymphoma cells to 3-BAABE, since Daudi/MDR20 and wild-type Daudi cells had a similar susceptibility to the cytotoxic effect of 3-BAABE. The cancericidal effect of 3-BAABE, which was not associated w ith changes in the cell cycle, was mediated by apoptosis. Thus, cells expos ed to 3-BAABE displayed the DNA fragmentation ladder characteristic for apo ptosis, associated with a marked increase of the activity of apoptosis effe ctor caspases-3 and -6, which was followed by proteolytic cleavage of DNA f ragmentation factor (DFF) and poly(ADP-ribose) polymerase (PARP). Exposure of tumor cells to 3-BAABE increased the activity of apical caspase-9, but h ad no effect on caspase-8. Complete inhibition of 3-BAABE-induced apoptosis was exerted by LEHD-FMK, a caspase-9 inhibitor. DEVD-FMK, a caspase-3 inhi bitor, and VEID-FMK, a caspase-6 inhibitor, partially inhibited 3-BAABE-ind uced apoptosis, whereas exposure to IETD-FMK, a caspase-8 inhibitor, had no effect, The fragmentation and elevated activity of caspase-9 in 3-BAABE-tr eated cells and the fact that only an inhibitor of caspase-9 abrogated 3-BA ABE-induced apoptosis indicate that 3-BAABE is a distinctive compound that elicits apoptosis through a pathway that is limited specifically to activat ion of apical caspase-9. (C) 2000 Elsevier Science Inc.