Caspase inhibitor BD-fmk distinguishes transforming growth factor �-induced apoptosis from growth inhibition. Cell Growth Differ

Transforming growth factor 13(TGFII) is essential for immune regulation and growth control. TGFI3 has previously been shown to inhibit cell growth as well as induce cell death in lymphocytes, although the mechanisms controlling these processes are not well understood. The mouse pie-B lymphoma cell line WEHI 231 was used to examine the mechanisms of TGFfi-mediated growth inhibition and apoptosis. TGFII inhibits the growth of WEHI 231 cells in a dose-dependent manner however, a decrease in viabilfty is also observed, which is indicative of increased cell death. TGFI3 induces oligonucleosomal DNA ladder formation in a dose-dependent manner, indicating the mechanism of cell death is via apoptosis. The broad spectrum caspase inhibitor BD-fmk, but not tetrapeptide inhibitors of specific caspases, completely blocks TGFI3-induced apoptosis while maintaining cellular viability. BD-fmk, however, has no effect on TGFfi-lnduced growth inhibition. The ability of TGFI3 to down-regulate cyclin A-associated kinase activity, postulated to mediate TGFfi growth inhibition, is not affected by the caspase inhibitor BD-fmk. These results suggest that caspases do not regulate cell cycle mediators of growth and provide the first demonstration that a pharmacological inhibitor of TGFI3-induced apoptosis is capable of distinguishing growth inhibitory from apoptotic pathways