Pheophorbide a, a moiety of chlorophyll a, induces apoptosis in human lymphoid leukemia Molt 4B cells

The exposure of human lymphoid leukemia Molt 4B cells to pheophorbide a (PP B a), a moiety of chlorophyll a, led both to growth inhibition and inductio n of programmed cell death (apoptosis). The growth inhibition by PPB a was much stronger than that by chlorophyll a. Morphological change showing apop totic bodies was observed in the Molt 4B cells treated with PPB a. The frag mentation by PPB a of DNA to oligonucleosomal-sized fragments, that are cha racteristics of apoptosis, was observed to be concentration- and time-depen dent. These findings suggest that growth inhibition by PPB a of Molt 4B cel ls results from the induction of apoptosis and that PPB a, moiety of chloro phyll a, is essential for exertion of antitumor and apoptosis-inducing acti vity in these cells.