Fig. 5.

Synergistic cytotoxicity between arsenic and either PMA or bryostatin 1 (Bryo). (A) PMA or byrostatin 1 at the doses used did not prevent cell proliferation. Without arsenic, the cells continued proliferation in the presence of PMA or bryostatin 1 in absence (Left) or presence (Right) of NAC. NAC had mild toxicity to NB4 cells. (B Left) Synergistic toxicity is evident in cells pretreated with arsenic and then exposed to PMA or byrostatin 1, as compared with cells pretreated with arsenic only. (Right) NAC blocks the synergistic toxicity. (C) NAC decreased arsenic-induced ROS signals. After the addition of 1 nM bryostatin, the arsenic-treated cells showed significant induction of chemiluminescence of luminol plus HRP than those cells coincubated with NAC.