Arsenic trioxide induces apoptosis in human gastric cancer cells through up-regulation of p53 and activation of caspase-3

Arsenic trioxide (As2O3) can induce clinical remission in patients sufferin g from acute promyelocytic leukemia, through induction of apoptosis and act ivation of caspases, We investigated the potential use of As2O3 in human ga stric cancer and its possible mechanisms. Human gastric cancer cell lines A GS and MKN-28 were treated with various concentrations (0.1 to 100 muM) of As2O3 for 24 to 72 hr. Apoptosis was determined by acridine orange staining , flow cytometry and DNA fragmentation. Protein levels of p53, p21(wafl/cip l), c-myc, bcl-2 and bax were detected by Western blotting. Effects of As2O 3 on caspase-3 protease activity, its protein concentration and cleavage of poly(ADP)-ribose polymerase (PARP) were also studied. As2O3 inhibited cell growth and induced apoptosis in both cell lines, though AGS cells were mor e sensitive. As2O3 induced apoptosis in AGS cells in a concentration- and t ime-dependent manner. Treatment resulted in a marked increase in p53 protei n levels as early as 4 hr. Co-incubation with p53 anti-sense oligo-nucleoti de suppressed As2O3-induced intracellular p53 over-expression and apoptosis , As2O3 increased the activity of caspase-3, with appearance of its 17 kDa peptide fragment, and cleavage of PARP, with appearance of the 85 kDa cleav age product, both in parallel with the induction of apoptosis, Both the tri peptide caspase inhibitor zVAD-fmk and the specific caspase-3 inhibitor DEV D-fmk partially suppressed As2O3-induced caspase-3 activation and apoptosis . As2O3 inhibits cell growth and induces apoptosis in gastric cancer cells, involving p53 over-expression and activation of caspase-3, The potential u se of this compound in the treatment of gastric cancer is worth further inv estigation. (C) 2001 Wiley-Liss, Inc.