Diallyl disulfide induces apoptosis of human colon tumor cells

The present studies compared the effects of various oil-soluble compounds containing allyl and disulfide groups on the proliferation of cultured human colon tumor cells (HCT-15). Diallyl disulfide (DADS) was more effective in inhibiting the growth of HCT-15 cells than isomolar concentrations of S-allyl cysteine, dipropyl disulfide (DPDS), allyl chloride, allyl glycidyl ether and allyl alcohol. These studies clearly demonstrate the importance of both the diallyl and the disulfide groups in DADS. Treatment of HCT-15 cells with 100 μM DADS increased the intracellular calcium levels by 40%,while DPDS caused only a 12% increase in intracellular calcium. Exposure to 100 μM DADS or more, but not DPDS, caused the cells to undergo apoptosis as determined by morphological changes and DNA fragmentation. A positive correlation (r = 0.944) was found between DADS-induced DNA fragmentation and its ability to increase intracellular free calcium levels. The widespread effectiveness of DADS was evident by its ability to inhibit the growth of human colon (HCT-15), skin (SKMEL-2) and lung (A549) tumor cell lines.