Human colon cancer cells differ in their sensitivity to curcumin-induced apoptosis and heat shock protects them by inhibiting the release of apoptosis-inducing factor and caspases.

Mild heat treatment induced the expression of heat shock protein-70 (hsp70), hsp90 and hsp27 in two human colon cancer cell lines, one derived from primary tumor, SW480, and the other derived from the secondary lymph node tissue, SW620, of the same patient. SW620 cells appear to be more sensitive to curcumin-induced apoptosis. Heat shock protects both the human colon cancer cells from curcumin-induced apoptosis. Heat shock prevented, at least in part, the release of apoptosis inducing factor from mitochondria induced by curcumin although the release of second mitochondria derived activator of caspase and cytochrome c was unaffected in both the cells. Moreover, heat shock reduced curcumin-induced activation of caspases 9 and 3 but not 8.