Indomethacin enhancement of lymphocyte responses to phytohemagglutinin in breast, stomach and colorectal cancer patients.

The effect of indomethacin, a prostaglandin synthetase inhibitor, on lymphocyte responses to phytohemagglutinin (PHA) was studied in 111 breast, stomach and colorectal cancer patients. Indomethacin exerted no mitogenic activity and the ethanol in which the indomethacin was dissolved produced no significant effect on the lymphocyte responses to PHA. Compared with the control group (13 healthy subjects and 30 patients with benign disease), indomethacin significantly enhanced the lymphocyte responses to PHA in the cancer patients. The degree of enhancement induced by indomethacin was independent of the primary site of the tumor, but was associated with tumor load. A significant inverse correlation was observed between the degree of enhancement and that of the original lymphocyte responses to PHA. Sequential determinations of the degree of enhancement in selected stomach and colorectal cancer patients revealed that it fell to a low level after curative tumor resection.