Effect of tumor excision on NK cytotoxic activity and formation of metastases of Bomirski melanoma in hamsters.

The growth of transplanted Bomirski melanoma in hamsters is accompanied by the decrease of natural killer cytotoxic activity and the formation of metastases. The excision of primary tumors was carried out to examine what was the effect of the growing tumor and its metastases on the host's NK activity. It was found that the excision of primary tumor caused increased NK cytotoxic activity in comparison to that of nonoperated animals although it was still lower than that of healthy hamsters. It is concluded that both, a growing tumor and metastases, exert suppressive effects on NK activity and those effects add up. The pattern of metastases in operated animals was different to that observed in nontreated hamsters.