Studies on the Mechanism of the Stimulatory Effect of Lethally Irradiated Cells on Tumor Inocula 1

Abstract

Summary

Addition of lethally irradiated cells or “nuclei” prepared from them to tumor inocula increased the frequency of tumor takes and decreased latency and host survival. In previous studies, sonication of either cells or “nuclei” abolished this effect. It was postulated that the stimulatory effect is due to the transfer of nutrients from the membrane-bound structures in the lethally irradiated preparations to living tumor cells prior to the establishment of a vascular supply. In the current studies it was found that sonication of ⁷⁵Se-methionine-labeled lethally irradiated cells or “nuclei” resulted in a more rapid disappearance of radioactivity from the site of injection and reduced the uptake of the label into simultaneously injected viable tumor cells. Similarly, tumors developing from inocula containing sonicated ¹²⁵IUdR-labeled irradiated cells retained less radioactivity than tumors which developed from inocula containing unsonicated lethally irradiated cells.