PURPOSE: To obtain the subject new proteinic factor, derived from a culture supernatant of an epithelial tumorous cell, having a specific molecular weight and enhancing actions on tumor cytotoxic actions of an anticancer agent and capable of suppressing adverse effects of the anticancer agent due to its ability to reduce the effective amount of the anticancer agent.

CONSTITUTION: This new proteinic factor is derived from a culture supernatant of an epithelial tumorous cell and has about 50000-55000 molecular weight measured by a get filtration method and further enhancing actions on tumor cytotoxic actions of an anticancer agent such as a tumor necrosis factor-α (TNF-α), bleomycin and cisplatin in a manner dependent on the concentration. The proteinic factor is obtained by culturing an epithelial tumorous cell (e.g. KB cell) in a culture medium containing a bovine fetal serum (FCS) and the culture medium is then removed after 2 days. A serum-free culture medium is added to carry out the culture for 2 days. The culture medium is centrifuged to collect a culture supernatant, which is then concentrated with an ultrafiltration membrane and fractionated according to an anion exchange column chromatography by using cytotoxic activities of the tumorous cell in the presence of the TNF-α as an index.