[Secretion of prostaglandin type E (PGE) by tumor cells of Syrian hamsters in in vitro contact with natural killers].

The ability of Syrian hamster tumor cells of the same origin but with different degrees of malignancy to secrete prostaglandin E (PGE) was studied following their in vitro contact with Syrian hamster natural killer cells (NK cells). Syrian hamster NK cells were shown to lose significantly cytotoxic activity after their contact with malignant tumor cells. Short-term in vitro contact of malignant tumor cells with human and Syrian hamster NK cells resulted in a rapid PGE secretion into the culturing medium. PGE was determined in the culturing medium, using the biological test, described in the paper, or direct radioimmunoassay. No PGE secretion was observed after the treatment of tumor cells with indomethacin. It is assumed that PGE secretion by malignant tumor cells is one of the mechanisms of their protection against natural killer cells.