POLYADENYLIC-POLYURIDYLIC ACID ENHANCES THE NATURAL CELL-MEDIATED CYTOTOXICITY IN PATIENTS WITH BREAST-CANCER UNDERGOING MASTECTOMY

Background. Surgical procedures suppress host antitumor defense mechan isms, which may increase the risk of metastatic tumor dissemination. W e have evaluated the effects of the biologic response modifier polyade nylic-polyuridylic acid (PAPU) on natural cytotoxicity in patients wit h breast cancer undergoing operation. Methods. PAPU (150 mg) or placeb o was given intravenously during the perioperative period (preoperativ e, days -1 and 0; postoperative,, days 1, 3, 5, 7, and 14). The functi on (chromium release assay) and number (flow cytometry) of natural Kil ler (NK) cells were measured before operation (days -2 and -1), on the day of operation (day 0), and after operation (days 1, 2, 4, 6, and 2 8). Results. Surgical procedures suppressed NK cell cytotoxicity in th e placebo group on postoperative days 1 (p <0.001), 4, 6, and 18 (p <0 .05) whereas inhibition on postoperative day 2 failed to reach signifi cance. PAPU abolished this immunosuppression after operation. The NK: cell activity was elevated when compared with the control group; it wa s significant (p < 0.05) on postoperative days 1, 5 4, 6, and 18. Surg ical procedures also reduced circulating NK cell numbers during the fi rst postoperative week in the placebo group; the decrease was statisti cally significant on day 4. The decrease in NK cell numbers in the PAP U group was insignificant. Conclusions. PAPU prevented the decrease in the circulating number and cytotoxic activity of NK cells that occurr ed after operation and enhanced NK cell cytotoxicity. This may have im portant implications for patients with cancer undergoing major operati on.