Natural killer cell activity of prostatic cancer patients

Natural killer (NK) cell activity of prostatic cancer patients was compared with that of control groups by the radioactive indium (111In) release assay using the K562 and H494 cells as targets. Patients suffering from advanced prostatic cancer (clinical stages C and D) exhibited significantly lower NK activity against K562 cells (28 +/- 18%) than did the normal group (41 +/- 19%). The lower NK activity of these patients is not related to their age, since patients in the same age range with localized cancer (stage B) or benign prostatic hyperplasia did not show low NK activity (37% +/- 19%). This lower NK activity is not due to a depletion of the NK cell precursor population, since the NK activity of advanced cancer patients improves significantly after in vitro incubation with interferon. The NK activity of normal subjects or patient groups showed wide fluctuations during the 18-month observation period. Because of these interassay variations, it is necessary to use standard control subjects during long-term monitoring of the NK activity of the patients.