Modulatory effects of oestrogen on immunological responsiveness. II. Suppression of tumour-associated immunity in patients with prostatic cancer

The effect of estrogen (diethylstilbestrol diphosphate, DES-P) on immunity to tumor-associated antigens in patients with prostatic cancer was evaluated by leucocyte adherence inhibition, a suggested in vitro correlate of cellular immunity. Significant (P < 0.05) suppression of immunity to malignant prostate was observed in 30 out of 31 patients following pre-incubation of their leucocytes with therapeutically significant levels of DES-P. Suppression of tumor-associated immunity by exogenous estrogen provides further evidence to earlier studies demonstrating estrogenic suppression of non-specific cellular responsiveness evaluated by mitogen-induced lymphocytic blastogenesis, and for concern over the efficacy of estrogenic therapy and its adverse effect in the treatment of patients with hormone-dependent tumors and responsive diseases. The reduced efficiency of immunosurveillance of tumors and underlying infectious agents may contribute to the exacerbation of disease. While speculative, these observations may also be relevant to the possible association between uterine cancer and prolonged administration of DES and the development of vaginal tumors in offspring found in association with maternal ingestion during pregnancy.