Role of hormones in growth kinetics of renal cell carcinoma in vitro.

Medroxyprogesterone acetate has been used to treat metastatic renal cell carcinoma largely because of its observed inhibitory effects on the growth of estrogen-induced tumors in male Syrian golden hamsters. The absence to date of any successful, established chemotherapeutic regimen in the management of metastatic renal cell carcinoma has led to the continued application of medroxyprogesterone acetate in the majority of patients with this disease because of the occasional regression witnessed (particularly in male patients) and the absence of untoward side effects. To examine the mechanism of action of medroxyprogesterone acetate renal cell carcinoma tumor cells from a patient who had responded to medroxyprogesterone acetate therapy were established in tissue culture. Cells were cultured in control medium, and in the presence of therapeutic and pharmacologic levels of medroxyprogesterone acetate. Tumor cell growth kinetics were determined by the incorporation of 3H thymidine. There was no growth inhibition effected by medroxyprogesterone acetate at therapeutic or pharmacologic levels. Therefore, the proposed salutary effect of medroxyprogesterone acetate in regression of metastatic renal cell carcinoma results from factors other than direct inhibition of renal cell carcinoma growth.