Dexamethasone-induced increase in in vitro clonogenicity of human neoplasms

The addition of the corticosteroid hormone, dexamethasone, to the culture medium results in a significant enhancement of tumor colony growth in the human tumor clonogenic assay. Taking 20 as the mean minimum number of colonies per dish that allows evaluation of 122 cultured tumors, 67 were fully evaluable in the presence of dexamethasone whereas only 34 were evaluable when it was omitted. The addition of dexamethasone significantly (P less than .05) increased the number of evaluable tumors by 23. Tumors cultured included those of the breast, lung, colon, ovary, kidney, and stomach. The response to dexamethasone showed a dose-response relationship over a concentration range typical of corticosteroid receptor-mediated reactions, and it appeared to be steroid specific. Possible mechanisms for this hormone effect are discussed.