Effects of granulocyte-macrophage colony-stimulating factor on in vitro growth of human solid tumors

Solid tumor biopsies from 33 patients were tested in vitro to evaluate the growth modulatory effects of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF). In 29 of 33 studies (88%), addition of GM-CSF either had no effect on in vitro growth, or induced growth inhibition. While significant growth inhibition was observed in 10 studies, marked inhibition was only observed in three studies. However, all dose-response curves were usually flat, suggesting indirect effects. Moderate growth stimulation was observed in four instances, which may have been due to residual granulocyte-macrophage progenitors within the biopsies. We conclude that GM-CSF has little or no growth-modulatory effect on most nonhematopoietic neoplasms. The primary role of GM-CSF in patients with solid tumors appears to be in prevention or reversal of myelosuppression associated with therapy. Thus, while GM-CSF seems unlikely to have a role in monotherapy of cancer, it is also unlikely to have its utility compromised by enhancement of tumor growth.