Inhibition of proliferation by retinoids, cytokines and their combination in four human transformed epithelial cell lines.

Various combinations of retinoids and cytokines were examined for their synergistic effect on inhibition in proliferation of four human transformed epithelial cell lines, MCF7 (mammary carcinoma), SCC4, SCC15 and A431 (squamous cell carcinomas). Synergism depended on the cell line tested, to some degree on the specific retinoid but particularly on the type of cytokine used. IFN alpha had the widest spectrum of activity. IFN gamma, TNF-alpha, IL-1, EGF and TGF-beta also exerted a synergistic effect on proliferation inhibition in certain cell lines, whereas G-CSF was inactive. Association of retinoids and cytokines represents a new approach to antitumor chemotherapy.