Synergistic anti-tumor effect of 13-cRA and IFN-alpha/beta in mouse renal cell carcinoma.

The synergistic anti-tumor effect of 13-cis retinoic acid (13-cRA) and interferon-alpha/beta (IFN-alpha/beta) was investigated using a highly metastatic mouse renal cell carcinoma cell subline (RenCa/F). Although 13-cRA inhibited tumor growth in vivo as well as in vitro, IFN-alpha/beta did not. Combined administration of 13-cRA and IFN-alpha/beta significantly enhanced the anti-tumor effect of 13-cRA. The retinoic acid receptor (RAR)-alpha and RAR-gamma were expressed in RenCa/F cells. Treatment with IFN-alpha/beta did not influence the expression level of these receptors at the mRNA level, which suggests that the synergism of 13-cRA and IFN-alpha/beta is not mediated through the RAR.