The present invention provides for methods and compositions for treating cancer. A subject having cancer is administered an interferon and an inhibitor of mitogen-activated protein kinase (MAPK) signaling pathway. The combination of the interferon and the inhibitor of the MAPK pathway produces a synergistic effect on the cancer compared to the effect of the interferon or the inhibitor of the MAPK pathway alone. The activity of the interferon pathway, interferon expression levels and/or interferon locus copy number can be used as biomarkers for treatment of cancer by MAPK pathway inhibitors.
