As an anticancer therapeutic, Interferon-alpha (IFN alpha) is used to treat a number of malignancies. However, the application of IFN alpha is restricted mostly due to its high toxicity. Therefore, novel combination therapeutic regimens are required to decrease the toxicity of IFN alpha and enhance its efficacy. Here we show that the treatment of p53-deficient human non-small lung carcinoma H1299 cells with IFN alpha in combination with an inhibitor of MDM2, Nutlin-3a, synergistically affects the proliferation of cancer cells. Importantly, Nutlin-3a was able to reduce the effective dose of IFN alpha about 3.4 times. Strikingly, this phenomenon is p53-independent, because H1299 cells lack p53, but is highly dependent on MDM2 because its ablation makes tumor cells completely insensitive to IFN alpha alone or in combination with Nutlin-3a. On the contrary, overexpression of MDM2 makes H1299 cells more susceptible to both IFN alpha and IFN alpha/Nutlin-3a treatments. Mechanistically, treatment with combination of IFN alpha and Nutlin-3a attenuates cyclin D1/CDK4 on the protein level and hence blocks cell cycle progression. This mechanism may be responsible, at least in part, for the anti-proliferative effects on H1299 cells observed. Our data suggest that the expression of MDM2 confers sensitivity of cancer cells to IFN alpha/Nutlin-3a treatment. Moreover, our data also confirm positive effect of Nutlin even on p53-deficient neoplasms. (C) 2017 Elsevier Inc. All rights reserved.