In order to investigate whether the in vivo mRNA-translated Pembrolizumab could retain the anti-cancer activities, we assessed the protective and inhibitory effects on animal survival and tumor growth, respectively, in a therapeutic human PD-1 knock in MC38 tumor bearing mouse which were weekly treated with Pembrolizumab mRNAs at the doses of 0.2, 0.6 and 2.0 mg/kg for 6 weeks, using the Pembrolizumab antibodies at 10 mg/kg as positive control, and tumor growths were recorded. This evidence concerns the gene PDCD1 and neoplasm.