Xenograft studies of KRAS-mutant HCT116 demonstrated inhibition of tumor growth by selumetinib, but little antitumor activity with MK-2206 alone (Fig. 1D; Supplementary Table S1). Combined treatment with MK-2206 and selumetinib resulted in moderate but significant increase in tumor regression over time compared with selumetinib alone...The combination therapy produced a tumor regression with statistically significant increase in the antitumor response as compared with monotherapy (P < 0.05).