Both genotypes responded to MEK + CDK4/6 inhibition (Fig. 5a–c and Extended Data Fig. 4a); however, ΔS tumors uniquely showed induction of necrosis detected by ultrasound (Fig. 5b,c), which was preceded by an early reduction in tumor size, increase in CD3e+ T-cell infiltration and engagement of an antitumor myeloid cell phenotype (Fig. 5d,e and Extended Data Fig. 4b–e). Here, MAP2K7 is linked to neoplasm.