The mechanism by which K-CAR T-cells repress tumor growth may not be a single mode, since reduced expression of HERV-K in tumor biopsies of the treated mice led to downregulated expression of HERV-K, and this was accompanied by upregulation of p53 and downregulation of its inhibitor MDM2, as well as decreased expression of p-ERK, compared with controls. This evidence concerns the gene MDM2 and neoplasm.