sentences:  The expression-deficient "MLH1" gene could then be carried along as a selectively neutral or only slightly deleterious passenger (hitch-hiker) gene when the mutated stem cell generates an expanded clone.The continued presence of a clone with an epigenetically repressed "MLH1" would continue to generate further mutations, some of which could produce a tumor.In a cancer, multiple DNA repair genes are often found to be simultaneously repressed.