LOH involving mismatch repair genes loci; some representative alterations are shown. Genomic DNA from ALL patients 63, 74, and AML patient 213 was PCR-amplified for microsatellites D3S1611, CA21, and D7S517, 3 genetic markers respectively associated with the MLH1, MSH2, and PMS2 genes, as reported in Materials and Methods. R, remission; Rel, relapse.