Alterations of p16 and p15 genes in acute leukemia with MLL gene rearrangements and their correlation with clinical features

Abstract

p16 and p15 genes are putative tumor suppressor genes located on chromosome 9p21. In acute leukemias, alterations of p16 and p15 genes have been reported to occur exclusively in lymphoid lineage. We analyzed alterations of p16 and p15 genes in 46 acute leukemias with MLL gene rearrangements by Southern blot analysis, and investigated the association with clinical characteristics. We identified homozygous deletion of p16 and p15 genes in five (19%) of 27 acute lymphoblastic leukemias (ALLs) and in two (11%) of 19 acute myeloid leukemias (AMLs). Patients with homozygous deletion of p16 and p15 genes showed higher average leukocyte counts (343 × 10⁹/l vs 271 × 10⁹/l) and lower estimated 2-year survival rates than those with normal p16 and p15 genes (14.3 vs 30.7%), although the differences were not statistically significant. In addition, we investigated mutation of p16 gene by polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) in 31 patients, but no mutation was found in the patients tested. Our results suggest that alterations of p16 and p15 genes are involved in a subset of acute leukemias with MLL gene rearrangement not only of lymphoid but also of myeloid phenotype. Homozygous deletion of p16 and p15 genes may be a possible adverse prognostic factor, although further analysis would be needed to confirm it.