Frequent Hypermethylation of p16 and p15 Genes in Multiple Myeloma

Abstract

Both p16 and p15, encoded by the genes located on chromosome 9p21, are inhibitors of cyclin-dependent kinases (CDK4/6) and the upstream regulators of Rb function. In hematopoietic malignancies, deletion of p16/p15 locus has been shown to be highly specific to lymphoid, and more particularly from B-lineage malignancies except multiple myeloma (MM). To investigate whether these genes are inactivated by deletions, mutations, and hypermethylation of the 5′ CpG islands, we examined 12 MM patients by Southern hybridization and polymerase chain reaction–single-strand conformation polymorphism (PCR-SSCP) analysis. No deletions nor mutations of the p16 and p15 genes were found. However, hypermethylation was observed in 75% for p16 and 67% for p15 in our group of MM patients. Such high frequencies of involvement of these genes in MM make them hitherto the most common genetic abnormalities in this disease. Concomitant hypermethylation, uncommon thus far in the literature of the study of these genes, is a rather common phenomenon, occurring in 67% of our patient group. Moreover, hypermethylation of p16/p15 was associated with blastic disease and concomitant hypermethylation of both genes may be pathogenetically related to plasmacytoma development. These results indicate that these genes are important in MM pathogenesis. Here we report, for the first time in the literature, the high incidences of p16 and p15 alterations in MM, not by homozygous deletions or mutations, but solely by hypermethylation of the 5′ CpG islands, which may be a specific mechanism in this disease.

Combination of DNA methylation inhibitor 5‐azacytidine and arsenic trioxide has synergistic activity in myeloma

“…RPMI 8226 cells treated with 5-AZA exhibited much higher efficiency for the DNA demethylation at the XAF1 promoter region, as indicated by lack of methylated PCR signal after treatment with 5-AZA for 72 h. Collectively, we concluded that lack of the full-length of XAF1 transcripts, seen in XG-7 cell line, was not attributable to the deletion of the XAF1 allele. The study and other studies indicated that hypermethylation in myeloma cell lines is a prevalent phenomenon (27)(28)(29)(30).…”

Mutational and methylation analysis of the cyclin‐dependent kinase 4 inhibitor (p16INK4A) gene in chronic lymphocytic leukemia

“…p16 gene promoter methylation has been observed in solid tumors like bowel and lung cancer and glioma (41). In hematological neoplasias p16 gene promoter methylation has been described in 75% of the cases of acute lymphoblastic leukemia of B-cell type, in 61% of cases of multiple myeloma, as well as in high-grade lymphomas (17,37,40,42). In low-grade lymphomas p16 gene promoter methylation has been described in 10% of cases (11,13,37,43).…”

“…The degree of p16 gene promoter methylation is different among hematologic malignancies. More specifically p16 gene methylation has been reported in 75% of cases of B cell precursor acute lymphoblastic leukemia, in 61% of cases of multiple myeloma and in 14% of cases of B cell non-Hodgkin lymphomas (11,(14)(15)(16)(17)(18).…”

Methylation status of fragile histidine triad (FHIT) gene and its clinical impact on prognosis of patients with multiple myeloma

“…Methylation of TSG has recently been investigated in MM. It has been reported that the p14 ARF , p15 INK4B , p16 INK4A , and DAP kinase genes are methylated in about 20-70% of MM cases (9)(10)(11)(12)(13).…”