Methylation status of nine tumor suppressor genes in multiple myeloma

Aberrant methylation in promoter-associated CpG islands has been recognized as a major mechanism for tumor suppressor gene silencing in several malignancies. We determined the methylation status of nine tumor suppressor genes in 68 newly diagnosed MM patients by methylation-specific PCR. The frequency of promoter hypermethylation for individual genes was: CDH1, 50%; p16 ^INK4a , 42.8%; p15 ^INK4b , 16.2%; SHP1, 14.7%; ER and BNIP3, 13.2%; RARβ, 11.8%; DAPK 5.9%; and MGMT 0%. Overall, 79% of patients presented at least one hypermethylated gene. By univariate analysis, hypermethylation of DAPK (P < 0.001) and RARβ (P = 0.01) genes were identified as adverse prognostic features. Median OS of patients with hypermethylation in DAPK (4 months) and RARβ (34 months) was significantly lower than in patients without hypermethylation (median survival not reached), with values of P < 0.001 and P = 0.01, respectively. Our data suggest that DAPK and RARβ hypermethylation are adverse prognostic factors in MM. The relevance of these findings as poor prognosis indicators requires confirmation in a larger sample with longer follow-ups.