Epigenetic inactivation of the MIR34B/C in multiple myeloma

Abstract

We postulated that MIR34B/C, a direct transcriptional target of TP53, might be inactivated by promoter hypermethylation in multiple myeloma (MM). MIR34B/C promoter methylation was studied in 8 normal marrow controls, 8 MM cell lines, 95 diagnostic, and 23 relapsed/progressed MMsamples by methylation-specific PCR. MIR34B/C was methylated in 6 (75.0%) MM cell lines but not normal controls. 5-Aza-2′-deoxycytidine led to MIR34B/C promoter demethylation and MIR34B reexpression. Moreover, restoration of MIR34B led to reduced cellular proliferation and enhanced apoptosis of myeloma cells. In primary samples, methylation of MIR34B/C occurred in 5.3% at diagnosis and 52.2% at relapse/disease progression (P