Downregulated miR-33b is a novel predictor associated with disease progression and poor prognosis in multiple myeloma.

MiRNAs located at chromosome fragile sites play important roles in regulating critical genes associated with myeloma pathogenesis, disease progression and drug resistance. Our previous results have identified miR-33b (located in chromosome 17p) was one of the dysregulated miRNAs in the sera of newly diagnosed MM patients. However, little is known about its expression pattern in myeloma tumor cells and its prognostic value in MM patients. In the present study, we investigated the expression pattern of miR-33b in 58 newly diagnosed, 11 relapsed, 12 remission MM patients and 18 health donors by quantitative real-time PCR. Our results showed the expression of miR-33b was obviously down-regulated in newly diagnosed and relapsed MM patients compared to remission patients and health donors (p<0.001). Moreover, patients with del(13q), del(17p), t(4;14) and high-risk genetic abnormalities have lower expression levels of miR-33b compared to patients without those of abnormalities (p=0.032, 0.018, 0.034, 0.005). Survival analysis showed patients with miR-33b low expression had significantly shortened PFS (p=0.016) and OS (p=0.033) and might be associated with drug resistance to bortezomib-based treatment. Our data suggest that down-regulated miR-33b might be a novel predictor associated with disease progression and poor prognosis in MM.