OBJECTIVETo investigate the expression of miR-21 and miR-30b in multiple myeloma (MM).

METHODSPeripheral blood mononuclear cells from patients with MM were cultured at 2.5 x 10(6) cells/ml in alpha-MEM supplemented with 10% of fetal bovine serum, antibiotics, RANKL (50 ng/ml), and macrophage colony-stimulating factor (25 ng/ml) for 10 to 14 days to obtain osteoclasts with bone-resorbing activity. Primary myeloma cells were purified from 12 MM patients. Of them, 8 samples were cocultured with osteoclasts and 4 as noncocultured control. The expression of miR-21 and miR-30b was detected by real-time PCR.

RESULTSThe viability of MM cells recovered from cocultures was higher than those of noncocultured control. After cocultured with osteoclasts, primary myeloma cells from eight patients exhibited a 1.3- 5.9-fold increase in miR-21 expression and 1.38- 4.32-fold decrease in miR-30b expression compared with controls. In highly purified plasma cells from 3 healthy subjects, 12 MM patients and 11 MM cell lines, the expression of miR-21 was 1.9 +/- 0.8, 6.5 +/- 4.9 and 35.1 +/- 36.2, respectively; the expression of miR-30b was 13.6 +/- 1.8, 7.2 +/- 6.3 and 4.5 +/- 1.9, respectively.

CONCLUSIONSmiR-21 acts as an oncogene and miR-30b a tumor suppressor gene in MM.