OBJECTIVETo study the differential expression of four TRAIL receptors on bone marrow mononuclear cells (BMMNC) from multiple myeloma (MM) patients and myeloma cell line KM3 cells, to compare their altered expressions after chemotherapy and to explore the mechanisms by which TRAIL selectively kills tumor cells.

METHODSSemi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry were used to investigate the expression of four TRAIL receptors on BMMNCs in 23 MM patients, KM3 cells and 15 controls, and the changes of their expression pattern after chemotherapy and after incubation of KM3 cells with sub-clinical concentration of doxorubicin.

RESULTSDR4 and DR5 were highly expressed on KM3 cells with no expression of DcR1 and DcR2. Expressions of DR4 and DR5 on BMMNCs from MM patients were higher and expression of DcR1 and DcR2 were lower than that of controls (P < 0.05). The expression of DR5 on MM and KM3 cells was up-regulated after chemotherapy and exposure to doxorubicin (P < 0. 05).

CONCLUSIONSThe expressions of four TRAIL receptors on myeloma cells and normal controls were different, which might account for the selective killing effect of TRAIL on MM cells. Up-regulated DR5 on KM3 cells after incubating with doxorubicin and after chemotherapy suggests the cytotoxic agents might enhance the apoptosis of MM cells.