OBJECTIVETo investigate the effects of CD45 expression on induction of apoptosis in multiple myeloma cells.

METHODSMelphalan was used to induce myeloma cell line U266 apoptosis. Serum-free culture was used to induce CD45RB gene or empty plasmid transfected U266 apoptosis. The glucose-free culture was used to induce high CD45 (CD45(hi)) or low CD45 (CD45(low)) expression AMO1 apoptosis. Intraperitoneal inoculation was used to compare the survival of CD45(-) or CD45(+) U266 cells in mice. The number of apoptotic cells and mitochondrial membrane potential (MMP) was detected by flow cytometry. Western blotting was used to detect the cytochrome C release from mitochondrial and caspase-9 activation.

RESULTSMelphalan treatment induced 45% of CD45(+) and 30% of CD45(-) U266 cells apoptosis. Compared with the CD45(low) AMO1 cells, CD45(hi) cells were more susceptible to apoptosis. In serum-free culture for five days, 60% of CD45RB transferred U266 cells underwent apoptosis, while in the empty plasmid transfected ones, apoptotic cell number was not significantly increased. The survival time of CD45(-) U266 cells in the SCID-hIL-6 mice was 5 times that of CD45(+) cells. After melphalan treatment, 60% of the CD45(+) U266 cells lost MMP, while only 30% of CD45(-) U266 cells, and 10% of control cells did so. After UV irradiation, CD45(+) U266 cells mitochondria released more cytochrome C, leading to more caspase-9 activation.

CONCLUSIONCD45 expression is involved in mitochondria-mediated apoptotic process and increases apoptotic sensitivity of myeloma cells under a variety of stimulation.