OBJECTIVETo investigate the effect of all-trans retinoid acid (ATRA) and granulocyte colony-stimulating factor (G-CSF) on the growth, apoptosis, differentiation and expression of RARα2 of myeloma cells.

METHODSMyeloma cell lines OPM2 (RARα2 positive) and U266 (RARα2 negative) were treated with ATRA in the presence or absence of G-CSF. The cells were divided into 6 groups: control groups, G-CSF groups (treated with 1000 U/ml and 2000 U/ml), ATRA groups (treated with 1.0 μmol/L ATRA) and combined groups (treated with 1000 U/mL or 2000 U/mL G-CSF plus 1.0 μmol/L ATRA). The cell viability, growth and apoptosis were examined by MTT method, inverted microscopy and Annexin-V/PI staining, respectively; RARα2 expression was detected by reverse transcription PCR; morphology change was evaluated by Wright-Giemsa staining; CD49e expression were analyzed by flow cytometry.

RESULTSThe proliferation of OPM2 cells was inhibited by ATRA treatment (P<0.05) . The growth inhibition rates in combined groups were higher than corresponding single ATRA groups (P<0.05). However, the above effects in U266 cells were not significant (P >0.05). The OPM2 cell stained by Wright-Giemsa in ATRA groups showed that the cell nucleus became smaller, chromatin condensed, number of nucleolus reduced, the volume of cytoplasm increased and the cytoplasm became dark blue. Expression rates of CD49e were low in both U266 and OPM2 cells. Expression of RARα2 in OPM2 cells of combination groups were higher than those of control group and corresponding single groups (P<0.05); and there was no significant difference between control group and G-CSF groups (P>0.05). Expression of RARα2 in U266 cells of control group and G-CSF groups was not detected; and ATRA groups and combination groups had weak expression.

CONCLUSIONATRA can induce proliferation inhibition in RARα2-expressing myeloma cells, and it may also play a certain role in promoting differentiation of RARα2 positive myeloma cells.