Effect of All-Trans Retinoic Acid on the Differentiation of U87 Glioma Stem/Progenitor Cells

GSPCs (glioma stem/progenitor cells) were isolated from U87 glioma cell lines by serum-free neural stem cell medium. Four concentrations (1, 2, 4, and 8 mu mol/L) of ATRA (all-trans retinoic acid) were used to induce the differentiation of GSPCs in the medium with or without growth factors. The effect of ATRA on the differentiation of GSPCs was analyzed by flow cytometry, real-time-PCR, and immunofluorescence. The differentiation of GSPCs could be induced by 1 or 2 mu mol/L ATRA when GSPCs were cultured in growth factor-free medium. The detection of real-time-PCR showed that the level of GFAP (glial fibrillary acidic protein) mRNA of differentiated GSPCs in the growth factor-free medium containing 1 mu mol/L ATRA group was significantly higher than that in the control group, and there was no significant difference in the level of TUBB-3 mRNA between the two groups. The GSPCs suffered apoptosis in the growth factor-free medium containing 4 or 8 mu mol/L ATRA. The differentiation of GSPCs could not be induced by ATRA when GSPCs were cultured in the medium containing growth factors. The percentage of cells in G0/G1 phase was 84.26 +/- A 2.24 %, and the percentage of apoptosis was 18.95 +/- A 2.53 % in experimental groups which was similar to those in the control group. In conclusion, ATRA has certain capacity to induce differentiation of GSPCs, while its effective concentration should be controlled strictly. The differentiation of GSPCs induced by ATRA cannot antagonize the formidable differential inhibition of epidermal growth factor and basic fibroblast growth factor.