9%~79.8%[3]. Che Xiaoming et al achieved similar outcomes by colony selection with the selleck products use of limited dilution, and harvested about 82% cells that have the proliferation capacity[2]. We obtained highly purified BTSCs by their method. As is known to all, EGF and bFGF, as powerful promoters of cell division, are essential key components in stem cell culture medium, and enable stem cells to proliferate continuously. Through MTT experiment,

we have found that ATRA alone can promote the proliferation of BTSCs, but the promoting effect is weaker than EGF+bFGF, and there is no obvious synergistic or antagonistic effect between ATRA and EGF+bFGF. Previous researches have showed that ATRA can inhibit the proliferation of ordinary glioma cells cultured in serum-containing medium, promoting apoptosis of the glioma cells. We have observed that BTSCs in the control group grew as suspended spheres when cultured in the medium without serum and growth

factors. Similar to the control group, BTSCs in the ATRA group were not adherent, but the formed spheres were larger and the proliferation was more rapid, indicating that ATRA did not induce the DNA Damage inhibitor differentiation of the suspended BTSCs, but promote the proliferation of BTSCs. The reason may be as mentioned below. In the serum-free medium, BTSCs can achieve continuous self renewal and proliferation through symmetric division, retaining the stem cell characteristics; and in the serum-containing click here medium, because of the influence of certain substance in the serum, BTSCs can retain their existence through asymmetric division, and produce a great number of comparatively

mature progeny cells, which differentiate into ordinary tumor cells ultimately, so there is only a small percentage of BTSCs in the whole cell population. The targets of ATRA’s effect of differentiation induction are cells in the process of differentiation. For BTSCs in the stem cell state, ATRA has a promoting effect on their proliferation. So ATRA exerts opposite effects on BTSCs at different stages of differentiation, the mechanism of which needs further clarification. Clinical trials of differentiation of brain glioma cells induced by ATRA showed that the differentiation effect of ATRA alone was weak, with insignificant curative efficacy[8, 9]. We speculate that the application of ATRA alone can induce the differentiation and apoptosis of most ordinary glioma cells, but promote the proliferation of a minority of BTSCs that does not experience differentiation, that is to say, the “”seeds”" resulting in the formation, development and relapse of tumors do not decrease but increase, which may be exactly the major reason for the poor therapeutic effect. Research of Singh et al revealed that only CD133 positive cells had the stem cell characteristics of self-renewal, unlimited proliferation and multilineage parent differentiation[3]. These days, CD133 has been recognized as the marker to isolate and identify BTSCs.