Development of the central nervous system (CNS) occurs normally in mammalian fetus despite lower temperature in the brain region than in the heart. To investigate the effects of temperature niche on the neural differentiation of stem cells in vitro, P19 embryonic carcinoma (EC) stem cells and N2a neuroblastoma stem cells were induced to undergo neural differentiation by retinoic acid and LiCl, respectively. The cells were analyzed for the expression of neural marker genes during 12 days differentiation. Although there were Map2 and NCAM expressions in both groups, no clear difference was found. Similarly, expression patterns of Tuj1 and NF-M were not different in both groups, showing more intensive staining patterns at day 12 than those at days 4 and 8, respectively. However, more cells expressed GFAP markedly at day 12 in 37℃ group. There was little expression of the above markers in N2a cells during differentiation except for Ngn2 and Tuj1. It was found that Ngn2 was expressed more intensely at days 6 and 9 in 33℃ group. Tuj1 expression showed a similar pattern to those of P19 EC cells. RT-PCR analysis also showed that the expressed transcripts did not quite different in both groups, although they were different among the days of differentiation. Thus, it appears that neural differentiation occurs normally with a slight delay and probably less cell death in the cells at 33℃ than that at 37℃.

Chemoresistance is one of the main problems to treat different kinds of cancers or cancer cells. Therefore, it is necessary to find out the strategies to make the cancer cells sensitive to chemotherapy along with optimal dosage of drugs. We examined sensitivity of MCF7 cells through pretreating with an epigenetic modulator, azacytidine (AzaC) to doxorubicin (Dox). The cells were treated with 5 and 10 mM of AzaC for a week, subsequently with 50, 100 and 500 nM of doxorubicin for 24 and 48h. It was found that pretreatment of AzaC significantly enhance the sensitivity of MCF7 cells to Dox, inducing cell death. After 24h 15% cells underwent apoptosis in 500 nM dox treatment group while 23.4% cells death occurred in AzaC pre treatment group. After 48h MCF7 cells treated with Dox showed 19.0% cell death while AzaC sensitized cells showed 50.0% cells death when exposed to 500 nM of Dox for 48h. Western blot analysis showed the upregulations in the expression of bax, caspase-3, caspase-9 and p53 in AzaC-sensitized MCF7 cells treated with Dox as compared to those treated with only Dox. There was no clear indication for pro-apoptosis genes in the cells treated with individual drugs. These results showed that pretreatment with the epigenetic modulator significantly increased the sensitivity of MCF7 cells to Dox. Therefore it is concluded that demethylation event might enhance the activity of DNA intercalating agents to induce DNA damage in breast cancer cells.