Abstract: Objective
To detect the expressions of hypoxia inducible factor -2α and ATP-binding cassette super family G2(ABC G2) in  mammospheres(MSs)  transplantation tumor tissue  in  nude mice，and to discuss the  possible  mechanism of the MSs’ strong tumor formation ability.Methods The  MSs cultured in serum-free media supplemented with growth factors were transplanted in the nude mice,and the growth of thetransplantation tumor was recorded.The expressions of HIF-2α and ABCG2 in transplantation tumor tissue were observed by immunohistochemistry.The expressions of HIF-2α and ABCG2 potein and mRNA in transplantation tumor tissue were detected by Western blotting and Real-time RT-PCR.Results The  MSs had the stronger tumor formation ability than the MCF-7 cell lines. Immunohistochemistry showed the expressions of HIF-2α and ABCG2 in transplantation tumor tissue in  nude mice. The expressions of HIF-2α and ABCG2 proteins in MSs transplantation tumor tissue were higher than those  in  MCF-7 transplantation tumor tissue and  para-tumor tissue（P<0.05）.The expressions of HIF-2α and ABCG2  mRNA in MSs transplantation tumor tissue were higher than those  in  MCF-7 transplantation tumor tissue  and  para-tumor tissue（P<0.05）.Conclusion  There are high expressions of HIF-2α and ABCG in  MSs transplantation tumor tissue.It is speculated that HIF-2α and ABCG may be the possible mechanism of MSs’ strong tumor formation ability.

Key words: breast neoplasms, transplantation t
umor, hypoxia inducible factor-2&alpha, ATP-binding cassette super family G 2