Abstract: Objective To isolate side population (SP) cells from human cervical cancer cells and to determine the characteristics of cancer stem cells, so as to investigate the feasibility of starting research on cervical cancer stem cells from the SP cells. Methods The human cervical cancer cells were obtained from fresh human cervical cancer tissue of 40 patients who were diagnosed as cervical cancer. Flow cytometry and Hoechst 33342 dye efflux assay were used to isolate SP cells and NSP cells from the cervical cancer cells. The proliferation and differentiation of the two sub-population cells were observed. The two sub-population cells were injected into nude mice subcutaneously to observe their tumorigenesis ability. The inhibition rates of SP and NSP cells were assessed after treatment with chemotherapy drugs (cisplatin) to evaluate the resistance. Results The proportion of SP cells excluding Hoechst 33342 dye in the human cervical cancer cells was 2.04%±0.93%, and the proportion of the SP cells was decreased with the the degree of reduction of differentiation(P<0.05). Cell growth curve indicated that proliferative capacity of the SP cells was better than the NSP cells (P<0.05). The SP cells demonstrated stronger tumorigenesis ability in nude mice. As few as 1×103 SP cells could give rise to new tumors in xenotransplantation, with a tumorigenesis ability 100 times as high as that of the NSP cells. The time of tumor formation was significantly reduced. After treatment with different concentrations of chemotherapy drugs (cisplatin) for 24h, the SP cells had significantly lower inhibition rate than the NSP cells (P<0.05). Conclusion Human cervical cancer cells contains a small subpopulation of cells excluding Hoechst 33342 dye. The more poorly the cell line differentiated,the fewer the proportion it contained. The SP cells has better proliferative capacity in vitro and stronger tumorigenicity than the NSP cells, with strongly resistant to chemotherapy drugs. The SP cells have the characteristics of cancer stem cells. So it can be applied to the cervical cancer stem cell research.

Key words: cervical cancer, side population cells, cancer stem cells, proliferation, tumorigenicity, drug resistance