At present, it is widely believed that the expression of ABCG2/BCRP on the cell surface is positively correlated with activation of the PI3K/Akt pathway. Liang and Zhang have shown that the PI3K/Akt signaling pathway affects tumor radioresis tance by anti apoptosis and activation of DNA repair mechanisms. Moreover, in a study of malignant glioma, Keishi found that the PI3K/Akt further signaling pathway affects the radioresistance of tumor cells by mediating the autophagy process. So far, it still remains far from clear for the exact mechanisms of the radioresistance and chemoresistance of SP cells and further investigations are needed. Conclusion In summary, a small number of SP cells were sorted from the HeLa cervical cancer cell line, which showed strong capacities for proliferation, anti apoptosis, and certain de grees of radioresistance and chemoresistance.

These SP cells likely include stem like tumor cells. Further study of the sorted SP cells from HeLa cells may provide new in sights into the treatment of cervical cancer. Materials and methods Cell culture The human cervical cancer cell line HeLa was purchased from the American Type Culture Collection and main tained in the laboratory of the Department of Gynecology and Obstetrics, Peking University Peoples Hospital. HeLa cells were maintained as adherent mono layer cultures in high glucose Dulbecco Modified Eagles Medium supplemented with 10% fetal bovine serum and incubated at 37 C with 5% CO2. The medium was re placed every 2 3 days. At 80 90% confluency, the cells were washed twice with PBS, and then digested with 0.

25% trypsin and 0. 02% EDTA. Fluorescence activated cell sorting of SP cells HeLa cells in the logarithmic growth phase were trypsi nized, washed twice with PBS, and counted. Then, the HeLa cells were resuspended in DMEM with 2% FBS and divided into two groups. Group 1 was incubated with the DNA binding dye Hoechst 33342 at a final concentration of 5 ug/mL for 90 min at 37 C with gentle agitation every 15 min. Group 2 was pretreated with 50 ug/mL verap amil for 15 min at 37 C, and then incubated with Hoechst 33342 for 90 min at 37 C with gentle agitation every 15 min. The incubation process was carried out in the dark. The cells were then washed twice with ice cold PBS and resuspended in PBS containing 2% FBS and 10 mM HEPES. The cell suspension was stored at 4 C while protected from light before FACS.

Cell suspen sions were freshly prepared for cell sorting and stained with PI at a final concentration of 2 Anacetrapib ug/mL. Cell sorting was performed using a FACS DIVA fluorescence activated cell sorter. SP and non SP cells were collected separately in sterile 25 cm2 flasks and cultured in DMEM containing 10% FBS at 37 C with 5% CO2. Cell morphology was ex amined under an inverted microscope every 6 h.