ABSTRACT
Objective To study the radiation sensitive enhancement ratio (SER) of NS398 on esophageal cancer stem cells and adherent tumor cells and analyze the radioresistance related protein expressions.Methods ECA109 esophageal cancer stem cells were cultured in serum-free medium.Expression levels of cell surface maker CD44 + and CD271 + were analyzed by flow cytometry.MTT assay was used to detect cell proliferation after the treatments with NS398 and irradiation(0,4 and 8 Gy).The sensitization effects of NS398 on the parental cells and its spheroid were evaluated by clone formation assay.Western blot assay was performed to determine protein expressions.Results Serum-free medium was successfully applied to isolate the cancer stem cells with spherical properties.CD271 + in the spheroid cells was notable higher than that in the parent cells (t =3.81,P ＜ 0.05).After irradiation,the proliferation rate of parental cells was higher than that in spheroid cells.After the combination treatment of NS398 and irradiation,SF2 value of parental cells was lower than spheroid cells(t =2.91,P ＜ 0.05)and the SER of NS398 on parental cells was greater than spheroid cells.The expressions of Bmi-1,c-Myc,β-catenin and Cyclin D1 in spheroid cells were higher than those in parental cells (t =8.09,7.90,7.50,7.15,P＜0.05).Cyclin D1 expression levels under both cell situations increased after 4 Gy irradiation (t =9.74,6.67,P ＜0.05).Compared to the 4 Gy irradiation alone group,the β-catenin and Cyclin D1 expression levels in both parental cells (t =10.15,12.12,P ＜ 0.05) and spheroid cells (t =3.23,7.45,P ＜ 0.05) decreased in the combination group.Conclusions Esophageal cancer stem cells with high level of CD271 can be isolated with serum-free medium and it is radioresistant where β-catenin and its downstream proteins may be involved.