Study Of Stem Cell-like Properties Of Basal-like Breast Cancer BT549 Cell Line And Characterization Of Heterogeneity Of Its Subsets

Tumor heterogeneity study receives more attention in recent years, it impact on understanding of tumor growth, invasiveness, drug sensitivity, prognosis, and so on. Heterogeneity within breast tumors has been experimentally confirmed, with most studies point to the pressure of tumor microenviroment and drug intervention. In this study, we analyzed the expression of stem cell-like antigens in breast cancer cell lines to verify the hypothesis that heterogeneity of breast cancer cells is the root cause of breast tumor heterogeneous diversity.We used BT549 with CD44(+)/CD24(-) subpopulation cell ratio close to 50% as the starting material, analyzed expression level of the breast cancer stem cell-like antigens CD44, CD24, and basal-like breast cancer stem cell-like antigen CD49 f. Based on expression of CD44, CD24 and CD49 f, BT549 cells were divided into multiple subpopulations. We found significant differences of generic stem cell-like antigen CD133 expressed in each subpopulation of cells, and the CD133-positive cells in BT549 cells were proportionally low, indicating the clearly heterogeneity of stem cell-like biomarkers in BT549 cells.By analyzing subpopulations of BT549 cells, we found obvious differences of expression of myoepithelial cell differentiation antigens CK14 and α-SMA. CK14 positive cells accounted for small proportion of BT549 cells, suggesting BT549 cells were in incomplete differentiation stage and heterogeneity in each subpopulation formed the differences amout cell populations.Two subpopulations CD44(+)/CD24(-) and CD44(+)/CD24(+), with purity of greater than 90% after flow sorting were cultured on complete growth medium with 10% fetal bovine serum shown abilitly to maintain stem cell-like phenotype, and there was no transformation of their phenotype, indicating stem cell-like phenotypic differences were not influenced from conditions. Also, there were no differences on growth rate, apoptosis of CD44(+)/CD24(-) subpopulation and CD44(+)/CD24(+) subpopulation compared with that of the wild type BT549, indicating the genetic stability of BT549 cells in vitro. However, tolerance of the wide type BT549 to low concentrations of nutrients is better than that of CD44(+)/CD24(-) subpopulation and CD44(+)/CD24(+) subpopulation, CD44(+)/CD24(+) subpopulation shown greater resistance to Anoikis compared with the wild type BT549 and CD44(+)/CD24(-) subpopulation, and lower susceptibility to paclitaxel, indicating the heterogeneity of biological traits in BT549 cells.These results indicate the heterogeneity of stem cell-like antigens and differentiation antigens expression presence of BT549 cells, there are also differences of biological traits such as serum-dependence, anti-Anokis ability and drug resistance, suggesting the characteristic of breast cancer cells innate heterogeneity is one of the sources of breast cancer heterogeneity.