FOXA1 expression affects the proliferation activity of luminal breast cancer stem cell populations.
Bottom Line: Using a quantitative PCR analysis, we found that mammosphere forming cells showed a higher expression of FOXA1 and stemness-related genes compared with adherent culture cells.As a result, we found no significant difference in the number of mammospheres but decreased colony formation in shFOXA1 MCF-7 cells compared with control.These results suggest that the expression of FOXA1 appears to be involved in the proliferation of immature BC cells rather than the induction of stemness-related genes and self-renewal potency of CSCs.
Affiliation: Department of Breast-Thyroid-Endocrine Surgery, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.Show MeSH
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Mentions: To clarify the stemness of luminal BC, we first isolated BC cells from metastatic breast cancer pleural effusion and characterized them. Immunohistochemical staining of the surgical tissue is shown in Figure 1(a): ER‐positive, HER2‐negative, and FOXA1‐positive staining was evident in approximately 80–90% of cells. NANOG, OCT4, and SOX2 were not stained in the tissue sample (data not shown). In newly isolated cells, named BC#1 cells, ER was not expressed, whereas PgR was expressed in nearly 80% by immunohistochemical staining (Fig. 1b, Table 2). As the PgR expression in the tumor has been determined to be an indication of functional ER,36, 37 we analyzed the expression of ER in BC#1 cells. BC#1 cells were negative for ER according to immunohistochemical staining, whereas ER mRNA expression was higher in BC#1 than in MDA‐MB‐231 cells (Fig. 1c). The reason behind the decreased ER expression of BC#1 was surmised as follows. It has been reported that the hormone receptor discordance between primary and recurrent BC has occurred at the frequency of 10–40%, because of the change in tumor characteristics after treatment.38 In addition, it is known that long‐term estrogen deprivation in culture causes the instability of ER expression in vitro.39 These factors might cause the discrepancy of the ER expression in BC#1 cells isolated from the pleural effusion. According to epithelial markers, approximately 100% of BC#1 cells were strongly positive for CK 8 and partially positive for CK 5/6. Therefore, we confirmed that there is little contamination of the non‐epithelial population in BC#1 cells. MCF‐7 and HCC1500 cells were positive for CK 8 (Fig. 1b, Table 2). We next examined FOXA1 expression by immunohistochemical staining. FOXA1 was positively expressed in MCF‐7 and HCC1500 cells, but not in BC#1 cells (Fig. 1b).
Affiliation: Department of Breast-Thyroid-Endocrine Surgery, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.