ElevatedCRB3 expression suppresses breast cancer stemness by inhibiting β‐catenin signalling to restore tamoxifen sensitivity

Abstract

Tamoxifen is a first‐line drug for hormone therapy (HT) in oestrogen receptor‐positive breast cancer patients. However, 20% to 30% of those patients are resistant to tamoxifen treatment. Cancer stem cells (CSCs) have been implicated as one of the mechanisms responsible for tamoxifen resistance. Our previous study indicated that decreased expression of the CRB3 gene confers stem cell characteristics to breast cancer cells. In the current investigation, we found that most of the breast cancer patient tissues resistant to tamoxifen were negative for CRB3 protein and positive for β‐catenin protein, in contrast to their matched primary tumours by immunohistochemical analysis. Furthermore, expression of CRB3 mRNA and protein was low, while expression of β‐catenin mRNA and protein was high in tamoxifen resistance cells (LCC2 and T47D TamR) contrast to their corresponding cell lines MCF7 and T47D. Similarly, CRB3 overexpression markedly restored the tamoxifen sensitivity of TamR cells by the MTT viability assay. Finally, we found that CRB3 suppressed the stemness of TamR cells by inhibiting β‐catenin signalling, which may in turn lead to a decrease in the breast cancer cell population. Furthermore, these findings indicate that CRB3 is an important regulator for breast cancer stemness, which is associated with tamoxifen resistance.

Crumbs protein homolog 3 (CRB3) expression is associated with oestrogen and progesterone receptor positivity in breast cancer

“…In the current study, we found that CRB3 expression was inversely associated with tumour size (Table ), which is consistent with previous studies showing that downregulation of CRB3 expression induced breast cancer cell proliferation, whereas CRB3 overexpression inhibited proliferation of human breast cell lines . Our previous study also showed that the downregulation of CRB3 expression increased migration and invasion of breast cancer cells, whereas CRB3 overexpression inhibited migration and invasion of human breast and kidney cancer cell lines .…”

DLG5 suppresses breast cancer stem cell‐like characteristics to restore tamoxifen sensitivity by inhibiting TAZ expression

“…The experimental protocol was approved by the Ethics Review Committee of the First Affiliated Hospital of Xi'an Jiaotong University. A total of 9 metastatic breast cancer tissues from patients, who were resistant to TAM, and their matched primary tumours were obtained from the First Affiliated Hospital of Xi'an Jiaotong University …”

“…The signals were photographed using a microscope slide scanner (Leica MP, SCN400). The intensity of antibody staining in individual fields was semi‐quantitatively analysed, as described previously …”

“…Human ER+ breast cancer MCF7 cells were given by Dr. Jianmin Zhang (Roswell Park Cancer Institute, Buffalo, New York, USA) and cultured in DMEM (Hyclone) supplemented with 10% fetal bovine serum (FBS) (Hyclone). The TAM‐resistant MCF7‐TamR and LCC2 cells were derived from MCF7 by continuous exposure to TAM, as previously described and cultured in phenol‐red‐free DMEM supplemented with 5% charcoal‐dextran stripped FBS and 1 μmol L −1 4‐hydroxytamoxifen (4‐OHT) (Sigma). MCF7 and LCC2 cells were transduced with lentivirus for expression of shDLG5 or DLG5 to generate DLG5‐silenced MCF7 (MCF7‐shDLG5) and DLG5 overexpression LCC2 (LCC2‐oxDLG5), respectively .…”

“…Breast cancer stem cells (BCSCs) are thought to be critical players for drug resistance . BCSCs can regulate the sensitivity of breast cancer cells to TAM by modulating the NF‐κB, PI3K/PTEN/AKT/mTOR, β‐catenin and HER2 pathways . Therefore, reducing the frequency of BCSCs and inhibiting their function will be valuable for control of TAM resistance.…”