Notch3 Maintains Luminal Phenotype and Suppresses Tumorigenesis and Metastasis of Breast Cancer via Trans-Activating Estrogen Receptor-α

Abstract

The luminal A phenotype is the most common breast cancer subtype and is characterized by estrogen receptor α expression (ERα). Identification of the key regulator that governs the luminal phenotype of breast cancer will clarify the pathogenic mechanism and provide novel therapeutic strategies for this subtype of cancer. ERα signaling pathway sustains the epithelial phenotype and inhibits the epithelial-mesenchymal transition (EMT) of breast cancer. In this study, we demonstrate that Notch3 positively associates with ERα in both breast cancer cell lines and human breast cancer tissues. We found that overexpression of Notch3 intra-cellular domain, a Notch3 active form (N3ICD), in ERα negative breast cancer cells re-activated ERα, while knock-down of Notch3 reduced ERα transcript and proteins, with alteration of down-stream genes, suggesting its ability to regulate ERα. Mechanistically, our results show that Notch3 specifically binds to the CSL binding element of the ERα promoter and activates ERα expression. Moreover, Notch3 suppressed EMT, while suppression of Notch3 promoted EMT in cellular assay. Overexpressing N3ICD in triple-negative breast cancer suppressed tumorigenesis and metastasis in vivo. Conversely, depletion of Notch3 in luminal breast cancer promoted metastasis in vivo. Furthermore, Notch3 transcripts were significantly associated with prolonged relapse-free survival in breast cancer, in particular in ERα positive breast cancer patients. Our observations demonstrate that Notch3 governs the luminal phenotype via trans-activating ERα expression in breast cancer. These findings delineate the role of a Notch3/ERα axis in maintaining the luminal phenotype and inhibiting tumorigenesis and metastasis in breast cancer, providing a novel strategy to re-sensitize ERα negative or low-expressing breast cancers to hormone therapy.

Notch-Induced Expression of FZD7 Requires Noncanonical NOTCH3 Signaling in Human Breast Epithelial Cells

“…Elevated levels of NR1 and JAG1 were correlated with poor patient prognosis, and shorter disease-free survival [207][208][209][210][211][212]. Although NR3 gene amplification was observed in breast cancer specimens at a low frequency [213], higher expression of NR3 was associated with improved recurrence-free survival in luminal A, luminal B and basal-like subtypes of breast cancers except for the HER2 overexpressing subtype [88]. And finally, the high expression of Notch ligands like JAG1 and DLL4 was associated with poor prognosis in breast cancer patients [193,207].…”

Oncogenic functions of the EMT-related transcription factor ZEB1 in breast cancer

“…Endocrine therapy is an important therapeutic strategy for breast cancer patients with ER-positive expression; however, antiestrogen resistance has become a major obstacle in endocrine therapy and involves reduced estrogen receptor-alpha (ER-α) expression. Zhang et al discovered that ZEB1 mechanistically inhibited ER-α transcription through the ZEB1/DNA methyltransferase 3B (DNMT3B)/histone deacetylase 1 (HDAC1) complex binding to hypermethylate and silence the ER-α promoter, subsequently attenuating the responsiveness of breast cancer cells to antiestrogen treatment [87]; these results indicate that ZEB1 is a key determinant of antiestrogen resistance in breast cancer.…”

Epigenetic silencing of SALL 2 confers tamoxifen resistance in breast cancer

“…Notably, the transcriptional levels of ESR1 are significantly decreased in relapsed lesions compared with primary tissues in tamoxifen-treated breast cancer (Johnston et al, 1995;Drury et al, 2011;Kim et al, 2011), suggesting that ESR1 might be transcriptionally repressed during acquired resistance to tamoxifen. Though multiple regulators, such as Notch3 (Dou et al, 2017), NR2E3 (Park et al, 2012), and MEL-18 (Lee et al, 2015), have been reported to be involved in tamoxifen resistance using cell or mouse models, the real contribution of these factors to tamoxifen resistance during therapy remains unclear.…”