ER-α36 Interactions With Cytosolic Molecular Network in Acquired Tamoxifen Resistance

Influence of CYP2D6, CYP2C19 and CYP3A5 polymorphisms on plasma levels of tamoxifen metabolites in Algerian women with ER+ breast cancer

Background

Tamoxifen, a selective estrogen receptor modulator, is indicated for breast cancer developed in response to estrogen.

Findings

In the current study we explored the relationship between the different variants of CYP2D6, CYP2C19, CYP3A5 and plasma Endoxifen levels in Algerian patients with ER + breast cancer. We further conducted the relationship between the candidate genes and the recurrences rate. Endoxifen levels differed significantly (p < .005) between carriers of two functional alleles and patients genotyped as CYP2D6*10, CYP2D6*17, CYP2D6*41 or CYP2D6*5/*5. Patients with elevated Endoxifen concentrations were significantly more likely to not report recurrences than patients with reduced or nul alleles. Such nul/nul, red/red, and red/nul diplotypes have been associated with a higher rate of recurrences than other genotypes during treatment.

Conclusion

Our findings suggest that the CYP2D6 genotype should be considered in tamoxifen-treated women. While quantitatively, CYP2D6 represents only a minor fraction of the total drug metabolizing capacity of the liver, it is polymorphic and, therefore, may alter the balance of metabolism of tamoxifen toward the activation pathways. Breast cancer patients with the CYP2D6 nul/nul or red/nul diplotype may benefit less from Tamoxifen treatment and are more likely to develop recurrences. Comprehensive CYP2D6 genotyping has a good predictive value for CYP2D6 activity. Common variants in CYP2C19 and CYP3A5 did not have a significant impact on the recurrences in this cohort of patients with ER + breast cancer.

Association of ERα-36 expression with the de novo resistance of tamoxifen in ER-positive breast cancer

BACKGROUND

Approximately 70-80% of breast cancer express ER-alpha and hormonal therapies, given significant improvements in patient survival. About 50% of ER-positive breast cancer patients with advanced disease insensitive to tamoxifen treatment when diagnosed. Recent studies have shown that ERα-36 is a crucial factor in the resistance of tamoxifen.

OBJECTIVE

This study aims to determine the association between ERα-36 expression and de novo resistance of tamoxifen in patients with ER-positive breast cancer.

METHODS

This study was an observational study using a cross-sectional method and was conducted at Wahidin Sudirohusodo Hospital and Unhas Hospital. ERα-36 protein expression was assessed using an immunohistochemistry assay. The association of ERα-36 expression and resistance of tamoxifen was tested with the Chi-square test.

RESULTS

A total of 50 locally advanced breast cancer cases were included in this study, 22 cases (44%) had overexpression of ERα-36, and 28 cases (56%) had not, 24 cases (48%) had experience resistance to tamoxifen and 26 cases (52%) had not. There was a significant association between ERα-36 expressions and resistance of tamoxifen (p = 0.000).

CONCLUSIONS

There was an association between the expression of ER-α36 with de novo resistance of tamoxifen in ER-positive breast cancer. ER-α36 could act as a worth considering biomarker for de novo resistance of tamoxifen in therapeutic strategies.

CUL4B renders breast cancer cells tamoxifen-resistant via miR-32-5p/ER-α36 axis

Tamoxifen (TAM) resistance is a significant clinical challenge in endocrine therapies for estrogen receptor (ER)-positive breast cancer patients. Cullin 4B (CUL4B), which acts as a scaffold protein in CUL4B-RING ubiquitin ligase complexes (CRL4B), is frequently overexpressed in cancer and represses tumor suppressors through diverse epigenetic mechanisms. However, the role and the underlying mechanisms of CUL4B in regulating drug resistance remain unknown. Here, we showed that CUL4B promotes TAM resistance in breast cancer cells through a miR-32-5p/ER-α36 axis. We found that upregulation of CUL4B correlated with decreased TAM sensitivity of breast cancer cells, and knockdown of CUL4B or expression of a dominant-negative CUL4B mutant restored the response to TAM in TAM-resistant MCF7-TAM^R and T47D-TAM^R cells. Mechanistically, we demonstrated that CUL4B renders breast cancer cells TAM-resistant by upregulating ER-α36 expression, which was mediated by downregulation of miR-32-5p. We further showed that CRL4B epigenetically represses the transcription of miR-32-5p by catalyzing monoubiquitination at H2AK119 and coordinating with PRC2 and HDAC complexes to promote trimethylation at H3K27 at the promoter of miR-32-5p. Pharmacologic or genetic inhibition of CRL4B/PRC2/HDAC complexes significantly increased TAM sensitivity in breast cancer cells in vitro and in vivo. Taken together, our findings thus establish a critical role for the CUL4B-miR-32-5p-ER-α36 axis in the regulation of TAM resistance and have important therapeutic implications for combined application of TAM and the inhibitors of CRL4B/PRC2/HDAC complex in breast cancer treatment. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Evaluating human epidermal growth factor receptor 2 roles in the efficacy of Tamoxifen treatment in breast cancer, a systematic review

PURPOSE

Hormone therapy with Tamoxifen is an effective treatment that can decrease recurrence rate and mortality. Numerous molecular mechanisms can modify the response to Tamoxifen. The objective of this study was to determine Tamoxifen efficacy on patients' recurrence and mortality rates, according to the human epidermal growth factor receptor 2 (HER2) status.

METHODS

In this meta-analysis of published studies, relapse and death rates were measured in both HER2 negative and positive patients treated with Tamoxifen. Besides, the relative risk of treatment with Tamoxifen compared to no Tamoxifen treatment was evaluated in both HER2 positive and negative patients.

RESULTS

There was an increased risk of recurrence in HER2 positive patients who received Tamoxifen compared with HER2 negative ones (RR = 1.63, p value < 0.001). Tamoxifen treatment is associated with decreased relapse rate (RR = 0.70, p value < 0.001); however, it did not effect on HER2 positive ones (RR = 1, p value = 0.99).

CONCLUSION

According to the analysis result, the relapse rate in breast cancer patients who were treated with Tamoxifen depends on the HER2 situation. Despite the limited sample size, it is revealed that Tamoxifen can decrease the relapse rate only in HER2 negative patients.

The Role of ERα36 in Development and Tumor Malignancy

Estrogen nuclear receptors, represented by the canonical forms ERα66 and ERβ1, are the main mediators of the estrogen-dependent pathophysiology in mammals. However, numerous isoforms have been identified, stimulating unconventional estrogen response pathways leading to complex cellular and tissue responses. The estrogen receptor variant, ERα36, was cloned in 2005 and is mainly described in the literature to be involved in the progression of mammary tumors and in the acquired resistance to anti-estrogen drugs, such as tamoxifen. In this review, we will first specify the place that ERα36 currently occupies within the diversity of nuclear and membrane estrogen receptors. We will then report recent data on the impact of ERα36 expression and/or activity in normal breast and testicular cells, but also in different types of tumors including mammary tumors, highlighting why ERα36 can now be considered as a marker of malignancy. Finally, we will explain how studying the regulation of ERα36 expression could provide new clues to counteract resistance to cancer treatments in hormone-sensitive tumors.

A Role for Estrogen Receptor alpha36 in Cancer Progression

Estrogen receptor α (ERα) functions as a ligand dependent transcription factor that directly binds specific estrogen responsive elements, thus regulating the transcription of estrogen sensitive genes. ERα has also been shown to be associated with the plasma membrane (membrane associated ERα, mERα), concentrated in lipid rafts, plasma membrane microdomains with a distinct lipid composition, where it transduces membrane-initiated estrogen-dependent activation of the mitogen-activated protein (MAP) kinase signaling pathway. Two isoforms of ERα have been described: the "traditional" ERα66 (66 kDa) and a lower molecular weight variant: the ERα46 (46 kDa). More recently, a novel ERα variant with a molecular mass of 36 kDa (ERα36) has been discovered. Notably, ERα36 has been found expressed in different human tumor cells, including both ER- positive and ER- negative breast cancer cells. Estrogen signaling at the cell membrane via ERα36 appears as capable of activating multiple pathways of importance for cancer aggressiveness and metastatic potential. The presence of serum autoantibodies reacting with mERα (anti-ERα Abs) in a large percentage of patients with breast cancer has recently been reported by our group. These anti-ERα Abs seem to act as estrogen agonists rapidly triggering MAP kinase pathway activation thus inducing tumor cell proliferation and overcoming cell resistance to anti-estrogen drug tamoxifen. In this review, we describe the involvement of ERα36 in different tumors. We also report the potential pathogenetic activity of anti-ERα Abs and their implication in drug resistance.

Overcoming Tamoxifen Resistance by Regulation of Del-1 in Breast Cancer

BACKGROUND

Hormone receptor-positive breast cancer accounts for nearly two-thirds of breast cancer cases; it ultimately acquires resistance during endocrine treatment and becomes more aggressive. This study evaluated the role of developmental endothelial locus (Del)-1 in tamoxifen-resistant (TAM-R) breast cancer.

METHODS

Del-1 expression in recurrent TAM-R breast cancer tissue was evaluated and compared to that in the original tumor tissue from the same patients. Del-1 expression was also evaluated in TAM-R cells by quantitative real-time PCR, western blotting, and enzyme-linked immunosorbent assay. The effects of Del-1 knockdown on the proliferation, migration, and invasion of TAM-R cells was assessed with wound-healing and Matrigel transwell assays.

RESULTS

Del-1 was more highly expressed in recurrent breast cancer as compared to the original tumor tissues before initiation of endocrine treatment. Del-1 mRNA was upregulated in TAM-R and small interfering RNA-mediated knockdown of Del-1 suppressed the migration and proliferation of TAM-R cells while partly restoring TAM sensitivity. And the TAM resistance was recovered by knockdown of Del-1.

CONCLUSIONS

TAM-R breast cancer is characterized by Del-1 overexpression and tumor progression can be inhibited by Del-1 depletion, which restores TAM sensitivity. Thus, therapeutic strategies that target Del-1 may be effective for the treatment of hormone-resistant breast cancer.

Oestrogen Non-Genomic Signalling is Activated in Tamoxifen-Resistant Breast Cancer

Endocrine therapies targeting oestrogen signalling have significantly improved breast cancer management. However, their efficacy is limited by intrinsic and acquired resistance to treatment, which remains a major challenge for oestrogen receptor α (ERα)-positive tumours. Though many studies using in vitro models of endocrine resistance have identified putative actors of resistance, no consensus has been reached. We demonstrated previously that oestrogen non-genomic signalling, characterized by the formation of the ERα/Src/PI3K complex, is activated in aggressive breast cancers (BC). We wondered herein whether the activation of this pathway is also involved in resistance to endocrine therapies. We studied the interactions between ERα and Src or PI3K by proximity ligation assay (PLA) in in-vitro and in-vivo endocrine therapy-resistant breast cancer models. We reveal an increase in ERα/Src and ERα/PI3K interactions in patient-derived xenografts (PDXs) with acquired resistance to tamoxifen, as well as in tamoxifen-resistant MCF-7 cells compared to parental counterparts. Moreover, no interactions were observed in breast cancer cells resistant to other endocrine therapies. Finally, the use of a peptide inhibiting the ERα–Src interaction partially restored tamoxifen sensitivity in resistant cells, suggesting that such components could constitute promising targets to circumvent resistance to tamoxifen in BC.

Tumor-Associated Macrophages Induce Endocrine Therapy Resistance in ER+ Breast Cancer Cells

Antiestrogenic adjuvant treatments are first-line therapies in patients with breast cancer positive for estrogen receptor (ER+). Improvement of their treatment strategies is needed because most patients eventually acquire endocrine resistance and many others are initially refractory to anti-estrogen treatments. The tumor microenvironment plays essential roles in cancer development and progress; however, the molecular mechanisms underlying such effects remain poorly understood. Breast cancer cell lines co-cultured with TNF-α-conditioned macrophages were used as pro-inflammatory tumor microenvironment models. Proliferation, migration, and colony formation assays were performed to evaluate tamoxifen and ICI 182,780 resistance and confirmed in a mouse-xenograft model. Molecular mechanisms were investigated using cytokine antibody arrays, WB, ELISA, ChIP, siRNA, and qPCR-assays. In our simulated pro-inflammatory tumor microenvironment, tumor-associated macrophages promoted proliferation, migration, invasiveness, and breast tumor growth of ER+ cells, rendering these estrogen-dependent breast cancer cells resistant to estrogen withdrawal and tamoxifen or ICI 182,780 treatment. Crosstalk between breast cancer cells and conditioned macrophages induced sustained release of pro-inflammatory cytokines from both cell types, activation of NF-κB/STAT3/ERK in the cancer cells and hyperphosphorylation of ERα, which resulted constitutively active. Our simulated tumor microenvironment strongly altered endocrine and inflammatory signaling pathways in breast cancer cells, leading to endocrine resistance in these cells.

Transcriptome profiling identified differentially expressed genes and pathways associated with tamoxifen resistance in human breast cancer

Tamoxifen (TAM) resistance is an important clinical problem in the treatment of breast cancer. In order to identify the mechanism of TAM resistance for estrogen receptor (ER)-positive breast cancer, we screened the transcriptome using RNA-seq and compared the gene expression profiles between the MCF-7 mamma carcinoma cell line and the TAM-resistant cell line TAMR/MCF-7, 52 significant differential expression genes (DEGs) were identified including SLIT2, ROBO, LHX, KLF, VEGFC, BAMBI, LAMA1, FLT4, PNMT, DHRS2, MAOA and ALDH. The DEGs were annotated in the GO, COG and KEGG databases. Annotation of the function of the DEGs in the KEGG database revealed the top three pathways enriched with the most DEGs, including pathways in cancer, the PI3K-AKT pathway, and focal adhesion. Then we compared the gene expression profiles between the Clinical progressive disease (PD) and the complete response (CR) from the cancer genome altas (TCGA). 10 common DEGs were identified through combining the clinical and cellular analysis results. Protein-protein interaction network was applied to analyze the association of ER signal pathway with the 10 DEGs. 3 significant genes (GFRA3, NPY1R and PTPRN2) were closely related to ER related pathway. These significant DEGs regulated many biological activities such as cell proliferation and survival, motility and migration, and tumor cell invasion. The interactions between these DEGs and drug resistance phenomenon need to be further elucidated at a functional level in further studies. Based on our findings, we believed that these DEGs could be therapeutic targets, which can be explored to develop new treatment options.