Clinical significance of PDEF factor expression and its relation to androgen receptor in ER- breast cancer

SPDEF enhances cancer stem cell-like properties and tumorigenesis through directly promoting GALNT7 transcription in luminal breast cancer

BACKGROUND

Luminal breast cancer (BC) is the predominant subtype of breast cancer with a sustained risk of late recurrence and death. Understanding the molecular mechanisms for the oncogenesis of luminal BC would improve the prognosis for this large subset of patients. SPDEF was reported to be dysregulated in breast cancers. However, the biological functions and underlying molecular mechanism of SPDEF in luminal BC remains largely unknown. The aim of the present study was to elucidate the potential roles of SPDEF underlying subtype-specific functions in BC, especially in luminal subtypes.

METHODS

The expressions and clinicopathological characteristics of SPDEF in luminal BC patients were evaluated bioinformatically. In vitro and in vivo assays were performed to investigate the oncogenic function and stemness maintenance of SPDEF in luminal BC. Chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays were conducted to determine the transcription regulation of GALNT7 by SPDEF. GALNT7 levels in serum from luminal BC patients were further detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

SPDEF is markedly upregulated in luminal BC and positively associated with tumor progression and poor prognosis. Furthermore, we confirmed that SPDEF enhanced the proliferation, migration, invasion and stemness of luminal BC cells in vitro as well the tumorigenicity in vivo. Mechanistically, we demonstrated the stimulative effect of SPDEF on the progression and stemness of luminal BC, which is mediated by its directly transcriptional target GALNT7. Clinically, we verified that the GALNT7 can be used as a noninvasive diagnostic marker. Noteworthy, the combined detection of serum GALNT7 and traditional tumor markers can enhance diagnostic accuracy thus is of vital importance in the early diagnosis of luminal BC.

CONCLUSIONS

Our study reveals a novel mechanism by which SPDEF transcriptionally activates GALNT7 via directly binding to its promoter to promote cell proliferation, motility and stemness, and led to luminal BC tumorigenesis and poor prognosis.

Identification of hub genes in AR-induced tamoxifen resistance in breast cancer based on weighted gene co-expression network analysis

BACKGROUND

Approximately 30% of patients with oestrogen receptor (ER)-positive breast cancer (BC) exhibit intrinsic or recurrent resistance to tamoxifen (TAM) adjuvant endocrine therapy. The androgen receptor (AR) is expressed in about 90% of ER-positive patients. Our previous studies found that BC patients with an AR:ER expression ratio ≥ 2.0 are more susceptible to TAM resistance. However, the specific mechanism by which a high AR:ER ratio promotes TAM resistance remains unknown.

METHODS

RNA sequencing was performed on 10 cases of BC tissues with AR:ER ratios ≥ 2.0 and 3 cases with AR:ER ratios < 2.0. We then compared our data with the screened TAM-resistant and TAM-sensitive cases from the TCGA BC database. Bioinformatics methods were used to screen differentially expressed genes (DEGs) and to perform gene enrichment analysis. Weighted correlation network analysis (WGCNA) was used to screen hub genes in the AR-induced TAM resistance process.

RESULTS

PAM50 analysis showed that the molecular phenotype of BC patients with AR:ER ratios ≥ 2.0 was similar to that of triple-negative breast cancer (TNBC), whereas the BC samples with AR:ER ratios < 2.0 were classified as the luminal subtype. Among the AR:ER ratio ≥ 2.0 and AR:ER < 2.0 BC tumours, 1855 DEGs were identified. Gene enrichment analysis showed that DEGs were enriched mainly in proliferation-related molecular pathways, such as the cell cycle, necroptosis, metabolic pathways and DNA replication. WGCNA analysis showed that SEC14L2, RIIAD1, STC2 and MAGEA6 served as hub genes in AR-induced TAM resistance and were associated with BC survival prognosis in the TCGA cohort.

CONCLUSIONS

A high AR:ER expression ratio is a biomarker for patients who might develop TAM resistance, and AR expression seems to be a possible mechanism of resistance to endocrine therapy.

TRPM4 is overexpressed in breast cancer associated with estrogen response and epithelial-mesenchymal transition gene sets

Ion channels form an important class of drug targets in malignancies. Transient receptor potential cation channel subfamily M member 4 (TRPM4) plays oncological roles in various solid tumors. Herein, we examined TRPM4 protein expression profile by immunohistochemistry (IHC) in breast cancer cases compared with normal breast ducts, its association with clinico-demographical parameters, and its potential function in breast cancers by Gene Set Enrichment Analysis (GSEA). Data-mining demonstrated that TRPM4 transcript levels were significantly higher in The Cancer Genome Atlas series of breast cancer cases (n = 1,085) compared with normal breast tissues (n = 112) (p = 1.03 x 10⁻¹¹). Our IHC findings in tissue microarrays showed that TRPM4 protein was overexpressed in breast cancers (n = 83/99 TRPM4⁺; 83.8%) compared with normal breast ducts (n = 5/10 TRPM4⁺; 50%) (p = 0.022). Higher TRPM4 expression (median frequency cut-off) was significantly associated with higher lymph node status (N1-N2 vs N0; p = 0.024) and higher stage (IIb-IIIb vs I-IIa; p = 0.005). GSEA evaluation in three independent gene expression profiling (GEP) datasets of breast cancer cases (GSE54002, n = 417; GSE20685, n = 327; GSE23720, n = 197) demonstrated significant association of TRPM4 transcript expression with estrogen response and epithelial-mesenchymal transition (EMT) gene sets (p<0.01 and false discovery rate<0.05). These gene sets were not enriched in GEP datasets of normal breast epithelium cases (GSE10797, n = 5; GSE9574, n = 15; GSE20437, n = 18). In conclusion, TRPM4 protein expression is upregulated in breast cancers associated with worse clinico-demographical parameters, and TRPM4 potentially regulates estrogen receptor signaling and EMT progression in breast cancer.

Double Agent: SPDEF Gene with Both Oncogenic and Tumor-Suppressor Functions in Breast Cancer

The dichotomy of cancer-regulatory genes into “oncogenes (OCGs)” and “tumor-suppressor genes (TSGs)” has greatly helped us in learning molecular details of tumor biology. SPDEF, known as the prostate-derived ETS factor, is reported to play a pivotal role in normal cell development and survival, which has also been endowed with dual characteristics in cancers. Breast cancer (BC) is a highly heterogeneous disease which becomes the leading reason for cancer-related fatality among women worldwide. The involvement of SPDEF in many aspects of BC has been postulated, whereas the mechanism governing the regulation of the pro- and anti-oncogenic activities of SPDEF in BC state remains poorly defined. In this review, we summarized SPDEF as the double agent involving in expression profiles, the regulatory mechanism in BC progression, as well as the role in diagnosis, treatment and prognosis of BC. The understanding of SPDEF duality has contributed to gain insight into the tumor biology and also add a new dimension to the new therapy targets for BC.

Triple negative breast cancer: special histological types and emerging therapeutic methods

Triple negative breast cancer (TNBC) is a complex and malignant breast cancer subtype that lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), thereby making therapeutic targeting difficult. TNBC is generally considered to have high malignancy and poor prognosis. However, patients diagnosed with certain rare histomorphologic subtypes of TNBC have better prognosis than those diagnosed with typical triple negative breast cancer. In addition, with the discovery and development of novel treatment targets such as the androgen receptor (AR), PI3K/AKT/mTOR and AMPK signaling pathways, as well as emerging immunotherapies, the therapeutic options for TNBC are increasing. In this paper, we review the literature on various histological types of TNBC and focus on newly developed therapeutic strategies that target and potentially affect molecular pathways or emerging oncogenes, thus providing a basis for future tailored therapies focused on the mutational aspects of TNBC.

The expression and prognostic role of EBP1 and relationship with AR in HER2+ breast cancer

Human epidermal growth factor receptor (HER)-2 positive (HER2⁺) breast cancer (BC) has a poor survival rate and is more aggressive in nature. HER2-targeting agents could be beneficial for patients with HER2⁺ BC. In addition, targeted therapy and chemotherapy have been successfully used. However, a few patients are resistant to treatment. ErbB3 binding protein 1 (EBP1) binds to HER3 and inhibits the proliferation and invasive potential of tumor cells. However, its role in HER2⁺ BC has not been demonstrated. In this study, we aimed to analyze the relationship between androgen receptor (AR) and EBP1 expression in HER2⁺ BC. A total of 282 cases (140 cases of HER2⁺ invasive BC and 142 HER2-negative invasive BC) were included in this study. We performed immunohistochemistry (IHC) to analyze the expression of AR and EBP1; thereafter, we evaluated the relationship between these two biomarkers and estrogen receptor (ER), progesterone receptor (PR), HER2, p53, Ki67 expression, and other clinicopathological parameters. Of the HER2⁺ cases, 67 (47.9%) showed high expression of EBP1 (EBP1^high) and 73 (52.1%) showed low/no expression of EBP1 (EBP1^low/no). EBP1 expression was correlated with AR expression, histological grade, and lymphatic metastasis (p < 0.001, < 0.001, and 0.013, respectively). Kaplan-Meier analysis revealed that AR⁺ and EBP1^low/no group had poorer overall survival (OS) and disease-free survival (DFS) compared with other groups (AR^- and EBP1^low/no, AR⁺ and EBP1^high, and AR^- and EBP1^high). AR⁺ and EBP1^low/no expression were independent prognostic factors for OS and DFS in HER2+ BC. This study showed the clinicopathological role of EBP1 and AR in HER2+ BC. Targeting EBP1 may be an effective treatment strategy for patients with AR⁺ HER2⁺ BC.

A high AR:ERα or PDEF:ERα ratio predicts a sub-optimal response to tamoxifen therapy in ERα-positive breast cancer

PURPOSE

Approximately 30% oestrogen receptor alpha (ERα)-positive breast cancer (BC) patients exhibit intrinsic or recurrent resistance to adjuvant endocrine therapy with tamoxifen. The androgen receptor (AR) is expressed in about 90% of ERα-positive patients, with particularly high expression in tamoxifen-resistant tumours. Prostate-derived Ets factor (PDEF), which is a co-regulator of AR, plays a role in tamoxifen resistance in ERα-positive BC. The purpose of this research was to analyse the potential roles of AR, PDEF and ERα levels in the response to tamoxifen resistance in ERα-positive BC.

METHODS

The nuclear AR:ERα and PDEF:ERα ratios were examined immunohistochemically in a cohort of 225 ERα-positive pre-menopausal BC patients who had received adjuvant tamoxifen therapy.

RESULTS

For both AR:ERα and PDEF:ERα ratios, the optimal cutoff value was 2.0. Patients receiving adjuvant tamoxifen treatment who had a high AR:ERα (≥ 2.0) (HR = 3.90) or PDEF:ERα ratio (≥ 2.0) (HR = 2.77) had a beyond twofold increased risk of failure. Both the AR:ERα ratio (P = 0.001) and PDEF:ERα ratio (P = 0.002) were independently associated with the risk of tamoxifen treatment failure. Furthermore, both a high ratio of AR:ERα (≥ 2.0) and PDEF:ERα (≥ 2.0) were associated with shorter disease-free survival (DFS) and shorter disease-specific survival (DSS). In addition, both the AR:ERα ratio and PDEF:ERα ratio were independent predictors of DFS (both P < 0.0001) and DSS (P = 0.001 and P < 0.0001, respectively).

CONCLUSIONS

AR:ERα and PDEF:ERα ratios are independent predictors of the response to conventional ERα-directed tamoxifen endocrine therapy.

AR-PDEF pathway promotes tumour proliferation and upregulates MYC-mediated gene transcription by promoting MAD1 degradation in ER-negative breast cancer

Background

Androgen receptor (AR) is expressed in 60%~ 70% oestrogen receptor (ER)-negative breast cancer (BC) cases and promotes the growth of this cancer subtype. Expression of prostate-derived Ets factor (PDEF), a transcription factor, is highly restricted to epithelial cells in hormone-regulated tissues. MYC and its negative regulator MAD1 play an important role in BC progression. Previously, we found that PDEF expression is strongly correlated with AR expression. However, the relationship between AR and PDEF and the function of PDEF in ER-negative BC proliferation are unclear.

Methods

AR and PDEF expression in ER-negative BC tissues and cell lines was determined by performing immunohistochemistry or western blotting. Protein expression levels and location were analysed by performing western blotting, RT-qPCR and immunofluorescence staining. Co-immunoprecipitation and chromatin immunoprecipitation assays were performed to validate the regulation of AR–PDEF–MAD1–MYC axis. Moreover, the effect of AR and PDEF on BC progression was investigated both in vitro and in vivo.

Results

We found that PDEF was overexpressed in ER-negative BC tissues and cell lines and appeared to function as an oncogene. PDEF expression levels were strongly correlated with AR expression in ER-negative BC, and PDEF transcription was positively regulated by AR. PDEF upregulated MYC-mediated gene transcription by promoting MAD1 degradation in ER-negative BC. Finally, we found that compared with the inhibition of AR expression alone, simultaneous inhibition of AR and PDEF expression further suppressed tumour proliferation both in vitro and in vivo.

Conclusions

Our data highlight the role of the AR–PDEF–MAD1–MYC axis in BC progression and suggest that PDEF can be used as a new clinical therapeutic target for treating ER-negative BC.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0883-0) contains supplementary material, which is available to authorized users.