Dual specificity phosphatase 4 gene expression in association with triple-negative breast cancer outcome

The impact of microRNAs on the resistance of breast cancer subtypes to chemotherapy

Breast cancer (BC) formation is primarily influenced by genetics, epigenetics and environmental factors. Aberrant Genetics and epigenetics leads to a condition known as heterogeneity. The heterogeneity of BC can be divided into several subtypes. Among the epigenetic factors, microRNAs (miRNAs) have been shown to play a crucial role in the development and progression of malignancies. These small non-coding RNAs regulate gene expression through a variety of mechanisms, resulting in either mRNA degradation or translation repression. As miRNAs directly control many proteins, genetic anomalies affect tumor metastasis, apoptosis, proliferation, and cell transportation. Consequently, miRNA dysregulations contribute not only in cancer development but also in invasiveness, proliferation rate and more importantly, drug response. Findings mostly indicate subtype-specified identical miRNA profile in BC. Among the BC subtypes, TNBC, HER2 + and luminal are the most resistant to therapy, respectively. Therapy resistance is greatly associated with miRNA expression profile. Hence, concentration of miRNA is the first marker of its role in chemotherapy response. Overexpressed miRNAs may disrupt drug efflux transporters and decrease the drug accumulation in cell. While down-regulated miRNAs which mediate drug resistance processes are mostly correlated with poor treatment response. Moreover, other mechanisms in which miRNAs play crucial roles in chemoresistance such as cell receptor mediations, dysregulation by environmental factors, DNA defects, etc. Recently, several miRNA-based treatments have shown promising results in cancer treatment. Inhibition of up-regulated miRNAs is one of these therapeutic approaches whilst transfecting cell with down-regulated miRNAs also show promising results. Moreover, drug-resistance could also be determined while in the pre-treatment phase via expression levels of miRNAs. Therefore, miRNAs provide intriguing insights and challenges in overcoming chemoresistance. In this article, we have discussed how miRNAs regulate breast cancer subtypes-specific chemoresistance.

Combined Dusp4 and p53 loss with Dbf4 amplification drives tumorigenesis via cell cycle restriction and replication stress escape in breast cancer

AIM

Deregulated signaling pathways are a hallmark feature of oncogenesis and driver of tumor progression. Dual specificity protein phosphatase 4 (DUSP4) is a critical negative regulator of the mitogen-activated protein kinase (MAPK) pathway and is often deleted or epigenetically silenced in tumors. DUSP4 alterations lead to hyperactivation of MAPK signaling in many cancers, including breast cancer, which often harbor mutations in cell cycle checkpoint genes, particularly in TP53.

METHODS

Using a genetically engineered mouse model, we generated mammary-specific Dusp4-deleted primary epithelial cells to investigate the necessary conditions in which DUSP4 loss may drive breast cancer oncogenesis.

RESULTS

We found that Dusp4 loss alone is insufficient in mediating tumorigenesis, but alternatively converges with loss in Trp53 and MYC amplification to induce tumorigenesis primarily through chromosome 5 amplification, which specifically upregulates Dbf4, a cell cycle gene that promotes cellular replication by mediating cell cycle checkpoint escape.

CONCLUSIONS

This study identifies a novel mechanism for breast tumorigenesis implicating Dusp4 loss and p53 mutations in cellular acquisition of Dbf4 upregulation as a driver of cellular replication and cell cycle checkpoint escape.

Cancer stem cell phosphatases

Cancer stem cells (CSCs) are involved in the initiation and progression of human malignancies by enabling cancer tissue self-renewal capacity and constituting the therapy-resistant population of tumor cells. However, despite the exhausting characterization of CSC genetics, epigenetics, and kinase signaling, eradication of CSCs remains an unattainable goal in most human malignancies. While phosphatases contribute equally with kinases to cellular phosphoregulation, our understanding of phosphatases in CSCs lags severely behind our knowledge about other CSC signaling mechanisms. Many cancer-relevant phosphatases have recently become druggable, indicating that further understanding of the CSC phosphatases might provide novel therapeutic opportunities. This review summarizes the current knowledge about fundamental, but yet poorly understood involvement of phosphatases in the regulation of major CSC signaling pathways. We also review the functional roles of phosphatases in CSC self-renewal, cancer progression, and therapy resistance; focusing particularly on hematological cancers and glioblastoma. We further discuss the small molecule targeting of CSC phosphatases and their therapeutic potential in cancer combination therapies.

Low DUSP4 Expression Is Associated With Aggressive Phenotypes and Poor Prognosis in Gastric Cancer

BACKGROUND/AIM

Dual-specificity protein phosphatase 4 (DUSP4) negatively regulates MAPK signaling and is involved in various cellular processes. We herein evaluated the relationship between DUSP4 expression and clinicopathological characteristics in a large series of gastric cancer samples.

MATERIALS AND METHODS

DUSP4 expression was examined by immunohistochemistry in 508 gastric cancer samples. Cases were classified according to the TCGA molecular classification and HER2 amplification. Kaplan-Meier plots were used to predict the relationship between mRNA expression of DUSP4 and survival.

RESULTS

Low expression of DUSP4 was significantly correlated with larger tumor size, higher pT category, positive nodal status, higher stage, lymphovascular invasion, perineural invasion, worse overall survival, and worse recurrence-free survival. No correlation was observed between DUSP4 expression and molecular characteristics. Bioinformatics analysis showed that low mRNA expression was associated with a poor prognosis.

CONCLUSION

Low expression of DUSP4 is associated with aggressive phenotypes of gastric cancer and a poor prognosis.

Association between lincRNA expression and overall survival for patients with triple-negative breast cancer

PURPOSE

Long intergenic non-coding RNAs (lincRNAs) are increasingly recognized as important regulators for pathogenesis and/or prognosis of breast cancer, including triple-negative breast cancer (TNBC) subtype. However, few previous studies used RNA-sequencing (RNA-Seq) technology, and none included an independent replication.

METHODS

To systematically evaluate the association between expression of lincRNAs and TNBC survival, we examined lincRNA expression profiles in TNBC tissues using RNA-Seq data for 200 TNBC patients from the Shanghai Breast Cancer Survival Study (SBCSS) and Southern Community Cohort Study (SCCS).

RESULTS

Twenty-five lincRNAs were found to be associated with overall survival (P < 0.05 and no significant heterogeneity across studies at Q statistic P > 0.1), and 61 lincRNAs were associated with disease-free survival (DFS). Among these, two lincRNAs (LINC01270 and LINC00449) were significantly associated with both worse overall survival and DFS and were expressed at significantly higher levels in tumor tissues compared with adjacent normal breast tissues (log2[Fold Change] > 0.5 and FDR < 0.05). We further evaluated the potential functions of LINC01270 and LINC00449 using in vitro functional experiments and found that siRNA-mediated knockdown of LINC01270 and LINC00449 expression significantly decreased cell viability, colony formation and cell migration ability in TNBC cells (P < 0.05).

CONCLUSIONS

Evidence from observational studies and in vitro experiments indicates that LINC00449 and LINC01270 may be prognostic biomarkers for TNBC.

DUSP4 directly deubiquitinates and stabilizes Smad4 protein, promoting proliferation and metastasis of colorectal cancer cells

Colorectal cancer is a common health-threatening tumor within the gastrointestinal tract. The aim of this study was to test the biological role of DUSP4 in colorectal cancer cells. In our study, DUSP4 overexpression-treated HCT116 cells and DUSP4 knockdown-treated SW480 cells were selected to perform study. Quantitative real-time PCR test (qRT-PCR) and western blot were used to detect DUSP4 abundance in clinical tissues and six cell lines, as well as ubiquitin-related Smad4 degradation. Western blot, migration and invasion. were used to assess the relationships between DUSP4 and Smad4. Higher DUSP4 expression of functional significance was observed in colorectal cancer tissues and cells. The results showed that both treatments could affect the proliferation, colony formation, migration, invasion of tumor cells, and the expression of epithelial mesenchymal transformation (EMT)-associated biomarkers. Moreover, in colorectal cancer cells, DUSP4 could promote the Smad4 degradation by regulating ubiquitin-related Smad4 degradation, and promote the cell proliferation, migration and invasion by regulating Smad4 degradation via Smad4 gene. Meanwhile, DUSP4 can directly deubiquitinate and stabilize Smad4 protein, hence further promote proliferation and metastasis of colorectal cancer cells.

CLCA2 expression is associated with survival among African American women with triple negative breast cancer

Purpose

Black/African American (AA) women are twice as likely to be diagnosed with triple negative breast cancer (TNBC) compared to whites, an aggressive breast cancer subtype associated with poor prognosis. There are no routinely used targeted clinical therapies for TNBC; thus there is a clear need to identify prognostic markers and potential therapeutic targets.

Methods

We evaluated expression of 27,016 genes in 155 treatment-naïve TN tumors from AA women in Detroit. Associations with survival were evaluated using Cox proportional hazards models adjusting for stage and age at diagnosis, and p-values were corrected using a false discovery rate. Our validation sample consisted of 494 TN tumors using four publically available data sets. Meta-analyses were performed using summary statistics from the four validation results.

Results

In the Detroit AA cohort, CLCA2 [Hazard ratio (HR) = 1.56, 95% confidence interval (CI) 1.31–1.86, nominal p = 5.1x10-7, FDR p = 0.014], SPIC [HR = 1.47, 95%CI 1.26–1.73, nominal p = 1.8x10-6, FDR p = 0.022], and MIR4311 [HR = 1.57, 95% CI 1.31–1.92, nominal p = 2.5x10-5, FDR p = 0.022] expression were associated with overall survival. Further adjustment for treatment and breast cancer specific survival analysis did not substantially alter effect estimates. CLCA2 was also associated with increased risk of death in the validation cohorts [HR = 1.14, 95% CI 1.05–1.24, p = 0.038, p-heterogeneity = 0.88].

Conclusions

We identified CLCA2 as a potential prognostic marker for TNBC in AA women.

miR-137 alleviates doxorubicin resistance in breast cancer through inhibition of epithelial-mesenchymal transition by targeting DUSP4

Acquired resistance to chemotherapy is a major obstacle in breast cancer (BC) treatment. Accumulated evidence has uncovered that microRNAs (miRNAs) are vital regulators of chemoresistance in cancer. Growing studies reveal that miR-137 acts as a suppressor in tumor progression. However, it remains obscure the role of miR-137 in modulating the sensitivity of BC cells to doxorubicin (DOX). In this study, we demonstrate that miR-137 exerts a significant effect on repressing the development of chemoresistance of BC cells in response to DOX via attenuating epithelial-mesenchymal transition (EMT) of tumor cells in vitro and in vivo. MiR-137 overexpression dramatically elevated the sensitivity of BC cells to DOX as well as impaired the DOX-promoted EMT of tumor cells. Mechanistically, miR-137 directly targeted dual-specificity phosphatase 4 (DUSP4) to impact on the EMT and chemoresistance of BC cells upon DOX treatment. Consistently, decreased DUSP4 efficiently enhanced the sensitivity of BC cells to DOX while overexpressed DUSP4 significantly diminished the beneficial effect of miR-137 on BC cells chemoresistance. Moreover, the increased miR-137 heightened the sensitivity of BC cells-derived tumors to DOX through targeting DUSP4 in vivo. Together, our results provide a novel insight into the DOX resistance of BC cells and miR-137 may serve as a new promising therapeutic target for overcoming chemoresistance in BC.

Patterns of Dual-Specific Phosphatase 4 mRNA Expression Before and after Neoadjuvant Chemotherapy in Breast Cancer

Objective: Evaluation of the neoadjuvant chemotherapy response can be performed by comparing the breast cancer burden and pathobiology before and after treatment. This study was aimed to investigate the pattern of dualspecific phosphatase 4 (DUSP4) mRNA expression in breast cancer cells before and after neoadjuvant chemotherapy. Methods: This was a longitudinal study. Twenty samples of matched breast cancer tissue taken from biopsy before and after chemotherapy were subjected to qRT-PCR to detect DUSP4 mRNA expression. Results: The mean value of DUSP4 mRNA expression in prechemotherapy breast cancer patients was 9.906±0.333 and that in breast cancer patients postchemotherapy was 10.016±1.062. In the responsive group, the rate of DUSP4 mRNA expression increased by 0.476 after chemotherapy. In the nonresponsive group, the proportion of DUSP4 mRNA expression likely decreased by 1.012. Statistical analysis found no significant correlation between DUSP4 mRNA expression prechemotherapy and the clinical chemotherapeutic response with p-value = 0.994 (p ≥0.05). A significant correlation was found between the postchemotherapy DUSP4 mRNA expression and the clinical chemotherapeutic response with p-value = 0.003 (p < 0.5). Conclusion: No significant difference was found in the mRNA expression of DUSP4 in pre- and post-neoadjuvant chemotherapy specimens. High DUSP4 expression postchemotherapy shows a substantial correlation with the chemotherapeutic response.

Gene expression in triple-negative breast cancer in relation to survival

PURPOSE

The identification of biomarkers related to the prognosis of triple-negative breast cancer (TNBC) is critically important for improved understanding of the biology that drives TNBC progression.

METHODS

We evaluated gene expression in total RNA isolated from formalin-fixed paraffin-embedded tumor samples using the NanoString nCounter assay for 469 TNBC cases from the Shanghai Breast Cancer Survival Study. We used Cox regression to quantify Hazard Ratios (HR) and corresponding confidence intervals (CI) for overall survival (OS) and disease-free survival (DFS) in models that included adjustment for breast cancer intrinsic subtype. Of 302 genes in our discovery analysis, 22 were further evaluated in relation to OS among 134 TNBC cases from the Nashville Breast Health Study and the Southern Community Cohort Study; 16 genes were further evaluated in relation to DFS in 335 TNBC cases from four gene expression omnibus datasets. Fixed-effect meta-analysis was used to combine results across data sources.

RESULTS

Twofold higher expression of EOMES (HR 0.90, 95% CI 0.83-0.97), RASGRP1 (HR 0.89, 95% CI 0.82-0.97), and SOD2 (HR 0.80, 95% CI 0.66-0.96) was associated with better OS. Twofold higher expression of EOMES (HR 0.89, 95% CI 0.81-0.97) and RASGRP1 (HR 0.87, 95% CI 0.81-0.95) was also associated with better DFS. On the contrary, a doubling of FA2H (HR 1.14, 95% CI 1.06-1.22) and GSPT1 (HR 1.33, 95% CI 1.14-1.55) expression was associated with shorter DFS.

CONCLUSIONS

We identified five genes (EOMES, FA2H, GSPT1, RASGRP1, and SOD2) that may serve as potential prognostic biomarkers and/or therapeutic targets for TNBC.

DUSP4 promotes doxorubicin resistance in gastric cancer through epithelial-mesenchymal transition

Chemoresistance limits treatment efficacy in gastric cancer and doxorubicin resistance is common in gastric cancer cells. Dual specificity phosphatase 4 (DUSP4) has been associated with tumor progression. This study aimed to investigate the mechanism of DUSP4 regulating doxorubicin resistance in gastric cancer cells. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay were used to measure cell viability and proliferation in gastric cancer cells treated with doxorubicin. The expression of DUSP4, E-cadherin and Vimentin protein was detected by Western blotting. Overexpression of DUSP4 was more resistant to doxorubicin in gastric cancer cells. Knockdown of DUSP4 increased the sensitivity of gastric cancer cells to doxorubicin. Moreover, up-regulation of DUSP4 promoted the Epithelial-Mesenchymal Transition (EMT) in gastric cancer cells, but blocking the EMT using a Twist siRNA increased the sensitivity of gastric cancer cells to doxorubicin and confirmed the EMT was involved in DUSP4-mediated doxorubicin resistance. These findings demonstrated that DUSP4 could enhance doxorubicin resistance by promoting EMT in gastric cancer cells.

Phosphatases and solid tumors: focus on glioblastoma initiation, progression and recurrences

Phosphatases and cancer have been related for many years now, as these enzymes regulate key cellular functions, including cell survival, migration, differentiation and proliferation. Dysfunctions or mutations affecting these enzymes have been demonstrated to be key factors for oncogenesis. The aim of this review is to shed light on the role of four different phosphatases (PTEN, PP2A, CDC25 and DUSP1) in five different solid tumors (breast cancer, lung cancer, pancreatic cancer, prostate cancer and ovarian cancer), in order to better understand the most frequent and aggressive primary cancer of the central nervous system, glioblastoma.

Sanguinarine inhibits growth and invasion of gastric cancer cells via regulation of the DUSP4/ERK pathway

Sanguinarine, a bioactive benzophenanthridine alkaloid extracted from plants of the Papaveraceae family, has shown antitumour effects in multiple cancer cells. But the therapeutic effects and regulatory mechanisms of sanguinatine in gastric cancer (GC) remain elusive. This study was aimed to investigate the correlation of dual‐specificity phosphatase 4 (DUSP4) expression with clinicopathologic features and overall survival in patients with GC and explore the effects of sanguinarine on tumour growth and invasion in GC cells (SGC‐7901 and HGC‐27) and underlying molecular mechanisms. Immunohistochemical analysis showed that decreased DUSP4 expression was associated with the sex, tumour size, depth of invasion and distant metastasis in patients with GC. Functional experiments including CCK‐8, Transwell and flow cytometry analysis indicated that sanguinarine or DUSP4 overexpression inhibited GC cell viability and invasive potential, and induced cell apoptosis and cycle arrest in S phase, but DUSP4 knockdown attenuated the antitumour activity of sanguinarine. Further observation demonstrated that sanguinarine up‐regulated the expression of DUSP4 and Bcl‐2‐associated X protein (Bax), but down‐regulated phosphorylated extracellular signal‐regulated kinase (p‐ERK), proliferating cell nuclear antigen (PCNA), matrix metalloproteinase 2 (MMP‐2) and B‐cell lymphoma 2 (Bcl‐2) expression. Taken together, our findings indicate that sanguinarine inhibits growth and invasion of GC cells through regulation of the DUSP4/ERK pathway, suggesting that sanguinarine may have potential for use in GC treatment.

Triple-negative breast cancer: the importance of molecular and histologic subtyping, and recognition of low-grade variants

Triple-negative breast cancers (TNBCs), defined by lack of expression of estrogen receptor, progesterone receptor and HER2, account for 12–17% of breast cancers and are clinically perceived as a discrete breast cancer subgroup. Nonetheless, TNBC has been shown to constitute a vastly heterogeneous disease encompassing a wide spectrum of entities with marked genetic, transcriptional, histological and clinical differences. Although most TNBCs are high-grade tumors, there are well-characterized low-grade TNBCs that have an indolent clinical course, whose natural history, molecular features and optimal therapy vastly differ from those of high-grade TNBCs. Secretory and adenoid cystic carcinomas are two histologic types of TNBCs underpinned by specific fusion genes; these tumors have an indolent clinical behavior and lack all of the cardinal molecular features of high-grade triple-negative disease. Recent studies of rare entities, including lesions once believed to constitute mere benign breast disease (e.g., microglandular adenosis), have resulted in the identification of potential precursors of TNBC and suggested the existence of a family of low-grade triple-negative lesions that, despite having low-grade morphology and indolent clinical behavior, have been shown to harbor the complex genomic landscape of common forms of TNBC, and may progress to high-grade disease. In this review, we describe the heterogeneity of TNBC and focus on the histologic and molecular features of low-grade forms of TNBC. Germane to addressing the challenges posed by the so-called triple-negative disease is the realization that TNBC is merely a descriptive term, and that low-grade types of TNBC may be driven by distinct sets of genetic alterations.

RNA Sequencing of Formalin-Fixed, Paraffin-Embedded Specimens for Gene Expression Quantification and Data Mining

Background. Proper rRNA depletion is crucial for the successful utilization of FFPE specimens when studying gene expression. We performed a study to evaluate two major rRNA depletion methods: Ribo-Zero and RNase H. RNAs extracted from 4 samples were treated with the two rRNA depletion methods in duplicate and sequenced (N = 16). We evaluated their reducibility, ability to detect RNA, and ability to molecularly subtype these triple negative breast cancer specimens. Results. Both rRNA depletion methods produced consistent data between the technical replicates. We found that the RNase H method produced higher quality RNAseq data as compared to the Ribo-Zero method. In addition, we evaluated the RNAseq data generated from the FFPE tissue samples for noncoding RNA, including lncRNA, enhancer/super enhancer RNA, and single nucleotide variation (SNV). We found that the RNase H is more suitable for detecting high-quality, noncoding RNAs as compared to the Ribo-Zero and provided more consistent molecular subtype identification between replicates. Unfortunately, neither method produced reliable SNV data. Conclusions. In conclusion, for FFPE specimens, the RNase H rRNA depletion method performed better than the Ribo-Zero. Neither method generates data sufficient for SNV detection.

ALDH1A1 mRNA expression in association with prognosis of triple-negative breast cancer

ALDH1 is a crucial element in the retinoic acid signaling pathway regulating the self-renewal and differentiation of normal stem cells, and may play an important role in cancer progression. However, research on ALDH1 gene expressionand breast cancer prognosis has yielded conflicting results. We evaluated the association between tumor tissue ALDH1A1/ALDH1A3 mRNA expression and triple-negative breast cancer (TNBC) prognosis in the Shanghai Breast Cancer Survival Study (SBCSS, N=463), Nashville Breast Health Study (NBHS, N=86), and Southern Community Cohort Study (SCCS, N=47). Gene expression was measured in RNA isolated from breast cancer tissues. In the SBCSS, higher ALDH1A1 mRNA level was associated with improved disease-free (HR=0.87, 95% CI: 0.80-0.95, per log unit change) and overall survival (HR=0.85, 95% CI: 0.78-0.93 per log unit change) independent of age at diagnosis, TNM stage and treatment. We replicated the findings for overall survival in the NBHS and SCCS (HR = 0.27, 95% CI: 0.10-0.73) and for disease-free survival by a meta-analysis of four publicly-available gene expression datasets (HR = 0.86, 95% CI: 0.76-0.97). No significant association was found for ALDH1A3. Our study suggests high expression of ALDH1A1 mRNA in tumor tissues may be an independent predictor of a favorable TNBC outcome.

Long-term soy consumption and tumor tissue MicroRNA and gene expression in triple-negative breast cancer

BACKGROUND

Soy food intake may have protective effects against the risk for breast cancer, including estrogen receptor (ER)-negative breast cancer. However, the underlying molecular mechanisms remain unclear.

METHODS

To evaluate the association of soy intake with the expression of microRNAs (miRNAs) and genes in the tumor tissue of patients with triple-negative breast cancer (TNBC; ie, breast cancer lacking expression of ER, progesterone receptor, and human epidermal growth factor receptor 2), the expression of 800 miRNAs and 302 genes were measured with NanoString nCounter assays in formalin-fixed, paraffin-embedded tumor tissue from 272 TNBC patients. Soy intake during the 1-year period before the cancer diagnosis was assessed with a validated food-frequency questionnaire. The association of soy intake with the expression of miRNAs and genes was evaluated via linear regression analysis with adjustments for patient age and TNM stage.

RESULTS

A total of 14 miRNAs and 24 genes were significantly associated with soy food intake (P < .05): Thirteen of the 14 miRNAs (92.9%) and 9 of the 24 genes (37.5%), including tumor suppressors miR-29a-3p and IGF1R, showed overexpression for those women with high soy intake, whereas the remaining miRNAs and genes, including oncogenes KRAS and FGFR4, showed underexpression. Furthermore, cell growth-related genes showed a predominantly underexpression pattern according to a comparison of tumor samples from women with high soy food intake and samples from women with lower soy food intake.

CONCLUSIONS

This study suggests that long-term prediagnosis soy intake may lead to increased expression of tumor suppressors and decreased expression of oncogenes, especially cell growth-related genes, in breast tumor tissues. Cancer 2016;122:2544-51. © 2016 American Cancer Society.

miR-655 suppresses epithelial-to-mesenchymal transition by targeting Prrx1 in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks effective targeted therapies. The epithelial-to-mesenchymal transition (EMT) is a key contributor in the metastatic process. In this study, we found that miR-655 was down-regulated in TNBC, and its expression levels were associated with molecular-based classification and lymph node metastasis in breast cancer. These findings led us to hypothesize that miR-655 overexpression may inhibit EMT and its associated traits of TNBC. Ectopic expression of miR-655 not only induced the up-regulation of cytokeratin and decreased vimentin expression but also suppressed migration and invasion of mesenchymal-like cancer cells accompanied by a morphological shift towards the epithelial phenotype. In addition, we found that miR-655 was negatively correlated with Prrx1 in cell lines and clinical samples. Overexpression of miR-655 significantly suppressed Prrx1, as demonstrated by Prrx1 3'-untranslated region luciferase report assay. Our study demonstrated that miR-655 inhibits the acquisition of the EMT phenotype in TNBC by down-regulating Prrx1, thereby inhibiting cell migration and invasion during cancer progression.

Differential Roles for DUSP Family Members in Epithelial-to-Mesenchymal Transition and Cancer Stem Cell Regulation in Breast Cancer

Dual-specificity phosphatases (DUSPs) dephosphorylate threonine/serine and tyrosine residues on their substrates. Here we show that DUSP1, DUSP4, and DUSP6 are involved in epithelial-to-mesenchymal transition (EMT) and breast cancer stem cell (CSC) regulation. DUSP1, DUSP4, and DUSP6 are induced during EMT in a PKC pathway signal-mediated EMT model. We show for the first time that the key chromatin-associated kinase PKC-θ directly regulates a subset of DUSP family members. DUSP1, DUSP4, and DUSP6 globally but differentially co-exist with enhancer and permissive active histone post-translational modifications, suggesting that they play distinct roles in gene regulation in EMT/CSCs. We show that nuclear DUSP4 associates with the key acetyltransferase p300 in the context of the chromatin template and dynamically regulates the interplay between two key phosphorylation marks: the 1834 (active) and 89 (inhibitory) residues central to p300’s acetyltransferase activity. Furthermore, knockdown with small-interfering RNAs (siRNAs) shows that DUSP4 is required for maintaining H3K27ac, a mark mediated by p300. DUSP1, DUSP4, and DUSP6 knockdown with siRNAs shows that they participate in the formation of CD44^hi/CD24^lo/EpCAM⁺ breast CSCs: DUSP1 knockdown reduces CSC formation, while DUSP4 and DUSP6 knockdown enhance CSC formation. Moreover, DUSP6 is overexpressed in patient-derived HER2⁺ breast carcinomas compared to benign mammary tissue. Taken together, these findings illustrate novel pleiotropic roles for DUSP family members in EMT and CSC regulation in breast cancer.

Clinicopathological significance of dual-specificity protein phosphatase 4 expression in invasive ductal carcinoma of the breast

Purpose

Dual-specificity protein phosphatase 4 (DUSP4), also known as mitogen-activated protein kinase phosphatase (MKP) 2 is a member of the inducible nuclear MKP group. The role of DUSP4 in cancer development and progression appears to vary with the type of malignancy. The purpose of this study was to investigate DUSP4 expression in a case series of invasive ductal carcinoma of the breast.

Methods

We constructed tissue microarrays consisting of 16, 14, 47, and 266 cases of normal breast tissue, usual ductal hyperplasia, ductal carcinoma in situ, and invasive ductal carcinoma, respectively. DUSP4 expression was investigated by immunohistochemistry.

Results

Cytoplasmic DUSP4 expression was observed. DUSP4 was more frequently expressed in malignant than in benign cases (p=0.024). The mean DUSP4 expression score was significantly higher in malignant tumors than in benign lesions (p=0.019). DUSP4 expression was significantly correlated with a larger tumor size (>2 cm, p=0.015). There was no significant correlation between overall survival or disease-free survival and DUSP4 expression in all 266 patients. We evaluated the impact of DUSP4 expression on the survival of 120 patients with T1-stage tumors. Interestingly, Kaplan-Meier survival curves revealed that DUSP4 expression had a significant effect on both overall patient survival (p=0.034, log-rank test) and disease-free survival (p=0.045, log-rank test). In early T-stage breast cancer, DUSP4 expression was associated with a worse prognosis.

Conclusion

DUSP4 is frequently upregulated in breast malignancy, and may play an important role in cancer development and progression. In addition, it may be a marker of adverse prognosis, especially in patients with early T1-stage cancer.