Wei Song

Antiproliferative Effect of Androgen Receptor Inhibition in Mesenchymal Stem-Like Triple-Negative Breast Cancer.

Background/Aims: Androgen receptor (AR), a steroid hormone receptor, has recently emerged as prognostic and treatment-predictive marker in breast cancer. Previous studies have shown that AR is widely expressed in up to one-third of triple-negative breast cancer (TNBC). However, the role of AR in TNBC is still not fully understood, especially in mesenchymal stem-like (MSL) TNBC cells. Methods: MSL TNBC MDA-MB-231 and Hs578T breast cancer cells were exposed to various concentration of agonist 5-α-dihydrotestosterone (DHT) or nonsteroidal antagonist bicalutamide or untreated. The effects of AR on cell viability and apoptosis were determined by MTT assay, cell counting, flow cytometry analysis and protein expression of p53, p73, p21 and Cyclin D1 were analyzed by western blotting. The bindings of AR to p73 and p21 promoter were detected by ChIP assay. MDA-MB-231 cells were transplanted into nude mice and the tumor growth curves were determined and expression of AR, p73 and p21 were detected by Immunohistochemistry (IHC) staining after treatment of DHT or bicalutamide. Results: We demonstrate that AR agonist DHT induces MSL TNBC breast cancer cells proliferation and inhibits apoptosis in vitro. Similarly, activated AR significantly increases viability of MDA-MB-231 xenografts in vivo. On the contrary, AR antagonist, bicalutamide, causes apoptosis and exerts inhibitory effects on the growth of breast cancer. Moreover, DHT-dependent activation of AR involves regulation in the cell cycle related genes, including p73, p21 and Cyclin D1. Further investigations indicate the modulation of AR on p73 and p21 mediated by direct binding of AR to their promoters, and DHT could make these binding more effectively. Conclusions: Our study demonstrates the tumorigenesis role of AR and the inhibitory effect of bicalutamide in AR-positive MSL TNBC both in vitro and in vivo, suggesting that AR inhibition could be a potential therapeutic approach for AR-positive TNBC patients.

Lin28B Expression Correlates with Aggressive Clinicopathological Characteristics in Breast Invasive Ductal Carcinoma

Lin28B is a RNA-binding protein that inhibits the let-7 microRNA family and acts as an oncogene in various human malignant diseases. Conversely, the members of let-7 family function as tumor suppressers and are often inactivated in cancers. The interaction of Lin28B/let-7 plays a crucial part of tumorigenesis. In this study, the authors examined the Lin28B expression using immunohistochemistry in 190 breast cancers and analyzed the correlation of Lin28B immunostaining and clinicopathological characteristics. Breast cancer patients previously diagnosed with invasive ductal carcinomas were enrolled in this study. All cases went through surgical procedures as the initial treatment. The characteristics of every case were collected, including tumor size, pathologic grade, metastatic lymphoid nodes, and estrogen receptor α (ERα), progesterone receptor (PR), and HER2 status. The immunostaining was scored by two independent investigators. Eighty-three (43.7%) of 190 cases showed positive expression of Lin28B. Lin28B immunostaining was increased in tumors compared with the adjacent tissues. Overexpression of Lin28B was linked to poor differentiation, advanced-stage disease, and Ki67-positive status (all p<0.05). Besides, Lin28B expression was significantly different among breast cancer subtypes. This study addresses the role of Lin28B in breast cancers and provides insight of its predictive effects in disease development.

TAp73 and ΔNp73 have opposing roles in 5-aza-2'-deoxycytidine-induced apoptosis in breast cancer cells.

The p73 gene contains an extrinsic P1 promoter and an intrinsic P2 promoter, controlling the transcription of the pro-apoptotic TAp73 isoform and the anti-apoptotic ΔΝp73 isoform, respectively. The DNA methylation status of both promoters act equally in the epigenetic transcriptional regulation of their relevant isoforms. The aim of this study was to analyze the different effects of these p73 isoforms in 5-aza-2′-deoxycytidine (5-aza-dC)-induced apoptosis in breast cancer cells. We investigated the effects of the DNA demethylation agent, 5-aza-dC, on the T-47D breast cancer cell line, and evaluated the methylation status of the p73 promoters and expression of TAp73 and ΔNp73. Furthermore, we assessed the expression of p53 and p73 isoforms in 5-aza-dC-treated T-47D cells and p53 knockout cells. 5-aza-dC induced significant anti-tumor effects in T-47D cells, including inhibition of cell viability, G1 phase arrest and apoptosis. This was associated with p73 promoter demethylation and a concomitant increase in TAp73 mRNA and protein expression. In contrast, the methylation status of promoter P2 was not associated with ΔNp73 mRNA or protein levels. Furthermore, demethylation of P2 failed to inhibit the expression of ΔNp73 with 5-aza-dC in the p53 knockdown cell model. Our study suggests that demethylation of the P1 and P2 promoters has opposite effects on the expression of p73 isoforms, namely up-regulation of TAp73 and down-regulation of ΔΝp73. We also demonstrate that p53 likely contributes to 5-aza-dC-induced ΔNp73 transcriptional inactivation in breast cancer cells.

Corrigendum: PARP inhibitor increases chemosensitivity by upregulating miR-664b-5p in BRCA1-mutated triple-negative breast cancer

Scientific Reports 7: Article number: 42319; published online: 08 February 2017; updated: 16 March 2017 This Article contains an error in Figure 4A where the graphs were labelled incorrectly. The correct Figure 4A appears below as Figure 1.

The Androgen Receptor Promotes Cellular Proliferation by Suppression of G-Protein Coupled Estrogen Receptor Signaling in Triple-Negative Breast Cancer

Background/Aims: The targeted therapy for triple-negative breast cancer (TNBC) is still challenging due to poor understanding on its molecular etiology. The androgen receptor (AR) has recently emerged as a prognostic and treatment-predictive marker in breast cancer. However, the role of AR in TNBC remained elusive. Methods: Immunohistochemistry (IHC) was used to detect AR and G-protein coupled estrogen receptor (GPER) expression in tissue microarrays of 165 TNBC patients. Microarray analysis of mRNAs was performed to identify downstream regulators of AR. TNBC cells were cultured with dihydrotestosterone (DHT) alone or in combination with AR knockdown performed with AR shRNA. Cell viability and colony formation were assessed. Western blotting and qRT-PCR were used to examine protein and mRNA expression, respectively. The potential mechanism of AR-mediated GPER suppression was identified by Chromatin immunoprecipitation (ChIP) assay. AR and GPER expressions were also assessed in nude mouse xenografts by IHC. Results: IHC staining showed that the expression of AR was positively associated with tumor size, lymph node metastasis and high-grade tumor in TNBC patients. AR activation triggered by DHT suppressed GPER expression, to promote cell growth of TNBC. G-1, a GPER agonist, inhibited DHT-stimulated proliferation. Further experiments illustrated that AR suppressed GPER activation via binding directly to the promoter of GPER. Moreover, a negative correlation between AR and GPER was observed in MDA-MB-231 tumor cell xenografts and TNBC patient samples. Conclusions: The suppression of GPER via AR may be involved in the positive actions towards the TNBC progression, making it a promising therapeutic target for TNBC treatment.

p27 Kip1 and Ser10-phosphorylated p27 Kip1 in breast cancer: clinical significance and expression

Background The protein p27 (p27Kip1) is a member of the cyclin-dependent kinase inhibitor family, which negatively regulates cell cycle progression, and the phosphorylation of p27 has been proven to affect its stability and nuclear export. Clinical studies on the relation between p27 and phosphorylated p27 (p-p27Ser10) in breast invasive ductal carcinomas are still scarce. Methods We examined the expression of p27 and p-p27Ser10 using immunohistochemistry in 107 breast invasive ductal carcinomas and analyzed the relationship of these biomarkers and tumor characteristics. Results Of the 107 tumor samples, 38.3% (41 of 107) overexpressed p27 and 64.5% (69 of 107) overexpressed p-p27Ser10. Analysis of correlation with clinical characteristics showed that high expression level of p-p27Ser10 was linked to poor differentiation, advanced disease stage, and lymph node metastasis, whereas a contrary trend was observed for p27 (all P<0.05). In addition, the expression of p-p27Ser10 was significantly higher in malignant tumors than in adjacent tissues, while p27 showed the opposite trend. Also, there were different levels of p27 and p-p27Ser10 in different types of breast cancer. Conclusion p27 and p-p27Ser10 are involved in the development of invasive ductal carcinoma and are potential indicators to judge the degree of malignancy as well as recurrence and metastasis.

miR‐1470 mediates lapatinib induced p27 upregulation by targeting c‐jun

Our previous study indicated that lapatinib induces p27‐dependent G1 arrest through both transcriptional and post‐translational mechanisms. Using miRNA microarray technology and quantitative RT‐PCR, we further investigated the potential miRNAs that involved in p27 upregulation and Her‐2 signaling pathway alteration with lapatinib treatment. A subset of 7 miRNAs was significantly affected in both 0.5 µM and 2.0 µM and 24 h and 48 h lapatinib treatment. Among them, only miR‐1470, miR‐126, and miR‐1208 were identified in the Her‐2 pathway after KEGG pathway analysis. However, luciferase reporter assay confirmed that miR‐1470 directly recognized the 3′‐untranslated region of c‐jun transcripts, which was consistent with TargetScan analysis. miR‐1470 significantly decreased c‐jun expression, thus miR‐1470 may repressc‐jun activation of cyclinD1 expression, and consequently promoted the upregulation of p27, a key molecule in the cell cycle arrest. Taken together, the present study provided the first evidences that miR‐1470 mediated lapatinib induced p27 upregulation by targeting c‐jun. J. Cell. Physiol. 230: 1630–1639, 2015.