Yan Shen1, Fang Yang1, Wenwen Zhang1, Wei Song2, Yuxiu Liu3, Xiaoxiang Guan1. 1. Department of Medical Oncology, Jinling Hospital, Medical School of Nanjing University, Nanjing, China. 2. Department of Medical Oncology, Jinling Hospital, Southern Medical University, Guangzhou, China. 3. Department of Medical Statistics, Jinling Hospital, Nanjing University, Nanjing, China.
Abstract
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.
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.
Authors: Pia Giovannelli; Marzia Di Donato; Giovanni Galasso; Erika Di Zazzo; Antonio Bilancio; Antimo Migliaccio Journal: Front Endocrinol (Lausanne) Date: 2018-08-28 Impact factor: 5.555