| Purpose and ContentThe breast cancer is an extraordinarily hormone-dependent tumor. Detection of estrogen receptor (ER) and progesterone receptor (PR) has become a routine method. There have been variable results regarding the clinical significance of androgen receptor (AR) in evaluating malignancy, prognosis in breast cancer and in its response to hormone therapy. Some recent studies have reported that the initiation, development, metastasis and drug resistance of breast cancer are related to some endogenous microRNAs. And AR also regulates the expression of some microRNAs. These suggest AR may change the intracellular genetic procedure via microRNAs. It is just the molecular basis of cell canceration and malignant behaviour. The aim of this study was to evaluate the expression of AR in the breast cancers and to clarify its relationship with prognosis, clinicopathological and biological characteristics, and the implications were evaluated in molecular subgroups. Further, we observe the biological effect of AR in ER-positive and ER-negative breast cancer cell lines, and identify differentially up-regulated and down-regulated microRNAs after androgen dihydrotestosterone (DHT) treatment, to search for the AR-related microRNAs.Materials and methods1. The expression of AR was analyzed by immunohistochemistry on paraffin-embedded tumor tissues of the breast, and compared with patient outcome, with the degree of differentiation, tumor size, nodes, the ER, PR and human epidermal growth factor receptor 2 (HER-2) status, and its implications were evaluated in five molecular subgroups.2. By western blot, we analyzed AR expression in ER-positive MCF-7 and ER-negative MDA-MB-453 breast cancer cell lines.3. By MTT assays, cell proliferation was determined after DHT treatment.4. Cell cycle was analyzed by flow cytology.5. MicroRNA array hybridization technique was used to screen the up-regulated and down-regulated microRNAs in the two breast cancer cell lines after DHT treatment6. The identified differentially up-regulated and down-regulated microRNAs were checked using real time RT-PCR. 7. The target genes were predicted by computer software.Results1. A greater percentage (72.5%) of breast cancer cases displayed nuclear immunoreactivity for AR, and AR expression was found in 53.2% of ER, PR-negative cases. AR expression was related to that of ER (P<0.001) and PR (P=0.035), but not correlated with the other conventional parameters. The majority (61.0%) of basal-like breast cancers showed loss of AR expression (P<0.001), which had poor prognosis. Among the subgroups, except HER-2 overexpressing subgroup, the hazard ratios for occurrence of relapse, metastasis or death for those AR positive were lower than that of AR negative tumors in luminal A, luminal B, basal-like, and normal-like subgroups (P=0.019,0.044,0.034 and 0.032 respectively). The disease-free survival curves revealed patients with AR expression had a more favorable prognosis than those without expression (P=0.006, P=0.013,P=0.036 and P=0.010).2. DHT increased AR expression in the two breast cancer cell lines. AR pathway was shown to inhibit ER-positive MCF-7 and ER-negative MDA-MB-453 proliferation. In cell cycle, the proportions of G1 phase cells increased, while S cells decreased.3. The identified microRNA up-regulated over 1.5-fold was hsa-miR-30c, and the down-regulated over 1.5-fold were hsa-miR-7, hsa-miR-518b. Rresults of realtime RT-PCR were consistent with that of microRNA array.4. Forty target genes of hsa-miR-7,191 of hsa-miR-30c, and 11 of hsa-miR-518b were predicted.ConclusionsThe detection of AR may help improve the molecular typing of breast cancer and provide theoretical evidence for individualized treatment. AR pathway may inhibit ER-negative MDA-MB-453 breast cell proliferation as well as ER-positive MCF-7, by suppressing the process of G1 to S phase progression. The androgen receptor related microRNAs which may contribute to breast cancer carcinogenesis and development include hsa-miR-30c, hsa-miR-7, hsa-miR-518b.
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