Aromatase inhibitor treatment of breast cancer cells increases the expression of let-7f, a microRNA targeting CYP19A1
Aromatase inhibitor treatment of breast cancer cells increases the expression of let-7f, a microRNA targeting CYP19A1
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DOI：
10.1002/path.4019
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发表时间：
2012-07-01
影响因子：
7.3
通讯作者：
Sasano, Hironobu
中科院分区：
文献类型：
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作者：
Shibahara, Yukiko;Miki, Yasuhiro;Sasano, Hironobu
芳香化酶抑制剂（AIs）被认为是雌激素受体阳性绝经后乳腺癌患者内分泌治疗的金标准。据报道，AI治疗导致癌组织中遗传谱的显著改变，但其详细的分子机制尚未阐明。因此，我们分析了与原代乳腺癌基质细胞共培养的MCF-7中来曲唑治疗前后的miRNA表达。来曲唑在体外显著改变了癌症miRNAs的表达谱。在来曲唑治疗后升高的miRNA中，计算分析鉴定了let-7 f，一种靶向芳香化酶基因（CYP 19 A1）表达的肿瘤抑制miRNA。使用MCF-7和SK-BR-3细胞以及新辅助研究的临床标本进行的定量实时PCR分析表明芳香化酶mRNA和let-7 f表达之间存在显著的负相关性。此外，let-7 f的高表达与乳腺癌中芳香化酶蛋白水平的低表达显著相关。3 'UTR荧光素酶分析结果也证明了CYP 19 A1中的实际let-7 f结合位点，表明let-7 f直接靶向芳香化酶基因。随后在let-7 f转染的MCF-7和SK-BR-3细胞中进行的WST-8和迁移测定显示其增殖和迁移显著减少。这些研究结果都表明，let-7 f是乳腺癌中的肿瘤抑制miRNA，直接靶向芳香化酶基因，并通过AI治疗恢复。因此，AI可能通过恢复let-7 f来抑制芳香化酶基因表达，从而对乳腺癌细胞产生肿瘤抑制作用。版权所有（c）2012大不列颠和爱尔兰病理学会。出版社：John Wiley & Sons，Ltd
Aromatase inhibitors (AIs) are considered the gold standard of endocrine therapy for oestrogen receptor-positive postmenopausal breast cancer patients. AI treatment was reported to result in marked alterations of genetic profiles in cancer tissues but its detailed molecular mechanisms have not been elucidated. Therefore, we profiled miRNA expression before and after treatment with letrozole in MCF-7 co-cultured with primary breast cancer stromal cells. Letrozole significantly altered the expression profiles of cancer miRNAs in vitro. Among the elevated miRNAs following letrozole treatment, computational analysis identified let-7f, a tumour-suppressor miRNA which targeted the aromatase gene (CYP19A1) expression. Quantitative real-time PCR assay using MCF-7 and SK-BR-3 cells as well as clinical specimens of a neoadjuvant study demonstrated a significant inverse correlation between aromatase mRNA and let-7f expression. In addition, high let-7f expression was significantly correlated with low aromatase protein levels evaluated by both immunohistochemistry and the western blotting method in breast cancer cases. Results of 3'UTR luciferase assay also demonstrated the actual let-7f binding sites in CYP19A1, indicating that let-7f directly targets the aromatase gene. Subsequent WST-8 and migration assays performed in let-7f-transfected MCF-7 and SK-BR-3 cells revealed a significant decrement of their proliferation and migration. These findings all demonstrated that let-7f, a tumour suppressor miRNA in breast cancer, directly targeted the aromatase gene and was restored by AI treatment. Therefore, AIs may exert tumour-suppressing effects upon breast cancer cells by suppressing aromatase gene expression via restoration of let-7f. Copyright (c) 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.