缺氧诱导乳腺癌雌激素受体α的下调

目的　探讨乳腺癌组织中雌激素受体α(ER α)的异质性表达与多种缺氧标志的关系。方法　 5 1例经配体结合法证实ER阳性的乳腺癌患者 ,采用免疫组织化学染色的方法观察其ER α的异质性表达与多种缺氧标志的关系 ,同时观察体外缺氧环境对乳腺癌细胞系ER α表达的影响及其特异性。结果　 4 9例乳腺癌为ER α阳性。无论乳腺导管内癌 (2 9例 )还是浸润性癌 (2 0例 ) ,ER α蛋白在邻近坏死灶的区域均下调 (P值分别≤ 0 .0 0 0 1) ;ER α的区域性下调还与缺氧诱导基因CA IX和Glut 1的表达有关 (P <0 .0 0 0 1)。缺氧可以直接诱导乳腺癌细胞系ER α蛋白和mRNA水平的下降 ,但其他一些应激因素 ,如低pH值、低糖及缺氧细胞的培养液等却无此作用。长时间、间歇性缺氧可以导致MCF 7细胞ER α表达的持久抑制。结论　乳腺癌ER α区域性的表达下降与缺氧有关 ,长时间、间歇性的缺氧可以持续性抑制ER α的表达。缺氧可能促使乳腺癌在进展过程中向ER α阴性的表型演变 ,并可能导致对内分泌治疗的耐药。

Hypoxia induces down-regulation of estrogen receptor alpha in human breast cancer

OBJECTIVE: To demonstrate the impact of hypoxia on ER-alpha in both breast cancer tissue and cell line, and its relationship with hypoxia-related parameters. METHODS: Expression of ER-alpha in 51 breast cancer patients with ER positive determined by ligand-binding assay was examined by immunohistochemistry and compared with CA-IX and Glut-1. Impact of hypoxia on breast cancer cell line MCF-7 (ER-alpha positive) was observed by Western Blot and RT-PCR. RESULTS: Of 51 breast cancer patients, 49 were ER-alpha positive. Regional decrease of ER-alpha expression was consistently observed in peri-necrotic regions as compared to distant regions in both in-situ carcinomas (n=29, P <0.0001) and invasive carcinomas (n=20, P=0.0001), which was closely associated with the induction of CA-IX and Glut-1 in hypoxia (P <0.0001). The decreased expression of ER-alpha protein and mRNA in breast cancer cell lines were attributed to hypoxia and not to other stress factors, such as reduced glucose, low pH, and products released from necrotic or hypoxic cells. Chronic intermittent hypoxia could cause persistent down-regulation of ER-alpha in the MCF-7 breast cancer cell line. CONCLUSION: Regional hypoxia in breast cancer is associated with the reduced ER-alpha expression, and intermittent hypoxia can cause persistent down-regulation. Hypoxia may therefore contribute to the progression of ER-alpha negative status and potentially to the development of resistance to endocrine therapy.