Expression of oestrogen receptor-beta in oestrogen receptor-alpha negative human breast tumours

To analyse the phenotype of breast tumours that express oestrogen receptor-beta (ERbeta) alone tissue microarrays were used to investigate if ERbeta isoforms are associated with specific prognostic markers and gene expression phenotypes in ERalpha-negative tumours. ERalpha-negative tumours were positive for ERbeta1 in 58% of cases (n=122/210), total ERbeta in 60% (n=115/192) and ERbeta2/cx in 57% of cases (n=114/199). Oestrogen receptor-beta1 and total ERbeta were significantly correlated with Ki67 (r=0.28, P<0.0001, n=209; r=0.29, P<0.0001, n=191) and with CK5/6, a marker of the basal phenotype (r=0.20, P=0.0106, n=170; r=0.18, P=0.0223, n=158). ERbeta2/cx was strongly associated with p-c-Jun and NF-kappaBp65 (r=0.53, P<0.0001, n=93; r=0.35, P<0.0001, n=176). This study shows that a range of ERbeta isoform expression occurs in ERalpha-negative breast tumours. While expression of ERbeta1, total and ERbeta2/cx are correlated, individual forms show associations with certain phenotypes that suggest different roles in subsets of ERalpha-negative cancers. Based on our in vivo observations, ERbeta may have the potential to become a therapeutic target in the specific subcohort of ERalpha-negative breast cancers.     

ERα和ERβ在非小细胞肺癌中作用的研究进展

摘 要　雌激素受体（estrogen receptor,ER）包括雌激素受体α（estrogen receptor alpha,ERα）和雌激素受体β（estrogen receptor beta,ERβ）,为类固醇激素核受体家族配体依赖性反式转录调节蛋白,包括N末端区、DNA结合区和C末端区3个主要功能域。ER在人类非小细胞肺癌（non-small cell lung cancer,NSCLC）组织、正常肺组织中均有表达,其表达与肺癌组织学类型相关。ERα与ERβ主要通过雌激素信号途径调节转录,通过生长因子受体途径和类固醇信号途径调节其在肿瘤细胞核的活性,进而影响肿瘤细胞的生长、分裂和代谢等生物学行为。ER高甲基化可能与肺肿瘤的发生有关,吸烟与肺癌的相关性在女性更明显,并非ERα影响烟草的致癌代谢。ERα或ERβ的表达是否为肺癌的有效预测因子需进一步确证。总之,ERα和ERβ与NSCLC的发生、发展和预后密切相关,基于ERα和ERβ的生物治疗也可能成为今后肺癌治疗的重要策略。     

Expression of the oestrogen regulated pNR-2 mRNA in human breast cancer: relation to oestrogen receptor mRNA levels and response to tamoxifen therapy

The pNR-2 mRNA is regulated by oestrogens in cell lines established from metastatic human breast cancer cells. The levels of the pNR-2 and oestrogen receptor RNAs have been measured in 96 tumour samples from patients undergoing surgery for breast cancer. Oestrogen receptor mRNA was detected in 90% of the 60 primary breast tumour samples from patients not receiving endocrine therapy at the time of surgery, whereas the pNR-2 RNA was detected in 57%. In primary tumours the expression of pNR-2 was entirely dependent upon oestrogen receptor RNA expression. When the 60 primary tumours were considered, pNR-2 and oestrogen receptor mRNA levels were significantly correlated. There was no significant correlation for pNR-2 positive tumours. pNR-2 mRNA levels were similar in tumours of pre- and post-menopausal patients and were independent of tumour differentiation and nodal status. Oestrogen receptor and pNR-2 mRNA levels were also measured in 21 tumour samples from patients receiving primary tamoxifen therapy. Eleven of these had shown an objective response and a significantly larger number of tumours from these patients contained pNR-2 mRNA than from patients who did not respond (chi 2 = 6.08, P less than 0.025).     

Metallothionein 1E mRNA is highly expressed in oestrogen receptor-negative human invasive ductal breast cancer

Metallothioneins (MTs), a group of ubiquitous metalloproteins, comprise isoforms encoded by ten functional genes in humans. Different MT isoforms possibly play different functional roles during development or under various physiological conditions. The MT-1E isoform mRNA has been recently shown to be differentially expressed in oestrogen receptor (OR)-positive and OR-negative breast cancer cell lines. In this study, we evaluated MT-1E mRNA expression via semi-quantitative RT-PCR in 51 primary invasive ductal breast cancer tissues, concurrently with OR-positive and progesterone receptor (PR)-positive MCF7 cells, OR-negative and PR-negative MDA-MB-231 cells and PR-transfected MDA-MB-231 breast cancer cells (ABC28). We demonstrated significantly higher MT-1E mRNA expression in OR-negative compared with OR-positive breast cancer tissues (P = 0.026). MCF7 cells lacked MT-1E mRNA expression, while both OR- and PR-negative MDA-MD-231 cells exhibited a high level of MT-1E mRNA expression. The level of MT-1E mRNA expression in progesterone-treated and -untreated ABC28 cells remained similar as the parental cell line MDA-MB-231-C2 cells. The results suggest that MT-1E may have specific and functional roles in OR-negative invasive ductal breast cancers, possibly mediated via effector genes downstream of the oestrogen receptor, but not through the PR pathway.     

Quantitative analysis of estrogen receptor-alpha and -beta messenger RNA expression in breast carcinoma by real-time polymerase chain reaction

BACKGROUND: Estrogen action is mediated not only through a classic estrogen receptor (ER) (ER-alpha) but also through a second ER (ER-beta) that has a structure and function similar to ER-alpha. A correlation between ER-beta mRNA expression with ER and progesterone receptor (PR) protein levels as well as prognostic factors remains to be established in breast carcinoma. METHODS: The authors conducted a quantitative analysis of ER-alpha and ER-beta mRNA expression in 116 breast tumors using real-time polymerase chain reaction (PCR), and investigated a possible correlation between ER-alpha and ER-beta mRNA expression and ER and PR status as determined by enzyme immunoassay as well as with various prognostic factors. RESULTS: ER-alpha mRNA levels were significantly (P < 0.01) higher in ER positive compared with ER negative tumors. Conversely, ER-beta mRNA levels were significantly (P < 0.01) lower in ER positive compared with ER negative tumors. Accordingly, the ratio of ER-beta to ER-alpha was significantly (P < 0.01) higher in ER negative compared with ER positive tumors. A subset analysis based on ER and PR status showed that ER-beta mRNA levels as well as the ratios of ER-beta to ER-alpha mRNA level were highest in ER negative and PR negative tumors (P < 0.05). ER-alpha mRNA levels were significantly (P < 0.05) higher in postmenopausal compared with premenopausal tumors. Histologic Grade 3 tumors showed a significant decrease in ER-alpha mRNA levels compared with Grade 1 and 2 tumors (P < 0.01 and P < 0.05, respectively). No significant correlation between ER-alpha and ER-beta mRNA levels and histologic type, tumor size, or lymph node status was observed. CONCLUSIONS: An absolute and relative increase in ER-beta mRNA levels in ER negative and PR negative breast tumors, which rarely respond to endocrine therapy, suggests the possible involvement of up-regulation of ER-beta mRNA in the development of estrogen-independent tumors.     

女性散发性基底细胞型乳腺癌ERα启动子甲基化的研究

目的:探讨ERα甲基化与基底细胞型乳腺癌发生发展的相关性。方法:用甲基化PCR研究60例散发性基底型乳腺癌ERα启动子甲基化情况,并研究其与临床病因素之间的关系。结果:女性散发性基底细胞型乳腺癌组织中ERα基因启动子甲基化发生率为80.0%(48/60)。ERα基因启动子甲基化与淋巴结转移情况、肿瘤分期、p53蛋白、BRCA-1蛋白和BRCA-2蛋白表达情况有相关性,与患者年龄及绝经状态无关。结论:ERα基因启动子甲基化在基底细胞型乳腺癌发生发展中可能起重要作用。     

Polymorphisms in the estrogen receptor-alpha gene and breast cancer risk

The estrogen receptor-alpha (ERalpha) has been known to play a role in the development and progression of breast cancer. Several genetic polymorphisms in the ERalpha gene have been related to breast cancer risk and/or different tumor characteristics. In this study, PCR and direct sequencing based methods were used to examine this issue further in a Korean study population consisting of 155 women, 110 with breast cancer and 45 without cancer. We also assessed the potential role of the ERalpha genotype in ER, PR, p53, c-erbB2, and bcl-2 expression. Only one of the allelic variants of ERalpha gene was found in our study subjects; the (C(975)G) change was present in half of the study subjects. Although this allele had no direct effect in individual breast cancer risk, it was positively associated with tumor PR (P for trend=0.04) and ER expression (P for trend=0.06) and negatively associated with p53 expression (P for trend=0.02).     

Monoallelic amplification of estrogen receptor-alpha expression in breast cancer

Gene amplification and loss of heterozygosity are alterations to chromosomal structure whereby tumor cells alter patterns of gene expression. We have identified a novel mechanism of gene regulation in which cancer cells predominantly express one of the two alleles of a gene. Estrogen receptor (ER)-alpha is overexpressed in hormone-responsive breast cancer compared with normal breast epithelial cells. Using a polymorphism of codon 10, we examined allele-specific expression of the four different ER promoters in MCF-7 breast cancer cells and primary tumors. Monoallelic amplification of expression (MAX) for all four ER promoters was identified, resulting in an allelic preference of > 100-fold. MAX was the result of an amplification of allele copy number and a preference to transcribe the amplified allele. The effect of MAX was most significant for the promoters clustered near the 1' exon, whereas the expression from the distant H promoter mirrored template copy number. MAX of the ER gene was not found to occur in normal endometrial or breast tissue. As a novel mechanism in cancer genetics, MAX can result in functional homozygosity at a gene locus.     

Sinophobic growth in oestrogen receptor-negative metastatic breast cancer

The mode of growth of tumour cells from primary breast carcinoma in the axillary nodes is shown to be related to the oestrogen receptor (ER) status of the primary tumour. ER-positive primaries are described as tending to show sinophilic growth, the tumour cells spreading along the nodal sinuses; while the ER-negative are sinophobic, spreading more diffusely in the lymphoid tissue.     

Effect of ethanol on proliferation and estrogen receptor-alpha expression in human breast cancer cells

There is substantial epidemiological evidence suggesting that alcohol consumption is associated with increased risk for breast cancer. However, possible biological mechanisms have not been clearly established. In the present studies, a direct effect of ethanol on the proliferation and intracellular content of cyclic AMP (cAMP) in two estrogen receptor-positive (ER+) and two estrogen receptor-negative (ER-) human breast cancer cell lines was examined. Treatment of ER+ human breast cancer cells (MCF-7 and ZR75.1) with ethanol at concentrations between 10 and 100 mM was associated with increased cell numbers compared to controls. The ERalpha content and the amount of intracellular cAMP also increased in ER+ cells exposed to ethanol, compared to controls. On the other hand, ethanol treatment did not increase cell proliferation or cAMP levels in the ER- (BT-20 and MDA-MB-231) human breast cancer cells. Therefore, ethanol added at physiologically relevant concentrations to ER+ human breast cancer cell cultures can enhance cell proliferation and increase the content of ERalpha.