Induction of acquired resistance to antiestrogen by reversible mitochondrial DNA depletion in breast cancer cell line

Although the net benefits of tamoxifen in adjuvant breast cancer therapy have been proven, the recurrence of the cancer in an aggressive and hormone independent form has been highly problematic. We previously demonstrated the important role mitochondrial DNA (mtDNA) plays in hormone-independence in prostate cancer. Here, the role of mtDNA in breast cancer progression was investigated. We established hydroxytamoxifen (4-OHT) resistant HTRMCF by growing MCF-7, human breast adenocarcinoma cells, in the presence of 4-OHT. HTRMCF was cross-resistant to 4-OHT and ICI182,780 concurrent with the depletion of mtDNA. To further investigate the role of mtDNA depletion, MCF-7 was depleted of mtDNA by treatment with ethidium bromide. MCF Rho 0 was resistant to both 4-OHT and ICI182,780. Furthermore, cybrid (MCFcyb) prepared by fusion MCF Rho 0 with platelet to transfer mtDNA showed susceptibility to antiestrogen. Surprisingly, after withdrawal of 4-OHT for 8 weeks, HTRMCF and their clones became susceptible to both drugs concurrent with a recovery of mtDNA. Herein, our results substantiated the first evidence that the depletion of mtDNA induced by hormone therapy triggers a shift to acquired resistance to hormone therapy in breast cancer. In addition, we showed that mtDNA depletion can be reversed, rendering the cancer cells susceptible to antiestrogen. The fact that the hormone independent phenotype can be reversed should be a step toward more effective treatments for estrogen-responsive breast cancer.     

BCAR1基因与乳腺癌抗雌激素药物耐药的相关研究

乳腺癌抗雌激素药物耐药是导致雌激素受体阳性患者内分泌治疗失败的重要原因之一。BCAR1／p130Cas蛋白能在活体外诱导雌激素依赖性乳腺癌细胞对抗雌激素药物产生耐药,是内分泌治疗的重要耐药因子,其诱导机制尚不能确定。但研究表明检测BCAR1／p130Cas蛋白表达水平可以提示乳腺癌临床内分泌治疗的效果。     

BCAR1基因与乳腺癌抗雌激素药物耐药的相关研究

乳腺癌抗雌激素药物耐药是导致雌激素受体阳性患者内分泌治疗失败的重要原因之一。BCAR1/p130Cas蛋白能在活体外诱导雌激素依赖性乳腺癌细胞对抗雌激素药物产生耐药,是内分泌治疗的重要耐药因子,其诱导机制尚不能确定。但研究表明检测BCAR1/p130Cas蛋白表达水平可以提示乳腺癌临床内分泌治疗的效果。     

A combined analysis of genome-wide association studies in breast cancer

In an attempt to identify common disease susceptibility alleles for breast cancer, we performed a combined analysis of three genome-wide association studies (GWAS), involving 2,702 women of European ancestry with invasive breast cancer and 5,726 controls. Tests for association were performed for 285,984 SNPs. Evidence for association with SNPs in genes in specific pathways was assessed using a permutation-based approach. We confirmed associations with loci reported by previous GWAS on 1p11.2, 2q35, 3p, 5p12, 8q24, 10q23.13, 14q24.1 and 16q. Six SNPs with the strongest signals of association with breast cancer, and which have not been reported previously, were typed in two further studies; however, none of the associations could be confirmed. Suggestive evidence for an excess of associations was found for genes involved in the regulation of actin cytoskeleton, glycan degradation, alpha-linolenic acid metabolism, circadian rhythm, hematopoietic cell lineage and drug metabolism. Androgen and oestrogen metabolism, a pathway previously found to be associated with the development of postmenopausal breast cancer, was marginally significant (P = 0.051 [unadjusted]). These results suggest that further analysis of SNPs in these pathways may identify associations that would be difficult to detect through agnostic single SNP analyses. More effort focused in these aspects of oncology can potentially open up promising avenues for the understanding of breast cancer and its prevention.     

Histone deacetylase-1 and -3 protein expression in human breast cancer: a tissue microarray analysis

Summary Impaired histone acetylation was recognized to be involved in carcinogenesis. Furthermore, histone deacetylase (HDAC) inhibitors induce differentiation of breast cancer cells and inhibit tumour growth. These results prompted us to study HDAC-1 and -3 expression in breast tumours to establish their potential therapeutic and prognostic significance.HDAC-1 und HDAC-3 protein expression was analyzed immunohistochemically on a tissue microarray (TMA) containing 600 core biopsies from 200 patients. HDAC-1 and -3 expression was correlated to steroid hormone receptor-, Her2/neu- and proliferation status of tumours as well as to overall and disease free survival.Moderate or strong nuclear immunoreactivity for HDAC-1 was observed in 39.8% and for HDAC-3 in 43.9% of breast carcinomas. HDAC-1 and -3 expression correlated significantly with oestrogen and progesterone receptor expression (both p< 0.001). HDAC-1 expression predicted significantly better disease free survival (DFS: p=0.044), in particular, in patients with small tumours of all differentiation types (DFS: p=0.016). Multivariate analysis demonstrated that HDAC-1 is an independent prognostic marker.Our data suggest that evaluation of HDAC-1 protein expression enables a more precise assessment of the prognosis of breast cancer patients. Thus, HDAC-1 expression analysis might be clinically useful to facilitate an individual, risk-directed, adjuvant systemic therapy in breast cancer patients.     

A combined comparative genomic hybridization and expression microarray analysis of gastric cancer reveals novel molecular subtypes

Comparative genomic hybridization (CGH), microsatellite instability (MSI) assays, and expression microarrays were used to molecularly subclassify a common set of gastric tumor samples. We identified a number of novel genomic aberrations associated with gastric cancer and discovered that gastric tumors could be grouped by their expression profiles into three broad classes: "tumorigenic," "reactive," and "gastric-like." Patients with gastric-like tumors exhibited a significantly better overall survival than patients belonging to the other two classes (P < 0.05). A novel supervised learning methodology for multiclass prediction was used to identify optimal predictor gene sets that accurately predicted the class of an unknown tumor sample. These predictor sets may prove useful in the development of new diagnostic applications for gastric cancer staging and prognostication.     

A genome-wide association study of chemotherapy-induced alopecia in breast cancer patients

Introduction

Chemotherapy-induced alopecia is one of the most common adverse events caused by conventional cytotoxic chemotherapy, yet there has been very little progress in the prevention or treatment of this side effect. Although this is not a life-threatening event, alopecia is very psychologically difficult for many women to manage. In order to improve the quality of life for these women, it is important to elucidate the molecular mechanisms of chemotherapy-induced alopecia and develop ways to effectively prevent and/or treat it. To identify the genetic risk factors associated with chemotherapy-induced alopecia, we conducted a genome-wide association study (GWAS) using DNA samples from breast cancer patients who were treated with chemotherapy.

Methods

We performed a case-control association study of 303 individuals who developed grade 2 alopecia, and compared them with 880 breast cancer patients who did not show hair loss after being treated with conventional chemotherapy. In addition, we separately analyzed a subset of patients who received specific combination therapies by GWASs and applied the weighted genetic risk scoring (wGRS) system to investigate the cumulative effects of the associated SNPs.

Results

We identified an SNP significantly associated with drug-induced grade 2 alopecia (rs3820706 in CACNB4 (calcium channel voltage-dependent subunit beta 4) on 2q23, P = 8.13 × 10^-9, OR = 3.71) and detected several SNPs that showed some suggestive associations by subgroup analyses. We also classified patients into four groups on the basis of wGRS analysis and found that patients who classified in the highest risk group showed 443 times higher risk of antimicrotubule agents-induced alopecia than the lowest risk group.

Conclusions

Our study suggests several associated genes and should shed some light on the molecular mechanism of alopecia in chemotherapy-treated breast cancer patients and hopefully will contribute to development of interventions that will improve the quality of life (QOL) of cancer patients.     

乳腺癌耐药蛋白在乳腺癌组织中的表达及与预后关系

目的研究乳腺癌耐药蛋白（Breast cancer resistance protein,BCRP）在乳腺癌组织中的表达,评估其在乳腺癌预后中的作用。方法采用免疫组织化学方法（Immunohistochemistry,IHC）检测47例手术切除的乳腺癌组织中BCRP的表达,并分析其与临床、病理特征的关系及对预后的影响。结果（1）BCRP在乳腺癌组织中的阳性表达率为55．3％（26／47例）,其中高表达者13例（27．7％）;（2）激素受体阳性者BCRP表达水平明显高于激素受体阴性者（P〈0．05）,BCRP表达与月经状况、肿瘤大小、腋淋巴结转移和组织分级均无关（P〉0．05）;（3）Kaplan—Meier生存分析结果表明BCRP和无病生存期相关（P〈0．05）,但和总生存期无关（P〉0．05）;（4）Cox单因素分析显示肿瘤大小和BCRP表达与无病生存期明显相关（P〈0．05）,而肿瘤大小和总生存期也明显相关（P〈0．05）;在多因素分析中BCRP表达仅和无病生存期明显相关,此外腋淋巴结转移与无病生存期和总生存期均明显相关（P〈0．05）。结论BCRP在乳腺癌组织中具有较高的表达水平,但与乳腺癌患者预后无关。     

Tissue microarray analysis of connexin expression and its prognostic significance in human breast cancer

Breast cancer accounts for approximately 15% of all cancer deaths. Currently, axillary nodal status is the most reliable prognostic indicator for breast cancer. Tumor size and histological grade are used to stage breast cancer. Estrogen receptor/progesterone receptor (ER/PR) and HER-2/neu status are useful in predicting patient survival and relapse. Ki67, an indicator of proliferative activity, also correlates well with prognosis. Connexin proteins form gap junction channels, permitting intercellular exchange of ions and small molecules. Reduced connexin protein levels and impaired gap junctional intercellular communication are associated with tumor phenotypes. This study investigated the prognostic value of connexin proteins as breast cancer markers. Tissue microarrays, containing 438 cases of invasive breast carcinoma, were stained with Cx26, Cx32, and Cx43 antibodies. The degree of connexin immunoreactivity was determined and then correlated with patient outcome, tumor grade, tumor size, lymph node status, and immunohistochemical markers, such as p53, ER/PR status, Ki67 and c-erbB-2 expression. Cx26, Cx32, or Cx43 did not correlate well with tumor grade, tumor size, p53 or c-erbB-2 status. There was an inverse correlation between Cx32 and lymph node status (P <0.05) and a positive correlation between Cx43 and PR status (P <0.01). Cx32 and Cx43 correlated positively with ER status (P <0.01). Cx43 correlated negatively with Ki67 expression (P <0.01). Cx26, Cx32, and Cx43 did not correlate with patient outcome. Based on our observations in this study, connexin proteins do not appear to be reliable indicators of breast cancer prognosis.     

乳腺癌多药耐药机制研究进展

近年来对乳腺癌的MDR机制研究不断深入 ,主要从基础和临床两方面对此予以综述。     

Intrinsic and acquired resistance to HER2-targeted therapies in HER2 gene-amplified breast cancer: mechanisms and clinical implications

Approximately 25% of human breast cancers overexpress the HER2 (ErbB2) proto-oncogene, which confers a more aggressive tumor phenotype and associates with a poor prognosis in patients with this disease. Two approved therapies targeting HER2, the monoclonal antibody trastuzumab and the tyrosine kinase inhibitor lapatinib, are clinically active against this type of breast cancer. However, a significant fraction of patients with HER2+ breast cancer treated with these agents eventually relapse or develop progressive disease. This suggests that tumors acquire or possess intrinsic mechanisms of resistance that allow escape from HER2 inhibition. This review focuses on mechanisms of intrinsic and/or acquired resistance to HER2-targeted therapies that have been identified in preclinical and clinical studies. These mechanisms involve alterations to HER2 itself, coexpression or acquisition of bypass signaling through other receptor or intracellular signaling pathways, defects in mechanisms of cell cycle regulation or apoptosis, and host factors that may modulate drug response. Emerging clinical evidence already suggests that combinations of therapies targeting HER2 as well as these resistance pathways will be effective in overcoming or preventing resistance.     

乙醛脱氢酶1与乳腺癌耐药蛋白在乳腺癌中的表达及相关性研究

背景与目的：乳腺癌患者对化疗药物耐药是导致化疗失败的主要原因。有研究证实,肿瘤干细胞标志物乙醛脱氢酶1(aldehyde dehydrogenase 1,ALDH1)与某些抗癌药物(如环磷酰胺、顺铂等)的耐药有关,并发现经这些药物治疗后的患者癌灶细胞中ALDH1的含量较治疗前高。乳腺癌耐药蛋白(breast cancerresistance protein,BCRP)不仅在正常组织中表达,更高表达于治疗后的乳腺癌中,提示这可能与肿瘤耐药机制相关。关于在乳腺癌患者中两者是否存在共表达的研究很少,本研究主要探讨ALDH1、BCRP与临床病理特征的关系及两种蛋白表达之间的相关性。方法：采用免疫组化法检测乳腺浸润性导管癌组织石蜡切片中ALDH1与BCRP的表达,研究并探讨它们与临床病理特征的关系以及两者表达之间是否有相关性。结果：ALDH1、BCRP在乳腺癌及癌旁乳腺组织中表达差异有统计学意义(χ²=14.685,P=0.000;χ²=12.243,P=0.000)。ALDH1的表达与患者年龄、病理分期、腋窝淋巴结转移、组织学分级及雌激素受体(estrogen receptor,ER)、孕激素受体(progesterone receptor,PR)、人类表皮生长因子受体(human epidermal growth factor receptor,HER-2)状态均无关(P>0.05);BCRP的表达与HER-2高表达有关,HER-2高表达组的癌组织中BCRP阳性表达率较高,差异有统计学意义(χ²＝5.289,P＝0.021)。BCRP的表达与患者年龄、肿瘤分化程度、腋窝淋巴结转移、病理分期及ER、PR状态无关(P>0.05);乳腺癌肿瘤干细胞标志物ALDH1与BCRP无相关性(r=-0.039,P=0.786)。结论：ALDH1可能是区别于其他耐药蛋白的一种独立的生物学因子,参与乳腺癌的化疗耐药或肿瘤的侵袭、转移等恶性生物学行为。     

Different mechanisms of acquired resistance to fluorinated pyrimidines in human colorectal cancer cells

5-Fluorouracil (5-FU), 5-fluoro-2'-deoxyuridine (FdUrd) and 5-trifluorothymidine (F3(d)Thd) are antimetabolites which are metabolized to their corresponding active forms which inhibit DNA synthesis via inhibition of thymidylate synthase (TS). To investigate ways of overcoming 5-FU-resistance, we established acquired-resistant colorectal cancer cell lines against these three drugs by continuous and step-wise escalation of drugs, and analyzed the cytotoxicity and the mechanism of resistance to the drugs. When cells were incubated with the 3 drugs for 72 h, the resistance ratio to parental DLD-1 human colorectal tumor cells was 65.2 for DLD-1/5-FU, 9.7 for DLD-1/FdUrd and 448.6 for DLD-1/F3(d)Thd cells. DLD-1/5-FU cells did not show any cross-resistance against FdUrd and F(3)dThd. However, DLD-1/FdUrd cells showed 3- and 9-fold increased resistance to 5-FU and F3(d)Thd, respectively, and DLD-1/F3(d)Thd cells also showed about 90-fold resistance to FdUrd. Analysis of enzyme activities and gene expression associated with pyrimidine metabolism indicated that a significant decrease in orotate phosphoribosyltransferase activity in DLD-1/5-FU cells, a 7-fold increase of TS mRNA in DLD-1/FdUrd cells, and a 37-fold decrease in thymidine kinase activity of DLD-1/F3(d)Thd cells were the major mechanisms of drug resistance. These findings were closely associated with the cytotoxicity of 5-FU, FdUrd and F3(d)Thd against the established 5-FU-, FdUrd- or F3(d)Thd-resistant cells. When DLD-1/FdUrd cells expressing increased TS mRNA were treated with FdUrd and F3(d)Thd for only 4 h, the resistance ratios of DLD-1/FdUrd cells to parental DLD-1 cells were markedly different for FdUrd and F3(d)Thd, suggesting that the cytotoxicity with short-time exposure to F3(d)Thd is due to a mechanism other than TS inhibition, although the cytotoxicity of F3(d)Thd in the short-time is low compared to that of long-time exposure. In conclusion, F3(d)Thd, an antimetabolite that inhibits TS activity, may be effective against 5-FU and/or FdUrd-resistance in colorectal cancer cells caused by amplification of TS and/or deletion of orotate phosphoribosyltransferase.     

A genome-wide linkage study of mammographic density, a risk factor for breast cancer

Introduction

Mammographic breast density is a highly heritable (h² > 0.6) and strong risk factor for breast cancer. We conducted a genome-wide linkage study to identify loci influencing mammographic breast density (MD).

Methods

Epidemiological data were assembled on 1,415 families from the Australia, Northern California and Ontario sites of the Breast Cancer Family Registry, and additional families recruited in Australia and Ontario. Families consisted of sister pairs with age-matched mammograms and data on factors known to influence MD. Single nucleotide polymorphism (SNP) genotyping was performed on 3,952 individuals using the Illumina Infinium 6K linkage panel.

Results

Using a variance components method, genome-wide linkage analysis was performed using quantitative traits obtained by adjusting MD measurements for known covariates. Our primary trait was formed by fitting a linear model to the square root of the percentage of the breast area that was dense (PMD), adjusting for age at mammogram, number of live births, menopausal status, weight, height, weight squared, and menopausal hormone therapy. The maximum logarithm of odds (LOD) score from the genome-wide scan was on chromosome 7p14.1-p13 (LOD = 2.69; 63.5 cM) for covariate-adjusted PMD, with a 1-LOD interval spanning 8.6 cM. A similar signal was seen for the covariate adjusted area of the breast that was dense (DA) phenotype. Simulations showed that the complete sample had adequate power to detect LOD scores of 3 or 3.5 for a locus accounting for 20% of phenotypic variance. A modest peak initially seen on chromosome 7q32.3-q34 increased in strength when only the 513 families with at least two sisters below 50 years of age were included in the analysis (LOD 3.2; 140.7 cM, 1-LOD interval spanning 9.6 cM). In a subgroup analysis, we also found a LOD score of 3.3 for DA phenotype on chromosome 12.11.22-q13.11 (60.8 cM, 1-LOD interval spanning 9.3 cM), overlapping a region identified in a previous study.

Conclusions

The suggestive peaks and the larger linkage signal seen in the subset of pedigrees with younger participants highlight regions of interest for further study to identify genes that determine MD, with the goal of understanding mammographic density and its involvement in susceptibility to breast cancer.     

Use of comparative proteomics to identify potential resistance mechanisms in cancer treatment

Drug resistance is a major problem in successful cancer chemotherapy. Many molecular mechanisms that are responsible for drug resistance are known whereas others have yet to be discovered. Determining the exact mechanism activated in a particular case (clinical or laboratory) is a difficult task. Recently, proteomics has been applied to investigate drug resistance mechanisms in model cancer cell lines. As a result, novel mechanisms of resistance have been discovered and known mechanisms of resistance confirmed. In this paper, we wish to review recent developments and progresses in the application of proteomic tools to identify known and novel drug resistance mechanisms in drug-selected model cancer cell lines. Our combined analyses of multiple proteomic studies of various drug resistant cancer cell lines revealed that many mechanisms of resistance likely exist in any given drug-selected cancer cell line and that common mechanisms of resistance may be selected in a spectrum of cancer cell lines. These observations suggest that combination therapies targeting multiple mechanisms to sensitize drug resistant cancers may be necessary to eradicate cancers in the future.     

Expression microarray analysis and oligo array comparative genomic hybridization of acquired gemcitabine resistance in mouse colon reveals selection for chromosomal aberrations

Gemcitabine is a commonly used therapy for many solid tumors. Acquired resistance to this nucleoside analogue, however, diminishes the long-term effectiveness in a majority of patients. To better define the molecular background of gemcitabine resistance, a mouse colon tumor was selected during successive rounds of transplantation with continued treatment of gemcitabine. Expression microarray analysis was applied to determine which genes are consistently and highly overexpressed or underexpressed in the resistant versus the nonresistant tumor. For the statistical interpretation of the microarray data, a parametric model was implemented, which returns model-based differential gene expression (log-) ratios and their uncertainties. This defined a set of 13 genes, putatively responsible for the gemcitabine resistance in solid tumors. One of these, RRM1, was previously identified as an important marker for gemcitabine resistance in human cell lines. Five of the 13 genes, including RRM1, are located within a 3 Mb region at chromosome 7E1 of which four are highly overexpressed, suggesting a chromosomal amplification. Therefore, chromosomal copy number changes were measured, using oligo array comparative genomic hybridization. A narrow and high amplification area was identified on 7E1 that encompassed all five genes. In addition, reduced RNA expression of two other genes at 8E1 encoding COX4I1 and RPL13 could be explained by a decrease in chromosomal copy number on chromosome 8. In conclusion, the array comparative genomic hybridization biologically validates our statistical approach and shows that gemcitabine is capable to select for chromosomally aberrant tumor cells, where changed gene expression levels lead to drug resistance.