The Role of chemokine receptor CXCR4 in breast cancer metastasis

Breast cancer is one of the leading causes of cancer related deaths worldwide. Breast cancer-related mortality is associated with the development of metastatic potential of primary tumor lesions. The chemokine receptor CXCR4 has been found to be a prognostic marker in various types of cancer, including breast cancer. Recent advances in the field of cancer biology has pointed to the critical role that CXCR4 receptor and its ligand CXCL12 play in the metastasis of various types of cancer, including breast cancer. Breast tumors preferentially metastasize to the lung, bones and lymph nodes, all of which represent organs that secrete high levels of CXCL12. CXCL12 acts as a chemoattractant that drives CXCR4-positive primary tumor cells towards secondary metastatic sites leading to the onset of metastatic lesions. Since its discovery in 2001, the CXCR4 field has progressed at a very fast rate and further studies have pointed to the role of CXCR4 in dissemination of tumor cells from primary sites, transendothelial migration of tumor cells as well as the trafficking and homing of cancer stem cells. This review summarizes the information that has been obtained over the years regarding the role of CXCL12-CXCR4 signaling in breast cancer, discusses its potential application to the development of new therapeutic tools for breast cancer control, and elucidates the potential therapeutic challenges which lie ahead and the future directions that this field can take for the improvement of prognosis in breast cancer patients.     

CXCR4和CXCR7在肿瘤中的研究进展

以往的研究认为趋化因子受体4(chemokine receptor 4,CXCR4)是趋化因子CXCL12的唯一受体,CXCL12/CXCR4生物轴在肿瘤发展过程中起重要作用,然而最近研究发现CXCL12尚存在CXCR7这一新的受体,并且CXCL12/CXCR7生物轴同样对肿瘤的发生发展起重要作用.本文就有关趋化因子受体CXCR4和CXCR7在肿瘤中的表达、促进肿瘤增殖和转移、促进血管新生以及肿瘤治疗等方面的研究作一综述.     

Tumor biology in estrogen receptor-positive,human epidermal growth factor receptor type 2-negative breast cancer: Mind the menopausal status

Breast cancer is not one disease, but can be categorized into four major molecular subtypes according to hormone receptor [estrogen receptor (ER) and progesterone receptor (PgR)] and human epidermal growth factor receptor type 2 (HER2) expression status. Ki67 labeling index and/or multigene assays are used to classify ER-positive, HER2-negative breast cancer into luminal A and luminal B (HER2-negative) subtypes. To date, most studies analyzing predictive or prognostic factors in ER-positive breast cancer have been performed in postmenopausal women, mainly using patients and samples in adjuvant aromatase inhibitor trials. In contrast, even the clinical roles of PgR and Ki67 have been little analyzed so far in premenopausal women. PgR is one of the estrogen-responsive genes, and it has been reported that plasma estradiol levels are related to expression levels of estrogen-responsive genes including PGR in ER-positive breast cancer. In this article, biological differences, especially differences in expression of PgR and Ki67 in ER-positive breast cancer between pre- and postmenopausal women are discussed. Clinical roles of PgR and Ki67 in ER-positive breast cancer differ between pre- and postmenopausal women. We suggest that the mechanisms of development and estrogen-dependent growth of ER-positive breast cancer might differ according to menopausal status.     

ETS2在乳腺癌细胞中调控CXCR4转录的机制研究

背景与目的：肿瘤转移是乳腺癌患者死亡的主要原因。趋化因子受体CXCR4与乳腺癌转移密切相关。本研究探讨转录因子ETS2(人红血细胞增多症病毒致癌基因同源体2)对人乳腺癌细胞中趋化因子受体CXCR4表达的影响,以及ETS2调控CXCR4转录的分子机制。方法：在MCF-7和MDA-MB-231人乳腺癌细胞株中,本研究通过瞬时转染技术,以及RNAi技术,检测过表达ETS2或抑制ETS2的表达。然后分别应用RT-PCR以及ELISA检测CXCR4 mRNA的表达和蛋白水平,荧光酶素报告基因实验检测启动子活性,ChIP实验检测结合到CXCR4启动子上的ETS2的量。并且对CXCR4启动子上的2个ETS结合位点进行突变,通过荧光报告基因实验,检测突变对CXCR4启动子活性的影响。结果：转染了ETS2过表达质粒的MDA-MB-231和MCF-7人乳腺癌细胞中,CXCR4的表达在mRNA和蛋白水平都升高;报告基因实验结果提示,ETS2通过激活CXCR4启动子的活性提高CXCR4的表达;通过ChIP实验发现,在转染了ETS2表达质粒的MDA-MB-231和MCF-7人乳腺癌细胞中,结合到CXCR4启动子上的ETS2的蛋白量増高,提示ETS2通过直接结合到CXCR4启动子上,从而提高CXCR4启动子的活性;利用RNA干扰技术,抑制ETS2的表达,可以显著减弱CXCR4启动子的活性,降低CXCR4的表达和结合到CXCR4启动子上的ETS2的量;荧光酶素报告基因的结果显示,任意一个位点的突变都降低了CXCR4启动子的活性,2个位点的同时突变使CXCR4启动子的活性进一步降低。结论：在人乳腺癌细胞株MCF-7和MDA-MB-231细胞中,ETS2通过直接结合到CXCR4启动子上的2个结合位点(-540到-535和-240到-235),活化CXCR4启动子活性,从而对CXCR4发挥转录调控的作用。     

趋化因子受体CXCR4在乳腺癌中表达的研究

目的探讨趋化受体CXCR4在乳腺癌中的表达及其与肿瘤转移的关系,以及脂多糖(LPS)对其表达的影响.方法采用流式细胞仪和RT-PCR法检测23例乳腺癌患者的癌组织、癌旁组织、正常组织以及MDA-MB-231细胞中CXCR4在蛋白质和mRNA水平的表达情况,以及LPS对MDA-MB-231细胞 CXCR4表达的影响;用Transwell板检测经LPS作用前后MDA-MB-231对趋化因子SDF-1趋化活性的影响.结果乳腺癌组织MDA-MB-231细胞的趋化因子受体CXCR4在蛋白质和mRNA水平的表达均显著高于癌旁组织和正常组织(P<0.05),并且CXCR4的表达与乳腺癌的转移密切相关;脂多糖(LPS)能下调CXCR4的表达,经LPS作用后乳腺癌细胞趋化活性降低.结论趋化因子受体在乳腺癌的转移中起重要作用,下调乳腺癌细胞CXCR4的表达水平,可减少或抑制其转移.     

局部进展期乳腺癌趋化因子受体CXCR4的表达与新辅助化疗疗效的相关性及预后研究

背景与目的:目前已经确立新辅助化疗在局部进展期乳腺癌(local advanced breast cancer,LABC)治疗中的地位,达到病理完全缓解者可提高生存率,但仍有大量患者复发、死亡,而无法从中受益。因此,我们迫切需要从分子水平找到可以预测新辅助化疗效果和预后的指标。目前已经证实趋化因子受体CXCR4与乳腺癌的侵袭和转移有关,然而关于CXCR4能否作为LABC患者新辅助化疗中的疗效指标和预后指标,目前却鲜有报道。本研究中,我们采用紫杉醇联合蒽环类的新辅助化疗方案治疗LABC,同时比较CXCR4低表达和高表达与疗效和远期生存的相关性。方法:对接受4个周期紫杉醇联合蒽环类的新辅助化疗方案进行治疗的86例ⅡB～ⅢB期(参照2002年AJCC乳腺癌TNM分期标准)LABC患者资料进行回顾性分析。用免疫组织化学法检测新辅助化疗前后乳腺癌组织CXCR4的表达,分析新辅助化疗对CXCR4低表达和CXCR4高表达患者的临床、病理疗效及其与远期生存的关系。结果:86例患者中58例(67.4%)为CXCR4高表达,28例(32.6%)为CXCR4低表达,新辅助化疗后,CXCR4高表达49例(57.0%),低表达37例(...     

The role of estrogen receptor alpha in mediating chemoresistance in breast cancer cells

Introduction

Previous studies suggested that estrogen receptor alpha (ERα) plays an important role in the chemoresistance of breast cancers. However, large random trials failed to demonstrate any benefit of the concurrent estrogen antagonist tamoxifen on the chemotherapy efficacy. Thus, in the present study, the importance of the role of ERα in the chemoresistance of breast cancer cells was investigated.

Methods

The ERα-transfected Bcap37 cells and natural ERα-positive T47D breast cancer cells were treated using chemotherapeutic agents with or without 17-beta estradiol (E2) pretreatment. Their viabilities were assessed using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assays. The dead cell rates were determined using propidium iodide dye exclusion tests, and the expression levels of Bcl-2 and Bax were detected through Western blot analysis. The effects of E2 on the growth of breast cancer cells were also determined via cell growth curve and cell cycle analysis.

Results

ERα activation by E2 increased the sensitivity of natural ERα-positive T47D breast cancer cells to chemotherapeutic agents. However, the increase in ERα expression in ERα-negative Bcap37 breast cancer cells also significantly increased their resistance. These phenomena cannot be explained by asserting that ERα mediated the chemoresistance of breast cancer cells by regulating the expression of Bcl-2 and Bax. Our findings show that ERα activation upregulated the expression of Bcl-2 in natural ERα-positive T47D breast cancer cells, whereas ERα activation by E2 downregulated and upregulated the Bcl-2 and Bax expression levels, respectively, in ERα-transfected Bcap37 cells. This phenomenon was due to the influence of ERα on the growth of breast cancer cells. Specifically, ERα activation enhanced the growth of natural ERα-positive breast cancer cells and thus increased their sensitivity to chemotherapeutic agents. However, ERα activation also inhibited the growth of ERα-transfected Bcap37 cells and increased the resistance of cancer cells to chemotherapeutic agents. Chemoresistance of ERα-transfected Bcap37 cells was only due to the specific growth inhibition by E2, which is not applicable to common ERα-positive breast cancer cells.

Conclusions

Although ERα was associated with chemoresistance of breast cancers, ERα itself did not mediate this resistance process.     

Simultaneous targeting of estrogen receptor and HER2 in breast cancer

Approximately 50% of HER2-positive breast cancers express estrogen receptor (ER) and these tumors are characterized by short-lived responses to hormonal agents. Preclinical models have shown that dual targeting of ER and HER2 could reverse and delay the development of drug resistance. Two studies (TAnDEM & EGF3008) have recently been published addressing the combined use of an aromatase inhibitor (AI) and an anti-HER2-targeted agent. Both studies showed that the combined approach is associated with improvement in response rate and progression-free survival compared with an AI alone with an acceptable toxicity profile. These results would indeed extend the treatment options for patients with ER/HER2-positive metastatic breast cancer. In this article, we discuss how the improved understanding of the complex cross-talk between ER and HER2 has resulted in better clinical outcomes. We analyze clinical evidence regarding the combined use of AIs and anti-HER2-targeted agents. We also touch on possible mechanisms of resistance and ways to improve research in this field.     

乳腺癌雌激素受体表达调控的研究进展

雌激素受体(ER)阴性和ER表达下调是内分泌治疗失败及影响预后的原因,许多因素影响雌激素受体的表达。对ER表达调节机制的研究可以为乳腺癌的内分泌治疗提供新的途径。     

Clinical impact of assay of estrogen receptor beta cx in breast cancer

Since 1996 when estrogen receptor beta(ER beta) was discovered, much effort has been devoted to the question of the value of ER beta as a prognostic and/or predictive factor in breast cancer and its potential as a novel target for pharmacological intervention. When estrogen receptors are applied on sucrose gradients and quantified by ligand binding, we found that in contrast to ER alpha, which has a narrow tissue distribution, ER beta is expressed in many tissues including both normal and malignant breast tissue. Receptor protein levels in tissues can also be measured from the intensities of bands after Western blotting and can be quantified when purified and quantified receptor is used as a standard. With this technique, we found that there were some tumors which had over 600 fmol/mg of ER beta protein but no detectable estradiol binding. In such tumors, RT-PCR analysis revealed that ER beta cx is the only ER beta isoform present. ER beta cx is a splice variant which utilizes an alternative exon 8. This change in the C-terminus results in very poor binding to estradiol (E2) and has a dominant negative effect on ER alpha function. Immunohistochemical analysis with an ER beta cx specific antibody in 115 ER alpha-positive breast cancers revealed that about half of the samples expressed ER beta cx protein. Initial analysis of samples from patients with preoperative tamoxifen treatment revealed that ER alpha-positive tumors expressing ER beta cx and lacking PR seemed to be resistant to the anti-estrogen. We conclude that, in order to better characterize breast cancers and design appropriate therapy for individual patients, assays for ER beta cx must be made available to clinicians.     

Elevated chemokine receptor CXCR4 expression in primary tumors following neoadjuvant chemotherapy predicts poor outcomes for patients with locally advanced breast cancer (LABC)

Purpose Patients with locally advanced breast cancer (LABC) have a poor outcome. A molecular predictor to identify at-risk patients is sorely needed. CXCR4 is a chemokine receptor that has been linked to breast cancer invasion and metastasis. We postulate that in patients with LABC, CXCR4 overexpression levels in cancer specimens following neoadjuvant chemotherapy predict cancer outcome. Experimental design 54 patients with LABC were prospectively accrued and analyzed. All had neoadjuvant chemotherapy and definitive surgical therapy. Study homogeneity was maintained by standardized treatment, surveillance, and compliance protocols. A 1 cm³ cancer from the surgical specimens of each patient was retrieved for analysis. CXCR4 levels were detected using Western blots, and results were quantified against 1 μg of protein from HeLa cells. CXCR4 expression was defined as low (<6.6-fold) or high (≥6.6-fold). Primary endpoints were cancer recurrence and death. Statistical analysis performed included independent samples t-test, chi-square test, Spearman Rank analysis, Kaplan-Meier survival analysis, log-rank test, and Cox proportional hazard model. Results With a median follow-up of 30 months, patients with high CXCR4 overexpression (≥6.6-fold) had a significantly higher incidence of recurrence (P = 0.0006) and cancer death (P = 0.0128) than those with low CXCR4 overexpression (<6.6-fold). The relative risks for recurrence and death in the high CXCR4 group were 27.3-fold (95% CI: 6.2–120.8; P = 0.001) and 4.8-fold (95% CI: 1.5–15.0; P = 0.0076) higher, respectively than those in the low CXCR4 group. Conclusion High CXCR4 overexpression in specimens from LABC patients receiving neoadjuvant chemotherapy was predictive of cancer outcome. Neal T. Holm was the recipient of the American Society of Clinical Oncology 2007 Merit Award     

Poly (ADP-ribose) polymerase inhibition enhances trastuzumab antitumour activity in HER2 overexpressing breast cancer

AimPoly (ADP-ribose) polymerase (PARP) inhibitors have shown promising results in Breast Cancer (BRCA) deficient breast cancer, but not in molecularly unselected patient populations. Two lines of research in this field are needed: the identification of novel subsets of patients that could potentially benefit from PARP inhibitors and the discovery of suitable targeted therapies for combination strategies.MethodsWe tested PARP inhibition, alone or combined with the anti-HER2 antibody trastuzumab on HER2+ breast cancer. We used two PARP inhibitors in clinical development, olaparib and rucaparib, as well as genetic downmodulation of PARP-1 for in vitro studies. DNA damage was studied by the formation of γH2AX foci and comet assay. Finally, the in vivo anti-tumour effect of olaparib and trastuzumab was examined in nude mice subcutaneously implanted with BT474 cells.ResultsIn a panel of four HER2 overexpressing breast cancer cell lines, both olaparib and rucaparib significantly decreased cell growth and enhanced anti-tumour effects of trastuzumab. Cells exposed to olaparib and trastuzumab had greater DNA damage than cells exposed to each agent alone. Mechanistic exploratory assays showed that trastuzumab downmodulated the homologous recombination protein proliferating cell nuclear antigen (PCNA). Combination treatment in the BT474 xenograft model resulted in enhanced growth inhibition, reduced tumour cell proliferation, and increased DNA damage and apoptosis.ConclusionTaken together, our results show that PARP inhibition has antitumour effects and increases trastuzumab activity in HER2 overexpressing breast cancer. These findings make this novel combination a promising strategy for clinical development.     

Interactions between the estrogen receptor,its cofactors and microRNAs in breast cancer

The activity of selective estrogen receptor modulators (SERMs) is not fully explained by an estrogen receptor (ER) switch model that simply turns estrogen activity on or off. A better understanding of the mechanisms involved in estrogen signaling and the development of drug resistance could help stratify patients into more coherent treatment groups and identify novel therapeutic candidates. This review describes how interactions between two novel factors known to influence estrogenic activity: nuclear receptor cofactors—protein partners which modulate estrogen action, and microRNAs—a class of recently discovered regulatory elements, may impact hormone-sensitive breast cancer. The role of nuclear receptor cofactors in estrogen signaling and the associations between ER cofactors and breast cancer are described. We outline the activity of microRNAs (miRNAs) and their associations with breast cancer and detail recent evidence of interactions between the ER and its cofactors and miRNA and provide an overview of the emerging field of miRNA-based therapeutics. We propose that previously unrecognised interactions between these two species of regulatory molecules may underlie at least some of the heterogeneity of breast cancer in terms of its clinical course and response to treatment. The exploitation of such associations will have important implications for drug development.     

乳腺癌中趋化因子受体CXCR4表达及临床病理意义

目的探讨趋化因子受体CXCR4在乳腺癌中的表达及临床意义,为临床治疗乳腺癌寻求新的治疗靶点提供依据。方法采用免疫组化SP染色法检测乳腺癌、乳腺增生组织及乳腺纤维腺瘤中CXCR4表达差异,以及CXCR4在乳腺癌中表达与患者肿瘤分级、淋巴结转移状态、Her2等相互关系。结果CXCR4在乳腺癌组织中高表达,与乳腺增生组织及乳腺纤维腺瘤中表达差异有显著性,而且与患者淋巴结转移状态、Her2、PCNA密切相关。结论CXCR4在乳腺中癌高表达,与患者淋巴结转移状态、Her2、PCNA密切相关,可以作为乳腺癌患者预后的一个指标,为寻找新的乳腺癌治疗靶点提供重要的临床依据。