Triple-negative breast cancer: making the most of a misnomer

Triple-negative breast cancer (TNBC) is defined by its lack of (or minimal) estrogen receptor and progesterone receptor expression, together with the absence of human epidermal growth factor receptor 2 overexpression or gene amplification. It can be a particularly aggressive form of breast cancer, often characterized by early systemic relapse. This subtype, absent from traditional pathology classifications, has quietly crept into the oncologist's lexicon over the last decade and aroused considerable research interest. Based on tumor pathology, immunohistochemistry and gene profiling studies, TNBC is likely to represent a heterogeneous mix of breast cancer subtypes. This observation will have important implications for the selection of optimal therapies, which are yet to be defined. This article reviews recent insights in the classification and ontogeny of TNBC, current approaches to its management and promising therapeutic targets that are forming the basis for innovative early and late phase clinical trials.     

Evaluating the link between stem cells and breast cancer

Mammary stem cells have recently been identified and purified on the basis of surface antigens and transplantation assays. In addition, recent reports have identified a small sub-population of highly tumorigenic cells within primary and metastatic breast tumors and in a number of breast cancer cell lines. This suggests that, similarly to its normal physiological counterpart, a cancer stem cell may be at the origin of breast cancer. These observations have dramatic biological and clinical implications, as they dictate a revision of our understanding of breast cancer and of our therapeutic strategies. The aim of this article is to review recent data regarding normal mammary epithelial stem cells and evidence in support of the cancer stem cell hypothesis in the breast, and to provide further insight into how taking this subpopulation of cells into account may affect the way we treat epithelial cancers in the future.     

Overexpression of Id1 in transgenic mice promotes mammary basal stem cell activity and breast tumorigenesis

Inhibitor of differentiation/DNA binding (Id)1 is a crucial regulator of mammary development and breast cancer progression. However, its effect on stemness and tumorigenesis in mammary epithelial cells remains undefined. Herein, we demonstrate that Id1 induces mammary tumorigenesis by increasing normal and malignant mammary stem cell (MaSC) activities in transgenic mice. MaSC-enriched basal cell expansion and increased self-renewal and in vivo regenerative capacity of MaSCs are observed in the mammary glands of MMTV-Id1 transgenic mice. Furthermore, MMTV-Id1 mice develop ductal hyperplasia and mammary tumors with highly expressed basal markers. Id1 also increases breast cancer stem cell (CSC) population and activity in human breast cancer lines. Moreover, the effects of Id1 on normal and malignant stem cell activities are mediated by the Wnt/c-Myc pathway. Collectively, these findings provide in vivo genetic evidence of Id1 functions as an oncogene in breast cancer and indicate that Id1 regulates mammary basal stem cells by activating the Wnt/c-Myc pathway, thereby contributing to breast tumor development.     

Loss of p16 expression is associated with the stem cell characteristics of surface markers and therapeutic resistance in estrogen receptor-negative breast cancer

Triple-negative breast cancer [TNBC, which is negative for the estrogen receptor (ER), progesterone receptor, and human epidermal growth factor receptor 2] is a high-risk form of the disease without a specific therapy. DNA microarray and immunohistochemical analyses have shown that most TNBCs fall within the basal-like histological subset of breast cancers, which frequently exhibit inactivation of the retinoblastoma tumor suppressor (Rb) and upregulation of the cyclin-dependent kinase inhibitor p16(INK4a) (p16). However, downregulation of p16 expression has been observed in some basal-like breast cancer cell lines, suggesting that such cells can be divided into two groups according to Rb and p16 status. We now show that cells that are CD44(+) and CD24(-) , a phenotype associated with stem-like breast cancer cells, are more abundant in ER(-) /p16(-) breast cancer cell lines than in ER(-) /p16(+) lines. It was also found that p16 expression was downregulated in mammospheres from an ER-negative breast cancer cell line. Depletion of p16 by RNA interference in ER-negative breast cancer cells increased the percentage of CD44(+) /CD24(-) cells and increased the expression of mRNA of the ES-like genes Nanog, Oct4, and Sox2 through an Rb-independent pathway. Furthermore, such depletion of p16 reduced chemosensitivity. The loss of p16 expression may thus reduce the response of ER-negative breast cancer cells to chemotherapy by conferring cancer stem cell-like properties. Consistent with this conclusion, immunohistochemical analysis of the clinical samples suggests that low p16 expression in TNBC is associated with resistance to preoperative chemotherapy.     

小白菊内酯体内杀伤小鼠乳腺癌肿瘤干细胞

目的： 探讨小白菊内酯（parthenolide,PTL）对小鼠乳腺癌肿瘤干细胞（cancer stem cell,CSC）的杀伤作用,为临床应用PTL治疗乳腺癌提供实验依据。 方法： 采用5-氟尿嘧啶（5-fluorouracil, 5-FU）化疗法制备富含CSC的小鼠4T1细胞乳腺癌模型,随机分为对照组、5-FU组、PTL组。4周后脱颈处死小鼠,检测各组小鼠肿瘤的体积和重量,流式细胞术检测小鼠肿瘤组织中CD44+CD24-/low细胞比例,Hoechst33342染色法检测侧群（side population,SP）细胞的比例,免疫组化法检测CD55和乙醛脱氢酶1（aldehyde dehydrogenase1,ALDH1）蛋白的表达,倒置显微镜观察乳腺癌细胞微球体的形成。 结果： 成功制备富含CSC的小鼠乳腺癌细胞移植瘤模型,PTL可下调小鼠肿瘤组织中CD44+CD24-/low细胞的比例\[（42.5±3.7）% vs （68.7±32）%,P<0.05\],有效降低荷瘤小鼠肿瘤组织中SP细胞的比例\[（39.2±1.8）% vs （61.3±2.6）%,P<0.05\],下调小鼠移植瘤组织中CD55和ALDH1蛋白的表达\[（18.9±1.5）% vs （30.1±1.3）%,（8.1±2.3）% vs （18.0±1.4）%;均P<0.05\],抑制小鼠肿瘤细胞在无血清培养条件下形成微球体,并可抑制小鼠移植瘤的体积和重量\[（0.625±0.159）cm3 vs （1.715±0184）cm3,（1.467±0.373）g vs （3.367±0.398）g;均P<0.05\]。 结论： PTL在荷瘤小鼠体内可以明显降低肿瘤组织CSC含量,提示PTL可用来靶向杀伤乳腺癌CSC。     

乳腺癌干细胞的分离方法探讨

乳腺癌干细胞是首次被分离出的实体肿瘤干细胞,由于缺乏特异的细胞表面标志,如何获得纯化的乳腺癌干细胞已经成为乳腺癌研究的热点。目前存在的几种常用的乳腺癌干细胞的分离方法都各有利弊,现就乳腺癌干细胞的分离方法作一综述。     

5-FU对小鼠乳腺癌4T1细胞株中肿瘤干细胞样细胞的富集作用

目的:探讨以氟尿嘧啶(5-fluorouracil,5-FU)处理并通过荷瘤小鼠模型体内传代的方法富集乳腺癌干细胞样细胞的可行性,为靶向肿瘤干细胞治疗奠定基础.方法:以乳腺癌细胞株4T1皮下接种小鼠制备荷瘤模型,以一定剂量5-FU腹腔注射4周;处死小鼠后取肿瘤组织制成细胞悬液,并接种小鼠制备下一代小鼠荷瘤模型,5-FU处理及再次传代方法同上,共传4代.对照组小鼠给予生理盐水注射,其余处理同模型组.流式细胞术检测各代肿瘤组织中CD44+ CD24-/low细胞比例,Hoechast 33342染色法检测侧群(side population,SP)细胞的比例,免疫组化法检测CD55和ALDH1蛋白的表达,倒置显微镜观察乳腺癌细胞微球体的形成,小鼠致瘤实验检测不同肿瘤细胞的致瘤能力.结果:各代对照组小鼠模型肿瘤组织中CD44+CD24-/low细胞比例为(11.5±0.9)％,SP细胞比例为(9.7±1.3)％,ALDH1表达阴性,CD55强阳性表达细胞数为(0.6±0.3)％,乳腺癌细胞微球体比例为(0.5±0.2)％;5-FU处理组4代小鼠模型肿瘤组织中CD44+ CD24-/low细胞比例分别为(49.8±1.2)％、(56.8％±1.7)％、(66.4±1.5)％、(69.0±1.6)％,SP细胞比例分别为(25.0±1.2)％、(42.6±2.8)％、(58.4±2.1)％、(61.3±2.6)％,ALDH1阳性表达细胞比例为(3.8±0.7)％、(14.1±2.4)％、(25.2±3.1)％、(27.5±2.7)％,CD55强阳性细胞比例为(7.8±1.6)％、(10.1±2.0)％、(15.6±1.4)％、(17.3±1.9)％,乳腺癌细胞微球体形成比例为(5.9±0.4)％;两组各相应指标之间差异均具有统计学意义(P＜0.05或P＜0.01).5-FU作用后富集了肿瘤干细胞的第3代肿瘤细胞的致瘤作用显著强于对照组细胞(P＜0.05).结论:5-FU作用并通过荷瘤小鼠体内传代能够富集小鼠乳腺癌4T1细胞株中的肿瘤干细胞样细胞.     

蟾蜍灵对乳腺癌干细胞增殖和凋亡的影响

目的:探讨蟾蜍灵对乳腺癌干细胞的增殖和侵袭能力的影响。方法:将人乳腺癌MDA-MB-231细胞系进行培养,采用流式细胞分选技术从中分离出乳腺癌干细胞。CCK-8法检测不同浓度的蟾蜍灵对乳腺癌干细胞增殖的影响。流式细胞术Annexin Ⅴ-FITC/PI双染检测不同浓度的蟾蜍灵对乳腺癌干细胞凋亡的影响。结果:成功从MDA-MB-231细胞系中分选出乳腺癌干细胞。CCK-8结果显示,蟾蜍灵呈时间、浓度依赖性抑制乳腺癌干细胞增殖。流式细胞术结果显示蟾蜍灵随时间和浓度增加诱导乳腺癌干细胞凋亡率增加。 结论:蟾蜍灵能够抑制乳腺癌干细胞的增殖,并诱导其凋亡。     

三阴性乳腺癌的系统治疗策略

三阴性乳腺癌被定义为雌激素受体（ER）、孕激素受体（PR）和人表皮生长因子受体2（EGFR2）均阴性的乳腺癌,它具有独特的生物学特性及临床特征。大多数三阴性乳腺癌有基底细胞样表型的特点以及相同的临床病理特征,并且与遗传性基因BRCA1相关。三阴性乳腺癌患者不同的亚群对于特定的靶向治疗有着不同的疗效。我们评估了三阴性乳腺癌化疗联合靶向治疗的方案,系统评价了PubMed数据库上对接受了化疗和靶向治疗的乳腺癌女性患者的随机临床试验报告。三阴性乳腺癌是一个对化疗敏感的实体肿瘤,单纯结合靶向药物并不能使疗效显著的提高,合理地选择病人,理性地结合靶向药物,才能使疗效更好。     

维生素D对乳腺癌细胞及乳腺癌干细胞凋亡的影响

目的:探究维生素D对人乳腺癌细胞及乳腺癌干细胞凋亡的影响。方法:MTT法检测维生素D对乳腺癌SUM159细胞活力的影响;Hoechst33258染色检测维生素D对乳腺癌SUM159细胞凋亡的影响;实时定量PCR法检测维生素D对乳腺癌SUM159细胞凋亡相关分子Bax和Bcl-2 mRNA表达水平的影响;无血清悬浮培养法（serum-free medium,SFM）富集乳腺癌干细胞,显微镜下观察维生素D对乳腺癌干细胞球大小和数量的影响;实时定量PCR法检测维生素D对乳腺癌干细胞凋亡相关分子Bax、Bcl-2 mRNA表达水平的影响。结果:MTT法检测结果显示,维生素D可显著抑制乳腺癌细胞活力,且随着维生素D浓度升高,乳腺癌SUM159细胞活力的下降具有一定的剂量依赖效应,单因素方差分析显示,差异具有统计学意义(P＜0.01);Hoechst33258染色结果显示,维生素D可诱导乳腺癌SUM159细胞发生细胞凋亡形态改变;进一步PCR法检测结果显示,维生素D可显著上调乳腺癌SUM159细胞促凋亡蛋白Bax mRNA的表达,下调抗凋亡蛋白Bcl-2 mRNA的表达,单因素方差分析显示,差异具有统计学意义(P＜0.01)。SFM培养可有效富集乳腺癌干细胞,维生素D干预可明显抑制SFM富集的乳腺癌干细胞球的大小和数量,且与对照组相比,维生素D可显著上调乳腺癌干细胞球Bax mRNA的表达水平,下调Bcl-2 mRNA的表达水平,单因素方差分析显示,差异具有统计学意义(P＜0.01)。结论:维生素D可抑制乳腺癌细胞及乳腺癌干细胞活力,诱导乳腺癌细胞凋亡。     

乳腺癌研究及治疗新靶点—乳腺癌干细胞的研究进展

随着人们对乳腺癌发生、发展机制的深入研究,乳腺癌干细胞日益受到研究者们的重视,研究表明,乳腺癌干细胞是一群未分化、具有自我更新及多系分化潜能的细胞。这些细胞具有化疗、放疗及缺氧抵抗性,同时具有高致瘤性、高侵袭转移性和在乳腺癌的发生﹑发展乃至转移﹑复发中起着极其重要作用。深入研究乳腺癌干细胞相关信号转导通路和微环境的调控,为临床靶向治疗乳腺癌具有重要的指导意义。因此,本文对乳腺癌干细胞在乳腺癌研究及治疗中的最新进展作一综述。     

MicroRNA与乳腺癌干细胞

乳腺癌干细胞是导致乳腺癌复发、转移和耐药的根源之一。microRNA(miRNAs)是一类小分子非编码RNA,可与靶mRNA的3’UTR区域结合而导致该mRNA分子的翻译受到抑制,参与多种生物功能的调节。最近研究发现,miRNAs参与乳腺癌干细胞的分化、自我更新等生物学特性的调控。MiRNAs可以作为乳腺癌干细胞研究的一个新的切入点。本文就近年来该方面的研究进展做简要综述。     

Mesenchymal stem cell secretion of chemokines during differentiation into osteoblasts,and their potential role in mediating interactions with breast cancer cells

Over 70% of patients with advanced breast cancer will develop bone metastases for which there is no cure. Mesenchymal Stem Cells (MSCs) and their derivative osteoblasts are subpopulations of cells within the bone marrow environment, postulated as potential interacting targets for disseminating cancer cells because of their ability to secrete a range of chemokines. This study aimed to investigate chemokine secretion throughout MSC differentiation into osteoblasts and their effect on the breast cancer cells. Primary MSCs and osteoblast progenitors were cultured in appropriate conditions to induce differentiation into mature osteoblasts. Chemokines secreted throughout differentiation were detected using ChemiArray and ELISA. Migration of breast cancer cells in response to the bone‐derived cells was quantified using Transwell inserts. Breast cancer cells were cocultured with MSCs, retrieved using magnetic beads, and changes in CCL2 expression were analyzed. MSCs secreted a range of factors including IL‐6, TIMP‐1 and CCL2, the range and level of which changed throughout differentiation. CCL2 secretion by MSCs increased significantly above control cells as they differentiated into mature osteoblasts (p < 0.05). The bone‐derived cells stimulated migration of breast cancer cells, and this was inhibited (21–50%) in the presence of a CCL2 antibody. CCL2 gene expression in breast cancer cells was upregulated following direct coculture with MSCs. The varying levels of chemokines secreted throughout MSC differentiation may play an important role in supporting tumor cell homing and progression. These results further highlight the distinct effect MSCs have on breast cancer cells and their potential importance in supporting development of metastases. © 2008 Wiley‐Liss, Inc.     

Lack of correlation of stem cell markers in breast cancer stem cells

Background:

Various markers are used to identify the unique sub-population of breast cancer cells with stem cell properties. Whether these markers are expressed in all breast cancers, identify the same population of cells, or equate to therapeutic response is controversial.

Methods:

We investigated the expression of multiple cancer stem cell markers in human breast cancer samples and cell lines in vitro and in vivo, comparing across and within samples and relating expression with growth and therapeutic response to doxorubicin, docetaxol and radiotherapy.

Results:

CD24, CD44, ALDH and SOX2 expression, the ability to form mammospheres and side-population cells are variably present in human cancers and cell lines. Each marker identifies a unique rather than common population of cancer cells. In vivo, cells expressing these markers are not specifically localized to the presumptive stem cell niche at the tumour/stroma interface. Repeated therapy does not consistently enrich cells expressing these markers, although ER-negative cells accumulate.

Conclusions:

Commonly employed methods identify different cancer cell sub-populations with no consistent therapeutic implications, rather than a single population of cells. The relationships of breast cancer stem cells to clinical parameters will require identification of specific markers or panels for the individual cancer.     

Regulation of nonsmall‐cell lung cancer stem cell like cells by neurotransmitters and opioid peptides

Nonsmall‐cell lung cancer (NSCLC) is the leading type of lung cancer and has a poor prognosis. We have shown that chronic stress promoted NSCLC xenografts in mice via stress neurotransmitter‐activated cAMP signaling downstream of beta‐adrenergic receptors and incidental beta‐blocker therapy was reported to improve clinical outcomes in NSCLC patients. These findings suggest that psychological stress promotes NSCLC whereas pharmacologically or psychologically induced decreases in cAMP may inhibit NSCLC. Cancer stem cells are thought to drive the development, progression and resistance to therapy of NSCLC. However, their potential regulation by stress neurotransmitters has not been investigated. In the current study, epinephrine increased the number of cancer stem cell like cells (CSCs) from three NSCLC cell lines in spheroid formation assays while enhancing intracellular cAMP and the stem cell markers sonic hedgehog (SHH), aldehyde dehydrogenase‐1 (ALDH‐1) and Gli1, effects reversed by GABA or dynorphin B via Gα_i‐mediated inhibition of cAMP formation. The growth of NSCLC xenografts in a mouse model of stress reduction was significantly reduced as compared with mice maintained under standard conditions. Stress reduction reduced serum levels of corticosterone, norepinephrine and epinephrine while the inhibitory neurotransmitter γ‐aminobutyric acid (GABA) and opioid peptides increased. Stress reduction significantly reduced cAMP, VEGF, p‐ERK, p‐AKT, p‐CREB, p‐SRc, SHH, ALDH‐1 and Gli1 in xenograft tissues whereas cleaved caspase‐3 and p53 were induced. We conclude that stress neurotransmitters activate CSCs in NSCLC via multiple cAMP‐mediated pathways and that pharmacologically or psychologically induced decreases in cAMP signaling may improve clinical outcomes in NSCLC patients.     

人卵巢癌细胞系干/祖细胞分离及其鉴定

目的:自人卵巢癌细胞系SK-OV-3中分离干/祖细胞并进行鉴定。方法:采用无血清球形体形成法从SKOV-3中分离培养卵巢癌干/祖细胞;采用实时定量PCR和蛋折质印迹法测定球形体细胞干/祖细胞相关标志ABCG2、Oct-4、Nanog基因和蛋白的表达;流式细胞仪检测其耐药性;双层软琼脂检测其克隆形成能力;NOD/SCID小鼠检测其体内致瘤性。结果:球形体细胞表达干/祖细胞相关标志Oct-4、ABCG2、Nanog;对顺铂高耐药;在双层软琼脂上克隆形成率达(13.67±1.48)%;1 000个球形体形成细胞就能在NOD/SCID鼠中成瘤。结论:采用无血清培养基中球形体形成法从SKOV-3细胞系中可以分离出具有干/祖特性的卵巢癌细胞,可为今后研究卵巢癌的发生、发展、复发及其化疗药物筛选提供简便实用的体外模型。     

Alpha-6 integrin is necessary for the tumourigenicity of a stem cell-like subpopulation within the MCF7 breast cancer cell line

The identification of mammary epithelial stem cells raises the hypothesis that these cells may be crucial in the pathogenesis of breast cancer. To further support this, a highly tumourigenic sub-population of cancer cells has recently been identified in primary and metastatic breast cancer samples. In this study, a sub-population of cells displaying features normally attributed to stem cells was identified within the breast cancer cell line MCF-7. This sub-population is capable of growth in anchorage-independent conditions as spherical organoids, displays resistance to proapoptotic agents and significantly greater tumourigenicity than its parental line, with as few as 1,000 cells able to form tumours in immunodeficient mice. Cells within this sub-population can be enriched by serial passages in anchorage-independence, and are characterized by over-expression of the adhesion molecule alpha6-integrin. Alpha-6 integrin proves to be required for the growth and survival of these cells, as the knockdown of ITGA6 causes mammosphere-derived cells to lose their ability to grow as mammospheres and abrogates their tumourigenicity in mice. These findings support the existence of a highly tumourigenic sub-population in breast cancer cells. Furthermore, it shows alpha6-integrin as a potential therapeutic target aimed at tumour-generating subsets of breast cancer cells.     

MicroRNAs在乳腺癌干细胞中的作用研究进展

乳腺癌干细胞（breast cancer stem cells,BCSCs）是导致乳腺癌发生、转移、耐药、复发等的重要原因。MicroRNAs（miRNAs）是近年来发现的一种非编码小分子RNA,可通过与靶标基因的3 '-非翻译区（3'-UTR）的完全或不完全配对,抑制靶标基因的翻译或降解靶标基因,从而发挥多种生物学功能。miRNAs在BCSCs中的异常表达可调控BCSCs的自我更新、抗凋亡、上皮间质转化（epithelial-mesenchymal transition,EMT）等生物学行为,从而促进乳腺癌的复发、转移。以miRNAs为研究靶点,为乳腺癌的诊断、预后及治疗提供了全新的思路。本文就近年来该方面的研究进展简要综述。