DNA损伤修复变异指导铂类药物治疗三阴性乳腺癌的应用前景

三阴性乳腺癌(TNBC)极易复发和远处转移, 是预后最差的乳腺癌亚型, 其主要的治疗手段为化疗, 但目前仍缺乏有效的辅助化疗方案。化疗效果不理想成为阻碍TNBC疗效提高的瓶颈问题。铂类药物作用于细胞DNA, 通过损伤肿瘤细胞DNA, 达到杀灭肿瘤的作用, 对携带DNA损伤修复缺陷的肿瘤细胞有更强的杀伤作用, 成为提高TNBC疗效的重要切入点。寻找能够预测铂类药物在TNBC治疗疗效的生物标志物始终为热点问题之一。DNA损伤修复(DDR)通路包含大量相关基因, DDR通路功能缺失可能与铂类药物疗效相关, 其有望成为预测铂类药物治疗乳腺癌疗效的生物标志物。     

Pol(t)与肿瘤

DNA聚合酶iota(Pol)与DNA修复基因Rev1、DNA聚合酶kappa (Polκ)、DNA聚合酶eta(Polη)同为Y家族聚合酶,能通过跨损伤修复对损伤DNA进行修复.但是在所有的DNA聚合酶中,Pol(t)具有最低的保真性,在错误和正确模板的情况下都有很高的错配几率,且能够跨过一些DNA损伤将错配累积起来.最近研究表明Pol(t)在一些肿瘤组织中表达异常,包括人葡萄膜黑色素瘤、乳腺癌、膀胱癌、肺癌和食管癌.异常表达的Pol(t)与肿瘤发生发展关系密切,其修复DNA损伤的功能可能与肿瘤的放化疗抵抗相关.     

真核细胞DNA双链断裂修复通路的选择和调节

许多外源及内源性因素均可导致DNA损伤,从而对遗传信息的有效传递甚至生物体的生存造成极大的威胁。真核细胞依靠长期进化出的DNA损伤应激反应(DDR)系统来对抗DNA损伤。DNA双链断裂(DSB)是最为严重的损伤形式之一,DSB修复失败会导致细胞死亡、遗传疾病以及肿瘤发生等严重后果。真核细胞中主要存在2种DSB修复方式:同源重组(HR)和非同源末端连接(NHEJ)。本文介绍了HR和NHEJ通路的执行过程和参与成员,并对当前HR和NHEJ修复通路选择和调节机制的最新研究进展进行综述。     

5-氮杂-2’-脱氧胞苷诱导乳腺癌细胞自噬与DNA损伤相关联

目的:探讨5-氮杂-2’-脱氧胞苷对乳腺癌细胞自噬的影响及其可能的机制.方法:用依托泊苷、顺铂和5-氮杂-2’-脱氧胞苷处理乳腺癌细胞后,采用彗星实验测定细胞DNA损伤,蛋白质印迹法检测p53和p21蛋白表达;细胞自噬测定用3种方法:(1)蛋白质印迹法检测微管相关蛋白1轻链3-Ⅱ (microtubule-associated protein1 light chain 3-Ⅱ,LC3-Ⅱ)蛋白的表达;(2)用单丹磺酰戊二胺对乳腺癌细胞染色后,在荧光显微镜下计数自噬泡阳性细胞,并计算自噬泡阳性细胞百分比;(3)将pEGFP-LC3质粒转染至乳腺癌细胞后,在荧光显微镜下计数含绿色荧光蛋白的阳性细胞,并计算绿色荧光蛋白阳性细胞的百分比.结果:依托泊苷和顺铂均可诱导乳腺癌细胞DNA损伤和自噬,与对照组比较,药物处理组细胞的彗星长度增长(P＜0.01),p53、p21和LC3-Ⅱ蛋白表达上调.5-氮杂-2’-脱氧胞苷也可诱导乳腺癌细胞DNA损伤和自噬,与对照组比较,处理组细胞的彗星长度增长(P＜0.01),p53、p21和LC3- Ⅱ蛋白表达上调,自噬泡阳性细胞百分比和绿色荧光蛋白阳性细胞百分比上升,差异均有统计学意义(P＜0.05和P＜0.01).结论:5-氮杂-2’-脱氧胞苷可诱导乳腺癌细胞自噬,其机制可能与其所诱导的DNA损伤有关.     

BRCA1的DNA损伤修复与启动子甲基化的研究进展

目的:总结国内外对BRCA1(breast cancer susceptibility gene 1)的DNA损伤修复功能及其启动子甲基化研究的现状.方法:检索西文生物医学期刊文献数据库及维普医药信息资源系统,以BRCA1、基因、乳腺癌和甲基化等为关键词,检索2000-01～2007-08相关BRCA1的文献.资料选择:初选与BRCA1的结构特点、DNA损伤修复功能、BRCA1失活和启动子甲基化相关的文献.纳入标准:1)BRCA1的基因序列及其编码产物;2)BRCA1的结构特点与蛋白质组学研究;3)BRCAl的DNA损伤修复功能;4)BRCA1表达缺失的研究;5)基因启动子甲基化的研究.资料提炼:粗选125篇关于乳腺癌BRCA1方面的文章摘要,根据纳入标准,精选48篇文献,最后纳入分析21篇文献.结果:BRCA1是迄今为止发现与乳腺癌发生有关的最重要的抑癌基因,其基因结构特点已被清楚认识,但其蛋白质组学研究的文献还不多.多个研究表明,BRCA1是一种主要与DNA双链损伤修复相关的抑癌基因,甲基化往往会改变基因的表达模式,导致抑癌基因的转录失活或沉默.结论:BRCA1基因启动子的甲基化导致抑癌基因的表达缺失和表达产物失活,丧失了DNA损伤修复等一系列功能是导致乳腺癌形成的重要原因之一.但BRCA1基因启动子甲基化的具体状态及其与乳腺癌的临床病理特征的关系还需进一步研究.     

BRCA1基因相关的DNA修复通路异常与三阴乳腺癌化疗药物选择的关系

三阴乳腺痛以雌激素受体(estrogen receptor,ER)、孕激素受体(progestogen receptor,PR)以及Her-2阴性为特征,临床表现为组织分化差,术后易出现局部复发和远处转移,而且脏器比骨骼更容易发生转移.因对内分泌治疗和以Her-2为靶向分子的治疗无效,化疗成为治疗方案中的主体.与其他类型乳腺癌比较,三阴乳腺癌患者与乳腺基底细胞样癌和乳癌基因1(BRCA1)相关性乳腺癌在表型和分子生物学水平方面具有很多共性.不同个体DNA损伤修复能力的差异和乳腺癌的发病密切相关.BRCA1以及相关的DNA修复通路中的不同基因,如BRCA2、ATM、RAD51和CHEK2对维护基因组稳定性方面有重要作用.因此,三阴乳腺痛患者BRCA1相关的DNA修复通路异常而导致DNA修复能力异常,影响了其对化疗药物的敏感性,进而可能促进了高转移特性的形成.导致三阴乳腺癌重要脏器转移高发的原因,是肿瘤本身的转移相关基因异常的内因所致,还是对所接受的治疗耐药而使肿瘤细胞处于逃逸状态而引起,目前尚不明确.因此本文对BRCA1相关的DNA修复通路异常与三阴乳腺癌高转移之间的关系进行综述.     

c-erbB-2、PS2、PSA及DNA含量与乳腺癌神经内分泌分化的相关性研究

目的　探讨伴神经内分泌 (NE)细胞分化的乳腺癌的恶性程度及生物学行为。方法　用免疫组化法(L SAB)对 131例乳腺癌进行铬粒素 (chromogranin)、c- erb B- 2、PS2及前列腺特异抗原 (PSA)表达检测 ,以经典的Feulgen染色法及图像分析技术对 81例乳腺癌进行 DNA定量分析。结果　 NE细胞阳性乳腺癌 c- erb B- 2阳性表达率为 37.5 %及表达强度 ( ～ ) 33.3%均明显低于 NE细胞阴性肿瘤的 6 2 .6 %和 6 8.7% (P<0 .0 5 ,P<0 .0 5 ) ;NE细胞阳性乳腺癌 PS2、PSA表达率分别为 72 .2 %和 5 5 .0 % ,均显著高于 NE细胞阴性肿瘤的 45 .0 %与16 .4% (P<0 .0 5 ,P<0 .0 5 ) ;NE细胞 ( )组 DNA指数、DNA主干系峰值、>5 C异倍体细胞数以及异倍体率均显著高于 NE细胞 ( )乳腺癌组 (P<0 .0 5 ) ,NE细胞 ( )乳腺癌组积分吸光度、DNA指数、DNA主干系峰值、>5 C异倍体细胞数以及异倍体率均明显低于 NE细胞阴性组 (P<0 .0 5 ) ;在 ～ 级乳腺癌中 ,NE细胞阳性组的积分吸光度、DNA指数、DNA主干峰值、>5 C异倍体细胞数以及异倍体率均显著低于 NE细胞阴性组 (P<0 .0 1)。结论　伴神经内分泌分化的乳腺癌恶性程度较低 ,预后较好。     

聚腺苷酸二磷酸核糖转移酶抑制剂在恶性肿瘤治疗中的应用进展

聚腺苷酸二磷酸核糖转移酶(PARP)是一种广泛参与DNA损伤修复过程的酶.PARP抑制剂能通过抑制肿瘤细胞中PARP功能阻断细胞自身DNA损伤修复,促进肿瘤细胞的凋亡,以发挥抗肿瘤作用.PARP抑制剂单药利用合成致死作用,选择性地杀伤同源重组修复缺陷(尤其乳腺癌易感基因1/2突变)的肿瘤细胞.除此之外,与其他抗肿瘤治疗联合应用,在保证安全性的条件下,PARP抑制剂可以增强破坏肿瘤细胞DNA的抗癌药物(如烷化剂、拓扑异构酶抑制剂和铂类化疗药物)以及放疗的疗效.近年来更是与血管内皮生长因子(VEGF)抑制剂、程序性死亡受体1(PD-1)/程序性死亡受体配体1(PD-L1)抑制剂等一些新型靶向抗癌药进行联合治疗,扩大了临床适用范围.目前,PARP抑制剂奥拉帕利、鲁卡帕利、尼拉帕利和他拉唑帕利已经成功应用于卵巢癌、乳腺癌等一些肿瘤.本文将PARP抑制剂在恶性肿瘤中临床应用进展作一综述.     

PARP抑制剂治疗晚期乳腺癌的作用机制及相关研究进展

多聚二磷酸腺苷核糖聚合酶（poly ADP-ribose polymerase，PARP）抑制剂可使乳腺癌细胞的单链DNA损伤修复受阻，而BRCA突变可造成乳腺癌细胞的双链DNA损伤修复功能缺失，因此PARP抑制剂治疗乳腺癌易感基因（breast cancer susceptibility gene，BRCA）突变乳腺癌是通过同时阻断单链DNA和双链DNA损伤修复，导致细胞的DNA损伤修复失败，使癌细胞死亡。目前已研发出多种敏感性和特异性较高的PARP抑制剂，该类药物主要抑制PARP1和PARP2两种亚型。本文总结PARP抑制剂用于治疗BRCA突变乳腺癌的作用机制，并对多种PARP抑制剂单用或联合化疗药物治疗晚期乳腺癌的研究进展进行综述。      

DNA甲基化对乳腺癌雌激素受体的调控

DNA甲基化是哺乳动物细胞中遗传外修饰,与基因转录失活有关.乳腺癌中部分雌激素受体(ER)阴性,与ER基因启动子CpG岛高甲基化有关.DNA甲基化抑制剂能使ER恢复表达,可望用于治疗乳腺癌,尤其是ER阴性的乳腺癌.     

Targeting the DNA damage response for patients with lymphoma: Preclinical and clinical evidences

The DNA damage response (DDR) is a well-coordinated cellular network activated by DNA damage. The unravelling of the key players in DDR, their specific inactivation in different tumor types and the synthesis of specific chemical inhibitors of DDR represent a new hot topic in cancer therapy. In this article, we will review the importance of DDR in lymphoma development and how this can be exploited therapeutically. Specifically, we will focus on CHK1, WEE1, ATR, DNA-PK and PARP inhibitors, for which preclinical data as single agents or in combination has been accumulating, fostering their clinical development. The few available clinical data on these inhibitors will also be discussed.     

Anti‐tumor activity of the ATR inhibitor AZD6738 in HER2 positive breast cancer cells

Ataxia telangiectasia and Rad3‐related (ATR) proteins are sensors of DNA damage, which induces homologous recombination (HR)‐dependent repair. ATR is a master regulator of DNA damage repair (DDR), signaling to control DNA replication, DNA repair and apoptosis. Therefore, the ATR pathway might be an attractive target for developing new drugs. This study was designed to investigate the antitumor effects of the ATR inhibitor, AZD6738 and its underlying mechanism in human breast cancer cells. Growth inhibitory effects of AZD6738 against human breast cancer cell lines were studied using a 3‐(4,5‐dimethylthiazol‐2‐yl)?2,5‐diphenyltetrazolium bromide (methyl thiazolyl tetrazolium, MTT) assay. Cell cycle analysis, Western blotting, immunofluorescence and comet assays were also performed to elucidate underlying mechanisms of AZD6738 action. Anti‐proliferative and DDR inhibitory effects of AZD6738 were demonstrated in human breast cancer cell lines. Among 13 cell lines, the IC₅₀ values of nine cell lines were less than 1 μmol/L using MTT assay. Two cell lines, SK‐BR‐3 and BT‐474, were chosen for further evaluation focused on human epidermal growth factor receptor 2 (HER2)‐positive breast cancer cells. Sensitive SK‐BR‐3 but not the less sensitive BT‐474 breast cancer cells showed increased level of apoptosis and S phase arrest and reduced expression levels of phosphorylated check‐point kinase 1 (CHK1) and other repair markers. Decreased functional CHK1 expression induced DNA damage accumulation due to HR inactivation. AZD6738 showed synergistic activity with cisplatin. Understanding the antitumor activity and mechanisms of AZD6738 in HER2‐positive breast cancer cells creates the possibility for future clinical trials targeting DDR in HER2‐positive breast cancer treatment.     

Targeting the PI3K pathway and DNA damage response as a therapeutic strategy in ovarian cancer

Ovarian cancer is the most lethal gynecological malignancy worldwide although exponential progress has been made in its treatment over the last decade. New agents and novel combination treatments are on the horizon. Among many new drugs, a series of PI3K/AKT/mTOR pathway (referred to as the PI3K pathway) inhibitors are under development or already in clinical testing. The PI3K pathway is frequently upregulated in ovarian cancer and activated PI3K signaling contributes to increased cell survival and chemoresistance. However, no significant clinical success has been achieved with the PI3K pathway inhibitor(s) to date, reflecting the complex biology and also highlighting the need for combination treatment strategies. DNA damage repair pathways have been active therapeutic targets in ovarian cancer. Emerging data suggest the PI3K pathway is also involved in DNA replication and genome stability, making DNA damage response (DDR) inhibitors as an attractive combination treatment for PI3K pathway blockades. This review describes an expanded role for the PI3K pathway in the context of DDR and cell cycle regulation. We also present the novel treatment strategies combining PI3K pathway inhibitors with DDR blockades to improve the efficacy of these inhibitors for ovarian cancer.     

ATR-CHK1 pathway as a therapeutic target for acute and chronic leukemias

Progress in cancer therapy changed the outcome of many patients and moved therapy from chemotherapy agents to targeted drugs. Targeted drugs already changed the clinical practice in treatment of leukemias, such as imatinib (BCR/ABL inhibitor) in chronic myeloid leukemia (CML) and acute lymphoblastic leukemia (ALL), ibrutinib (Bruton's tyrosine kinase inhibitor) in chronic lymphocytic leukemia (CLL), venetoclax (BCL2 inhibitor) in CLL and acute myeloid leukemia (AML) or midostaurin (FLT3 inhibitor) in AML.In this review, we focused on DNA damage response (DDR) inhibition, specifically on inhibition of ATR-CHK1 pathway. Cancer cells harbor often defects in different DDR pathways, which render them vulnerable to DDR inhibition. Some DDR inhibitors showed interesting single-agent activity even in the absence of cytotoxic drug especially in cancers with underlying defects in DDR or DNA replication. Almost no mutations were found in ATR and CHEK1 genes in leukemia patients. Together with the fact that ATR-CHK1 pathway is essential for cell development and survival of leukemia cells, it represents a promising therapeutic target for treatment of leukemia. ATR-CHK1 inhibition showed excellent results in preclinical testing in acute and chronic leukemias. However, results in clinical trials are so far insufficient. Therefore, the ongoing and future clinical trials will decide on the success of ATR/CHK1 inhibitors in clinical practice of leukemia treatment.     

Aberrant expression of DNA damage response proteins is associated with breast cancer subtype and clinical features

Landmark studies of the status of DNA damage checkpoints and associated repair functions in preneoplastic and neoplastic cells has focused attention on importance of these pathways in cancer development, and inhibitors of repair pathways are in clinical trials for treatment of triple negative breast cancer. Cancer heterogeneity suggests that specific cancer subtypes will have distinct mechanisms of DNA damage survival, dependent on biological context. In this study, status of DNA damage response (DDR)-associated proteins was examined in breast cancer subtypes in association with clinical features; 479 breast cancers were examined for expression of DDR proteins γH2AX, BRCA1, pChk2, and p53, DNA damage-sensitive tumor suppressors Fhit and Wwox, and Wwox-interacting proteins Ap2α, Ap2γ, ErbB4, and correlations among proteins, tumor subtypes, and clinical features were assessed. In a multivariable model, triple negative cancers showed significantly reduced Fhit and Wwox, increased p53 and Ap2γ protein expression, and were significantly more likely than other subtype tumors to exhibit aberrant expression of two or more DDR-associated proteins. Disease-free survival was associated with subtype, Fhit and membrane ErbB4 expression level and aberrant expression of multiple DDR-associated proteins. These results suggest that definition of specific DNA repair and checkpoint defects in subgroups of triple negative cancer might identify new treatment targets. Expression of Wwox and its interactor, ErbB4, was highly significantly reduced in metastatic tissues vs. matched primary tissues, suggesting that Wwox signal pathway loss contributes to lymph node metastasis, perhaps by allowing survival of tumor cells that have detached from basement membranes, as proposed for the role of Wwox in ovarian cancer spread.     

BRCA1/2突变和同源重组修复缺陷(HRD)检测在乳腺癌中的临床研究进展

乳腺癌已成为发病率最高的癌症。DNA修复缺陷是乳腺癌最重要的特征之一。先前的研究表明,乳腺癌易感基因1/2(breast cancer susceptibility gene 1/2,BRCA1/2)突变是预测乳腺癌同源重组修复缺陷(homologous recombination deficiency, HRD)最主要的生物标志物,能识别铂类药物和多腺苷二磷酸核糖聚合酶(poly ADP ribose polymerase, PARP)抑制剂治疗的获益人群。美国食品药品监督管理局(FDA)已批准Olaparib和Talazoparib两种PARP抑制剂,用于BRCA1/2突变的早期和晚期乳腺癌的辅助治疗。但中国尚未获批。现有研究表明,一部分非BRCA1/2突变的乳腺癌患者也具有HRD特征,可以从铂类药物或PARP抑制剂中获益。本综述总结了涉及到BRCA1/2突变、同源重组修复(homologous recombination repair, HRR)基因突变和HRD状态检测的临床研究。阐明了各种检测方法在识别乳腺癌患者HRD状态和预测疗效方面的价值,并提出应尽快开发用于中国乳腺癌HR...     

Synthetic lethality strategies: Beyond BRCA1/2 mutations in pancreatic cancer

Cancer cells are often characterized by abnormalities in DNA damage response including defects in cell cycle checkpoints and/or DNA repair. Synthetic lethality between DNA damage repair (DDR) pathways has provided a paradigm for cancer therapy by targeting DDR. The successful example is that cancer cells with BRCA1/2 mutations are sensitized to poly(adenosine diphosphate [ADP]‐ribose)polymerase (PARP) inhibitors. Beyond the narrow scope of defects in the BRCA pathway, “BRCAness” provides more opportunities for synthetic lethality strategy. In human pancreatic cancer, frequent mutations were found in cell cycle and DDR genes, including P16, P73, APC, MLH1, ATM, PALB2, and MGMT. Combined DDR inhibitors and chemotherapeutic agents are under preclinical or clinical trials. Promoter region methylation was found frequently in cell cycle and DDR genes. Epigenetics joins the Knudson's “hit” theory and “BRCAness.” Aberrant epigenetic changes in cell cycle or DDR regulators may serve as a new avenue for synthetic lethality strategy in pancreatic cancer.     

Decreased expression of the translation factor eIF3e induces senescence in breast cancer cells via suppression of PARP1 and activation of mTORC1

Altered expression of the translation factor eIF3e is associated with breast cancer occurrence. We have previously shown that eIF3e deficiency leads to an impaired DNA damage response with a marked decrease in DNA repair by homologous recombination. Here, we explored the possibility to exploit this DNA repair defect in targeted cancer therapy using PARP inhibitors. Surprisingly, eIF3e-deficient breast cancer cells are resistant to these drugs, in contrast to BRCA1-deficient cells. Studying this, we found that eIF3e-depleted cells synthesize lowered amounts of PARP1 protein, due to a weakened translation of the corresponding mRNA, associated with a strong decrease in cellular poly(ADP-ribosyl)ation. Additionally, we discovered that the mTORC1 signaling pathway is aberrantly activated in response to eIF3e suppression. Together, these PARP1 and mTORC1 dysfunctions upon eIF3e depletion are causally linked to induction of cellular senescence associated with a pro-inflammatory secretory phenotype. This study provides mechanistic insights into how eIF3e protects against breast cancer, with potential novel cancer therapeutic opportunities. While PARP inhibitors appear as inappropriate drugs for eIF3e-deficient breast tumors, our findings suggest that such cancers may benefit from senolytic drugs or mTORC1 inhibitors.     

Recent advances in targeting DNA repair pathways for the treatment of ovarian cancer and their clinical relevance

Poly (ADP-ribose) polymerase (PARP) inhibitors have attracted much attention as one of the major molecular-targeted therapeutics for inhibiting DNA damage response. The PARP inhibitor, olaparib, has been clinically applied for treating certain recurrent ovarian cancer patients with BRCA1/2 mutations in Europe and the United States. It was also designated on 24 March 2017 as an orphan drug in Japan for similar clinical indications. In this review, we discuss (i) the prevalence of BRCA1/2 mutations in ovarian cancer, (ii) clinical trials of PARP inhibitors in ovarian cancer, (iii) genetic counseling for hereditary breast and ovarian cancer patients, and (iv) non-BRCA genes that may be associated with homologous recombination deficiency.     

Exploiting DNA repair defects in breast cancer: from chemotherapy to immunotherapy

Introduction: Impaired DNA damage response (DDR) and subsequent genomic instability are associated with the carcinogenic process itself, but it also results in sensitivity of tumor cells to certain drugs and can be exploited to treat cancer by inducing deadly mutations or mitotic catastrophe. Exploiting DDR defects in breast cancer cells has been one of the main strategies in both conventional chemotherapy, targeted therapies, or immunotherapies.

Areas covered: In this review, the authors first discuss DDR mechanisms in healthy cells and DDR defects in breast cancer, then focus on current therapies and developments in the treatment of DDR-deficient breast cancer.

Expert opinion: Among conventional chemotherapeutics, platinum-based regimens, in particular, seem to be effective in DDR-deficient patients. PARP inhibitors represent one of the successful models of translational research in this area and clinical data showed high efficacy and reasonable toxicity with these agents in patients with breast cancer and BRCA mutation. Recent studies have underlined that some subtypes of breast cancer are highly immunogenic. Promising activity has been shown with immunotherapeutic agents, particularly in DDR-deficient breast cancers. Chemotherapeutics, DNA-repair pathway inhibitors, and immunotherapies might result in further improved outcomes in certain subsets of patients with breast cancer and DDR.