DNA损伤修复与大肠癌关系的研究进展

大肠癌是人类恶性肿瘤之一,具有比较明确的遗传背景.近年来的研究表明,患者DNA的损伤修复与肿瘤的关系密切,本文综述DNA的错配修复、碱基切除修复、核苷酸切除修复等3种损伤修复机制与大肠癌相互关系的研究进展.     

DNA修复与肿瘤

随着分子生物学的迅速发展,人们对肿瘤的认识不断加深,对于增加肿瘤易感性的基因以及DNA修复与肿瘤的关系的研究亦日益深入。近来的研究已将周期素作为正性调控细胞生长的原癌基因,而将周期素依赖的激酶抑制物作为负性调控细胞生长的抑癌基因,从而将细胞转化的分子机制、肿瘤发生与细胞周期的调控联系起来,而DNA修复基因正是能够限制上述生长控制基因的突变而间接控制细胞增生的基因。本文仅就此方面的研究进展作以简要综述。     

川芎嗪通过RAD52调控乳腺癌细胞DNA损伤修复

目的:探究TMP对乳腺癌BT474细胞增殖、细胞周期及其调控蛋白表达与DNA双链断裂修复通路的相关性。方法:CCK8法测定TMP对乳腺癌BT474细胞的增殖抑制情况；流式细胞术测定TMP对细胞周期的影响；单细胞凝胶电泳测定分析TMP对损伤后细胞DSBs累积情况的影响；Isce-I内切酶系统检测TMP对修复通路活性的影响；Western blotting检测DSBs修复通路相关染色体结合蛋白表达水平变化。结果:TMP通过使细胞阻滞在G₁期呈浓度依赖性抑制BT474细胞增殖，显著减少体内由Zeocin导致的细胞拖尾DNA含量(P<0.05);TMP显著增加BT474细胞对RAD52、ERCC1、XRCC4以及DNA LigⅣ蛋白募集，减少对KU80蛋白募集，促进了SSA以及NHEJ通路修复活性(P<0.05)。结论:TMP通过阻滞BT474细胞停留在G₁期使其发挥增殖抑制作用的机制之一；TMP通过增强损伤缺口对各个通路的关键染色体结合蛋白募集，促进SSA与NHEJ修复通路活性从而减少DNA损伤。     

小鼠DNA双链断裂修复缺陷细胞的γ射线剂量率效应

目的：探讨γ射线照射后小鼠DNA双链断理解修复缺陷细胞（SCID）的剂量率效应和潜在致死性损伤的修复。方法：采用低剂量率和高剂量率以及间隔24h的2次γ射线照射正常细胞（CB．17＋／＋）和SCID细胞，通过成克隆分析法观察被照射细胞的存活分数。结果：应用间隔24h的2次γ射线照射CB．17＋／＋细胞时，其存活分数明显高于相同剂量的单次照射，而SCID细胞二者无明显差异。在高剂量率单次和2次γ射线照射时，SCID细胞均比CB．17＋／＋细胞更敏感。在低剂量率γ射线照射时，SCID细胞亦显示比CB．17＋／＋细胞更敏感。低剂量率γ射线照射 CB．17＋／＋细胞和SCID细胞后，二者的存活分数均明显高于剂量率照射。结论：SCID细胞不具有DNA双链断裂的修复能力。SCID细胞和CB．17＋／＋细胞均具有剂量率效应。     

DNA的损伤与修复

细胞的生物信息储存在DNA中。在真核细胞中,绝大多数（98％）DNA与蛋白质结合形成染色质存在于细胞核内,一小部分存在于其他细胞器中,如线粒体内。DNA由鸟嘌呤、腺嘌呤、胸腺嘧啶、胞嘧啶、戊糖和磷酸组成,碱基不同的排列顺序编码了不同的生物信息。在细胞的生存过程中,DNA会遭到内源性和外源性的损伤（表1）,例如放射线和化学物质。正常细胞的DNA损伤是诱发疾病的原     

DNA损伤修复与铂类耐药研究进展

铂类是非小细胞肺癌化疗的基本药物，它的耐药机制复杂，其中 DNA损伤修复能力改变是铂类耐药的重要分子基础。全文综述DNA损伤修复机制——碱基切除修复、恢苷酸切除修复、酶修复及DNA双链断裂修复等研究进展。     

DNA损伤修复与肺癌顺铂耐药机制的研究进展

肺癌是目前世界上致死率最高的恶性肿瘤,化疗是治疗的主要手段之一,肺癌的化疗是以铂类为基础的联合化疗,其中,顺铂是有效并广泛应用的一线药物,但是由于耐药问题的存在使其疗效不尽如人意。顺铂是一种细胞周期非特异性细胞毒药物,其主要作用靶点是DNA,因此DNA损伤修复功能的异常是顺铂耐药的主要机制之一。本文主要综述了与肺癌顺铂耐药相关的DNA损伤修复异常,包括核苷酸切除修复异常、碱基错配修复异常、DNA双链断裂损伤修复异常及跨损伤修复。     

DNA损伤修复调控因子与肿瘤耐药的研究进展

DNA分子是生物细胞中易受辐射损伤的敏感分子,亦称靶分子.多种理化因素如紫外线、电离辐射、化学诱变剂等导致细胞DNA损伤,同时生物体内本身又存在修复体系.肿瘤细胞DNA修复能力与化疗药物敏感性密切相关.本文综述DNA损伤修复机制-碱基切除修复、核苷酸切除修复、错配修复、DNA双链断裂修复等研究进展以及与肿瘤耐药之间的联系.     

β-榄香烯联合X线照射对肺腺癌A549细胞DNA损伤及修复影响

目的 探讨β-榄香烯联合放射对肺腺癌A549细胞DNA损伤及修复影响.方法 10、20 μg/mlβ-榄香烯作用于肺腺癌A549细胞24 h后进行X线照射.通过克隆形成实验观察β-榄香烯对A549细胞放射敏感性影响,采用彗星分析法探讨损伤修复的机制.结果 克隆形成实验结果显示β-榄香烯能增加A549细胞放射敏感性,10 μg/ml和20 μg/mlβ-榄香烯联合照射组的放射增敏比分别为1.55和1.64(D0值比)及1.43和1.75(Dq值比).20 μg/mlβ-榄香烯联合X线照射组与单独照射组和单独药物组0、2、6、24 h的彗星尾力矩相比有所增加,分别为7.16±2.61与0.95±0.65和1.81±1.23(F=231.24,P<0.01)、3.65±2.06与0.11±0.07和1.58±1.40(F=90.22,P<0.01)、2.09±0.83与0.1±0.05和0.45±0.25(F=238.44,P<0.01)、1.45±1.37与0.11±0.08和0.60±0.40(F=38.94,P<0.01),表明β-榄香烯与放射线联合对A549细胞DNA损伤增加和修复的抑制作用.结论 β-榄香烯对A549细胞放射敏感性的影响可能与其对DNA放射损伤及修复作用有关.

Abstract：

Objective To study if β-elemene can increase radiation-induced deoxyribonucleic acid (DNA) damage and decrease the damage repair.Methods Exponentially growing human lung adenocarcinoma cells (A549) were exposed to 10 or 20 μg/ml β-elemene for 24 h before irradiation.The effect of β-elemene on the in vitro radiosensitivity of A549 cells was evaluated using clonogenic assay.DNA damage and repair were evaluated using comet assay.Results Exposure to β-elemene before irradiation increased the radiosensitivity of A549 cells.The SERD0 for 10 μg/ml and 20 μg/ml β-elemene was 1.55 and 1.64, respectively.The SERDq for 10 μg/ml and 20 μg/ml β-elemene was 1.43 and 1.75, respectively.Combined treatment, comparing to irradiation or β-elemene treatment alone, induced higher levels of DNA damage and slower rate of damage repair.A549 cells exposed to 20 μg/ml β-elemene followed by irradiation showed a higher levels of tail moment (TM) than those exposed to irradiation or β-elemene alone at 0 h,2 h,6 h and 24 h after irradiation.The TM of the three groups at 0 h,2 h,6 h and 24 h after irradiation was 7.16±2.61,0.95±0.65 and 1.81±1.23(F=231.24,P<0.01), 3.65±2.06,0.11±0.07 and 1.58±1.40(F=90.22,P<0.01), 2.09±0.83,0.1±0.05 and 0.45±0.25(F=238.44,P<0.01), 1.45±1.37,0.11±0.08 and 0.60±0.40(F=38.94,P<0.01), respectively. Conclusions β-elemene can enhance the radiosensitivity of A549 cells through the enhancement of DNA damage and the inhibition of DNA damage repair.     

EGFR核转位与DNA损伤修复研究进展

表皮生长因子受体(epidermal growth factor receptor, EGFR)在许多人类恶性肿瘤中过表达或突变,参与肿瘤发生和恶性转变过程,是目前分子靶向治疗的热点。多种肿瘤组织细胞核内发现高水平的 EGFR 表达,并且已经证实核EGFR 的高表达与患者总体生存率、无病生存率负相关[1]。核EGFR 在肿瘤的形成、发展、转移及治疗耐受中发挥着重要的生物学功能,特别是核EGFR 能促进细胞生成和 DNA 损伤修复[2]。因此,核EGFR 与DNA 之间的相互关系值得深入研究。本文将综述EGFR 核转位通路及其与DNA 损伤修复的关系,并分析核EGFR 潜在的分子治疗靶点。     

PTEN in DNA damage repair

The ability of DNA repair in a cell is vital to its genomic integrity and thus to the normal functioning of an organism. Phosphatase and tensin homolog (PTEN) is a well-established tumor suppressor gene that induces apoptosis and controls cell growth by inhibiting the PI3K/AKT pathway. In various human cancers, PTEN is frequently found to be mutated, deleted, or epigenetically silenced. Recent new findings have demonstrated that PTEN also plays a critical role in DNA damage repair and DNA damage response. This review summarizes the recent progress in the function of PTEN in DNA damage repair, especially in double strand break repair and nucleotide excision repair. In addition, we will discuss the role of PTEN in DNA damage response through its interaction with the Chk1 and p53 pathways. We will focus on the newly discovered mechanisms and the potential implications in cancer prevention and therapeutic intervention.     

Decreased DNA repair activity in bone marrow due to low expression of DNA damage repair proteins

The bone marrow (BM) is one of the organs that is sensitive to acute exposure of ionizing radiation (IR); however, the mechanism of its high sensitivity to IR remains to be elucidated. BM is differentiated into dendritic cells (DC) with granulocyte macrophage-colony stimulating factor (GM-CSF). Using this in vitro model, we studied whether radiosensitivity is distinctly regulated in undifferentiated and differentiated BM. We discovered that levels of DNA damage repair (DDR) proteins are extremely low in BM, and they are markedly increased upon differentiation to DC. Efficiency of both homologous recombination (HR)- and non-homologous end joining (NHEJ)-mediated repair of DNA double strand breaks (DSBs) is much lower in BM compared with that of DC. Consistent with this, immunofluorescent γH2AX is highly detected in BM after IR. These results indicate that increased radiosensitivity of BM is at least due to low expression of the DNA repair machinery.     

Radiation induced DNA damage and damage repair in human tumor and fibroblast cell lines assessed by histone H2AX phosphorylation

PURPOSE: To analyze the radiation-induced levels of gammaH2AX and its decay kinetics in 10 human cell lines covering a wide range of cellular radiosensitivity (SF2, 0.06-0.63). METHODS AND MATERIALS: Five tumor cell lines included Colo-800 melanoma, two glioblastoma (MO59J and MO59K), fibrosarcoma HT 1080, and breast carcinoma MCF7. Five primary skin fibroblasts lines included two normal strains, an ataxia telangiectasia strain, and two fibroblast strains from breast cancer patients with an adverse early skin reaction to radiotherapy. Cellular radiosensitivity was assessed by colony-forming test. Deoxyribonucleic acid damage and repair were analyzed according to nuclear gammaH2AX foci intensity, with digital image analysis. RESULTS: The cell lines tested showed a wide degree of variation in the background intensity of immunostained nuclear histone gammaH2AX, which was higher for the tumor cell lines compared with the fibroblast strains. It was not possible to predict clonogenic cell survival (SF2) for the 10 cell lines studied from the radiation-induced gammaH2AX intensity. In addition, the slopes of the dose-response (0-4 Gy) curves, the rates of gammaH2AX disappearance, and its residual expression (相似文献   

“彗星” 法分析人肿瘤细胞DNA放射损伤和修复

探讨“彗星”分析法 (CA)在检测体外培养人肿瘤细胞DNA放射损伤与修复和放射敏感性的关系。方法　采用碱性CA检测鼻咽高分化鳞癌上皮细胞系 (CNE 1)、食管鳞癌上皮细胞系 (Ec 10 9)、肺腺癌细胞系 (GLC)和胃低分化腺癌细胞系 (BGC 82 3)经 6MVX射线照射后单细胞内DNA单链断裂 (SSB)程度及其与放射剂量的关系 ,以及CNE 1和GLC细胞系在分别接受了 16GyX射线照射后的自身修复情况 ,同时与相应的细胞存活曲线比较。结果　碱性CA可以检测出 4个细胞系DNA的SSB ,并与放射剂量呈良好的线性关系。 16Gy剂量下各细胞系的SSB程度依次为CNE 1>Ec 10 9>GLC >BGC 82 3。CNE 1,Ec 10 9,GLC和BGC 82 3细胞系的Do值分别为 1.2 5 ,1.2 7,1.88和 1.5 6。 16Gy诱导CNE 1和GLC细胞系的DNA损伤后 ,其半修复时间分别为 7.4,17.8min。结论　采用碱性CA能确切反映 4种人肿瘤细胞系DNA的定量损伤程度及其与放射剂量的关系 ,并能确切反映辐射损伤后自身修复能力 (CNE 1和GLC)在受测时间中的定量变化情况。自身修复能力的大小在鳞癌和腺癌细胞系间与放射敏感性的大小 (Do值 )有较好的对应关系。     

A novel bisindole-PBD conjugate causes DNA damage induced apoptosis via inhibition of DNA repair pathway

DNA damage response (DDR) that includes cell cycle check points, DNA repair, apoptosis, and senescence is intimately linked with cancer. It shields an organism against cancer development when genomic integrity fails. DNA repair pathways protect the cells from tumor progression caused as a result of DNA damage induced by irradiation or due to chemotherapeutic treatment. Many promising anticancer agents have been identified that target specific DNA repair pathways in response to DNA damage thereby leading to apoptosis. Here we identified a novel bisindole-PBD conjugate that possess potent anticancer activity in breast cancer cells. Further studies aimed at understanding the mechanism of action of the molecule showed its role in DNA damage induced apoptosis via inhibition of DNA repair pathway. Trypan blue and BrdU assay exhibited a dose-dependent effect. Single-stranded DNA damage was observed by COMET assay. In addition DNA damage induced ROS generation with simultaneous activation of ATM and ATR upon compound treatment was observed. Further downregulation of Bcl-XL and activation of Bax showed DNA damage induced apoptosis in MCF-7 and MDAMB-231 cells. In conclusion, it can be summarized that bisindole-PBD conjugate induces DNA damage in a dose dependent (2, 4, and 8 μM) manner by inhibiting the DNA repair genes.     

The role of DNA damage and repair in decitabine-mediated apoptosis in multiple myeloma

DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi) are under investigation for the treatment of cancer, including the plasma cell malignancy multiple myeloma (MM). Evidence exists that DNA damage and repair contribute to the cytotoxicity mediated by the DNMTi decitabine. Here, we investigated the DNA damage response (DDR) induced by decitabine in MM using 4 human MM cell lines and the murine 5T33MM model. In addition, we explored how the HDACi JNJ-26481585 affects this DDR. Decitabine induced DNA damage (gamma-H2AX foci formation), followed by a G0/G1- or G2/M-phase arrest and caspase-mediated apoptosis. JNJ-26481585 enhanced the anti-MM effect of decitabine both in vitro and in vivo. As JNJ-26481585 did not enhance decitabine-mediated gamma-H2AX foci formation, we investigated the DNA repair response towards decitabine and/or JNJ-26481585. Decitabine augmented RAD51 foci formation (marker for homologous recombination (HR)) and/or 53BP1 foci formation (marker for non-homologous end joining (NHEJ)). Interestingly, JNJ-26481585 negatively affected basal or decitabine-induced RAD51 foci formation. Finally, B02 (RAD51 inhibitor) enhanced decitabine-mediated apoptosis. Together, we report that decitabine-induced DNA damage stimulates HR and/or NHEJ. JNJ-26481585 negatively affects RAD51 foci formation, thereby providing an additional explanation for the combinatory effect between decitabine and JNJ-26481585.     

表观遗传学在肿瘤放射性DNA损伤修复中的研究进展

放疗通过放射线诱导肿瘤细胞DNA双链断裂来治疗癌症,但肿瘤细胞中异常的DNA双链断裂修复往往会导致放疗抵抗,而表观遗传学在其中发挥至关重要作用。靶向表观遗传学相关的重要分子可能是潜在的肿瘤放射增敏手段,但将表观遗传学药物与放疗联合的临床应用还需要进一步的机制研究。本文将对表观遗传学在肿瘤放射性DNA损伤修复中的作用最新进展进行综述。