Enhanced repair of DNA interstrand crosslinking in ovarian cancer cells from patients following treatment with platinum-based chemotherapy

Despite high tumour response rates to platinum-based chemotherapy in ovarian cancer survival is poor due to the emergence of drug resistance. Mechanistic studies in clinical material have been hampered by the unavailability of sensitive methods to detect the critical drug-induced effects in individual cells. A modification of the single cell gel electrophoresis (comet) assay allows the sensitive detection of DNA interstrand crosslinking in both tumour and normal cells derived directly from clinical material. Tumour cells isolated from 50 ovarian cancer patients were treated ex vivo with 100 microM cisplatin for 1 h and crosslink formation and repair (unhooking) measured. No significant difference in the peak level of crosslinking in tumour cells was observed between patients who were either newly diagnosed or previously treated with platinum-based therapy, or between tumour and mesothelial cells from an individual patient. This indicates no difference in cellular mechanisms such as drug transport or detoxification. In contrast, the percentage repair (unhooking) of DNA interstrand crosslinks was much greater in the group of treated patients. At 24 h in the 36 newly diagnosed patient tumour samples, only one gave >50% repair and 23 gave <10% repair; however, 19 out of 22 treated patient samples gave >10% repair and 14 showed >50% repair. The estimated median difference (newly diagnosed minus treated) was -52 (95% CI -67 to -28), and the P-value from a Mann-Whitney test was <0.001. In eight patients, it was possible to obtain tumour samples prior to any chemotherapy, and also on relapse or at interval debulking surgery following platinum-based chemotherapy. In these patients, the mean % repair prior to therapy was 2.85 rising to 71.23 following treatment. These data demonstrate increased repair of DNA interstrand crosslinks in ovarian tumour cells following platinum therapy which may contribute to clinical acquired resistance.     

Personalising Treatment for High-Grade Serous Ovarian Carcinoma

Ovarian cancer is a heterogeneous group of cancers that differ by cell of origin and genomic features. High-grade serous ovarian cancer (HGSOC) is the commonest histiotype and is characterized by extreme genomic complexity and dysregulation of DNA damage repair pathways, particularly homologous recombination deficiency. New insights from molecular profiling into homologous recombination deficiency now offers the credible possibility of personalizing treatment choices for women with HGSOC using poly(ADP-ribose) polymerase inhibitor (PARP) therapy. Although the presence of tumour infiltrating lymphocytes (TILs) in the microenvironment is associated with improved survival in HGSOC, the role of anti-angiogenic and immune checkpoint inhibitor therapy remains unclear. PARP inhibition combined with immunotherapy is an exciting combination strategy for future therapeutic development for women with advanced HGSOC.     

Targeting DNA damage response in cancer therapy

Cancer chemotherapy and radiotherapy are designed to kill cancer cells mostly by inducing DNA damage. DNA damage is normally recognized and repaired by the intrinsic DNA damage response machinery. If the damaged lesions are successfully repaired, the cells will survive. In order to specifically and effectively kill cancer cells by therapies that induce DNA damage, it is important to take advantage of specific abnormalities in the DNA damage response machinery that are present in cancer cells but not in normal cells. Such properties of cancer cells can provide biomarkers or targets for sensitization. For example, defects or upregulation of the specific pathways that recognize or repair specific types of DNA damage can serve as biomarkers of favorable or poor response to therapies that induce such types of DNA damage. Inhibition of a DNA damage response pathway may enhance the therapeutic effects in combination with the DNA‐damaging agents. Moreover, it may also be useful as a monotherapy when it achieves synthetic lethality, in which inhibition of a complementary DNA damage response pathway selectively kills cancer cells that have a defect in a particular DNA repair pathway. The most striking application of this strategy is the treatment of cancers deficient in homologous recombination by poly(ADP‐ribose) polymerase inhibitors. In this review, we describe the impact of targeting the cancer‐specific aberrations in the DNA damage response by explaining how these treatment strategies are currently being evaluated in preclinical or clinical trials.     

Survival of Patients with Ovarian Cancer due to a Mismatch Repair Defect

Purpose: Hereditary non-polyposis colorectal cancer (HNPCC, Lynch syndrome) is characterized by the development of cancer of the colorectum, endometrium and other cancers. Cancer of the ovaries (OC) has frequently been reported in HNPCC. Colorectal cancer associated with HNPCC has a better survival chance compared to sporadic colorectal cancer. It is yet unknown whether patients with OC from HNPCC families (OC–HNPCC) also have a better survival. Therefore, the aim of the study was to compare the survival between patients with OC–HNPCC and a control group. Methods: A total of 26 patients with OC were identified from the Dutch HNPCC Registry. A control group (52 cases) matched for age, stage and year of diagnosis was derived from the population-based Eindhoven Cancer Registry. Data on treatment were collected for all patients. Kaplan–Meier analysis was used to calculate the crude survival. Results: The mean age at diagnosis of OC–HNPCC was significantly lower than the age of sporadic OC (49.5 vs 60.9 years). Compared to sporadic OC, OC–HNPCC was diagnosed at an earlier stage. The survival rate was not significantly different between patients with OC–HNPCC and the controls with sporadic OC. The cumulative 5-year-survival rates were 64.2 and 58.1% respectively. Conclusion On the basis of our findings, we recommend to treat OC–HNPCC similar to sporadic OC.     

DNA Repair Gene Associated with Clinical Outcome ofEpithelial Ovarian Cancer Treated with Platinum-basedChemotherapy

Objective: The nucleotide excision repair (NER) and base excision repair (BER) pathways, two DNA repairpathways, are related to platinum resistance in cancer treatment. In this paper, we studied the association betweensingle nucleotide polymorphisms (SNPs) of involved genes and response to platinum-based chemotherapy inepithelial ovarian cancer. Method: Eight SNPs in XRCC1 (BER), XPC and XPD (NER) were assessed in 213patients with epithelial ovarian cancer using polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) and primer-introduced restriction analysis-polymerase chain reaction (PIRA-PCR) techniques.Results: The median progression-free survival (PFS) of patients carrying the Lys/Lys and Lys/Gln+Gln/Glngenotype of the XPC Lys/Gln polymorphism were 25 and 12 months, respectively (P=0.039); and the mean overallsurvival (OS) of patients was 31.1 and 27.8 months, respectively (P=0.048). Cox’s multivariate analysis suggestedthat patients with epithelial ovarian cancer with the Gln allele had an increased risk of death (HR=1.75; 95%CI=1.06-2.91) compared to those with the Lys/Lys genotype. There are no associations between the XPC PAT+/-,XRCC1 Arg194Trp, Arg280His, Arg399Gln, and XPD Asp312Asn, Lys751Gln polymorphisms and the survivalof patients with epithelial ovarian cancer when treated with platinum-based chemotherapy. Conclusion: Ourresults indicated that the XPC Lys939Gln polymorphism may correlate with clinical outcome of patients withepithelial ovarian cancer when treated with platinum-based chemotherapy in Northern China.     

The ups and downs of DNA repair biomarkers for PARP inhibitor therapies

PARP inhibitors are emerging as a valuable new drug class in the treatment of cancer. Recent discoveries make a compelling case for the complexity of DNA repair biomarker evaluation and underscore the need to examine at multiple biomarkers in a relational manner. This review updates the current trends in DNA repair biomarker strategies in use for the PARP inhibitors and describes the impact of many DNA repair biomarkers on PARP inhibitor benefit in the cancer clinic.     

晚期卵巢上皮癌初治方案选择的预测因素

目的探讨晚期卵巢上皮癌初治方案选择的预测因素。方法根据初治方案将120例晚期卵巢上皮癌患者分为先行手术组（78例）和先期化疗再间期手术组（简称：先期化疗组）（42例），分析了影响初次手术成功率的因素以及先期化疗对间期手术成功的作用。采用Logistic回归方法，用Log-rank和Kaplan-Meier方法分析生存率。结果先行手术组的手术成功率为46．2％（36／78），先期化疗组的手术成功率为59．5％（25／42）。研究表明降低初次手术成功率的因素有腹水、CA125〉500U／L、道格拉斯窝异常。有腹水及CA125〉500U／L的患者经先期化疗后的间期手术成功率高于初次手术（P〈0．05）。结论对晚期卵巢上皮癌在选择治疗方案前分析预测因素是有益的。它有助于筛选出宜初次手术和以先期化疗为最佳初次治疗方案的病例。     

腹腔静脉双途径化疗治疗晚期卵巢癌

采用卡铂腹腔内化疗及阿霉素和环磷酰胺的静脉内化疗方法，治疗１４例晚期卵巢癌，结果完全缓解５例，部分缓解７例，因疾病进展死亡２例，有效率达８５．７％。表明腹腔内及静脉内双途径化疗治疗晚期卵巢癌为一理想的治疗措施。     

The Future of Targeted Therapies in Ovarian Cancer

Ovarian cancer is the second most common gynecological malignancy and the leading cause of death from gynecological cancer. Most women present with advanced disease with little prospect for cure. There have been some advances in surgical and chemotherapeutic strategies, but these approaches have led to only minor improvements in outcome. There remains a significant risk for recurrence and resistance to therapy, and hence there is a need to improve upon the current treatment options. Molecularly directed therapy aims to target tumor cells and the tumor microenvironment by blocking specific molecular changes in the cancer. The most promising agents so far are the antiangiogenic agents and polyadenosine diphosphate‐ribose polymerase inhibitors. This article reviews the various targeted therapeutic approaches under clinical investigation in ovarian cancer and the challenges facing their future success in the clinic.     

卵巢癌与DNA修复功能相关的研究

对４０例卵巢肿瘤患者和１００例健康人的外周血淋巴细胞按经典的非顺序性ＤＮＡ合成法进行ＤＮＡ修复功能测定。其结果表明卵巢癌患者的ＤＮＡ修复功能明显低于健康者，二者间有显著性差异。另外通过实验利用紫外线照射诱导人淋巴细胞的ＤＮＡ非顺序性合成，估价个体ＤＮＡ修复能力，对癌患者进行前瞻性研究，提供了对癌易感个体的检出方法和早期预防的可能性。     

A Pan-Canadian Consensus Statement on First-Line PARP Inhibitor Maintenance for Advanced,High-Grade Serous and Endometrioid Tubal,Ovarian, and Primary Peritoneal Cancers

The majority of patients with advanced, high-grade epithelial-tubo ovarian cancer (EOC) respond well to initial treatment with platinum-based chemotherapy; however, up to 80% of patients will experience a recurrence. Poly(ADP-ribose) Polymerase (PARP) inhibitors have been established as a standard of care maintenance therapy to prolong remission and prevent relapse following a response to first-line platinum-chemotherapy. Olaparib and niraparib are the PARP inhibitors currently approved for use in the first-line maintenance setting in Canada. Selection of maintenance therapy requires consideration of patient and tumour factors, presence of germline and somatic mutations, expected drug toxicity profile, and treatment access. This paper discusses the current clinical evidence for first-line PARP inhibitor maintenance therapy in patients with advanced, high-grade EOC and presents consensus statements and a treatment algorithm to aid Canadian oncologists on the selection and use of PARP inhibitors within the Canadian EOC treatment landscape.     

siRNA干扰Id1表达增强卵巢癌细胞对顺铂的敏感性

[目的]探讨体外DNA结合抑制因子（inhibitor of DNA bindingor differentiation,Id）的表达对卵巢上皮癌SKOV3对顺铂化疗敏感性的影响。[方法]构建靶向Id1基因siRNA慢病毒载体并转染SKOV3细胞,筛选出稳定转染的SKOV3细胞克隆。实验分为4组：实验组（Cell＋LvshRNA-Id1）、阴性对照组（Cell＋Lv-shRNA-NC）、病毒对照组（Cell＋Lv-control）与空白对照组（Cell group）。CCK8检测各组SKOV3细胞不同时间增殖活性以及暴露于不同浓度顺铂（0.1、0.2、0.5、1、2、5、10μg/ml）48h后顺铂对各组SKOV3细胞的半数抑制浓度,分析沉默Id1基因后卵巢癌细胞对顺铂化疗敏感性的影响。[结果]三组对照组细胞增殖活性随着时间增加显著,而实验组则增加缓慢。在48h和72h时,实验组细胞增殖活性值分别为0.449±0.072μg/ml、0.885±0.232μg/ml,与三组对照组比较差异均有统计学意义（P均〈0.05）;实验组顺铂对SKOV3细胞的半数抑制浓度为1.5±0.71μg/ml,明显低于对照组（P〈0.01）。[结论]抑制Id1基因表达可以增加顺铂对卵巢癌细胞的生长抑制作用,为临床进一步提高卵巢癌的疗效提供了研究基础。     

c-jun反义核酸消除人体卵巢癌细胞的抗药性研究

目的:c-jun反义核酸消除人体卵巢癌细胞抗药性探讨.方法:采用c-jun反义核酸处理抗药型人体卵巢癌细胞,观察c-jun,γ-GCS以及GSH在两种细胞内的表达水平.结果:c-jun反义核酸可抑制c-jun基因的表达并降低谷胱苷肽合成的关键酶γ-GCS的mRNA表达量,使抗药型细胞内GSH含量降低大约75%.ATT分析结果也表明,经c-jun反义核酸处理后,抗药型细胞对顺铂的IC_(50)从40μmol/L降低到1.0μmol/L,对敏感型细胞无明显影响(0.2μmol/L).结论:c-jun反义核酸可特异地抑制抗药型细胞内c-jun基因的表达并间接抑制γ-GCS的表达,最终抑制GSH的合成,从而消除卵巢癌细胞的抗药性.     

Ifosfamide and Etoposide Salvage Treatment in Advanced Ovarian Cancer

Summary

Twelve FIGO stage III-IV ovarian cancer patients progressing or relapsing after primary cisplatin-containing combination chemotherapy were treated with ifosfamide and etoposide. Only patients with clinically evaluable disease entered the trial. The 12 patients received a median number of 3 courses (range 1-6). No complete or partial response and two disease stabilizations were observed. Ten patients progressed on therapy. The combination of ifosfamide and etoposide does not appear to be an effective salvage treatment for advanced ovarian cancer.     

Sublethal concentrations of 17-AAG suppress homologous recombination DNA repair and enhance sensitivity to carboplatin and olaparib in HR proficient ovarian cancer cells

The promise of PARP-inhibitors(PARPis) in the management of epithelial ovarian cancer(EOC) is tempered by the fact that approximately 50% of patients with homologous recombination (HR)-proficient tumors do not respond well to these agents. Combination of PARPis with agents that inhibit HR may represent an effective strategy to enhance their activity in HR-proficient tumors. Using a bioinformatics approach, we identified that heat shock protein 90 inhibitors(HSP90i) may suppress HR and thus revert HR-proficient to HR-deficient tumors. Analysis of publicly available gene expression data showed that exposure of HR-proficient breast cancer cell lines to HSP90i 17-AAG(17-allylamino-17-demethoxygeldanamycin) downregulated HR, ATM and Fanconi Anemia pathways. In HR-proficient EOC cells, 17-AAG suppressed HR as assessed using the RAD51 foci formation assay and this was further confirmed using the Direct Repeat-GFP reporter assay. Furthermore, 17-AAG downregulated BRCA1 and/or RAD51 protein levels, and induced significantly more γH2AX activation in combination with olaparib compared to olaparib alone. Finally, sublethal concentrations of 17-AAG sensitized HR-proficient EOC lines to olaparib and carboplatin but did not affect sensitivity of the HR-deficient OVCAR8 line arguing that the 17-AAG mediated sensitization is dependent on suppression of HR. These results provide a preclinical rationale for using a combination of olaparib/17-AAG in HR-proficient EOC.     

Novel Directions in Adjuvant Chemotherapy for Early Stage Epithelial Ovarian Cancer

Treatment of early stage ovarian cancer remains controversial despite advances in chemotherapeutic options.Over the past 30 years, molecular and clinicopathologic studies accelerated and treatment of ovarian cancer hasundoubtedly improved although there is a debate as to whether this impacts outcome or not. More recently, theintroduction of targeted therapy started a new era. Probably it is because early stage disease comprises a smallportion of the epithelial ovarian cancer, studies have mostly ignored this group and still there is no clear consensusregarding systemic treatment of early-stage lesions. However this group of patients has the best chance of cure.In this review, we focus on current developments in the treatment of early stage ovarian cancer and query theoptions.