DNA错配修复蛋白表达与胃腺癌临床病理特征的关系及意义

目的:检测DNA错配修复（mismatch repair，MMR）主要蛋白（MLH1、MSH2、MSH6和PMS2)在人胃腺癌组织中的表达，并分析错配修复缺陷（defective mismatch repair，dMMR）与胃腺癌临床病理因素及预后的关系。方法:采用免疫组织化学染色法检测4种MMR蛋白（MLH1、MSH2、MSH6和PMS2)在120例人胃腺癌组织中的表达，并从癌症基因组图谱（The Cancer Genome Atlas，TCGA）公共数据库下载432例胃腺癌患者的临床病理资料和微卫星不稳定性（microsatellite instability，MSI）的检测结果，分析MSI与胃腺癌临床病理特征的关系，利用TCGA的数据分析高频度微卫星不稳定（MSI-H）与胃腺癌患者预后的关系。结果:免疫组化染色结果显示在120例胃腺癌组织中，MMR蛋白表达正常（pMMR）组106例（88.3%），MMR蛋白表达缺失（dMMR)组14例（11.7%），其中MLH1缺失2例（1.7%）、PMS2缺失13例（10.8%）、MLH1和PMS2共同缺失2例（1.7%）、MSH2和MSH6共同缺失1例（0.8%）。统计分析结果显示，dMMR与胃腺癌淋巴结转移相关（P=0.022），而与其他临床病理因素无关。TCGA数据统计分析结果显示，MSI-H与胃腺癌患者年龄（P=0.001)、性别（P=0.000)、原发肿瘤部位（P=0.000)、Lauren分型（P=0.011）、肿瘤浸润深度T分期（P=0.024)、淋巴结有无转移（P=0.008)有关。Kaplan-Meier生存分析结果显示MSI-H型胃腺癌患者有预后更好的趋势，但差异不具有统计学意义（P=0.070）。结论:120例中国胃腺癌患者中MSI/dMMR型胃腺癌占比为11.7%，且dMMR状态与胃腺癌的淋巴结转移呈负相关；MSI-H型胃腺癌患者具有年龄大、多为女性、肿瘤多位于胃远端、肿瘤浸润深度T分期低、无淋巴结转移的特征，且MSI-H型胃腺癌具有预后更好的趋势，但不具有统计学意义。MSI状态与胃癌预后的关系尚需进一步深入研究和大样本数据的验证。     

DNA错配修复基因的遗传变异/突变与肿瘤治疗反应

DNA错配修复（mismatch repair,MMR）是一个复杂的生物学过程,在维持基因组完整性方面起着重要作用。微卫星不稳定性（microsatellite instability,MSI）由MMR蛋白功能缺陷导致。MMR基因的遗传变异或突变对肿瘤的发生、发展以及预后起到关键作用,其相关研究已取得显著成果。目前国内外多个指南建议对晚期实体瘤患者检测MMR/MSI,其结果可以预测肿瘤患者的预后,并可预测肿瘤辅助化疗及免疫治疗疗效,对治疗方案的选择具有指导意义。     

微卫星不稳定性(MSI)与胃癌关系的研究进展

因DNA错配修复（mismatch repair,MMR）基因的突变或表观遗传学的改变导致微卫星不稳定性（microsatellite instability,MSI）的产生被认为是胃癌发生的机制之一,许多研究表明高度微卫星不稳定型（MSI-H）胃癌有其独特的临床病理特征和较好的预后,但其中关于预后及化疗敏感性等方面也存在很多异质性结论,本文就MSI的基本概念、检测方法与指标及与胃癌关系的研究情况作一综述。     

微卫星不稳定性胃癌的研究进展和展望

胃癌是一种异质性较强的肿瘤,基于精准分型指导下的个体化治疗是目前的研究热点之一。微卫星不稳定性(MSI)是由于DNA错配修复系统缺陷导致微卫星片段出现的碱基对插入或丢失的现象,是肿瘤的发生机制之一。截至目前,有限证据表明高度MSI(MSI-H)胃癌展现出特定的临床特征、独特的肿瘤微环境、良好的预后以及对综合治疗的特殊反应,因此MSI状态可能是评估胃癌预后和预测治疗反应的良好标记物之一。近年来,免疫治疗在胃癌中的研究和获批给胃癌患者带来了新的治疗希望,而MSI-H患者也逐步被定义为胃癌免疫治疗的优势人群。本研究就MSI-H胃癌的基础及临床研究现状进行总结和讨论,旨在为胃癌的精准治疗提供参考依据。     

散发性结直肠癌微卫星不稳定状态与错配修复蛋白表达缺失及临床病理特征的相关性

目的： 探讨散发性结直肠癌微卫星不稳定(microsatellite instability,MSI)情况及其与错配修复 (mismatch repair,MMR) 蛋白MLH1、MSH2、MSH6、PMS2表达缺失的相关性,并总结MSI散发性结直肠癌的临床病理学特征。方法：多重荧光PCR法检测散发性结直肠癌肿瘤组织DNA的微卫星不稳定性,免疫组化(Immunohistochemistry,IHC)S-P法检测散发性结直肠癌肿瘤组织MLH1、MSH2、MSH6、PMS2蛋白的表达缺失,分析MSI发生与MMR蛋白表达缺失及临床病理特征的相关性。结果：75 例散发性结直肠癌检出MSI 21例(28%),包括 MSI-H 19例、MSI-L 2例,其他54例(72%)为MSS。检出MMR蛋白表达缺失16例(21.33%),其中15例(93.75%)为MSI-H、1例(6.25%)为MSS;MMR蛋白表达59例(78.67%),其中4例(6.78%)为MSI-H、2例(3.39%)MSI-L,其他53例为MSS。MSI组MMR蛋白缺失率(15/21,71.43%)显著高于MSS组(1/54,1.9%)（P<0.01）。MSI与患者年龄,是否黏液腺癌,肿瘤有无远处转移有关（P<0.01）,其中MSI-H好发于年龄>50岁、肿瘤无远处转移、MMR蛋白缺失人群,且类型以黏液腺癌为主。结论： 散发性结直肠癌肿瘤组织中MSI发生率高于MMR蛋白缺失率,并且MSI-H的散发性结直肠癌转移风险较低、预后较好。检测MSI 状态对提高结直肠癌的预防、诊断和治疗水平,降低结直肠癌的发病率和病死率有着重要意义。     

WRN基因有望成为耐药性结直肠癌治疗新靶点

DNA错配修复( dMMR)可以在DNA复制过程中识别和修复自发错配的碱基,微卫星不稳定性( MSI)是由dMMR受损引起的,是癌症中普遍存在的现象. Werner 解旋酶( WRN)是dMMR/MSI-H癌症的合成致死靶点,在结直肠癌细胞系中具有很大比例的敏感性. WRN是DNA解旋酶Re-cQ家族的成员之一,在维持...     

微卫星高度不稳定或错配修复缺陷结直肠癌新辅助免疫治疗的探讨和展望

微卫星高度不稳定（microsatellite instability-high,MSI-H）或错配修复缺陷（mismatch repair-deficient,dMMR）结直肠癌对传统新辅助治疗方案的敏感性较低，免疫治疗的出现改变了MSI-H/dMMR结直肠癌的治疗格局。从晚期疾病的后线治疗到一线治疗，甚至在早期结直肠癌的新辅助治疗，免疫治疗均展现出优异的疗效。全文探讨了结直肠癌新辅助免疫治疗的最新研究进展、目前存在的问题以及未来的发展方向，以期在临床实践过程中为MSI-H/d MMR结直肠癌患者制定个体化治疗方案提供参考。     

ASCO采纳的美国病理学家协会指南：免疫检查点抑制剂治疗的错配修复和微卫星不稳定性检测

美国病理学家协会（CAP）于2022年发布了用于免疫检查点抑制剂治疗的错配修复（MMR）和微卫星不稳定性（MSI）检测指南。该指南旨在解决多种癌症类型中MMR/MSI检测的相关问题，并就合适的检测方式的选择提供了建议，ASCO对其进行审核并采纳。该CAP指南中，IHC检测MMR(MMR-IHC)和（或）聚合酶链反应检测MSI(MSI-PCR)、NGS检测MSI均是结直肠癌推荐的检测方法；胃食管癌和小肠癌推荐MMR-IHC和（或）MSI-PCR；子宫内膜癌推荐MMR-IHC；上述癌种以外的其他类型癌症最佳检测方法尚未明确。肿瘤突变负荷不能作为检测错配修复缺陷（dMMR）的替代指标。若检测到符合Lynch综合征的dMMR则应告知主管医师。     

微卫星不稳定状态对Ⅳ期结直肠癌患者化疗反应性和预后的影响

背景与目的：错配修复缺陷导致的微卫星不稳(microsatellite inistability,MSI)状态对Ⅱ、Ⅲ期结直肠癌患者的预后及化疗敏感性有重要作用,但在晚期肠癌中研究较少。该研究探讨微卫星不稳对晚期结直肠癌患者化疗敏感性及预后的影响。方法：收集采用XELOX或FOLFOX为一线化疗方案的Ⅳ期肠癌患者的原发肿瘤组织,免疫组化方法检测肿瘤组织中错配修复基因hMLH1、hMSH2、hMSH6和hPMS2的蛋白表达,分析微卫星状态与患者临床特征、预后及化疗反应的相关性。结果：共收集113例晚期结直肠癌患者,未发现MSI与患者总体生存时间(overall survival,OS)以及化疗敏感性存在相关。亚组分析中我们发现79例原发灶姑息性切除的患者中,MSI 患者(22例)较MSS患者(57例)的中位无疾病进展时间(progression-free survival,PFS)明显延长(19.9个月vs 7个月,P=0.005),但MSI与OS无关(P=0.07)。对该79例患者预后行Cox多因素分析显示,MSI是影响患者PFS的独立危险因素(P=0.043,MSS/MSI,HR=2.079)。此外,该群患者的MSI状态与疾病控制率(59.1%vs 31.6%,P=0.025)相关。结论：在原发灶姑息性切除的Ⅳ期结直肠癌患者中,微卫星不稳定状态与无疾病进展时间和化疗的疾病控制率呈正相关,因而有必要对该群患者进行微卫星检测。     

微卫星不稳定性检测在结直肠外科的应用及其临床意义

结直肠癌中约15%患者存在基因组微卫星高度不稳定(MSI-H),最新的美国国立综合癌症网络与中国临床肿瘤学会指南均推荐所有结直肠癌患者都要进行微卫星不稳定(MSI)检测以判断预后,并可以用于林奇综合征的诊断与筛查;早发性结直肠癌患者的MSI-H频率更高,且好发于近端结肠(右半结肠),所以临床上对于年轻的结直肠癌患者,尤其是右半结肠癌患者,更应该重视MSI的检测。MSI-H的结直肠癌患者预后更好,免疫治疗对于MSI-H的结直肠癌疗效显著,目前国内外指南均建议MSI-H的结直肠癌全线推荐免疫治疗,但是MSI-H的误诊可能导致免疫一线治疗患者疾病进展,所以结直肠外科医师需要积极探索新的错配修复基因通路蛋白、微卫星不稳定性的检测位点及新的检测方式,以提高诊断准确率。     

Low prevalence of biliary tract cancer with defective mismatch repair genes in a Japanese hospital-based population

Recent studies have reported that immune checkpoint inhibitors are effective against various defective mismatch repair (dMMR)/microsatellite instability-high (MSI-H) cancers. A limited number of reports are available on the frequency of dMMR/MSI-H carcinoma in biliary tract cancer (BTC), describing its clinicopathological characteristics and prognosis. The latter carcinoma is also associated with Lynch syndrome (LS). The present study was performed to investigate the frequency of patients with dMMR/MSI-H in BTC and the clinical characteristics of BTC with dMMR/MSI-H in a single institution in Japan. A total of 116 patients with BTC who underwent curative surgical resection at Kagawa University Hospital between January 2008 and December 2017 were included. The protein expression levels of the mismatch repair (MMR) genes [mutL homolog 1 (MLH1), mismatch repair endonuclease PMS2 (PMS2), MutS homolog (MSH)2 and MSH6] were assessed by immunohistochemistry (IHC) using formalin-fixed paraffin-embedded tissue specimens. Subsequently, MSI testing was performed on patients who exhibited loss of MMR protein expression. Loss of expression of one or more proteins was detected in five cases (4.3%). Loss of MLH1/PMS2 expression was observed in one case of intrahepatic cholangiocarcinoma, whereas loss of PMS2 expression was noted in one case of perihilar cholangiocarcinoma. Loss of MSH2/MSH6 and MSH6 expression was noted in two cases of distal cholangiocarcinoma and loss of PMS2 expression in one case of ampullary carcinoma. Out of the five patients, two demonstrated MSI-H. Microsatellite stability was observed in two cases and for one case, no data were available. Two MSI-H cases were patients with loss of expression of MLH1/PMS2 and MSH2/MSH6. None of the five patients exhibited a past medical history or family history of suspected LS. The frequency of dMMR in BTC was ~5%, which was similar to that reported by similar studies performed in other countries. In the present study, IHC appeared to be more useful than MSI testing for detecting MMR abnormalities with regards to the detection rate. Furthermore, there may only be a limited number of patients with BTCs who are likely to benefit from the therapeutic effects of treatment with immune checkpoint inhibitors.     

Association between deficient mismatch repair system and efficacy to irinotecan-containing chemotherapy in metastatic colon cancer

The present study investigated the association between deficient mismatch repair (dMMR) and efficacy outcomes of irinotecan-based first-line chemotherapy in patients with metastatic colorectal cancer (mCRC). Among 297 patients with sporadic mCRC receiving an irinotecan-containing regimen as first-line chemotherapy, 197 with available paraffin-embedded tissues were included in the current analysis. Tumors displaying loss of MMR protein (MLH1 or MSH2) and/or a microsatellite instability-high (MSI-H) genotype by PCR were classified as dMMR. Deficient mismatch repair was found in 23 evaluable tumors, among which eight displayed negativity for MLH1 expression, 11 for MSH2 expression, and four for both. The overall response rate was 47.2% (46.0% in proficient MMR (pMMR) and 56.5% in dMMR), with no significant difference between the two groups (P = 0.569). Median progression-free survival was 8.85 months in patients with dMMR tumors and 6.82 months in patients with pMMR tumors, but this difference did not reach statistical significance (P = 0.089). Median overall survival was not different between the two groups (P = 0.413). Efficacy outcomes of first-line irinotecan-based chemotherapy did not differ significantly between mCRC patients with pMMR and those with dMMR. Our data collectively indicate that MMR status is not effective as a single predictive marker for response to irinotecan-based chemotherapy in mCRC patients.     

Microsatellite instability and colorectal cancer prognosis.

PURPOSE: Many studies have evaluated the role of high levels of microsatellite instability (MSI) as a prognostic marker and predictor of the response to chemotherapy in colorectal cancer (CRC); however, the results are not conclusive. The aim of this study was to analyze the prognostic significance of high levels of MSI (MSI-H) in CRC patients in relation to fluorouracil-based chemotherapy. EXPERIMENTAL DESIGN: In three different institutions, 1,263 patients with CRC were tested for the presence of MSI, and CRC-specific survival was then analyzed in relation to MSI status, chemotherapy, and other clinical and pathologic variables. RESULTS: Two hundred and fifty-six tumors were MSI-H (20.3%): these were more frequently at a less advanced stage, right-sided, poorly differentiated, with mucinous phenotype, and expansive growth pattern than microsatellite stable carcinomas. Univariate and multivariate analyses of 5-year-specific survival revealed stage, tumor location, grade of differentiation, MSI, gender, and age as significant prognostic factors. The prognostic advantage of MSI tumors was particularly evident in stages II and III in which chemotherapy did not significantly affect the survival of MSI-H patients. Finally, we analyzed survival in MSI-H patients in relation to the presence of mismatch repair gene mutations. MSI-H patients with hereditary non-polyposis colorectal cancer showed a better prognosis as compared with sporadic MSI-H; however, in multivariate analysis, this difference disappeared. CONCLUSIONS: The type of genomic instability could influence the prognosis of CRC, in particular in stages II and III. Fluorouracil-based chemotherapy does not seem to improve survival among MSI-H patients. The survival benefit for patients with hereditary non-polyposis colorectal cancer is mainly determined by younger age and less advanced stage as compared with sporadic MSI-H counterpart.     

Comparison of Tissue Mismatch Repair Protein Deficiency between Early- and Advanced-Stage Endometrial Cancer

Objective: ESGO/ESTRO/ESP guidelines recommend that DNA mismatch repair (MMR) proteins or microsatellite instability tests should be performed in all cases of endometrial cancer. This study aims to clarify the relationship of MMR protein deficiency (dMMR) between early and advanced stages of endometrial cancer. Secondary objective is to identify dMMR affecting factors in endometrial cancer. Methods: This cross-sectional study was conducted on endometrial cancer patients who underwent surgery at HRH Princess Maha Chakri Sirindhorn Medical Center, Srinakharinwirot University, between May 2013 and April 2021. Patients with endometrial cancer whose tumor tissue was available for analysis were identified. The expression of MMR proteins was assessed by immunohistochemistry, including MLH1, MSH2, MSH6, and PMS2. Then, the pathological specimens were reviewed. Results: A total of 207 patients with endometrial cancer were assessed for data analysis. MMR deficiency was observed in 92 cases (44.4%). We found patients with dMMR in both the early and advanced stages of endometrial cancer-68/155 cases (43.9%) and 24/52 cases (46.2%), respectively (P = 0.774).  Statistically significant differences were found only in myometrial invasion (adjusted prevalence odds ratio 2.35, 95% CI 1.21 to 4.57, P = 0.012). Conclusion: Our study showed no difference in tissue dMMR between early- and advanced-stage endometrial cancer. The dMMR was not associated with improved outcomes in patients with endometrial cancer. Even though ESGO/ESTRO/ESP guidelines recommend the performance of MMR IHC or MSI tests in all endometrial cancer cases, we can select the appropriate patients those categorized as “advanced stage” or “recurrent”-who may gain the most benefits from the immunotherapy modality of treatment.     

Single-Agent Neoadjuvant Immunotherapy With a PD-1 Antibody in Locally Advanced Mismatch Repair-Deficient or Microsatellite Instability-High Colorectal Cancer

BackgroundPD-1 blockade has been recommended as first-line therapy for nonresectable or metastatic mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) colorectal cancer (CRC). However, the safety and efficacy of neoadjuvant PD-1 blockade immunotherapy for locally advanced dMMR/MSI-H CRC remain unclear.Patients and MethodsFrom June 2020 to June 2022, 11 locally advanced dMMR/MSI-H CRC patients treated at the Sixth Affiliated Hospital of Sun Yat-sen University (Guangzhou, China) were enrolled. All patients received 6 sintilimab (Innovent, LTD) injections (200 mg/injection, every 3 weeks) before radical laparoscopic resection. The patient clinical and pathological data were analyzed retrospectively.ResultsdMMR was confirmed by immunohistochemistry for all patients. However, polymerase chain reaction (PCR) or next-generation sequencing confirmed MSI-H for only 90.9% (10/11) of the patients, while 1 patient had microsatellite stable (MSS) disease. After 6 injections of neoadjuvant anti-PD-1 therapy, 90.9% (10/11) of the patients (those confirmed to have dMMR and MSI-H disease) achieved pathological complete response (pCR). The other patient, who achieved major pathological response with residual tumor <1%, had dMMR but MSS disease. No grade 3 or above immunotherapy-related adverse events occurred [Common Terminology Criteria for Adverse Events ; version 5.0]. Overall, 72.7% (8/11) of the patients had grade 1-2 immunotherapy-related adverse events . No operational mortality or complications occurred within 30 days after surgery.ConclusionSingle-agent neoadjuvant PD-1 antibody immunotherapy was safe and effective in locally advanced dMMR/MSI-H CRC. Dual confirmation of MMR and MSI status by immunohistochemistry and next-generation sequencing or PCR is necessary for dMMR/MSI-H CRC patients before immunotherapy. The immunotherapy regimen used in this study deserves further validation in phase II and III clinical studies.     

肠癌微卫星状态检测方法的比较

目的:探索PCR法与IHC法对微卫星状态判断的差异性与一致性。方法:收集南京鼓楼医院病理科2014年6月至2015年12月病理诊断明确的大肠癌手术切除标本485例,所有标本的微卫星状态通过检测癌组织及正常组织中BAT25、BAT26、D5S346、D2S123及D17S250等5个标准位点的突变状态确定,并同时采用IHC法检测标本癌组织中MLH1、MSH2、MSH6和PMS2等DNA错配修复基因蛋白的表达,对比两种检测结果之间的一致性。结果:PCR法共检测到MSI状态39例,包括30例MSI-H和9例MSI-L,MSS状态446例,MSI占所有病例的8.04%,其中MSI-H的比率为6.19%。485例患者的免疫组化检测结果显示蛋白缺失（dMMR）者61例,蛋白不缺失（pMMR）者424例,dMMR占所有病例的12.58%。IHC法检测的灵敏度和特异度分别为86.67%和92.31%,两种方法检测微卫星状态的符合率为91.96%。结论:IHC法和PCR法检测微卫星状态具有较高的一致性,IHC法经济、便捷,更便于临床推广,当IHC法检测4种修复蛋白均无缺失时,则可以诊断为MSS/MSI-L,无需进一步行PCR,而当发现有任一修复蛋白有缺失时,则需行PCR检测进一步判定是否存在微卫星不稳定状态。我们的这一结论,将为临床工作节省大量的时间与成本。     

全自动IdyllaTM系统在中国结直肠癌微卫星不稳定性检测中的可行性研究

背景与目的：微卫星不稳定性（microsatellite instability,MSI）与错配修复（mismatch repair,MMR）基因缺陷,作为结直肠癌（colorectal cancer,CRC）等泛肿瘤免疫治疗的重要生物标志物之一,其检测近年来备受关注。目前临床上常用的多重荧光聚合酶链反应（polymerase chain reaction,PCR）检测MSI的传统方法（如Promega等）,通常需要非肿瘤组织对照及较长的检测周期。Idylla^TM系统作为一种全自动定量PCR装置,检测MSI无需非肿瘤组织对照,且运行时间仅为2.5 h,具有较好的临床应用前景。但在国内临床应用前,应在中国CRC患者中验证该方法的可靠性。方法：收集2017年3月—2019年3月复旦大学附属肿瘤医院的87例CRC患者用40%甲醛溶液固定石蜡包埋（formalin-fixed paraffin-embedded,FFPE）的组织样本,分别采用免疫组织化学（immunochemistry,IHC）、传统PCR（Promega）和Idylla^TM 3种方法进行MMR/MSI检测并比较分析,评估Idylla^TM系统临床检测的灵敏度和特异度以及在不同肿瘤含量样本中的可重复性。结果：87例CRC患者中,IHC和Promega的检测结果完全一致,其中56例被判定为MMR缺陷（deficient MMR,dMMR）/高度MSI（MSI-high,MSI-H）,31例为MMR完整（proficient MMR,pMMR）/微卫星稳定（microsatellite stable,MSS）。然而,其中4例dMMR/MSI-H患者被Idylla^TM MSI系统诊断为MSS,1例pMMR/MSS患者被诊断为MSI-H。若以IHC/Promega为参考标准,Idylla^TM MSI系统的诊断灵敏度为92.9%（52/56）,特异度为96.8%（30/31）,总体一致率达94.3%（82/87）。随后,应用Idylla^TM系统对上述不一致的5例患者进行重复检测,其中4例肿瘤含量≥20%的病例检测结果与IHC/Promega MSI检测一致,但1例肿瘤含量仅为5%的病例仍与IHC/Promega不一致,被误诊为MSS。最后,针对该病例,通过激光捕获显微切割技术对肿瘤细胞进行富集后,应用Idylla^TM MSI系统再次检测,结果显示为MSI-H。此外,选取5例具有不同肿瘤含量（20% ~ 60%）的病例,分别进行3次重复性验证,结果显示,Idylla^TM系统具有高度可重复性。结论：对于肿瘤含量≥20%的CRC患者,Idylla^TM系统可以为临床MSI检测提供一种快速、可靠、全自动的解决方案,并具有较高的灵敏度、特异度和可重复性。