Li Xiangzhao, Zhang Shifen, Zeng Jiamin, Song Sha-Sha, Liu Xiaoqing, Kang Wei, Liang Minyi, Yang Rui, Li Hong, Liang Li
Department of Pathology, Nanfang Hospital/Basic Medical College, Southern Medical University, Guangzhou 510515, Guangdong Province, People's Republic of China; Guangdong Province Key Laboratory of Molecular Tumor Pathology, Guangzhou 510515, Guangdong Province, People's Republic of China.
Department of Pathology, Nanfang Hospital/Basic Medical College, Southern Medical University, Guangzhou 510515, Guangdong Province, People's Republic of China; Department of Pathology, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University; The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen 518020, Guangdong, People's Republic of China.
Pathol Res Pract. 2023 Aug;248:154647. doi: 10.1016/j.prp.2023.154647. Epub 2023 Jul 2.
To investigate the heterogeneous expression patterns of four mismatch repair (MMR) proteins in colorectal cancer (CRC) and endometrial cancer (EC), and their effects on the interpretation of immunohistochemical (IHC) results. A total of 1636 CRC and EC specimens were collected from two hospitals. Seventy-eight cases had heterogeneous expression of MMR proteins, including 49 CRC and 29 EC cases. Polymerase chain reaction-capillary electrophoresis (PCR-CE) was then performed to detect the microsatellite instability (MSI) status, and 44 cases were further verified by targeted next-generation sequencing (NGS). Heterogeneous expression of MMR proteins was observed in 66 cases (66/78, 84.6%) of proficient MMR (pMMR) and 12 cases (12/78, 15.4%) of deficient MMR (dMMR). The proportion of heterogeneous MMR protein expression in EC (12.0%) was higher than that in CRC (3.5%). The heterogeneous expression patterns were divided into focal clonal heterogeneity (6/78, 7.7%) and glandular mosaic heterogeneity (72/78, 92.3%). Surprisingly, three pMMR CRC cases showed isolated small focal clonal heterogeneity of mutS homologue 6 (MSH6), with < 15% positive tumour cells, which was validated as high MSI (MSI-H) with PCR-CE and NGS. However, the other three EC pMMR cases with > 50% focal clonal heterogeneity of MMR proteins were verified as microsatellite stable (MSS) or low MSI (MSI-L). Fifteen EC cases with glandular mosaic heterogeneous expression of MMR proteins included two MSI-H cases, which were validated using PCR-CE and NGS. Among the dMMR cases, only two EC cases with mutL homologue 1 (MLH1)/PMS1 homologue 2, mismatch repair system component (PMS2) loss and MSH2/MSH6 mosaic heterogeneous expression were confirmed as MSS using PCR-CE and NGS, which may be related to the mechanism of MLH1 promoter methylation. Thus, in CRC, only cases with small focal clonal heterogeneous expression of MSH6 have a high likelihood of MSI-H, and further PCR-CE or NGS testing is recommended. The possibility of MSI-H cannot be ruled out in EC cases with glandular mosaic heterogeneous expression of MMR proteins; PCR-CE or NGS detection is therefore necessary.
研究四种错配修复（MMR）蛋白在结直肠癌（CRC）和子宫内膜癌（EC）中的异质性表达模式，以及它们对免疫组织化学（IHC）结果解读的影响。从两家医院共收集了1636例CRC和EC标本。78例存在MMR蛋白的异质性表达，其中包括49例CRC和29例EC。随后进行聚合酶链反应 - 毛细管电泳（PCR - CE）以检测微卫星不稳定性（MSI）状态，并通过靶向二代测序（NGS）对44例进行进一步验证。在错配修复功能正常（pMMR）的66例（66/78，84.6%）和错配修复功能缺陷（dMMR）的12例（12/78，15.4%）中观察到MMR蛋白的异质性表达。EC中MMR蛋白异质性表达的比例（12.0%）高于CRC（3.5%）。异质性表达模式分为局灶性克隆异质性（6/78，7.7%）和腺管镶嵌异质性（72/78，92.3%）。令人惊讶的是，3例pMMR CRC病例显示错配修复蛋白6（MSH6）存在孤立的小局灶性克隆异质性，阳性肿瘤细胞<15%，经PCR - CE和NGS验证为高度微卫星不稳定（MSI - H）。然而，另外3例MMR蛋白局灶性克隆异质性>50%的EC pMMR病例经验证为微卫星稳定（MSS）或低度微卫星不稳定（MSI - L）。15例MMR蛋白呈腺管镶嵌异质性表达的EC病例包括2例MSI - H病例，经PCR - CE和NGS验证。在dMMR病例中，仅2例错配修复蛋白MutL同源物1（MLH1）/错配修复蛋白PMS1同源物2（PMS2）缺失且错配修复蛋白MutS同源物2（MSH2）/MSH6呈镶嵌异质性表达的EC病例经PCR - CE和NGS确认为MSS，这可能与MLH1启动子甲基化机制有关。因此，在CRC中，只有MSH6呈小局灶性克隆异质性表达的病例有较高的MSI - H可能性，建议进一步进行PCR - CE或NGS检测。在MMR蛋白呈腺管镶嵌异质性表达的EC病例中不能排除MSI - H的可能性；因此有必要进行PCR - CE或NGS检测。
