Objective: To investigate the relationship between the expression of four mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2) and NTRK genetic fusions in colorectal cancer. Methods: The paraffin-embedded tissue blocks of 830 cases of colorectal cancer were collected at the Affiliated Drum Tower Hospital, Nanjing University Medical School, China, from 2015 to 2019. Immunohistochemical and fluorescence in situ hybridization(FISH) method were used respectively to detect the expression of mismatch repair proteins and the break-apart of NTRKs; and the relationship between the expression of mismatch repair proteins and the NTRK genetic fusions was analyzed. Results: The overall mismatch repair protein deficiency (dMMR) rate was 9.88% (82/830), the mismatch repair proteins proficiency (pMMR) rate was 90.12%(748/830). The total deficiency rate of MLH1 protein was 9.04% (75/830), hPMS2 protein deficiency rate was 9.04% (75/830), MSH2 protein deficiency rate was 2.53% (21/830), MSH6 protein deficiency rate was 4.10% (34/830), the deficiency rate of synchronous MLH1 and PMS2 were 8.67% (72/830) and the deficiency rate of synchronous MSH2 and MSH6 were 2.17% (18/830). The dMMR group was associated with tumor location, different histological subgroups, tumor differentiation, AJCC stage and N stage (P<0.05). There were six cases (7.32%) carrying NTRK fusion by FISH among the 82 cases of dMMR, but only seven cases (0.94%) carrying NTRK fusion among the 748 cases of PMMR. The NTRKs translocation by FISH in all 13 cases were further confirmed by next generation sequencing. Among the clinicopathological characteristics, only differentiation showed significant difference between NTRK fusion positive and negative groups (P<0.05). More importantly, NTRK fusion was enriched in dMMR group (7.32% vs. 0.94%). Conclusion: In dMMR colorectal cancer group, the prevalence of NTRK fusion is higher than that in pMMR group.
目的： 探讨结直肠癌中错配修复蛋白缺陷（dMMR）与NTRK基因融合的相关性。 方法： 收集南京大学医学院附属鼓楼医院病理科2015—2019年诊断为结直肠癌的组织蜡块830例，分别运用免疫组织化学和荧光原位杂交（FISH）检测830例甲醛固定石蜡包埋（FFPE）肿瘤组织中错配修复蛋白表达情况以及NTRK1/2/3基因断裂情况。比较dMMR型和错配修复蛋白无缺陷（pMMR）结直肠癌中NTRK1/2/3基因融合的发生率，进一步运用FFPE样本进行RNA Seq二代测序检测，分析融合伴侣和融合方式。 结果： 830例原发性结直肠癌FFPE样本均成功进行免疫组织化学和FISH检测。dMMR病例82例（9.88%），pMMR病例748例（90.12%）。其中MLH1蛋白缺失比例为9.04%（75/830），PMS2蛋白缺失比例为9.04%（75/830），MSH2蛋白缺失比例为2.53%（21/830），MSH6蛋白缺失比例为4.10%（34/830），MLH1和PMS2共缺失比例为8.67%（72/830），MSH2和MSH6共缺失比例为2.17%（18/830）。伴有dMMR肿瘤与pMMR肿瘤相比较，在发生部位、组织学分型、分化程度、美国癌症联合会（AJCC）分期、N分期及NTRK基因融合的发生频率上差异有统计学意义（P<0.05）。在82例dMMR的病例中共检测到6例（7.32%）携带NTRK基因融合；而在748例pMMR的病例中共检测到7例（0.94%）携带NTRK基因融合。二代测序进一步证实13例FISH检测阳性的病例均为携带了NTRK基因融合，NTRK基因融合阳性组仅在分化程度上与融合阴性组差异有统计学意义（P<0.05）。 结论： 在原发性结直肠癌中，携带dMMR的肿瘤其NTRK基因融合的比例远高于pMMR的肿瘤。.