微滴式数字PCR在检测胃腺癌和结直肠腺癌NTRK基因融合中的应用

Application of droplet digital PCR system for detecting NTRK fusionsin gastrointestinal adenocarcinomas

目的评估微滴式数字PCR(droplet digital PCR,ddPCR)应用于NTRK基因融合检测的可行性。方法回顾性分析830例原发性结直肠腺癌和560例胃腺癌样本,分别运用免疫组织化学(IHC)和荧光原位杂交(FISH)技术检测石蜡包埋肿瘤组织中pan-TRK蛋白表达情况以及NTRK1/2/3基因断裂情况。FISH及IHC阳性样本进一步行二代测序(NGS)检测及ddPCR检测。结果所有石蜡包埋肿瘤样本均成功进行IHC和FISH检测。FISH或IHC阳性样本合计26例,其中FISH阳性21例,IHC阳性18例。26例阳性样本进一步行RNA Seq NGS、DNA Seq NGS及ddPCR检测。DNA Seq NGS合计检测到14例NTRK基因融合,2例扩增。RNA Seq NGS合计检测到3例NTRK基因融合,ddPCR检测结果与RNA Seq NGS完全一致。结论ddPCR可有效区分FISH和DNA Seq NGS检测为NTRK非典型融合的结直肠腺癌和胃腺癌病例,可以作为除FISH之外NTRK基因初筛方法的补充。

Purpose To evaluate the feasibility of droplet digital PCR(ddPCR)for gene fusion detection of neurotrophic receptor kinase(NTRK).Methods A total of 830 cases of primary colorectal adenocarcinoma(CRAC)and 560 cases of gastric adenocarcinoma(GAC)were retrospectively studied.Immunohistochemistry(IHC)and fluorescence in situ hybridization(FISH)were used to detect pan-TRK protein expression and NTRK1/2/3 gene fracture in formalin-fixed paraffin-embedded(FFPE)tumor tissues,respectively.FISH or IHC positive samples were further detected by next generation sequencing and ddPCR.Results All FFPE samples were tested successfully by IHC and FISH methods.A total of 26 samples with NTRK gene breaks or pan-TRK expression were detected by IHC,among these 26 cases,21 FISH were positive and 18 IHC positive.A total of 14 cases of NTRK fusion and 2 cases of amplification were detected by DNA sequencing.A total of 3 cases carrying NTRK gene fusion were detected by RNA sequencing,and the results of ddPCR were completely consistent with RNA sequencing.Conclusion ddPCR can effectively distinguish false positive CRAC and GAC cases harboring NTRK fusion detected by FISH and DNA sequencing,which can be used as the effective method for screening NTRK gene fusion.