胃癌微卫星不稳定和KRAS基因突变与肿瘤免疫微环境的关系

Relationship between microsatellite instability,KRAS gene mutations and tumor immune microenvironment of gastric cancer

目的检测胃癌患者微卫星不稳定(MSI)和KRAS基因突变状态,探讨两者相互关系及对肿瘤免疫微环境的影响。方法收集胃癌90例,采用多重荧光PCR法检测MSI,ARMS-PCR法检测KRAS基因第2号外显子突变,通过流式细胞分析术检测部分胃癌术后标本TILs CD8和PD-1表达水平。结果 MSI在胃癌中总发生率43.3%,KRAS基因突变率为8.89%,两者均在性别、年龄、肿瘤分期方面差异无统计学意义(P>0.05),两者之间不存在明显相关性(r=-0.037)。在不同MSI状态或KRAS基因突变背景下,胃癌组织TILs中CD8表达水平差异均无统计学意义(P>0.05)。KRAS基因突变与PD-1表达水平无明显相关性(P>0.05)。MSI-H组PD-1表达水平显著高于MSI-L组和MSS组(P<0.01)。结论 MSI发生和KRAS基因突变是胃癌形成过程中的相对独立事件,MSI-H表达的胃癌患者可能受益于肿瘤免疫治疗。

Objective To investigate the changeable pattern of microsatellite instability(MSI) and mutations ofKRAS gene in gastric cancer(GC), and to explore the relationship between MSI,KRAS gene mutations and tumor immune mi-croenvironment(TME) in GC.MethodsA total of 90 gastric cancer patients were included. The multiplex fluorescencepolymerase chain reaction(PCR) was conducted to detect the status of MSI, the amplification refractor mutation system PCR(ARMS-PCR) was conducted to detect mutations in exon 2 of KRAS gene, and the expressions of CD8 and PD-1 in tumor-infiltrating lymphocytes(TILs) were detected by flow cytometry.ResultsIn gastric cancer, the occurrence rates of MSI andKRAS gene mutations were 43.3% and 8.89% respectively. No correlation was found between MSI and KRAS gene mutations(r=-0.037). There was no significant difference between/among different ages, genders or tumor stage in either MSI or KRASgene mutations(P>0.05).There was no statistic difference among different status of MSI or KRAS gene mutations in the CD8 expression in TILs(P>0.05). It was the same to PD-1 expression in TILs at different status of KRAS gene mutations(P>0.05).However, PD-1 expression in the MSI-H group was higher than thosein the MSI-L group and MSS group(P<0.01).ConclusionMSI and KRAS gene mutations are independent events during gastric tumorigenesis. It may be beneficial to gastriccancer patients with MSI-H from tumor immunotherapy.