Abstract：
OBJECTIVE: There are no established biomarkers for immune checkpoint inhibitors (ICI) in colorectal cancer (CRC) with microsatellite stability (MSS) or proficient mismatch repair (pMMR). Therefore, this study aimed to identify biomarkers for ICI benefit in patients with pMMR by analyzing the down-regulated DNA repair-related genes involved in highly immunogenic and immune responses, and comparing their expression levels and clinical features.
METHODS: Mismatch repair (MMR), tumor-infiltrating lymphocytes (TIL), and tumor mutation burden (TMB) were evaluated in 13 CRC cases and mRNA expression levels of 95 DNA repair-related genes were measured. DNA repair-related genes with reduced mRNA expression in the high immunogenicity and high immune response groups were identified. Then, the mRNA expression levels of the identified DNA repair-related genes were measured in 135 patients with CRC. Hierarchical cluster analysis was performed using the mRNA expression levels to compare the clinicopathological characteristics of each cluster.
RESULTS: ATR, LIG4, and RAD52 mRNA levels were significantly down-regulated in the high immunogenicity group. GADD45B, SMUG1, and XRCC6 mRNA levels were significantly down-regulated in the high immune response group. Cases in the cluster with reduced mRNA expression of the six genes were pMMR cases. CD8 mRNA expression level was higher in this cluster than in the other clusters.
CONCLUSIONS: Decreased mRNA expression levels of ATR, LIG4, RAD52, GADD45B, SMUG1, and XRCC6 genes were associated with high cytotoxic T cell and TMB levels, suggesting that these genes could serve as biomarkers for ICI efficacy in pMMR cases.
METHODS: Mismatch repair (MMR), tumor-infiltrating lymphocytes (TIL), and tumor mutation burden (TMB) were evaluated in 13 CRC cases and mRNA expression levels of 95 DNA repair-related genes were measured. DNA repair-related genes with reduced mRNA expression in the high immunogenicity and high immune response groups were identified. Then, the mRNA expression levels of the identified DNA repair-related genes were measured in 135 patients with CRC. Hierarchical cluster analysis was performed using the mRNA expression levels to compare the clinicopathological characteristics of each cluster.
RESULTS: ATR, LIG4, and RAD52 mRNA levels were significantly down-regulated in the high immunogenicity group. GADD45B, SMUG1, and XRCC6 mRNA levels were significantly down-regulated in the high immune response group. Cases in the cluster with reduced mRNA expression of the six genes were pMMR cases. CD8 mRNA expression level was higher in this cluster than in the other clusters.
CONCLUSIONS: Decreased mRNA expression levels of ATR, LIG4, RAD52, GADD45B, SMUG1, and XRCC6 genes were associated with high cytotoxic T cell and TMB levels, suggesting that these genes could serve as biomarkers for ICI efficacy in pMMR cases.
摘要：
目的：在具有微卫星稳定性（MSS）或有效错配修复（pMMR）的结直肠癌（CRC）中，没有建立免疫检查点抑制剂（ICI）的生物标志物。因此,这项研究旨在通过分析与高度免疫原性和免疫反应有关的下调DNA修复相关基因，来确定pMMR患者ICI获益的生物标志物。并比较它们的表达水平和临床特征。
方法：不匹配修复(MMR)，肿瘤浸润淋巴细胞（TIL），在13例CRC中评估了肿瘤突变负荷（TMB），并测量了95个DNA修复相关基因的mRNA表达水平。鉴定了在高免疫原性和高免疫应答组中mRNA表达降低的DNA修复相关基因。然后，在135例CRC患者中检测了已鉴定的DNA修复相关基因的mRNA表达水平.使用mRNA表达水平进行层次聚类分析，以比较每个簇的临床病理特征。
结果：ATR，在高免疫原性组中,LIG4和RAD52mRNA水平显著下调。GADD45B,SMUG1和XRCC6mRNA水平在高免疫应答组中显著下调。6个基因的mRNA表达减少的簇中的病例为pMMR病例。该簇中的CD8mRNA表达水平高于其他簇。
结论：ATRmRNA表达水平降低，LIG4,RAD52,GADD45B,SMUG1和XRCC6基因与高细胞毒性T细胞和TMB水平相关，提示这些基因可作为pMMR病例ICI疗效的生物标志物。
方法：不匹配修复(MMR)，肿瘤浸润淋巴细胞（TIL），在13例CRC中评估了肿瘤突变负荷（TMB），并测量了95个DNA修复相关基因的mRNA表达水平。鉴定了在高免疫原性和高免疫应答组中mRNA表达降低的DNA修复相关基因。然后，在135例CRC患者中检测了已鉴定的DNA修复相关基因的mRNA表达水平.使用mRNA表达水平进行层次聚类分析，以比较每个簇的临床病理特征。
结果：ATR，在高免疫原性组中,LIG4和RAD52mRNA水平显著下调。GADD45B,SMUG1和XRCC6mRNA水平在高免疫应答组中显著下调。6个基因的mRNA表达减少的簇中的病例为pMMR病例。该簇中的CD8mRNA表达水平高于其他簇。
结论：ATRmRNA表达水平降低，LIG4,RAD52,GADD45B,SMUG1和XRCC6基因与高细胞毒性T细胞和TMB水平相关，提示这些基因可作为pMMR病例ICI疗效的生物标志物。
