肌层浸润性膀胱尿路上皮癌MDM2扩增与PD-1/PD-L1抑制剂耐药机制TCGA数据库资料分析

Potential mechanisms of MDM2 amplification participating in PD-1/PD-L1 inhibitor resistance in muscle invasive bladder urothelial carcinoma:An analysis based on The Cancer Genome Atlas database

目的免疫检测点抑制剂能延长晚期膀胱尿路上皮癌患者的生存,但仍面临耐药问题,其机制是目前的研究热点。本研究通过分析癌症基因组图谱(The Cancer Genome Atlas,TCGA)数据库中肌层浸润性膀胱尿路上皮癌的鼠双微基因2(murine double minute 2,MDM2)扩增情况及相关基因表达,寻找免疫检查点抑制剂耐药的潜在机制。方法于2019-04-01从TCGA数据库下载自建库至2014-11-15肌层浸润性膀胱尿路上皮癌数据包"bladder cancer(TCGA,cell2017)",含临床信息、基因拷贝数变异与核糖核酸测序数据,共412例患者,其中408例患者有基因拷贝数信息。对比MDM2扩增(36例)和未扩增(372例)的2组患者间临床特征和预后差异;利用cBioportal和DAVID6.8在线分析mRNA表达与MDM2扩增相关基因,并进行功能富集分析;进一步采用cBioportal和GeneSpringGX软件筛选出MDM2扩增和未扩增组间表达有差异的基因。结果肌层浸润性膀胱尿路上皮癌中MDM2扩增发生率为8.8%(36/408)。MDM2基因扩增组和未扩增组,总人群的中位生存期为33.1和35.0个月(χ^2=0.759,P=0.384),根治术后患者的中位无疾病生存期为18.0和35.7个月(χ^2=2.921,P=0.087),差异均无统计学意义。对mRNA水平与MDM2扩增相关的357个基因进行KEGG功能富集分析显示,36个基因富集于代谢通路(校正P=0.090),14个基因富集于内吞作用通路(校正P=0.280),但差异无统计学意义。MDM2扩增时自身mRNA水平增高,并与FRS2、RAB3IP、YEATS4、RAP1B和CPSF6mRNA水平中度正相关;其中FRS2、RAB3IP、RAP1B、CPSF6与MDM2常同时扩增。MDM2扩增与常见免疫抑制因子PD-1(PDCD1)、PD-L1(PDCD1LG2)、CTLA4、LAG3和IDO1的mRNA水平低度负相关。结论MDM2扩增与非扩增肌层浸润性膀胱尿路上皮癌患者的多个基因mRNA表达水平存在差异,可能为研究免疫检测点抑制剂耐药机制提供线索。

OBJECTIVE Immune checkpoint inhibitors(ICIs)prolong the survival of bladder urothelial carcinoma patients,but they still face with challenges of drug resistance.In this study,we investigated the potential mechanisms of murine double minute 2(MDM2)amplification and the resistance to ICIs in muscle invasive bladder urothelial carcinoma.METHODS The"bladder cancer(TCGA,cell 2017)"dataset(412 patients)was downloaded from the TCGA database on April 1 st 2019,containing clinical information,copy number alteration and RNA-Seq V2 data.There were 408 patients with copy number data,and they were divided into two groups,with(36 patients)and without(372 patients)MDM2 amplification(MDM2 amp),respectively.Clinicopathological features and survival were compared between these two groups.Genes whose mRNA level correlates with MDM2 amp were identified by cBioportal online analysis,and analysis of their functional enrichment was performed by Kyoto Encyclopedia of Genes and Genomes(KEGG)using DAVID6.8 online analysis.Genes differentially expressed between patients with and without MDM2 amp were identified by cBioportal online analysis and Gene Spring GX software.RESULTS The incidence of MDM2 amp in muscle invasive bladder urothelial cancer was 8.8%(36/408).Differences in medium overall survival of general population(33.1 months vs 35.0 months,χ^2=0.759,P=0.384)and medium disease free survival of population after radical resection(18.0 months vs35.7 months,χ^2=2.921,P=0.087)between patients with or without MDM2 amp were not significant.The mRNA level of 357 genes were correlated with MDM2 amp.The functional enrichment analysis of KEGG of these genes showed that36 genes were insignificantly enriched in the metabolic pathway(corrected P=0.090),and 14 genes were insignificantly enriched in the endocytosis pathway(corrected P=0.280).MDM2 amp was correlated with higher mRNA level of MDM2 itself,and was positively correlated with the mRNA level of the following genes:FRS2,RAB3 IP,YEATS4,RAP1 Band CPSF6.Co-amplification of FRS2,RAB3 IP,RAP1 Band CPSF6 with MDM2 had a high frequency.However,MDM2 amp was negatively correlated with the mRNA level of the following common immune inhibiting factors:PD-1(PDCD1),PD-L1(PDCD1 LG2),CTLA4,LAG3,and IDO1.CONCLUSION There were differences in the mRNA level of several genes between patients with and without MDM2 amp,which would be clues for further investigation of the underlying mechanisms between MDM2 amp and ICIs’resistance.