UBR1 is a prognostic biomarker and therapeutic target associated with immune cell infiltration in gastric cancer
Authors: Yuan Weiwei , Han Jianye , Wu Zhiheng , Huang Yang , Deng Mao , Chen Chen , Xu Yuanmin , Qiu Yue , Zhang Ling , Dai Shiping , chen Zhangming , Xu Aman 
Published: July 2023

Background
Ubiquitination is a targeted protein modification process mediated by intracellular molecules. UBR1 encodes a protein that binds to unstable N-terminal residues of substrate proteins and contributes to the formation of substrate-linked polyubiquitin chains. However, the cellular pathways and the function of UBR1 in tumors have received inadequate attention. Therefore, the aim of this study is to examine the potential of UBR1 as a prognostic biomarker and immunotherapy target for stomach adenocarcinoma (STAD) as well as its biological function and molecular mechanism in relation to the disease.
Methods
Differential expression and pan-cancer GSEA analyses were performed using TCGA, GEO and GTEx datasets. Immunohistochemical differences between cancer and paraneoplastic tissues were analyzed using the HPA database to identify pathways enriched by UBR1 in AGS cells. Besides, with the help of Kaplan-Meier curves, univariate and multivariate Cox regression, and receiver operating characteristic (ROC) curve studies, the prognostic and diagnostic roles of UBR1 can be identified and determined. The correlation between UBR1 expression and clinical parameters was predicted by using the TCGA and GEO databases. The UBR1 mutation data were retrieved from the cBioPortal database. The biological mechanisms of UBR1 were investigated using GO and KEGG enrichment analyses. TIMER and EPIC computational methods were utilized to establish the connection between UBR1 and immune infiltration. Protein expression was determined using immunohistochemistry (IHC) and Western blot analysis (WB). In regard to mRNA expression, Quantitative Real-time PCR (qRT-PCR), it was analyzed by taking advantage of Quantitative Real-time PCR (qRT-PCR). Quantitative Immunoprecipitation (IP) assays were used to detect protein-protein interactions. Cell proliferation was evaluated using CCK8 and colony formation assays. Cell invasion was determined using wound healing assays and Transwell. Apoptosis was analyzed using flow cytometry.
Result
UBR1 was upregulated in 28 cancer types,including STAD, and its overexpression was validated in gastric cancer cell lines and tissues. UBR1 expression was associated with advanced pathological characteristics. High UBR1 expression was linked to poor prognostic outcomes, including progression-free interval (PFI), overall survival (OS), disease-specific survival (DSS), surgery, chemotherapy, and HER2 expression. UBR1 expression was significantly correlated with clinical parameters, such as age, gender, TMN stage, pathological stage, tumor resection, and anti-reflux therapy. Amplifications and deletions were the frequent genetic alterations associated with UBR1. According to the KEGG and GSEA, UBR1 was significantly associated with several cancer pathways, oxidative phosphorylation, and the TNF-NFκB pathway. UBR1 exhibited a significant correlation with immunotherapy and immune cell infiltration, and a direct interaction with CD274. Also, the proliferation and invasion of STAD cells were inhibited due to the UBR1 knockdown, but apoptosis was promoted in a contrary way.
Conclusion
The results of this investigation show that UBR1 is overexpressed in STAD, promoting its progression, and positively correlates with immune cell infiltration and immunotherapeutic responses. Therefore, UBR1 could be a promising biomarker in the prognosis and immunotherapy field of STAD.