NOTCH3 serves as a potential biomarker for radioresistance and is correlated with the immunosuppressive microenvironment in rectal cancer

Background: ： Radioresistance significantly hinders tumor regression in locally advanced rectal cancer (LARC). Identifying potential biomarkers associated with radioresistance is essential for guiding treatment selection in rectal cancer. Methods: ： In this study, we analyzed mRNA expression datasets of rectal adenocarcinoma (READ) obtained from the Gene Expression Omnibus (GEO) databases to identify differentially expressed genes (DEGs) by comparing radiotherapy responders and non-responders. To identify common DEGs, we constructed a Venn diagram using an online tool. Furthermore, we used the Kaplan–Meier Plotter to screen for target genes associated with the prognosis of READ. The mRNA expression of the target gene was determined using TCGA-COAD (READ) and R language. Moreover, we investigated the relationship between NOTCH3 and immune cell-associated gene markers via TIMER and GEPIA. Finally, we used immunohistochemistry (IHC) to validate the expression of NOTCH3 in READ and to establish the correlation between NOTCH3 expression and radioresistance. Results: : The expression of NOTCH3 was up-regulated in the rectal cancer radiotherapy non-responders. Elevated NOTCH3 expression was found to be associated with shorter overall survival in READ. NOTCH3 expression exhibited a positive correlation with the levels of infiltrating CD4+ T cells, macrophages, neutrophils, and dendritic cells. Additionally, the expression level of NOTCH3 demonstrated a significant correlation with gene markers associated with TAM, M2 macrophages, Treg cells, and T cell exhaustion. Conclusions: : Our research demonstrate NOTCH3 may serve as a prognostic biomarker for predicting radioresistance linked to immunosuppression in READ. Targeting NOTCH3 could be a promising therapeutic approach to improve the efficacy of radiotherapy.