Characteristic comparison between the low- and high-risk score groups

pRRophetic R package was used to predict IC₅₀ of 5-FU in each sample. IC₅₀ indicates the effectiveness of a substance in inhibiting specific biological or biochemical functions. ssGSEA was performed using “GSEABase” and GSVA R packages to quantify the extent of the immune-related infiltration of each sample in TCGA cohort. The gene sets were collected for evaluation of immune-related characteristics in TME from the previous study, including many different types of human immune cell subtypes and immune-related activities, such as CD8⁺ T cell, B cell, T cell co-stimulation, and so on (Table S1).34^,35 The enrichment scores calculated using the ssGSEA algorithm indicated a relative degree of each immune-related characteristic expression in each sample. The difference of enrichment scores in the low- and high-risk score groups was compared. The correlation between genes related to prognosis and immune cells was also evaluated. Finally, TIDE (http://tide.dfci.harvard.edu/) and SubMap (https://cloud.genepattern.org/gp) algorithms were used to predict immune checkpoint response inhibitors of PD-1 and CTLA4 in the low- and high-risk score groups. p value < 0.05 was considered statistically significant.