2.5. Correlation of the EPI with tumour mutational burden (TMB), microsatellite instability (MSI), and immune infiltration

Immune-associated data were downloaded from the Immune Cell Abundance Identifier database (http://bioinfo.life.hust.edu.cn/ImmuCellAI/#!/). The Estimation of STromal and Immune cells in MAlignant Tumour tissues (ESTIMATE) algorithm was used to approximate the levels of immune components and overall stroma [27]. Pearson's correlation coefficient was used to assess the relevance of the EPI to TMB; MSI; immune parameters (stromal, immune, and ESTIMATE scores); and the expression of immune checkpoint, immunostimulatory, immunosuppressive, and major histocompatibility complex (MHC), chemokine, and chemokine receptor genes. The correlation between the EPI and Tumour Immune Dysfunction and Exclusion (TIDE) score was evaluated in the cancers. Three immunotherapy cohorts [IMvigor210, {"type":"entrez-geo","attrs":{"text":"GSE32894","term_id":"32894"}}GSE32894, and {"type":"clinical-trial","attrs":{"text":"NCT02684006","term_id":"NCT02684006"}}NCT02684006 (PMID: 32895571)] were used to validate the effect of the EPI on immunotherapy outcomes.