Aim: In this report, we performed a comprehensive analysis of data in colorectal cancer (CRC), to elucidate the association among Solute Carrier Family 4 Member 4 (SLC4A4) and the abundance of immunological features and immune cell infiltration in CRC, and to explore the impact of SLC4A4 on the CRC tumor microenvironment.
Background: Colorectal cancer (CRC) cases with advanced or distal metastases experience a survival rate of less than 20%, with the lack of spectral therapeutic targets and prognostic markers posing a significant challenge for CRC treatment. SLC4A4 may be a CRC-targeted therapy for which there is currently inadequate evidence Objective: To deeply and systematically reveal the characteristics of the tumor microenvironment created by SLC4A4.
Methods: We downloaded RNA sequencing files (TCGA-COADREAD), clinical data for Colon Cancer (COAD) and Rectal Cancer (READ) from the Cancer Genome Atlas. We evaluated the spearman correlation of SLC4A4 with immune features, Tracking Tumor Immunophenotype (TIP) score, and immune checkpoint gene expression. SLC4A4/immunity-related differentially expressed genes (DEGs) were identified in SLC4A4 expression groups and immune groups, and an assessment system for predicting CRC prognosis was constructed based on univariate COX and multivariate COX analyses. Based on the prognostic factors in CRC, we also constructed a nomogram to assess the survival risk status of CRC. Besides, we evaluated the potential association of SLC4A4 to immunotherapy.
Results: We found that SLC4A4 expression trended positively with immune checkpoint expression (PD-L1, CTLA4) and promoted infiltration of 27 immune cells. SLC4A4 promoted the infiltration of CD8 T cells, Dendritic cells, Macrophage, NK cells, and Th1 cells in CRC, shaping the inflammatory tumor microenvironment. Up-regulation of SLC4A4 expression might promote drug response to Anti-FGFR3_therapy, Anti-PPARG_therapy, Nivolumab, Ipilimumab in CRC patients, and down-regulation of SLC4A4 expression might promote drug response to Anti-EGFR_therapy, Aflibercept drug response. Based on the SLC4A4/immunization-related DEGs, we constructed RiskScore to assess the prognosis of CRC, which showed excellent predictive effect and robustness. RiskScore showed a trend of negative correlation with SLC4A4, which was consistent with the trend of the effect of SLC4A4 on CRC survival. Besides, RiskScore could also be useful for predicting patient prognosis. Finally, we constructed a nomogram for predicting CRC survival based on metrics with independent prognostic value (Age, M stage, Stage, RiskScore), which showed potential clinical value.
Conclusion: Overall, upregulation of SLC4A4 expression promoted an inflammatory tumor microenvironment in CRC, and RiskScore predicted therapeutic expectancy. SLC4A4 could be a potentially clinically valuable target for CRC therapy.
Keywords: Colorectal cancer; SLC4A4; immunogenicity; immunotherapy; prognosis.
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