Prognostic value of FUBP1 in Colorectal cancer and association with immune microenvironment characteristics

To investigate FUBP1 expression, its prognostic value, impact on the tumor microenvironment (TME), and drug sensitivity in colorectal cancer (CRC), and to explore its potential underlying mechanisms.

Using data from The Cancer Genome Atlas (TCGA), we analyzed FUBP1 expression in CRC, evaluated its prognostic value via survival analysis and nomogram construction, performed pathway enrichment analysis, and assessed immune cell infiltration and Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data (ESTIMATE) scores. We further conducted immunohistochemistry (IHC) validation on an independent institutional cohort and analyzed the Gene Expression Omnibus (GEO) single-cell RNA sequencing dataset GSE132465 (n = 63,689 cells) to examine the association between FUBP1 expression and the tumor immune microenvironment at single-cell resolution.

FUBP1 was highly expressed in CRC (P < 0.001), particularly in younger patients. High FUBP1 expression was associated with improved overall survival in univariate analysis (HR = 0.68, P = 0.028), yet this association was not maintained as an independent prognostic factor after adjustment for other clinical covariates (HR = 0.722, P = 0.098). Immunohistochemistry results from the independent cohort confirmed upregulated FUBP1 protein in 90% of CRC specimens. Single-cell analysis revealed that FUBP1-high cell clusters exhibited markedly reduced immune cell infiltration (35.97%vs 62.96%, P < 0.001), indicating an immunosuppressive "cold" tumor microenvironment. Tumors with high FUBP1 expression also displayed elevated PD-L1, PD-1, and CTLA4 expression, lower half-maximal inhibitory concentration (IC50) values for oxaliplatin, irinotecan, and 5-fluorouracil, and higher Immune Phenotype Score (IPS) for anti-PD-1 monotherapy or combined anti-CTLA-4 immunotherapy. FUBP1 expression was correlated with increased expression of MYC, TP53, and their downstream target genes (CCND1, CDK4, BAX, CDKN1A).

FUBP1 is highly expressed in CRC and associated with an immunosuppressive "cold" tumor microenvironment characterized by decreased immune cell infiltration, while it correlates with favorable chemotherapeutic sensitivity. FUBP1 may serve as a potential predictive biomarker for responses to chemotherapy and immunotherapy, rather than an independent prognostic indicator for survival. Its linkage to MYC and TP53 signaling pathways warrants further mechanistic investigation.