The comprehensive molecular landscape of the immunologic co-stimulator B7 and TNFR ligand receptor families in colorectal cancer: immunotherapeutic implications with microsatellite instability

Abstract

Immunotherapy is reportedly effective in a subset of colorectal cancers (CRCs) with high microsatellite instability (MSI-H). Exploring the expression patterns and clinical values of immunologic molecules is critical in defining the specific responsive candidates. Here, we performed comprehensive molecular profiling of the B7 and TNFR family genes across 6 CRC datasets with over 1,000 patients' details using cBioPortal TCGA data. About 20% of patients had B7 and TNFR family gene alterations. The frequency of B7 gene mutations (2.2%-5%) were similar to copy number alterations (0.53%-5.46%). TNFR amplifications were relatively more common (5.45-11.32%) than that of B7 (0.09-2.73%). B7 and TNFR gene mRNAs were upregulated in 26% of cases (102/379) and 16% of cases (61/379), respectively. The mRNA levels of B7 and TNFR genes were inversely correlated with promoter methylation status. Clinically, both B7-H3 and TNFSF7 mRNA overexpression were associated with unfavorable clinical outcomes, and the B7-H3 expression was increased gradually in cases with gene amplifications. Moreover, patients with MSI-H had significantly higher PD-L1 or PD-1 expression. Most importantly, in MSI-H group, patients with PD-L1 or PD-1 upregulation had poorer survivals than those with PD-L1/PD-1 downregulation. This is the first study drawing the immune landscapes of the co-stimulator B7 and TNFR families in CRC and showing that MSI-H patients with PD-1/PD-L1 upregulation are associated with poor clinical outcomes, providing potential markers to stratify patients responsive to immune checkpoint therapy.

Keywords: B7 family; TNFR superfamily; checkpoint immunotherapy; colorectal cancer; microsatellite instable.

Figure 1.

The gene alteration frequencies in the B7 and TNFR families across 6 colorectal cancer studies. (A) Gene alterations of B7 and TNFR family. (B) Gene alterations of B7 family. (C) Gene alterations of TNFR family.

Figure 2.

The gene alterations and mRNA dysregulations of B7 and TNFR family genes in colorectal cancer. (A) Gene alterations and mRNA dysregulations of B7 and TNFR family genes. (B) Mutation alterations of B7 family genes. (C) Mutation alterations of TNFR family genes. (D) Copy number alterations (CNA) of B7 family genes. (E) CNAs of TNFR family genes. (F) mRNA dysregulations of B7 family genes. (G) mRNA dysregulations of TNFR family genes.

Figure 3.

The correlation between the promoter DNA methylation status and mRNA expression level of the B7 and TNFR families in colorectal cancer. (A) The mRNA levels of B7-1, B7-H3, B7-H6 and B7-H7 are negative correlated with their promoter methylated status respectively in 379 colorectal cancer (CRC) samples. (B) The mRNA levels of TNFSF4, TNFRSF5, TNFSF7 and TNFSF9 are negative correlated with their promoter methylated status respectively in 379 colorectal cancer samples. Spearman coefficient in red, relatively strong correlation; Spearman coefficient in black, poor correlation.

Figure 4.

B7-H3 and TNFSF7 are potential biomarkers in colorectal cancer. (A) Overall survival and disease-free survival of patients with upregulated B7-H3 mRNA in CRC. (B) B7-H3 genetic alteration in four studies from cBioPortal and increased B7-H3 mRNA levels with copy number variations in CRC samples. (C) TNFSF7 genetic alteration in four studies from cBioPortal and disease-free survival of patients with upregulated TNFSF7 mRNA in CRC. P values were determined using the log-rank test.

Figure 5.

B7-H1 and PD-1 are potential prognostic biomarkers in colorectal cancer with MSI-High status. (A) Spearman’s correlation between MSI status and B7 or TNSF mRNA expression. (B and C) B7-H1 (B) and PD-1 (C) mRNA expression levels in CRC with high-microsatellite instable (MSI-high, n = 35) and low- microsatellite instable/microsatellite stable (MSI-L/MSS, n = 149) status, respectively. Student’s t-test. (D) Overall survival and disease-free survival of patients with upregulated B7-H1 mRNA in CRC. (E) Disease-free survival of patients with upregulated PD-1 mRNA in CRC. P values were determined using the log-rank test.