Friend or Foe: Prognostic and Immunotherapy Roles of BTLA in Colorectal Cancer

Abstract

Background: B and T lymphocyte attenuator (BTLA) is a co-signaling protein belonging to the CD28 immunoglobulin superfamily. However, the role of BTLA in prognosis and immunotherapy of colorectal cancer (CRC) remains unclear.

Methods: We evaluated the expression of BTLA via the Oncomine and the cancer genome atlas (TCGA) database. We research the outcome among different BTLA expression patients by Kaplan-Meier curve. We used the Chi-Squared test and Cox regression analysis to identify potential risk factors. Besides, the correlations between BTLA and cancer immune infiltration were investigated via CIBERSORT.

Results: Various cohorts showed that BTLA expression was lower in CRC compared to corresponding normal tissue. Moreover, low BTLA expression was correlated with poor overall survival in TCGA cohorts and Gene Expression Omnibus cohorts (GSE29623 and GSE17536). Low BTLA expression was associated with less lymph node metastasis (p = 0.0123). In the Cox proportional hazards model, BTLA was identified as a favorable prognostic factor. Naive B cells, memory B cells, CD8 T cells, CD4 memory resting T cells, follicular helper T (Tfh) cells, monocytes, resting natural killing (NK) cells, M0 macrophages, M1 macrophages, resting mast cells, and activated mast cells were affected by BTLA expression (all p < 0.01). Correlated immune markers and functional enrichment analysis revealed BTLA functioned in the T cell receptor signaling pathway, B cell receptor signaling pathway, and NK cell-mediated cytotoxicity pathway.

Conclusion: These analyses suggest BTLA is a potential factor for extended survival and closely related to CD8 T cells, Tfh cells, B cells, and NK cells in CRC. We summarize these results that BTLA can be used as a prognostic biomarker and might contribute to developing novel CRC immunological treatment strategies.

Keywords: BTLA; colorectal cancer; immunotherapy; prognosis; tumor-infiltration.

FIGURE 1

The expression of BTLA in colorectal cancer and other cancer types. (A) BTLA mRNA levels in different cancer types by TIMER database. *p < 0.05, **p < 0.01, ***p < 0.001. (B) BTLA in different cancer data sets increased or decreased compared with normal tissues detected by the Oncomine database. (C) BTLA expression levels in whole tumorous tissues and normal tissues in TCGA cohorts. ****p < 0.0001. (D) BTLA expression levels in tumor tissues and paired normal adjacent tissues in TCGA cohorts.****p < 0.0001.

FIGURE 2

Kaplan-Meier survival curves comparing the different expression of BTLA groups in colorectal cancer in TCGA cohorts and GEO cohorts. (A–D) Survival curves of OS, DSS, DFI, PFI in TCGA colorectal cancer cohorts. (E,F) Low BTLA expression was correlated with poor OS in the GEO cohorts. OS, overall survival; DSS, disease-specific survival; DFI, disease-free interval; PFI, progression-free interval.

FIGURE 3

BTLA-related immune infiltration alteration. (A) The group with high expression of BTLA is red, and the group with low expression of BTLA is blue. Naive B cells, memory B cells, CD8 T cells, CD4 memory resting T cells, follicular helper T cells, resting NK cells, M1 macrophages and resting mast cells share a higher proportion in high expression group compared with low expression group. On the contrary, the proportion of monocytes, M0 macrophages, activated mast cells are apparently lower. (B) The proportions of different immune infiltration cells subpopulations were weakly to highly correlated. ns, p > 0.05; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.

FIGURE 4

Function enrichment analysis of the co-expressed genes of BTLA. KEGG and GO biological process enrichment of BTLA co-expressed genes (A) The top 10 enrichment results of the BP, CC, and MF category. (B) The top 30 enrichment results of the KEGG signal pathway. Clusters are based on the gene count to measure the similarity between terms. BP, biological process; CC, cellular component; MF, molecular function; KEGG, Kyoto Encyclopedia of Genes and Genomes.