Bone marrow stromal antigen 2 is associated with immune microenvironment of colorectal cancer

Aims: This study aimed to investigate the involvement of bone marrow stromal antigen 2 (BST2) in the immune microenvironment of colorectal cancer (CRC). Methods BST2 expression profiles, clinical information, and chemosensitivity data of CRC patients were downloaded from TCGA, GEO, and GDSC databases. The relationship between BST2 and immune cell infiltration was evaluated using CIBERSORT and TIMER. Immune-related coexpressed genes of BST2 were identified by GeneMANIA and Immport. A prognostic model containing BST2 and immune-related genes was constructed and tested by ROC curves. Kaplan-Meier plot was used for survival analysis. BST2 promoter methylation and the correlation of BST2 expression with TMB and MSI were assessed using UALCAN and SangerBox. Results BST2 mRNA levels were significantly increased in high-stage CRC tumors compared with those in low-stage tumors and correlated with poor survival of patients. The fractions of M1 macrophages, CD8 + T cells, and gamma delta T cells were markedly increased in patients with high BST2 expression versus those with low BST2 expression. IFITM1, ISG15, MX1, and OAS1 were identified as immune-related coexpressed genes of BST2 in CRC and performed well in predicting the overall survival of patients. Furthermore, BST2 expression was associated with DNA methylation and positively correlated with TMB and MSI in CRC. BST2 expression also positively correlated with IC50 values of chemotherapeutic agents in patients with MSI-L/MSS CRC. Conclusion BST2 upregulation is associated with the immune microenvironment of CRC and poor prognosis of patients. Patients with high expression of BST2 or MSI-H CRC may respond well to immunotherapy.