Background: Bicaudal-D (BICD) Family Like Cargo Adaptor 1 (BICDL1) is an essential component of the molecular mechanism during neuronal development. However, BICDL1 has not been reported in cancer. Using bioinformatics analysis, we systematically evaluated the potential role of BICDL1 in CRC.
Methods: Colorectal cancer (CRC) and normal tissue samples were retrieved from the Gene Expression Omnibus (GEO), Genotype-Tissue Expression (GTEx), and Cancer Genome Atlas (TCGA) databases. Kaplan–Meier (K-M) analysis, nomogram, COX analysis, and receiver operating characteristic (ROC) curves were used to evaluate the prognostic power. Correlation analysis was also conducted to explore the correlation between mRNA expression and the methylation level of BICDL1 using cBioPortal, and the correlation between immune infiltration and BICDL1. RT-qPCR and Western blot assays were performed to analyze BICDL1 expression level between human colorectal cancer cell lines and normal colonic epithelial cells.
Results: BICDL1 had a higher expression in CRC tissues than in normal tissues (p < 0.001) in TCGA and GES 74602 datasets. Kaplan-Meier survival analysis revealed that patients with high BICDL1 expression had lower overall survival (OS) (1.53, 95% confidence interval: 1.07– 2.17, p=0.019). The ROC curves demonstrated that BICDL1 has high specificity and efficiency in diagnosis (AUC=0.919, CI: 0.895– 0.943). The expression level of BICDL1 was significantly correlated with the infiltrating levels of Treg (R=0.146, p < 0.001), TFH (R=0.080, p=0.043), NK CD56bright cells (R=0.149, p < 0.001), aDC (R=0.095, p=0.016), and T helper cell infiltration (R=− 0.084, p=0.034). The correlation between BICDL1 expression and methylation levels was negative (R2=0.134, p < 0.001), and CRC patients had lower methylation levels than normal people (p=0.036). BICDL1 mRNA and its protein expression levels in CRC cell lines (SW620) was markedly increased compared with that of normal colonic epithelial cells (NCM460) (p < 0.001).
Conclusion: BICDL1 may be a potential biomarker for evaluating immune infiltration levels and prognosis of CRC.

Keywords: colorectal cancer, BICDL1, prognosis, biomarker, immune infiltration, methylation