Novel colon cancer tumor suppressor gene, β-defensin 1, to predict recurrence in patients with stage II and III colon cancer.

Abstract

3622 Background: Human β-defensin 1 (hBD-1) encoded by the DEFB1 gene is an antimicrobial peptide involved in the innate immune response and is expressed in epithelial cells, including the colon. hBD-1 has been shown to have tumor suppressor functions in urothelial cancer models. We tested whether 4 germline single nucleotide polymorphisms (SNPs) in DEFB1 could predict time to tumor recurrence (TTR) in stage II and III colon cancer (CC) patients. We then sought to demonstrate if hBD-1 has tumor suppressor functions in CC models. Methods: A total of 234 patients, 105 stage II and 129 stage III, treated with 5-FU-based chemotherapy at the University of Southern California were included. The median follow-up time was 4.4 yrs. SNPs were analyzed from whole blood samples using direct DNA-sequencing. To gain insight into hBD-1’s function, hBD-1 expression in CC cell lines was determined by qRT-PCR and Western blotting. hBD-1 expression was induced ectopically and CC cells and viability, membrane permeability, cell-cycle and apoptosis analyzed. Results: Stage III patients with rs1800972 DEFB1 -44G containing genotypes had longer TTR than patients with C/C genotype (11.3 mo vs 2.7 mo; p=.008). In contrast in stage II, patients with rs1799946 DEFB1 -52A containing genotypes, had significantly longer TTR than patients with G/G genotype (16.8 mo vs 5.9 mo; p=.017). In the multivariate analysis, both DEFB1 -44C/G and DEFB1 -52G/A SNPs remained significant, respectively in stage III (HR=.419; 95%CI .201-.87; p=.020) and in stage II (HR=.360; 95%CI .152-.853; p=.020). Haplotype of all four SNPs was significantly associated with stage-specific TTR (to be presented at the meeting). In CC cell line models, there was a loss of hBD-1 expression, and induction of hBD-1 expression resulted in a loss of cell viability, membrane permeability and the induction of apoptosis. Conclusions: The results demonstrate for the first time evidence of hBD-1’s potential influence on the microenvironment and its role as a tumor suppressor in CC. Further studies need to be conducted to better understand the role of hBD-1 in CC development and progression and evaluate the potential utility of hBD-1 as a therapeutic strategy.