Abstract 1526: Evaluation of the novel tumor suppressor gene, β-Defensin-1, in colorectal cancer cell line models.

Abstract

Background: Human defensins are antimicrobial linear peptides with broad anti-microbial activity, organized into two classes, α- and β-defensins. Human β-Defensin 1 (hBD-1) is encoded by the DEFB1 gene located on chromosome 8p23 and functions as an antimicrobial peptide involved in the innate immune response. It is most often expressed in epithelial cells, including those in the large intestines. Previous experiments have shown that hBD-1 exhibits tumor suppressor functions in urothelial and kidney cancer cells. Previous evaluation of germline single nucleotide polymorphisms in the promoter region of DEFB1 demonstrated CRC stage specific effects of rs1800972 and rs179946 in predicting time-to-tumor recurrence in CRC patients. This study examined the cancer specific expression of hBD-1 in CRC compared to normal cells and further evaluated the cellular mechanism associated with the effects of hBD-1 expression in CRC proliferation, cell cycle progression and apoptosis. Methods: Twenty-two patients colon tissue samples were subjected to immunohistochemistry (IHC) specific for hBD-1 to examine its expression in both normal and tumor cells. To gain insight into the effects of hBD-1 expression in CRC, CaCo2, HCT116, HT29 and SW620 CRC cell lines were transfected with pCMV6-XL4-DEFB1, alongside a control empty vector, to compare the effect of hBD-1 overexpression on cell viability and apoptosis at 24 and 48 hr. In addition, recombinant hBD-1 was exogenously added to CRC cells and analyzed for the effect on cell viability. Results: Examination of hBD-1 expression from patients’ colon tissue samples by IHC demonstrated that hBD-1 expression was present in the normal colon cells, but its expression was lost in CRC cells. Induction of hBD-1 expression in CRC cell lines resulted in a significant change in cell viability, membrane permeability and induction of apoptosis. Further, the exogenous addition of recombinant hBD-1 to CRC cells resulted in a significant reduction in cell number at 48 hr. Conclusion: These results demonstrate evidence of loss of hBD-1 expression in CRC cells and further provide evidence for hBD-1’s potential role as a tumor suppressor. Further studies are being conducted to determine the pathway of apoptosis that is induced and to better understand the hBD-1 affects in the CRC cells development and progression and further evaluate the potential utility of targeting hBD-1 as a therapeutic strategy. Citation Format: Austin Layton, Pierre O. Bohanes, Wu Zhang, Heinz-Josef Lenz, Melissa J. Labonte. Evaluation of the novel tumor suppressor gene, β-Defensin-1, in colorectal cancer cell line models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1526. doi:10.1158/1538-7445.AM2013-1526

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“…Studies have also reported it to be an important marker for colorectal cancer. A study by Layton et al[ 29 ] presented at American Association of Cancer Research 104th Annual Meeting in 2013 reported that β-defensins 1 was expressed in colon tissue samples of normal subjects while this expression was lost in subjects with colorectal cancer. While another study by Melle et al[ 30 ], reported that α-defensins are expressed more in colonic epithelium of patients with colorectal cancer than in normal epithelium, establishing defensins potential role as a tumor markers[ 30 ].…”