574 Transgenic Epithelial Expression of TLR4 Results in Duodenal Adenoma and Colitis-Associated Neoplasia

Abstract

Background & Aims: Recently, the role of stromal cells such as inflammatory cells in tumor development has received much attention. Nuclear factor kappa B (NF-κB) is an important transcription factor in various biological processes and is involved in carcinogenesis. The exact mechanism how NF-κB activation contributes to inflammation-associated carcinogenesis is not clear.We conducted this study to investigate how colon cancer cells induced inflammatory response to link tumor growth. Methods: Mouse bone marrow macrophages (BMDMs) (wildtype, IKKβ-/-, TLR2-/-, TLR4-/and MyD88-/-), J774.1 and THP-1 cells were stimulated with the culture supernatant of several colon cancer cell lines. NF-κB activation was evaluated by EMSA, immunoblot of phosphorylated-IκBα and IκBα. Macrophage invasion assay were performed using chemotaxis chamber. In tumors of subcutaneously transplantation of the cells into nude mice, macrophage infiltration and IL-6 expression which is regulated NFκB activation were evaluated by immunostaining . Results: Six out of 10 (60%) of the supernatants prepared from colon cancer cells activated NF-κB in BMDMs and THP-1 cells (NF-κB activating colon cancer cells). This activation was observed in macrophages from wild-type and TLR4-/-, but not in TLR2-/-, MyD88-/and IKKβ-/-, suggesting that the activation is dependent on TLR2, MyD88 and IKKβ. Supernatant from NF-κB activating colon cancer cells also induces chemotaxis. In transplanted tumor tissue, macrophages accumulation and IL-6 expression were markedly increased in tumors of NF-κB activating colon cancer cells compared with non-activating ones. In addition, NF-κB activating colon cancer cells grewmore rapidly and aggressively than non-activating ones inmice. Surprisingly, NF-κB activating colon cancer cells had constitutive NF-κB activity. Conclusions: Colon cancer-derived certain factors induce accumulation of macrophages and activate NF-κB in macrophages through TLR2 and MyD88, eventually link tumor growth.