Su1868 Constant Stimulation of Epithelial Cell Death in the Steady-State Gut Is Controlled via CFLIP

was estimated pathologically using human colorectal cancer tissues. We used HCT116, a cultured cell line derived from human colon cancer tissue: p53-wild type HCT116p53+/+, p53-knockout HCT116p53-/-. Furthermore, we established p53-suppressed cell line using p53 shRNA (HCT116sh p53) compared with HCT116sh control. To elucidate the effect of fibroblast existence on tumor growth, in in vivo study, HCT116p53+/+, HCT116p53-/-, HCT116sh control and HCT116sh p53 were implanted subcutaneously into nude mice, with or without WI-38, a human fibroblast cell line, and the volume of implanted subcutaneous tumors were determined. In in vitro study, the gene expression signature of HCT116 cells co-cultured directly or through transwell filters with or without WI-38 was determined. Immunohistochemistry study of human colon cancer tissues revealed the significant positive relationship among p53 dysfunction, fibroblast agglomeration, and micro vessel density. Xenograft tumors of p53-dysfunctional cells (HCT116p53-/or HCT116sh p53) implanted with WI-38 cells grew up larger than tumors of p53-functional cells (HCT116p53+/ + or HCT116sh control) with or without WI-38 cells, and p53 dysfunctional cells without WI38 cells. In in vitro, no significant increase in proliferation of p53-normal or p53-functionaldeficient HCT116 cells co-cultured with WI-38, directly or through transwell, was detected compared without WI-38. WI-38 co-cultured with p53 dysfunctional cells secreted more VEGF than the one with p53 normal cells, indicating that p53 dysfunctional cancer cells induced alteration of angiogenic characteristics from fibroblasts to CAFs. VEGF deletion in WI-38, not cancer cells, reduced xenograft tumor size of p53 dysfunctional cells implanted with WI-38. These results demonstrated that VEGF produced by fibroblasts, not epithelial cancer cells, has a crucial role in p53-functional-deficient tumor growth. The present study indicates that p53-incompetent tumor cells educate fibroblasts to secrete VEGF, leading to tumor progression. This is the novel insight in that gene alteration of epithelial cancer cells triggers the transformation of tumor microenvironment.