PI3K/AKT signaling is essential for\ud communication between tissue infiltrating mast\ud cells, macrophages, and epithelial cells in colitis-induced\ud cancer

摘要

Colorectal cancer is one of the leading cause of mortality in USA and worldwide.\udColon cancer is a complex world of connective tissue epithelial, inflammatory and\udendothelial cell interactions. It s long known that patients with persistent colitis\udare at high risk of developing colon cancer, where the patients passes through a\udphase from colitis to colitis induced dysplasia and finally invasive cancer. Though\uda lot of efforts have been poured into understanding the mechanisms underlying\udthe etiology of colon cancer, less has been known with respect to the changes\udhappening at genomic and proteomic levels in the inflammatory compartment of\udthe colon cancer with respect to interaction with the tumor epithelium and\udsubsequent tumor progression.\udIt is well known that the levels of PI3K/AKT and inflammatory cells mainly mast\udcells and macrophages are upregulated in the cancer. However, few efforts have\udbeen done to understand the pathogenesis in this direction, but they lacked in the\udcorrelative study of PI3K/AKT or immune infiltration in colon cancer or colitis and\udtheir spatial distribution with respect to cancer prognosis. Hence for the first time\udin this study a novel investigation was conducted where human patients were\udstudied in the various stages of inflammation associated colonic illness i.e. colitis\udto dysplasia and invasive cancer and compared it to normal amongst\udthemselves. The human-patient colonic tissue specimens were investigated for\udthe spatial distribution of mast cells, macrophages and pAKT in the histological\udareas of musoca and submucosa. It was observed that mast cells, macrophages\udand pAKT levels incrementally rise from colitis to dysplasia to cancer in the\udsubmucosal tissues. In mucosal tissue, pAKT levels were found atleast 10 fold\udhigher in the stromal cells in comparison with epithelial cells. The stromal and\udsubmucosal pAKT+ cells were found to be the macrophages that progressively\udinfiltrate from colitis to dysplasia and invasive cancer, also mast cells were found\udto be high in pAKT activity.\udTo investigate the role of PI3K/AKT in mast cells and macrophages biology and\ud4\udtheir crosstalk with colonic epithelium a pan PI3K/AKT inhibitor used in clinical\udtrials “LY2949002” was used. PI3K/AKT in mast cells was found to be critical for\udperipheral blood isolated human macrophage migration. LY294002 treatment of\udhuman and gut-derived murine mast cells restricted their ability to degranulate in\uddose-dependent manner. Moreover, inhibition of PI3K/AKT in human and mouse\udmast cells blocked the release of growth factors from them, and attenuated tumor\udproliferation and invasion promoting properties of mast cells. Also, PI3K/AKT\udinhibition in tumor infiltrating leukocytes isolated from colitis-associated patients\udlowered their soluble growth factor and cell-cell contact based tumor invasion\udpromoting properties.\udTreatment of LY294002 using intra-peritoneal injections lowered the incidence of\udcolitis associated invasive cancer development by day 56 in the Piroxicam\udtreated IL-10-/- mice. LY294002 displayed a striking effect on the epithelial\udproliferation, induced tumor apoptosis and attenuated the pAKT levels.\udLY294002 showed special predilection for the pAKT+ stromal cells in comparison\udwith pAKT+ epithelial cells. Moreover, frequencies of mast cells and granulocytebased\udinflammation were lowered after LY294002 treatment. Finally, the in situ\uddegraunulating potential of mast cells was attenuated by LY294002 treatment.\udIn conclusion, using in situ human patient specimen study, in vitro human and\udmurine assays and in vivo mouse model system this study confirms the role of\udPI3K/AKT pathway in mast cells and tumor infiltrating leukocytes in crosstalk with\udthe colonic epithelium and progression of colonic tissue from colitis.