glucagon-like-peptide-2 and Colorectal-Neoplasms

APC mutations drive human colorectal cancer (CRC) development. A major contributing factor is colonic stem cell (SC) overpopulation. But, the mechanism has not been fully identified. A possible mechanism is the dysregulation of neuroendocrine cell (NEC) maturation by APC mutations because SCs and NECs both reside together in the colonic crypt SC niche where SCs mature into NECs. So, we hypothesized that sequential inactivation of APC alleles in human colonic crypts leads to progressively delayed maturation of SCs into NECs and overpopulation of SCs. Accordingly, we used quantitative immunohistochemical mapping to measure indices and proportions of SCs and NECs in human colon tissues (normal, adenomatous, malignant), which have different APC-zygosity states. In normal crypts, many cells staining for the colonic SC marker ALDH1 co-stained for chromogranin-A (CGA) and other NEC markers. In contrast, in APC-mutant tissues from familial adenomatous polyposis (FAP) patients, the proportion of ALDH+ SCs progressively increased while NECs markedly decreased. To explain how these cell populations change in FAP tissues, we used mathematical modelling to identify kinetic mechanisms. Computational analyses indicated that APC mutations lead to: 1) decreased maturation of ALDH+ SCs into progenitor NECs (not progenitor NECs into mature NECs); 2) diminished feedback signaling by mature NECs. Biological experiments using human CRC cell lines to test model predictions showed that mature GLP-2R+ and SSTR1+ NECs produce, via their signaling peptides, opposing effects on rates of NEC maturation via feedback regulation of progenitor NECs. However, decrease in this feedback signaling wouldn't explain the delayed maturation because both progenitor and mature NECs are depleted in CRCs. So the mechanism for delayed maturation must explain how APC mutation causes the ALDH+ SCs to remain immature. Given that ALDH is a key component of the retinoic acid (RA) signaling pathway, that other components of the RA pathway are selectively expressed in ALDH+ SCs, and that exogenous RA ligands can induce ALDH+ cancer SCs to mature into NECs, RA signaling must be attenuated in ALDH+ SCs in CRC. Thus, attenuation of RA signaling explains why ALDH+ SCs remain immature in APC mutant tissues. Since APC mutation causes increased WNT signaling in FAP and we found that sequential inactivation of APC in FAP patient tissues leads to progressively delayed maturation of colonic ALDH+ SCs, the hypothesis

Topics: Adenomatous Polyposis Coli; Adult Stem Cells; Aldehyde Dehydrogenase 1 Family; Animals; Biomarkers; Cell Differentiation; Cell Line; Cell Line, Tumor; Cell Transformation, Neoplastic; Chromogranin A; Colon; Colorectal Neoplasms; Feedback, Physiological; Genes, APC; Glucagon-Like Peptide 2; Glucagon-Like Peptide-2 Receptor; HCT116 Cells; HT29 Cells; Humans; Mice; Models, Genetic; Mutation; Neuroendocrine Cells; Receptors, Somatostatin; Signal Transduction; Somatostatin; Stem Cell Niche; Tretinoin; Wnt Signaling Pathway

Glucagon like peptide-2 may play an important role in human colon cancer and polyp development because of its proliferative and antiapopitotic effects especially in colon. In this study, we investigated the role of human glucagon like peptide and it's receptor in development of human colorectal carcinogenesis.. The study includes 30 patients in colon cancer group and 20 patients in colonic polyp group who have been diagnosed by endoscopic and pathologic examination in Dokuz Eylül University, Department of Gastroenterology within 2 year-period. For comparison biopsies were taken from normal appearing colonic mucosa of the same patient. The cancer, polyp and normal colon mucosa samples were stained with glucagon like peptide receptor antibody by immunohistochemical method.. Glucagon like peptide 2 receptor positivity of colon cancer patients was 20 % (6/30) in focal cytoplasmic coloration while it was 0 % in colonic adenomas and 100 % in enteroendocrine cells of normal colonic mucosa. Statistically significant differences were found by the comparison of colonic polyp and normal colonic tissue (p=0.000), colonic cancer and normal colonic tissue (p=0.000) and colonic polyp and cancer tissues (p= 0.023).. Glucagon like peptide-2 receptor expression in colonic adenomas was not detected in human in contrary to the study on mice. Our study suggested that Glucagon like peptide-2 receptor expression is not a factor in adenoma-cancer pathogenesis. More studies are needed on this subject with more facts and different methods.

Topics: Adenocarcinoma; Adenoma; Adult; Aged; Aged, 80 and over; Colonic Polyps; Colorectal Neoplasms; Female; Glucagon-Like Peptide 2; Glucagon-Like Peptide-2 Receptor; Humans; Immunohistochemistry; Male; Middle Aged; Receptors, Glucagon