Long‑term model of colitis‑associated colorectal cancer suggests tumor spread mechanism and nature of cancer stem cells

Abstract

Although chemical-induced animal models of colorectal cancer (CRC) suggest a lot about the disease, more efforts are required to establish metastasis models. Azoxymethane (AOM) and dextran sodium sulfate (DSS)-treated (AOM/DSS) Crl:CD-1 mice were sacrificed after 10 or 20 weeks in our previous study, and most colon tumors exhibited intramucosal adenocarcinomas. Our observations were extended until 30 weeks to study a colitis-associated advanced CRC mouse model, and explore whether linker threonine-phosphorylated Smad2/3 (pSmad2/3L-Thr) immunostaining-positive cells were involved in the progressive course of colitis-associated CRC as cancer stem cells. AOM/DSS mice were sacrificed at 10, 20 and 30 weeks after AOM administration. Following the histopathological analysis, immunohistochemical staining was performed for the following markers: CD34, podoplanin, β-catenin, E-cadherin, Ki67, Bmi1 and pSmad2/3L-Thr. Compared with AOM/DSS mice at 10 and 20 weeks, submucosal tumor infiltration and tumor invasion into vessels were markedly increased at 30 weeks. In the parts of colon tumors from AOM/DSS mice, particularly in mice at 30 weeks, the positive signal of E-cadherin was clearly reduced in the cell membranes. The percentage of Ki67-positive tumor cells in mucosal areas of AOM/DSS mice was higher than that in the sites of submucosal infiltration. In mucosal areas of colon tumors, pSmad2/3L-Thr-positive cells were scattered among tumor cells. At sites of submucosal infiltration and vessel invasion of these tumors, pSmad2/3L-Thr-positive cells were also observed among tumor cells. In colon tumors from AOM/DSS mice at 30 weeks, the percentage of pSmad2/3L-Thr-positive cells among the nuclear β-catenin-positive tumor cells was higher than that among the cytoplasmic β-catenin-positive tumor cells. For both non-neoplastic and neoplastic epithelial cells, pSmad2/3L-Thr-positive cells exhibited immunohistochemical co-localization with Bmi1. The present study developed an advanced CRC mouse model that exhibited tumor infiltration into the submucosa and invasion into vessels. The present study re-confirmed the theory that pSmad2/3L-Thr-positive cells may be cancer stem cells.

Roles of phosphatidylinositol-3-kinases signaling pathway in inflammation-related cancer: Impact of rs10889677 variant and buparlisib in colitis-associated cancer

“…No diffuse inflammation was observed in the colonic mucosal of CAC-induced mice, even though it was reported that signs of diffuse inflammation can appear as early as third to fourth weeks after treatment[ 42 ]. Furthermore, compared to a prior study, where submucosal tumor infiltrations were sporadically seen in 20%–24% of AOM-DSS mice at week ten, the percentage of CAC-induced mice with tumors in this study was considered high[ 43 ]. The selection of the mouse strain may have affected the percentage of tumor occurrence because different strains of mice have varying susceptibilities.…”

AOM/DSS Induced Colitis-Associated Colorectal Cancer in 14-Month-Old Female Balb/C and C57/Bl6 Mice—A Pilot Study

“…Despite these age-dependent changes, there are very few intervention studies on old mice. One recent study investigated the effect of the duration of tumor development post-tumor induction with AOM, where the mice were in the longest cohort at around 9-months-old at the time of sacrifice [14], which still only corresponds to ~35 years of age in humans [7], while the median age at diagnosis for colon cancer is 67 years [10].…”

Colonic expression of glutathione S-transferase alpha 4 and 4-hydroxynonenal adducts is correlated with the pathology of murine colitis-associated cancer

“…Cross sections were stained with hematoxylin and eosin (H & E) for pathological evaluation. Because AOM/DSS-induced murine CAC exhibits extensive pathological changes from focal inflammation to carcinomas in situ, occasionally, submucosal tumor infiltration depending on the mouse strain, dose of AOM/DSS, and duration of treatment [ 60 , 61 ], pathological changes was evaluated and scored based on the number of inflammatory cells, decrease in goblet cells, reactive atypia/dysplasia, and submucosal tumor infiltration (0, negative; 1, weak; 2, moderate; and 3, strong). These criteria represent major pathological changes for AOM/DSS-induced CAC.…”

“…While atypia represents benign cellular abnormalities, dysplasia describes neoplastic events [ 63 ]. Finally, submucosal tumor infiltration is often relevant to lymphatic metastasis [ 61 , 64 ].…”