Gut-associated lymphoid tissue and dimethylhydrazine-induced colorectal carcinoma in the Wistar/Furth rat

Colonic Lymphoid Follicle Hyperplasia after Gastrectomy in Rats

Nodular lymphoid hyperplasia (NLH) of the human colon has been associated with multiple diseases and symptoms. Causes include food allergies, infections, inflammatory bowel disease, and immunodeficiency, and gastrectomy is not usually considered to be the etiology. Nine rats two weeks after total gastrectomy and 12 control rats were sacrificed and submitted for histological examination. In the gastrectomy group, we found lymphoid hyperplasia throughout the entire colon mucosa. The cross-sectional area of lymphoid follicles was increased to be five-fold larger than that in the rats in the control group (sham surgery). Lymphoid follicles were classified into primary and secondary follicles according to the presence/absence of germinal centers; the gastrectomy group had a significantly larger number of secondary follicles. When T cell and B cell classification of lymphocytes was performed, there was no difference between gastrectomy and control groups at T:B = 40:60. When the lymphoid follicles were classified, the proportion of T lymphocytes increased in the secondary follicle (T:B = 40:60) compared with in the primary follicle (T:B = 20:80). Gastrectomy significantly activated lymphocytic intestinal immunity by altering the intestinal environment, causing colonic NLH. Gastrectomy in rats is a good animal model for the study of NLH in colorectal diseases.

The third pathway of colorectal carcinogenesis

Aims

The majority of the colorectal carcinomas (CRC) arise in a vast mucosal area built with columnar cells and mucus-producing goblet cells. These carcinomas evolve via the conventional (tubular/villous) adenoma–carcinoma pathway, or the serrated adenoma–carcinoma pathway. Much less frequently CRC arise in the gut-associated lymphoid tissue (GALT) mucosal domain via the third pathway of colorectal carcinogenesis.

Methods

All publications on human colorectal GALT carcinomas in the literature were reviewed.

Results

Only 23 GALT-carcinomas found in 20 patients are in record. The GALT carcinomas were detected at surveillance colonoscopic biopsy in 11 patients (four had ulcerative colitis, two were members of a Lynch syndrome family, two of a CRC family, one had familial adenomatous polyposis (FAP), one prior colon adenomas and one a submucosal tumour), or at diagnostic colonoscopic biopsy in the remaining nine patients (three had rectal bleedings, two abdominal pains, one diverticular disease and one protracted constipation. In three, no ground disease or symptoms were provided). In six of the 23 GALT carcinomas, the luminal surface showed tumour cells, ulcerations or no descriptions were given. Ten (66.7%) of the remaining 15 GALT carcinomas showed on top, adenomas (n=8) or high-grade dysplasia (n=2).

Conclusions

The low frequency of GALT carcinomas might be explained by the fact that the colorectal mucosal areas occupied by GALT domains are minute. The finding that two-thirds of the 15 remaining GALT carcinomas (vide supra) were covered by high-grade dysplasia or by conventional adenomas strongly suggest that conventional non-invasive neoplasias might have preceded the majority of the GALT carcinomas in record.

Corrupted colonic crypt fission in carcinogen-treated rats

Background

The colonic crypts in rats reproduce themselves by symmetric fission at the base of the crypts, and proceeding upwards, generate two separate identical crypts. Recently we reported corrupted colonic crypt fission (CCCF) in rats with colonic carcinoma. Here we investigated whether CCCF also occurred in the colonic mucosa without carcinoma in carcinogen-treated rats.

Methods

Filed Swiss-roll sections from 35 male rats (25 treated with 1,2-dimethyhydrazine (DMH) suspended in EDTA solution, and 10 EDTA-treated) were reviewed. CCCF were regarded those with either asymmetric basal fission, asymmetric lateral sprouting/lateral fission, basal dilatations, or spatial aberrations of the normal (vertical) axis.

Results

202 CCCF (38%) were recorded amongst 533 crypts with fission in DMH-treated rats, and only one CCCF (0.1%) was found amongst 571 crypts with fission in EDTA-treated rats (p<0.05). The basal aspect of four adenomas included in Swiss roll sections exhibited CCCF lined either with indigenous (non-dysplastic) epithelium or with dysplastic epithelium.

Conclusion

It was demonstrated that CCCF without dysplasia develop in carcinogen-treated SD rats. As judged by the figures presented, the possibility that the epithelium in those corrupted crypts was successively replaced by top-down growing dysplastic cells, could not be totally rejected. This is the first report showing that non-dysplastic CCCF may antedate the very early stages of colonic carcinogenesis in SD rats.

Chemopreventive effects of nonsteroidal anti-inflammatory drugs on 1,2-dimethylhydrazine-induced colon carcinogenesis in rats

ABSTRACT The anticancer efficacy of two different classes of NSAIDs, the nonspecific cyclooxygenase (COX) inhibitor aspirin and the specific COX-2 inhibitor celecoxib, was examined at their therapeutic anti-inflammatory doses during 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis in a rat model. Eight to 10-week-old male rats of Sprague strain were divided into four groups. While group 1 served as control and received the vehicle of the drugs, groups 2, 3, and 4 were administered freshly prepared DMH in 1 mM EDTA saline (pH 7.0) (30 mg/kg body weight/week, subcutaneously). Groups 3 and 4 were also given a daily treatment of aspirin (60 mg/kg body weight, orally) and celecoxib (6 mg/kg body weight, orally), respectively, both prepared in carboxy-methyl cellulose. Animals were sacrificed at the end of 12 weeks and colons from different groups were subjected to macroscopic and histopathological studies, enzymatic activities of superoxide dismutase (SOD) and catalase (CAT), and determination of lipid peroxide level. The maximum number of raised mucosal lesions in proximal, middle, and distal regions of the colon was found in the DMH group alone, and the lowest number was found in the celecoxib-treated DMH group. Histological studies also showed the highest occurrence of dysplastic aberrant crypt foci (ACF) associated with enlarged lymphoid follicles in all the three portions of colon (i.e., proximal, middle, and distal). The aspirin-administered DMH group had lesser ACF in the proximal and middle portions and no ACF in the distal region. The celecoxib-administered DMH group showed no ACF in the middle region of the rat colon. DMH treatment induced lipid peroxidation and inhibited the activities of SOD and CAT. Both the aspirin- and celecoxib-treated DMH groups showed a marked lowering of the lipid peroxide level along with a significant enhancement of CAT activity when compared with the DMH-treated group. The results show that celecoxib was found to be more effective in reducing the ACF occurrence and aggregates of lymphoid tissue than the nonselective COX inhibitor aspirin, and suggests a possible chemoprevention modality in colon cancer. This may have important implications as COX-2 selective drugs at anti-inflammatory doses are better tolerated clinically than standard NSAIDs, thus making them potentially better chemopreventive agents in colon cancer.

Normal structure, function, and histology of mucosa-associated lymphoid tissue

The mucosa-associated lymphoid tissue (MALT) initiates immune responses to specific antigens encountered along all mucosal surfaces. MALT inductive sites are secondary immune tissues where antigen sampling occurs and immune responses are initiated. Effector sites, present as diffuse lymphoid tissue along all mucosal surfaces are the sites of IgA transport across the mucosal epithelium. Though there are many differences between inductive sites in various organs, they all contain the same basic compartments-follicles, interfollicular regions, subepithelial dome regions, and follicle-associated epithelium. The morphologic differences between MALT and other secondary lymphoid tissues, between the MALT sites of differing anatomic locations, and species differences among laboratory animals are described. The morphologic changes in MALT associated with aging, route of nutrition, and genetic mutation (i.e., the nude and SCID mutations) are also discussed. MALT tissues comprise the mucosal immune system which can function independently of the systemic immune system and are, therefore, an important and often overlooked aspect of immunopathology.

Inhibition of tumor progression and neoangiogenesis using cyclic RGD-peptides in a chemically induced colon carcinoma in rats

Integrins are cell surface molecules that mediate cell adhesion, but are also important regulators of tumor cell interactions with their microenvironment, tumor cell survival and growth. In addition, the alpha(v)beta3-integrins appear to be critical for microvessel formation in tumor-induced neoangiogenesis. The present study is the first to investigate the effects of therapeutic alpha(v)beta3-integrin inhibition in a chemically induced tumor model that largely resembles human colon carcinomas. Tumor induction was performed in 47 male Sprague-Dawley rats using 1,2 dimethylhydrazin (21 mg/kg) twice a week. After 20 weeks of tumor induction, 100% of the animals developed adenocarcinomas with a median of 13.5 macroscopic tumor nodules (range 12-17), but no distant metastases. During further tumor induction for an additional 10 weeks, rats were treated three times/week with (a) 15 mg/kg RGDfV-peptide that can block vitronectin and fibronectin receptors; (b) an equimolar amount of an ineffective cyclic control peptide; or (c) with equimolar amounts of a linear RGDS-peptide. At the end of this treatment period, rats were sacrificed, and tumor load was quantified macroscopically and confirmed by histological examination. For investigation of the involvement of tumor-induced neoangiogenesis microvessel, density was determined using CD31-immunostaining. After 30 weeks, control animals (group B) had 5-18 tumors (median 14.5). If rats were treated with RGDfV-peptide (group A), the number of tumor nodules was significantly reduced (P < 0.005) to a median of seven macroscopic tumors (range 2-10 tumors), which also represented a significant reduction (P < 0.005) compared with prior to treatment. Application of noncylic RGDS-peptides (group C) did not affect the number of tumor nodules (median 18; range 10-30 tumors). The diameters of tumor nodules were comparable (3.2-6.1 mm) in animals of all groups. In addition, microvessel density was significantly (P < 0.05) reduced in tumors in group A compared to control rats. The major side effect in the treatment group was increased susceptibility to respiratory infections. Our results demonstrate that alpha(v)beta3-integrin-receptor inhibition appears to be a therapeutic strategy for colorectal cancer. In our therapeutic model, late onset of treatment with integrin-blocking peptides resulted in an inhibition of tumor growth and a reduced tumor load which appeared to be mediated, at least in part, by inhibition of neoangiogenesis.

LOCALIZAÇÃO DE LESÕES TUMORAIS INDUZIDAS PELA 1,2-DIMETILHIDRAZINA E SEU GRAU DE ATIPIA NO COLON DE RATOS

As diversas técnicas para o tratamento cirúrgico da Síndrome do Intestino Curto apresentam, ainda hoje, problemas de difícil resolução. De todas, as mais promissoras são o transplante de intestino delgado e o transplante de colo. Uma técnica intermediária que mostrou resultados controversos tanto clínicos como experimentais, é a interposição de segmentos de colo no trajeto do intestino delgado após extensas ressecções. Sua aplicação serve, todavia, como um meio de se estudar a adaptação do colo, inclusive visando os transplantes. Neste trabalho foi estudada a indução de tumores pela 1,2-dimetilhidrazina, sua localização e grau de atipia nos diferentes segmentos intestinais após ressecção de 80% do jejuno-íleo. Foram encontradas 24 lesões ao exame macroscópico após a décima sexta semana de pós-operatório. O número de lesões por animal variou de 0 a 9. Das 24 lesões encontradas, 20 estavam no colo (83,33%), sendo que 11 estavam localizadas no cólon proximal, 3 no cólon distal e 6 anorretais. No estudo histológico, a maioria das lesões era de grau III. Este trabalho mostrou que o método de indução de tumores pela 1,2-dimetilhidrazina é apropriado para o estudo de tumores intestinais em ratos.

Induction of small intestinal adenocarcinomas in Wistar rats administered amsacrine

Amsacrine is an aminoacridine that binds to DNA by intercalation. Because amsacrine interferes with DNA synthesis it has potent genotoxic and cytotoxic properties. To define its tumorigenic nature, amsacrine was studied in a 104-week carcinogenicity bioassay using Wistar rats. Treatment regimen consisted of 6 cycles of intravenous administration over 5 consecutive days followed by 23 days without drug to allow for recovery from cytotoxicity. Doses were 0.25, 1 and 3 mg/kg. At 3 mg/kg mortality was excessive reaching 100% of males by Week 90 and 96% of females at Week 104. Deaths were associated with either tumor induction or cytotoxicity. Multisystemic tumor development manifested in a dose-related fashion. The incidence of small intestinal adenocarcinomas was particularly striking owing to the rarity of these neoplasia in Wistar rats. Small intestinal adenocarcinomas that were well-differentiated presented as pedunculated masses or were sessile masses derived from flat mucosa. Mucin-secreting adenocarcinomas showed poorly-differentiated histologic pattern with absence of crypt or villus structures. We postulate that they are variants of the neoplasia derived from flat mucosa wherein the loss of histologic architecture is the sequela of protracted secretion and accumulation of mucin leading ultimately to extensive tumor remodeling. As amsacrine is primarily excreted in bile, direct exposure to this genotoxic agent was a probable factor in tumorigenesis like small intestinal carcinogens such as 1,2-dimethylhydrazine and azoxymethane.

Photo detection of carcinoma of the colon in a rat model: a pilot study

Photodynamic sensitizers are light-absorbing chemicals that cause photoreactions in biologic systems when exposed to light of the proper wave-length. Dihematoporphyrin ethers (DHE) are the active porphyrin derivatives most commonly used as a photosensitizer (Photofrin, QLT). DHE accumulates in tumor tissue and also fluoresces when light activated. A more reliable and less costly screening method for early detection and treatment of colon cancer is needed. The present study was designed to induce adenocarcinoma of the colon in rats with 1,2 dimethylhydrazine (DMH) and attempt to identify tumors early in their evolution by DHE fluorescence. Forty rats were injected with 20 mg/kg of DMH at weekly intervals until sacrifice. Photofrin (3 mg/kg) was injected through the tail vein in each prior to sacrifice. Eight colonic specimens contained invasive adenocarcinoma, seven of which fluoresced when exposed to a Woods lamp. Carcinoma in situ was identified in two specimens by fluorescence, and one fluorescent specimen contained dysplasia.

Effect of gut-associated lymphoid tissue on cellular proliferation in proximal and distal colon of the rat

In previous studies, chemically induced colonic carcinomas were found to originate preferentially from crypts adjacent to lymphoid tissue. Proliferative parameters and mucosecretion were analyzed in proximal and distal rat colon in relation to the proximity of lymphoid patches. Animals received an intraperitoneal pulse of bromodeoxyuridine 1-hr before death. In both proximal and distal colon, crypts located at the immediate proximity of the lymphoid formations contained fewer mucous cells (P less than 0.001), but a higher percentage of proliferative epithelial cells (P less than 0.001) than the crypts far from lymphoid formations. The labeling index was higher in crypts adjacent to lymphoid patches compared to crypts distant from lymphoid patches only in the lower third of the crypts. The association of an increased proliferative activity and a decrease in differentiated mucosecreting cells in colonic crypts adjacent to lymphoid patches could be related to the particular sensitivity of these crypts cells to the effects of mutagens and carcinogens.

Ultrastructural and cytoarchitectural features of lymphoreticular organs in the colon and rectum of adult BALB/c mice

The structure and function of colonic mucosal lymphoid organs remain largely unexplored, especially in the rectum hidden within the pelvic vault. Two-month-old female BALB/c mice were anesthetized, and the entire colon was removed from cecum to anus. Distal colonic patches were then prepared for electron microscopy or were quick-frozen and sectioned for immunoperoxidase localization of B cells and T cell subsets. Aggregated lymphoid follicles were distributed irregularly along the entire colon with an average of 1.4 patches per centimeter of colon length. There were large collections of follicles opposite the ileocecal valve (cecal patches), variable numbers of patches throughout the colon, and at least one patch within 10 mm of the anus (rectal patch). Follicles were adjacent to branching crypts lined by epithelium infiltrated by lymphoid cells and containing few goblet cells. In electron micrographs, M cells were identified by their short, irregular microvilli; intraepithelial lymphoid cells; reduced lysosomal dense bodies; and an expanded tubulovesicular network. Small germinal centers were seen. Cytoarchitectural components of colonic lymphoid follicles and Peyer's patch follicles were remarkably similar, despite differences in surrounding mucosa and luminal microbial exposure. The presence of organized lymphoid tissue with M cells and germinal centers suggests that transepithelial particle transport and antigen recognition can take place in the rectum. Whether such tissue has the capacity for uptake of luminal microorganisms is of particular interest, not only because colonic follicles may be sites for local initiation of immune responses but also because they may be important entry points for systemic infection.

Gut-associated lymphoid tissue and 1,2-dimethylhydrazine intestinal tumors in the rat: an histological and immunoenzymatic study

The association between chemically-induced intestinal carcinoma and gut lymphoid patches was studied in 20 male Sprague-Dawley rats 7 months after the first of 16 weekly injections of 1,2 dimethylhydrazine (DMH). The lymphoid patches of DMH-treated rats and of 14 untreated control animals were systematically studied histologically on sections of "swiss-rolled" whole intestine. It was found that 78% of the small-intestine carcinomas and 73% of the colorectal carcinomas were associated with intestinal lymphoid patches. Furthermore, misplaced and often atypical glandular crypts were often found in the parafollicular or interfollicular areas of lymphoid patches, in treated as well as in control animals. These glands could be the origin of the lymphoid-patch-associated carcinoma. Immunohistological staining with monoclonal antibodies (MAbs) against T-lymphocyte antigens or anti-IgM serum labelling B lymphocytes clearly localized early carcinoma and atypical glands in the T-dependent, interfollicular and parafollicular area of lymphoid follicles. An MAb directed against la-antigen stained some well-differentiated carcinomas and some atypical glands found in control rats. On the other hand, lymphoid patches, when not invaded by a carcinoma, were not modified in their number, size, morphology or cellular composition in DMH-treated rats as compared to control animals.

Monitoring the histogenesis of colonic tumors in the Sprague-Dawley rat

A total of 306 male Sprague-Dawley rats, injected with dimethylhydrazine (DMH), dose 21 mg/kg body weight s.c., were investigated. Of the 109 rats receiving the dose once only, seven colonic adenocarcinomas developed; all seven (100%) were seen to originate in discrete lymphoid patches. Of the 97 rats treated with one dose/week for 3 months, only 6% of the 50 adenocarcinomas developed in discrete lymphoid patches, while 46% were seen to originate in a pre-existing adenoma. Of the remaining 100 rats, receiving one dose/week for 6 months, only 3.5% of the 57 adenocarcinomas arose from discrete lymphoid patches; 43.9% arose from a pre-existing adenoma. Thus, the histogenesis of adenocarcinomas at our laboratory appears to be dose-dependent. Experiments are therefore being designed to monitor in detail the events of these two histogenetically different adenocarcinomas in the colonic mucosa in our animal model.