Establishment and characterization of a novel cell line and xenotransplant mouse model derived from feline colorectal adenocarcinoma

Colorectal adenocarcinoma is an aggressive malignant tumor in cats that frequently metastasizes to the lymph nodes and/or distant organs. However, research on feline colorectal adenocarcinoma is limited, and experimental models have not been established. A novel cell line, FeLeco-G7, was established from the lymph node of a 12-year-old spayed female Maine Coon cat with metastatic colorectal adenocarcinoma. FeLeco-G7 cells were polygonal with abundant cytoplasm and adherent growth. The population-doubling time was approximately 28.3 hours, and the mean number of chromosomes was 37.6±0.1 per cell (ranging between 32 and 41). Consistent with the original tumor, FeLeco-G7 cells were immunopositive for cytokeratin (CK) 20 and CDX2, and immunonegative for CD10 and CK7. Nuclear accumulation of β-catenin was rarely observed. Mutation analysis suggested TP53 gene alterations. A subcutaneous injection of FeLeco-G7 cells into immunodeficient mice resulted in the formation of a mass at the injection site without the development of metastatic lesions. An orthotopic (intrarectal) transplantation of FeLeco-G7 cells caused cachexia and diffuse involvement of the rectal mucosa in one of the 3 mice and the formation of masses around the rectum in the other 2 mice. Metastases to the regional lymph nodes and lungs were detected in three of the 3 and one of the 3 mice, respectively. The histological findings and immunohistochemical features of these masses were similar to those of the original tumor. These results suggest that FeLeco-G7 cells and the orthotopically transplanted mouse model are valuable tools for further molecular and therapeutic research on feline colorectal adenocarcinoma.

Transcriptomic analysis reveals immune infiltration status and potential biomarkers of canine colorectal cancer

Colorectal cancer (CRC) in dogs has been shown to have similar molecular characteristics to human colorectal cancer. Although researchers have explored the pathogenesis and immune status of human CRC, the canine CRC has been far less studied. As a result, we analyzed canine colorectal tumors and normal canine intestinal samples by Gene Set Enrichment Analysis (GSEA) and found significant enrichment of immune-related pathways, including the TNF-α signaling pathway and IL6-STAT3 signaling pathway. In addition, the differential infiltration of naive B cells and regulatory T cells suggested that canine CRC was in a state of immunosuppression. Weighted gene co-expression network analysis (WGCNA) revealed the gene modules that contribute to differences in regulatory T cell inetfiltration, Further cross-validation of canine and human CRC differential genes obtained three core genes that are both species-conserved and differentially expressed, CD44, NAT10, and ETV4, of which NAT10 and ETV4 have been little studied in the immune status of colorectal cancer. Our findings may have implications for the pathogenesis and progression of CRC in dogs and could be a new potential therapeutic target for CMT and provide a bioinformatics foundation for later clinical experiment validation.

Assessment of colorectal anastomosis perfusion with confocal laser endomicroscopy − an experimental study

Introduction: Early diagnosis of complicated healing of colorectal anastomosis can increase the chance for salvage surgery and thus reduce overall morbidity. Confocal laser endomicroscopy (CLE) enables in vivo assessment of tissue perfusion without disturbing its integrity. This experimental study evaluates the potential of CLE for postoperative monitoring of colorectal anastomosis. Methods: A hand-sewn colorectal anastomosis was performed in 9 pigs. The animals were subsequently divided into groups with normal (N=3) and ischemic anastomosis (N=6). Microscopic signs of hypoperfusion were evaluated postoperatively at regular intervals using CLE. Results: Uneven saturation of the images was evident in the group with ischemic anastomosis. The epithelium had inhomogeneous edges and more numerous crypt branching was visible. Tissue oedema quantified as the number of crypts per visual field was already more extensive at the first measurement after induction of ischemia. There was also a significant difference between the values measured before and 10 minutes after ischemia – 8.7±1.9 vs. 6.0±1.1 (p=0.013). Conclusion: Postoperative monitoring of the colorectal anastomosis using CLE enables prompt detection of perfusion disorders.

Activities of matrix metalloproteinase-2, matrix metalloproteinase-9, and serine proteases in samples of the colorectal mucosa of Miniature Dachshunds with inflammatory colorectal polyps

OBJECTIVE

To investigate the activities of gelatinases (matrix metalloproteinase [MMP]-2 and MMP-9) and serine proteases in the colorectal mucosa of Miniature Dachshunds (MDs) with inflammatory colorectal polyps (ICRPs).

ANIMALS

15 MDs with ICRPs and 5 dogs with non-ICRP-related large bowel diarrhea (controls).

PROCEDURES

Zymographic methods were used to evaluate the activities of MMP-2, MMP-9, latent forms of MMP-2 and MMP-9 (pro-MMP-2 and pro-MMP-9), and serine proteases in inflamed and noninflamed tissue samples from MDs with ICRPs and in noninflamed tissue samples from control dogs. The associations of serine protease activities with MMP-2 or MMP-9 activity were also analyzed.

RESULTS

Activities of pro-MMP-2 and pro-MMP-9 were detected in most tissue samples, regardless of the tissue type, whereas activities of MMP-2 and MMP-9 were not detected in control tissue samples. In the inflamed tissue samples from MDs with ICRPs, the activities of MMP-2, pro-MMP-9, and MMP-9 were significantly higher than those in the noninflamed tissue samples from those dogs. Serine protease activities were significantly higher in the inflamed and noninflamed tissue samples from MDs with ICRP, compared with findings for control tissue samples. A weak correlation was detected between serine protease activities and MMP-9 activity.

CONCLUSIONS AND CLINICAL RELEVANCE

Study results suggested that gelatinase and serine protease activities are upregulated in the colorectal mucosa of MDs with ICRPs, possibly contributing to the pathogenesis of this disease through the functions of these enzymes in degradation of extracellular matrix and promotion of inflammatory cell migration and inflammatory responses.

cGAMP inhibits tumor growth in colorectal cancer metastasis through the STING/STAT3 axis in a zebrafish xenograft model

The leading cause of mortality due to colorectal cancer (CRC) is highly associated with the development of liver metastases. Recently, we described cGAMP that is closely related to the metastatic state wherein the progress of metastatic tumors is associated with favorable outcomes in a zebrafish xenograft model. cGAMP was administered and the expression levels of type-I interferons were induced amongst tumor tissues to illuminate the overall measure of the induced STING/STAT3 axis in colorectal liver metastases. Furthermore, cGAMP-STING dependent STAT3 activation resulted in the inhibition of tumor cell proliferation, viability, and invasion in vitro. The subtotal reduction in tumor growth attributed to a large number of infiltrating inflammatory cells in vivo. We showed that cGAMP inhibited migration through angiogenesis by up-regulating IL-2, TNF-α, and IFN-γ, whereas STAT3 down-regulation inhibited CXCL8, BCL-2, and VEGFA expression. The importance of cGAMP in inhibiting the invasion front of CRC confirmed that the cGAMP dependent activation of STING/STAT3 axis played a key role in the inhibition of tumor progression.

Frequent alteration of the tumor suppressor gene APC in sporadic canine colorectal tumors

Sporadic canine colorectal cancers (CRCs) should make excellent models for studying the corresponding human cancers. To molecularly characterize canine CRC, we investigated exonic sequence mutations of adenomatous polyposis coli (APC), the best known tumor suppressor gene of human CRC, in 23 sporadic canine colorectal tumors, including 8 adenomas and 15 adenocarcinomas, via exon-resequencing analysis. As a comparison, we also performed the same sequencing analysis on 10 other genes, either located at human 5q22 (the same locus as APC) or 18q21 (also frequently altered in human CRC), or known to play a role in human carcinogenesis. We noted that APC was the most significantly mutated gene in both canine adenomas and adenocarcinomas among the 11 genes examined. Significantly, we detected large deletions of ≥10 bases, many clustered near the mutation cluster region, as well as single or two base deletions in ∼70% canine tumors of both subtypes. These observations indicate that like in the human, APC is also frequently altered in sporadic colorectal tumors in the dog and its alteration is an early event in canine colorectal tumorigenesis. Our study provides further evidence demonstrating the molecular similarity in pathogenesis between sporadic human and canine CRCs. This work, along with our previous copy number abnormality study, supports that sporadic canine CRCs are valid models of human CRCs at the molecular level.

Single-dose safety and pharmacokinetic evaluation of fluorocoxib A: pilot study of novel cyclooxygenase-2-targeted optical imaging agent in a canine model

We evaluated preclinical single-dose safety, pharmacokinetic properties, and specific uptake of the new optical imaging agent fluorocoxib A in dogs. Fluorocoxib A, N-[(5-carboxy-X-rhodaminyl)but-4-yl]-2-[1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indol-3-yl]acetamide, selectively binds and inhibits the cyclooxygenase-2 (COX-2) enzyme, which is overexpressed in many cancers. Safety pilot studies were performed in research dogs following intravenous (i.v.) administration of 0.1 and 1  mg/kg fluorocoxib A. Blood and urine samples collected three days after administration of each dose of fluorocoxib A revealed no evidence of toxicity, and no clinically relevant adverse events were noted on physical examination of exposed dogs over that time period. Pharmacokinetic parameters were assessed in additional research dogs from plasma collected at several time points after i.v. administration of fluorocoxib A using high-performance liquid chromatography analysis. The pharmacokinetic studies using 1  mg/kg showed a peak of fluorocoxib A (92±28  ng/ml) in plasma collected at 0.5 h. Tumor specific uptake of fluorocoxib A was demonstrated using a dog diagnosed with colorectal cancer expressing COX-2. Our data support the safe single-dose administration and in vivo efficacy of fluorocoxib A, suggesting a high potential for successful translation to clinical use as an imaging agent for improved tumor detection in humans.

E-cadherin and β-catenin expression in canine colorectal adenocarcinoma

E-cadherin and its associated cytoplasmic proteins, including β-catenin, have been examined as potential oncogenic markers due to the significant correlation between tumour dedifferentiation and the invasive capacity of epithelial tumours. The purpose of this study was to evaluate the expression of E-cadherin and β-catenin in canine colorectal cancer using immunohistochemistry and to examine the relationship between this expression and various clinicopathological variables. The expression pattern of E-cadherin and β-catenin was investigated in 44 colorectal canine carcinomas. In the intestinal mucosa of noncancerous areas, epithelial cells demonstrated equally strong membranous expression of E-cadherin and β-catenin localised to the cell-cell junctions. Reduced expression of E-cadherin and β-catenin was demonstrated in 75% and 81.8% of the colorectal carcinoma cases, respectively. The down-regulation of both E-cadherin and β-catenin was correlated with decreased differentiation and increased tumour grade. In addition, the expression of β-catenin was correlated with tumour size. These results suggest that dysfunction of the E-cadherin-catenin complex starts in the early stages of carcinogenesis and that the disruption of the tissue architecture is progressively associated with the invasion of the tumour.

Rectovaginal fistula following colectomy with an end-to-end anastomosis stapler for a colorectal adenocarcinoma

An 11-year-old, female neutered Labrador retriever was presented with a micro-invasive differentiated papillar adenocarcinoma at the colorectal junction. A colorectal end-to-end anastomosis stapler device was used to perform resection and anastomosis using a transanal technique. A rectovaginal fistula was diagnosed two days later. An exploratory laparotomy was conducted and the fistula was identified and closed. Early dehiscence of the colon was also suspected and another colorectal anastomosis was performed using a manual technique. Comparison to a conventional manual technique of intestinal surgery showed that the use of an automatic staple device was quicker and easier. To the authors' knowledge, this is the first report of a rectovaginal fistula occurring after end-to-end anastomosis stapler colorectal resection-anastomosis in the dog. To minimise the risk of this potential complication associated with the limited surgical visibility, adequate tissue retraction and inspection of the anastomosis site are essential.

Colorectal Plasmacytomas: A Retrospective Study of Nine Dogs

Nine cases of colorectal plasmacytomas diagnosed between 1998 and 2001 were reviewed. Treatment consisted of complete surgical resection when possible. Two dogs had multiple plasmacytomas. Two dogs had local recurrence of the tumor at 5 and 8 months after resection. Two dogs were alive at 20 and 23 months with no recurrences at the time of follow-up. The median survival time was 15 months (range 5 to 33 months). Colorectal plasmacytomas are similar to mucocutaneous plasmacytomas, in that they tend to progress slowly and do not recur with complete excision.

Effects of HIV-1 Nef, a cytotoxic viral protein, on the growth of primary colorectal cancer

Colorectal cancer is the third leading cause of cancer deaths in American men and women. We describe the cytotoxic use of HIV-1 Nef protein and a cytotoxic peptide identified within the HIV-1 Nef structure in targeting human cancer cells in vitro and in vivo in a human xenograft model. A human colorectal tumor was implanted and propagated in the subcutaneous tissue of SCID mice. The mice were injected biweekly with the Nef apoptotic peptide. The tumor treated with Nef peptide underwent significant growth inhibition by as much as 300 percent when compared to the control (untreated) tumors. The Nef peptides were found to have an apoptotic effect on the human colon tumor similar to the effect seen on CD4 cells when the viral protein is secreted by the HIV-1 virus infected cells. The evidence from the xenograft mouse model suggests that the Nef peptides can be used to inhibit human colorectal cancer growth.

Antitumor effect of MCC-465, pegylated liposomal doxorubicin tagged with newly developed monoclonal antibody GAH, in colorectal cancer xenografts

MCC-465 is an immunoliposome-encapsulated doxorubicin. The liposome is tagged with polyethylene glycol and the F(ab')2 of a monoclonal antibody named GAH, a human antibody obtained by the hybridoma technique. The epitope recognized by GAH is not well characterized, but human gastric, colorectal, and mammary cancer cells were GAH-positive, while the normal counterparts were GAH-negative. Pegylated liposome doxorubicin (PLD) and MCC-465 did not show significant antitumor activity against GAH-negative Caco-2 xenografts. On the other hand, MCC-465 exhibited significantly superior antitumor effects against GAH-positive WiDr-Tc and SW837 xenografts, compared with PLD. Immunohistochemistry with GAH revealed that 94% (100 of 106) of surgical specimens of colorectal cancer were GAH-positive. These results warrant a phase I clinical trial of MCC-465 for patients with metastatic colorectal cancer.

Cyclooxygenase-2 selective inhibition with NS-398 suppresses proliferation and invasiveness and delays liver metastasis in colorectal cancer

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been reported to reduce the risk and mortality of colorectal cancer (CRC) by inhibiting the activity of cyclooxygenase (COX). The present studies were directed to determine whether selective COX-2 inhibition reduces CRC tumour cell proliferation and invasion/migration, and the possible cellular and molecular mechanisms involved. The MC-26 cells are a highly invasive mouse CRC cell line expressing COX-2 protein. NS-398 (100 μM), a highly selective COX-2 inhibitor, decreased cell proliferation by ∼35% of control, as determined using [³H]-thymidine incorporation. This reduction in cell proliferation was associated with decreased expression of cyclin D1 and proliferating cell nuclear antigen (PCNA). Furthermore, NS-398 inhibited cell invasion/migration through Matrigel extracellular matrix components at 24 h by ∼60%. The addition of exogenous prostaglandin E₂ partially attenuated the inhibition of cell invasion by 10 μM NS-398, but failed to reverse the effect of 100 μM NS-398. Matrix metalloproteinases-2 (MMP-2) and -9 (MMP-9) are two enzymes that facilitate cell invasion/migration by degrading the extracellular matrix. In the presence of 100 μM NS-398, Western blot hybridisation analysis and zymography demonstrated that both MMP-2 and MMP-9 protein levels and enzyme activity were decreased by ∼25–30%. In separate studies, NS-398 also inhibited tumour growth in vivo and retarded the formation of liver metastasis. The results of these studies indicate that the expression and activity of COX-2 appear to be associated with both the proliferative and invasive properties of CRC. Cyclooxygenase-2 inhibition suppresses tumour cell growth and invasion/migration, and retards liver metastasis in a mouse colon cancer model, via multiple cellular and molecular mechanisms.

High susceptibility of nullizygous p53 knockout mice to colorectal tumor induction by 1,2-dimethylhydrazine

PURPOSE

The susceptibility of male p53 nullizygote (-/-), heterozygote (+/-), and wild-type (+/+) mice to 1,2-dimethylhydrazine (DMH) induction of colon carcinogenesis was investigated.

METHODS

In a preliminary short-term experiment, male mice of three genotypes were given s.c. of 20 mg/kg DMH once weekly for 5 weeks. In a medium-term experiment, mice were given weekly s.c. of DMH for 15 weeks. In a long-term experiment, male p53 (+/-) and (+/+) mice were given weekly injections of DMH for 15 weeks, and killed at week 30.

RESULTS

In the medium-term experiment, carcinomas were observed in 70% of p53 (-/-) mice, although there were no carcinomas in p53 (+/+) and (+/-) mice. In the long-term experiment, there was no significant difference in incidences of adenomas and carcinomas between p53 (+/+) and (+/-) mice. PCR-single strand conformation polymorphism analysis of exons 5-8 of p53 gene revealed four mutations in one focal atypia, one adenoma, and two carcinomas, out of 56 colonic proliferative lesions in the medium- and long-term experiments.

CONCLUSIONS

These results suggest that p53 might not be a direct target of DMH but complete loss of p53 might elevate susceptibility to DMH-induced colorectal carcinogenesis.

Cyclooxygenase-2 expression in spontaneous intestinal neoplasia of domestic dogs

Cyclooxygenase-2 (Cox-2) is commonly upregulated during human colorectal tumorigenesis, and its contribution to this process has been clearly demonstrated in genetic mouse models. The only other species that naturally develops intestinal cancer with any frequency is the domestic dog. Intestinal carcinogenesis in humans has been strongly linked to environmental factors such as diet, which may be shared by household pets. We have previously reported that beta-catenin is overexpressed in the neoplastic epithelium of canine colorectal polyps, as it is in humans and rodents. We now show that Cox-2 is also upregulated in the majority of these lesions. Thirteen out of 20 colorectal adenomas (65%) contained immunohistochemically detectable Cox-2 protein restricted to the nonneoplastic tumor stroma, including myofibroblasts and a-smooth muscle actin-negative mesenchymal cells morphologically consistent with macrophages and/or fibroblasts. In contrast to benign polyps, seven of 15 adenocarcinomas (47%) also expressed Cox-2 in the neoplastic epithelium. These changes duplicate molecular changes in human intestinal tumorigenesis and substantiate a fundamental role for both beta-catenin and Cox-2 in intestinal neoplasia.

Evidence for Msh2 haploinsufficiency in mice revealed by MNU-induced sister-chromatid exchange analysis

The role of Msh2 in chromosome stability has been investigated in a targeted mouse model for HNPCC, Msh2Delta7N. Chromosome aberration frequencies were similar in bone marrow of Msh2(+/+), Msh2(+/-)and Msh2(-/-)mice and no differential effects of in vivo X-irradiation were noted. By contrast, the induction of sister-chromatid exchanges (SCEs) by methyl nitrosourea (MNU) was reduced in Msh2(-/-)and Msh2(+/-)cells to approximately 20% and approximately 45% wild-type levels respectively indicating a phenotypic effect of haploinsufficiency of the mouse Msh2 gene.

Dysregulation of beta-catenin is common in canine sporadic colorectal tumors

Human colorectal tumorigenesis is often initiated by APC (adenomatous polyposis coli) or beta-catenin (CTNNB1) mutations, which result in dysregulation of beta-catenin expression, followed by alterations in E-cadherin and/or p53. We examined 32 canine intestinal tumors for expression and intracellular distribution of beta-catenin, E-cadherin, and p53 using immunohistochemistry. beta-Catenin in normal mucosal epithelial cells was restricted to lateral cell membranes, but 13/13 (100%) colorectal adenomas had intense cytoplasmic and/or nuclear reactivity. Three of six (50%) colorectal carcinomas, 2/13 (15%) small intestinal carcinomas, and dysplastic cells in 1/2 focal hyperplastic lesions in the small intestine had a similar pattern of staining; remaining tumors had normal membranous beta-catenin reactivity. There was a correlation (P = 0.007) between abnormal beta-catenin and E-cadherin staining with 11/13 (85%) colorectal adenomas, 3/6 (50%) colorectal carcinomas, and 3/13 (23%) small intestinal carcinomas showing decreased membranous reactivity compared with normal mucosal epithelium. E-cadherin staining was reduced more often in adenomas than in carcinomas (P = 0.04). There were two patterns of nuclear p53 staining: > 60% of nuclei in 2/26 (8%) carcinomas (one colorectal, one small intestinal) were strongly labeled, whereas three colorectal adenomas and one small intestinal carcinoma had fainter staining in 10-20% of cells. Dysregulation of beta-catenin appears to be as important in canine colorectal tumorigenesis as it is in the human disease and could be due to analogous mutations. Malignant progression in canine intestinal tumors does not appear to be dependent on loss of E-cadherin or beta-catenin expression or strongly associated with overexpression of nuclear CMI antibody-reactivity p53.

Immunological determination of faecal haemoglobin concentrations in dogs

Faecal haemoglobin (Hb) concentrations in apparently healthy experimental Beagle dogs and in dogs of various breeds kept in private households or at breeders were measured by reversed passive latex agglutination (RPLA) and enzyme-linked immunosorbent assay (ELISA) in an effort to define the physiological concentrations of faecal Hb in the dog. In 88% (53) of 60 experimental Beagle dogs (30 males and 30 females), the RPLA titres were 1:2 and 1:8 and the faecal Hb concentrations ranged from 40.0 to 431.5 (mean 184.1 +/- 92.6) micrograms/g faeces by ELISA. No significant difference was found in Hb levels or RPLA titres between males and females. Seven dogs (12%) had significantly greater RPLA titres and Hb concentrations by ELISA than the remaining dogs. In 84% (45) of the 53 dogs kept in private households or at breeders, the RPLA titres were < 1:1 to 1:8 and the faecal Hb concentrations ranged from 7.1 to 456.7 (mean 137.5 +/- 128.7) micrograms/g faeces in ELISA. Eight of these dogs (15.1% of 53 dogs) had significantly greater RPLA titres and Hb concentrations by ELISA than the remaining dogs. There were no significant differences between the Beagles and dogs kept in private households or at breeders. In conclusion, in 98 (86.7% of 113) dogs the physiological concentrations of RPLA titres were < 1:1 to 1:8 and the faecal Hb concentrations were 143.5-185.1 micrograms/g (95% confidence level). Approximately 13.3% of apparently healthy dogs had higher faecal Hb concentrations, suggesting the presence of subclinical haemorrhages. Four dogs suffering from colorectal cancer also had high faecal Hb concentrations.

Immunohistochemical detection of p53 tumor suppressor gene protein in canine epithelial colorectal tumors

Eighty canine epithelial colorectal tumors obtained by excisional biopsy were evaluated immunohistochemically for p53 tumor suppressor gene protein. Dogs in the study average 6.9 years of age (range, 1-12.5 years). A standard avidin-biotin immunohistochemical protocol incorporated a polyclonal antibody of rabbit origin (CM-1) as the primary antibody. Positive staining was observed within all subcategories of lesions, including hyperplastic polyps 1/2 (50%), adenomas 14/29 (48%), carcinomas in situ 9/22 (41%), adenocarcinomas 3/4 (75%), and invasive carcinomas 8/23 (35%). A total of 35/80 (44%) positive tumors wee identified. Fifteen of 31 (48%) benign tumors labeled for p53 protein compared to 20/49 (41%) malignant tumors. Survival data was available for 57/80 (71%) dogs. The average age of dogs within the group with survival data was 4.4 years. Males predominated 34/57 (60%). Mean survival time was 20.6 months. There was no significant difference in survival time between dogs grouped according to p53 immunoreactivity, cellular stain location, or tumor site. A statistically significant increase in survival time was observed between dogs with clean surgical margins and those without (P < 0.018) and for dogs with adenomas or carcinomas in situ over dogs with invasive carcinomas (P < 0.02). In this study, the overall greater positive staining frequency of benign lesions compared to malignant lesions is contrary to data derived from similar immunohistochemical analyses of human tumors and is incongruous with the theorized late-stage participation of the p53 protein in the development of human colorectal cancers. The results of this study suggest that if the p53 tumor suppressor gene protein is involved in the progression of canine colorectal tumors, it may play a relatively early role, possibly analogous to the early appearance of p53 overexpression in precancerous lesions of human ulcerative colitis. Immunohistochemical detection of p53 was not useful prognostically.

Adenomatous polyps and carcinoma in situ of the canine colon and rectum: 34 cases (1982-1994)

The medical records of 34 dogs (median age, eight years) with colorectal mucosal lesions were reviewed. Hematochezia was the most common (82%) presenting sign. Most dogs (79%) presented with solitary masses located in the rectum. After histological review, 12 masses were classified as adenomatous polyps and 22 as carcinoma in situ. Recurrence of clinical signs were common (41%), and malignant transformation of the tumor was documented in 18% of the cases. A higher recurrence rate and malignant transformation occurred in dogs presented with multiple masses or diffuse disease and in dogs initially diagnosed with carcinoma in situ.

Interspecies comparative pathology of colorectal neoplasms: relevance for treatment

Comparative pathology may serve as a practical tool for therapy by comparison of normal and abnormal structures of the digestive tract in animals and men. A better understanding of colon cancer as the most common solid neoplasm after lung cancer in the industrialized world is sought. In the so-called developed nations and in animals colon cancer is less frequent. The pathogenesis of colon cancer involves environmental and genetic factors. Several types of colorectal cancer can be discerned and the species distribution ranges from invertebrates to man. Colorectal neoplastic progression is species-specific. An intraspecies-specific comparison of large bowel cancer is also valuable. Alteration of signal transduction pathways and somatic mutations of oncogenes are described, as well as the occurrence, research and current treatment. Metastasis of neoplasms of the colon and of the rectum can be studied by intraspecies-specific comparison. Sections of this review deal with vitamin D and cancer and close with present therapies for colorectal cancer.