Effect of indomethacin in autotransplanted colonic tumors

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.

Traditional serrated adenomas and serrated carcinomas in carcinogen-treated rats

AIMS

A recent review of archived sections from early experiments in rats showed neoplasias exhibiting serrated configurations. The aim was to assess the frequency of serrated neoplasias in the colon and small intestine of carcinogen-treated rats.

METHODS

While reviewing archival sections from early experiments in Sprague-Dawley (SD) and Fisher-344 (F-344) rats, we recently detected colonic and intestinal traditional serrated adenomas (displaying serrated or microtubular patterns) and serrated carcinomas. SD rats were injected 1,2-dimethylhydrazine (DMH) for 27 weeks whereas F-344 rats were fed with a pyrolysate (GLU-1) for 24 months. Filed sections from 358 colonic and small intestinal neoplasias were re-evaluated.

RESULTS

DMH-treated SD rats had 215 colonic neoplasias (1.4% were serrated adenomas, 7.9% microtubular adenomas, 2.8% serrated carcinomas and 2.8% microtubular carcinomas). GLU1-treated F-344 rats had 53 colonic neoplasias (1.9% were serrated adenomas and 20.8% microtubular adenomas), and 89 small intestinal neoplasias (1.1% were serrated adenomas, 42.7% microtubular adenomas and 6.7%, microtubular carcinomas).

CONCLUSIONS

DMH/SD-rats develop serrated and microtubular adenomas and carcinomas in the colon, whereas GLU1/F-344 rats develop microtubular adenomas in the colon and microtubular adenomas and carcinomas in the small intestine. The two rat-settings emerge as suitable models to study the molecular attributes of serrated and microtubular neoplasias under the standard conditions of the laboratory. This study is the first showing that a substantial number of serrated and particularly microtubular adenomas and carcinomas develop in the colon and small intestine of experimental rats. Importantly, serrated and microtubular neoplasias in rats recreate the histology of duodenal and colonic traditional serrated neoplasias in human beings.

Regular aspirin use and esophageal cancer risk

Given the high mortality rate and the rapidly increasing incidence rate of esophageal carcinoma, chemopreventive agents are highly desirable. Aspirin has been shown to be associated with reduced risk of developing colorectal carcinoma and other cancers. Even though previous studies have shown reduced risk of esophageal cancer associated with aspirin use, results were inconsistent with respect to frequency and duration of use. In this hospital-based case-control study, 163 esophageal cancer cases were compared to 482 age- and sex-matched hospital controls with nonneoplastic conditions. Participants were classified as regular aspirin users if they had taken the drug at least once a week for 6 months. Results suggest that esophageal cancer risk is significantly lower for regular aspirin users compared to nonusers [adjusted odds ratio (aOR) 0.54; 95% confidence interval (CI) 0.36-0.86]. Individuals who used an equivalent of at least 1 aspirin a day (> or =7 tablets/week) were half as likely to have been diagnosed with esophageal carcinoma (aOR 0.47; 95% CI 0.26-0.85), and a linear trend was noted with increasing frequency of use (p(trend) 0.007). Similar protective effects were noted with < or =20 years of use, whereas no risk reduction was noted with >20 years of use. Consistent reduction in risk associated with aspirin use was noted among both the major histological subtypes, but the protective effect appears to be more pronounced in adenocarcinoma compared to squamous cell carcinoma. Overall, results from the current study suggest that regular aspirin use may be associated with reduced risk of esophageal cancer.

Protective association of aspirin/NSAIDs and esophageal cancer: a systematic review and meta-analysis

BACKGROUND & AIMS

Esophageal carcinomas have high fatality rates, making chemoprevention agents desirable. We performed a systematic review with meta-analysis of observational studies evaluating the association of aspirin/nonsteroidal anti-inflammatory drug (NSAID) use and esophageal cancer.

METHODS

We evaluated the MEDLINE, BIOSIS, and Web of Science electronic databases (1980-2001); manually reviewed the literature; and consulted with experts. Studies were included if they: (1) evaluated exposure to NSAIDs, aspirin, or both; (2) evaluated esophageal cancer; and (3) reported relative risks or odds ratios or provided data for their calculation. Data were independently abstracted by 2 investigators. The primary and sensitivity analyses used both fixed and random-effects models.

RESULTS

Nine studies (2 cohort, 7 case control) containing 1813 cancer cases were identified. All primary summary estimates were homogeneous. Statistical pooling showed a protective association between any use of aspirin/NSAID and esophageal cancer (odds ratio [OR] = 0.57; 95% confidence interval [CI], 0.47-0.71). Both intermittent (OR = 0.82; CI, 0.67-0.99) and frequent medication use were protective (OR = 0.54; CI, 0.43-0.67), with greater protection with more frequent use. Stratified by medication type, aspirin use was protective (OR = 0.5; CI, 0.38-0.66), and NSAIDs had a borderline protective association (OR = 0.75; CI, 0.54-1.0). Any use was protective against both esophageal adenocarcinoma (OR = 0.67; CI, 0.51-0.87) and squamous cell carcinoma (OR = 0.58; CI, 0.43-0.78).

CONCLUSIONS

Pooled results support a protective association between aspirin and NSAIDs and esophageal cancer (of both histological types) and provide evidence for a dose effect. These findings support evaluating these agents in clinical trials of high-risk patients.

Mesalazine-induced apoptosis of colorectal cancer: on the verge of a new chemopreventive era?

BACKGROUND

It is an accepted fact that non-steroidal anti-inflammatory drugs (NSAIDs) are potent inhibitors of colorectal carcinogenesis. However, the major disadvantages of NSAIDs are gastrointestinal and renal toxicity. We conducted a prospective pilot study on the effects of the safe salicylic acid derivative, mesalazine, on apoptosis and proliferation of tumour cells and on normal tissue in colorectal cancer patients.

METHODS

Patients with colorectal cancer were asked to take mesalazine enemas for 14 days. Biopsies from malignant and normal tissue were taken prior to and after this treatment. Apoptosis was scored on haematoxylin/eosin-stained tissue sections, and cell proliferation was assessed by the proliferation marker Ki-67.

RESULTS

Ten out of 14 patients completed the study. The apoptotic score increased significantly in the tumour samples (pre-treatment 14.6 +/- 1.3 vs. post-treatment 19.4 +/- 0.8; P < 0.03). The apoptotic index in the normal mucosa was unchanged (pre-treatment 3.1 +/- 0.4 vs. post-treatment 2.9 +/- 0.3; N.S.). The cell proliferation in malignant tissue, according to the Ki-67 score, was hardly affected by mesalazine (pre-treatment 522 +/- 38 vs. post-treatment 493 +/- 39; N.S.). There was no effect on the Ki-67 index of normal mucosa (pre-treatment 24.2 +/- 2.0 vs. post-treatment 28.3 +/- 2.0; N.S.).

CONCLUSIONS

This pilot study conducted in patients with colorectal cancer clearly shows that mesalazine selectively induces apoptosis of tumour cells. On the basis of these findings, which need to be confirmed in larger studies, it may be speculated that 5-ASA could be useful in the chemoprevention of colorectal cancer.

Non-polypoid adenomas of the colon are associated with subjacent lymphoid nodules. An experimental study in rats

BACKGROUND

Subjacent lymphoid nodules (SLNs) have been found in 38% of non-polypoid colonic adenomas in humans. In the present work the presence of SLNs in experimentally induced colonic adenomas was investigated in rats.

METHODS

1,2-Dimethylhydrazine was injected subcutaneously in 290 Sprague-Dawley rats for 27 weeks.

RESULTS

An SLN was present in 28.6% of the 84 adenomas, in 8.4% of the 119 adenocarcinomas, and in 9.7% of the 31 small carcinomas without remnant adenomatous tissue. An SLN was found in 35.6% of the 59 non-polypoid neoplasias but only in 9.1% of the 175 polypoid (that is, exophytic) neoplasias. When only adenomas were considered, SLNs were present in 50.0% of the 34 non-polypoid adenomas but only in 14.0% of the 50 polypoid adenomas.

CONCLUSIONS

Non-polypoid colonic adenomas evolve preferentially from the minimal fraction of the colonic mucosa that overlays the few existing lymphoid nodules in rats.

Aspirin and gastrointestinal cancer

In rodents, nonsteroidal anti-inflammatory drugs (NSAIDs) including aspirin inhibit chemically induced adenomas and early carcinomas of the colon. The NSAID Sulindac inhibits the growth of polyps of the colon and rectum in two randomized trials of patients with familial adenomatous polyposis (FAP), although the inhibition is not complete. Eight epidemiologic studies have found a 40-50% reduction in polyps or colorectal cancer among persons who regularly use aspirin or other NSAIDs compared to those who do not. Two epidemiologic studies show a slight increase in risk. Interpretation of the epidemiologic studies is complicated, because bleeding induced by aspirin may enhance the diagnosis and early treatment of cancer, and at least in theory, the symptoms of cancer could cause patients to avoid aspirin. Clinical trials designed specifically to investigate the aspirin hypothesis in humans at high risk of colorectal polyps or cancer are needed to establish causality, and to define the optimal dose and drug. Experimental studies should further define the mechanism of tumor inhibition in animals.

NSAID use and decreased risk of gastrointestinal cancers

The accumulating evidence suggests that aspirin or other NSAIDs may prevent or inhibit the development of colon and perhaps other digestive tract cancers. Although the clinical, experimental, and epidemiologic evidence is promising, the hypothesis remains unproven except in the models of chemically induced colon cancer in rodents and adenomatous polyps in patients with FAP. Clinicians should await the results of randomized trials before using NSAIDs for cancer prevention or treatment. Recommendations are as follows: 1. Experimental studies should define the mechanism or mechanisms by which NSAIDs inhibit tumorigenesis in the rodent model. 2. Experimental and clinical studies should define the optimal drug, dosage, and treatment regimen. The new, selective COX-2 inhibitors should be studied for efficacy and toxicity. 3. Epidemiologic studies should continue to explore the issues of dosage, duration, drug, and toxicity. Because full-scale, randomized trials are feasible only for studying intermediate end points such as polyp recurrence or proliferative indices in high-risk populations, epidemiologic studies have an ongoing role. 4. Carefully designed randomized, clinical trials, now underway, are needed to test the efficacy of NSAIDs in inhibiting colorectal polyps or cancer in humans. 5. Better criteria are needed as to who should take aspirin and who should not.

The effects of sulindac on colorectal proliferation and apoptosis in familial adenomatous polyposis

BACKGROUND & AIMS

The mechanism by which sulindac causes regression of adenomas in patients with familial adenomatous polyposis (FAP) is unclear. Conflicting data on the drug's effects on colorectal epithelial proliferation have been reported. An alternative mechanism, and one not previously studied, is via induction of colorectal epithelial cell apoptosis (programmed cell death). This hypothesis was tested by studying the effects of sulindac on colorectal epithelial proliferation and apoptosis in patients with FAP.

METHODS

Cell proliferation was studied via immunohistochemistry for cell nuclear antigen in a group of 22 patients randomized to either sulindac (150 mg twice a day) or placebo in a previously published trial. The rectal epithelium from 7 additional patients with FAP treated with sulindac was examined by flow cytometry to assess changes in cell-cycle distribution and apoptosis.

RESULTS

Although sulindac caused a significant decrease in polyp size and number, there was no significant change in cytokinetic variables or cell cycle distribution 3 months after treatment. However, the subdiploid apoptotic fraction was increased significantly 3 months after treatment with sulindac (31.3% +/- 4.8% compared with 10% +/- 4.3% at baseline; P = 0.01).

CONCLUSIONS

Our findings suggest that sulindac does not affect colorectal epithelial proliferation and that its effects in patients with FAP may instead result from induction of apoptosis.

Flat adenoma-adenocarcinoma sequence in the colon of rats

PURPOSE

As there is an increased awareness of the existence of a "flat adenoma-adenocarcinoma sequence" in the colonic mucosa of human subjects, the aims of the study were to assess whether flat colonic adenocarcinomas in rats are also preceded by flat adenomas, as is reported in humans, and to determine the frequency of flat lesions compared with exophytic lesions in the colon of rats.

METHOD

The colonotropic carcinogen 1,2-dimethylhydrazine was injected subcutaneously in 300 Sprague-Dawley rats for 27 weeks.

RESULTS

A total of 358 tumors developed in 278 of the 300 rats. Of the 60 adenomas found at histology, 25 percent were flat adenomas. Of the 298 adenocarcinomas, 12.7 percent had originated in a flat adenoma. Of the 180 colonic neoplasias (adenomas or adenocarcinomas), 29.4 percent were flat neoplasias (flat adenomas or adenocarcinomas arising in a flat adenoma), and the remaining 70.6 percent were exophytic neoplasias (tubulo or villous adenomas or adenocarcinomas arising in exophytic adenomas). From the 298 colonic adenocarcinomas, 1 was a intramucosal adenocarcinoma, 87 were overt adenocarcinomas, and 90 were lymphoid-associated carcinomas; in those 298 adenocarcinomas, no preneoplastic lesion could be recorded. In 208 animals, biopsies were taken from macroscopically visible colonic lesions, and, in the remaining 70 animals, the entire colon was processed for histologic examination. Flat adenomas were found in 3.8 percent of the 208 biopsy specimens and in 10 percent of the 70 colectomy specimens. Further, of the 40 adenomas found in biopsy specimens, 20 percent were flat adenomas, and, of the 20 adenomas found in colectomy specimens, 35 percent were flat adenomas.

CONCLUSIONS

The study reported herein indicates the existence of a "flat adenoma-adenocarcinoma sequence" in the colonic mucosa of Sprague-Dawley rats. The flat lesions of the colon constituted approximately one-third of the total neoplastic lesions seen in the rat following injections of 1,2-dimethylhydrazine. More flat adenomas were detected at histologic examination of the entire colon than in biopsies obtained from the macroscopically visible colonic lesions. Consequently, flat adenomas may be overlooked by naked-eye examination.

Randomized controlled trial of the effect of sulindac on duodenal and rectal polyposis and cell proliferation in patients with familial adenomatous polyposis

Twenty-four patients with familial adenomatous polyposis who had previously undergone prophylactic colectomy and had advanced duodenal polyposis were entered into a randomized trial to assess the effect of the non-steroidal anti-inflammatory drug sulindac on duodenal and rectal polyps. Polyp size and number were assessed by videotaped duodenoscopy (and rectoscopy in 14 patients) at entry and after 6 months of treatment; the tapes were compared by two assessors who were unaware of the randomization and the shuffled chronological order of the recordings. Mucosal cell proliferation was measured by in vitro incorporation of 5-bromo-2'-deoxyuridine. Sulindac therapy was associated with a reduction in epithelial cell proliferation in the duodenum (median labelling index (LI) 15.8 versus 14.4 per cent, P = 0.003) and a trend towards duodenal polyp regression (P = 0.12). In the rectum, cell proliferation showed a marked reduction (median LI 8.5 versus 7.4 per cent, P = 0.018), and significant (P = 0.01) polyp regression was seen. Rectal polyposis was less severe than that in the duodenum and responded more dramatically. Sulindac is a possible treatment for patients in whom rectal polyps have failed to show significant regression after ileorectal anastomosis and who are unsuitable for pouch surgery; it may be useful in early duodenal polyposis or as an adjunct after duodenal clearance.

Quantification of acid mucins in the descending colon of rats having simultaneously growing colonic tumors

The acid mucins contained in goblet cells of the descending colon of 34 male Sprague-Dawley rats were histochemically labeled by Alcian blue pH 2.5 and quantified in an image analyzer (Cortex Controller). Twenty-two of these 34 rats were treated with 1,2-dimethylhydrazine (DMH) suspended in EDTA solution as a stabilizing agent and the remaining 12 rats with EDTA only. Of the 22 DMH-treated rats, 11 had concomitantly an adenocarcinoma elsewhere in the colon and the remaining 11 rats had no colonic tumors despite DMH treatment. The results indicated that Alcian blue-positive areas occupied 34.5% of the mucosa of the descending colon in tumor-bearing rats, and 35.2% in non-tumor-bearing DMH-treated rats. For EDTA-treated rats the percentage of mucosa occupied by Alcian blue-positive cells was 48.1%. The difference between DMH-treated rats (with or without tumors) and EDTA-treated rats was significant (p less than 0.001). These results suggest that the decrease of Alcian blue areas is related to the protracted treatment with DMH. Whether the decrease in acid mucins is induced by the carcinogen per se or whether it represents a true biochemical premalignant change at the cytoplasmic level remains to be elucidated.