Genetic variation in SLC7A2 interacts with calcium and magnesium intakes in modulating the risk of colorectal polyps.

Solute carrier family 7, member 2 (SLC7A2) gene encodes a protein called cationic amino acid transporter 2, which mediates the transport of arginine, lysine and ornithine. l-Arginine is necessary for cancer development and progression, including an important role in colorectal cancer pathogenesis. Furthermore, previous studies found that both calcium and magnesium inhibit the transport of arginine. Thus, calcium, magnesium or calcium:magnesium intake ratio may interact with polymorphisms in the SLC7A2 gene in association with colorectal cancer. We conducted a two-phase case-control study within the Tennessee Colorectal Polyps Study. In the first phase, 23 tagging single-nucleotide polymorphisms in the SLC7A2 gene were included for 725 colorectal adenoma cases and 755 controls. In the second phase conducted in an independent set of 607 cases and 2113 controls, we replicated the significant findings in the first phase. We observed that rs2720574 significantly interacted with calcium:magnesium intake ratio in association with odds of adenoma, particularly multiple/advanced adenoma. In the combined analysis, among those with a calcium:magnesium intake ratio below 2.78, individuals who carried GC/CC genotypes demonstrated higher odds of adenoma [OR (95% CI):1.36 (1.11-1.68)] and multiple/advanced adenoma [OR (95% CI): 1.68 (1.28, 2.20)] than those who carried the GG genotype. The P values for interactions between calcium:magnesium intake ratio and rs2720574 were .002 for all adenomas and <.001 for multiple/advanced adenoma. Among those with the GG genotype, a high calcium:magnesium ratio was associated with increased odds of colorectal adenoma [OR (95% CI): 1.73 (1.27-2.36)] and advanced/multiple adenomas [1.62 (1.05-2.50)], whereas among those with the GC/CC genotypes, high calcium:magnesium ratio was related to reduced odds of colorectal adenoma [0.64 (0.42-0.99)] and advanced/multiple adenomas [0.55 (0.31-1.00)].

n-3 polyunsaturated fatty acids reverse the development of polyps in Apc(Min/+) transgenic mice.

Dietary n-3 polyunsaturated fatty acids (n-3 PUFAs) have been demonstrated to reduce tumor load in Apc(Min/+) mice, supporting a role for n-3 PUFAs in the inhibition of colon carcinogenesis and progression. The aim of the present study was to investigate whether a diet enriched with n-3 PUFAs, known already to have anti-neoplastic efficacy in Apc(Min/+) mice, would reverse the development of intestinal polyps. For this purpose, Apc(Min/+) mice were randomly divided into 3 groups of 5 animal each and fed as follows: control ST1 and ST2 groups, received a purified AIN-93M standard diet for 5 and 10 weeks, respectively; the OM-3R group received a purified AIN-93M standard diet for 5 weeks and a diet supplemented with salmon oil, rich in n-3 PUFAs, for another 5 weeks. After dietary treatment, in intestinal tissue, we evaluated the polyp number and volume, expression levels of cell proliferation- and apoptosis-related proteins, as well as the protein expression of LDL receptor and the levels of fatty acid synthase (FAS) activity. The results showed the ability of a diet enriched with n-3 PUFAs to suppress intestinal polyps in Apc(Min/+) mice, and to significantly reverse polyp development associated with the downregulation of cell proliferation markers and with the induction of estrogen receptor ß and LDL receptor, which are negative modulators of cellular proliferation. This noteworthy finding is important for a translational study evaluating the therapeutic role of n-3 PUFAs in the prevention and treatment of subjects with gastrointestinal diseases.

Body size, IGF and growth hormone polymorphisms, and colorectal adenomas and hyperplastic polyps.

OBJECTIVE: We examined the risk of colorectal polyps in relation to body size factors and candidate polymorphisms in selected genes of insulin-like growth factor (IGF1) (rs5742612), IGF1 receptor (IGF1R) (rs2229765), IGF binding protein 3 (IGFBP3) (rs2854746) and growth hormone (GH1) (rs2665802). DESIGN: Cases with colorectal adenomas (n=519), hyperplastic polyps (n=691), or both lesions (n=227), and controls (n=772), aged 20-74 years, were recruited from patients who underwent colonoscopy between December 2004 and September 2007 at a large integrated-health plan in Washington state. Subjects participated in a 45-minute telephone interview to ascertain body size and physical activity, and provided a buccal DNA sample for genetic analysis. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using multivariable polytomous regression. RESULTS: Compared to those of normal weight, higher body mass index (BMI) was associated with elevated risk of colorectal adenomas (OR=1.65, 95% CI 1.22-2.25 BMI>or=30 kg/m(2), p-trend=0.002) and both lesions (OR=2.15, 95% CI 1.43-3.22 BMI>or=30 kg/m(2), p-trend=0.003), but there was no relationship with hyperplastic polyps. Obesity at age 18 and a weight gain of >or=21 kg since age 18 were also significantly associated with an increased risk of colorectal adenomas and both lesions, but not hyperplastic polyps. There was a reduced risk of colorectal adenomas (OR=0.63, 95% CI 0.42-0.94) and hyperplastic polyps (OR=0.7, 95% CI 0.5-0.9) associated with the homozygous variant genotype for GH1. Few meaningful results were evident for the other polymorphisms. CONCLUSIONS: There is an increased risk of colorectal adenomas and presence of both adenomas and hyperplastic polyps in relation to increasing body size. Some genetic variation in GH1 might contribute to a reduced risk of colorectal adenomas and hyperplastic polyps.

Clock genes and cancer.

Period genes ( Per2, Per1) are essential circadian clock genes. They also function as negative growth regulators. Per2 mutant mice show de novo and radiation-induced epithelial hyperplasia, tumors, and an abnormal DNA damage response. Human tumors show Period gene mutations or decreased expression. Other murine clock gene mutations are not associated with a tumor prone phenotype. Shift work and nocturnal light exposure are associated with circadian clock disruption and with increased cancer risk. The mechanisms responsible for the connection between the circadian clock and cancer are not well defined. We propose that circadian disruption per se is not uniformly tumor promoting and the mechanisms for tumor promotion by specific circadian clock disturbances will differ dependent upon the genes and pathways involved. We propose that Period clock gene mutations promote tumorigenesis by unique molecular pathways. Per2 and Per1 modulate beta-catenin and cell proliferation in colon and non-colon cancer cells. Per2 mutation increases intestinal beta-catenin levels and colon polyp formation. Per2 mutation also increases Apc(Min/+)-mediated intestinal and colonic polyp formation. Intestinal tumorigenesis per se may also alter clock function as a result of increased beta-catenin destabilizing PER2 protein. Levels and circadian rhythm of PER2 in Apc(Min/+) mouse intestine are markedly decreased, and selective abnormalities in intestinal clock gene and clock-controlled gene expression are seen. We propose that tumor promotion by loss of PERIOD clock proteins is unique to these clock genes as a result of altered beta-catenin signaling and DNA damage response. PERIOD proteins may offer new targets for cancer prevention and control.

Genetic variability in prostaglandin synthesis, fish intake and risk of colorectal polyps.

Dietary polyunsaturated fatty acids (PUFAs) can be converted to prostaglandins and leukotrienes. Metabolism of omega-6 (n-6) PUFAs results in the production of pro-inflammatory mediators whereas downstream products of omega-3 (n-3) PUFAs have lower inflammatory activity. Elevated n-3 PUFA intake from dietary fish may be associated with lower risk of colorectal neoplasia among those with genetic variants resulting in higher levels of pro-inflammatory mediators. We investigated interactions between dietary fish intake and polymorphisms in cyclooxygenase (COX)-1, COX-2, ALOX5 and PGIS in a case-control study of adenomas (N = 522), hyperplastic polyps (N = 194) and polyp-free controls (N = 626). Polyp risk did not differ by fish intake. A suggested interaction with fish intake was observed for COX-1 P17L. Among those who were homozygous wild type, increasing fish intake was associated with a modestly reduced risk of adenoma, whereas among those with at least one variant allele, the reverse trend was observed (p-interaction = 0.08). The interaction was statistically significant when non-steroidal anti-inflammatory drug (NSAID) use was also taken into account: among those with COX-1 17PP genotypes, high fish intake and regular NSAID use was associated with a decreased risk compared with low fish intake and low NSAID use (odds ratio = 0.60, 95% confidence interval 0.33-1.09). The opposite association was observed among those with COX-1 17PL or LL genotypes (p-interaction = 0.04). Our results suggest that the effects of dietary n-3 PUFA intake and NSAID use may differ by genetic variation in COX-1.

A molecular/epidemiologic analysis of expression of cyclooxygenases 1 and 2, use of nonsteroidal antiinflammatory drugs, and risk of colorectal adenoma.

Nonsteroidal antiinflammatory drugs (NSAIDs) are postulated to protect against colorectal cancer and adenomas at least in part by a cyclooxygenase (COX-mediated mechanism. The results reported herein address the questions of what factors are associated with expression (relative messenger RNA levels) of COX-1 and COX-2 in colorectal adenomas and whether there is heterogeneity in the protective effect of NSAIDs by levels of COX expression. Paraffin-embedded tissue samples and data describing selected risk factors were obtained from cases enrolled in a case-control study of colorectal adenomatous polyps. RNA was isolated from paraffin-embedded specimens. Samples of complementary DNA were quantified using a fluorescence-based real-time detection method. We tested for differences in levels of COX expression among selected subgroups of cases using a standard Student t test. Odds ratios for the effects of NSAID variables were calculated using unconditional logistic regression in order to make use of all available data on COX expression. Results suggest that use of NSAIDs is associated with lower levels of COX-2 expression and that the protective effect of NSAIDs on polyp occurrence is stronger in the subgroup of cases with higher expression of COX-2 and a higher COX-2/COX-1 ratio. The results suggest that at least part of the protective effect of NSAIDs on the risk of colorectal adenoma involves a COX-mediated pathway.

Colon polyps and cancer.

The superiority of colonoscopy to double-contrast barium enema in detecting neoplasia was finally demonstrated in 2000, but colonoscopic surveillance programs are still based on short-term observations and are mostly inadequate, despite the prospective design of the trials. The evaluation of the diagnostic accuracy of virtual colonoscopy is in progress, but its appropriate place in clinical gastroenterology has not yet been defined. There is now solid evidence that screening with fecal occult blood testing (FOBT) not only reduces the mortality from colorectal cancer, but also that the incidence is substantially reduced after removal of the precursor lesions. Feasibility studies for population screening are ongoing. A once-only sigmoidoscopy will probably not be an optimal method of screening, but may be added to a program with FOBT. Molecular stool screening is attractive, but still experimental. Colonoscopy is not attractive as an initial screening instrument, despite its high diagnostic accuracy, and should only be used for screening high-risk individuals. Genetic methods are playing an increasing role in defining prognostic markers for intestinal neoplasia, and it is recommended that information services should be established for the public. Chemopreventive studies have revealed that dietary fiber supplementation may not reduce the risk of adenomas; the opposite seems to be true for aspirin and non-aspirin NSAIDs, which are active in the early phase of carcinogenesis. New techniques for optimizing diagnostic and therapeutic colonoscopy have been introduced.

Serum selenium and colonic neoplastic risk.

BACKGROUND: Selenium deficiency has been associated with cancer risk in several organs. This association was investigated in neoplasia of the colorectum. DESIGN: A case-control study is reported with two patient series, colorectal cancer and colorectal adenomatous polyps, and a control group found to be free of colorectal neoplasia. Diagnosis was determined by colonoscopy and histologic review of suspected neoplasms. Serum drawn at the time of colonoscopy was subsequently assayed for selenium content, and quartiles based on selenium were defined. Crude and adjusted odds ratios with 95 percent confidence intervals for adenoma related to selenium were calculated, controlling for known or suspected risk factors including gender, age, race, body mass index, family history, tobacco use, alcohol consumption, serum beta carotene, serum alpha tocopherol, and serum ferritin. RESULTS: There were 138 controls who had no neoplastic disease, 139 adenoma patients, and 25 cancer patients. For adenoma, comparing higher quartiles of selenium to the first (lowest selenium), the adjusted odds ratio for the second quartile was 1.7 (95 percent confidence interval, 0.8-3.7), the third quartile was 1.4 (0.7-3.2), and the fourth (highest selenium) quartile was 1.8 (0.9-4). The odds ratios for cancer patients were 0.8 for the second quartile, 1 for the third quartile, and 1.7 for the fourth quartile. CONCLUSION: No trend could be detected toward a protective effect of higher levels of serum selenium for colonic benign or malignant tumors.

[A case of a probable "cancer family syndrome" presenting four synchronous malignancies of the colon].

A 72-year-old male was admitted because of right lower quadrant pain, Barium enema and total colonoscopy disclosed multiple colon cancers and sequentially, a subtotal colectomy was performed. The resected specimen demonstrated 3 advanced carcinomas and an adenomatous cancer with additional multiple polyps. Investigation of his family history revealed that his mother and his elder sister had died of uterine cancer, and that his elder brother, his nephew, and his niece had been operated on for colorectal cancer. We thus supposed a case of "Cancer Family Syndrome" presenting multiple neoplasms of the colon.

Generalized juvenile polyposis coli. Clinical management based on long-term observations.

Generalized juvenile polyposis occurred in five patients (age range, 18 months to 16 years). Clinical findings included abdominal pain, weakness, rectal bleeding, diarrhea, rectal prolapse, intussusception, clubbing, and failure to thrive. Laboratory findings included anemia, hypoalbuminemia, hypokalemia, and skin test anergy. Diagnosis is achieved by double contrast enema, endoscopy, and biopsy. Unlike patients with solitary juvenile polyps, patients with generalized involvement require surgical intervention. Subtotal colectomy and ileoproctostomy are the procedures of choice, and we performed them in four cases. An ileoanal-endorectal pull-through procedure was required in one patient with continued rectal disease. All five patients are currently alive and well. Long-term follow-up is important as polyps may persist into adult life. Family members are at risk for developing gastrointestinal tract tumors and should be screened.

Radiological features of familial polyposis coli: grouping by polyp profusion.

The radiological features of familial polyposis coli (FPC) were studied in 60 patients by double-contrast barium enema examinations. When classified by profusion of polyps, cases fell into two groups: the profuse type and the sparse type. The radiologically determined boundary range distinguishing these types was 6-9 polyps/cm2 in adult patients and 3-6 in children. But on grouping the FPC patients by size of the polyps, one group of 34 cases had one or more polyps of more than 1 cm diameter, and in 16 of this group, one or more advanced cancers were histologically demonstrated; whereas in the group of 20 patients, in which the lesions were 5 mm or less, no malignancy was detected. In contrast to cases of the sparse type, in which the size of the polyps bore no relation to age, all cases of the profuse type who were 15 years old or more had polyps more than 1 cm in diameter.

Colonic polyp patterns in familial polyposis.

The diagnosis of familial polyposis depends on there being more than 100 adenomatous polyps in the large bowel. The polyps are the result of intramucosal microadenomatous growth. The age at which this occurs varies, and in the early stages of polyp development relatively few larger polyps may be seen. The numbers and size of the polyps as seen on double-contrast barium enema were compared with the macroscopic findings on the resected specimens in 27 patients with proven polyposis. Of these patients, 23 (83%) were diagnosed when polyps were first found at sigmoidoscopy. Radiologically the predominant polyp size was more than 5 mm in only four cases, 2-5 mm in 22 (81%), and less than 2 mm in one. Of the 22 with predominately 2-5 mm polyps, eight had significant numbers of nodules smaller than 2 mm and three had considerable numbers of polyps larger than 5 mm. Eleven (41%) were thought to have fewer than 70 polyps. Pathologically the nodular pattern (less than 2 mm) predominated in 11 (41%) and 14 had polyps of 2-5 mm. More than 100 polyps were present in each case, with fewer than 500 polyps in eight. In the 11 patients thought radiologically to have fewer than 70 polyps, the nodular pattern predominated in nine. In the initial stages of polyp growth, the larger polyps are less numerous, and the background nodular pattern is a useful diagnostic feature of familial polyposis.

Computerized radiology of the colon: a potential screening technique.

We report here a new technique, computerized radiology of the colon. This technique consists of digital radiography of the colon combined with colon CT utilizing only air as a contrast agent. This technique is capable of detection of very small polyps. It is also useful in the study of diverticulitis of the colon. Comparison between CT and radiographic air contrast barium enema is demonstrated. In one case, a 13-yr-old girl who underwent total colectomy for familial polyposis, the surgical pathologic findings are also shown. Future potential of the technique is discussed including use as a mass screening method.