Proliferative patterns of rectal mucosa as predictors of advanced colonic neoplasms in routinely processed rectal biopsies

Interleukin-1 Signaling Mediates Obesity-Promoted Elevations in Inflammatory Cytokines, Wnt Activation, and Epithelial Proliferation in the Mouse Colon

Obesity is a prominent risk factor for colorectal cancer (CRC). One mechanism by which obesity promotes the development of CRC is by generating a chronic, low-grade state of colonic inflammation. Interleukin-1β (IL-1β), a proinflammatory cytokine often elevated in obesity, is known to activate several procarcinogenic signaling pathways that are implicated in colonic carcinogenesis. We therefore sought to define the role of IL-1β in mediating some of the early biochemical and molecular events leading up to obesity-promoted CRC. Twenty-five wild-type (WT) C57BL/6J mice and 24 lacking a functional IL-1 receptor (IL1R^-/-) were each randomized to either low-fat or high-fat diets, resulting in lean and obese mice. Compared to WT lean controls, WT obese mice displayed 30%-80% greater concentrations of IL-1β and tumor necrosis factor-α (TNF-α) in the colonic mucosa (IL-1β: P = 0.04; TNF-α: P < 0.05), activation of the Wnt signaling cascade [evidenced by a 2-fold increase in colonic crypt cells displaying intranuclear β-catenin (P < 0.03)], and a significant expansion of the proliferation zone of the colonic crypt (P < 0.04). These obesity-induced alterations in colonic cytokines, Wnt signaling, and proliferation were absent in the obese IL1R^-/- mice. In the absence of IL-1 signaling, obesity-induced elevations of colonic IL-1β, TNF-α, Wnt activation, and enhanced epithelial proliferation no longer occur. These observations underscore the important mechanistic roles that IL-1 signaling appears to play in mediating the procancerous effects of obesity in the colon, thereby identifying a potential target for future strategies aimed at chemoprevention.

Subsite-specific differences of estrogen receptor beta expression in the normal colonic epithelium: implications for carcinogenesis and colorectal cancer epidemiology

OBJECTIVE

This study aimed at investigating whether a differential estrogen receptor beta (ER-beta) expression between the colonic subsites could correspond to a modification in proliferation, apoptosis, and adhesion of the normal colonocytes.

METHODS

ER-beta, Ki-67, Bcl-2, and E-cadherin expressions were investigated immunohistochemically, in normal epithelium biopsies from the ascending and the descending colon of 53 individuals, who underwent colonoscopy for the investigation of anemia and in whom no local pathology was identified.

RESULTS

ER-beta immunoreactivity has been shown to be stronger at the superficial epithelium than the crypts' base, the difference being important only for the ascending colon. In addition, ER-beta expression was higher in the superficial epithelium of the ascending colon than that of the descending colon. The variations of ER-beta expression did not correspond to the alterations in Ki-67, Bcl-2, and E-cadherin expression.

CONCLUSION

A subsite-specific variation of ER-beta expression has been shown in the normal colonic epithelium. This modulation of ER-beta might account for some well established specificities of colorectal cancer epidemiology like the right-sided predominance of the neoplasm in women and its gradual shift to more proximal sites over time.

Why do African Americans get more colon cancer than Native Africans?

The incidence of colorectal cancer (CRC) is dramatically higher in African Americans (AAs) than in Native Africans (NAs) (60:100,000 vs. <1:100,000) and slightly higher than in Caucasian Americans (CAs). To explore whether the difference could be explained by interactions between diet and colonic bacterial flora, we compared randomly selected samples of healthy 50- to 65-y-old AAs (n = 17) with NAs (n = 18) and CAs (n = 17). Diet was measured by 3-d recall, and colonic metabolism by breath hydrogen and methane responses to oral lactulose. Fecal samples were cultured for 7-alpha dehydroxylating bacteria and Lactobacillus plantarum. Colonoscopic mucosal biopsies were taken to measure proliferation rates. In comparison with NAs, AAs consumed more (P < 0.01) protein (94 +/- 9.3 vs. 58 +/- 4.1 g/d) and fat (114 +/- 11.2 vs. 38 +/- 3.0 g/d), meat, saturated fat, and cholesterol. However, they also consumed more (P < 0.05) calcium, vitamin A, and vitamin C, and fiber intake was the same. Breath hydrogen was higher (P < 0.0001) and methane lower in AAs, and fecal colony counts of 7-alpha dehydroxylating bacteria were higher and of Lactobacilli were lower. Colonic crypt cell proliferation rates were dramatically higher in AAs (21.8 +/- 1.1% vs. 3.2 +/- 0.8% labeling, P < 0.0001). In conclusion, the higher CRC risk and mucosal proliferation rates in AAs than in NAs were associated with higher dietary intakes of animal products and higher colonic populations of potentially toxic hydrogen and secondary bile-salt-producing bacteria. This supports our hypothesis that CRC risk is determined by interactions between the external (dietary) and internal (bacterial) environments.

Down-regulation of the tumor suppressor gene C-terminal Src kinase: An early event during premalignant colonic epithelial hyperproliferation

Hyperproliferation of the premalignant epithelium is critical for colonic carcinogenesis; however the mechanisms remain largely unexplored. We report herein that prior to occurrence of neoplastic lesions in the azoxymethane-rat model of colon carcinogenesis; the tumor suppressor gene C-terminal Src kinase (Csk) was down-regulated with a concomitant increase in Src activity. Furthermore, pharmacological or genetic (RNA interference) inhibition of Csk resulted in increased proliferation in colon cancer cell lines through the mitogen-activated protein kinase dependent pathway. Thus, we demonstrate, for the first time, that Csk suppression is an important early event in colorectal cancer pathogenesis.

Dietary pectin and calcium inhibit colonic proliferation in vivo by differing mechanisms

Diet plays an important role in promoting and/or preventing colon cancer; however, the effects of specific nutrients remain uncertain because of the difficulties in correlating epidemiological and basic observations. Transmissible murine colonic hyperplasia (TMCH) induced by Citrobacter rodentium, causes significant hyperproliferation and hyperplasia in the mouse distal colon and increases the risk of subsequent neoplasia. We have recently shown that TMCH is associated with an increased abundance of cellular beta-catenin and its nuclear translocation coupled with up-regulation of its downstream targets, c-myc and cyclin D1. In this study, we examined the effects of two putatively protective nutrients, calcium and soluble fibre pectin, on molecular events linked to proliferation in the colonic epithelium during TMCH. Dietary intervention incorporating changes in calcium [high (1.0%) and low (0.1%)] and alterations in fibre content (6% pectin and fibre-free) were compared with the standard AIN-93 diet (0.5% calcium, 5% cellulose), followed by histomorphometry and immunochemical assessment of potential oncogenes. Dietary interventions did not alter the time course of Citrobacter infection. Both 1.0% calcium and 6% pectin diet inhibited increases in proliferation and crypt length typically seen in TMCH. Neither the low calcium nor fibre-free diets had significant effect. Pectin diet blocked increases in cellular beta-catenin, cyclin D1 and c-myc levels associated with TMCH by 70%, whereas neither high nor low calcium diet had significant effect on these molecules. Diets supplemented with either calcium or pectin therefore, exert anti-proliferative effects in mouse distal colon involving different molecular pathways. TMCH is thus a diet-sensitive model for examining the effect of specific nutrients on molecular characteristics of the pre-neoplastic colonic epithelium.

Biomarkers of human colonic cell growth are influenced differently by a history of colonic neoplasia and the consumption of acarbose

The nutritional effects of butyrate on the colonic mucosa and studies of transformed cells suggest that butyrate has anti-colon cancer effects. If butyrate has antineoplastic effects, mucosal growth contrasts between normal subjects and those with a history of colonic neoplasia would parallel changes in growth characteristics caused by butyrate in a colon neoplasia population. To test this hypothesis, rectal biopsies from a survey of colonoscopy patients (n = 50) with and without a history of colonic neoplasia (controls) were compared. Similarly, rectal biopsies were compared from subjects (n = 44) with a colon neoplasia history in an acarbose-placebo crossover trial. Control subjects in the colonoscopy survey had higher bromodeoxyuridine (BrdU) uptake than subjects with a history of neoplasia (P = 0.05). The control subjects also had a higher correlation of BrdU and Ki-67 labeling (P = 0.003). Both findings were paralleled by acarbose use. Acarbose augmented BrdU uptake (P = 0.0001) and improved the correlation of BrdU and Ki-67 labeling (P = 0.013). Acarbose also augmented fecal butyrate (P = 0.0001), which was positively correlated with Ki-67 labeling (P = 0.003). p52 antigen had an earlier pattern of crypt distribution in subjects with a history of colon neoplasia but was not affected by acarbose use. Lewis-Y antigen was expressed earlier in the crypt with acarbose but had similar expression in the colonoscopy survey groups. The use of acarbose to enhance fecal butyrate concentration produced mucosal changes paralleling the findings in control subjects as opposed to those with neoplasia, supporting the concept of an antineoplastic role for butyrate.