Colon cancer is induced by a single low dose of azoxymethane in fasted-refed rats

Is Sunflower Cooking Oil Beneficial for Colorectal Cancer? In Vivo Studies on Azoxymethane-induced Colon Cancer in Rats

Background:

The incorporation of oils in the diet may have promoting or inhibitory effects on Colorectal Cancer (CRC). In this study, azoxymethane (AOM) was used to mimic CRC in rats, and the effect of sunflower oil on cancer progression in the colon of the rats was tested.

Objective:

This study was conducted to investigate the effect of sunflower oil on preneoplastic cancer properties of the colonic mucosal surface of tumors and the aberrant crypt foci (ACF).

Methods:

Six-week-old Sprague-Dawley male rats were randomized into 4 groups of 6 rats each, namely naïve, positive control, negative control, and sunflower oil-fed. CRC was induced by AOM by subcutaneous injection of 20 mg/kg. After CRC induction, the rats were given the respective treatment of either basal diet (naïve group), 10 mg/kg indomethacin (positive control), 0.9 % saline (negative control), or 7 % sunflower oil (experimental group) daily by oral gavage for 42 days. Rats were sacrificed by cervical dislocation; colon samples were visually observed for any tumors on the colonic mucosal surface and evaluated for ACF; histopathological examinations were also performed.

Results:

The mean body weights of the rats were similar in all groups as per one-way ANOVA. A total of 3 ACF were found in the negative group, while none were observed in other groups. The crypts appeared regular with circular luminal openings and were closely packed together in the naïve group. Crypts in the positive and treated group had a similar appearance to the naïve group.

Conclusion:

Sunflower oil inhibition of the preneoplastic cancer ACF properties were tested but were found to be insignificant when administered during CRC treatment or management. However, long-term experiments with a greater number of days will yield better development of tumor and ACF development and will be useful in identifying the molecular mechanism.

Enhanced growth of colorectal aberrant crypt foci in fasted/refed rats involves changes in TGFbeta1 and p21CIP expressions

We previously demonstrated that fasting/refeeding enhances the initiation phase of liver and colorectal carcinogenesis in rats. The present study was undertaken to establish whether cycles of fasting/refeeding carried out during the promotion phase of carcinogenesis may also affect the formation of aberrant crypt foci (ACF), preneoplastic lesions induced in the colon by azoxymethane (AOM). We were also interested in studying whether this effect might be mediated by changes in the proliferation, apoptosis or expression of TGFbeta1 and p21CIP genes in the colon. 44 male Fisher 344 rats were given a single dose of AOM (20 mg/kg s.c.) and one week later, they were exposed to 5 cycles of 4 days fasting followed by 7-10 days of refeeding (refed rats); controls were regularly fed; the rats were killed 2, 8 or 30 days after the last cycle of fasting. Fasting/refeeding caused a dramatic increase in crypt multiplicity when compared with regularly fed rats (AC/ACF was 4.30 +/- 1.3 in refed and 2.38 +/- 0.4 in regularly fed rats, P < 0.005 means +/- SD), while no significant changes were observed in the number of ACF/colon. In the two experimental groups, cell proliferation was higher in ACF than in the surrounding mucosa, but proliferative indexes were higher and the apoptotic index lower in ACF of refed rats compared with regularly fed rats. TGFbeta1 expression was higher in the ACF of refed rats than in those of fully fed controls while p21CIP was less expressed in refed rats than in controls. These results suggest that fasting/refeeding is a risk factor for colon cancer and must be taken into account for cancer prevention in humans.

Resveratrol depresses the growth of colorectal aberrant crypt foci by affecting bax and p21(CIP) expression

We investigated whether resveratrol (RV) affects azoxymethane (AOM)-induced colon carcinogenesis, by administering RV (200 microg/kg/day in drinking water) to male F344 rats for 100 days, beginning 10 days before carcinogen treatment (two weekly doses of 15 mg/kg AOM). Aberrant crypt foci (ACF) were isolated and proliferation, apoptosis and expression of the cell cycle genes bax and p21 were determined. RV significantly reduced the number of ACF/colon [25.7 +/- 3.6 (mean +/- SEM) versus 39.4 +/- 3.3 in controls; P < 0.01] and their multiplicity (2.7 +/- 0.3 versus 4.9 +/- 0.6 in controls; P < 0.01), and also abolished large ACF. In RV-treated rats, bax expression was enhanced in ACF but not in the surrounding mucosa. In both controls and RV-treated rats, proliferation was higher in ACF than in normal mucosa. p21 was expressed in ACF of controls and of RV-treated rats and in normal mucosa of controls, but was lost in normal mucosa of RV-treated animals. In conclusion, the results suggest a protective role of RV in colon carcinogenesis with a mechanism involving changes in bax and p21 expression.

Resveratrol depresses the growth of colorectal aberrant crypt foci by affecting bax and p21(CIP) expression

We investigated whether resveratrol (RV) affects azoxymethane (AOM)-induced colon carcinogenesis, by administering RV (200 microg/kg/day in drinking water) to male F344 rats for 100 days, beginning 10 days before carcinogen treatment (two weekly doses of 15 mg/kg AOM). Aberrant crypt foci (ACF) were isolated and proliferation, apoptosis and expression of the cell cycle genes bax and p21 were determined. RV significantly reduced the number of ACF/colon [25.7 +/- 3.6 (mean +/- SEM) versus 39.4 +/- 3.3 in controls; P < 0.01] and their multiplicity (2.7 +/- 0.3 versus 4.9 +/- 0.6 in controls; P < 0.01), and also abolished large ACF. In RV-treated rats, bax expression was enhanced in ACF but not in the surrounding mucosa. In both controls and RV-treated rats, proliferation was higher in ACF than in normal mucosa. p21 was expressed in ACF of controls and of RV-treated rats and in normal mucosa of controls, but was lost in normal mucosa of RV-treated animals. In conclusion, the results suggest a protective role of RV in colon carcinogenesis with a mechanism involving changes in bax and p21 expression.