Coffee, but Neither Decaffeinated Coffee nor Caffeine, Elicits Chemoprotection Against a Direct Carcinogen in the Colon of Wistar Rats.

Colorectal cancer (CRC) is the third most frequent malignancy worldwide. Coffee is the second most consumed drink in the globe and suggested to decrease the CRC risk. Here, we explored whether coffee, decaffeinated coffee, or caffeine impact on the development of colorectal carcinogenesis induced by the direct carcinogen N-methyl-N-nitro-N-nitrosoguanidine (MNNG) in rats. To this end, sixty-four young male Wistar rats were divided into eight groups of eight animals each. We analyzed the frequency of dysplastic crypts and expression of metallothionein as a biomarker of the cancer risk, as well the expression of phosphorylated H2A histone family/member X (γH2AX) for DNA damage and cyclooxygenase-2 (COX-2) for inflammatory response. We also studied the oxidative stress profile in hepatic and colonic frozen samples (malondialdehyde [MDA], glutathione [GSH], and α-tocopherol). We found that coffee but neither decaffeinated coffee nor caffeine decreased the development of dysplastic crypts in MNNG-exposed rats. All treatments reduced DNA damage intensity in colonocytes. Only decaffeinated coffee increased the numbers of metallothionein positive crypts in comparison with coffee-treated rats. Coffee and caffeine inhibited COX-2 expression in the colon. Both decaffeinated coffee and caffeine decreased hepatic α-tocopherol levels. We suggest that coffee may have other compounds that elicit greater chemoprotective effects than caffeine reducing the CRC risk.

Multiple mucin depleted foci, high proliferation and low apoptotic response in the onset of colon carcinogenesis of the PIRC rat, mutated in Apc.

PIRC rats (F344/NTac-Apc (am1137) ) mutated in the Apc gene spontaneously develop colon tumors thus mimicking familial adenomatous polyposis (FAP) and sporadic colorectal cancer (CRC) more closely than Apc-based rodent models developing tumors mostly in the small intestine. To understand whether microscopic dysplastic lesions precede the development of macroscopic tumors, PIRC rat colon was examined for the presence of mucin depleted foci (MDF), microadenomas of the rodent and human colon. Few MDF (about 4/animal) were already present in 1-month-old rats and their number rapidly increases to about 250 in 8-month-old rats. These lesions showed Wnt signaling activation (nuclear ß-catenin accumulation) and were dramatically decreased by sulindac (320 ppm), a drug with chemopreventive activity (MDF/rat at 4 months: 156 ± 8 and 38 ± 6 in controls and sulindac-treated rats, respectively, means ± SE, p < 0.001). Since altered proliferation and apoptosis could underlie the early phases of carcinogenesis, we studied these processes in the apparently normal colon mucosa (NM) of 1-month-old PIRC and wt rats. Colon proliferation (PCNA expression) was significantly higher in PIRC rats. Notably, PIRC rat NM showed resistance to apoptosis since it sustained proliferation and had lower apoptosis after a cytotoxic insult with 1,2 dimethylhydrazine. Gene expression of Myc, p21, Birc5, Ogg1, Apex1 and Sod2 were significantly up-regulated in the NM of PIRC rat. The overall results put forward PIRC rat as useful model of colon carcinogenesis, either to study the process itself or to test in vivo chemopreventive agents in both short- and long-term studies.

Sulindac, 3,3'-diindolylmethane and curcumin reduce carcinogenesis in the Pirc rat, an Apc-driven model of colon carcinogenesis.

BACKGROUND: Recently, we showed that Sulindac (SU; 320 ppm) reduces precancerous lesions in the colon of Pirc rats, mutated in the Apc gene. Surprisingly, previous data in Apc-mutated mice showed that SU, with reported efficacy in Familial Adenomatous Polyposis (FAP), increases colon carcinogenesis. Therefore, we assessed the effect of SU 320 ppm in a long-term carcinogenesis experiment in Pirc rats. Moreover, since side effects of SU hamper its chronic use and a combination of drugs could be more effective and less toxic than single agents, we also studied whether two natural compounds, 3,3'-diindolylmethane (DIM; 250 ppm) and curcumin (CUR; 2000 ppm), with or without lower doses of SU could affect carcinogenesis METHODS: Pirc rats were fed an AIN76 diet containing SU, DIM and CUR and sacrificed at 8 months of age to measure intestinal tumours. Apoptosis and proliferation in the normal colon mucosa, as well as gene expression profile were studied RESULTS: Colon tumours were significantly reduced by SU 320 ppm (62 % reduction over Controls), by DIM and CUR without or with SU 80 and 160 ppm (50, 53 and 58 % reduction, respectively) but not by SU 80 ppm alone. Total tumours (colon and small intestine) were reduced by SU (80 and 320 ppm) and by DIM and CUR. Apoptosis in the normal mucosa was significantly increased by SU 320 ppm, and slightly increased by DIM and CUR with or without SU. A slight reduction in Survivin-Birc5 expression was observed with all the treatments compared to Controls. Proliferative activity was not varied CONCLUSIONS: The results on SU reinforce the validity of Pirc rats to identify chemopreventive products. Moreover, the efficacy of the DIM and CUR combination to lower colon tumours, suggests an alternative strategy to be exploited in patients at risk.