Abstract #2104: Chemopreventive combinations significantly inhibit the formation of aberrant crypt foci (ACF) in azoxymethane (AOM) treated male Sprague-Dawley rats

Abstract

Colorectal cancer (CRC) is one of the most common causes of cancer deaths in the United States with approximately 50,000 deaths occurring each year. The objective of this study was to study the chemopreventive effects of combinatorial regimens of aspirin, folic acid and calcium on azoxymethane (AOM)-induced male Sprague-Dawley (SD) rats. The inhibition of the formation of aberrant crypt foci (ACF) in the colon of the SD rats was observed. Three (3) groups of six (6) male SD rats each received low (40+3.5+65 mg/kg), medium (133+11+216mg/kg) or high (400+650+32mg/kg) doses of the chemopreventive combinations of aspirin, folic acid and calcium respectively, for 12 weeks. Prior to that, these groups were inoculated with two consecutive weekly subcutaneous injections of AOM (15 mg/kg) to induce the formation of ACF. Additionally, a positive control group of six (6) rats received only saline for the duration of the study whereas another group (6 rats, negative control group) received the AOM injection to induce ACF but no chemopreventive therapy was given. Therapy was started one week after the second AOM injection. After twelve (12) weeks, the rats were sacrificed as per an approved IACUC protocol, the colon harvested, washed with saline and cut longitudinally into three segments representing the proximal, middle and distal colon parts. Each part was fixed in 10% buffered formalin and then immersed in 0.1% methylene blue solution for 5-10 min. ACF identification was conducted by visual inspection using a X40 magnification on a dissecting microscope. ACFs were distinguished from the surrounding normal crypts by their increased size, significantly increased distance from lamina to basal surfaces of cells, and the easily discernible pericryptal zone. All colons were scored by one observer who was blinded to the identity of the agents under study and subsequently by the primary investigator responsible for ACF studies. Data obtained was compared to saline and AOM control animal groups. At the termination of the study, ACFs were counted in the colons of AOM-control rats and compared with treated rats. In rats given low dose of chemopreventive combinations along with AOM, the ACF/colon was significantly reduced compared to rats given AOM alone (p<0.05). Most of the ACF appeared in the distal colon in both AOM-control and treated rats rather than the proximal or the middle colon. Overall, the low dose group showed a 31% decrease in AC counts compared to the AOM-control. The medium and high dose treated rats also demonstrated significant reduction in ACF/colon however the low dose group was selected for further studies.. From the results obtained, we were successful in demonstrating that the low dose chemopreventive treatment group had a significant impact on the ACF progression within the colon and these data will be used to design newer regimens for colon cancer chemoprevention.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 2104.