Site specific reduction of colon cancer incidence, without a concomitant reduction in cryptal cell proliferation, in 1,2-dimethylhydrazine treated rats by diets containing 10% pectin with 5% or 20% corn oil

The effects of specific dietary interventions on incidence ofcarcinogen-induced cancer and on cryptal cell proliferationin areas of the colon located either over aggregates of lymphoidnodules (ALN) or away from ALN was investigated. Groups of dimethylhydrazine(DMH) treated rats or non-DMH-treated rats were fed a basalAIN-76 diet less fiber of any type, or the basal fiber freediet supplemented with 10% pectin and with 5%, 10%, or 20% cornoil. The adenocarcinoma (AC) incidence was determined in regionsof the colon, i.e. ascending, descending, descending over theALN and descending away from the ALN. The results indicate that:(i) factors associated with ALN promote AC formation, (ii) dietarymodifications (addition of pectin and of 20% corn oil to thediet) each cause significant site specific suppression of ACincidence, (iii) DMH-treatment rendered crypts non-responsiveto the suppression of cryptal cell proliferation which occurredin the rats not treated with DMH (suggestive of a DMH-inducedloss in the regulation of cell proliferation) and (iv) reductionof AC incidence was not always accompanied by reduction in cryptcell proliferation. Studies of intervention procedures designedto prevent colon cancer should take into account the colon sitespecific tumorigenic response to the preventive agent and shouldnot rely on a single biomarker to predict the efficacy of theintervention.