Dietary carcinogens, such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and chronic inflammation have each been implicated as etiologic agents in prostate cancer. We hypothesized that bacterial prostatitis would accelerate PhIP-induced preinvasive lesions in the rat prostate. Male Fischer 344 rats were assigned into 4 groups: Control (untreated), PhIP (200 ppm in the diet for 20 weeks), Escherichia coli (E. coli, prostatic inoculation in week 10), or PhIP + E. coli. Study animals were monitored for a total of 52 weeks and were euthanized as necessary based on strict criteria for health status and tumor burden. Animals treated with E. coli initially developed acute and chronic inflammation in all lobes of the prostate, whereas inflammation was observed predominantly in the ventral lobe at time of death. PhIP + E. coli-treated animals exhibited a marked decrease in survival compared with PhIP-alone-treated animals as a result of an increase in the number of invasive cancers that developed at multiple sites, including the skin, small intestine, and Zymbal's gland. Despite their earlier mortality, PhIP + E. coli-treated animals developed an increased average number of precancerous lesions within the prostate compared with PhIP-treated animals, with a significantly increased Ki-67 index. Multiplexed serum cytokine analysis indicated an increase in the level of circulating IL6 and IL12 in PhIP + E. coli-treated animals. Elevated serum IL6 levels correlated with the development of precancerous lesions within the prostate. These results suggest that bacterial infections and dietary carcinogens, two conceivably preventable cancer risk factors, may synergistically promote tumorigenesis.
©2015 American Association for Cancer Research.