Non-invasive detection of fecal protein kinase C betaII and zeta messenger RNA: putative biomarkers for colon cancer

We have developed a non-invasive method utilizing feces, containingsloughed colonocytes, as a sensitive technique for detecting diagnosticcolonic biomarkers. In this study, we used the rat colon carcinogenesismodel to determine if changes in fecal protein kinase C (PKC) expressionhave predictive value in monitoring the neoplastic process. Weanling ratswere injected with saline or azoxymethane (AOM) and 36 weeks later fecalsamples and mucosa were collected, poly A+ RNA isolated, and quantitativeRT-PCR performed using primers to PKC betaII and zeta. Fecal PKC betaII andzeta mRNA levels were altered by the presence of a tumor, withtumor-bearing animals having a 3-fold higher (P < 0.05) PKC betaIIexpression as compared with animals without tumors. In addition,AOM-injection increased mucosal PKC betaII mRNA expression compared withsaline controls. No effect of tumor incidence on mucosal PKC betaIIexpression was observed. In contrast, fecal PKC zeta expression was2.5-fold lower (P < 0.05) in animals injected with azoxymethane versussaline. Since tumor incidence exerts a reciprocal effect on fecal PKCbetaII and zeta mRNA expression, data were also expressed as the ratiobetween PKC betaII and zeta. The isozyme ratio was strongly related totumor incidence, i.e. ratio for animals with tumors was 2.18 +/- 1.25,animals without tumors was 0.50 +/- 0.16, P = 0.025. We demonstrate thatthe expression of fecal PKC betaII and zeta may serve as a noninvasivemarker for development of colon tumors. A sensitive technique for thedetection of colon cancer is of importance since early diagnosis cansubstantially reduce mortality.