NONINVASIVE DETECTION OF FECAL PROTEIN-KINASE-C-BETA(PI) AND PROTEIN-KINASE-C-ZETA MESSENGER-RNA - PUTATIVE BIOMARKERS FOR COLON-CANCER

We have developed a non-invasive method utilizing feces, containing sl oughed colonocytes, as a sensitive technique for detecting diagnostic colonic biomarkers. In this study, we used the rat colon carcinogenesi s model to determine if changes in fecal protein kinase C (PKC) expres sion have predictive value in monitoring the neoplastic process. Weanl ing rats were injected with saline or azoxymethane (AOM) and 36 weeks later fecal samples and mucosa were collected, poly A(+) RNA isolated, and quantitative RT-PCR performed using primers to PKC beta(II) and z eta. Fecal PKC beta(II) and zeta mRNA levels mere altered by the prese nce of a tumor, with tumor-bearing animals having a 3-fold higher (P < 0.05) PKC beta(II) expression as compared with animals without tumors . In addition, AOM-injection increased mucosal PKC beta(II) mRNA expre ssion compared with saline controls. No effect of tumor incidence on m ucosal PKC beta(II) expression was observed. In contrast, fecal PKC ze ta expression was 2.5-fold lower (P < 0.05) in animals injected with a zoxymethane versus saline. Since tumor incidence exerts a reciprocal e ffect on fecal PKC beta(II) and zeta mRNA expression, data were also e xpressed as the ratio between PKC beta(II) and zeta. The isozyme ratio was strongly related to tumor 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 that the expression of fecal PKC beta(II) and zeta may serve as a non-invasive marker for development of colon tumor s. A sensitive technique for the detection of colon cancer is of impor tance since early diagnosis can substantially reduce mortality.