The development of noninvasive methods for early detection of
colon cancer is critical for the successful management of this disease. Using a targeted quantitative proteomics technique, we assessed the ability of 12
serum proteins to detect the presence of
colonic polyps in the Apc(Pirc) (/+) rat model of familial
colon cancer.
Serum protein candidates were selected from gene transcripts upregulated in colonic
tumors of Apc(Pirc) (/+) rats and from a prior study of
serum proteins differentially expressed in mice carrying intestinal
adenomas.
Proteins were quantified at early stages of
polyp formation in a rat cohort monitored longitudinally by colonoscopy over a period of 75 days. Of the 12
proteins monitored at three distinct time points, seven showed differential expression in at least one time point in the serum from Apc(Pirc) (/+) rats compared with wild-type rats.
Tumor multiplicity correlated with
protein expression changes, and most
tumors grew during the study. EGFR, LRG1, ITIH4, and F5 displayed the most robust
tumor-associated
protein expression changes over time. Receiver operator characteristic analysis using these four
proteins resulted in a sensitivity of 100%, a specificity of 80%, and an area under the curve of 0.93 at 135 days of age, when the Pirc rats bore an average of 19
tumors in the colon and seven in the small intestine. The results of this study demonstrate that the quantitative analysis of a panel of
serum proteins can detect the presence of early intestinal
tumors in a rat model, and provides support for future measurements in humans.