Proteomic profiling of tear fluid as a promising non-invasive screening test for colon cancer.

Background: Current screening options for colorectal cancer (CRC) are either invasive (colonoscopy) or have lower sensitivity to identify pre-malignant lesions (fecal immunochemical test). We proposed to identify protein profiles in tears of patients with both pre-malignant polyps and CRC; these profiles could have potential as a noninvasive screening test.

Method: Colonoscopy patients were divided into "high risk" group (CRC and tubular adenomatous polyp) and "low risk" (normal and hyperplastic polyps). Tear fluids from patients were analyzed by Liquid Chromatography Mass Spectrometry/Mass Spectrometry. The data were analyzed for protein expression, protein-protein interaction and gene set enrichment.

Results: The results showed 80 proteins (18 up-regulated and 62 down-regulated) significantly differentiated in "high-risk" compared to "low-risk"; Twenty-eight of these show protein-protein interactions, 9 of which were associated with pathways demonstrated to be altered in CRC patients.

Conclusion: Our pilot data, though limited, demonstrated tear protein profiling could distinguish the groups of patients with and without colon lesions.