Human-Derived Proteome Characterization of Tongue Coating in Colorectal Cancer

Most colorectal cancer (CRC) patients experience changes in tongue coating morphology, but the underlying mechanisms remain unclear. While the human-derived proteome of tongue coatings in gastric cancer and healthy individuals has been characterized, research on CRC patients remains lacking. The tongue coating collection process is painless and noninvasive, providing a more favorable examination experience. This study aims to preliminarily explore the composition and changes in the human-derived proteome of tongue coatings in CRC patients, providing insights into abnormal morphology and potential new CRC screening methods. Utilizing a "bottom-up" strategy and data-independent acquisition (DIA) mode, the human-derived proteome of tongue coating in healthy controls, colorectal hyperplastic polyps patients, and CRC patients was detected using the EASY-nLC 1200 chromatograph coupled with the Orbitrap Fusion Lumos Tribrid mass spectrometer. Differentially expressed proteins were validated by Western blot, and the diagnostic efficacy of tongue coating proteins compared with CRC serum markers was assessed. Our results indicate that the human tongue coating proteome undergoes significant changes in CRC, with upregulated proteins potentially involved in remodeling the tongue coating morphology. Hemopexin (HPX), fibrinogen β chain (FGB), and cystatin C (CST3) in the tongue coating are promising indicators for CRC screening.