Serum phosphopeptide profiling for colorectal cancer diagnosis using liquid chromatography–mass spectrometry.

Rationale: The identification and evaluation of novel biomarkers are essential to clinical diagnosis and prognosis of colorectal cancer (CRC). Serum phosphopeptides have been recognized as a potential signature pool for cancers; therefore, we aim to profile the expression of serum phosphopeptides and to evaluate their feasibility in CRC diagnosis. Methods: We conducted the characterization and absolute quantification of endogenous phosphopeptides in sera using liquid chromatography–mass spectrometry analysis in combination with enrichment of phosphopeptides by ZrAs‐Fe3O4@SiO2nanoparticles and use of deuterium‐labeled standards. Differentially expressed analysis of four phosphopeptides was performed, generating a two‐phosphopeptide‐based biomarker, LF3–4, by logistic regression analysis, where LF3–4 is equal to (5.85 − 5.13 × [F3] − 3.57 × [F4]), and [F3] and [F4] are the concentration of phosphopeptides DpSGEGDFLAEGGGVR and ADpSGEGDFLAEGGGVR in sera, respectively. Results: The LF3–4 values showed significant difference in CRC cases compared with controls, and yielded a specificity of 100%, leading to correct classification of 56 (93%) out of 60 CRC patients, including 12 (92.3%) of 13 CRC cases in stage I. Double‐blind validation showed that 97.5% of CRC cases were discriminated accurately. Conclusions: The LF3–4 value was firstly verified to be a potential biomarker for CRC diagnosis, and may expand our view in underlying mechanisms for CRC. [ABSTRACT FROM AUTHOR]