Abstract: Objective Using the remainder urine samples of hospital laboratories for urinary proteomic analysis to save resource for urine sample collection. Methods Urine samples collected from the same individuals were divided into two parts. In which, half of them was frozen in -80℃ immediately and the rest was stayed in room temperature for 4 h (4h-RT) before frozen in -80℃. Samples were then analyzed by proteomics strategy including sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional gel electrophoresis (2-DE) and liquid chromatography tanden mass spectrometry (LC-MS/MS). The differentially expressed urinary proteins were then compared between the two sample collection methods. Using the urine samples (n=150) collected by 4 h-RT, the expression levels of cytosolic non-specific dipeptidase 2 (CNDP2) between colorectal cancer (CRC) patients and health controls were analyzed by Dot blot assay. Results There was no significant difference in the main protein bands, numbers and positions of SDS-PAGE and 2DE analysis between the frozen immediately and 4 h-RT samples. A total of (1204 ± 50) kinds and (1155 ± 7) kinds of urine proteins, and (7501 ± 661) and (6940 ± 182) peptides were identified with no significant difference between the two groups. The level of CNDP2 was significantly higher in the urine of CRC patients than that in healthy controls (P < 0.001). Conclusions There was no significant difference in urinary proteome between the samples frozen immediately or 4 h-RT staying after collection. The urine samples after laboratory examinations in hospital can be used for urinary proteomics analysis. The expression level of CNDP2 is elevated in the urine of CRC patients and it may be a candidate marker of CRC.

Key words: urine proteome, 2-DE, LC-MS/MS, urinary biomarker