Identification of differential proteins between early submucosal invasive and non-invasive colorectal cancer

Abstract

Objective To construct tumor models of early submucosal invasive colorectal cancer (SICRC) and submucosal non-invasive colorectal cancer (SNICRC) in rats,identify the differential proteins between SICRC,SNICRC and normal control (NC) and screen the biomarkers for early detection and diagnosis of SICRC.Methods N-methyl-N-nitrosourea (MNU) was used to induce tumor models of SICRC and SNICRC in rats.2D-DIGE and MOLDI-TOF-MS/MS were applied to identify the differential proteins between SICRC,SNICRC and NC.Quantitative real-time polymerase chain reaction (PCR) and Western blotting assays confirmed the validation of 2D-DIGE analysis.Results MNU-induced tumor models of SICRC and SNICRC in rats were successfully constructed and five differential proteins were found between SICRC,SNICRC and NC by 2D-DIGE (each P ＜ 0.01 ).The identified results using mass spectrometry showed that Transgelin,Peptidylprolyl isomerase A and Tropomyosin 1 were up-regulated,while carbonic anhydrase 2 ( CA Ⅱ ) and an unnamed protein were down-regulated in SICRC compared with SNICRC and NC.Furthermore,consistent with the proteomics,real-time PCR and Western blottoing assays demonstrated that the relative mRNA and protein levels of Transgelin were highly expressed in SICRC (33.05 ± 0.75,86.63 ± 1.83 ) as compared with SNICRC (22.68 ± 0.89,67.93 ± 2.39) and NC ( 18.07 ± 0.55,44.25 ± 1.55 ) ( each P ＜ 0.05 ),while those of CA Ⅱ were weakly expressed in SICRC (18.01 ±0.53,41.55 ± 1.89) as compared with SNICRC (26.28 ± 1.08,61.11 ± 1.57) and NC (33.08 ±0.76,83.43 ± 1.61 ) (each P ＜0.05).Conclusion 2D-DIGE technique is an effective way to screen the differential proteins between early SICRC and SNICRC and identified proteins such as Transgelin and CA Ⅱ may be the potential biomarkers for early detection and diagnosis of SICRC. Key words: Colorectal cancer; Proteomics; Mass spectrometry; Transgelin; Carbonic anhydrase 2