Proteomics-Based Analysis of Clinical Significance of Roundabout Guidance Receptor 4 and Protocadherin 12 in Screening,Diagnosis,and Staging of Colorectal Cancer.

Objective To explore the clinical significance of roundabout guidance receptor 4(ROBO4) and protocadherin 12(PCDH12) in the human serum in the screening,diagnosis,and staging of colorectal cancer(CRC) through proteomics and bioinformatics,thus providing a novel screening method with high specificity,sensitivity,and accuracy for the early screening and diagnosis of CRC in clinical practice. Methods Proteomics and bioinformatics approaches were employed to select the target proteins ROBO4 and PCDH12,and the correlation between ROBO4 and PCDH12 was analyzed.A total of 121 CRC patients(cancer group),112 patients with polyps(polyp group),and 108 healthy volunteers(normal group) who received treatment or physical examination from January 2023 to June 2024 were enrolled in this study.ELISA was employed to determine the expression levels of ROBO4,PCDH12,carcinoembryonic antigen(CEA),and carbohydrate antigen 199(CA199) in the samples of each group.The expression levels of the four proteins in the serum were compared among the three groups of patients mentioned above,and the relationships of the serum levels of ROBO4 and PCDH12 with the pathological characteristics of the CRC patients were analyzed.Furthermore,the receiver operating characteristic(ROC) curves were established to evaluate the diagnostic efficacy of the serum levels of ROBO4 and PCDH12 for CRC patients in early and progressive stages. Results The target proteins ROBO4 and PCDH12 were screened out through proteomics.Bioinformatics analysis showed that ROBO4 and PCDH12 were highly expressed in CRC patients.Further correlation analysis revealed a positive correlation between ROBO4 and PCDH12 in CRC(<i>R</i>=0.870,<i>P</i><0.001).The ELISA results of clinical samples showed that compared with the normal group and polyp group,the cancer group presented elevated expression levels of ROBO4 and PCDH12(all <i>P</i><0.001).There was no statistically significant difference in the expression level of ROBO4 or PCDH12 between the normal group and the polyp group(<i>P</i>=0.586,<i>P</i>=0.550).The ROC curves showed that the diagnostic efficacy of ROBO4,PCDH12,and ROBO4+PCDH12 was 0.787,0.757,and 0.812,respectively,all of which were higher than the diagnostic efficacy of CEA and CA199.Further analysis of serum levels of ROBO4 and PCDH12 with the pathological data of CRC showed that the serum level of ROBO4 was correlated with differentiation degree(<i>P</i>=0.013),pathological stage(<i>P</i>=0.002),lymph node metastasis(<i>P</i>=0.001),and distant metastasis(<i>P</i>=0.026).The serum level of PCDH12 was correlated with differentiation degree(<i>P</i>=0.043),pathological stage(<i>P</i>=0.012),and lymph node metastasis(<i>P</i>=0.001).The ROC curves showed that the diagnostic efficacy of ROBO4,PCDH12,and ROBO4+PCDH12 was 0.637,0.758,and 0.787 for early CRC and 0.872,0.757,and 0.882 for progressive CRC,respectively. Conclusions The serum levels of ROBO4 and PCDH12 demonstrate high diagnostic efficacy for CRC patients and are correlated with the pathological features of CRC.The two proteins are expected to be novel serum biomarkers for the diagnosis and screening of CRC.