Identification of Novel Plasma Protein Biomarkers for Early Clinical Stage Colorectal Carcinoma by High-Throughput Proteomics

Early detection is critical for improving survival in colorectal carcinoma (CRC), underscoring the need for reliable early-stage biomarkers. Plasma protein biomarkers may support the detection of early-stage CRC. In this study, we profiled plasma from 24 patients with stages I–III CRC and 10 non-tumor participants, together with paired tumor and distant-normal tissues from the patients with CRC, to identify proteins preferentially elevated in stage I disease. Seven plasma proteins had higher abundance in stage I CRC than in stages II and III CRC and non-tumor participants; three of these proteins, HSPA8, ALDOA, and PDLIM1, were also elevated in stage I tumor tissues. In the discovery comparison of stage I CRC with non-tumor participants, HSPA8 alone achieved an internally cross-validated random forest classification accuracy of 88.9%, matching the three-protein model. Tissue upregulation was further supported by Western blotting. ELISA assessment included 32 participants with matched proteomic measurements and was subsequently expanded to 108 participants. The HSPA8-score was calculated by dividing the dilution-corrected HSPA8 concentration by the total protein amount in 10 μL of plasma. In the expanded cohort, random forest classification using this score achieved internally cross-validated accuracies of 74.47% for stage I versus stages II–IV CRC and 56.67% for stage I CRC versus non-tumor participants. The corresponding exploratory reference cutoffs were 0.066 and 0.029. These findings identify HSPA8 as a potential plasma protein biomarker for stage I CRC detection.