Plasma Inter-Alpha-Trypsin Inhibitor Heavy Chains H3 and H4 Serve as Novel Diagnostic Biomarkers in Human Colorectal Cancer

OBJECTIVE: Inter-alpha-trypsin inhibitor heavy chain H3 (ITIH(3)) and inter-alpha-trypsin inhibitor heavy chain H4 (ITIH(4)) are heavy chains of protein members belonging to the ITI family, which was associated with inflammation and carcinogenesis. However, the diagnostic value of ITIH(3) and ITIH(4) in human colorectal cancer (CRC) remains unknown. METHODS: In total, 101 CRC patients and 156 healthy controls were enrolled. The concentrations of ITIH(3) and ITIH(4) proteins in plasma samples of participants were assessed using enzyme-linked immunosorbent assay. ITIH(3) and ITIH(4) expressions in human CRC tissues were additionally assessed via immunohistochemical staining (IHC). Receiver operating characteristic (ROC) was applied to estimate the diagnostic power of the two proteins, and the net reclassification improvement (NRI) was adopted to evaluate the incremental predictive ability of ITIH(3)/ITIH(4) when added to the tissue inhibitor of metalloproteinase-1 (TIMP-1). RESULTS: The plasma concentration of ITIH(3) in CRC patients (median: 4.370 μg/mL; range: 2.152–8.170 μg/mL) was significantly lower than that in healthy subjects (median: 4.715 μg/mL; range: 2.665–10.257 μg/mL; p < 0.001), while the ITIH(4) plasma level in subjects with CRC (median: 0.211 μg/mL; range: 0.099–0.592 μg/mL) was markedly increased relative to that in the control group (median: 0.134 μg/mL; range: 0.094–0.460 μg/mL, p < 0.001). Consistently, IHC score assessment showed a dramatic reduction in ITIH(3) expression and, conversely, upregulation of ITIH(4) in colorectal carcinoma specimens relative to adjacent normal colorectal tissues (p < 0.001 in both cases). The area under the curve (AUC) of the ROC for ITIH(4) (AUC = 0.801, 95% CI: 0.745–0.857) was higher than that for ITIH(3) (AUC = 0.638, 95% CI: 0.571–0.704, both p values < 0.001). The AUC of the ROC for combined ITIH(3) and ITIH(4) was even higher than that for carcinoembryonic antigen. NRI results showed that combining ITIH(3) and ITIH(4) with TIMP-1 significantly improved diagnostic accuracy (NRI = 17.12%, p = 0.002) for CRC patients compared to TIMP-1 alone. CONCLUSIONS: Circulating ITIH(3) and ITIH(4) levels are associated with carcinogenesis in CRC, supporting their potential diagnostic utility as surrogate biomarkers for colorectal cancer detection.