Evaluation of circulating IGF-I and IGFBP-3 as biomarkers for tumors in dogs

Serum-based parameters are considered non-invasive biomarkers for cancer detection. In human studies, insulin-like growth factor-I and II (IGF-I and IGF-II) and insulin-like growth factor binding protein-3 (IGFBP-3) are useful as diagnostic or prognostic markers and potential therapeutic targets. This study examined the diagnostic utility of circulating IGF-I, IGF-II, and IGFBP-3 levels in healthy dogs and dogs with tumors. The serum concentrations of these biomarkers in 86 dogs with tumors were compared with those in 30 healthy dogs using an enzyme-linked immunosorbent assay (ELISA). The ELISA results showed no difference between healthy dogs and dogs with tumors in the serum IGF-II concentrations. On the other hand, there was a significant difference in the circulating IGF-I and IGFBP-3 levels between healthy dogs and dogs with tumors. The concentrations of serum IGF-I (median [interquartile range], 103.4 [59.5-175] ng/mL) in dogs with epithelial tumors were higher than those (58.4 ng/mL [43.5-79.9]) in healthy dogs. Thus, the concentrations of serum IGFBP-3 (43.4 ng/mL [33.2-57.2]) in dogs with malignant mesenchymal tumors were lower than those (60.8 ng/mL [47.6-70.5]) in healthy dogs. The serum IGF-I and IGFBP-3 levels can be used as diagnostic biomarkers in dogs with tumors.