Collagen Type XV (COL15, encoded by COL15A1) is a non-fibrillar FACIT collagen, widely distributed in human tissues and highly enriched in basement membrane zones. It forms a homotrimeric structure with interrupted collagenous domains, functioning to anchor basement membranes to underlying connective tissue stroma and stabilize tissue architecture. Its C-terminal fragment, restin, exhibits anti-angiogenic activity. COL15 acts as a tumor suppressor; its loss correlates with muscle/microvessel degeneration and enhanced cancer cell invasion. Hypoxia upregulates COL15 via HIF-1α, and it modulates epithelial-mesenchymal transition (EMT) in tumor microenvironments. COL15 indirectly interacts with E-cadherin by regulating EMT signaling, thereby stabilizing E-cadherin-mediated cell-cell adhesion.Thus a functional ELISA assay was conducted to detect the interaction of recombinant human COL15 and recombinant human EMT. Briefly, COL15 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to EMT-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-COL15 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 μL stop solution to the wells and read at 450/630nm immediately. The binding activity of recombinant human COL15 and recombinant human EMT was shown in Figure 1, the EC50?for this effect is 0.0117 μg/mL.