In patients with malignant disease, the Ang/Tie system might serve as a tumour or response marker. In patients with multiple myeloma, normalization of the Ang-1/Ang-2 ratio reflects a response to treatment with anti-angiogenesis medication [176] . In patients with non-small-cell lung cancer, Ang-2 is increased in serum and indicates tumour progression [177] . After allogeneic stem cell transplantation in patients with high-risk myeloid malignancies, the serum Ang-2 concentration predicts disease-free survival [178] , possibly reflecting a relation between cancer-driven angiogenesis and Ang-2 serum level.