Angiopoietin system expression in patients with MM. Ang-1 mRNA expression was evaluated by RT-PCR in highly purified (more than 90%) MM cells obtained from 23 patients at diagnosis or relapse. (A) In 18 patients, Ang-2 and Tie2 mRNA expression were also tested. (B) Ang-1, Ang-2, and Tie2 protein production, evaluated by Western blot analysis immediately after immunomagnetic purification, are shown for 2 representative patients with MM (MM1, Ang-1–positive; MM5, Ang-1–negative). (C) Ang-1 and Ang-2 protein expression in a cell-contact coculture system with fresh MM cells and either BM endothelial cell line BMEC-60 (BMEC) or BM stromal cells (BMSCs).