Microvessel overexpression of aquaporin 1 parallels bone marrow angiogenesis in patients with active multiple myeloma

The erythrocyte water channel aquaporin 1 (AQP1) is expressed in multiple a bsorptive and secretory epithelia including the capillary endothelia. Immun oblot analysis showed that bone marrow biopsies of patients with active mul tiple myeloma (MM) display significantly higher levels of AQP1 than those f rom patients with non-active MM, whose values are higher, but to a lesser e xtent, than those of patients with monoclonal gammopathies of undetermined significance (MGUS). Values of MGUS overlapped those of patients with anaem ia as a result of iron or vitamin B-12 deficiencies (called 'benign anaemia s'). Immunohistochemistry and computerized image analysis of AQP1 highlight ed bone marrow microvessels whose area per microscopic field was significan tly greater in patients with active MM, and always larger than and closely correlated with the microvessel area when assessed with factor VIII-related antigen/von Willebrand's factor (FVIII-VWF). The intensity of AQP1 express ion by microvessels evaluated using image analysis was significantly greate r in active than non-active MM and in the latter over MGUS or benign anaemi as. It is suggested that, among plasma cell tumours, AQP1 expression is pre ferentially associated with microvessels of MM and that the highest degree of expression occurs in active MM in step with enhanced angiogenesis, in wh ich AQP1 recognizes more immature neovessels than FVIII-VWF. It may, perhap s, favour angiogenesis in a positive loop and, hence, MM progression, and t hus be applied for therapeutic vascular targeting.