Early and mature endothelial progenitors and VEGFR2+-cells in multiple myeloma: association with disease characteristics and variation in different cell compartments.

We analyzed (1) early endothelial progenitors (EPCs; CD34(+)/AC133(+)/VEGFR2(+)), mature EPCs (CD34(+)/VEGFR2(+)) and VEGFR2(+)-cells in bone marrow (BM)-specimens of multiple myeloma (MM)- vs. monoclonal gammopathy (MGUS)-patients and healthy controls; (2) differences of BM-, peripheral blood (PB)- and leukapheresis (LP)-samples; and (3) the association of EPCs and VEGFR2(+)-cells with MM-parameters. MM patients demonstrated highest early and mature EPCs and VEGFR2(+)-cells in the BM, particularly with advanced and active disease. Endothelial cells differed in BM-, PB- and LP-specimens, albeit seemed less associated with unfavorable prognostic MM-parameters. Our data suggest that especially VEGFR2(+)-cells and mature EPCs in MM are of value to explore further.