Proposed model of the effects of VEGF on VEGFR⁺ cells such as subsets of leukemias.

Patients with leukemia have elevated circulating VEGF levels, which, in an autocrine or paracrine fashion, may stimulate VEGFR-2 (KDR) resulting in activation of the MAP kinase pathway and increased Hsp90 levels. Hsp90 in turn promotes survival of leukemic cells by binding APAF-1 and Bcl-2, thereby inhibiting apoptosis. Whether there is a direct interaction between Hsp90, APAF-1, and Bcl-2 is still not established.