VEGF Autocrine System Is Demonstrated in Some of Acute Promyelocytic Leukemia Cases: Relationship to WBC Count at the Disease Onset.

In acute promyelocytic leukemia (M3), a prominent production of vascular endothelial growth factor (VEGF) is reported, and the obvious angiogenesis is observed in bone marrow specimens; however, VEGF receptors (VEGFRs) are not expressed in M3 cells in general. We analyzed VEGF systems in M3 blasts.

Bone marrow cells were obtained from informed M3 patients, whose mononuclear cells were prepared with density-sedimentation method. Cells were cultured for one day for the elimination of an adherent cell-fraction. RNA was extracted from the non-adherent mononuclear cell-fraction, and cDNA was synthesized. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to determine the expression of VEGF and VEGFRs. When the expression of VEGFR type-1 and -2 was demonstrated with RT-PCR, cells were analyzed on the protein level with FACS. VEGF-A levels in sera and in the conditioned media from the cultured M3 cells were determined with ELISA kit. When M3 blasts expressed VEGFR type-1, -2, and also secreted VEGF-A, a growth-inhibition by anti-VEGF antibody was assayed in in vitro cultures.

In all 25 cases examined VEGF-A production was observed, in which VEGFR type-3 was not expressed in any cases. VEGFR type-1 and -2 were expressed in 3 cases, in all of which WBC count at the onset of the disease was above 20,000/μl. When VEGF antibody was added to the blast cell-cultures, the cell-growth was inhibited significantly. These observations indicate that VEGF system works on proliferation in a few of M3 cases with hyper-leukocytosis.

No relevant conflicts of interest to declare.