Effect of tumor-produced VEGF on hematopoiesis. Tumor-produced VEGF underlies altered hematopoiesis. (A) Levels of VEGF in the supernatant of established mammary carcinoma cell lines (□) and in the supernatant of 48-hour primary culture of spontaneous mammary tumors (▪), measured by ELISA. (B) Levels of VEGF in serum from 3 representative BALB-neuT females at 22 to 26 weeks of age (□) in correlation with the rising percentage of Gr-1/Mac-1 cells in the PB (▪) and tumor multiplicity (○). (C) VEGF-neutralizing Ab-mediated inhibition of the effects of BALB-neuT tumor supernatant on normal BALB/c hematopoietic stem/progenitor–enriched cells. Sca-1⁺–enriched BM cells were conditioned for 5 days with medium containing 50% tumor supernatant (□), in the presence of anti-VEGF Ab (Ab JH121), isotype-matched control Ab, or medium alone (▪) before CFU assay in methylcellulose. Statistically significant differences of anti-VEGF treatment from control: *P < .03; ** P < .01 (mean of 3 replicates ± SD).