VEGF secretion by CD45⁺ and CD45^- MM cells. (A) Sorting of CD45⁺ and CD45^- 5T2MM cells. BMNCs isolated from tumor-bearing mice were stained with anti-5T2MM idiotype antibodies (18B9) and CD45 (i). The 5T2MM cell population was sorted into CD45^- (ii) and CD45⁺ (iii) fractions. Sorted cell populations with a purity of at least 95% were used for further experiments. Dot plots from one representative cell sorting are illustrated. (B) Expression of VEGF transcripts by CD45⁺ and CD45^- 5T2MM cells. Flow cytometric–sorted CD45^- and CD45⁺ MM cells were analyzed for VEGF120 (i) and VEGF164 (ii) mRNA expression by quantitative RT-PCR as described in “Materials and methods.” Values are expressed relative to the expression by CD45^- MM cells. Mean ± SD values of 3 independent experiments are shown. (C) Secretion of VEGF by CD45⁺ and CD45^- 5T2MM cells. VEGF secretion by CD45^- and CD45⁺ MM cells in 24-hour conditioned media was analyzed by ELISA. Mean ± SD values of 3 independent experiments are illustrated.