Fig. 1.

Kinetic analysis of the stimulation of proliferation of CD34⁺ cell cultures by tumor-conditioned medium. CD34⁺ cells were seeded under conditions to support myeloid cell growth (GM–CSF and SCF) in the presence or absence of 40% tumor-conditioned medium. At various times, the effect of tumor-conditioned medium on cellularity was approximated by a tetrazolium-based colorimetric assay. Data shown are mean absorbance values  ±  SEM from four separate experiments