VEGF production by CLL cells in response to hypoxic stimulation.

(A) CLL cells from 6 patients were cultured under normoxic and hypoxic conditions. After 24 hours, CM was collected and subjected to ELISA. Higher levels of VEGF protein were detected in the cells cultured under hypoxic conditions (▪) than in those grown under normoxic conditions (■). Histograms represent the mean of duplicates. Error bars are standard deviations calculated from 6 measurements in 3 separate experiments using the cells of 2 patients. (B) Cells from the same patients used for ELISA were also subjected to cellular VEGF mRNA determination by slot-blot hybridization. Hypoxia (H) compared with normoxia (N) increased VEGF mRNA expression in all cases. The bands were measured densitometrically, and the sample loading was determined by parallel measurement of the actin mRNA in each sample.