Effect of interleukin-6 (IL-6) on the production of basic fibroblast growth factor (bFGF) by purified marrow myeloma cells from patients (n = 18).

(A) Basic FGF concentrations in supernatants of myeloma cell cultures after exposure to 0 (native) or 10 ng/mL of IL-6 for 72 hours, presented as pg/mL corrected for 10⁶ cells.P < .002 for difference between native and IL-6–stimulated myeloma cells (Wilcoxon test). (B) Quantitative bFGF-RT-PCR in CD38^high/CD138⁺ marrow myeloma cells of 2 patients (UPN nos. 10 and 11) after exposure to 0 (native) or 10 ng/mL of IL-6 with or without anti–IL-6 for 72 hours. Basic FGF-RT-PCR was performed as described in “Patients, materials, and methods.” Ratios of bFGF over glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression are depicted as fold increase over unstimulated controls. Corresponding patient numbers (UPN) are indicated in panels A and B.