VEGF₁₆₅ protects CLL B cells from spontaneous apoptosis/cell death and overcomes chlorambucil-induced apoptosis/cell death. (A) CLL B cells from 7 separate individuals were cultured without (NIL) and with the indicated concentrations of VEGF (ng/mL indicated in parentheses) and the mean level of spontaneous apoptosis/cell death was determined after 24 hours in culture. The mean decrease in apoptosis with VEGF-exposed CLL B cells was substantially lower when compared with control cells. (B) CLL B cells were first cultured with VEGF₁₆₅ (2 ng/mL) or diluent for 24 hours and then incubated with chlorambucil (10 μM) for an additional 24 hours before assessing levels of apoptosis/cell death. Data (mean ± 1 SEM) shown are representative of 4 different patients. C indicates chlorambucil; NIL, B cells cultured without VEGF; and *, statistical analysis.