CD40 activation induces p53-dependent vascular endothelial growth factor secretion in human multiple myeloma cells

It was previously demonstrated that p53 status in human multiple myeloma (MM) cells regulates distinct cell cycle responses to CD40 activation. In this study, the production of vascular endothelial growth factor (VEGF) and migration in MM cells triggered by CD40 activation was examined, and the influence of p53 status in regulating this process was determined. Two human MM cell lines that express wild-type p53 at permissive (28 degrees C) and mutant p53 at restrictive (37 degrees C) temperatures were used as a model system. CD40 activation induces a 4-fold (RPMI 8226) and a 6-fold (SV) increase in VEGF transcripts, respectively, under restrictive, but not permissive, temperatures. VEGF expression is significantly induced after CD40 activation in patient MM cells expressing mutant p53. Increased VEGF transcripts result in increased protein and secretion levels, as evidenced by immunoblotting and enzyme-linked immunosorbent assay. In a double-chamber transmigration assay, CD40 activation of MM cells induced a 3-fold (RPMI 8226) and a 5-fold (SV) increase in migration under restrictive, but not permissive, conditions. A 2- to 8-fold induction in migration of patient MM cells expressing mutant p53 was similarly observed. Transduction of MM cells with a luciferase reporter under the control of a human VEGF promoter further indicated that CD40-induced VEGF expression was mediated through a transcriptional control mechanism. Finally, adenovirus-mediated wild-type p53 overexpression down-regulated CD40-induced VEGF expression and transmigration in MM cells expressing mutant p53. These studies demonstrate that CD40 induces VEGF secretion and MM cell migration, suggesting a role for CD40 in regulating MM homing and angiogenesis.