Differential effects of BAFF on B cell precursor acute lymphoblastic leukemia and Burkitt lymphoma.

B cell-activating factor belonging to the tumor necrosis factor superfamily (BAFF) is a crucial factor for B cell development and is involved in the survival of malignant B cells, but its effect on B cell precursors (BCPs) remains unclear. We investigated BCP acute lymphoblastic leukemia (-ALL) cells for BAFF receptor (-R) expression and compared the effect of BAFF on BCP-ALL cells and Burkitt lymphoma (BL) cells. Expression of BAFF-R was detected in some cell lines and some clinical specimens of both BL and BCP-ALL. BAFF acted on both BL and BCP-ALL cells and promoted proliferation by both. BAFF also inhibited apoptosis by BL cells induced by cross-linking of cell surface molecules and anticancer drugs, but failed to inhibit apoptosis by BCP-ALL cells. BAFF induced prompt and obvious activation of the NF-kappaB signaling pathway in BL cells, but only weak and delayed activation of the pathway in BCP-ALL cells. The results of this study indicate that some BCP-ALL cells and some BL cells express BAFF-R, but that the effects of BAFF on BCP-ALL cells are different from its effects on mature B cell malignancies.