BCL-6/LAZ3 gene encodes a zinc-finger transcriptional repressor and is loca
ted at the breakpoint of the 3q27-associated translocations that occur most
frequently in non-Hodgkin's lymphomas (NHLs). A number of chromosomal tran
slocations involving BCL-6 have been analyzed, but the biological functions
of this protein remain obscure. To examine cell responses and target genes
related to the BCL-6 signaling pathway, we established Ba/F3 pro-B cells c
arrying a human BCL-6 transgene that is inducible under control of the lact
ose operon. Using a cDNA array hybridization technique, we found that the i
nduced BCL-6 protein can downregulate the expressions of the genes, cyclin.
A2, chemokine receptor CXCR4 and insulin-like growth factor binding protei
n-4 (IGFBP-4) in the Ba/F3 cells. Northern blot analysis established that t
he expressions of these genes were indeed downregulated by the induced BCL-
6 protein but in a somewhat different manner. The induced BCL-6 protein als
o inhibited cell proliferation of Ba/F3 cells. These findings strongly sugg
est that three key genes, namely cyclin A2, CXCR4 and IGFBP-4 may play a ro
le in the downstream of the BCL-6 signaling pathway during B-lymphoid diffe
rentiation. (C) 2001 Academic Press.