Prednisolone sodium succinate down-regulates BSAP/Pax5 and causes a growth arrest in the Nalm6 pre-B cell line

Glucocorticoids (GCs) induce growth arrest and apoptosis of B lineage cells, especially pre-B and immature B cells, but little is known about this mechanism. Since B cell-specific activator protein (BSAP) encoded by the Pax5 gene is an essential transcription factor for B-cell proliferation, we have investigated the effect of prednisolone sodium succinate (Pss) on BSAP expression in several human leukemic B lineage cell lines. Pss caused growth arrest of Nalm6 (pre-B) cells, but this is not the case for 207 (pro-B) and Raji (mature B) cells. In Nalm6 cells, the growth rate and the amount of BSAP bound to its recognition sequence decreased in proportion to the Pss dose. Pss also reduced the expression level of BSAP as well as of Pax5 mRNA. These data suggest that the suppression of Pax5/BSAP may be involved in the GCs-induced growth arrest of pre-B cells.