SOCS-2 expression in

BCR-ABL–positive as compared withBCR-ABL–negative cell lines. The upper 2 panels show Northern blots hybridized with SOCS-2 and β-actin of (A) human hematopoietic cell lines, (B) human and murineBCR-ABL–transfected cell lines and their parental counterparts exposed (+) or not (−) to 1 μM STI571 for 10 to 24 hours. The lower 2 panels show densitometric analyses ofSOCS-2/β-actin signals from the Northern blots in panel B: (C) baseline expression in cells not exposed to STI571, demonstrating up-regulation of SOCS-2 in BCR-ABL–positive cells (for comparative purposes, the SOCS-2 signals inBCR-ABL–negative lines were normalized to 1); (D)SOCS-2 down-regulation upon STI571 treatment (for comparative purposes, SOCS-2 levels in nonexposed cells were normalized to 1).