Pak1 gene functioned differentially in different BCR-ABL subtypes in leukemiagenesis and treatment response through STAT5 pathway.

The BCR-ABL fusion gene (BCR-ABL) has different subtypes such as p210 and p190 with p190 appear to lead to a worse prognosis. To explore the mechanism of difference in pathogenesis and prognosis in different BCR-ABL subtype-related leukemia, expression profile microarray analysis was conducted between p190 and p210 patients and verified by RT-PCR. The p21-activated kinase (PAK1) gene was chosen and regulation of the PAK1-STAT5 biological axis and its influence on proliferation and apoptosis in leukemia cells were also analyzed. The results showed that PAK1 might be an important molecular mechanism of the pathogenic difference between different BCR-ABL subtypes. In P210 (+) chronic myelogenous leukemia (CML), down-regulated PAK1 gene expressions may lead to the suppression of cell proliferation and promotion of apoptosis through phosphorylation of STAT5, with a reverse effect in P190 (+) acute lymphoblastic leukemia(ALL), especially acute B lymphoblastic leukemia (B-ALL). Additionally, in P210 (+) CML, down-regulated PAK1 expression may enhance the effect of TKI, whereas the reverse is true in P190 (+) B-ALL, demonstrating that PAK1 might also be an important therapeutic target between different BCR-ABL subtypes.