We used fluorescence in situ hybridization and reverse transcription polymerase chain reaction (RT-PCR) assays to describe a BCR-JAK2 fusion gene from a patient with acute lymphoblastic leukemia.     ///    "Recent reports described a BCR-JAK2 fusion gene in fatal chronic and acute myeloid leukemia, but the functional behavior of the chimeric protein remains uncharacterized. "    ///    "Therefore, BCR-JAK2 is a novel tyrosine-kinase with transforming activity."    ///    BCR-JAK2 codes for a protein containing the BCR oligomerization domain fused to the JAK2 tyrosine-kinase domain.     ///    Transforming and tumorigenic activity of JAK2 by fusion to BCR: molecular mechanisms of action of a novel BCR-JAK2 tyrosine-kinase..     ///    "Treatment with the JAK2 inhibitor TG101209 abrogated BCR-JAK2 and STAT5 phosphorylation, decreased Bcl-xL expression and triggered apoptosis of transformed Ba/F3 cells. "    ///    Primary mouse progenitor cells transduced with BCR-JAK2 also showed increased proliferation and survival.     ///    "Therefore, BCR-JAK2 is a novel tyrosine-kinase with transforming activity. "    ///    "Moreover, transformed Ba/F3 cells developed tumors when injected subcutaneously into nude mice, thus proving the tumorigenic capacity of BCR-JAK2 in vivo. "    ///    In vitro analysis of transfected cells showed that BCR-JAK2 is located in the cytoplasm.     ///    "Transduction of hematopoietic Ba/F3 cells with retroviral vectors carrying BCR-JAK2 induced IL-3-independent cell growth, constitutive activation of the chimeric protein as well as STAT5 phosphorylation and translocation to the nuclei, where Bcl-xL gene expression was elicited. "