ABSTRACT
<p><b>OBJECTIVE</b>To investigate the regulation of Bruton's tyrosine kinase (Btk) and to explore its possible mechanism.</p><p><b>METHODS</b>After treatment with the proteasome inhibitors and/or phorbol esters (PMA), the mRNA and protein expression level of Btk was detected by RT-PCR and Western blot, respectively. The ubiquitination level of Btk in B lymphoblastoid A20 cells was estimated after stimulation via the crosslinking of BCR with anti-IgM antibody. The cotransfection of COS-7 cell with Btk, ubiquitin and Cbl was performed, then the ubiquitination level of Btk was measured. The Btk ubiquitination level was detected after ectopic expression of ubiquitin transfected with the wild type or triple mutant of Ub (K29R, K48R, K63R) . Mono-ubiquitination of Btk was detected with antibodies preferentially against monovalent ubiquitin; in addition, the protein expression levels of chloroquine-treated stably transfected cells expressing Btk-GFP were detected by Western blot, and quantified with the strength of GFP fluorescence.</p><p><b>RESULTS</b>In the presence of proteasome-specific inhibitors and/or PMA, steady-state levels of Btk protein were reduced due to decrease of transcription. Posttranslational modification of Btk by ubiquitination was observed, which was related with the level of Btk expression and activation. The E3 ubiquitin ligase Cbl, which binds to Btk, was also found to ubiquitinate this kinase. Altogether, the data of this study strongly suggest that Btk is regulated by poly- and/or mono-ubiquitination events.</p><p><b>CONCLUSION</b>The Btk protein is dictated by its expression level through the ubiquitination pathway.</p>
ABSTRACT
<p><b>OBJECTIVE</b>To establish human B-acute lymphoblastic leukemia NOD/SCID mouse model.</p><p><b>METHODS</b>The unirradiated mice aged 4-5 weeks were injected with Nalm-6 cells via the tail vein. Successful transplantation was assessed by the general state, bone marrow smear and histopathologic examination.</p><p><b>RESULTS</b>After 15 days of injection with Nalm-6 cells, the NOD/SCID mice displayed the morbidily with lethargy, hind limb paralysis, hunched back and lossing weight. The infiltration of leukemia cells could be observed in bone marrow and spleen sections.</p><p><b>CONCLUSION</b>Systemic B lineage acute leukemia animal mode1 has been successfully established in the NOD/SCID mice, which is a useful tool for studying pathogenesis of leukemia and guiding clinical chemotherapy regimens.</p>