[Establishment of stable subline of K562 cells overexpressing high mobility group B1 protein]

This study was aimed to establish a stable subline of K562 cells (K562-HMGB1) overexpressing HMGB1 protein and K562-HMGB1 sublines served as control, so as to provide a basis for exploring the role of hmgb1 gene in occurrence and development of leukemia and their mechanism. Protein-coding gene of hmgb1 was amplified by PCR with cDNA as template, which was synthesized by reverse transcription from total RNA extracted from U937 cells. The PCR-amplified hmgb1 gene was ligated into PMD18-T vector (PMD18-T-HMGB1 vector), and then transformed into E. coli strain DH5α. DH5α containing PMD18-T-HMGB1 vector were grown on LB agar plate supplemented with 100 µg/ml ampicillin overnight. The single ampicillin-selected DH5α clone was picked for culturing overnight and then harvested for plasmid extraction. The extracted plasmid was characterized to contain hmgb1 gene digested with the desired restriction enzymes of KpnI/XhoI. The correctness of hmgb1 sequence was confirmed with DNA sequencing. The insert of hmgb1 gene contained in PMD18-T-HMGB1 vector was cut out with restriction enzymes of KpnI/XhoI and then ligated into eukaryotic expression vector pcDNA3.1 to form pcDNA3.1-HMGB1 vector. 10µg of pcDNA3.1-HMGB1 or pcDNA3.1 plasmid was separately electroporated into K562 cells. At 48 hours after electroporation the cells were cultured with G418 at a final concentration of 800 µg/ml for over 2 weeks. Finally stably transfected sublines of K562 cells containing hmgb1 gene (K562-HMGB1), and of K562 containing pcDNA3.1 vector (K562-pcDNA3.1) served as a control, were obtained. The transcriptional or translational expression of hmgb1 gene was detected with RT-PCR or Western blot, respectively, to testify transfected efficiency and validity of stable subline of K562-HMGB1. The results indicated that the eukaryotic expression vector pcDNA3.1-HMGB1 plasmid was successfully constructed and was electroporated into K562 cells. The transcriptional or translational expression of hmgb1 gene in the stable subline of K562 cells containing hmgb1 gene was overexpressed. It indicated that stable subline of K562-HMGB1 cells was successfully established. It is concluded that the stable sublines of K562-HMGB1 cells or K562-pcDNA3.1 cells are successfully established, which provides a basis for exploring the roles and mechanisms of hmgb1 gene in leukemogenesis and development of leukemia.