Construction of granulocyte-macrophage colony stimulating factor gene eukaryotic expressing plasmid and identification of its biological activity

Objective To construct mouse granulocyte-macrophage colony stimulating factor (mGM-CSF) gene eukaryotic expressing plasmid pcDNA3-GM-CSF, to transfect the recombinant into erythroleukemia cell line FBL-3, and identify their biological activity.Methods GM-CSF gene eukaryotic expressing plasmid was constructed by subclone and recombinant was transfected into FBL-3 cells by electroporation. After screening by G418 and cloning by limiting dilution,we obtained positive cell clones(FBL-3-GM-CSF). PCR and RT-PCR were used to identify the integration and stable expression of GM-SF gene in FBL-3-GM-CSF cells. The biological activity was confirmed by the hematopoietic progenitor cell proliferative assay and hematopoietic progenitor cell colony formation assay. Results Mouse GM-CSF cDNA was amplified from the prokaryotic expressing plasmid PET-30a(+)-GM-CSF by PCR firstly and BamH Ⅰ and EcoRⅠrestriction sites were introduced. The inserted fragment was cut by BamH Ⅰ and EcoR Ⅰ digestion and ligated into pcDNA3 vector. The pcDNA3-GM-CSF eukaryotic expressing plasmid was constructed. The recombinant was cleared with appropriate endoneucleases and sequenced. The findings showed that the orientation of the insert was correct, while no rearrangement or mutation was found. PCR and RT-PCR assay showed that GM-CSF gene had integrated into FBL-3-GM-CSF cells and stably expressed. The hematopoietic progenitor cell proliferative assay and hematopoietic progenitor cell colony formation assay demonstrated that the cultured supernatant of FBL-3-GM-CSF cells of expressing GM-CSF should obviously stimulate proliferation of murine marrow mononuclear cells, and could stimulate hematopoietic progenitor cell colony formation. The number of colony formation was 54.67±4.83. The rate of colony formation was 0.547 %.Conclusions GM-CSF gene eukaryotic expressing plasmid is constructed successfully. A cell clone, which can express stably GM-CSF gene and possess biological activity,is obtained. Our studies have founded the base for the preparation of GM-CSF gene-modified vaccine of tumor cell and the study of feasibility of immune therapy of leukemia.