Efficient production of biologically active human recombinant proteins in human lymphoblastoid cells from integrative and episomal expression vectors.

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The ability of human lymphoblastoid cells to secrete large amounts of biologically active human hematopoietic growth factors from adenovirus-based expression vectors was investigated. The gene for human erythropoietin (EPO) was inserted into integrative (pTS39) and episomal (pTS53) vectors. Cell clones, originating from pTS39 or pTS53-transfected and stably selected cells, secreted recombinant human EPO (re-hEPO) at similar levels. The highest production, 60 mu/10(6) cells per 24 h, was obtained from a subclone of pTS39-transfected cells, grown in nonselective medium. The re-hEPO was shown to be biologically active in vivo by incorporation of 59Fe into red blood cells of polycythemic mice and in vitro by the proliferative response of the EPO-dependent cell line UT7. The purified protein of 36 kDa in SDS-PAGE slightly differed from re-hEPO from CHO cells. pTS39 vector was integrated at 15-30 copies per genome, whereas the pTS53 vector replicated at 10 copies per cell. Genes encoding human interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) were also expressed in the integrative system as biologically active growth factors, demonstrating that our host-vector system allows the expression of any little gene or cDNA and efficient secretion of the re-protein produced.