Retroviral-mediated gene expression in human myelomonocytic cells: a comparison of hematopoietic cell promoters to viral promoters.

Gene transfer into human hematopoietic stem cells with expression targeted to the maturing myelomonocytic progeny has applications for gene therapy of genetic diseases affecting granulocytes and macrophages. We hypothesized that promoters of myeloid-specific genes that are upregulated with myelomonocytic differentiation would also upregulate expression of an exogenous gene in a retroviral vector. Moloney murine leukemia virus (MoMuLV)-based retroviral vectors using promoters from hematopoietic genes (CD11b, CD18, and CD34) were compared with vectors with viral promoters (MoMuLV long terminal repeat [LTR], cytomegalovirus [CMV], and simian virus 40 [SV40]). Human glucocerebrosidase (GC) cDNA was the reporter gene. HL60 cells were transduced with these vectors and vector-derived GC activity was compared in undifferentiated HL-60 cells and the same cells differentiated into granulocytes using dimethyl sulfoxide or monocyte/macrophages using phorbol myristate acetate. In undifferentiated HL-60 cells, vector-derived GC activity was the highest when it was controlled by the MoMuLV LTR. In HL-60 cells differentiated into granulocytes, vector-derived GC activity transcribed from the CD11b, MoMuLV LTR, and CMV promoters was equivalent to 1.7, 1.5, and 1.5 times the normal endogenous GC activity, respectively, and 0.8, 2.0, and 3.6 times the normal GC activity, respectively, in those differentiated into macrophages. With granulocytic differentiation, the CD11b promoter showed maximal induction in GC activity (8-fold); with macrophage differentiation, the CD11b promoter showed a fourfold induction in GC expression. The CD11b promoter also generated significant levels of GC activity in the myelomonocytic progeny of transduced CD34+ cells. Expression from the CD11b promoter, unlike that from the CMV or the MoMuLV LTR promoters, was relatively myelomonocyte-specific, with minimal expression observed in Jurkat T cells or HeLa carcinoma cells. The induction of expression from the CD11b promoter with differentiation in HL-60 cells correlates with the developmental regulation of the CD11b gene. Retroviral vectors using the CD11b promoter have potential utility for gene therapy of disorders affecting the myelomonocytic lineage.