Distinct Effect of Retroviral-Mediated IFN-alpha Gene Transfer on Human Erythroleukemic and CD34 + Cell Growth and Differentiation

Human interferon-alpha (IFN-alpha) has been used in the management of leukemia, but its diverse adverse effects may influence the ability of IFN-alpha to treat this disease. We constructed two retroviral vectors, LSN-IFN-alpha and LNC-IFN-alpha, in which IFN-alpha cDNA was driven by viral LTR and CMV promoters, respectively. After transduction into the PA317 and PG13 retroviral packaging cells, high titers of retrovirus were produced and were used to infect K562 and human BM CD34⁺ hematopoietic cells. The IFN-alpha gene expression in transduced K562 cells was confirmed by Northern blot, RTPCR, RIA, and biologic assay. Cell proliferation and cell viability in IFN-alpha-transduced K562 cells were significantly suppressed as compared with control K562 cells. Although the IFN-alpha expression in K562 cells did not affect BCR/ABL expression, it apparently upregulated the production of adhesion molecules (VLA-4 and Mac-1). We evaluated the effect of IFN-alpha gene transfer on human CD34⁺ cells infected with LSN-IFN-alpha retrovirus with the aid of fibronectin (FN) fragment CH-296 and growth factors. RIA showed that IFN-alpha-transduced CD34⁺ cells produced 72.2 +/- 15 U/ml of IFN-alpha compared with 4.3 +/- 1.2 U/ml in control CD34⁺ cells. Methylcellulose clonogenic assay indicated that IFN-alpha-transduced CD34⁺ cells produced similar numbers of burst-forming units-erythrocytes (BFU-E)/colony-forming units-GM (CFU-GM) colonies as compared with control CD34⁺ cells. Selected colonies expressed IFN-alpha and neo^r mRNA, as measured by RT-PCR. These studies indicate that retrovirus-mediated IFN-alpha gene transfer may provide a useful tool for studying the effect of IFN-alpha gene transfer on leukemic cells and long-lived CD34⁺ cells.