AUTOCRINE TRANSFORMATION OF HUMAN HEMATOPOIETIC-CELLS AFTER TRANSFECTION WITH AN ACTIVATED GRANULOCYTE MACROPHAGE COLONY-STIMULATING FACTORGENE/

The effects of constitutive cytokine gene expression on the growth-fac tor-dependence of the human erythroleukemic TF-1 cell line have been d etermined. TF-1 cells normally require the presence of exogenous cytok ines to proliferate in vitro. TF-1 cells were transfected with constru cts containing either the germline granulocyte-macrophage colony-stimu lating factor (GMCSF) gene or the GM-CSF gene linked to the Moloney mu rine leukemia virus (Mo-MuLV) long terminal repeat. The Mo-MuLV-LTR, w hich contains a strong transcriptional enhancer, was added to stimulat e the constitutive expression of the GM-CSF gene. Transfection with th e germline GM-CSF gene did not abrogate the cytokine dependence of TF- 1 cells, indicating that inheritance of an extra copy did not result i n sufficient GM-CSF expression to abrogate cytokine dependence. In con trast, transfection with the LTR-modified GM-CSF gene resulted in the isolation of cells that proliferated in the absence of exogenous GMCSF . The LTR increased nascent transcription and accumulation of GM-CSF m RNA transcripts, which had a normal half-life. This increase in GM-CSF expression led to secretion of sufficient GM-CSF to support the growt h of the parental TF-1 cells. These results indicate that the deregula ted expression of human cytokine genes induced by certain retroviral L TRs can result in their conversion into hematopoietic-specific oncogen es. These modified human sell lines provide a model to investigate aut ocrine transformation and therapy of acute myelogenous leukemia as wel l as other hematopoietic disorders.