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COOH-terminal-modified interleukin-3 is retained intracellularly and stimulates autocrine growth
C E Dunbar1, T M Browder, J S Abrams
1Clinical Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD 20892.
Abstract:
Autocrine growth due to dysregulated growth factor production may have a role in the development of neoplasia. Whether autocrine growth is stimulated by growth factor secretion in an autocrine loop or by intracellular binding of the growth factor to a receptor has been unclear. The carboxyl-terminus coding sequence for murine interleukin-3 (IL-3) was extended with an oligonucleotide encoding a four-amino acid endoplasmic reticulum retention signal. IL-3-dependent hematopoietic cells became growth factor-independent when the modified IL-3 gene was introduced by retroviral gene transfer, despite lack of secretion of the modified IL-3. Hence autocrine growth can occur as a result of the intracellular action of a growth factor and this mechanism may be important in neoplastic and normal cells.