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SW Chung, PM Wong, G Shen-Ong, S Ruscetti, T Ishizaka and CJ Eaves
We have recently described a system that supports the development of
continuously growing and tumorigenic cell lines after infection of
individual multilineage hematopoietic colonies with Abelson murine leukemia
virus (A-MuLV). We now provide definitive evidence that these transformed
lines express features characteristic of mast cells. Although these lines
have been maintained in some cases for more than a year in the absence of
exogenous growth factors other than those present in fetal calf serum,
colony formation could consistently after 2 months, and variably after 5
months, be shown to be increased several fold when pokeweed
mitogen-stimulated spleen cell conditioned medium (CM) was added to the
cultures. CM from the A-MuLV-transformed lines was then tested for its
ability to stimulate hematopoietic colony formation by cells from both
fetal and adult tissues. Four of four randomly selected cell lines produced
factors that were active on erythropoietic, granulopoietic, and in some
cases pluripotent progenitors. Removal of viral particles from the CM from
one of the lines (27d1) by either heat inactivation or high-speed
centrifugation did not alter the colony-stimulating activity detected. When
CM from 27d1 cells was tested for its ability to stimulate the
proliferation of interleukin 3 (IL3) granulocyte-macrophage
colony-stimulating factor (GM-CSF)-dependent FDC-P1 cells, a positive
result was obtained. This stimulatory activity was not reduced in the
presence of neutralizing anti-IL 3 immunoglobulin (Ig), suggesting that the
activity detected was GM-CSF and not IL 3. This was confirmed by the lack
of expression of the IL 3 gene in 27d1 cells as determined by Northern
analysis of 27d1 cell RNA. Furthermore, S1 analysis of mRNA from 27d1 cells
as well as two other lines indicated that the GM-CSF gene in all three was
transcriptionally active. Taken together, these data suggest that A- MuLV
transformation of normal mast cells or their precursors under certain
conditions commonly activates the production of GM-CSF.
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| Copyright © 1986 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||