Transforming growth factor-beta(1) augments granulocyte-macrophage colony-stimulating factor-induced proliferation of umbilical cord blood CD34(+) cells with an associated tyrosine phosphorylation of STAT5.
OBJECTIVE
Several investigators have reported that transforming growth factor (TGF)-beta(1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) synergistically support cell proliferation. However, the mechanisms involved have not been elucidated. To clarify the mechanisms of the synergistic action of TGF-beta(1) and GM-CSF, we compared the activation states of STAT5 and mitogen-activated protein kinase in CD34(+) cells and in GM-CSF-dependent hematopoietic cell lines.


METHODS
Human CD34(+) cells and GM-CSF-dependent cell lines (FKH-1, YNH-1, and M-07e) were stimulated with 1.25 ng/mL GM-CSF and/or 0.25 ng/mL TGF-beta(1), and 1.25 ng/mL GM-CSF and/or 0.25 ng/mL, 0.025 ng/mL TGF-beta(1), respectively, and cell proliferation was analyzed by [3H]thymidine uptake. Expression of signal transduction proteins and their phosphorylation states were determined by Western blotting.


RESULTS
TGF-beta(1) synergistically enhanced the GM-CSF-augmented growth of CD34(+) cells and FKH-1 cells, but inhibited the growth of YNH-1 and M-07e cells. Tyrosine phosphorylation of STAT5 induced by GM-CSF was enhanced by stimulation with the combination of TGF-beta(1) and GM-CSF (TGF-beta(1)/GM-CSF) compared with that induced by GM-CSF alone in CD34(+) cells and FKH-1 cells. However, combinations of TGF-beta(1)/GM-CSF caused inhibition of GM-CSF-induced tyrosine phosphorylation in M-07e cells. No significant difference was observed in mitogen-activated protein kinase activation between CD34(+) cells and FKH-1 cells stimulated with GM-CSF/TGF-beta(1) or GM-CSF alone.


CONCLUSIONS
Results suggest that TGF-beta(1) may augment GM-CSF-induced proliferation of CD34(+) cells in association with enhanced tyrosine phosphorylation of STAT5. Our data suggest a novel mechanism for the synergistic enhancement of cellular growth induced by the combination of TGF-beta(1) and GM-CSF.
Suzuki
Motoyuki
M
Fujisaki Cell Center, Hayashibara Biochemical Laboratories, Inc., Okayama, Japan. fcch@hayashibara.co.jp
Harashima
Akira
A
Okochi
Ayumi
A
Yamamoto
Mayuko
M
Matsuo
Yoshinobu
Y
Motoda
Ryuichi
R
Yoshioka
Tamotsu
T
Orita
Kunzo
K
D015703:Antigens, CD / Q000097:blood; D018952:Antigens, CD34 / Q000097:blood; D002455:Cell Division / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D005312:Fetal Blood / Q000166:cytology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D007231:Infant, Newborn; D008894:Milk Proteins; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000187:drug effects / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D015703:Antigens, CD; D018952:Antigens, CD34; D004268:DNA-Binding Proteins; D008894:Milk Proteins; D011994:Recombinant Proteins; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D019000:Phosphotyrosine; D016178:Granulocyte-Macrophage Colony-Stimulating Factor