Granulocyte-macrophage colony-stimulating factor stimulates the metastatic properties of Lewis lung carcinoma cells through a protein kinase A signal-transduction pathway.
Expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) by metastatic Lewis lung carcinoma cells (LLC-LN7) was previously shown to contribute to the maintenance of phenotypic characteristics associated with an increased capacity to metastasize. In the present study, pre-incubation of LLC-LN7 cells with neutralizing anti-GM-CSF antibodies diminished the capacity of the tumor cells to form experimental metastases after i.v. inoculation, while pre-incubation with recombinant GM-CSF (rGM-CSF) increased formation of metastases. In the presence of rGM-CSF, the LLC-LN7 cells exhibited an increased capacity to migrate, invade through a reconstituted basement membrane, and adhere to lung tissue. Studies to identify the signal transduction pathway through which GM-CSF enhanced the in vitro metastatic properties of the LLC-LN7 tumor cells implicated protein kinase A (PKA). Signaling through PKA was suggested by the demonstration that the stimulation of tumor-cell motility by GM-CSF was blocked in the presence of the adenylate cyclase inhibitor nicotinic acid, or the PKA inhibitors A3 or KT5720. In addition, the role of PKA as a signaling mechanism for GM-CSF was assessed by using REV-LN7 cells, which are LLC-LN7 cells that have been stably transfected with an expression vector encoding a mutant PKA RI alpha subunit and which, in turn, express a cAMP-resistant PKA. Adherence and invasion by the PKA-defective REV-LN7 cells were not stimulated by rGM-CSF, contrasting with the stimulation observed for wild-type LLC-LN7 cells. These data suggest that rGM-CSF can further enhance the in vitro metastatic characteristics of LLC-LN7 tumor cells and that this is dependent on signal transduction through PKA.
Young
M R
MR
Department of Research Services, Hines V.A. Hospital, Hines, IL 60141.
Lozano
Y
Y
Djordjevic
A
A
Devata
S
S
Matthews
J
J
Young
M E
ME
Wright
M A
MA
D000818:Animals; D002277:Carcinoma / Q000473:pathology; D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D009374:Neoplasms, Experimental / Q000473:pathology*; D011494:Protein Kinases / Q000502:physiology*; D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D015398:Signal Transduction
D016187:Receptors, Granulocyte-Macrophage Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D011494:Protein Kinases