Role of Protein Kinase C in Expression of Granulocyte Colony Stimulating Factor and Granulocyte-Macrophage Colony Stimulating Factor in Lung Cancer Cells.

Many cases of tumors that produce granulocyte-colony stimulating factor (G-CSF) or granulocyte macrophage-colony stimulating factor (GM-CSF) have been reported. However, the biological properties regulatory mechanisms of the overproduction of G-CSFor GM-CSF by tumor cells are not well known. We present the role of protein kinase C (PKC) pathways in the constitutive expression of G-CSF and GM-CSF by lung cancer cells. We previously established two lung cancer cell lines, OKa-C-1 and MI-4, that constitutively produce an abundant dose of G-CSF and GM-CSF. We showed that the PKC activator; phorbol 12-myristate 13-acetate (PMA) stimulated the production of GM-CSF in a dose-dependent manner and inversely reduced G-CSF in the cell lines. These effects of PMA were antagonized by PKC inhibitor; staurosporine. The induction of GM-CSF expression by PMA was mediated through the activations of nuclear factor (NF)-kB activation. The induction of G-CSF expression by staurosporine was mediated through p44/42 mitogen-activated protein kinase (MAPK) pathway signaling. PMA accelerated cell growth and inhibited cell death in the cell line. Whereas staurosporine acted inversely. GM-CSF induced by PMA might stimulate cell growth and suppress cell death. G-CSF expression by staurosporine appears to be related to the activation of p44/42 MAPK, and GM-CSF by PMA to NF-kB in OKa-C-1 and MI-4 cells.

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