Effect of serum deprivation on constitutive production of granulocyte-colony stimulating factor and granulocyte macrophage-colony stimulating factor in lung cancer cells.

We previously established 2 lung cancer cell lines, OKa-C-1 and MI-4, which constitutively produce an abundant dose of granulocyte-colony stimulating factor (G-CSF) and granulocyte macrophage-colony stimulating factor (GM-CSF). Many other cases with G-CSF or GM-CSF producing tumors have been reported up to the present. However, the biological properties of the overproduction of G-CSF and GM-CSF by tumor cells have not been well known. Several reports demonstrated the presence of an autocrine growth loop for G-CSF and GM-CSF in nonhematopoietic tumor cells. We showed that exogenous G-CSF and GM-CSF stimulated cell growth in a dose-dependent manner in OKa-C-1 and MI-4 cells. We could detect the presence of G-CSF and GM-CSF receptors in both cell lines by RT-PCR analysis. We have previously shown that inflammatory cytokines, tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta enhance the expression of G-CSF and GM-CSF in the cell lines. However, the factors that regulate constitutive production of G-CSF or GM-CSF by tumor cells are still unknown well. In our study, we first reported that serum deprivation stimulated constitutive production of G-CSF and GM-CSF by lung tumor cells through activation of nuclear factor (NF)-kappaB and p44/42 mitogen-activated protein kinase (MAPK) pathway signaling. We suggest that G-CSF and GM-CSF constitutively produced by tumor cells could grow tumor itself and rescue tumor cells from the cytotoxicity of serum deprivation.