Augmentation of in vivo growth of Lewis lung carcinoma cells transduced with granulocyte macrophage-colony stimulating factor gene

Cloned high-metastatic Lewis lung carcinoma. All cells were retrovirally transduced with either granulocyte macrophage-colony stimulating factor (GM-CSF) or β-galactosidase gene and examined for their tumorigenicity, GM-CSF-engineered All cells produced a much higher amount of GM-CSF than the parental and control cells. Unexpectedly, GM-CSF-engineered All cells grew more rapidly than the control cells, while in vitro growth rates of these cells were almost the same. The enhanced tumor growth seemed to be unique to GM-CSF among various cytokines, because interleukin 2 (IL-2), interleukin 4 (IL-4) and interleukin 6 (IL-6) producer cells exhibited suppressed tumor growth.