Growth factor modulation of metastatic lung colonization.

Altered production and response to growth factors is often involved in neoplasia but little is known about their effect on the dissemination of tumors. Therefore, we have examined the effect of growth factors on metastatic lung colonization. Autocrine induction of the metastatic phenotype was demonstrated in NIH-3T3 cells transformed by a signal peptide-bFGF gene but not bFGF in the absence of the signal peptide. In addition, exogenous growth factor regulation of metastasis was demonstrated. Treatment of ras transformed C3H-10T 1/2 cells and ras or src transformed NIH-3T3 cells with bFGF prior to intravenous injection resulted in potent inhibition of metastatic potential. Stimulation of v-fms transformed cells by the natural fms-ligand, CSF-1, resulted in potent stimulation of metastatic behavior in freshly plated or refed cells, whereas following autocrine conditioning of the medium, the metastatic properties of these cells were sensitive to inhibitory effects of CSF-1. These observations indicate that specific growth factors can regulate the metastatic phenotype and, depending on the oncogenes responsible for cell transformation and autocrine conditioning, these effects can be either stimulatory or inhibitory.