Tumor necrosis factor alpha and interleukin 1 alpha induce anchorage independence in v-jun transgenic murine cells

The oncogene jun encodes a transcription factor of the AP-1 family. In mice carrying viral jun (v-jun) as a transgene, wounding is a prerequisite for tumorigenesis, suggesting collaboration between the transgene and a wound-related event. To define possible candidates for this collaborative process, we examined the effect of several wound-related polypeptide growth factors on cells from transgenic mice. Tumor necrosis factor alpha and interleukin 1 alpha induce anchorage independence in embryo fibroblasts and tumor cell revertants from these mice. This effect was specific for the two cytokines and was restricted to cells from v-jun transgenic mice. Anchorage independence required the continued presence of the cytokines. Transfection of transgenic cells with a v-jun expression plasmid also induced anchorage independence and a tumorigenic phenotype in transgenic tumor cell revertants. However, there was no correlation between anchorage independence, expression of Jun, and AP-1 activity. These results suggest that while increased transgene expression can enhance the growth properties of v-jun transgenic cells, there exist other cytokine-dependent mechanisms that have a similar effect. Retinoic acid, dexamethasone, or forskolin inhibits induction of anchorage independence by tumor necrosis factor alpha, interleukin 1 alpha, and transfected v-jun. Although these agents affect both AP-1 transactivation potential and DNA binding in the transgenic cells, the changes are not correlated with the inhibition of growth.