DISSOCIATION OF RAS ONCOGENE-INDUCED CONE EXPRESSION AND ANCHORAGE-INDEPENDENT GROWTH IN A SERIES OF SOMATIC-CELL MUTANTS

The mechanism or mechanisms by which ras oncogenes induce morphologica l transformation and anchorage-independent growth are poorly understoo d but are thought to involve stable alterations in gene expression. We previously described a genetically dominant, mutant rat fibroblast ce ll line (ER-1-2) that is resistant to ras-induced anchorage-independen t growth. We now describe a cell line derived from ER-1-2 cells, terme d ER-1-2T, that has apparently sustained a second, dominant mutation t hat conferred on these cells the ability to form colonies in soft agar . Analysis of these and control cell lines demonstrated that deregulat ion of many of the genes commonly associated with the transformed phen otype could be dissociated from anchorage-independent growth. After in fection with a ras-expressing retrovirus, bath control and ER-1-2 cell lines constitutively expressed elevated levels of the c-jun, junB, fo sB, c-myc, collagenase, ornithine decarboxylase, osteopontin, stromely sin, cathepsin L, and insulin-like growth factor 1 genes. These data i ndicate that signaling events downstream of ras were largely intact in ER-1-2 cells and that the defect in these cells lies either on a path way separate from those that control stable, ras-mediated expression o f these genes or at a point in the cell-division cycle distinct from t hose that control expression of the genes. In contrast, only c-jun, ju nB, c-myc, and ornithine decarboxylase were expressed at a significant ly elevated level in ER-1-2T cells. Thus, deregulated expression of th e genes analyzed was not sufficient for anchorage-independent growth. Furthermore, deregulation of most of them was also not necessary. (C) 1996 Wiley-Liss, Inc.