V-K-RAS TRANSFORMATION INDUCES REVERSION TO AN EARLIER DEVELOPMENTAL FORM IN ADULT-RAT ADRENAL-CELLS

The basis for specific changes in differentiation that accompany ras-oncogene-mediated transformation are not understood. When short-term cultures of fibroblast-like cells from adult rat adrenal glands were transformed with Kirsten murine sarcoma virus (Ki-MSV), the original stromal characteristics of the target cells (metachromatic extracellular matrix, high collagen production, collagen incorporation into pericellular matrix and a fibroblastic morphology and growth pattern) diminished. In contrast, parenchymal differentiation markers (neutral lipid, Δ 5, 3β-hydroxys-teroid dehydrogenase, 21-hydroxylase and epithelial morphology) were enhanced. These changes in differentiation were initiated concurrently with the over-expression of the transforming protein v-p21, but were unrelated to the levels of v-p21 expression. They were independent of the immortalizing component of transformation mediated by v-K-ras, because they did not take place in spontaneously immortalized lines derived from the same target cells, unless the lines were also transformed with Ki-MSV. In normal embryonic development, stromal and parenchymal adrenocortical cells arise by divergent differentiation pathways from a common, multipotential mesenchymal precursor. The transformation-induced modulation from a predominantly stromal to a more-parenchymal phenotype is thus reminiscent of reversion to a more primitive, bipotential developmental stage. © 1990, International Society of Differentiation. All rights reserved.