Cytoarchitecture of ras oncogene-expressing tumor cells: butyrate modulation of substrate adhesion, cytoskeletal actin content and subcellular microfilament distribution.

1. The subcellular distribution of particular cytoskeletal (CSK) and cell-substrate adhesive elements was assessed during the morphologic response of cultured tumor cells to the shape modulating agent sodium butyrate (NaB). 2. NaB induced marked increases in cellular and CSK actin content and in the matrix-associated proteins fibronectin and p52. 3. Subcellular fractionation indicated disproportionate increases in the actin content of the substrate-attached cellular residue (SAM fraction) which contains the majority of cell-substrate adhesive elements. 4. Augmented cell spreading and substrate attachment characteristic of NaB-treated cells is likely due to increased elaboration of cell-to-substrate adhesive structures and reflected in an enhanced deposition of actin into the CSK and SAM compartments.