Altered biochemical properties of actin in normal skin fibroblasts from individuals predisposed to dominantly inherited cancers.

The data presented here show that normal skin fibroblasts from individuals with dominantly inherited retinoblastoma, polyposis coli, and nevoid basal cell carcinoma (predisposed cells), grown in the presence of [35S]methionine, contain more than 2.5-fold [35S]methionine-labeled actin as compared to normal fibroblasts from individuals without a prior history of predisposition to cancer (normal cells). The rate of incorporation of [35S]methionine into actin in predisposed cells is rapid and is not correlated with an increase in the total protein and actin contents of the cells, in the intracellular pool size of [35S]methionine, or in the synthesis of beta-actin-specific mRNA, as compared to normal cells. However, the half-life of actin in predisposed cells is less than 5 h, as compared to at least 48 h for normal cells. The significantly reduced half-life of actin and an increased incorporation of [35S]methionine specifically into actin in all predisposed cells studied may represent an inherited biochemical defect which leads to cytoskeletal disorganization previously observed in these cells. It can be speculated that the altered properties of actin in predisposed cells may be caused by the same genetic lesion(s) which is responsible for the induction of dominantly inherited cancers.