Analysis of actin microfilaments and cell-to-substrate adhesive structures in human fibroblasts from individuals genetically predisposed to colonic carcinoma

Abstract

Skin fibroblasts from patients with inherited adenomatosis of the large bowel (ACR-SF) possess alterations in actin microfilament (MF) organization which serve to distinguish “predisposed” cells from fibroblasts derived from normal individuals (NSF). MF bundle frequency and diameter were considerably reduced in ACR-SF compared to NSF. This deficit in MF density correlated with a 60% decline in cytoskeletal-associated actin half-life. Absence of a well-structured MF network in ACR-SF was reflected in relatively poor cell-to-substrate adhesion (as indicated by increased sensitivity to trypsin release) and extensive membrane ruffling. Unlike NSF, ACR-SF failed to develop well-defined vinculin-containing focal contacts although the cellular content of vinculin was approximately the same in both cell types. The relatively low substrate adhesivity and reduced incidence of adhesive structures (i.e., MF and associated focal contacts) which typify ACR-SF correlated with a sixfold increase in cellular plasminogen activator (PA) activity. This increased protease activity corresponded with a 50–70% reduction in the content of the PA inhibitor-like protein p50 in both the saponin-resistant undersurface matrix and the culture medium. Increased motility and reduced cell-to-substrate adhesion, involving several cellular structural elements, appear to be significant correlates of the “predisposed” phenotype in cultured fibroblasts.