6533b7d6fe1ef96bd1266431

RESEARCH PRODUCT

Loss of Contact-Dependent Inhibition of Growth in Chemically Transformed Fibroblasts

subject

description

The plasma membrane has been recognized as an important regulatory unit of mammalian cells during determination, differentiation, and social behaviour of individual cells within various tissues (1–4). On the molecular level, plasma membrane glycoproteins and glycolipids have been shown to be involved in these processes (1–4). Density-dependent growth of non-transformed cells in vitro has been proposed to be regulated by secreted inhibitory compounds (5–7), by the cell’s shape (8) or by diffusion boundary layers (9). On the other hand, specific cell-cell interactions via cell membrane molecules were found to be of great importance for the contact-dependent inhibition of growth (10–16) and consequently, to be responsible for the stop of growth of non-transformed cells when a confluent monolayer has been established. Several reports have shown the involvement of glycoconjugates in the control of proliferation by indirect means (11, 14, 17–19). Beyond it, a correlation between altered plasma membrane glycosylation and transformation has been demonstrated by numerous studies (20–22), and has been confirmed by DNA-transfection recently (23, 24). Furthermore, inhibitors of glycoprotein processing enzymes led to the loss of transformed phenotype of transformed fibroblasts (25, 26). These results suggest a causal relationship between glycoprotein structures and tumorigenesis.