A glycosylation-deficient endothelial cell mutant with modified responses to transforming growth factor-beta and other growth inhibitory cytokines: evidence for multiple growth inhibitory signal transduction pathways.

Abstract

An endothelial cell line (M40) resistant to growth inhibition by transforming growth factor-beta type 1 (TGF beta 1) was isolated by chemical mutagenesis and growth in the presence of TGF beta 1. Like normal endothelial cells, this mutant is characterized by high expression of type II TGF beta receptor and low expression of type I TGF beta receptor. However, the mutant cells display a type II TGF beta receptor of reduced molecular weight as a result of a general defect in N-glycosylation of proteins. The alteration does not impair TGF beta 1 binding to cell surface receptors or the ability of TGF beta 1 to induce fibronectin or plasminogen activator inhibitor-type I production. M40 cells were also resistant to growth inhibition by tumor necrosis factor alpha (TNF alpha) and interleukin-1 alpha (IL-1 alpha) but were inhibited by interferon-gamma (IFN gamma) and heparin. These results imply that TGF beta 1, TNF alpha, and IL-1 alpha act through signal transducing pathways that are separate from pathways for IFN gamma and heparin. Basic fibroblast growth factor was still mitogenic for M40, further suggesting that TGF beta 1, TNF alpha, and IL-1 alpha act by direct inhibition of cell growth rather than by interfering with growth stimulatory pathways.

Expression of a dominant negative type II TGF-β receptor in mouse skin results in an increase in carcinoma incidence and an acceleration of carcinoma development

“…This compares well to the mass of the amino acids of the truncated receptor plus glycosylation to the same extent as it had been described for the wild type receptor (Lin et al, 1992). Correct glycosylation seems to be important for the functionality of the type II receptor (Fafeur et al, 1993). In both transgenic lines the dominant negative type II receptor interferes with TGF-b signaling in primary keratinocytes.…”

Transforming Growth Factor-β (TGF-β)-induced Down-regulation of Cyclin A Expression Requires a Functional TGF-β Receptor Complex

“…Also, a Phe to Ala mutation at position 498 in RII does not affect the induction of transcription by TGF-␤, yet reduces significantly its antiproliferative effect (60). In addition, several cell lines lacking detectable levels of RII expression or with a defective RII display TGF-␤ responsiveness in gene expression assays but are not growth inhibited by TGF-␤ (53,70). Furthermore, various tumor cell lines also lack a growth inhibitory response to TGF-␤ yet respond to TGF-␤ by the induction of gene expression (52).…”

“…These findings support the notion that the two receptors are needed for both types of responses to TGF-␤. However, separate signaling pathways for the two types of responses have been observed in several studies (51)(52)(53). For example, cells in which the type II receptor has been functionally inhibited by a truncated type II receptor are resistant to the antiproliferative effect of TGF-␤, yet still induce the expression of PAI-1 and other gene products (51).…”

“…Ref. 53), are resistant to TGF-␤-induced antiproliferation, but remain able to induce various genes including PAI-1 in response to TGF-␤ (see "Discussion").…”

Signaling Mechanisms of Transforming Growth Factor-β (TGF-β) in Cancer: TGF-β Induces Apoptosis in Lung Cells by a Smad-Dependent Mechanism

“…Hypermethylation of CpG islands in the promoters of TGF-β RI and TGF-β RII or mutations in the TGF-β RII promoter that interfere with transcription factor binding may also result in transcriptional silencing (Amoroso, et al, 1998). Decreased TGF-β RII function results in resistance to the growth inhibitory activity of TGF-β, but other TGF-β responses may not be affected in a similar fashion because they may require different levels of signaling (Chen et al, 1993;Fafeur et al, 1993). The tumor suppressor role of TGF-β RII has been demonstrated by expressing wildtype TGF-β RII in cancer cells that lack a functional TGF-β RII allele (Sun et al, 1994;Wang et al, 1995) or by over-expressing TGF-β RII in vitro (Turco et al, 1999).…”