The transcriptional programme of contact‐inhibition

Abstract

Proliferation of non-transformed cells is regulated by cell-cell contacts, which are referred to as contact-inhibition. Vice versa, transformed cells are characterised by a loss of contact-inhibition. Despite its generally accepted importance for cell-cycle control, little is known about the intracellular signalling pathways involved in contact-inhibition. Unravelling the molecular mechanisms of contact-inhibition and its loss during tumourigenesis will be an important step towards the identification of novel target genes in tumour diagnosis and treatment. To better understand the underlying molecular mechanisms we identified the transcriptional programme of contact-inhibition in NIH3T3 fibroblast using high-density microarrays. Setting the cut off: >or=1.5-fold, P <or= 0.05, 853 genes and 73 cDNA sequences were differentially expressed in confluent compared to exponentially growing cultures. Importing these data into GenMAPP software revealed a comprehensive list of cell-cycle regulatory genes mediating G0/G1 arrest, which was confirmed by RT-PCR and Western blot. In a narrow analysis (cut off: >or=2-fold, P <or= 0.002), we found 110 transcripts to be differentially expressed representing 107 genes and 3 cDNA sequences involved, for example, in proliferation, signal transduction, transcriptional regulation, cell adhesion and communication. Interestingly, the majority of genes was upregulated indicating that contact-inhibition is not a passive state, but actively induced. Furthermore, we confirmed differential expression of eight genes by semi-quantitative RT-PCR and identified the potential tumour suppressor transforming growth factor-beta (TGF-beta)-1-induced clone 22 (TSC-22; tgfb1i4) as a novel protein to be induced in contact-inhibited cells.

Cell density-dependent stimulation of PAI-1 and hyaluronan synthesis by TGF-β in orbital fibroblasts

“…Contact inhibition of proliferation is typical of non-transformed cells (Küppers et al 2010) and is considered to be continuously active, regulating cell proliferation and organ size in adult tissues (Zeng & Hong 2008). Therefore, we have hypothesized that confluent cultures correspond to the healthy orbit, whereas pre-confluent cultures represent the expanding, high ECM orbital tissue with higher fibroblast proliferation rate.…”

Cell Density-dependent Nuclear Accumulation of ELK3 is Involved in Suppression of PAI-1 Expression

“…Several studies have shown that fibroblasts, which are typical non-transformed cells, exhibit growth arrest at high cell density (Levine et al, 1965;Eagle and Levine, 1967). For example, at high cell density, NIH/ 3T3 cells, which are mouse embryonic fibroblasts, exhibit limited proliferation and migration at high cell density, coupled with the activation of anti-proliferative signals and subsequent cell cycle arrest at the G0/G1 phases (Holley and Kiernan, 1968;Küppers et al, 2010). Vascular endothelial cells, upon contact with neighboring cells, impair cell proliferation and cell differentiation by the activation of Notch signaling during angiogenesis and embryogenesis (Augustin et al, 1994;Eiraku et al, 2005).…”

Regulation of gene expression by tobacco product preparations in cultured human dermal fibroblasts

“…As fibroblasts reach confluence, they undergo contact inhibition, a directional inhibition of movement and proliferation that occurs when one fibroblast contacts another (Abercrombie, 1970). It has been shown that gene expression in cells may differ between proliferating versus confluent cultures (Kuppers et al, 2010). Sorrell and Caplan (2004) suggest that studies using monolayers of fibroblasts more closely reflect the status of these cells in an “early wound repair situation”.…”