DLC1 deficiency and YAP signaling drive endothelial cell contact inhibition of growth and tumorigenesis

The possibility that contact inhibition of growth in cultures of human diploid cells is influenced by the effects of cell crowding on nutrient uptake by the cells was investigated. Two human lung cell lines were compared, the diploid line MRC-5 and the heteroploid line L-132. In pre-confluent cultures the ability of these 2 cell types to accumulate amino acids was very similar. Post-confluent L-132 cells showed very little change from the pre-confluent cultures but the ability of MRC-5 cells in post-confluent cultures was greatly reduced. The intracellular concentrations of various amino acids necessary to achieve the maximum rate of protein synthesis were found. These values were identical for sparse and crowded cultures but due to the reduced uptake ability of crowded MRC-5 cells a far higher external amino acid concentration was required in post-confluent cultures. This meant that although amino acids did not become growth-limiting until over 80% utilized in pre-confluent cultures, in post-confluent cultures they became growth-limiting when only 50% utilized. Although protein synthesis was significantly affected by extracellular amino acid concentration and cell crowding, thus contributing towards the effect of contact inhibition of growth, DNA synthesis was shown to be the major metabolic function in contact inhibition. Increased cell density had a very inhibitory effect on DNA synthesis in MRC-5 cultures, but not in L-132 cultures, and this was unaffected by extracellular amino acid and glucose concentration.

Download Full-text

Monocytes Upregulate Endothelial Cell Expression of Tissue Factor: A Role for Cell-Cell Contact and Cross-Talk

Blood ◽

10.1182/blood.v89.2.541 ◽

1997 ◽

Vol 89 (2) ◽

pp. 541-549 ◽

Cited By ~ 80

Author(s):

Emanuela Napoleone ◽

Angelomaria Di Santo ◽

Roberto Lorenzet

Keyword(s):

Endothelial Cell ◽

Tissue Factor ◽

Cross Talk ◽

Umbilical Vein ◽

Cell Types ◽

Cell Contact ◽

Tnf Α ◽

Factor Α ◽

Cell Expression ◽

Cell Cell

Abstract Monocytes and endothelial cells interact at sites of vascular injury during inflammatory response, thrombosis, and development of atherosclerotic lesions. Such interactions result in modulation of several biological functions of the two cell types. Because both cells, on appropriate stimulation, synthesize tissue factor (TF), we examined the effect of human umbilical vein endothelial cell (HUVEC)/monocyte coculture on the expression of TF. We found that the coincubation resulted in TF generation, which was maximal at 4 hours, increased with increasing numbers of monocytes, and required mRNA and protein synthesis. Supernatant from HUVEC/monocyte coculture induced TF activity in HUVECs, but not in monocytes, indicating that HUVEC were the cells responsible for the activity, and that soluble mediators were involved. Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), well-known inducers of TF in HUVECs, were found in the supernatant from the coculture, and specific antibodies directed against either cytokine inhibited TF generation. The need of IL-1β and TNF-α synthesis in order to elicit TF expression was also suggested by the delay observed in TF mRNA formation and TF activity generation when monocytes were incubated with HUVECs. IL-1β and TNF-α antigen levels in the coculture supernatant, and, consequently, HUVEC TF expression, were inhibited in the presence of anti-CD18 monoclonal antibody. These findings emphasize the role of cell-cell contact and cross-talk in the procoagulant activity, which could be responsible for the thromboembolic complications observed in those vascular disorders in which monocyte infiltration is a common feature.

Download Full-text