Abstract
The effects of acute hypoxia on integrin expression and adhesion to extracellular matrix proteins were investigated in two human melanoma cell lines, HMB-2 and DX3, and a human adenocarcinoma cell line, HT29. Exposure to hypoxia caused a significant down-regulation of cell surface integrins and an associated decrease in cell adhesion. Loss of cell adhesion and integrin expression were transient and levels returned to normal within 24 h of reoxygenation. Other cell adhesion molecules, such as CD44 and N-CAM, were also down-regulated after exposure of cells to hypoxia. Acute exposure to hypoxia of cells at confluence caused rapid cell detachment. Cell detachment preceded loss of viability. Detached HMB-2 and DX3 cells completely recovered upon reoxygenation, and floating cells re-attached and continued to grow irrespective of whether they were left in the original glass dishes or transferred to new culture vessels, while detached HT29 cells partly recovered upon reoxygenation. Cell detachment after decreased adhesion appears to be a stress response, which may be a factor enabling malignant cells to escape hypoxia in vivo, with the potential to form new foci of tumour growth.
Highlights
We report that changes in cell adhesion, brought about by hypoxic stress, occur as a consequence of changes in the expression of cell adhesion molecules in human tumour cell lines
The adhesion of HMB-2, DX3 and HT29 cells to extracellular matrix proteins was tested in initial experiments and it was found that HMB-2 cells adhere mainly to fibronectin and vitronectin, with very little adherence to collagen
DX3 and HT29 cells behaved in a similar way to HMB cells and adhesion to all extracellular matrices tested was reduced in a similar fashion
Summary
Cell cultureHuman cutaneous melanoma (HMB-2) and (DX3) and human adenocarcinoma (HT29) cells were cultured in minimum essential medium (MEM) supplemented with 10% fetal calf serum (FCS), glutamine (5 mM) and penicillin/streptomycin (100 U/100 gg ml-'). Cells were grown on glass dishes for at least 3 days. Glass dishes, without lids, were put in a polypropylene box fitted with an inlet-outlet system and the box was purged with continuous flow (500 ml min-1) of 95% nitrogen, 5% carbon dioxide (BOC) for various periods. This system renders cells radiobiologically hypoxic within 1 h (Stratford et al, 1980; Sutherland et al, 1982), corresponding to an oxygen tension less than 400 p.p.m. Duration of hypoxic exposure was defined from the start of nitrogen purging Duration of hypoxic exposure was defined from the start of nitrogen purging.
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