Activation of Focal Adhesion Kinase in Detached Human Epidermal Cancer Cells and Their Long-term Survival Might be Associated with Cell Surface Expression of Laminin-5

H Katayama, Y Yamane, Y Furukawa, S Kitagawa, Y Nakamura, K Yoshino
2008 Acta Dermato-Venereologica  
While normal epithelial cells are anchorage-dependent, cancer cells are anchorage-independent. To elucidate the mechanism underlying the anchorage-independence of cancer cells, we cultured detached cells in medium containing elastase. Detached human epidermal cancer cells (DJM-1) survived for at least 3 weeks and focal adhesion kinase was still phosphorylated. In contrast, most detached keratinocytes underwent rapid apoptosis and focal adhesion kinase was not phosphorylated while the cells were
more » ... hile the cells were alive. Thus, discontinuation of the phosphorylation of focal adhesion kinase preceded cell death. Immunostaining showed laminin-5 expression on the surface of detached DJM-1 cells, but not on detached keratinocytes. Receptors for laminin-5 (i.e. integrins) were detected on both detached DJM-1 cells and keratinocytes. Laminins are secreted proteins, so we speculated that laminin-5 adhered to the surface of secreting DJM-1 cells via integrins and evoked activation of focal adhesion kinase, with the resultant signalling cascade promoting cellular survival. If this hypothesis is correct, cell surface expression of laminin-5 may be used to explain the characteristics of cancer, immortality, tumour formation, metastasis and angiogenesis.
doi:10.2340/00015555-0405 pmid:18311433 fatcat:whefydzxrng7dk2i4caa5xn2bq