Histopathologic evaluation of subcutaneous xenografts suggested that arresten overexpression affected tumor differentiation in vivo, Arr-HSC tumors containing more often keratinized areas and keratin pearls than Ctrl-HSC tumors. The clear membranous E-cadherin staining was localized around these keratinized areas. The ECIS experiments and modeling also supported our notion that HSC-3 cells form tighter cell-cell and cell-substrate PI3Kα inhibitor 1 manufacturer contacts in the presence of arresten. The loss or down-regulation of cell-cell adhesion is crucial for the cells to metastasize, and it is considered to be one of the key features of EMT. EMT-like changes are reversible, however, and thus the cells can restore their non-motile epithelial characteristics in the MET process. Approximately a 2- fold excess of E-cadherin in A431 human epidermoid carcinoma cells has been shown inhibit their invasion which is in line with the degree of E-cadherin up-regulation induced by arresten in our experiments. Our data therefore suggest that carcinoma cells undergo changes resembling MET in the presence of arresten. Arresten mediates its effects on endothelial cells through integrin receptors. Arresten is known to bind to a1b1 integrin and this ligation is shown to lead to the inhibition of focal adhesion kinase /c-Raf/MEK1/2/p38/ERK1 mitogen-activated protein kinase pathway and suppression of endothelial cell migration, proliferation, and tube formation. Integrin a1 is also required for the order 160807-49-8 anti-survival effect of arresten in endothelial cells. Using ECIS measurements we showed here that the high impedance of Arr-HSC cells was reduced upon treatment with the function-blocking a1 integrin antibody. These data suggest that a1b1 integrin mediates the promoting effect of arresten on HSC-3 cell-cell contacts and cell spreading that are disturbed upon antibody binding. Blocking of a2b1 integrin receptor had a strong inhibitory effect on both the Arr-HSC and the Ctrl-HSC cell attachment suggesting that this receptor mediates interactions that do not involve arresten. Thus, the upregulation of E-cadherin on cell-cell junctions and the concomitant less invasive behavior may be linked to modulation of integrin a1b1 signalling by arresten. The manipulation of b1 integrin and subs
