Figure 8. OPN isoform-expressing cells differ in cell detachment phenotypes that can be modulated by the MET oncogene.

A. Significant cell detachment was observed for OE33/OPNc-expressing cells. OE33/OPN stable cells were seeded in culture dishes at 80% confluence (0.22 × 10⁶ cells/ml in 6-well plates) for 24 h, transfected with lipofectamine alone (mock) or siNonTarget (siNT) or untreated for 96 h and then fixed and stained with Diff-Quik staining solution. While OPNb-expressing cells demonstrated adherence to culture dishes, OPNc cells were significantly detached, as exhibited by markedly increased non-stained areas in culture dishes (see also Figure S4A). B. OE33 cells harbor both MET and ERBB2 gene amplification with corresponding gene overexpression (see Figure S4C). Silencing of MET using siRNA enhanced OE33/OPNc cell detachment while knockdown of ERBB2 did not alter its existing phenotype. Expression of both OPNa and b in OE33 cells appeared to increase adhesion of these cells, as control LacZ cells exhibited increased detachment following transfection with 10 nM siMET or co-transfection with 5 nM each siMET and siERBB2 as compared to transfection with 10 nM siERBB2 alone. C. Silencing of MET resulted in significant detachment of OPNia-expressing cells but did not change the phenotypes of OPNib or OPNic-expressing cells as compared to their full-length OPN counterparts treated with siMET.