Integrin β1, Osmosensing, and Chemoresistance in Mouse Ehrlich Carcinoma Cells.

BACKGROUND/AIMS Altered expression of the integrin family of cell adhesion receptors has been associated with initiation, progression, and metastasis of solid tumors as well as in the development of chemoresistance. Here, we investigated the role of integrins, in particular integrin β1, in cell volume regulation and drug-induced apoptosis in adherent and non-adherent Ehrlich ascites cell lines. METHODS Adhesion phenotypes were verified by colorimetric cell-adhesion-assay. Quantitative real-time PCR and western blot were used to compare expression levels of integrin subunits. Small interfering RNA was used to silence integrin β1 expression. Regulatory volume decrease (RVD) after cell swelling was studied with calcein-fluorescence-self-quenching and Coulter counter analysis. Taurine efflux was estimated with tracer technique. Caspase assay was used to determine apoptosis. RESULTS We show that adherent cells have stronger fibronectin binding and a significantly increased expression of integrin α5, αv, and β1 at mRNA and protein level, compared to non-adherent cells. Knockdown of integrin β1 reduced RVD of the adherent but not of the non-adherent cells. Efflux of taurine was unaffected. In contrast to non-adherent, adherent cells exhibited chemoresistance to chemotherapeutic drugs (cisplatin and gemcitabine). However, knockdown of integrin β1 promoted cisplatin-induced caspase activity in adherent cells. CONCLUSION Our data identifies integrin β1 as a part of the osmosensing machinery and regulator of cisplatin resistance in adherent Ehrlich cells.