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


CONCLUSIONS
Our data identifies integrin β1 as a part of the osmosensing machinery and regulator of cisplatin resistance in adherent Ehrlich cells.
Department of Biology, Section of Cell and Developmental Biology, The August Krogh Building, University of Copenhagen, Copenhagen Ø, Denmark.
Belinda Halling
BH
Sørensen
Line Jee Hartmann
LJ
Rasmussen
Bjørn Sindballe
BS
Broberg
Thomas Kjær
TK
Klausen
Daniel Peter Rafael
DP
Sauter
Ian Henry
IH
Lambert
Anders
A
Aspberg
Else Kay
EK
Hoffmann
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D002286:Carcinoma, Ehrlich Tumor / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D005353:Fibronectins / Q000378:metabolism; D019012:Integrin beta1 / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D009995:Osmosis; D013654:Taurine / Q000378:metabolism; D000093542:Gemcitabine
D000970:Antineoplastic Agents; D005353:Fibronectins; D019012:Integrin beta1; D003841:Deoxycytidine; D013654:Taurine; D020169:Caspases; D002945:Cisplatin; D000093542:Gemcitabine