Resistance to the mTOR-inhibitor RAD001 elevates integrin alpha2- and beta1-triggered motility, migration and invasion of prostate cancer cells
British Journal of Cancer,
Tsaur I et al. – Chronic RAD001 treatment caused resistance development characterised by distinct modification of the integrin-expression profile, driving prostate cancer cells towards high motility.Methods
- Metastatic potential of PC3 prostate cancer cells, susceptible (PC3par) or resistant (PC3res) to the mTOR-inhibitor RAD001 was investigated. Adhesion to vascular endothelium or immobilised collagen, fibronectin and laminin was quantified.
- Motility, migration and invasion were explored by modified Boyden chamber assay.
- Integrin alpha and beta subtypes were analysed by flow cytometry, western blotting and real-time PCR.
- Integrin-related signalling, EGFr, Akt, p70S6kinase and ERK1/2 activation were determined.
- Adhesion was reduced, whereas motility, migration and invasion were enhanced in PC3res.
- The alpha2 and beta1 integrin subtypes were dramatically elevated, integrins alpha1 and alpha6 were lowered, whereas alpha5 was nearly lost in PC3res.
- Activation of the Akt signalling pathway was strongly upregulated in these cells.
- Treating PC3par cells with RAD001 reduced motility, migration and invasion and deactivated Akt signalling.
- Blocking studies revealed that alpha2 and beta1 integrins significantly trigger the motile behaviour of the tumour cells.