MET receptor inhibition: Hope against resistance to targeted therapies?

Overcoming the drug resistance remains a crucial issue in cancer treatment. For refractory patients, the use of MET receptor tyrosine kinase inhibitors seems to be hopeful. Indeed, important mechanisms underlying drug resistance argue for association of MET inhibitors with targeted therapies, both on first-line to prevent a primary resistance and on the second line to overcoming acquired resistance. Indeed, met gene amplification is the second most common alteration involved in acquired resistance to anti-epidermal growth factor receptor (EGFR) therapies in non-small cells lung cancer (NSCLC). Hypoxia, for its part, can activate MET transcription and amplifies HGF signaling resulting in MET activation, which could be involved in vascular endothelial growth factor (VEGF) inhibitors escape. In HER2 positive breast cancers, MET amplification may also induce tumor cells a hatch escape, resulting in secondary resistance. Finally, some patients with BRAF mutated melanoma exhibit primary resistance to BRAF inhibition by stromal HGF (ligand of MET) secretion resulting in MET receptor activation. Experimental data highlight the role of MET in primary and secondary resistance and encourage combined treatments including MET inhibitors. In this context, several promising clinical trials are in progress in numerous cancers (NSCLC, melanoma, breast cancer, glioblastoma...) using combination of antiMET and other specific therapies targeting EGFR, BRAF, VEGF or HER2. This review summarizes the potential benefits that MET inhibition should provide to patients with cancer refractory to targeted therapies.