Quantitation of ligand is critical for ligand-dependent MET signalling activation and determines MET-targeted therapeutic response in gastric cancer.

Background: Despite the promising preclinical antitumor activity of MET-targeting therapies, most clinical trials have failed. We introduced a new concept of quantitation of stroma-induced hepatocyte growth factor (HGF) to assess the actual MET signalling activity in gastric cancer (GC).
Methods: We treated serially diluted HGF and conditioned media (CM) from cancer-associated fibroblasts (CAFs) on low MET-expressing cancer cells and investigated the phenotypical and signalling changes. Stromal proportion and MET expression in GC samples were assessed, and gene set enrichment analysis (GSEA) from the public database was performed. The antitumor effect of anti-MET treatment was examined, especially when cancer cells were activated in a ligand-dependent manner.
Results: Relatively high doses of HGF or high-concentrated CM fully activated MET signalling cascades and promoted cell proliferation/invasion. High stromal proportion denoted worse patient survival in MET-positive GCs than in MET-negative ones. GSEA showed that the gene sets regarding proliferation, migration, and CAF as well as MET pathway signature were enriched in simultaneously MET- and HGF-positive samples. Sufficient ligand-dependent MET signalling activation increased the sensitivity to crizotinib.
Conclusions: We conclude that patients whose tumours have a high stromal proportion and at least low MET expression may benefit more from MET-targeted therapies.