Cancer-associated fibroblasts confer ALK inhibitor resistance in EML4-ALK-driven lung cancer by concurrent integrin and MET signaling.

Cancer-associated fibroblasts (CAFs) are associated with tumor progression and drug resistance. Here, we investigated the mechanisms underlying the cross-talk between CAFs and tumor cells in non-small cell lung cancer (NSCLC). In NSCLC cell lines with EML4-ALK fusions, we observed substantial CAF-mediated drug resistance to clinically used inhibitors of the tyrosine kinase ALK. Array-based cytokine profiling of CAF-derived conditioned medium indicated that a major contributor to the phenomenon was the secreted growth factor HGF, and blocking its receptor MET overcame paracrine resistance to ALK inhibition. However, cell-selective labeling of the proteome in cocultures also revealed an equally important contribution by the fibronectin-integrin pathway, specifically integrin β1, which was confirmed through pharmacological inhibition and cell-specific silencing or knockout. Concurrent targeting of MET and integrin signaling effectively abrogated ALK inhibitor resistance in EML4-ALK+ NSCLC cells cocultured with CAFs. Moreover, the combination of the ALK inhibitor alectinib with the MET inhibitor capmatinib and/or the integrin inhibitor cilengitide was more effective than single-agent treatment in suppressing tumor growth in allografted mice. The findings illustrate a previously unappreciated complex nature of concurrent paracrine and juxtacrine mechanisms of CAF-driven resistance that may inform the development of more effective therapeutic approaches.