AXL–SHC1 signaling axis mediates adaptive resistance to HER2-targeted tyrosine kinase inhibitors in HER2-aberrant lung and gastric cancers

Human epidermal growth factor receptor 2 (HER2)-tyrosine kinase inhibitors (TKIs) are being developed for the treatment of patients with HER2-aberrant lung and gastric cancers. However, achieving complete tumor remission remains challenging. Here, we investigated the molecular mechanisms underlying adaptive resistance to HER2-TKIs in HER2-aberrant tumor cells in order to devise strategies to prevent the emergence of drug-tolerant cells. Our findings showed that the AXL receptor was activated by HER2-TKIs and maintained cell survival by interacting with epidermal growth factor receptor, HER2, and HER3. This process, mediated by the SHC1BP–SHC1 axis, contributed to adaptive resistance to HER2-TKIs in a subset of HER2-aberrant lung and gastric cancers. AXL inhibition significantly delayed tumor regrowth of AXL-overexpressing cells by enhancing HER2-TKI-induced apoptosis in xenograft models. These results suggest that patients with HER2-aberrant lung and gastric cancers exhibiting high AXL expression may benefit from an initial combination therapy with an AXL inhibitor.