A trafficking regulatory subnetwork governs α _V β ₆ integrin-HER2 cross-talk to control breast cancer invasion and drug resistance

HER2 and α_Vβ₆ integrin are independent predictors of breast cancer survival and metastasis. We identify an α_Vβ₆/HER2 cross-talk mechanism driving invasion, which is dysregulated in drug-resistant HER2+ breast cancer cells. Proteomic analyses reveal ligand-bound α_Vβ₆ recruits HER2 and a trafficking subnetwork, comprising guanosine triphosphatases RAB5 and RAB7A and the Rab regulator guanine nucleotide dissociation inhibitor 2 (GDI2). The RAB5/RAB7A/GDI2 functional module mediates direct cross-talk between α_Vβ₆ and HER2, affecting receptor trafficking and signaling. Acute exposure to trastuzumab increases recruitment of the subnetwork to α_Vβ₆, but trastuzumab resistance decouples GDI2 recruitment. GDI2, RAB5, and RAB7A cooperate to regulate migration and transforming growth factor-β activation to promote invasion. However, these mechanisms are dysregulated in trastuzumab-resistant cells. In patients, <i>RAB5A</i>, <i>RAB7A</i>, and <i>GDI2</i> expression correlates with patient survival and α_Vβ₆ expression predicts relapse following trastuzumab treatment. Thus, the RAB5/RAB7A/GDI2 subnetwork regulates α_Vβ₆-HER2 cross-talk to drive breast cancer invasion but is subverted in trastuzumab-resistant cells to drive α_Vβ₆-independent and HER2-independent tumor progression.