Tumor cells, with stem-like properties, are highly aggressive and often display drug resistance. Here, we reveal that integrin αvβ3 serves as a marker of breast, lung, and pancreatic carcinomas with stem-like properties that are highly resistant to receptor tyrosine kinase inhibitors such as erlotinib. This was observed in vitro and in mice bearing patient-derived tumor xenografts or in clinical specimens from lung cancer patients that had progressed on erlotinib. Mechanistically, αvβ3, in the unligated state, recruits KRAS and RalB to the tumor cell plasma membrane, leading to the activation of TBK-1/NFκB. In fact, αvβ3 expression and the resulting KRAS/RalB/NFκB pathway were both necessary and sufficient for tumor initiation, anchorage-independence, self-renewal, and erlotinib resistance. Pharmacological targeting of this pathway with Bortezomib reversed both tumor stemness and erlotinib resistance. These findings not only identify αvβ3 as a marker/driver of carcinoma stemness but they reveal a therapeutic strategy to sensitize such tumors to RTK inhibition.

SUMMARY While molecular subtypes of glioblastoma (GBM) are defined using gene expression and mutation profiles, we identify a unique subpopulation based on addiction to the high affinity glucose transporter, Glut3. Although Glut3 is a known driver of a cancer stem cell phenotype, direct targeting is complicated by its expression in neurons. Using established GBM lines and patient-derived stem cells, we identify a subset of tumors within the “Proneural” and “Classical” subtypes that are addicted to aberrant signaling from integrin αvβ3 that activates a PAK4-YAP/TAZ signaling axis to enhance Glut3 expression. This defined subpopulation of GBM is highly sensitive to agents that disrupt this pathway, including the integrin antagonist cilengitide, providing a targeted therapeutic strategy for this unique subset of GBM tumors.

Identifying the molecular basis for cancer cell dependence on oncogenes such as KRAS can provide new opportunities to target these addictions. Here, we identify a novel role for the carbohydrate-binding protein Galectin-3 as a lynchpin for KRAS dependence. By directly binding to the cell surface receptor integrin αvβ3, Galectin-3 gives rise to KRAS addiction by enabling multiple functions of KRAS in anchorage-independent cells, including formation of macropinosomes that facilitate nutrient uptake and ability to maintain redox balance. Disrupting αvβ3/Galectin-3 binding with a clinically active drug prevents their association with mutant KRAS, thereby suppressing macropinocytosis while increasing reactive oxygen species to eradicate αvβ3-expressing KRAS mutant lung and pancreatic cancer patient-derived xenografts and spontaneous tumors in mice. Our work reveals Galectin-3 as a druggable target for KRAS-addicted lung and pancreas cancer, and indicates integrin αvβ3 as a biomarker to identify susceptible tumors.