Extracellular vesicles induce aggressive lung cancervia non-canonical integrin-EGFR-KRAS signaling
Small cell lung cancer (SCLC) is an extremely aggressive lung cancer type with a patient median survival of 6-12 months. Epidermal growth factor (EGF) signaling plays an important role in triggering SCLC. In addition, growth factor-dependent signals and alpha-, beta-integrin (ITGA, ITGB) heterodimer receptors functionally cooperate and integrate their signaling pathways. However, the precise role of integrins in EGF receptor (EGFR) activation in SCLC has remained elusive. We analyzed RNA-sequencing data, human precision-cut lung slices (hPCLS), retrospectively collected human lung tissue samples and cell lines to demonstrate that non-canonical ITGB2 signaling activates EGFR and RAS/MAPK/ERK signaling in SCLC. Further, we identified a novel SCLC gene expression signature consisting of 93 transcripts that were induced by ITGB2, which might be used for stratification of SCLC patients, prognosis prediction of LC patients and development of patient-tailored therapies. We also found by proteomic analysis a cell-cell communication mechanism based on extracellular vesicles (EVs) containing ITGB2, which were secreted by SCLC cells and induced in control human lung tissue RAS/MAPK/ERK signaling and SCLC markers. We uncovered a mechanism of ITGB2-mediated EGFR activation in SCLC that explains EGFR-inhibitor resistance independently of EGFR mutations, suggesting the development of therapies targeting ITGB2 for patients with this extremely aggressive lung cancer type.