Integrins are transmembrane receptors that are the bridges for cell-cell and cell-extracellular matrix (ECM) interactions. When triggered, integrins trigger chemical pathways to the interior (signal transduction), such as the chemical composition and mechanical status of the ECM. This results in a response (activation of transcription) like the regulation of the cell cycle, cell shape, and/or motility; or adding new receptors to the cell membrane. This allows rapid and flexible responses to events at the cell surface, for example to signal platelets to initiate an interaction with coagulation factors.
Integrins come in several types. One cell may have several types on its surface. Integrins are found in all animals.
Integrins work alongside other receptors such as cadherins, the immunoglobulin superfamily cell adhesion molecules, selectins and syndecans to mediate cell–cell and cell–matrix interaction. Ligands for integrins include fibronectin, vitronectin, collagen and laminin.
Combined inhibition of the adhesion receptor β1 integrin and the stress-mediator c-Jun N-terminal kinase (JNK) induces radiosensitization and blocks invasion in stem-like and patient-derived GBM cultures as well as in GBM cell lines. In vivo, this treatment approach not only significantly delays tumor growth but also increases median survival of orthotopic, radiochemotherapy-treated GBM mice. Both, in vitro and in vivo, effects seen with β1 integrin/JNK co-inhibition are superior to the monotherapy. Mechanistically, the in vitro radiosensitization provoked by β1 integrin/JNK targeting is caused by defective DNA repair associated with chromatin changes, enhanced ATM phosphorylation and prolonged G2/M cell cycle arrest. Our findings identify a β1 integrin/JNK co-dependent bypass signaling for GBM therapy resistance, which might be therapeutically exploitable 2).