Integrin α6: a potential target for cancer molecular imaging and targeting therapy

As a major kind of cell surface adhesion molecules with signal transduction function, integrins play a major role in tumorigenesis and tumor progression. The role of integrins in tumor cells and the tumor microenvironment has been extensively revealed. Among the integrin family, integrin αvβ3 is the most studied integrin in the past 20 years. Plenty of preclinical and clinical studies have been conducted, which showed clinical benefits of targeting integrin αvβ3 in tumor imaging and treatment. Currently, the focus of interest is gradually shifting from integrin αvβ3 toward other integrin subtypes. Integrin α6 is expressed in many malignant tumors, such as colorectal cancer, head and neck squamous cell carcinoma, breast cancer, pancreatic cancer, and liver cancer, and its expression is correlated with poor survival of the patients. Recent studies have shown that tumor molecular imaging agents and therapeutic drugs targeting integrin α6 have excellent safety and efficacy in preclinical mouse models, encouraging clinical translation of this promising target. In this review, we briefly overview the physiological and pathological function of integrin α6 and highlight the recent advances in integrin α6-targeted imaging and therapeutics in tumors.