Metal complexes targeting the Translocator Protein 18 kDa (TSPO)

Since the discovery of antitumor activity of cisplatin in the late 60's, the development of metal-based drugs has had an enormous burst with the aim of to increase the anti-cancer activity, lower side effects and promote specific accumulation to the target cells or organs. Indeed, a new discipline, called medicinal inorganic chemistry, has born where metal ions play a fundamental role. This review provides a comprehensive overview of various metal complexes targeting the Translocator Protein (TSPO), an 18 kDa high affinity cholesterol- and drug-binding protein found mostly in the outer mitochondrial membrane and formerly known as peripheral-type benzodiazepine receptor. TSPO distribution in healthy tissues varies considerably; in contrast, aberrant expression of TSPO has been noted in several pathological specimens including neurodegenerative diseases and cancers. These findings suggest that TSPO-targeted therapy and imaging may have utility in the treatment and visualization of diseases expressing high density of TSPO. In this review, potential applications in cancer diagnosis and therapy will be discussed.