Heat shock proteins as targets in oncology

Heat shock proteins are ubiquitous molecular chaperones involved in posttranslational folding, stability, activation and maturation of many proteins that are essential mediators of signal transduction and cell cycle progression. Hsp90 proteins are the best studied proteins of this family. A growing number of Hsp90 client proteins have been shown to be important for the development, proliferation and survival of several types of cancer. Inhibition of Hsp90 leads to the degradation of known oncogene products, such as Her2, BRAF and others, leading to the simultaneous blockade of multiple oncogenic transduction pathways. Hsp90 inhibitors, derived from the natural compound geldanamycin, are attractive targets for anticancer drug development. We will review the clinical data on Hsp90 inhibitors in different malignancies. The best known of them, 17-AAG, has shown significant antitumour activity against a broad variety of cancers in preclinical studies, including breast, myeloma, melanoma, prostate and lung cancers. Hsp90 inhibitors can be used as single agents or in combination with other targeted treatments or chemotherapy and radiotherapy. The results of clinical phase II and III trials evaluating the effi cacy of these drugs in different types of tumours are awaited.