The Hsp90 molecular chaperone has emerged as one of the most exciting targets for cancer drug development. Hsp90 is overexpressed in many malignancies, very likely as a result of the stress that is induced both by the hostile cancer microenvironment and also by the mutation and abberant expression of oncoproteins. A particularly attractive feature of Hsp90 as a cancer drug target is that it is required for the conformational stability and function of a wide range of oncogenic ‘client’ proteins, including c-Raf-1, Cdk4, ErbB2, mutant p53, c-Met, Polo-1 and telomerase hTERT. Inhibition of Hsp90 should therefore block multiple mission critical oncogenic pathways in the cancer cell, leading to inhibition of all the hallmark traits of malignancy. This combinatorial blockade of oncogenic targets should give rise to board spectrum antitumour activity across multiple cancer types. The ‘druggability’ of Hsp90 was confirmed by the discovery that the natural products geldanamycin and radicicol, which have anticancer activity, exert their biological effects by inhibiting the essential ATPase activity associated with the N-terminal domain of the protein. The first-inclass Hsp90 inhibitor has entered clinical trial and provided proof of concept that Hsp90 can be inhibited and clinical benefit seen at non-toxic doses. Further development is underway and a related analogue 17DMAG also shows promise in preclinical models. In addition, novel Hsp90 inhibitors have been identified using methods such as high throughput screening and x-ray crystallography. The opportunities and challenges involved in translating the fast moving biology of Hsp90 into patient benefit is discussed.
Cancer Research UK Centre for Cancer Therapeutics, Institute of Cancer Research, Sutton, Surrey SM2 5NG UK.
Publication date: October 1, 2003
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Current Cancer Drug Targets aims to cover all the latest and outstanding developments on the medicinal chemistry, pharmacology, molecular biology, genomics and biochemistry of contemporary molecular drug targets involved in cancer, e.g. disease specific proteins, receptors, enzymes, genes. Each issue of the journal contains a series of timely in-depth reviews written by leaders in the field covering a range of current topics on drug targets involved in cancer. As the discovery, identification, characterization and validation of novel human drug targets for anti-cancer drug discovery continues to grow; this journal has become essential reading for all pharmaceutical scientists involved in drug discovery and development.