Molecular cancer therapy: can our expectation be met?

Altered regulation of tyrosine kinase receptors (RTKs) is frequent in solid tumors and it is often associated with the acquisition of an aggressive phenotype. Thus, therapies targeting these receptors have been proposed as molecular approaches to treat human cancers. The MET proto-oncogene, encoding the tyrosine kinase receptor for Hepatocyte Growth Factor (HGF), controls genetic programs leading to cell growth, invasion and protection from apoptosis. Germline mutations of MET in patients affected by Hereditary Papillary Renal Carcinomas (HPRC) have provided strong genetic evidences for its role in human malignancies; moreover constitutive activation of this receptor, as consequence of different mechanisms such as overexpression, autocrine stimulation or point mutations, is frequent in sporadic cancers. Several strategies to block the activation of MET are under development, such as the use of tyrosine kinase inhibitors or monoclonal antibodies and some of these compounds have already been used in clinical trials. In this review we will discuss the molecular mechanisms underlying MET involvement in tumorigenesis and present preclinical and clinical data obtained with compounds aimed at targeting MET in the frame of cancer therapy.