New pharmacological strategies against metastatic spread

Although metastatic spread is the most frequent cause of death in cancer patients, there are very few drugs specifically targeting this process. Bases for a new antimetastatic drug discovery strategy are weak because a great number of unknowns characterize the complete understanding of the metastatic cascade mechanisms. Moreover, the current experimental models are too simplistic and do not account for the complexity of the phenomenon. Some targets have been identified but too few are validated. Among them, the metastasis suppressor genes seem to be the most promising. In spite of this, during recent years, a dozen of molecules, which fulfil the definition of a specific metastatic drug that inhibits the metastases without altering the growth of the primary tumour (which can be eradicated by surgery), have been identified and assessed for the proof of the concept. The continuation of this effort would benefit in terms of efficiency, if the objectives were defined more precisely. It is particularly important to distinguish molecules that prevent spread of the metastatic cells of the early-stage primary tumour from the ones which induce a regression of the established metastases or to inhibit the transition from disseminated occult tumour cells to dormant micrometastasis. This second goal is a priori more relevant in the current clinical setting where the detection of early metastatic spread is very difficult, and therefore would call for greater effort on the part of the scientific community.