Drug resistance in oncology: from concepts to applications.

The complex problem of drug resistance is discussed with respect to host toxicity, to tumor characteristics (kinetic resistance, heterogeneity of cell subpopulations, hypoxia, mutation and gene amplification), and to the medication itself (pharmacokinetic and pharmacodynamic resistance: cell membrane, intracellular metabolism, intracellular target). After detailing each type of resistance, the possibilities of fighting against drug resistance are explored (dealing with host toxicity, tumor characteristics and drugs--intensifying therapy, multiple drug therapy, biochemical modulation, particular modalities of drug administration). Finally, perspectives of research and development of new drugs are summarized.