Resistance to cytotoxic agents.

Conflicting results have been published concerning the role of apoptosis impairment in cytotoxic drug resistance. This has shed important doubts on the currently accepted dogma, which presents apoptosis as a universal determinant of drug activity. These differing results are likely to be related to the cell-type specificity of apoptotic pathways. New genetic tools have recently been made available for the study of anticancer drug resistance. Differential or subtractive analyses of gene expression, especially using cDNA microarrays, allow the identification of multiple genes and complex pathways involved in drug activity, and the use of genetic suppressor elements represents a functional approach for the identification of resistance genes.