Refractoriness to the pharmacological treatment of cancer is dependent on the expression levels of genes
involved in mechanisms of chemoresistance and on the existence of genetic variants that may affect their function. Thus,
changes in genes encoding solute carriers may account for considerable inter-individual variability in drug uptake and the
lack of sensitivity to the substrates of these transporters. Moreover, changes in proteins involved in drug export can affect
their subcellular localization and transport ability and hence may also modify the bioavailability of antitumor agents.
Regarding pro-drug activation or drug inactivation, genetic variants are responsible for changes in the activity of drugmetabolizing
enzymes, which affect drug clearance and may determine the lack of response to anticancer chemotherapy.
The presence of genetic variants may also decrease the sensitivity to pharmacological agents acting through molecular
targets or signaling pathways. Recent investigations suggest that changes in genes involved in DNA repair may affect the
response to platinum-based drugs. Since most anticancer agents activate cell death pathways, the evasion of apoptosis
plays an important role in chemoresistance. Several genetic variants affecting death-receptor pathways, the mitochondrial
pathway, downstream caspases and their natural modulators, and the p53 pathway, whose elements are mutated in more
than half of tumors, and survival pathways, have been reported. The present review summarizes the available data
regarding the role of genetic variants in the different mechanisms of chemoresistance and discusses their potential impact
in clinical practice and in the development of tools to predict and overcome chemoresistance.
Keywords: Apoptosis, cancer, drug, metabolism, mutation, pharmacology, refractoriness, transport
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