Sequence variations of mitochondrial DNA and individual sensitivity to the ototoxic effect of cisplatin

Background: Since mutations in the mitochondrial genome are associated with hearing loss, we analyzed whether sequence variations of mtDNA are associated with individual sensitivity, to cisplatin-induced ototoxicity. Materials and Methods: The mtDNA of 20 patients with and 19 patients without hearing impairment under therapeutic doses of cisplatin was sequenced for mutations and characterized for haplotype by restriction analysis. Results: Neither the A7445G mutation, nor the 7472insC insertion or the A1555G mutation were identified in any of the patients. Nucleotide variations in the variable D-loop region did not correlate with cisplatin-induced hearing loss. However, these patients clustered more frequently (5 out of 20) in the rare European haplogroup J, than those with normal hearing after therapy (I out of 19). Conclusion: The linkage of cisplatin-induced hearing impairment to the mitochondrial haplogroup J, which is also associated with the mitochondrially-mediated Lebers Hereditary Optic Neuropathy, might act as a predisponsing genetic background for biochemical differences in mitochondria.