AIMS: To examine the relationship between cytochrome P450 2C19 (CYP2C19) genotype and expressed metabolic activity in 16 patients with advanced metastatic cancer. METHODS: Individual CYP2C19 genotypes were determined by PCR-based amplification, followed by restriction fragment length analysis, and compared with observed CYP2C19 metabolic activity, as determined using the log hydroxylation index of omeprazole. RESULTS: All 16 patients had an extensive metabolizer genotype. However, based on the antimode in a distribution of log omeprazole hydroxylation indices from healthy volunteers, four of the patients had a poor metabolizer phenotype and there was a general shift of the remaining 12 patients towards a slower metabolic phenotype. This suggests a reduction in metabolic activity for all patients relative to healthy volunteers. A careful analysis of patient medical records failed to reveal any drug interactions or other source for the observed discordance between genotype and phenotype. CONCLUSIONS: There are no previous reports of a 'discordance' between genotype and expressed enzyme activity in cancer patients. Such a decrease in enzyme activity could have an impact on the efficacy and toxicity of chemotherapeutic agents and other drugs, used in standard oncology practice.
AIMS: To examine the relationship between cytochrome P450 2C19 (CYP2C19) genotype and expressed metabolic activity in 16 patients with advanced metastatic cancer. METHODS: Individual CYP2C19 genotypes were determined by PCR-based amplification, followed by restriction fragment length analysis, and compared with observed CYP2C19 metabolic activity, as determined using the log hydroxylation index of omeprazole. RESULTS: All 16 patients had an extensive metabolizer genotype. However, based on the antimode in a distribution of log omeprazole hydroxylation indices from healthy volunteers, four of the patients had a poor metabolizer phenotype and there was a general shift of the remaining 12 patients towards a slower metabolic phenotype. This suggests a reduction in metabolic activity for all patients relative to healthy volunteers. A careful analysis of patient medical records failed to reveal any drug interactions or other source for the observed discordance between genotype and phenotype. CONCLUSIONS: There are no previous reports of a 'discordance' between genotype and expressed enzyme activity in cancerpatients. Such a decrease in enzyme activity could have an impact on the efficacy and toxicity of chemotherapeutic agents and other drugs, used in standard oncology practice.
Authors: J D Balian; N Sukhova; J W Harris; J Hewett; L Pickle; J A Goldstein; R L Woosley; D A Flockhart Journal: Clin Pharmacol Ther Date: 1995-06 Impact factor: 6.875