RATIONALE: Among the first line antituberculosis (anti-TB) drugs, the major drug incriminated in the development of hepatotoxicity is isoniazid (INH). The human N-acetyl transferase2 (NAT2) gene is mainly responsible for INH metabolism. This gene exhibits a hereditarily determined polymorphism. There is presently no study on the predominant NAT2 genotype among Filipinos. There are also no Filipino studies on the incidence of hepatitis and other adverse effects of first line anti-TB drugs.

OBJECTIVES: To determine the predominant NAT2 genotype and its association with the development of hepatitis among Filipino children given first line anti-TB drugs (INH, rifampicin and pyrazinamide) and to determine the incidence of hepatitis and other serious adverse reactions to these drugs.

STUDY DESIGN: Prospective cohort study

SETTING: Tertiary government hospital in Metro Manila

STUDY POPULATION: Children on to 18 years old with pulmonary tuberculosis and normal liver function test at baseline.

METHODS: Total bilirubin (TB), direct bilirubin (DB) and liver transaminases (AST and ALT) were checked routinely at baseline and at thow, four, eight and 12 weeks after starting treatment. Within the first month of treatment, blood was also taken for NAT2 genotyping. The identification of the three NAT2 polymorphisms that are associated with a slow acetylator status - 481C to T (NAT2*5), 950G to A (NAT2*6) and 857G to A (NAT2*7) was carried out by polymerase chain reaction-restriction fragment length polymorphism. All patients were followed up for a total of six months. The presense of any adverse effects like gastroinstestinal symptoms, rash, hepatitis or drug fever was also monitored.

RESULTS: A total of 24 children [mean age: 5 years; 11 males] were included. Majority (96%) were diagnosed by passive detection and mean Z score was - 1.38 (1 to -3). No patient developed hepatotoxicity or any side effects to anti-TB drugs. In 23 patients who had NAT2 genotyping, 39% and 22% were alleles homozygous for the NAT2*6 and NAT2*7, respectively. There was a combination of alleles in only three (13%) subjects.

CONCLUSION: NAT2*6 and NAT2*7 alleles associated with a slow acetylator status were detected among our patients although the presence of these variants did not lead to any hepatotoxicity nor any treatment-related side effects. A larger study with broader genotype analysis is needed to confirm the present findings.

Human ; Male ; Female ; Adolescent ; Child ; Child Preschool ; Infant ; Isoniazid ; Pyrazinamide ; Rifampin ; Alleles ; Bilirubin ; Liver Function Tests ; Transaminases ; Antitubercular Agents ; Tuberculosis, Pulmonary ; Hepatitis ; Polymorphism, Genetic

Objectives: The highly polymorphic nature of the CYP2D6 gene and its central role in the metabolism of commonly used drugs make it an ideal candidate for pharmacogenetic screening. This study aims to determine the prevalence of CYP2D6 polymorphisms among Filipinos and their association to lung cancer. Method: Forty seven single nucleotide polymorphisms (SNPs) of the CYP2D6 gene were genotyped from DNA samples of 115 cases with lung cancer and age- and sex-matched 115 controls. Results: Results show that 18 out of 47 polymorphisms have significant genotypic variability (>1% for at least 2 genotypes). No variant is associated with lung cancer. However, rs1135840, rs16947 and rs28360521, were found to be highly variable among Filipinos. Conclusion This study demonstrated that CYP2D6 polymorphisms are present among Filipinos, which, although not found to be associated with lung cancer, can be useful biomarkers for future pharmacogenetic studies. The SNP rs16947 is found to be associated with cancer and timolol-induced bradycardia; the SNP rs1135840, on the other hand, is only shown to be linked with cancer. The genetic variant rs28360521 is known to be associated with low-dose aspirin-induced lower gastrointestinal bleeding.
Pharmacogenetics ; Cytochrome P-450 CYP2D6 ; Lung Neoplasms ; Biomarkers

Objectives. Polymorphisms in metabolic genes which alter rates of bioactivation and detoxification have been shown to modulate susceptibility to colorectal cancer. This study sought to evaluate the colorectal cancer risk from environmental factors and to do polymorphism studies on genes that code for Phase I and II xenobiotic metabolic enzymes among Filipino colorectal cancer patients and matched controls. Methods. A total of 224 colorectal cancer cases and 276 controls from the Filipino population were genotyped for selected polymorphisms in GSTM1, GSTP1, GSTT1, NAT1 and NAT2. Medical and diet histories, occupational exposure and demographic data were also collected for all subject participants.Results. Univariate logistic regression of non-genetic factors identified exposure to UV (sunlight) (OR 1.99, 95% CI: 1.16-3.39) and wood dust (OR 2.66, 95% CI: 1.21-5.83) and moldy food exposure (OR 1.61, 95% CI:1.11-2.35) as risk factors; while the NAT2*6B allele (recessive model OR 1.51, 95% CI :1.06-2.16; dominant model OR 1.87, 95% CI: 1.05-3.33) and homozygous genotype (OR 2.19, 95% CI: 1.19-4.03) were found to be significant among the genetic factors. After multivariate logistic regression of both environmental and genetic factors, only UV radiation exposure (OR 2.08, 95% CI: 1.21-3.58) and wood dust exposure (OR 2.08, 95% CI: 0.95-5.30) remained to be significantly associated with increasing colorectal cancer risk in the study population.Conclusion. This study demonstrated that UV sunlight and wood dust exposure play a greater role in influencing colorectal cancer susceptibility than genotype status from genetic polymorphisms of the GST and the NAT` genes.
Colorectal Neoplasms ; Polymorphism, Genetic