No abstract

Previous mutational analysis for BRCA gene mutations in sporadic ovarian cancer occurring in Chinese patients in Hong Kong identified six germline BRCA1 mutations and one germline BRCA2 mutation, six of which were novel (Khoo et al., 2000). Knowledge of BRCA gene mutations in the Chinese population is relatively scant. In this study, we focussed on whether any of these mutations could be recurrent in our Chinese population, making use of archival paraffin embedded tissue. A consecutive series of 214 ovarian cancer cases, half of Southern Chinese origin from Hong Kong whilst the other half of Northern Chinese origin from Beijing were used for the study. We identified one further novel mutation, 1081delG, in BRCA1. This was found to occur in two unrelated individuals with shared haplotype as revealed by allelotype analysis, thus demonstrating founder effect. Two other recurrent mutations were also identified, the 2371-2372delTG mutation in BRCA1 and the 3337C>T mutation in BRCA2 recurring in two and three unrelated individuals respectively, giving an overall prevalence 4.7% of recurrent BRCA mutations in ovarian cancer in the Southern Chinese population. Most importantly, all our recurrent mutation carriers were identified from Southern Chinese patients from Hong Kong whilst such mutations were absent in samples from the Northern Chinese. Our findings indicate possible heterogeneity in the BRCA genotype between Northern and Southern Chinese. The identification of a founder mutation and two recurrent mutations moreover, has important implications towards screening strategies for breast and ovarian cancer among Chinese of southern ancestral origin who are now dispersed throughout the world.

Because of difficulty in measuring each antioxidant component separately and interactions among antioxidants, methods have been developed to assess the total antioxidant capacity of serum or plasma. The 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox)-equivalent antioxidant capacity (TEAC) assay (1 ), the oxygen radical absorbance capacity (ORAC) assay (2 ), and the ferric reducing ability of plasma (FRAP) assay (3 ) are commonly used and have been extensively evaluated. Although comparable mean results have been obtained with the TEAC and ORAC assays (4,5 ), no correlation has been found between ORAC and TEAC values or between FRAP and TEAC values (6 ). This lack of correlation between TEAC and other assays is likely attributable to underestimation of overall antioxidant capacity. Underestimation may be related to the effects of dilution (7 ) and to premature measurement of inhibition percentage at a fixed time of 3 min (6 ). In fact, both the ORAC and TEAC assays are inhibition methods: a sample is added to a freeradical-generating system, and the inhibition of the free radical action is measured. This inhibition is related to the antioxidant capacity of the sample. In addition, both assay methods measure antioxidants in serum or plasma proteins, including albumin (6 ). In this study we investigated the performance of the TEAC assay, modified the procedure, and then reevaluated the TEAC for comparison with the ORAC assay.The TEAC assay, commercialized by Randox Laboratories Ltd., is based on the suppression of the absorbance of radical cations of 2,2Ј-azinobis(3-ethylbenzothiazoline 6-sulfonate) (ABTS) by antioxidants in the test sample when ABTS incubates with a peroxidase (metmyoglobin) and H 2 O 2 (1 ). If the inhibition time is fixed at 3 min, as stated in the manufacturer's instructions, the added antioxidants quench ABTS radicals in a nonlinear doseresponse fashion (6 ). To optimize the incubation period for the complete inhibition of ABTS radical formation in the system, we extended the reaction up to 40 min and monitored the absorbance changes at 3-min intervals at 600 nm (Fig. 1A). A reaction mixture containing 20 L of H 2 O 2 (100 mol/L), 100 L of metmyoglobin (6.1 mol/ L), ABTS (610 mol/L), and 4 L of Trolox (concentration range, 0 -1.65 mol/L) was incubated and subjected to spectrophotometry (Quant; Bio-Tek Instruments) at 37°C. We found that the formation of ABTS radicals increased in proportion to the incubation period until a plateau was achieved after 30 min. The higher the concentration of Trolox used in the reaction mixture, the