Re: Polymorphisms of death pathway genes FAS and FASL in esophageal squamous-cell carcinoma.

We have read with great interest the recent work by Sun et al. (1) about the role of functional FAS and FASL gene polymorphisms and esophageal squamouscell carcinoma risk. In addition to the report of Sun et al., polymorphisms of the FAS/FASL system have also been shown to be associated with acute myeloid leukemia(2), cervical cancer(3), and lung cancer (4). To analyze the role of FAS/FASL polymorphisms for breast cancer, we performed a case–control study that included 500 female breast cancer patients and 500 healthy sexand age-matched control subjects. The study was approved by the Ethical Committee of the Medical University Graz. Written informed consent was obtained from all participating subjects. All subjects were Caucasian. FAS –1377G A, FAS –670A G, and FASL –844C T genotypes were determined by a 5 -nuclease assay (TaqMan; Applera Austria Handels, Vienna, Austria). Primer and probe sets were designed and manufactured by the Applied Biosystems Assay-by-Design custom service (Applera Austria Handels). The following sequences of primers and probes were used to detect FAS and FASL polymorphisms: for FAS –1377G A, forward primer (5 -GCT CAGAGTGTGTGCACAAG-3 ), reverse primer (5 -ACTGTTAGTGCCATGAG GAAGAC-3 ), G-probe (5 -VIC-CTG GCACGCCCAGG-NFQ-3 , where VIC is the fluorescent dye, NFQ is the nonfluorescent quencher, and the underlined base indicates the polymorphic site), and A-probe (5 FAM-CTGGCACAC CCAGG-NFQ-3 , where FAM is the fluorescent dye); for FAS –670A G, forward primer (5 -CTATGGCGCAA CATCTGTACTTTT-3 ), reverse primer (5 -TCCATCTTGTGGCTGCAACAT3 ), G-probe (5 -VICCATTCCAG GAACGTC-NFQ-3 ), and A-probe (5 FAM-CATTCCAGAAACGTC-NFQ3 ); and for FASL 844C T, forward primer (5 -CCTGGGTGACAGAGT GAGACT-3 ), reverse primer (5 AGGCTGCAAACCAGTGGAA-3 ), Cprobe (5 -VIC-TTTGTATTTCGCAAT GTT-NFQ-3 ), and T-probe (5 -FAM CTTTGTATTTCACAATGTT-NFQ-3 ). As a quality control, 95 samples were reanalyzed; results were identical for all samples. Characteristics of the study population have been described previously (5,6). At the time of breast cancer diagnoses, case patients were between 28 and 84 years of age, with a mean ( standard deviation) age of 57 ( 11) years. Control subjects were agematched to the case patients ( 1 year), and their mean age was 57 ( 11) years with a range of 28–84 years. Genotype distribution did not deviate from the Hardy–Weinberg equilibrium in case patients or control subjects. Genotype frequencies are summarized in Table 1. The FAS –1377A allele was associated with a higher breast cancer risk, whereas genotype and allele frequencies of FAS –670A G and FASL –844C T were not statistically significantly different between case patients and control subjects. In a co-dominant model (genotype codes: GG 0, GA 1, AA 2), the odds ratio of the FAS –1377A variant for breast cancer was 1.42 (95% confidence interval 1.08 to 1.88; P .013). Although both FAS polymorphisms were in tight linkage disequilibrium (P .001), the FAS –670G A polymorphism appeared to have no statistically significant influence on breast cancer risk. The FAS –1377A/–670G haplotype was associated with breast cancer (odds ratio 1.39, 95% confidence interval 1.02 to 1.90;P .038), but this association was less pronounced than that of the –1377G A polymorphism alone. In summary, our data suggest that the FAS –1377G A polymorphism is associated with breast cancer, similar to its association with esophageal squamouscell carcinoma(1). Interestingly, two other functional polymorphisms of the FAS/FASL system, FAS –670A G and FASL –844C T, were not related to breast cancer risk in our study. This finding could be the result of the different ethnicities of study populations and/or different molecular mechanisms of breast and esophageal tumorigenesis, respectively. Consequently, we urge that the association between polymorphisms of the FAS/FASL system and cancer be investigated in additional studies.