A polymorphism in NAD(P)H:quinone oxidoreductase (NQO1): relationship of a homozygous mutation at position 609 of the NQO1 cDNA to NQO1 activity

Abstract

A polymorphism in NAD(P)H:quinone oxidoreductase (NQO1): relationship of a homozygous mutation at position 609 of the NQO1 cDNA to NQO1 activity Sir -NQO1 has attracted considerable attention owing to its ability to deactivate a broad range of xenobiotics while activating certain anti-tumour quinones (Ross et al., 1994). A number of recent reports have highlighted the occurrence and potential significance of a point mutation in the NQO1 gene which is associated with a loss of NQO1 activity in both normal and tumour tissue (Traver et al., 1992; Eickelmann et al., 1994a,b;Rosvold et al., 1995;Kolesar et al., 1995). The mutation is a C to T point mutation at position 609 of the NQO1 cDNA which codes for a proline to serine substitution in the amino acid sequence of the protein (Traver et al., 1992). The mutation was originally characterised in the BE human colon adenocarcinoma cell line by SSCP analysis and sequencing (Traver et al., 1992) and subsequently in the H596 human non-small-cell lung cancer cell line by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique (1995) have recently examined the relationship between the heterozygous mutation at position 609 and NQO1 activity. These data demonstrate a wide range of NQO1 activity in IC to T heterozygotes and suggests a significant role for post-transcriptional modification in determination of NQO1 activity.In the paper by Kuehl et al. (1995), the BE cell line is described as heterozygous for the 9C-T point mutation with very low NQO1 activity. An additional fibroblastoid cell line, the 3701T line, was reported as homozygous for the mutation with very low NQO1 activity. Since these results differed, with respect to the BE cell line, from the original report of Traver et al. (1992) al., 1995). Because of the somewhat nonspecific nature of both DCPIP as a substrate and dicoumarol as an inhibitor (Ross et al., 1993), it is possible that the extremely low rates of dicoumarol-inhibitable DCPIP reduction obtained in BE, H596 or 3701T cells may reflect the presence of reductases other than NQO1. Our joint findings confirm previous results that the BE cells are homozygous for the 609C-T mutation and that the presence of the homozygous mutation is associated with a loss of NQO1 protein activity (Traver et al., 1992. The same conclusion was reached by Eickelmann et al. (1994) who reported that a cell line and three human kidney carcinoma samples without detectable NQO1 activity were all homozygous for the IC to T mutation.An alternatively spliced form of NQO1 lacking exon 4 and the quinone binding site has recently been reported (Gasdaska et al., 1995). This form of NQO1 has minimal enzyme activity with traditional model substrates for NQO1 but retains immunoreactivity and can be detected using a polyclonal antibody to NQO1 (Gasdaska et al., 1995). We have also examined BE and H596 cells for NQO1 protein using the same polyclonal antibody used by Gasdaska and colleagues and were unable to detect NQO1 protein. We have recently sugg...

Genetic susceptibility to tobacco-related cancer

“…Recently, a polymorphism of the gene encoding NQO1 has been described. The polymorphic variant of the gene (a C to T transition at base pair 609, codon 187) is associated with reduced NQO1 activity (Ross et al, 1996;Siegel et al, 1999). The three genotypes of this gene are the homozygous wild-type C/ C (normal activity), the heterozygous C/T genotype (mild activity), and the homozygous rare allele T/T genotype (2-4% of normal activity).…”

NQO1, MPO, and the risk of lung cancer: A HuGE review

“…As a clear gene-dose effect was suggested by the genotype-phenotype association studies, [21][22][23][24][25] a genetic model (codominant or decreasing model), in which lung cancer risks of the genotypes Pro/Pro, Pro/Ser, and Ser/Ser decrease in that order, was applied. As the Ser/Ser genotype has not been separated due to a low prevalence of the rare Ser allele in several studies, we combined the Pro/Ser genotype with Ser/Ser genotype.…”

“…The three genotypes of this gene are the Pro/Pro (normal activity), the Pro/Ser (mild activity), and the Ser/Ser (2-4% of normal activity). [21][22][23][24][25] The genotype frequencies in different populations are shown in Table 1. 26 -65 The summary frequency of the Ser allele among Caucasians was 18.9% (95% CI ϭ 15.6 -22.1%), and the summary frequency of the Ser/Ser and Pro/Ser genotypes combined was 31.8% (95% CI ϭ 30.0 -33.7%).…”

Genetic polymorphisms in glutathione S-transferase T1 affect the surgical outcome of varicocelectomies in infertile patients

“…Phase II enzymes catalyse the conversion of quinones to hydroquinones, which are readily excreted by the body. However, the Pro-toSer substitution in NQO1 is associated with a loss of enzyme function because of protein instability [16,17]. In our study, patients with an NQO1-Ser/Ser genotype showed a better response to surgical repair.…”

“…NAD(P)H:quinone oxidoreductase 1 (NQO1) is a cytosolic enzyme that induces two-electron reduction of quinoid compounds to hydroquinones, a less toxic form, thus avoiding free radical formation. A sequence variant at position 609 (C-to-T, proline [Pro]-to serine [Ser], rs1800566 at dbSNP) in the NQO1 gene encodes for an enzyme with reduced quinone reductase activity, which has been hypothesized to affect cancer susceptibility [16,17].…”