Norman Moullan

A TP53 polymorphism is associated with increased risk of colorectal cancer and with reduced levels of TP53 mRNA

We undertook a case–control study to examine the possible associations of the TP53 variants Arg>Pro at codon 72 and p53PIN3, a 16 bp insertion/duplication in intron 3, with the risk of colorectal cancer (CRC). The p53PIN3 A2 allele (16 bp duplication) was associated with an increased risk (OR 1.55, 95% CI 1.10−2.18, P=0.012), of the same order of magnitude as that observed in previous studies for other types of cancer. The Pro72 allele was weakly associated with CRC (OR=1.34, 95% CI 0.98−1.84, P=0.066). The possible functional role of p53PIN3 was investigated by examining the TP53 mRNA transcripts in 15 lymphoblastoid cell lines with different genotypes. The possibility that the insertion/deletion could lead to alternatively spliced mRNAs was excluded. However, we found reduced levels of TP53 mRNA associated with the A2 allele. In conclusion, the epidemiological study suggests a role for p53PIN3 in tumorigenesis, supported by the in vitro characterization of this variant.

Evidence for an important role of alcohol- and aldehyde-metabolizing genes in cancers of the upper aerodigestive tract.

Background: Incidence and mortality rates of upper aerodigestive tract cancers in Central Europe are among the highest in the world and have increased substantially in recent years. This increase is likely to be due to patterns of alcohol and tobacco consumption. Genetic susceptibility to upper aerodigestive tract cancer in relation to such exposures is an important aspect that should be investigated among populations in this region. Methods: A multicenter case-control study comprising 811 upper aerodigestive tract cancer cases and 1,083 controls was conducted in: Bucharest (Romania), Lodz (Poland), Moscow (Russia), Banska Bystrika (Slovakia), and Olomouc and Prague (Czech Republic). We analyzed six SNPs in three genes related to ethanol metabolism: alcohol dehydrogenase 1B and 1C (ADH1B, ADH1C) and aldehyde dehydrogenase 2 (ALDH2). Results: The ADH1B histidine allele at codon 48 was associated with a decreased risk of upper aerodigestive tract cancer; odds ratios (OR) were 0.36 [95% confidence interval (95% CI), 0.17-0.77] for medium/heavy drinkers and 0.57 (95% CI, 0.36-0.91) for never/light drinkers. Moderately increased risks were observed for the ADH1C 350Val allele (OR, 1.19; 95% CI, 0.98-1.55) and ADH1C 272Gln allele (OR, 1.24; 95% CI, 0.98-1.55). Medium/heavy drinkers who were heterozygous or homozygous at ALDH2 nucleotide position 248 were at a significantly increased risk of upper aerodigestive tract cancer (OR, 1.76; 95% CI, 1.13-2.75; OR, 5.79; 95% CI, 1.49-22.5, respectively), with a significant dose response for carrying variant alleles (P = 0.0007). Similar results were observed for the ALDH2 +82A>G and ALDH2 −261C>T polymorphisms. When results were analyzed by subsite, strong main effects were observed for squamous cell carcinoma of the esophagus for all six variants. Among the 30% of the population who were carriers of at least one ALDH2 variant, the attributable fraction among carriers (AFc) was 24.2% (5.7-38.3%) for all upper aerodigestive tract cancers, increasing to 58.7% (41.2-71.0%) for esophageal cancer. Among carriers who drank alcohol at least thrice to four times a week, the AFc for having at least one ALDH2 variant was 49% (21.3-66.8%) for all upper aerodigestive tract cancers, increasing to 68.9% (42.9-83.1%) for esophageal cancer. Conclusions: Polymorphisms in the ADH1B and ALDH2 genes are associated with upper aerodigestive tract cancer in Central European populations and interact substantially with alcohol consumption. (Cancer Epidemiol Biomarkers Prev 2006;15(4):696–703)

Effect of cruciferous vegetables on lung cancer in patients stratified by genetic status: a mendelian randomisation approach

Whether consumption of cruciferous vegetables protects against lung cancer is unclear, largely because of potential confounding factors. We therefore studied the role of cruciferous vegetables in lung cancer after stratifying by GSTM1 and GSTT1 status, two genes implicated in the elimination of isothiocyanates, the likely chemopreventative compound. In 2141 cases and 2168 controls, weekly consumption of cruciferous vegetables protected against lung cancer in those who were GSTM1 null (odds ratio=0.67, 95% CI 0.49-0.91), GSTT1 null (0.63, 0.37-1.07), or both (0.28, 0.11-0.67). No protective effect was seen in people who were both GSTM1 and GSTT1 positive (0.88, 0.65-1.21). Similar protective results were noted for consumption of cabbage and a combination of broccoli and brussels sprouts. These data provide strong evidence for a substantial protective effect of cruciferous vegetable consumption on lung cancer.

Functional consequences of ATM sequence variants for chromosomal radiosensitivity.

The ATM [for ataxia‐telangiectasia (A‐T) mutated] protein plays a key role in the detection and cellular response to DNA double‐strand breaks. Several single‐nucleotide polymorphisms (SNPs) have been described in the ATM gene; however, their association with cancer risk or radiosensitivity remains to be fully established. In this study, the functional consequences of specific ATM SNPs on in vitro radiosensitivity, as assessed by micronuclei (MN) formation, were measured in lymphoblastoid cell lines established from 10 breast cancer (BC) patients carrying different ATM missense SNPs, six A‐T patients, six A‐T heterozygotes (A‐T het), and six normal individuals. The BC, A‐T het, and A‐T cell line groups showed significantly higher mean levels of MN formation after exposure to ionizing radiation (IR) than did the group containing normal cell lines, with similar levels in the BC and A‐T het groups. Within the BC lines studied, the group composed of the six carrying the linked 2572T>C (858F>L) and 3161C>G (1054P>R) variants had a higher level of MN after IR exposure compared to that observed in the remaining four BC or in the normal cell lines. This increase was not related to the constitutive ATM mRNA level, which was similar in these BC and the normal cell lines. Our results indicate that alterations in the ATM gene, including the presence of heterozygous mutations and the 2572C and 3161G variant alleles, are associated with increased in vitro chromosomal radiosensitivity, perhaps by interfering with ATM function in a dominant‐negative manner.

ATM polymorphisms as risk factors for prostate cancer development

The risk of prostate cancer is known to be elevated in carriers of germline mutations in BRCA2, and possibly also in carriers of BRCA1 and CHEK2 mutations. These genes are components of the ATM-dependent DNA damage signalling pathways. To evaluate the hypothesis that variants in ATM itself might be associated with prostate cancer risk, we genotyped five ATM variants in DNA from 637 prostate cancer patients and 445 controls with no family history of cancer. No significant differences in the frequency of the variant alleles at 5557G>A (D1853N), 5558A>T (D1853V), ivs38-8t>c and ivs38-15g>c were found between the cases and controls. The 3161G (P1054R) variant allele was, however, significantly associated with an increased risk of developing prostate cancer (any G vs CC OR 2.13, 95% CI 1.17–3.87, P=0.016). A lymphoblastoid cell line carrying both the 3161G and the 2572C (858L) variant in the homozygote state shows a cell cycle progression profile after exposure to ionising radiation that is significantly different to that seen in cell lines carrying a wild-type ATM gene. These results provide evidence that the presence of common variants in the ATM gene, may confer an altered cellular phenotype, and that the ATM 3161C>G variant might be associated with prostate cancer risk.

Inherited Predisposition of Lung Cancer: A Hierarchical Modeling Approach to DNA Repair and Cell Cycle Control Pathways

The DNA repair systems maintain the integrity of the human genome and cell cycle checkpoints are a critical component of the cellular response to DNA damage. We hypothesized that genetic variants in DNA repair and cell cycle control pathways will influence the predisposition to lung cancer, and studied 27 variants in 17 DNA repair enzymes and 10 variants in eight cell cycle control genes in 1,604 lung cancer patients and 2,053 controls. To improve the estimation of risks for specific variants, we applied a Bayesian approach in which we allowed the prior knowledge regarding the evolutionary biology and physicochemical properties of the variant to be incorporated into the hierarchical model. Based on the estimation from the hierarchical modeling, subjects who carried OGG1 326C/326C homozygotes, MGMT 143V or 178R, and CHEK2 157I had an odds ratio of lung cancer equal to 1.45 [95% confidence interval (95% CI), 1.05-2.00], 1.18 (95% CI, 1.01-1.40), and 1.58 (95% CI, 1.14-2.17). The association of CHEK2 157I seems to be overestimated in the conventional analysis. Nevertheless, this association seems to be robust in the hierarchical modeling. None of the pathways seem to have a prominent effect. In general, our study supports the notion that sequence variation may explain at least some of the variation of inherited susceptibility. In particular, further investigation of OGG1, MGMT, and CHEK2 focusing on the genetic regions where the present markers are located or the haplotype blocks tightly linked with these markers might be warranted. (Cancer Epidemiol Biomarkers Prev 2007;16(12):2736–44)

Cellular responses to ionising radiation of AT heterozygotes: differences between missense and truncating mutation carriers

It has been estimated that approximately 1% of the general population are ataxia telangiectasia (AT) mutated (ATM) heterozygotes. The ATM protein plays a central role in DNA-damage response pathways; however, the functional consequences of the presence of either heterozygous truncating or missense mutations on ATM expression and the ionising radiation (IR)-induced cellular phenotype remain to be fully determined. To investigate this relationship, the ATM mRNA and protein levels and several cellular end points were characterised in 14 AT heterozygote (AT het) lymphoblastoid cell lines, compared to normal and AT homozygote lines. The AT het cell lines displayed a wide range of IR-induced responses: despite lower average levels of ATM mRNA and protein expression compared to normal cells, 13 out of 14 were capable of phosphorylating the ATM substrates p53-ser15 and Chk2, leading to a normal cell cycle progression after irradiation. However, cell survival was lower than in the normal cell lines. The presence of a missense compared to a truncating mutation was associated with lower cell survival after exposure to 2 Gy irradiation (P=0.005), and a higher level of ATM mRNA expression (P=0.047). Our results underline the difficulty in establishing a reliable test for determining ATM heterozygosity.

Sequence Variants in Cell Cycle Control Pathway, X-ray Exposure, and Lung Cancer Risk: A Multicenter Case-Control Study in Central Europe

Exposure to ionizing radiation (IR) results in various types of DNA damage and is a suspected cause of lung cancer. An essential cellular machinery against DNA damage is cell cycle control, which is regulated by several genes, including TP53, CCND1, and CDKN2A. Therefore, we hypothesized that the genetic variants in these three genes influence the predisposition of lung cancer (i.e., CCND1 G870A, CDKN2A Ala(148)Thr, TP53 Arg(72)Pro, and 16-bp repeat in intron 3) and that the effect of X-ray on lung cancer risk can be modified by the presence of these genetic variations. The study was conducted in 15 centers in 6 countries of Central Europe between 1998 and 2002. A total of 2,238 cases and 2,289 controls were recruited and provided DNA samples. Cases with positive family history were analyzed separately. The joint effect of X-ray and previous risk genotypes was assessed, and modification by sequence variants on X-ray dose-response relationship with lung cancer risk was evaluated. We found an overall effect of TP53 intron 3 16-bp repeats [odds ratio (OR), 1.99; 95% confidence interval (95% CI), 1.27-3.13], which was stronger among cases with family history of lung cancer (OR, 2.98; 95% CI, 1.29-6.87). In addition, our results suggested an interaction that was greater than multiplicativity between TP53 intron 3 16-bp repeats and multiple X-ray exposures (interaction OR, 5.69; 95% CI, 1.33-24.3). We did not observe a main effect of CCND1 G870A polymorphism; however, the dose-response relationship between lung cancer risk and X-ray exposures was modified by CCND1 genotype with no risk from X-ray exposures among subjects who carried G/G genotype, intermediate risk [trend OR for X-ray, 1.16; 95% CI, 1.05-1.27) among subjects with G/A genotype, and highest risk [trend OR for X-ray, 1.29; 95% CI, 1.12-1.49) among subjects with A/A genotype. Sequence variants in cell cycle control pathway may increase the risk of lung cancer and modify the risk conferred by multiple X-ray exposures. However, a definite conclusion can only be drawn on replication by different studies among individuals who are highly exposed to IR.

Re: correspondence from Dr. Michael Swift, Disease Insight Research Foundation, concerning Gutiérrez-Enríquez S, Fernet M, Dörk T, Bremer M, Lauge A, Stoppa-Lyonnet D, Moullan N, Angèle S, Hall J, “Functional consequences of the ATM sequence variants for chromosomal radiosensitivity”

We welcome the opportunity to comment on the issues raised by Dr. Swift based on our article Gutiérrez-Enrı́quez et al. (2004), “Functional consequences of the ATM sequence variants for chromosomal radiosensitivity”. In this article, we reported on our investigation of whether certain variants in the ATM gene are associated with altered in vitro chromosomal radiosensitivity exploiting the micronucleus formation assay to provide evidence for increased sensitivity in carriers of some but not all ATM missense variants. This project is part of ongoing research in our laboratories aimed at investigating the relationship between sequence variants and cancer risk and in particular whether such genetic variants have functional consequences that may modify the cellular response to DNA damaging agents. It was our intention neither to obscure known facts about the association of ataxia-telangiectasia (A-T) mutations and breast cancer predisposition nor to claim priority for hypothesizing this association. The sentence about “our” hypothesis is far from representing a priority claim and was simply meant to designate “the” hypothesis that was the initial reason for “our” research study. As we did state in our article, several epidemiological studies on A-T families over the past 30 years have shown clear evidence that heterozygous carriers of A-T-causing mutations have an increased breast cancer risk. We are well aware of the excellent article by Athma et al. (1996), which falls into this category, and its omission in the reference list was an oversight on our part for which we apologize. We fully agree with Dr. Swift in the opinion that the epidemiological evidence for an association of A-T heterozygosity with breast cancer is strong. But we also have to recognize that an association between ATM gene mutations and breast cancer has been demonstrated in some but not all published studies outside the setting of A-T families. These breast cancer patients screened have been a heterogeneous group, including breast cancer cases with a strong family history or early onset of disease, unselected cases from the general population, and cases who show unusually high sensitivity to therapeutic radiation. As mentioned by Dr. Swift, some studies are based on small numbers of cases and controls, and with hindsight, some have used suboptimal mutation detection technology in the sense that the full spectra of ATM mutations could not have been detected. While the conclusions that can be drawn from these latter studies may be limited in terms of associations with breast cancer risk, they have allowed the frequency of truncating ATM mutations to be documented and thus make an important contribution to our understanding of the impact of this mutation type in several populations. To rank the usefulness of a particular study is a difficult task, and the categories may to some extent depend on the viewpoint. In this respect, we are intrigued by Swift’s stating that the publication by Atencio et al. (2001) can be considered both as a rigorous study and as one that uses inadequate mutation detection technology. Dr. Swift takes us to task over the introductory sentence of our discussion in which we state that “the relationship between the presence of ATM mutations or sequence variants and breast cancer predisposition remains controversial in part because of the low frequency at which such alterations have been detected in this population and the uncertainty of their biological and functional significance.” We still feel that this introductory sentence reflects the published literature at the present time on the association between common sequence variants in the ATM gene and breast cancer predisposition, but we also recognize that if misquoted and thus taken out of context, it could be misleading. One important issue that arises from a review of the published studies is the mixed use of terms such as ATM “mutations”, “polymorphisms,” and “sequence variants,” which are not interchangeable, to describe the different sequence alterations