Metabolic gene polymorphisms and p53 mutations in healthy centenarians and younger controls

L. GASPARI

, P. PEDOTTI

, M. BONAFE`

, C. FRANCESCHI

, D. MARINELLI

, D. MARI

, S. GARTE

and E. TAIOLI

*

Genetic and Molecular Epidemiology Unit, IRCCS  Ospedale Policlinico di Milano, / Milan, Italy

Department of Experimental Pathology, University of Bologna, Bologna, Italy

Institute of Internal Medicine, University of Milan, Milan, Italy

2 Department of Experimental Pathology, University of Bologna, Bologna, Italy 3 Institute of Internal Medicine, University of Milan, Milan, Italy 4 Genetics Research Institute, Strada della Carita` 10, 20135, Milan, Italy

Received 21 May 2003, revised form accepted 25 September 2003

To obtain insights into the genetic mechanisms of ageing, we studied the frequency of the simultaneous presence of polymorphisms in phase I and phase II genes and of several p53 germline mutations in a group of 66 nonagenarians and centenarians in good health, selected from a larger sample of a multicentre Italian study in Northern Italy, and in a sample of 150 young healthy volunteers of the same ethnic group. We found a statistically significant difference in the frequency of the GSTT1 deletion and the p53 genotypes: the absence of any p53 polymorphisms and of GSTT1 deletion, and the simultaneous presence of the three p53 polymorphisms and of GSTT1 deletion, were much more frequent in young subjects than in centenarians (41.5% versus 26.9% and 8.8% versus 3.8%, respectively). One hypothesis to explain this difference is that subjects with both GSTT1 deletion and p53 polymorphisms may accumulate carcinogens and may have reduced DNA repair ability, and thus are more at risk for cancer. Another possible explanation is that both metabolic genes and p53 act on pathways related to cell ageing and death, and therefore certain composite genetic patterns could represent a generic mechanism of protection against ageing, not just against the development of chronic diseases. It is likely that longevity is related to a complex genetic trait as well as to certain environmental exposures.

Keywords: ageing, molecular epidemiology, chronic diseases.

Introduction

Centenarians who have managed to reach the extreme limit of human life in good health are the best example of successful ageing. It is possible that they were able to escape the major diseases associated with age as a result of optimal environmental conditions and good lifestyle habits combined with some genetically determined resistance against age-associated diseases (Johnson 1997). Recently a possible antagonism between living to an old age and getting cancer has been suggested (Leroi et al. 2003).

Individual susceptibility to environmental carcinogens and toxicants is by genetic differences. Many enzymes are involved in the metabolism of and endogenous carcinogens. These enzymes are the products of two major families: phase 1 (such as the CYP family) and phase 2 (such as the GST, NAT EH families). Polymorphisms in these genes are very common in the

*Corresponding author: Emanuela Taioli, Molecular and Genetic Epidemiology Unit, Padiglione Marangoni, Ospedale Policlinico IRCCS, Via F. Sforza 35, 20122 Milano, Italy. Tel: ((cid:2)39) 02 / 55034055; fax: ((cid:2)39) 02 55034055; e-mail: epidemiologia@policlinico.mi.it /

Biomarkers ISSN 1354-750X print/ISSN 1366-5804 online # 2003 Taylor & Francis Ltd http://www.tandf.co.uk/journals DOI: 10.1080/13547500310001627519

Metabolic gene polymorphisms and p53 mutations in healthy centenarians

population (Garte et al. 2001) and are associated with various types of cancer (D’Errico et al. 1999). We have previously found a significant increase in homozygous deletion of the GSTT1 gene in Italian nonagenarians compared with young healthy subjects (Taioli et al. 2001).

The homozygous CYP1A1 Msp1 restriction fragment length polymorphism (RFLP) has been found to affect levels of expression of the gene (Garte et al. 2003), and has been shown to be associated with lung cancer in Europeans (Vineis et al. 2003). The heterozygote polymorphism has not been found to have any phenotypic effect.

p53 is a nuclear protein that plays a major role in tumour suppression via its involvement in multiple pathways, including apoptosis, cell cycle regulation and arrest, cellular transcriptional control and DNA repair. The p53 gene is located on chromosome 17p13, and is one of the most commonly mutated genes in different types of human cancer (Hollstein et al. 1991). Besides the known example of germline mutations as the basis of the rare, familial Li-Fraumeni syndrome (Law et al. 1991), other more common polymorphisms have been found in this gene: in codon 72 in exon 4, a G0C transversion leads to an arginine (Arg) to proline (Pro) / change (Miller et al. 2002); in intron 6 there is an Msp1 RFLP consisting of either six or eight variable bases (McDaniel et al. 1991), and a 16 bp duplication has been described in intron 3 (Lazar et al. 1993). These polymorphisms have been associated with lung cancer (Birgander et al. 1995, Biros et al. 2001), breast cancer (Sja¨lander et al. 1996, Wang-Gohrke et al. 2002), ovarian cancer (Wang- Gohrke et al. 1999) and bladder cancer (Biro et al. 2000). A previous study showed no differences in genotype frequency between healthy centenarians and controls (Bonafe` et al. 1999). Two studies on lung cancer looked at the combined effect of both p53 codon 72 polymorphism and GSTs polymorphisms. Both studies showed an increased risk of lung cancer when the combined genotypes were present (Liu et

Recently it has been demonstrated that the two p53 variants at codon 72 are not functionally equivalent, either biochemically or biologically: they have different gene expression activities in inducing apoptosis and suppressing transfor- mation, with the p53Arg variant more efficient than the p53Pro (Thomas et al.