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M T Landi

Publications and source records attributed to M T Landi.

31 records · Page 2Linked to original sources
PubMed1994

Association between CYP1A1 genotype, mRNA expression and enzymatic activity in humans.

Genetic susceptibility factors may play a role in determining adverse effects of exposure to environmental toxins. As a preliminary step to a molecular epidemiological study in a population exposed to 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD), we investigated 20 healthy Caucasian volunteers with a set of putative susceptibility markers including a CYP1A1 Msp I restriction fragment length genetic polymorphism (RFLP), CYP1A1 mRNA expression, and ethoxyresorufin-O-deethylase (EROD) activity in cultured and mitogen-activated blood lymphocytes. Both basal (p = 0.008) and induced (p = 0.0001) EROD activity was significantly higher among persons with a mutation in one or both alleles of the CYP1A1 gene (variant CYP1A1 genotype). Induction in vitro by TCDD significantly increased EROD activity in both variant and wild-type CYP1A1 subjects; however, the absolute increase was greater in subjects with variant genotypes. An additive interaction between genotype and TCDD induction was suggested. Expression of CYP1A1 mRNA, both basal and induced, did not vary significantly across the genotypes.

Adult↗
PubMed1993

Cancer incidence in a population accidentally exposed to 2,3,7,8-tetrachlorodibenzo-para-dioxin.

In 1976, an accident in a plant near Seveso, Italy, exposed the local population to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Persons residing in three zones of decreasing TCDD contamination (A, B, and R) and a reference population were followed up for cancer occurrence in 1977-1986. The most exposed subgroup (A) was small, and only 14 cancer cases were observed. In zone B, hepatobiliary cancer was elevated, especially for those living in the area for > 5 years [relative risk (RR) = 2.8; 95% confidence interval (CI) = 1.2-6.3]. Men exhibited an increase in hematologic neoplasms, most notably lymphoreticulosarcoma (RR = 5.7; 95% CI = 1.7-19.0). Women experienced an increased incidence of multiple myeloma (RR = 5.3; 95% CI = 1.2-22.6) and myeloid leukemia (RR = 3.7; 95% CI = 0.9-15.7). In zone R, the incidence of soft tissue tumors and non-Hodgkin's lymphomas was elevated, particularly among persons living in the area for > 5 years (RR = 3.5; 95% CI = 1.2-10.4 for sarcomas, and RR = 2.0; 95% CI = 1.2-3.6 for non-Hodgkin's lymphomas). Breast cancer among females was below expectations in the most contaminated zones, and a clear deficit for endometrial cancer was observed in zones B and R.

Adult↗
PubMed1992

Mortality of a young population after accidental exposure to 2,3,7,8-tetrachlorodibenzodioxin.

The mortality experience of 19,637 people aged 1-19 years living in an area around Seveso, Italy, contaminated by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) after an accidental explosion in a chemical plant was examined for the period 1976-1986. For comparison, the mortality of the population of nearly 100,000 people living in the surrounding districts was examined. People who left the study area were followed up. Vital status ascertainment was successful in over 99% of the cases. A group of 186 children who contracted chloracne, a reversible marker of TCDD intoxication, shortly after the accident were in the study: none of them died during the observation period. Among the exposed, mortality owing to all causes, to all accidents and to all cancers failed to show major departure from expectations. Five leukaemia deaths were observed, four among males and one among females; the corresponding relative risks were 2.1 (95% confidence interval (CI): 0.7-6.9), and 2.5 (95% CI: 0.2-27.0), respectively. Two lymphatic leukaemias among males yielded a RR = 9.6 (95% CI: 0.9-106.0). Mortality owing to congenital anomalies showed a nearly twofold increase in the contaminated area; however, five out of seven observed cases were born before the accident. Interpretation is limited by the small number of deaths, short latency period and low validity of death certificate information for certain causes, and by the definition of exposure which was based merely on residence. The follow-up is continuing. A cancer morbidity study is in progress.

Adolescent↗
PubMed1992

The debrisoquine metabolic phenotype and DNA-based assays: implications of misclassification for the association of lung cancer and the debrisoquine metabolic phenotype.

Debrisoquine is an antihypertensive drug that is metabolized by cytochrome P4502D6. Deficient metabolism is inherited as an autosomal recessive condition. We previously reported in a case-control study that extensive metabolizers of debrisoquine were at greater risk of lung cancer compared to poor and intermediate metabolizers. Cloning of the gene that encodes P4502D6 (CYP2D6) led to the identification of both wild-type and mutant forms of the gene. Subsequently, a DNA-restriction fragment length polymorphism (RFLP) was identified, and a Southern hybridization-based test was developed in an attempt to define the genotype. When the DNA-RFLP test was applied to stored DNA from our study subjects there was neither a significant association with the metabolic phenotype nor an association with lung cancer. Further work has demonstrated that the wild-type gene, which was characterized by a 29-kb allele, can also contain mutations that result in nonfunctional or absent proteins. When these mutations are present, individuals exhibit the poor or intermediate metabolizer phenotype in spite of the presence of the 29-kb putative wild-type allele. Sequence determination of the mutants led to the development of techniques to exploit the polymerase chain reaction, which, together with Southern analysis, have been reported to detect as many as 95% of poor metabolizers. This technique is being used to examine the association of the extensive metabolizer genotype with lung cancer in the subjects from the case-control study. Preliminary results indicate a weak association between the homozygous wild-type genotype and lung cancer; in contrast, the extensive metabolizer phenotype is strongly associated with lung cancer in this subset.(ABSTRACT TRUNCATED AT 250 WORDS)

Case-Control Studies↗
PubMed1991

Relevance of metabolic polymorphisms to human carcinogenesis: evaluation of epidemiologic evidence.

Genetic modulation of environmental exposures associated with common malignancies (lung and bladder) is an attractive mechanism to explain differential susceptibility to tobacco or occupation related carcinogens in the population. Epidemiologic studies to test the hypothesis of such associations and to evaluate evidence for a causal role for genetic factors in the etiology of chemically-induced tumors are challenging and require the close collaboration of epidemiologists, clinicians and laboratory investigators. In this work we review the evidence for an association of three polymorphisms of drug or xenobiotic metabolism with human cancers. Methodologic considerations and data relevant to evaluating a causal role for each polymorphism are considered. Fair to good support for both an association of the acetylation phenotype with occupationally-related bladder cancer and for an association of the debrisoquine metabolic phenotype and lung cancer is found, although in neither case is the evidence completely convincing. Epidemiologic evidence for the association of aryl hydrocarbon hydroxylase and lung cancer is presently problematic because of difficulties in the assay and subsequent confounding factors. DNA based assays are at various stages of development for each of the genotypes and promise to simplify future studies while introducing new methodologic pitfalls. Further studies in all three areas are warranted as each has important implications for the understanding of the carcinogenic process, etiology and the public health aspects of common malignancies.

Age Factors↗
PubMed1988

Effects of prolonged picotamide therapy on platelet activity in patients with peripheral arterial disease.

An open study was carried out in 14 patients with peripheral arterial disease to investigate the effects of prolonged therapy with picotamide on platelet activity. Patients received daily oral doses of 900 mg picotamide for 1 month, 600 mg per day during the second month and 300 mg per day from the third to the sixth month of the study. Measurements were made before and during therapy of blood coagulation parameters and factors influencing platelet function, i.e. plasma beta-thromboglobulin and serum thromboxane B2. The results showed that there were no significant variations in platelet count, prothrombin time, partially activated thromboplastin time, presence and amount of fibrinogen in blood, and antithrombin III. Examination for fibrinogen degradation products was constantly negative and unaltered during therapy. Although plasma beta-thromboglobulin values did not vary significantly, there was a significant and progressive reduction throughout treatment in serum levels of thromboxane B2.

Aged↗
PubMedDate not supplied

[Occupational epidemiology and new challenges in occupational medicine].

Epidemiology has greatly contributed in the past to the recognition of work-related ill health. Working life, work organisation and labour markets are now rapidly changing. Does epidemiology still have a relevant role in this evolving context? New exposures at the workplace and related health and behavioural changes currently prevailing in industrialized countries are reviewed. It appears that epidemiology might in the future play an even greater role than in the past, when the mere observation of a few subjects could sometimes lead to the identification of occupation-related risks. In order to examine the relations between complex and low-level exposures and subtle and long-term risks in working populations, epidemiology appears essential. Controlled, longitudinal population studies are especially needed to clarify, for prevention purposes, the meaning and the predictive role of the increasing number of markers of exposure, of effect and of individual susceptibility; to describe and model in quantitative terms exposure-response relations; to assist with risk assessment and evaluation. Although occupational health research has a long tradition of inter-disciplinary co-operation, this remains a major challenge for the future.

Animals↗
PubMedDate not supplied

[Metabolic polymorphisms and the cancer risk: the evaluation of epidemiological studies].

Genetic modulation of environmental exposures associated with common malignancies is an attractive mechanism to explain differential susceptibility to tobacco or occupation-related carcinogens in the population. The paper reviews the evidence for an association between three genetically based metabolic polymorphisms (N-acetyltransferase, Debrisoquine, hydroxylase, aryl hydrocarbon hydroxylase), which have been implicated in the modulation of lung or bladder cancer risks. Fair to good support emerged for both an association of the acetylation phenotype with occupationally related bladder cancer and for an association of the debrisoquine metabolic phenotype with lung cancer, although in neither case was the evidence completely convincing. Epidemiologic evidence for an association between aryl hydrocarbon hydroxylase and lung cancer is presently problematic because of the difficulties in the assay and subsequent confounding factors.

Acetyltransferases↗
PubMedDate not supplied

[Molecular epidemiology for the study of the environment-genome interaction].

The study of the gene-environment interaction considered initially genes involved in the biotransformation of carcinogenic agents. Genetic polymorphisms are useful markers of individual susceptibility, provided that their association with the exposure and the outcome of interest are clearly understood. The availability of biochemical and molecular markers in epidemiology research has been greeted as a major step forward from the traditional "black box" epidemiology, and certainly represents a real advancement in knowledge. Yet, the advancement in research made possible by the adoption of molecular biomarkers in epidemiological studies still needs to be evaluated as a relevant and effective tool for a more adequate prevention of the adverse effects caused by environmental agents.

Environment↗
PubMedDate not supplied

A study of gender-based cytochrome P4501A2 variability: a possible mechanism for the male excess of bladder cancer.

One hypothesis for the well known gender difference in bladder cancer risk is that males and females metabolize carcinogens differently. The caffeine breath test (CBT) was performed on a group of healthy men and women to determine whether there was a gender difference in P4501A2 activity. Results consistent with previous data suggest an elevation of CBT in men were observed, although this increase was not statistically significant. Among women, however, there was a significant difference between nulliparous and parous women(P = 0.03). Parous women had CBT values similar to men, whereas the results of women who had never given birth were lower. Confirming earlier studies, women taking oral contraceptives had low CBT values. Our data suggest an effect of recent caffeine consumption, with heavy coffee drinkers having higher rates of caffeine clearance. Adjustment for other weak effects, such as age, exposure to environment cigarette smoke, history of smoking, recent meat and cruciferous vegetable consumption, and use of alcohol or other medications, did not alter these findings. The finding of a difference between parous and nulliparous women requires further study.

Adult↗
PubMedDate not supplied

Molecular epidemiology: a new perspective for the study of toxic exposures in man. A consideration of the influence of genetic susceptibility factors on risk in different lung cancer histologies.

This data in the aggregate suggests that the 3 best studied genetic susceptibility factors (CYP2D6 extensive metabolizers, GST mu null phenotype, and CYP1A1 "mutant" alleles in Asians only) constitute greater risk factors for the more smoking related histologies of lung cancer, but not for adenocarcinoma. The epidemiologic evidence for a these genetic susceptibility factors in tobacco-related cancer is suggestive but not determinant. A consensus estimate of relative risk for extensive metabolizers of debrisoquine is around 2. Variability in study results depend on a number of factors which include: assay misclassification, non-correspondence of phenotype/genotype in certain subjects, disease heterogeneity, exposure variation, ethnic and racial variation. Future studies should emphasize: a high quality approach to data gathering, careful attention to epidemiologic design, and the use of intermediate markers where feasible. Investigators should consider the use of multiple genetic markers since PCR approaches can make this an efficient approach. A meta-analysis may serve to illuminate points of heterogeneity between studies. New discoveries should provide opportunities to explore for analogous associations in other malignancies. It may be speculated that the "specificity" of the association observed for each of the genetic factors tends to support the general causal nature of the hypothesis. The fact that each shares the histologic preference at least suggests that a common mechanism may be operative. The observation that the tobacco-cancer association, though clearly present, is weaker for adenocarcinoma than for the other lung cancer histologies, suggests that the underlying mechanism involves some interaction of the genetic trait with exposure to tobacco smoking, and suggests further attention to this factor to elucidate differences in risk estimates for genetic susceptibility factors among different studies.

Disease Susceptibility↗
PubMedDate not supplied

[Bis-chloromethyl ether and carcinogenesis of alkylating agents].

Bis-Chloro-Methyl-Ether is an alkylating agent and a recognised carcinogen. It can form spontaneously from the reaction of chloridric acid with formaldehyde. In the past it was extensively used as a chemical intermediate in organic synthesis, particularly as a crosslinking agent in the manufacture of ion-exchange resins. Recently, since its carcinogenicity has been proved in animal studies and confirmed in epidemiological studies of occupationally exposed cohorts, its use has been consistently reduced. A characteristic association has been observed between BCME exposure and a peculiar lung cancer histotype (oat cell carcinoma). In spite of these data, little information is available on the molecular alterations related to BCME exposure and possibly to its carcinogenic activity. Some suggestions can reasonably be obtained considering how the class of alkylating agents acts. They form adducts, binding different positions of DNA bases. The reaction that seems more relevant for mutagenesis and carcinogenesis is the alkylation at the atom O6 of guanine in DNA, which is followed by mis-coding and GC-->AT transition mutation. This kind of alteration determines the activation of a group of enzyme like DNA repair, mismatch repair, excision repair and a specific one, methyl guanine methyl transferase (MGMT). This last repair protein transfers alkyl groups from the O6 position of guanine to an internal cysteine residue, inactivating itself. Thus, the possibility for the cell to eliminate alkylated DNA bases depends strictly upon the cellular content of MGMT. In this view reduced or absent levels of the enzyme are associated with an increased number of adducts and hence increased risk of DNA mutations and cancer. At the moment no molecular studies in vivo have been performed to verify this hypothesis. The peculiar association BCME-oat cell carcinoma, the most chemosensitive tumor, need further investigation.

Air Pollutants, Occupational↗