Search PubMed⌕ Search

Biomedical subjects

K Hemminki

Publications and source records attributed to K Hemminki.

At least 217 records · Page 12Linked to original sources

DNA adducts and mutations in occupational and environmental biomonitoring.

The methods applied for DNA adduct determination in humans have become more reliable. Yet there is a need to characterize the adducts studied better and when possible, to identify them with the help of the available standard compounds. Use of standard compounds also allows quantification of adduct levels. There is a lack of knowledge on the adduct levels and their half-lives in target and surrogate tissues. Most adduct studies have been carried out on occupational populations exposed to complex mixtures. White blood cells have been the most common source of DNA. Other exposures and tissues should be a subject of study. Notably, dietary exposures have been largely neglected. Biomonitoring of mutations is a relatively new field and a few exposures have so far been investigated. The results have been promising but logistics of the studies have to be improved to make large field studies possible. Future biomonitoring studies should make an effort to combine many end points, with emphasis on adducts, mutations, and constitutional metabolic factors.

DNA Adducts↗

Mutations, tissue accumulations, and serum levels of p53 in patients with occupational cancers from asbestos and silica exposure.

In order to determine the relationship between mutations, tissue accumulations, and serum levels of p53 in occupational cancers, we used denaturing gradient gel electrophoresis and DNA sequencing of exons 5-9 of the p53 gene, immunohistochemical analysis for tissue identification of mutant p53 protein, and enzyme-linked immunosorbent assay for serum levels of mutant p53 protein to examine for such alteration in a cohort of individuals with workplace exposure to asbestos or silica, and resultant lung cancers or mesotheliomas. DNA analysis detected mutations in 5 of 18 (28%) tumors, and tissue accumulations of protein were detected in 7 of 20 (35%) tumors; the agreement between mutational and immunohistochemical analyses was significant (kappa = 0.62, P = 0.002). Serum elevations of protein were detected in 4 of 11 (36%) cases with available serum samples; the agreement between tissue alterations and serum elevations was also significant (kappa = 0.71, P = 0.017). In addition, based on the analysis of banked samples, serum results tended to be consistent over time prior to the diagnosis of disease (positive predictive value = 0.67, negative predictive value = 0.83). These results suggest that serum levels of p53 are reasonably accurate in reflecting tissue alterations in p53 at the gene and/ or protein level and may be early biomarkers of disease risk.

Adult↗

Effect of paternal and maternal cancer on cancer in the offspring: a population-based study.

The Family-Cancer Database was constructed from the nationwide Swedish registries to include more than 30,000 cancers in offspring diagnosed at ages 15-51 years and their parents. Cancer risk in the offspring was increased about 1.10 times when the father had cancer, whereas no increase was noted when the mother had cancer. If both parents had cancer, the risk for sons was 1.39 and for daughters, 1.34. Familial aggregation between parents and offspring was observed for 5 concordant and 14 discordant cancer sites and 10 parental sites at which all cancer was increased in the offspring. The concordant sites between the parent and offspring were colorectum, breast, melanoma, skin (squamous cell carcinoma), and thyroid. The aggregation at discordant sites in the parents and the offspring included stomach-breast, colorectum-salivary glands, colorectum-breast, colorectum-lymphoma, colorectum-leukemia, liver-breast, pancreas-breast, breast-melanoma, ovary-breast, prostate-breast, prostate-cervix, prostate-multiple myeloma, kidney-melanoma, and nervous tissue-melanoma. In most of these combinations, cancer in the second parent increased the risk to the offspring. The present results on young and middle-aged adults suggest that cancer in both parents increases cancer risk in the offspring at many sites. Chance and environmental effects may explain some of the results, whereas true genetic factors probably contribute to most of the findings. The molecular genetic explanation may be that rare dominant single genes increase susceptibility at many sites or that overlapping sets of genes control susceptibility at multiple sites.

Adolescent↗

The non-random distribution of UV-induced photoproducts in the nuclear matrix and non-matrix DNA fractions.

The formation of UV-induced photoproducts in the chromatin fractions of human lymphocytes was studied by 32P-post-labeling. A higher level of DNA lesions was found in the matrix-attached DNA fraction as compared to non-matrix DNA of irradiated cells (about 150 and 110 adducts per 10(6) nucleotides, respectively, at a 500 J/m2 254 nm-UV dose). Formation of photoproducts in a MAR (matrix attached region) sequence from the mouse kappa immunoglobulin gene irradiated in vitro was examined as well. The MAR sequence showed a two-fold higher level of adducts as compared to non-MAR DNA. The effect of photoproducts on complex-formation between MAR DNA and proteins of the nuclear matrix was studied in vitro. The amount of UV-induced adducts was 1.5-fold higher in matrix-bound fraction as compared to non-fractionated DNA (and five-fold higher as compared to unbound fraction), which possibly resulted from preferential binding of lesion-containing DNA fragments to the nuclear matrix proteins.

Animals↗

Tamoxifen-induced DNA adducts in endometrial samples from breast cancer patients.

Tamoxifen-induced DNA adducts were analyzed with the (32)P-postlabeling method using high-performance liquid chromatography (HPLC)-radioactivity detection from endometrial tissue of breast cancer patients and controls. Liver DNA from tamoxifen-treated rats was used as a positive standard. In blind analysis, five of the seven samples from tamoxifen-treated patients showed DNA adducts; none of the five controls were positive. The identity of the tamoxifen adduct was confirmed by using different chromatographic systems, isolating the HPLC fractions and running them on TLC, with or without spiked rat liver samples. The level of adducts in the treated patients was 2.7 adducts/10(9) nucleotides in the HPLC analysis.

Aged↗

Aromatic DNA adducts in lymphocytes of humans working at high and low traffic density areas.

Aromatic DNA adduct levels were determined by the 32P-postlabelling assay in lymphocytes isolated from newspaper vendors working at urban high traffic areas (n = 31) and suburban low traffic areas (n = 22) in Milan, Italy. The DNA adduct levels ranged from 0.7 to 6.7/10(8) nucleotides, while most of them were between 1.0 and 3.0/10(8) nucleotides. No difference was found between the DNA adduct levels of the high-exposed group (2.2/10(8) and the low-exposed group (2.2/10(8). The heavy smokers (n = 8) had 23% higher DNA adduct level (2.7/10(8)) than the non-smokers (n = 37, 2.2/10(8) (P = 0.27), but no correlation was found between the adduct level and the number of cigarettes/day. Analysis of variance of the DNA adduct levels among the 14 pairs of individuals working at the same news-stands revealed little effect of the environmental air exposure on the DNA adduct level.

DNA Adducts↗

32P-postlabelling of bulky human DNA adducts enriched by different methods including immunoaffinity chromatography.

DNA adducts in lymphocytes and granulocytes of men exposed occupationally and environmentally to high concentrations of aromatic compounds in air were measured by the 32P-postlabelling method. Adducts in the same samples were characterized using nuclease P1 enrichment, butanol extraction and immunoaffinity purification with an antiserum raised against benzo[alpha]pyrene diol epoxide (BPDE). Only part of the adducts found in human samples were extracted by butanol. It also seemed, that only a small part of them belonged to the group of polycyclic aromatic hydrocarbons (PAHs) recognised by the antibody. Relative content of hydrophobic adducts and those with a structure similar to PAHs was higher in winter samples (when exposure to aromatic chemicals in air was higher) in comparison to samples collected in summer.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

Assessment of cancer hazard from environmental pollution in Silesia.

New concepts of cancer risk estimation have been developed during the past decade. Short-term bioassays dealing with mutagenicity and carcinogenicity of environmental samples are being replaced by more relevant molecular epidemiology studies. The general idea of using a battery of bioassays remains unchanged while the origin of tested samples is different. Instead of testing samples collected from the environment, body fluids or human cells from exposed populations are under investigation. This paper reviews the collaborative study on cancer risk assessment in highly polluted industrial region of Silesia in which both approaches had been employed during the 1985-1995 period. A potent carcinogenic activity of airborne pollutants was indicated in a battery of in vitro and in vivo short-term assays. These studies were followed by the molecular epidemiology study performed on human populations inhabiting the region of Silesia. An elevated damage of genetic material on the chromosome and/or DNA levels was observed in the Silesian populations as compared with proper rural controls.

Air Pollutants↗

Seasonal variation of DNA adduct pattern in human lymphocytes analyzed by 32P-HPLC.

32P-HPLC is a recently published method to generate DNA adduct profiles after exposure to a complex of genotoxic substances. The low detection limit enables characterization of individual DNA adducts in the general population. The 32P-HPLC method was applied to human lymphocytes and granulocytes from Silesia, a polluted industrial region in the south of Poland. Human samples were collected at the end of winter and summer to investigate the seasonal influence on DNA adduct formation. In lymphocytes a strong seasonal variation was seen in total DNA adducts, with winter values exceeding the summer values by 7.33 +/- 3.56 times. Granulocytes did not show any seasonal variation. In winter-collected lymphocytes the DNA adduct levels were 21.4 +/- 16.6/10(8) normal nucleotides (NN) while the summer values were 2.96 +/- 2.46/10(8) NN. Granulocytes had 8.06 +/- 7.76 and 9.59 +/- 6.19 DNA adducts/10(8) NN during winter and summer respectively. The lymphocyte DNA adduct profile consisted of at least 16 individual or clusters of DNA adducts. All 16 had a clear winter influence, with a winter:summer ratio of 1.6-15.3, indicating exposure to a complex mixture of genotoxic substances. The DNA adducts analyzed in human lymphocytes had retention times similar to DNA adducts generated by polycyclic aromatic hydrocarbons. The suggested candidates for DNA adducts displayed a similar seasonal variation in airborne particles to that found in DNA adducts in lymphocytes of humans living in the area. This is the first application of the 32P-HPLC method to analysis of DNA adducts in human tissues.

Air Pollutants↗

Adduct formation on DNA and haemoglobin in mice intraperitoneally administered with styrene.

Styrene-specific N-7- and O6-guanine DNA adducts and N-terminal valine adducts were determined in mice tissues after the intraperitoneal administration of styrene. Blood, liver, lungs and spleen were collected 3 h after administration of various doses (from 0 to 4.35 mmol/kg b.w.) of styrene. DNA adducts were analysed by the modified 32P-postlabelling assay and N-terminal valine adducts were detected by GC-MS according to the modified Edman degradation technique. In the dose-range studied, for all adducts a clear dose-response relationship was observed. 7-Alkylguanines and O6-styrene guanine adducts were most abundant in lungs, approximately 30% more than in liver and spleen. In all analysed tissues 7-alkylguanines were more abundant than O6-styrene guanine adducts. We found a considerably lower rate of N-terminal valine adduct formation as compared with both DNA adducts. The ratio between 7-alkylguanines and O6-guanine adducts was 1.9, 1.6 and 7.8 in liver, lung and spleen, respectively. In vitro determination of both DNA adducts by 32P-postlabelling resulted also in a lower ratio than that reported earlier using an HPLC analysis. All correlation's between dose, haemoglobin and DNA adducts were very high and significant. However, at the highest injected doses the adduct formation showed a levelling off. To explain this phenomenon a model simulation was performed revealing that 3 h after the injection of the higher doses styrene was not completely converted into styrene-7,8-oxide.

Animals↗

Separation of 7-methyl- and 7-(2-hydroxyethyl)-guanine adducts in human DNA samples using a combination of TLC and HPLC.

We have used a combination of thin-layer chromatography (TLC) and high pressure liquid chromatography (HPLC) to achieve separation of 32P-postlabelled 7-methylguanine and 7-(2-hydroxyethyl)-guanine adducts. The level of these two adducts was determined in human total white blood cells (mean values 0.7 to 1.5 adducts per 10(7) normal nucleotides) and isolated lymphocytes (mean values 1.1 to 12 adducts per 10(7) normal nucleotides). The separation of these two adducts revealed that the level of 7-(2-hydroxyethyl)-guanine was twice the level of 7-methylguanine adducts in total white blood cells, whereas, in isolated lymphocytes it was at least four times more than the 7-methylguanine adduct. The combined level of these two adducts in the lymphocytes of non-smokers was 1.1 to 8.4 adducts per 10(7) normal nucleotides and in the lymphocytes of smokers, the level was 5.6 to 12 adducts per 10(7) normal nucleotides. We also report detection of three unidentified adducts in the samples analysed, and at least one of these adducts seemed to be related to smoking. The chromatographic behaviour and depurination at neutral pH indicated the probable 7-alkylguanine or 3-alkyladenine nature of these unidentified adducts.

Chromatography, High Pressure Liquid↗

Tobacco smoke-associated N7-alkylguanine in DNA of larynx tissue and leucocytes.

The presence of N7-alkylguanine adducts in DNA was analysed in a group of 46 patients with larynx tumours. All patients were subjected to laryngectomy and the tissues accessible for analysis by (32)P-post-labelling assay were larynx tumour, larynx non-tumour and peripheral blood leucocytes. N7-Alkylguanine adducts were detected in all the studied DNA samples. The average level of N7-alkylguanines was 26.2/10(7) nucleotides in tumour cells, 22.7/10(7) in non-tumour cells and 13.1/10(7) in blood leucocytes. There was significantly higher level of N7-alkylguanines in the larynx tissues in males than in females. The effect of tobacco smoking on DNA adduct levels was shown by an increase in the average levels of N7-alkylguanines in the subject groups classified according to their smoking habits. A moderate age-related increase in levels of N7-alkylguanine was demonstrated in larynx tumour tissue. The levels of N7-alkylguanine adducts in larynx cells were compared with that of aromatic DNA adducts. Pearson correlation coefficients (0.28 for tumour tissue and 0.30 for non-tumour tissue) indicate independent formation and removal of N7-alkylguanine and aromatic DNA adducts resulting from tobacco smoke exposure.

Adult↗

7-Alkylguanine adducts of styrene oxide determined by 32P-postlabeling in DNA and human embryonal lung fibroblasts (HEL).

The modified 32P-postlabeling method was used for the detection of N-7-(2-hydroxy-phenylethyl) guanine adducts in DNA and human embryonal lung (HEL) cells treated in vitro with styrene oxide (SO). The total recovery of 7-alkylguanine adducts of styrene oxide in DNA analysed by 32P-postlabeling assay was 4.1 +/- 0.6%. The disappearance of 7-alkyldeoxyguanosine monophosphate adducts from SO-modified DNA at 37 degrees C showed a half-life of 19 h. The levels of 7-alkylguanine DNA adducts and single-strand breaks (SSBs) in DNA were determined in HEL cells treated with SO for 3 and 18 h. In the 3 h treatment there was a concentration-dependent increase of both 7-alkylguanine adducts and SSBs in DNA (r = 0.98, P = 0.012 and r = 0.99, P = 0.003, respectively). We found a significant correlation between 7-alkylguanine DNA adducts and SSBs in DNA (r = 0.98, P = 0.011). In HEL cells approximately 3-fold higher levels of both 7-alkylguanine DNA adducts and SSB in DNA were found after the SO (100 microM) treatment for 3 h than after the treatment for 18 h. A significant concentration-dependent increase was found only for SSB ( r = 0.95, P = 0.024) in the 18 h treatment with SO. There was no significant correlation between 7-alkylguanine adducts and SSBs (r = 0.72, P = 0.15). Our data suggest relatively fast removal of both 7-alkylguanine adducts of SO and DNA SSBs.

Autoradiography↗

32P-postlabelling of diastereomeric 7-alkylguanine adducts of butadiene monoepoxide.

The reaction of 3,4-epoxy-1-butene (BMO) with deoxyguanosine-3'-monophosphate (3'-dGMP) resulted in the formation of two pairs of diastereomeric 7-alkyl-3'-dGMP derivatives corresponding to two isomers C¿-1 and C¿-2. The T4 polynucleotide kinase-mediated phosphorylation with [gamma-32P]-ATP showed preferential labelling of diastereo- mers of the C¿-1 isomer. The diastereomers 1 and 2 of the C¿-1 isomer had labelling efficiencies of 42%. However, the labelling efficiencies of diastereomers 3 and 4 of the C¿-2 isomer were 11 and 10%, respectively. The 32P-postlabelling of BMO-modified DNA yielded four isomers in the ratio of 4:4:1:1 with overall recoveries being 14%. The two isomers had a half-life of 270 min (C¿-1 isomer) and 300 min (C¿-2 isomer) which is in accordance with the stability predicted by other similar adduct experiments. The molecular modelling experiments showed more pronounced restricted rotation of butadiene residue in C¿-2 isomers due to steric interaction between butadiene residue at N-7 and O(6) atom of guanine than in C¿-1 isomer. The butadiene residue also leads to steric overcrowding at 3'-phosphate in C¿-2 isomer which probably restricts the access to the active site of T4 polynucleotide kinase.

Animals↗

Assay of different photoproducts after UVA, B and C irradiation of DNA and human skin explants.

A 32P-HPLC method was applied to study the induction of UVB- and UVC-induced DNA lesions (cyclobutane dimers, 6-4 photoproducts and Dewar isomers) in human skin explants. The employed technique was sensitive enough to detect the lesions at a dose of 10 J/m2 UVB. Comparison of photoadduct formation under UVC and UVB indicated the importance of photosensitization pathways in DNA damage. Dewar isomers were detected only at a high dose of UVB. The compounds were identified by their photochemical reactivity and by spiking with prepared standards. Treatment with nuclease P1 was used to identify the 5'-terminal nucleotide. UVA caused no detectable adducts.

Adenosine Triphosphate↗

Risk of nervous system cancer among workers exposed to lead.

Experimental animal studies suggest that lead compounds may increase the risk of gliomas. To study whether occupational exposure to lead increases the risk, we followed nervous system cancer incidence among 20,741 employees biologically monitored for their blood lead (B-Pb) concentrations. We also performed a nested case-referent study, comprising 26 male cases of nervous system cancer (16 of which had gliomas). Those cases a B-Pb > or = 1.4 mumol/L had a twofold increase in the odds ratio of nervous system cancer as compared with those employees whose B-Pb had not exceeded 0.7 mumol/L. The excess was confined to gliomas (odds ratio 11, 95% confidence interval 1.0 to 630 for B-Pb > or = 1.4 mumol/L; overall P value for trend, 0.037). We obtained lifetime information on exposure and potential confounders for 58% of the cases. The odds ratio of glioma was associated with indices of lifetime exposure to lead, and potential confounders seemed not to explain the effects. The results suggest that there may be an association between occupational lead exposure and the risk of gliomas. No firm conclusions can be drawn because of the small number of cases and loss of material.

Adult↗

Communication Concerning the Risks of Occupational Exposures in Pregnancy.

The health professional who is involved in communicating information about reproductive risks from occupational hazards needs to consider several important aspects. Uncertainties in risk assessment, timing of exposure in relation to pregnancy, and the consequences of different preventive measures for the woman (family), as well as for the employer and other persons at the workplace are examples of such aspects. The basis for the pregnant woman's perception of risk must be recognized. The risk-communication goal is that the persons concerned fully understand the risk and its possible consequences, so that they will be able to make informed decisions about how to act. More attention should be given to risk communication in the training of health professionals.

Journal Article↗

Future research directions in the use of biomarkers.

Many DNA adduct studies have been carried out in occupational groups that have been at a risk of cancer based on epidemiological results relating to exposure decades ago. Even new epidemiological publications on cancer cannot accurately address the effective exposures after about 1970. This is one justification for biomarker studies. Another justification is exposures for which epidemiological studies have not been conducted or have provided inadequate results, in spite of suspicions raised by short-term or animal experiments. The modulation of environment carcinogenesis by host polymorphism in genes for xenobiotic metabolizing and DNA repair enzymes is currently under extensive investigation. The studies relating phenotype/genotype to cancer are presently extended to various end points that may be related to cancer such as DNA adducts and cytogenetic damage. Adjustment for a metabolic phenotype or genotype may also increase the precision in the measurement. Mutations in oncogenes and tumor suppressor genes may give clues to the etiology of cancer.

Alkenes↗