Postmenopausal circulating levels of 2- and 16α-hydroxyestrone and risk of endometrial cancer.

BACKGROUND: It has been suggested that the relative importance of oestrogen-metabolising pathways may affect the risk of oestrogen-dependent tumours including endometrial cancer. One hypothesis is that the 2-hydroxy pathway is protective, whereas the 16α-hydroxy pathway is harmful. METHODS: We conducted a case-control study nested within three prospective cohorts to assess whether the circulating 2-hydroxyestrone : 16α-hydroxyestrone (2-OHE1 : 16α-OHE1) ratio is inversely associated with endometrial cancer risk in postmenopausal women. A total of 179 cases and 336 controls, matching cases on cohort, age and date of blood donation, were included. Levels of 2-OHE1 and 16α-OHE1 were measured using a monoclonal antibody-based enzyme assay. RESULTS: Endometrial cancer risk increased with increasing levels of both metabolites, with odds ratios in the top tertiles of 2.4 (95% CI=1.3, 4.6; P(trend)=0.007) for 2-OHE1 and 1.9 (95% CI=1.1, 3.5; P(trend)=0.03) for 16α-OHE1 in analyses adjusting for endometrial cancer risk factors. These associations were attenuated and no longer statistically significant after further adjustment for oestrone or oestradiol levels. No significant association was observed for the 2-OHE1 : 16α-OHE1 ratio. CONCLUSION: Our results do not support the hypothesis that greater metabolism of oestrogen via the 2-OH pathway, relative to the 16α-OH pathway, protects against endometrial cancer.

Circulating sex hormones and breast cancer risk factors in postmenopausal women: reanalysis of 13 studies.

BACKGROUND: Breast cancer risk for postmenopausal women is positively associated with circulating concentrations of oestrogens and androgens, but the determinants of these hormones are not well understood. METHODS: Cross-sectional analyses of breast cancer risk factors and circulating hormone concentrations in more than 6000 postmenopausal women controls in 13 prospective studies. RESULTS: Concentrations of all hormones were lower in older than younger women, with the largest difference for dehydroepiandrosterone sulphate (DHEAS), whereas sex hormone-binding globulin (SHBG) was higher in the older women. Androgens were lower in women with bilateral ovariectomy than in naturally postmenopausal women, with the largest difference for free testosterone. All hormones were higher in obese than lean women, with the largest difference for free oestradiol, whereas SHBG was lower in obese women. Smokers of 15+ cigarettes per day had higher levels of all hormones than non-smokers, with the largest difference for testosterone. Drinkers of 20+ g alcohol per day had higher levels of all hormones, but lower SHBG, than non-drinkers, with the largest difference for DHEAS. Hormone concentrations were not strongly related to age at menarche, parity, age at first full-term pregnancy or family history of breast cancer. CONCLUSION: Sex hormone concentrations were strongly associated with several established or suspected risk factors for breast cancer, and may mediate the effects of these factors on breast cancer risk.

Calorie-providing nutrients and risk of breast cancer.

A case-control study was conducted in Italy to investigate the role of diet in breast cancer. Cases were 250 women with breast cancer, and controls were a stratified random sample of 499 women from the general population. A dietary history questionnaire was used to measure the intake of total fat, saturated fat, animal proteins, and other macronutrients. In multivariate analyses, the relative risks of breast cancer for women in the highest quintile of consumption of saturated fat and animal proteins were 3.0 (95% confidence interval, 1.9-4.7) and 2.9 (1.8-4.6), respectively. A reduced risk was found for women who derived less than 28% of calories from fat versus greater than 36%. A similarly reduced risk was found for women who derived less than 9.6% of calories from saturated fat or less than 5.9% from animal proteins. These data suggest that during adult life, a reduction in dietary intake of fat and proteins of animal origin may contribute to a substantial reduction in the incidence of breast cancer in population subgroups with high intake of animal products.

Blood levels of organochlorine residues and risk of breast cancer.

BACKGROUND: Organochlorines such as DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane] and PCBs (polychlorinated biphenyls), which have been used extensively as insecticides and as fluid insulators of electrical components, respectively, are known to be persistent environmental contaminants and animal carcinogens. These agents have been found in human tissue due to their inefficient metabolism and their solubility in lipids, which lead to lifelong sequestration in adipose tissue. Their association with human cancer occurrence, however, has been explored only marginally, with most studies having 20 or fewer cases. PURPOSE: This blinded study was designed to determine whether exposure to PCBs and to DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene], the major metabolite of DDT, is associated with breast cancer risk in women. METHODS: We analyzed sera from the stored blood specimens of 14,290 participants enrolled between 1985 and 1991 in the New York University Women's Health Study, a prospective cohort study of hormones, diet, and cancer. Cohort members who developed breast cancer were included as case patients in our nested case-control study. DDE and PCBs were measured by gas chromatography in the sera of 58 women with a diagnosis of breast cancer 1-6 months after they entered the cohort and in 171 matched control subjects from the same study population who did not develop cancer. RESULTS: Mean levels of DDE and PCBs were higher for breast cancer case patients than for control subjects, but paired differences were statistically significant only for DDE (P = .031). After adjustment for first-degree family history of breast cancer, lifetime lactation, and age at first full-term pregnancy, conditional logistic regression analysis showed a fourfold increase in relative risk of breast cancer for an elevation of serum DDE concentrations from 2.0 ng/mL (10th percentile) to 19.1 ng/mL (90th percentile). For PCBs, the relative risk for a change in serum levels from 3.9 ng/mL (10th percentile) to 10.6 ng/mL (90th percentile) was less than twofold, a nonsignificant association that was further reduced after adjustment for DDE. CONCLUSION: In this population of New York City women, breast cancer was strongly associated with DDE in serum but not with PCBs. IMPLICATIONS: These findings suggest that environmental chemical contamination with organochlorine residues may be an important etiologic factor in breast cancer. Given the widespread dissemination of organochlorine insecticides in the environment and the food chain, the implications are far-reaching for public health intervention worldwide.

Serum C-peptide, insulin-like growth factor (IGF)-I, IGF-binding proteins, and colorectal cancer risk in women.

BACKGROUND: Leading a Western lifestyle, being overweight, and being sedentary are associated with an increased risk of colorectal cancer. Recent theories propose that the effects of these risk factors may be mediated by increases in circulating insulin levels and in the bioactivity of insulin-like growth factor (IGF)-I. To test this hypothesis, we conducted a case-control study nested within a cohort of 14 275 women in New York. METHODS: We used blood samples that had been obtained from these women from March 1985 through June 1991 and stored in a biorepository. C-peptide (a marker for insulin secretion), IGF-I, and IGF-binding proteins (IGFBPs)-1, -2, and -3 were assayed in the serum of 102 women who subsequently developed colorectal cancer and 200 matched control subjects. Logistic regression was used to relate cancer risk to these peptide levels, by adjustment for other risk factors. All statistical tests used are two-sided. RESULTS: Colorectal cancer risk increased with increasing levels of C-peptide (P:(trend) =.001), up to an odds ratio (OR) of 2. 92 (95% confidence interval [CI] = 1.26-6.75) for the highest versus the lowest quintiles, after adjustment for smoking. For colon cancer alone (75 case subjects and 146 control subjects), ORs increased up to 3.96 (95% CI = 1.49-10.50; P:(trend) <.001) for the highest versus the lowest quintiles. A statistically significant decrease in colorectal cancer risk was observed for increasing levels of IGFBP-1 (P:(trend) =.02; OR in the upper quintile = 0.48 [95% CI = 0.23-1. 00]), as well as for the highest quintile of IGFBP-2 levels (P:(trend) =.06; OR = 0.38 [95% CI = 0.15-0.94]). Colorectal cancer risk showed a modest but statistically nonsignificant positive association with levels of IGF-I and was statistically significantly increased for the highest quintile of IGFBP-3 (OR = 2.46 [95% CI = 1. 09-5.57]). CONCLUSIONS: Chronically high levels of circulating insulin and IGFs associated with a Western lifestyle may increase colorectal cancer risk, possibly by decreasing IGFBP-1 and increasing the bioactivity of IGF-I.

A prospective study of endogenous estrogens and breast cancer in postmenopausal women.

BACKGROUND: Circumstantial evidence links endogenous estrogens to increased risk of breast cancer in women, but direct epidemiologic support is limited. In particular, only a few small prospective studies have addressed this issue. PURPOSE: Our purpose was to assess breast cancer risk in relation to circulating levels of the two major endogenous estrogens, estrone and estradiol, measured before the clinical onset of the disease. METHODS: The association between serum levels of estrogens and the risk of breast cancer was examined in a prospective cohort study of 14,291 New York City women, 35-65 years of age, who received screening for breast cancer at the time of blood sampling and who had not been diagnosed with breast cancer. During the first 5 1/2 years of study, we identified 130 breast cancers among the postmenopausal group (7063 women, 35,509 person-years). The case subjects and twice as many postmenopausal control subjects were included in a case-control study nested within the cohort. Biochemical analyses for percent free estradiol, percent estradiol bound to sex hormone-binding globulin (SHBG), total estradiol, estrone, and follicle-stimulating hormone were performed on sera that had been kept at -80 degrees C since sampling. RESULTS: For increasing quartiles of total estradiol, the odds ratio (ORs) of breast cancer, as adjusted for Quetelet index (weight in kilograms divided by the square of the height in meters), were 1.0, 0.9, 1.8, and 1.8 (P value for trend = .06); the ORs for increasing quartiles of estrone were 1.0, 2.2, 3.7, and 2.5 (P value for trend = .06). For increasing quartiles of free estradiol, defined as the fraction of estradiol that is not bound to proteins, the Quetelet index-adjusted ORs of breast cancer were 1.0, 1.4, 3.0, and 2.9 (P value for trend < .01). When we considered the percent of estradiol bound to SHBG, the Quetelet index-adjusted ORs were 1.0, 0.70, 0.40, and 0.32 (P value for trend < .01), thus suggesting a strong protective effect. These associations persisted or became even stronger when analyses were restricted to women whose samples had been drawn 2 or more years before breast cancer diagnosis. CONCLUSIONS: These data represent the first confirmation in a large prospective epidemiologic study of a link between circulating estrogens and breast cancer risk. Although estrogen levels appeared to fall within the conventional limits of normality in all women under study, those who subsequently developed breast cancer tended to show higher levels of estrone, total estradiol, and free estradiol, and a lower percent of estradiol bound to SHBG than women who remained free of cancer. IMPLICATIONS: Factors that increase endogenous estrogen production or reduce the binding of estradiol to SHBG may increase a woman's risk of developing breast cancer later in life.

DNA-protein cross-links in welders: molecular implications.

A new method for detecting DNA-protein cross-links involving selective precipitation of DNA containing cross-linked proteins by K(+)-sodium dodecyl sulfate was utilized in the peripheral WBC of 21 male metal arc welders and in 26 male controls of similar age and racial characteristics who were not exposed to welding fumes. DNA was quantitated by Hoechst fluorescence. Although the concentration of nickel and chromium in the peripheral blood did not differ between subjects in the two groups, one-fourth of the welders had levels of DNA-protein cross-links that were above the upper limit of the controls. Mean cross-link values were 1.85 +/- 1.14% (SD) among the welders and 1.17 +/- 0.46% among the controls, a 58% statistically significant difference (P = 0.01). Thus, many welders appeared to be burdened with an excess of DNA-protein cross-links, suggesting exposure to cross-linking agents and, possibly, a detectable biological effect of potential genotoxic consequences.

Breast cancer and alcohol consumption: a case-control study in northern Italy.

From 1983 to 1986, a population-based case-control study of alcohol and breast cancer (250 cases and 499 controls) was conducted in a grape-farming area of northern Italy, where wine consumption is widespread. In the study population, 30% of women were abstainers and 15% reported alcohol intakes of 30 g/day or more. After adjustment for potential confounders, no appreciable association was evident for alcohol consumptions as high as 40 g/day. Women reporting intakes of more than 40 g/day showed approximately a 2-fold increase in the risk of breast cancer (relative risk, 1.9; 95% confidence interval, 1.1-3.3). A 2-fold increase in risk was observed for consumptions of more than 40 g/day of alcohol from wine, the most common alcoholic beverage in this population. These findings suggest that an association between alcohol intake and breast cancer may exist. However, the moderate risk observed seems to be limited to the relatively small group of women consuming daily amounts of alcohol in excess of 40 g, the equivalent of about half a bottle of wine or more.

A CYP1A1 restriction fragment length polymorphism is associated with breast cancer in African-American women.

We examined the role of CYP1A1 polymorphisms as potential molecular markers of breast cancer susceptibility in Caucasian and African-American women. The case-control study involved 51 women with breast cancer and 269 female controls. In African-Americans, the frequency of the homozygous MspI polymorphism was 3.5% in controls and 19% in breast cancer cases. The odds ratio of breast cancer with the MspI homozygous variant was 9.7 (95% confidence interval: 2.0-47.9). This association was not observed in Caucasian women. The exon 7 and AA polymorphisms were not associated with breast cancer in either group. The mechanism for the observed association between the MspI polymorphism and breast cancer is unclear. It is possible that the CYP1A1 MspI RFLP is linked with other polymorphisms in the African-American population, either in the CYP1A1 gene, which is involved in estrogen metabolism, or other genes related to risk of breast cancer.

Increased androgenic activity and breast cancer risk in premenopausal women.

Blood and urine specimens from 27 premenopausal breast cancer patients and 62 healthy controls have been compared with respect to concentration of testosterone and progesterone in blood and of testosterone and androstanediol in urine, measured in the luteal phase of the menstrual cycle. There was a strong positive association between the concentration of the two androgens, either in blood or urine, and breast cancer risk. A strong association was also observed with decreasing levels of progesterone. The association was statistically significant (p for trend less than 0.01) for each hormone; the rate ratios were 10.2 for serum testosterone (highest category), 5.6 for serum progesterone (lowest category), 8.4 for urinary testosterone (highest category), and 5.2 for androstanediol (highest category). The rate ratio for women presenting both high serum testosterone and low progesterone was 21.8 (4.1 to 116.1). Considering the exposure to at least one of three androgens at the highest level and low progesterone, the rate ratio was as high as 90.2 (8.2 to 989.7). This study provides evidence for the hypothesis that increased androgenic activity is an important risk indicator for breast cancer, particularly when associated with anovulation, as indicated by low serum progesterone level.

A specific African-American CYP1A1 polymorphism is associated with adenocarcinoma of the lung.

A case-control study on lung cancer in African-Americans has been conducted to assess whether a novel African-American-specific polymorphism in the CYP1A1 gene increases the susceptibility to tobacco-related lung cancer. The prevalence of the AA RFLP was 17.1% in the DNA extracted from archived tissue blocks from 76 incident cases of lung cancer, and was 16.3% in peripheral blood lymphocyte DNA of 123 healthy African-American volunteers recruited from a community in the eastern United States. The analysis by histological type showed an association between adenocarcinoma (AC) of the lung and the AA RFLP (odds ratio, 2.6; 95% confidence interval, 1.1-6.3). One homozygous variant subject was present among the AC cases. The risk of AC in subjects who both smoke and carry the AA RFLP was more than double, in comparison to subjects who only smoke (relative interaction magnitude under the additive model, 24%). The mean value of pack-year in AC with the polymorphism was 5.0 +/- 2.5 and in AC without the polymorphism was 37.2 +/- 6.5 (P < 0.05). Our data suggest that a selective association exists between the AA polymorphism and adenocarcinoma of the lung and that a lower dose of tobacco is sufficient to exert carcinogenic effects on the adenomatous tissue of subjects carrying the AA polymorphism.

Serum and urinary androgens and risk of breast cancer in postmenopausal women.

Serum levels of testosterone, dihydrotestosterone, androstenedione, dehydroepiandrosterone sulfate, and sex hormone-binding globulin and urinary levels of testosterone and androstanediol were compared in 75 women with breast carcinoma and 150 age-matched healthy controls. Odds ratios for quartiles of hormones, adjusted for known potential confounders, were computed using conditional logistic regression. Risk of breast cancer was positively associated with levels of all androgens in serum and urine but appeared stronger for testosterone (for trend, P = 0.03) and dehydroepiandrosterone sulfate (for trend, P = 0.06) in serum and for testosterone (for trend, P = 0.001) and androstanediol (for trend, P = 0.04) in urine. The adjusted odd ratios for high versus low quartiles were 2.7 (95% confidence interval, 1.1-6.5) for serum testosterone, 2.8 (1.1-7.4) for dehydroepiandrosterone sulfate, 4.7 (1.8-12.1) for urinary testosterone, and 3.4 (1.4-8.7) for urinary androstanediol. These observations suggest that endogenous androgenic hormones may play an important role in the epidemiology of postmenopausal breast cancer in women.

Androgens and breast cancer in premenopausal women.

We investigated the role of androgens in premenopausal breast cancer by comparing serum testosterone, dihydrotestosterone, androstenedione, dehydroepiandrosterone sulfate, progesterone, sex-hormone-binding globulin-binding capacity, and urinary testosterone and androstanediol in 63 women with breast adenocarcinoma and 70 healthy controls of similar age. With variables dichotomized at the 75th percentile, the age-adjusted relative risk was 3.4 (95% confidence interval, 1.6-7.3) for high versus low levels of serum testosterone, 2.1 (0.9-4.8) for urinary testosterone, and 2.5 (1.1-5.9) for serum dihydrotestosterone. We observed no differences in other hormones. The strength of the associations changed markedly with increasing time to the onset of the next menses. The risk for testosterone and dihydrotestosterone, which was negligible in women with onset within 5 days of sampling, increased progressively to nearly 10-fold higher than in unstratified data in women with onset 10 days or more after sampling. This study provides arguments in favor of a role for increased androgenic activity in premenopausal breast cancer. It also suggests that unknown factors related to cycle length may be important in modulating the strength of the association with testosterone. The results are discussed also in reference to possible biases and inadequacies in study design.

Genetic variant of luteinizing hormone and risk of breast cancer in older women.

A genetic variant of luteinizing hormone (LH) characterized by two point mutations in codons 8 (TGG-->CGG) and 15 (ATC-->ACC) of the LH beta-subunit gene has been described recently. As compared with wild-type LH, the variant LH appears to have higher in vitro bioactivity but a shortened circulatory half-life, and it has been reported to affect circulating levels of sex hormones. Our purpose was to determine whether the variant form of LH is associated with an altered risk of breast cancer. This hypothesis was addressed in a case-control study nested within a prospective cohort that included 270 cases of breast cancer and twice as many matching control subjects. The study was limited to subjects diagnosed at age 50 years or older. The LH status was determined by the combination of two immunofluorometric assays of serum using monoclonal antibodies. Frequency of the variant LH was similar in breast cancer cases and controls (11.5% versus 10.7%). In conditional regression models, the presence of the variant LH was not associated with a considerable increase of breast cancer risk (odds ratio, 1.07; 95% confidence interval, 0.68-1.69). Adjustment for potential confounders did not notably change the risk estimate (odds ratio, 1.11; 95% confidence interval, 0.69-1.78). These observations do not appear to support the hypothesis that this particular variant of LH is associated with altered risk of breast cancer diagnosed at age 50 years and older.

Risk of breast cancer and organochlorine exposure.

A prospective investigation of breast cancer and organochlorine (OC) exposures was undertaken in the New York University Women's Health Study. Cases (n = 148) and individually matched controls (n = 295) were identified among women whose blood had been obtained 6 months or more prior to breast cancer diagnosis. In addition, among 84 cases and 196 controls, two or more consecutive annual blood samples were available to estimate half-lives of 1,1-dichloro-2,2-bis(p-chlorophenyl) ethene (DDE) and polychlorinated biphenyls (PCBs). Cases and controls had similar levels of DDE (geometric mean, 6.95 versus 7.27 ng/ml; lipid-adjusted geometric mean, 977 versus 1100 ng/g) and PCBs (5.04 versus 4.97 ng/ml; lipid-adjusted geometric mean, 683 versus 663 ng/g). These differences remained nonsignificant when estrogen receptor status of tumors was considered. DDE and PCB half-lives did not differ in case versus control patients. In control patients, DDE and PCB half-lives were strongly correlated (r(s) = 0.71), and the half-life of DDE (but not that of PCB) was inversely correlated with body mass index (BMI), yet the blood serum levels of PCB (but not those of DDE) were correlated with BMI. We conclude that there is no evidence for an association of breast cancer risk with DDE or PCB levels in blood (based on samples collected during the period 1987-1992) nor with their elimination half-lives. However, changes in DDE and PCBs over time are influenced by metabolism, BMI, and current OC exposures, and each may affect interpretation of OC levels in risk assessment models.

Temperature variations in upright mechanical freezers.

We examined temperature deviations from the set temperature in specific locations, between-freezer temperature variability, and the effect of defrosting on temperature deviation in a group of 15 upright mechanical freezers, part of a biological sample bank of a large prospective cohort study. By using an Omega Type T Thermocouple Microcomputer thermometer with the freezers set at -80 degrees C, the internal temperature (12 locations in each freezer) ranged from -90 degrees C to -43.5 degrees C. Overall, internal temperatures tended to be appreciably warmer in the upper and front sections of the freezers. Upright front-loading mechanical freezers, which are widely used in research laboratories throughout the world, may not be optimally suited to preserve human biological samples for long-term banking in epidemiology.

Reliability of serum measurements of lignans and isoflavonoid phytoestrogens over a two-year period.

We examined the distribution and long-term reliability of serum measurements of the two main human lignans, enterolactone and enterodiol, and the isoflavonoid phytoestrogens daidzein, genistein, equol, and O-Desmethylangolensin in the New York University Women's Health Study, a prospective cohort study of sex hormones and breast cancer. Serum samples collected at three yearly visits in 30 premenopausal and 30 postmenopausal women who had not been diagnosed with cancer or cardiovascular disease were included in the study. Assays were carried out by ion-exchange chromatography and capillary gas chromatography-mass spectrometry. Levels of isoflavonoid phytoestrogens were low, often at or below the sensitivity level of the assay. The reliability coefficients for these compounds were also low (< or =0.30). The median levels of enterodiol and enterolactone were 1.52 nmol/liter and 20.2 nmol/liter, respectively, and were comparable with the levels observed in omnivorous Finnish women living in the Helsinki area. A substantial number of women, though, had fairly high levels: for instance, 15% of the assays showed levels of enterolactone greater than the mean level observed in vegetarian Finnish women, i.e., 89.1 nmol/liter (H. Adlercreutz et al., Cancer Detec. Prev., 18: 259-271, 1994). The reliability coefficient of a single measurement of enterolactone was moderately high (0.55), suggesting that serum measurements of this compound could be a useful tool in prospective epidemiological studies with access to repeated blood or serum specimens. For instance, the reliability coefficient of the average of three measurements of enterolactone would be 0.79, a level considered acceptable in light of the other sources of error that are present in epidemiological studies (W. Willett, Stat. Med., 8: 1031-1040, 1989).

Racial differences in restriction fragment length polymorphisms and messenger RNA inducibility of the human CYP1A1 gene.

Recent studies have examined the relationship between genetic polymorphisms of the human cytochrome P-4501A1 (CYP1A1) gene and lung cancer susceptibility. We have quantified genotypic frequencies and measured gene expression in the CYP1A1 gene within racially diverse groups in order to determine the relationship between genotype and transcriptional regulation of the CYP1A1 gene. Lymphocytes were obtained from 68 individuals of European-American, African-American, and Asian descent, and CYP1A1 gene inducibility was measured in mitogen-stimulated cells. CYP1A1 gene inducibility was significantly lower in African-Americans than in European-Americans or Asians, while several other population parameters were found to have no effect on gene expression levels. Restriction fragment length polymorphism analysis of lymphocyte DNA following MspI restriction enzyme digestion revealed a significant difference in the frequencies of CYP1A1 genotypes between European-Americans and Asians. The only homozygous variants detected were of Asian descent. The frequencies of CYP1A1 genotypes in all races conformed to Hardy-Weinberg genotypic equilibrium. When CYP1A1 gene inducibility was compared to CYP1A1 genotype, no significant correlations were found. These studies, along with our previous survey of CYP1A1 gene expression in creosote-exposed workers, add further support to the use of CYP1A1 gene inducibility as a potential marker of polycyclic aromatic hydrocarbon exposure in human populations.

Expression of the CYP1A1 gene in peripheral lymphocytes as a marker of exposure to creosote in railroad workers.

We have conducted a pilot study to assess levels of cytochrome CYP1A1 gene expression in human peripheral lymphocytes as a molecular biomarker assay for polycyclic hydrocarbon exposure. Basal and 3-methylcholanthrene-induced levels of gene expression were measured by standard slot-blot mRNA analyses in mitogen-stimulated cultures of peripheral blood lymphocytes from creosote-exposed railroad workers and unexposed control subjects. Dermal and inhalation exposure of workers to creosote may vary substantially as a function of working conditions related to temperature. Therefore, blood specimens were collected from separate groups during the winter, fall, and summer. Basal and induced CYP1A1 gene expression levels were not elevated in workers from any of the three seasonal studies. However, induced/basal (inducibility) CYP1A1 mRNA ratios from workers sampled in the summer (when actual exposures were greatest) were significantly higher when compared to those of controls (P < 0.01). These studies demonstrate the potential usefulness of specific gene expression assays in human peripheral lymphocytes for the assessment of carcinogen exposure in human populations.

Human metallothionein gene expression determined by quantitative reverse transcription-polymerase chain reaction as a biomarker of cadmium exposure.

Expression of the metallothionein (MT) gene in frozen human lymphocytes has been developed as a new molecular biomarker of heavy metal exposure. Workers at a Polish battery factory with high exposure to cadmium were monitored for airborne exposure and blood cadmium levels. A novel quantitative reverse transcription-PCR (RT-PCR) technique, making use of a homologous internal standard, was used to assess the level of MT-specific mRNA in frozen stored aliquots of blood samples taken from exposed and control workers. Results from this assay showed a statistically significant 2.5-fold increase in MT mRNA in exposed compared to control workers. The RT-PCR results also showed significant correlation with airborne cadmium, as registered on personal monitors and with blood cadmium levels. The results suggest that gene induction measured by quantitative RT-PCR is a promising approach for application as a biomarker of biologically effective dose in small samples of frozen tissues or cells.