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Biomedical subjects

D W Sepkovic

Publications and source records attributed to D W Sepkovic.

At least 19 recordsLinked to original sources
PubMed1998

Do urinary oestrogen metabolites predict breast cancer? Guernsey III cohort follow-up.

This is the first prospective study of urinary measures of the two major competing pathways of oestrogen metabolism, 16alpha-hydroxyoestrone (16alpha-OHE1) and 2-hydroxyoestrone (2-OHE1), in relation to incident breast cancer risk. Experimental and case-control study results suggest that metabolism favouring the more oestrogenic 16alpha-OHE1 pathway may be linked to higher breast cancer risk. Women aged 35 and older from Guernsey (n = 5104) were surveyed in 1977-85 and have been continuously monitored for breast cancer and mortality up to the present (Guernsey III, Imperial Cancer Research Fund). Incident cases of breast cancer were matched to three control subjects for comparison of urinary oestrogen metabolite levels measured by enzyme immunoassay (EIA) in spot urine samples collected at baseline and stored frozen for up to 19 years. Consistent with case-control study results, post-menopausal (but not premenopausal) women at baseline who went on to develop breast cancer showed about a 15% lower 2:16alpha-OHE1 ratio than matched control subjects. Further, subjects with metabolite ratios in the highest tertile of 2:16alpha-OHE1 had about a 30% lower risk than women with ratios in the lowest two-thirds, although results were not statistically significant (OR = 0.71, 95% CI = 0.29-1.75). It is of potential importance that, in contrast to most risk factors for breast cancer, such as late age at first birth, oestrogen metabolism appears to be modifiable via diet and exercise, offering women the possibility of lowering breast cancer risk through non-pharmacological measures, although this remains to be tested.

Adult↗
PubMed1998

Estrogen metabolism and the malignant potential of human papillomavirus immortalized keratinocytes.

Increased 16alpha-hydroxylation of estradiol has been shown to be associated with heightened cancer risk in estrogen responsive tissue. Certain types of human papillomavirus (HPV) are cofactors for cancer in the cervix, an estrogen sensitive tissue. We have demonstrated that estradiol and 16alpha-hydroxyestrone increased the number of cells positive for proliferating cell nuclear antigen in HPV immortalized keratinocytes, the in vitro correlate of the premalignant keratinocyte. These estrogens caused the abnormal proliferation and anchorage independent growth, which correlates with malignant conversion. Indole-3-carbinol, a phytochemical in cruciferous vegetables known to preferentially induce 2-hydroxylation with minimal effect on 16alpha-hydroxylation, markedly blocked the ability of estradiol to increase anchorage independent growth. The results indicate that 16alpha-hydroxyestrone increases the malignant phenotype of HPV immortalized keratinocytes. However, indole-3-carbinol will block this response.

Aryl Hydrocarbon Hydroxylases↗
PubMed1997

Role of the estrogen receptor in the action of organochlorine pesticides on estrogen metabolism in human breast cancer cell lines.

As interest in the properties of xenoestrogenic compounds has grown, different in vitro cell culture systems have been proposed as models, against which to gauge relative estrogenic impact. Previous research indicated that some organochlorine-based pesticides elevated the production of 16 alpha-hydroxyestrone relative to 2-hydroxyestrone in ER+ MCF-7 breast cancer cells while phytochemicals like indole-3-carbinol reduced this ratio. That this ratio may be a biological marker of the risk of breast cancer has recently been demonstrated. In this study we have carried out the same paradigm in two ER- cell lines to examine the effect of receptor status. To determine whether the impact of chlorinated pesticides can be modulated by phytochemicals, the ability of indole-3-carbinol or brassinin to reverse the changes in metabolism was examined. Non-persisting phosphorus-based pesticides were also studied and shown not to have an effect on estrogen metabolism. The implications of these findings are examined.

Anticarcinogenic Agents↗
PubMed1996

Urinary markers of estrogen metabolism 2- and 16 alpha-hydroxylation in premenopausal women.

There is considerable scientific interest in whether measurement of the major estrogen metabolites 2- and 16 alpha-hydroxyestrone will shed light on the role of estrogen in the risk of breast cancer. These have been difficult to measure in large numbers because of the need for radiolabeled tracers, but a new assay is able to utilize spot urine samples. The main objective of this study was to assess the reliability of a newly developed enzyme immunoassay (EIA) for the measurement of 2- and 16 alpha-hydroxyestrone in urine samples collected from a large group of healthy premenopausal women enrolled in a clinical trial A secondary objective was to assess the impact of several factors such as body weight on the urinary estrogen metabolite ratios. The study cohort included 174 women aged 44-50, who were enrolled in the Cardiovascular Risk Factors and Menopause Trial, also referred to as the Women's Healthy Lifestyle Project (WHLP), an ongoing 5-year clinical trial of 535 premenopausal women randomized either to an intensive dietary life-style intervention group or to an assessment-only control group. Measurements of 2- and 16 alpha-hydroxyestrone showed a high intraclass correlation for blind duplicate urine samples (R = 0.94 and R = 0.80), cross-sectionally and over time (R = 0.79 and R = 0.62), in this population of healthy premenopausal women. The intervention diet (of 25% of total calories from fat) did not appear to influence the estrogen metabolite ratio. This new estrogen metabolite EIA demonstrates good reliability and thus may be appropriate for use in large epidemiologic studies of estrogen-related diseases. There was no relation between dietary fat reduction, weight loss, and increased exercise and change in the ratio among premenopausal women in this study.

Adult↗
PubMed1996

2-hydroxyestrone: the 'good' estrogen.

The issue of the role of 2-hydroxyestrone (2-OHE1) in breast cancer has been the subject of considerable controversy as to whether it is carcinogenic or anticarcinogenic. The expanding data base outlined below is most consistent with the conclusion that 2-OHE1 is anticarcinogenic. In every experimental model in which 2-hydroxylation was increased, protection against tumors was achieved. Correspondingly, when 2-hydroxylation was decreased, an increase in cancer risk was observed. Even more dramatically, in the case of laryngeal papillomas induction of 2-hydroxylation with indole-3-carbinol (I3C) has resulted in inhibition of tumor growth during the time that the patients continue to take 13C or vegetables rich in this compound.

Anticarcinogenic Agents↗
PubMed1995

Indole-3-carbinol. A novel approach to breast cancer prevention.

The results show that all of the carcinogens, oncogenes, and tumor-associated viruses that we have studied profoundly affect the extent of 2- and 16 alpha-hydroxylation in a prorisk direction. All of the dietary and biological responses associated with increased cancer risk decrease 2-hydroxylation and increase 16 alpha-hydroxylation. Remarkably, although PAHs are reported to induce P450-1A1, we have found them to decrease 2-hydroxylation. Finally, using indole-3-carbinol to induce 2-hydroxylation results in the chemoprevention of mammary tumors in rodents and recurrences of laryngeal papillomas in humans. Also correlating with these studies in HPV is the decrease in the C-2/C-16 alpha metabolite ratio observed in women with CIN relative to control subjects. The greatest decrease was observed in women with the most severe form, CIN3 (Figure 23). These findings are under further investigation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1994

Monoclonal antibody-based enzyme immunoassay for simultaneous quantitation of 2- and 16 alpha-hydroxyestrone in urine.

Alterations in the metabolism of estrogen have been implicated as an important factor in the etiology of diseases such as gynecological cancers and lupus erythematosus. The major metabolites of estradiol are hydroxylated at the C-2 or C-16 alpha position yielding products with estrogen antagonist and agonist activities, respectively. A sensitive and specific immunodiagnostic assay to determine the balance between these competing pathways might serve as a routine biomarker for management of estrogen-related diseases. We describe here the generation of high affinity, specific murine monoclonal antibodies to 2-hydroxyesterone and 16 alpha-hydroxyestrone by high efficiency fusion protocols. With these antibodies, we have developed a rapid and simple enzyme immunoassay (EIA) kit for the simultaneous quantitation of 2- and 16 alpha-hydroxyestrone in unextracted urine. Initial validation studies established that urinary metabolite 2- and 16 alpha-hydroxyestrone concentrations found by the EIA correlate well with values found by gas chromatography-mass spectroscopy. Preliminary studies with the EIA kit found total recovery of metabolites from spiked urine samples. The EIA inter- and intra-assay coefficients of variation for 2-hydroxyestrone and 16 alpha-hydroxyestrone and the ratio of 2-hydroxyesterone to 16 alpha-hydroxyestrone with the current EIA kit were consistently less than 9%. This kit, designated ESTRAMET 2/16 may provide an important new tool for research in estrogen-related diseases.

Antibodies, Monoclonal↗
PubMed1994

Catechol estrogen production in rat microsomes after treatment with indole-3-carbinol, ascorbigen, or beta-naphthaflavone: a comparison of stable isotope dilution gas chromatography-mass spectrometry and radiometric methods.

Compounds like indole-3-carbinol (I3C) have been shown to increase catechol estrogen formation and reduce mammary tumor incidence in mice. These compounds may exert a protective effect for breast cancer development by decreasing the overall estrogen pool available for the formation of 16 alpha-hydroxyestrone (16 alpha-OHE1), a metabolite that retains significant estrogenic activity, may be mutagenic and could represent a potential carcinogenic intermediate of estradiol degradation. I3C and ascorbigen originate from the breakdown of glucobrassicin. We have compared the inductive effects of I3C with ascorbigen and beta-naphthaflavone (Bnf) in microsomes from rats pretreated with these compounds using isotope dilution GC-MS and a radiometric method. Incubated microsomes from rats pretreated with I3C and ascorbigen yielded high levels of 2-hydroxyestradiol (2-OHE2) that were comparable to levels induced by Bnf and were significantly above control group levels (p < 0.005). Absolute values determined by the radiometric method were approximately 40% lower than 2-OHE2 concentrations determined by GC-MS, although the relative changes in each group were the same. These differences may be attributed to the radiolabel becoming trapped in microsomal intermediates in the sequence leading to tritium entering the aqueous compartment. Both ascorbigen- and Bnf-treated animals exhibited significant increases in 2-hydroxyestrone (2-OHE1) (p < 0.05). The ability of ascorbigen to induce estradiol C-2 hydroxylation has not been previously reported. Based on these data, we speculate that ascorbigen will act as an anticarcinogenic agent and will inhibit or reduce the incidence of mammary tumor formation.

Animals↗
PubMed1993

Effect of varying proportions of dietary menhaden and corn oil on experimental rat mammary tumor promotion.

Dose-related effects of long-chain highly unsaturated n-3 fatty acids on the development of N-nitrosomethylurea (NMU)-induced rat mammary tumors were assessed in female F344 rats. Four test groups (36 rats/group) were fed the following high-fat (HF) diets (23% fat, w/w): Group 1, 18% menhaden oil (MO) and 5% corn oil (CO); Group 2, 11% MO and 11.8% CO; Group 3, 5% MO and 18% CO; Group 4, CO alone. A fifth group, serving as an internal control, was fed a low-fat diet containing 5% CO alone. Experimental diets were begun after initiation with NMU, and the experiment was terminated 31 wk later. Total tumor numbers in the five groups were 28, 16, 32, 26 and 11, respectively, indicating that the promotion phase of NMU-induced carcinogenesis was significantly suppressed only when equal parts of CO and MO (Group 2) were fed or when CO alone was fed at 5% (w/w). At high (Group 1) or low (Group 3) levels of MO, tumor numbers were indistinguishable from the HF CO group (Group 4). The same pattern was observed when assessed in terms of cumulative tumor incidence and multiplicity. However, when expressed in terms of final tumor incidence, dietary MO did not suppress tumor promotion in a statistically significant fashion at any concentration. Animals fed MO gained weight at the same rate as those fed CO, indicating that the presence of MO in the diet did not result in food avoidance behavior. Measurement of total serum cholesterol indicated an inverse trend with respect to the MO content of the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1993

Influence of indole carbinols and growth hormone on the metabolism of 4-androstenedione by rat liver microsomes.

The effect of indole-3-carbinol (IC), an anticarcinogen present in cruciferous vegetables, to alter the metabolism of 4-androstenedione (AD) by female rat liver microsomes was investigated and compared to that of its main gastric conversion product, diindolylmethane (DIM) as well as other specific cytochrome P450 inducers. DIM was a more potent inducer of the hydroxylase which converts androsterone to its 6 beta-hydroxylated derivative 3 alpha, 6 beta-dihydroxy-5 alpha-androstan-17-one (A) than IC after either oral or intraperitoneal administration and was also a better in vitro inhibitor. Isosafrole (ISF), which like IC and DIM, induces CYP1A2 as well as gestodene, were powerful inhibitors of the in vitro reaction. Naringenin produced only a weak inhibitory effect while 3-methylcholanthrene was inactive. SKF-525A, a prototypic hydroxylase inhibitor, or 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androst-1-ene-3-one which inhibits steroid 5 alpha-reductase, also decreased the formation of A from AD by liver microsomes. The infusion of human growth hormone by osmotic minipump, which feminizes hepatic steroid metabolism, increased the ability of male rat liver microsomes to convert AD to A and to respond to induction by IC. The identity of A, the main polar derivative of AD, induced by IC, DIM and ISF, was tentatively assigned by a combination of GC-MS and results from metabolic studies with intermediates in the pathway leading to its formation. It is proposed that the protective role of indole carbinols against mammary carcinoma due to decreased formation of 16 alpha-hydroxyestrone from estrone may be further enhanced by the diminished availability of AD for aromatization to estrone.

Administration, Oral↗
PubMed1991

Approaches for assessing health risks from complex mixtures in indoor air: a panel overview.

Critical to a more definitive human health assessment of the potential health risks from exposure to complex mixtures in indoor air is the need for a more definitive clinical measure and etiology of the health effects of complex mixtures. This panel overview highlights six of the eight presentations of the conference panel discussion and features a number of the major topical areas of indoor air concern. W. G. Meggs assessed clinical research priorities with primary focus on the role of volatile organic chemicals in human health, recognizing the areas where definitive data are lacking. By recognizing many types of chemical sensitivity, it may be possible to design studies that can illuminate the mechanisms by which chemical exposure may cause disease. The critically important topic of multiple chemical sensitivity was discussed by N. A. Ashford, who identified four high risk groups and defined the demographics of these groups. P. A. Schulte addressed the issue of biological markers of susceptibility with specific considerations of both methodological and societal aspects that may be operative in the ability to detect innate or inborne differences between individuals and populations. Three case studies were reviewed. H. Anderson discussed the past and present priorities from a public health perspective, focusing on those issues dealing with exposures to environmental tobacco smoke and formaldehyde off-gassing from materials used in mobile home construction. J. J. Osborne described several case studies involving wood smoke exposure to children, with emphasis on the significantly greater occurrence of chronic respiratory symptoms and acute chest illness for children from homes heated with woodburning stoves.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollution, Indoor↗
PubMed1989

Biochemical validation of self-reported exposure to environmental tobacco smoke.

Biochemical validation of reported exposure to environmental tobacco smoke (ETS) lends credibility to epidemiological studies investigating the association of passive inhalation of smoke to respiratory disease or lung cancer. In the current study, a series of questions regarding ETS exposure was self-administered to nonsmokers and self-reported intensity of exposure was compared with cotinine levels in urine samples obtained on site. The target population of this study was a group of municipal workers who reported exposure in a domestic setting and/or in the workplace. When asked if they were exposed to ETS on social occasions, both males and females who responded positively had higher urinary cotinine levels (P less than 0.02) than those who gave a negative response. Mean urinary cotinine concentrations were found to be elevated in both men and women who reported that they lived with a smoker. Cotinine levels in the urine of those reporting exposure were over twice as high as those in the urine of respondents who denied having been exposed. ETS exposure in the home was the greatest contributor to increased urinary cotinine levels in both men and women. Among individuals who were exposed at work only, the reported degree of exposure agreed well with the mean urinary cotinine values. Those findings emphasize that the validation of exposure status with a biomarker is an essential prerequisite for epidemiological studies investigating passive smoking.

Adult↗
PubMed1989

Elimination of cotinine from body fluids: disposition in smokers and nonsmokers.

We have evaluated differences in the elimination of cotinine, a major nicotine metabolite, in smokers who quit smoking and never-smokers who were exposed to environmental tobacco smoke (ETS) under controlled conditions. The mean biological half-life of cotinine in urine, collected from the nine smokers was 16.5 +/- 1.2 h, in never-smokers exposed to ETS, 27.3 +/- 1.9 h. Differences in the mode of uptake and absorption of nicotine and possible differences in nicotine metabolism may play roles in the clearance rate differences between smokers and nonsmokers.

Adult↗