Anti-proliferative effects of Chinese herb Cornus officinalis in a cell culture model for estrogen receptor-positive clinical breast cancer

Selective estrogen receptor modulators and a combination of mechanistically distinct chemotherapeutic agents represent conventional therapeutic interventions for estrogen receptor-positive (ER+) clinical breast cancer. Long-term treatment with these agents is associated with acquired tumor resistance and other adverse side effects that impact on patient compliance. Herbal medicines are being widely used in complementary and alternative medicine. However, long-term safety and efficacy of the use of herbal medicines, as well as their interaction with conventional endocrine and chemotherapeutic drug regimens remain largely unknown. The present study utilized a human cell culture model for ER+ clinical breast cancer to examine the potential therapeutic efficacy of an aqueous extract prepared from the fruit of popular Chinese herb Cornus officinalis (CO), also known as Fructus cornii. The human mammary carcinoma-derived MCF-7 cell line represented the model. Status of anchorage-independent growth and cellular metabolism of 17β-estradiol (E₂) represented the quantitative end-point biomarkers for efficacy. MCF-7 cells adapted for growth in serum-depleted medium (0.7% serum, <1 nM E₂) retained their endocrine responsiveness as evidenced by growth promotion by physiological levels of E₂, and growth inhibition by the selective ER modulator tamoxifen at the clinically achievable concentrations. Treatment of MCF-7 cells with CO resulted in inhibition of E₂-stimulated growth in a dose-dependent manner. Similarly, CO treatment also produced a dose-dependent progressive reduction in the number of anchorage-independent colonies, indicating effective reduction of the carcinogenic risk. Treatment of MCF-7 cells with CO at a maximally effective cytostatic concentration resulted in a 5.1-fold increase in the formation of the anti-prolifertive E₂ metabolite 2-hydoxyestrone (2-OHE₁), a 63.6% decrease in the formation of the pro-mitogenic metabolite 16α-hydroxestrone (16-αOHE₁) and a 9.1% decrease in the formation of mitogenically inert metabolite estrone (E₃). These alterations led to a 14.5-fold increase in the 2-OHE₁:16α-OHE₁, and a 3.3-fold increase in the E₃:16α-OHE1 ratios. These data validate a rapid cell culture-based mechanistic approach to prioritize efficacious herbal medicinal products for long-term animal studies and future clinical trials on ER+ clinical breast cancer.

Diindolylmethane (DIM) spontaneously forms from indole-3-carbinol (I3C) during cell culture experiments

Indole-3-carbinol (I3C) when given orally is converted to diindolylmethane (DIM) and other oligomers catalyzed by stomach acid. This suggests that DIM is the predominant active agent and that I3C is a precursor, 'pro-drug' in vivo. However, in cell culture studies carried out in neutral solutions, I3C has been considered fully active.

MATERIALS AND METHODS

The stability of I3C in cell culture media was studied.

RESULTS

In the 8 different cell culture media tested, greater than 50% dimerization of I3C into DIM occurred in 24 hours. At 48 hour, greater than 60% conversion was found. When neutral synthetic cerebrospinal fluid (CSF) or peritoneal fluid (PF) was studied, a large peak, tentitively identified as I3C's linear trimer (LTR) conversion product by mass spectra, and two smaller peaks, were seen. When CSF or PF was diluted 1:1 with media, the formation of these additional peaks was diminished.

CONCLUSION

Because of the greater biologic potency of DIM when studied in parallel with I3C in vitro, this extent of dimerization shows that DIM rather than I3C is the active agent in cell culture studies.

Influence of postmenopausal hormone replacement therapy on an estrogen metabolite biomarker of risk for breast cancer

Whether postmenopausal hormone-replacement therapy (HRT) increases the risk of breast cancer remains controversial, despite numerous epidemiological studies. We approached the question from a biochemical rather than an epidemiological direction - we hypothesized that if estrogen administration increases the risk of breast cancer, it should also alter a known estrogen biomarker of risk towards what has been observed in patients who already have breast cancer. The specific biomarker we studied was the ratio of the urinary excretion of two principal estradiol metabolites, 2-hydroxyestrone and 16 alpha-hydroxyestrone, which is markedly decreased in women with breast cancer and women with familial risk for breast cancer. We studied 34 healthy postmenopausal women not on HRT and 19 women on HRT (Premarin 0.625 mg daily plus Provera, 2.5 mg daily, in women with a uterus and Premarin alone in women without a uterus); treatment duration ranged from 3 months to 15 years. We also studied four women with recently diagnosed, untreated breast cancer. The women with breast cancer showed a significantly lower 2-hydroxyestrone to 16 alpha-hydroxyestrone ratio than control women on HRT (1.35 +/- 0.13 vs. 2.71 +/- 0.84; p < 0.0001). There was no significant difference in the metabolite ratio between healthy women on HRT and women not on HRT (2.82 +/- 0.92 vs. 2.71 +/- 0.84). There was no significant difference between women receiving Premarin alone and women receiving Premarin plus Provera (2.46 +/- 0.84 vs. 3.13 +/- 0.90), and neither differed significantly from women not on HRT (2.71 +/- 0.84). The finding that the ratio of women on HRT was not decreased to or toward the ratio in women with breast cancer can be interpreted, we believe, as a suggestive item of biochemical evidence that HRT is not a risk for breast cancer.

Predictors of the plasma ratio of 2-hydroxyestrone to 16alpha-hydroxyestrone among pre-menopausal, nulliparous women from four ethnic groups

Studies of circulating estrogen levels in relation to pre-menopausal breast cancer risk have yielded inconsistent results. Various estrogen metabolites might affect the risk differently. Estradiol metabolism occurs primarily via two mutually exclusive pathways, yielding 2-hydroxyestrone (2-OHE) and 16alpha-hydroxyestrone (16alpha-OHE). Most, but not all, studies have found that a relatively high 2-OHE/16alpha-OHE ratio is associated with a low breast cancer risk. Our objective was to determine if the 2-OHE/16alpha-OHE ratio in plasma correlates with suspected breast cancer risk factors and other lifestyle factors, such as ethnicity, body size, age at menarche, oral contraceptive use, smoking, vegetarian diet, coffee and alcohol consumption in 513 nulliparous women, aged 17-35. Oral contraceptive users had significantly lower 2-OHE/16alpha-OHE ratios than pill non-users (P = 10(-21)). Among women who were not using oral contraceptives, the median 2-OHE/16alpha-OHE ratio in plasma was similar for white, black, Indian/Pakistani and Asian women, after adjustment for age and menstrual cycle phase. Among oral contraceptive users, Asian women had significantly lower 2-OHE/16alpha-OHE ratios than white women, and this result remained after adjustment for age and day of menstrual cycle. Daily coffee consumption was significantly positively correlated with 2-OHE/16alpha-OHE ratios (r(s) = 0.18, P = 0.002) only among pill non-users. Our findings suggest that the plasma 2-OHE/16alpha-OHE ratio is associated with constitutional factors and with modifiable lifestyle factors. The reported elevated risk of early onset breast cancer among young oral contraceptive users could be mediated in part through altered estrogen metabolism induced by synthetic estrogens and progestins.

Quantitative determination of 3,3'-diindolylmethane in urine of individuals receiving indole-3-carbinol

Indole-3-carbinol (I3C) or, more correctly, its acid condensation products act as chemoprotective agents via several mechanisms. It induces the expression of cytochrome P-450 1A1, which shifts the estrogen metabolic pathway in favor of C-2 hydroxylation and away from the formation of 16 alpha-hydroxyestrone, a suspected endogenous carcinogen. Increased 16 alpha-hydroxylation of estrogen is associated with greater risk of cancer of the cervix, breast, endometrium, and larynx. The production of 4-hydroxyestrone is also inhibited by I3C. I3C can induce a G1 cell cycle arrest in human MCF-7 breast cancer cells. It can suppress aberrant crypt foci. I3C significantly inhibits the cell adhesion, spreading, and invasion associated with an upregulation of PTEN (a tumor suppressor gene) and E-cadherin (a regulator of cell-cell adhesion) expression in T47-D human breast cancer cells. Thus I3C exhibits anticancer activities by suppressing breast tumor cell growth and metastatic spread. A gas chromatography-mass spectrometry method for the quantitation of diindolylmethane, the principal acid condensation product of I3C, has been developed for use in determining compliance in subjects who have been treated with I3C. The method utilizes a 1-ml urine sample. We have used this method to correlate I3C ingestion with regression of cervical intraepithelial neoplasia in a population of women at risk for cervical cancer. The assay provides an objective marker of consumption using a noninvasive biological fluid and illustrates that diindolylmethane may be used as a marker of compliance in I3C dietary intervention studies.

Abrogation of estrogen-mediated cellular and biochemical effects by indole-3-carbinol

The use of naturally occurring phytoantiestrogens for prevention and therapy of breast cancer is an alternative to synthetic antiestrogens. We have been examining the mechanism of action of the antiestrogen indole-3-carbinol (I3C), a constituent of compounds present in cruciferous vegetables. I3C abrogates the cell-proliferative effect of 17 beta-estradiol (E2), as observed in several different estradiol-responsive breast cancer cell lines and isolated cell clones. Modulation of E2 activity by I3C, in part, was by the induction of the 2-hydroxylation pathway, one of the two competing hydroxylation pathways of estrone conversion that resulted in the formation of metabolites with antiestrogenic properties. I3C-mediated induction of the 2-hydroxylation pathway correlated with a selective induction of cytochrome P-450 1A1 by I3C in E2-responsive human breast cancer cells. Induction of neither the 2-hydroxylation pathway nor cytochrome P-450 1A1 was observed in estrogen-nonresponsive human breast cancer cells. This selective effect warranted a further search for biochemical targets of I3C related to E2 function. To this end, we observed that E2-mediated phosphorylation of the estrogen receptor is inhibited by I3C. Our results are consistent with the hypothesis that I3C exerts its antiestrogenic effect by intervention in the E2-estrogen receptor signal transduction pathways and by alterations in E2 metabolism that resulted in the formation of metabolites with antiestrogenic activity.

Urinary estrogen metabolites and mammographic parenchymal patterns in postmenopausal women

It has been hypothesized that women who metabolize their endogenous estrogens predominantly via 16(alpha)-hydroxylation rather than via 2-hydroxylation and, as a result, have a low ratio of 2-hydroxyestrone (2-OHE1):16(alpha)-hydroxyestrone (16(alpha)-OHE1) are at an increased risk of breast cancer. Epidemiological evidence in support of this hypothesis is scarce and mostly based on measurements made after the onset of the disease. To gain insight into the role of these metabolites in the etiology of breast cancer, we assessed their relationship with high-density Wolfe mammographic parenchymal patterns (P2/DY), a recognized indicator of risk of this tumor. The study was nested within a large cross-sectional survey on determinants of mammographic patterns carried out in a population-based breast screening program in Northern Greece. Urinary levels of 2-OHE1 and 16(alpha)-OHE1 were measured in a random sample of 70 postmenopausal women with P2/DY mammographic patterns and in a random sample of 70 women with N1 mammographic patterns, individually matched to the P2/DY women on year of birth, years since menopause and date of urine collection. Women with a P2/DY pattern had, on average, 58% higher levels of 2-OHE1 (P = 0.002) and 15% higher levels of 16(alpha)-OHE1 (P = 0.37) than those with an N1 pattern. The ratio of 2-OHE1:16(alpha)-OHE1 was 35% higher (P = 0.005) in women with a P2/DY pattern. Women in the highest one-third of this ratio were six times more likely to have a P2/DY pattern than those in the lowest one-third after adjusting for potential confounders (prevalence odds ratio, 6.2; 95% CI, 1.7-22.9; test for linear trend, P = 0.002). These findings seem to suggest that a high, rather than a low, 2-OHE1:16(alpha)-OHE1 ratio may be associated with an increase in breast cancer risk at postmenopausal ages, unless the pathway through which estrogen metabolites may affect breast cancer risk is unrelated to mammographic parenchymal patterns.

Reciprocal expression of ERalpha and ERbeta is associated with estrogen-mediated modulation of intestinal tumorigenesis

Menopausal hormone replacement therapy has been widely used to alleviate the symptoms of menopause and to decrease the detrimental effects of ovarian hormone loss on bone density and cardiovascular health. Multiple studies of colorectal cancer epidemiology also support a role for hormone replacement therapy in prevention of colorectal cancer. We studied the effect of ovariectomy and estrogen replacement on tumor formation in C57BL/6J-Min/+ (Min/+) mice, animals that bear a germline mutation in murine Apc. These mice develop multiple intestinal tumors that show loss of wild-type Apc protein. After ovariectomy, intestinal adenomas in Min/+ mice increased by 77% (P = 0.0004). Ovariectomized Min/+ mice that were treated with a replacement dose of 17beta-estradiol had the same number of tumors as Min/+ mice that were neither castrated nor treated with estrogen replacement (P = 0.85). Examination of estrogen receptor (ER) levels in intestinal tissue by immunoblot showed changes in relative expression levels of ERalpha and ERbeta, with highest ERalpha and lowest ERbeta expression in the normal-appearing intestine of Min/+ mice, and lowest ERalpha and highest ERbeta expression in the enterocytes of animals that received 17beta-estradiol. These results suggest that endogenous estrogens protect against Apc-associated tumor formation and that tumor prevention by 17beta-estradiol is associated with an increase in ERbeta and a decrease in ERalpha expression in the target tissue.

Estrogen metabolism as a risk factor for head and neck cancer

OBJECTIVE

Estrogen metabolites have been associated in the pathogenesis of breast and cervical cancer; 16alpha-hydroxyestrone(16alpha-OHE1) demonstrated proliferative effects whereas 2-hydroxyestrone(2-OHE1) had antiproliferative effects. Our study's objective is to demonstrate that head and neck (H&N) cancer patients metabolize estrogen differently than healthy controls, which may constitute a risk factor for H&N cancer development.

STUDY DESIGN

Urinary metabolite levels of 2-OHE1 and 16alpha-OHE1 from 50 H&N cancer patients and 50 age- and sex-matched controls were measured using enzyme-linked immunosorbent assay (ELISA). Absolute values and 2-/16alpha-OHE1 ratios were calculated. Conditional logistic regression for univariate and multivariate analysis with odds ratio (OR) and 95% confidence interval (CI) were used.

RESULTS

Thirty percent (15 of 50) from the case group had a low 2-/16alpha-OHE1 ratio compared with only 4% (2 of 50) in the control group (OR = 11.1; 1.4-91.5, 95% CI) (P < 0.05). When adjusted for tobacco, OR remained significant at 15.6 (1.1-212.5, 95% CI) (P < 0.05).

CONCLUSION

H&N cancer patients are more likely to express abnormal estrogen metabolism than healthy controls; 2-/16alpha-OHE1 may serve as a potential biological marker of individuals at increased risk of H&N cancer.

DHEA-PC slows the progression of type 2 diabetes (non-insulin-dependent diabetes mellitus) in the ZDF/Gmi-fa/fa rat

The etiology of non-insulin-dependent diabetes mellitus (NIDDM) is complex and development is manifested by initial insulin resistance coupled with elevated insulin levels in the early diabetic state with concomitant increases in circulating levels of glucose and triglycerides. This is followed by a decline in insulin levels due to pancreatic exhaustion. Our results show that administration of DHEA-PC, a phosphocholine conjugate of dehydroepiandrosterone (DHEA), delayed the development of NIDDM symptoms and the onset of type 2 diabetes in the ZDF/Gmi-fa/fa rat model. The treatment consisted of weekly implantation of subdermal osmotic infusion pumps in the rats starting at 6 weeks of age (n = 5 animals per group). For the first three weeks the pumps delivered 6 mg/day/rat followed by 12 mg/day/rat for 1 week (control group pumps delivered only carrier vehicle) after which the pumps were removed. Plasma was collected weekly from day 0 through day 58, and glucose, triglycerides, cholesterol, insulin, IGF-1, and IGF-BP3 levels were measured. Data were analyzed by two-way ANOVA. Following 3 weeks of treatment with DHEA-PC, plasma glucose levels in the treated group remained low, 150+/-9 mg/dL, while the levels in the control animals steadily increased to 320+/-100 mg/dL (p < 0.05). After the DHEA-PC treatment ended, plasma glucose plateaued for 10 days and then took 25 days to reach the level in the control animals (p < 0.05). After 2 weeks of DHEA-PC treatment, plasma triglyceride levels in the treated group remained low, 85+/-24 mg/dL, while the level in the control rats increased to 180+/-35 mg/dL (p < 0.05). After the treatment was terminated triglyceride levels in the treated group increased to control levels within 2 days. Insulin, IGF-1, IGF-BP3, cholesterol, body weight, and food consumption were not changed by DHEA-PC treatment (p < 0.05). Therefore, the delay of increases in plasma glucose and triglycerides, caused by DHEA-PC, was not the result of differences in caloric intake, increased insulin, or increased IGF-1 levels. The data suggest that DHEA-PC delayed the onset of the two most important parameters of NIDDM, namely hyperglycemia and hypertriglyceridemia. (ZDF/Gmi-fa/fa rats and their care was supplied by contract with Genetic Models Inc., Indianapolis, IN.).

Estrone and estradiol metabolism in vivo in human breast cysts

Fibrocystic disease of the breast manifesting palpable cysts express breast cyst fluids frequently containing estrogen sulfates at concentrations far exceeding those found in sera of the patient. The study explored the potential of the breast cyst to synthesize some of these estrogen sulfates. Deuterated estrone and estradiol were synthesized and either (estradiol, 4 cases or estrone, 2 cases) was injected into a cyst. The cyst was aspirated at approximately 0, 4 and 8 h, the target being 1 ml, 50% and complete aspiration respectively. Metabolites were purified sequentially by ether extraction, enzymatic hydrolysis of estrogen conjugates, chromatography on Sephadex LH 20 and identified by gas chromatography linked to mass spectrometry. The unconjugated fraction isolated from the ether extract was subjected to the same purification and detection scheme. Among the conjugates, deuterated estrone sulfate was the major metabolite of either precursor in all studies, while estradiol sulfate was not detected in any of the 6 experiments. The sulfate fractions also yielded traces of 16alpha-hydroxyestrone (2 studies), 4-hydroxyestrone (4 studies) and 2-hydroxyestrone (1 study). In the unconjugated fraction, one study with deuterated estradiol, 4- hydroxyestrone was obtained. In one study with deuterated estrone, traces of 2-hydroxyestrone and 16alpha- hydroxyestrone were obtained. These novel data are significant because patients with fibrocystic disease are at slightly elevated risk for developing breast cancer and 16alpha-hydroxyestrone and 4- hydroxyestrone are reported carcinogens.

Estrogen metabolism and risk of breast cancer: a prospective study of the 2:16alpha-hydroxyestrone ratio in premenopausal and postmenopausal women

Experimental and clinical evidence suggests that 16alpha-hydroxylated estrogen metabolites, biologically strong estrogens, are associated with breast cancer risk, while 2-hydroxylated metabolites, with lower estrogenic activity, are weakly related to this disease. This study analyzes the association of breast cancer risk with estrogen metabolism, expressed as the ratio of 2-hydroxyestrone to 16alpha-hydroxyestrone, in a prospective nested case-control study. Between 1987 and 1992, 10,786 women (ages 35-69 years) were recruited to a prospective study on breast cancer in Italy, the "Hormones and Diet in the Etiology of Breast Cancer" (ORDET) study. Women with a history of cancer and women on hormone therapy were excluded at baseline. At recruitment, overnight urine was collected from all participants and stored at -80 degrees C. After an average of 5.5 years of follow-up, 144 breast cancer cases and four matched controls for each case were identified among the participants of the cohort. Among premenopausal women, a higher ratio of 2-hydroxyestrone to 16alpha-hydroxyestrone at baseline was associated with a reduced risk of breast cancer: women in the highest quintile of the ratio had an adjusted odds ratio (OR) for breast cancer of 0.58 [95% confidence interval (CI) = 0.25-1.34]. The corresponding adjusted OR in postmenopausal women was 1.29 (95% CI = 0.53-3.10). Results of this prospective study support the hypothesis that the estrogen metabolism pathway favoring 2-hydroxylation over 16alpha-hydroxylation is associated with a reduced risk of invasive breast cancer risk in premenopausal women.

Placebo-controlled trial of indole-3-carbinol in the treatment of CIN

OBJECTIVE

Most precancerous lesions of the cervix are treated with surgery or ablative therapy. Chemoprevention, using natural and synthetic compounds, may intervene in the early precancerous stages of carcinogenesis and prevent the development of invasive disease. Our trial used indole-3-carbinol (I-3-C) administered orally to treat women with CIN as a therapeutic for cervical CIN.

METHODS

Thirty patients with biopsy proven CIN II-III were randomized to receive placebo or 200, or 400 mg/day I-3-C administered orally for 12 weeks. If persistent CIN was diagnosed by cervical biopsy at the end of the trial, loop electrocautery excision procedure of the transformation zone was performed. HPV status was assessed in all patients.

RESULTS

None (0 of 10) of the patients in the placebo group had complete regression of CIN. In contrast 4 of 8 patients in the 200 mg/day arm and 4 of 9 patients in the 400 mg/day arm had complete regression based on their 12-week biopsy. This protective effect of I-3-C is shown by a relative risk (RR) of 0.50 ((95% CI, 0. 25 to 0.99) P = 0.023) for the 200 mg/day group and a RR of 0.55 ((95% CI, 0.31 to 0.99) P = 0.032) for the 400 mg/day group. HPV was detected in 7 of 10 placebo patients, in 7 of 8 in the 200 mg/day group, and in 8 of 9 in the 400 mg/day group.

CONCLUSIONS

There was a statistically significant regression of CIN in patients treated with I-3-C orally compared with placebo. The 2/16 alpha-hydroxyestrone ratio changed in a dose-dependent fashion.

Phytochemicals as modulators of cancer risk

These results, describing antitumor activity of some of the phytochemicals that have been actively studied, suggest that dietary changes could play a role in decreasing the incidence of a variety of tumors. 13C and the other compounds discussed may well be only prototypes for other as yet unexplored phytochemicals present in the diet. There have been no attempts to explore the possibilities of synergistic action among the various phytochemicals, 13C, limonene, curcumin, epigallocatechin gallate, sulforaphene, or genistein. Mixtures of these compounds might well show potency at lower doses for each of the compounds and show even greater promise than that already demonstrated.

Endocrine characteristics of human breast epithelial cells, MCF-10F

MCF-10F is a spontaneously immortalized nontransformed human breast epithelial cell line which does not grow in soft agar or form tumors in nude mice. Though the presence of estrogen receptors has not been found in these cells, they can metabolize estradiol very efficiently. The present study describes the endocrine characteristics of this cell line with respect to growth response to estradiol and its metabolites, estradiol metabolism and aromatase activity. MCF-10F cells were growth stimulated by 16alpha-hydroxyestrone and estriol, whereas, estradiol and other estradiol metabolites did not affect cell proliferation. The constitutive level of 16alpha-hydroxyestrone, a metabolite of estradiol biotransformation that has been associated with enhanced carcinogenesis in several animal, cell and tissue culture models, was a hundredfold higher in the non-transformed MCF-10F cells than in the transformed MCF-7 cells. Treatment with the carcinogen, dimethylbenz(a)anthracene (DMBA), however, did not upregulate 16alpha-hydroxylation as was observed in transformed MCF-7 cells. MCF-10F cells also had no detectable aromatase activity though the level of 17-oxidation was unusually high as compared with MCF-7 cells. Our results using the non-transformed MCF-10F cells as a model system suggests that the presence of high level of 16alpha-hydroxyestrone, a metabolite previously shown to be associated with malignant phenotype, may not be sufficient for breast cancer transformation.

Multifunctional aspects of the action of indole-3-carbinol as an antitumor agent

Previous studies from this laboratory have suggested that 2-hydroxyestrone is protective against breast cancer, whereas the other principal metabolite, 16 alpha-hydroxyestrone, and the lesser metabolite quantitatively, 4-hydroxyestrone, are potent carcinogens. Attempts to directly decrease the formation of the 16-hydroxylated metabolite were either unsuccessful or required such high levels of the therapeutic agent as to be impractical. On the other hand the concentration of the protective metabolite, 2-hydroxyestrone, proved to be readily modulated by a variety of agents, both in the direction of increased protection and the opposite direction, increased risk by a variety of agents and activities. We have focussed our attention on indole-3-carbinol, a compound found in cruciferous vegetables, and its further metabolites in the body, diindolylmethane (DIM) and indolylcarbazole (ICZ), because of its relative safety and multifaceted activities. It has been shown that it induces CyP4501A1, increasing 2-hydroxylation of estrogens, leading to the protective 2-OHE1, and also decreases CyP1B1 sharply, inhibiting 4-hydroxylation of estradiol, thereby decreasing the formation of the carcinogenic 4-OHE1. In addition to these indirect effects as a result of altered estrogen metabolism, indole-3-carbinol has been shown to have direct effects on apoptosis and cyclin D, resulting in blockage of the cell cycle. In addition to its antitumor activity in animals, it has also been shown to be effective against HPV-mediated tumors in human patients. All of these responses make the study of its behavior as a therapeutic agent of considerable interest.

A new ELISA kit for measuring urinary 2-hydroxyestrone, 16alpha-hydroxyestrone, and their ratio: reproducibility, validity, and assay performance after freeze-thaw cycling and preservation by boric acid

There is considerable controversy regarding the role of estrogen metabolites in breast cancer risk, fueled in part by the development of a rapid ELISA that is suitable for large scale investigations. An earlier version of the ELISA could detect values of the 2-hydroxyestrone (2-OHE1) and 16alpha-hydroxyestrone (16alpha-OHE1) metabolites as low as 2 ng/ml and produce consistent results in premenopausal urines. However, reproducibility was problematic in postmenopausal urines where concentrations of these compounds are much lower. In response to our concern, a new ELISA was developed with a sensitivity of 0.625 ng/ml, which we evaluated using the same pre- and postmenopausal urine samples analyzed in the earlier ELISA. In this report, we present findings on the new kit with regard to reproducibility of the 2-OHE1 and 16alpha-OHE1 measurements, comparability of results with gas chromatography-mass spectroscopy values, and with regard to the stability of the metabolites after repeated freeze-thaw cycles and after preservation by boric acid. For the most part, we found the new ELISA to be reproducible, with assay coefficients of variation ranging from 10 to 20%, and intraclass correlation coefficients (ICCs) ranging from 80 to 95% in both the pre- and postmenopausal urines. ELISA results for 16alpha-OHE1 differed from 1 day (i.e., batch) to the next, and the absolute values of the metabolites obtained by the ELISA were consistently lower than but well correlated with those obtained by gas chromatography-mass spectroscopy. Values of the 2-OHE1:16alpha-OHE1 ratio also differed between the methods, but because the range of values was not large, the magnitude of these differences was not as great. For the ratio, the correlation between methods was excellent, and the ICCs were high for both groups of women. After preservation by boric acid, values of the ratio varied according to acid concentration but not in a linear fashion. Ratio values were similar in urine samples exposed to four different freeze-thaw cycle treatments, although values for all treatments were consistently lower in one batch. Because batch-to-batch variability was not negligible, it is advisable that matched cases and controls be analyzed in the same batch. Provided this is done, the relatively low assay coefficient of variation and high ICC demonstrate that the new ELISA kit can reliably measure the 2-OHE1:16alpha-OHE1 ratio and detect small case-control differences in large population-based studies, where rapid and relatively easy laboratory methods are critical.

Reproducibility of plasma and urinary sex hormone levels in premenopausal women over a one-year period

Although endogenous sex steroid hormones in premenopausal women may be associated with the risk of breast cancer and other illnesses, direct evidence to support this hypothesis is limited in large part by methodological issues in the conduct of relevant studies. One major unresolved issue is whether a single blood sample (such as is available in most epidemiological studies), collected in a specific phase of the menstrual cycle, reflects long-term levels in that phase. To address this issue, two sets of blood and urine samples were obtained from 87 premenopausal women over a 1-year period in both the follicular and luteal phases. Plasma estradiol, estrone, and estrone sulfate were measured in the blood samples obtained in both phases, whereas progesterone and urinary 2- and 16a-hydroxyestrone were measured in luteal-phase samples only. For all of the women combined, intraclass correlation coefficients (ICCs) ranged, with one exception, from 0.52 to 0.71 for the plasma estrogens and the urinary estrogen metabolites. The sole exception was for estradiol in the luteal phase (ICC = 0.19); inclusion of only women who were ovulatory in both cycles and who collected each sample 4-10 days before their next period resulted in a substantially higher ICC for estradiol in the luteal phase (ICC = 0.62; 95% confidence interval, 0.43-0.78). These data indicate that, for several plasma and urinary sex hormones, a single follicular- or luteal-phase measurement in premenopausal women is reasonably representative of hormone levels in that phase for at least a 1-year period.

Immunological properties of dehydroepiandrosterone, its conjugates, and metabolites

The immunological response to the administration of various C-19 steroids has been of increasing interest. Although the action of dehydroepiandrosterone has been studied, the responses to its metabolites have not been explored. In the present study the ability of dehydroepiandrosterone, its conjugates, and metabolites to oppose the anti-inflammatory action of glucocorticoids on the inflammatory response to 2,4-dinitrochlorobenzene in the sensitized mouse was examined. A clear difference was seen between the antiglucocorticoid activity of dehydroepiandrosterone, its conjugates, and its 5 beta-metabolites on the one hand and the planar 5 alpha- and delta 4-metabolites, which were devoid of antiglucocorticoid activity. The mechanism of this antiglucocorticoid activity remains to be established.

Role of estradiol metabolism and CYP1A1 polymorphisms in breast cancer risk

The endogenous metabolism of estrogens is primarily oxidative and involves hydroxylation of the steroid at either C2 (2-OHE1) or C16 (16-OHE1). While the 2-OHE1 metabolites are essentially devoid of peripheral biological activity, 16-OHE1 is an estrogen agonist. There is evidence of an association between the 2-OHE1/16-OHE1 metabolites ratio and breast cancer risk. The CYP1A1 gene may play a role in the 2-hydroxylation (2-OH) of estradiol. African-American women with the wild-type CYP1A1 gene showed a significant increase in the 2-OHE1/16-OHE1 ratio, from 1.35 +/- 0.56 at baseline to 2.39 +/- 0.98 (p = 0.006) after 5 days of treatment with indole-3-carbinol (400 mg/day), a 2-OHE1 inducer. Women with the Msp1 polymorphism showed no significant increase, (0.37% +/- 0.17%). In a case-control study involving 57 women with breast cancer and 312 female controls, the frequency of the homozygous Msp1 polymorphism was 4.2% in African-American controls and 16% in African-American breast cancer cases. The odds ratio of breast cancer with the Msp1 homozygous variant was 8.4 (95% confidence interval: 1.7-41.7). This association was not observed in Caucasian women. The other CYP1A1 polymorphisms were not associated with breast cancer. The CYP1A1 Msp1 polymorphism may be a marker of altered estradiol metabolism and of increased susceptibility to estrogen-related breast cancer in African-Americans.

Anti-estrogenic activities of indole-3-carbinol in cervical cells: implication for prevention of cervical cancer

BACKGROUND

Cervical cancer constitutes the second most common cancer in women. Estrogen promotes development of cervical cancer in cells infected with high risk human papillomaviruses (HPVs). We asked whether the phytochemical indole-3-carbinol (I3C) has anti-estrogenic activities in cervical cells with the goal of preventing cancer in HPV infected cells.

MATERIALS AND METHODS

Using the cervical cancer cell line CaSki, we evaluated expression of HPV and cytochrome p450 (CYP) enzymes by Northern, RNase protection or quantitative RT-PCR. I3C binding to estrogen receptor was measured by competition with estradiol. Estrogen metabolites were measured by gas chromarography-mass spectrometry (GC-MS).

RESULTS

Estradiol increased expression of HPV oncogenes whereas I3C and the estrogen metabolite 2-hydroxyestrone (2-OHE) abrogated the estrogen-increased expression of HPV oncogenes. Both I3C and 2-OHE competed with estradiol for estrogen receptor binding. I3C enhanced gene expression of CYP enzymes responsible for 2-hydroxylation of estrogen, and induced the formation of 2-OHE.

CONCLUSION

I3C has anti-estrogenic activities which should prevent cancer in cervical cells.

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.

Estrogen metabolism and laryngeal papillomatosis: a pilot study on dietary prevention

Evidence exists that estrogen metabolism has a role in the pathogenesis of recurrent respiratory papillomatosis (RRP). This disease has a papillomavirus etiology and is characterized by recurrent benign tumors with a significant propensity to become malignant. We have measured the systemic transformation of estrogen using an enzyme-linked-immunoassay to measure estrogen metabolites in the urine of patients with RRP and compared these ratios to the severity of RRP, a measure of the average growth rate of papillomas. Our results show an inverse relationship between the ratio of C-2 to C-16 alpha-hydroxylated estrogens and the severity of RRP. In a pilot study, patients consumed cruciferous vegetables to induce C-2-hydroxylation. In this group of patients, an increase in the ratio correlated with an improvement in RRP. The ratio did not change in a subset of these patients, and their RRP did not improve. Regardless, the ratio correlated with severity of their RRP.

Application of an improved ELISA assay to the analysis of urinary estrogen metabolites

Work from Strang and other laboratories has established that the 2-/16 alpha-hydroxyestrone ratio is inversely correlated with the risk for breast and cervical cancer. In order to measure these metabolites in urine samples, it is essential to have an assay for these compounds that is both sensitive and reproducible. The present paper describes such an ELISA assay, which overcomes problems that existed in prior approaches to measuring these compounds. The new ELISA procedure supplies greater sensitivity and reproducibility than earlier assay procedures. The ELISA assay has also been found to correlate well with the GC-MS procedure of Adlercreutz.

Examination of genotype and phenotype relationships in 14 patients with apparent mineralocorticoid excess

Apparent mineralocorticoid excess (AME) is a genetic disorder causing pre- and postnatal growth failure, juvenile hypertension, hypokalemic metabolic alkalosis, and hyporeninemic hypoaldosteronism due to a deficiency of 11 beta-hydroxysteroid dehydrogenase type 2 enzyme activity (11 beta HSD2). The 11 beta HSD2 enzyme is responsible for the conversion of cortisol to the inactive metabolite cortisone and therefore protects the mineralocorticoid receptors from cortisol intoxication. Several homozygous mutations are associated with this potentially fatal disease. We have examined the phenotype, biochemical features, and genotype of 14 patients with AME. All of the patients had characteristic signs of a severe 11 beta HSD2 defect. Birth weights were significantly lower than those of their unaffected sibs. The patients were short, underweight, and hypertensive for age. Variable damage of one or more organs (kidneys, retina, heart, and central nervous system) was found in all of the patients except one. The follow-up studies of end-organ damage after 2-13 yr of treatment in six patients demonstrated significant improvement in all patients. The urinary metabolites of cortisol demonstrated an abnormal ratio with predominance of cortisol metabolites, i.e. tetrahydrocortisol plus 5 alpha-tetrahydrocortisol/tetrahydrocortisone was 6.7-33, whereas the normal ratio is 1.0. Infusion of [11-3H]cortisol resulted in little release of tritiated water, indicating the failure of the conversion of cortisol to cortisone. Thirteen mutations in the HSD11B2 gene have been previously published, and we report three new genetic mutations in two patients, one of whom was previously unreported. All of the patients had homozygous defects except one, who was a compound heterozygote. Our first case had one of the most severe mutations, resulting in the truncation of the enzyme 11 beta HSD2, and died at the age of 16 yr while receiving treatment. Three patients with identical homozygous mutations from different families had varying degrees of severity of clinical and biochemical features. Due to the small number of patients with identical mutations, it is difficult to correlate genotype with phenotype. In some cases, early and vigilant treatment of AME patients may prevent or improve the morbidity and mortality of end-organ damage such as renal or cardiovascular damage and retinopathy. The outcome of treatment in more patients may establish the efficacy of treatment.

Preliminary results of the use of indole-3-carbinol for recurrent respiratory papillomatosis

OBJECTIVE

We report the preliminary results of a phase I trial using indole-3-carbinol for the treatment of recurrent respiratory papillomatosis. Indole-3-carbinol is a chemical that is found in high concentrations in cruciferous vegetables and has been shown to alter the growth pattern of recurrent respiratory papillomatosis cell cultures and to be effective in an in vivo animal model of recurrent respiratory papillomatosis.

METHODS

Eighteen patients were treated with oral indole-3-carbinol and had a minimum follow-up of 8 months and a mean follow-up of 14.6 months. All patients received indole-3-carbinol, and outcome measures included a change in papilloma growth rate and the need for surgery during treatment compared with before treatment. All patients had serial examinations with videoendoscopy to document papilloma location and growth rate.

RESULTS

Thirty-three percent (6 of 18) of the study patients had a cessation of their papilloma growth and have not required surgery since the start of the study. Six patients have had reduced papilloma growth rate, and 6 (33%) patients have shown no clinical response to indole-3-carbinol. Indole-3-carbinol affects the ratio of hydroxylation of estradiol; changes in the ratios of urinary 2-hydroxylation and 16-hydroxylation of estradiol caused by indole-3-carbinol correlated well with clinical response. No major complications or changes in the children's growth curve were noted.

CONCLUSIONS

The preliminary results of treating recurrent respiratory papillomatosis with indole-3-carbinol holds promise. Longer follow-up of this patient group and a blinded, controlled trial are required. We conclude that indole-3-carbinol appears to be safe and well tolerated and may be an efficacious treatment for recurrent respiratory papillomatosis.

Alteration of oestradiol metabolism in myc oncogene-transfected mouse mammary epithelial cells

Targeted overexpression of the c-myc oncogene induces neoplastic transformation in immortalized, non-tumorigenic mouse mammary epithelial cells (MMEC). Experiments in the present study were conducted to examine whether cellular transformation induced by c-myc oncogene is associated with altered metabolism of 17beta-oestradiol (E2). The parental, MMEC and the stable c-myc transfectant (MMEC/myc3) cell lines were compared for major oestrogen metabolic pathways, namely E2 and E1 interconversion, and C2- and C16alpha-hydroxylation by both high-pressure liquid chromatography (HPLC) analysis and the 3H release assay using specifically labelled [C2-3H]E2 or [C16alpha-3H]E2. The reductive conversion of E1 to E2 was about 14-fold and 12-fold higher than the oxidative conversion of E2 to E1 in MMEC and MMEC/myc3 cells respectively. However, in MMEC/myc3 cells, both reductive and oxidative reactions were decreased by about 32% and 12% relative to those seen in the parental MMEC cells (P = 0.0028). The extent of C16alpha-hydroxylation was increased by 164.3% (P < 0.001), with a concomitant 48.4% decrease (P < 0.001) in C2-hydroxylation in MMEC/myc3 cells; this resulted in a fourfold increase in the C16alpha/C2 hydroxylation ratio in this cell line. Thus, a persistent c-myc expression, leading to aberrant hyperproliferation in vitro and tumorigenesis in vivo, is associated with an altered oestrogen metabolism. However, it remains unclear whether this represents a result of oncogene expression/activation or is rather a consequence of phenotypic transformation of the cells.

Negative growth regulation of oncogene-transformed mammary epithelial cells by tumor inhibitors

Deregulated expression of Ras and myc oncogenes confers neoplastic transformation in non-tumorigenic mammary epithelial cells. Down-regulation of perturbed biomarkers prior to tumorigenesis may provide a means of effective chemoprevention. In vitro experiments were designed to i) identify specific molecular, endocrine and cellular biomarkers as quantitative end points for preneoplastic transformation, and ii) utilize these end points to evaluate chemopreventive efficacy of selected naturally-occurring and synthetic tumor inhibitors. Stable Ras and myc transfectants exhibited persistent expression of oncogene specific mRNA transcripts, altered estradiol biotransformation and enhanced anchorage-independent growth in vitro prior to tumorigenesis in vivo. Treatment of the transfectants with omega-3-fatty acid, indole-3-carbinol and tamoxifen individually suppressed the perturbed molecular, endocrine and cellular biomarkers in vitro. Thus, suppressed oncogene expression and altered estrogen metabolism may be important determinants for antiproliferative mechanisms in mammary tumor inhibition, providing useful end points for chemopreventive intervention of preneoplasia.

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.

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.

Inhibition of proliferation and modulation of estradiol metabolism: novel mechanisms for breast cancer prevention by the phytochemical indole-3-carbinol

Aberrant proliferation is an early-occurring intermediate event in carcinogenesis whose inhibition may represent preventive intervention. Indole-3-carbinol (I3C), a glucosinolate metabolite from cruciferous vegetables, inhibits organ site carcinogenesis in rodent models. Clinically relevant biochemical and cellular mechanisms for the anticarcinogenic effects of I3C, however, remain unclear. Experiments were conducted on reduction mammoplasty derived 184-B5 cells initiated with chemical carcinogen (184-B5/BP) or with oncogene (184-B5/HER), and on mammary-carcinoma-derived MDA-MD-231 cells to examine whether (i) I3C inhibits aberrant proliferation in initiated and transformed cells, and (ii) inhibition of aberrant proliferation is associated with altered cell-cycle progression, estradiol (E2) metabolism, and apoptosis. Aberrant proliferation in 184-B5/BP, 184-B5/HER, and MDA-MB-231 cells was evident by a 55%-67% decrease in the ratio of quiescent (Q = G0) to proliferative (P = S + M) phase of the cell cycle, a 72%-90% decrease in apoptosis, and a 76%-106% increase in anchorage-dependent growth. These cells also exhibited a 88%-90% decrease in the ratio of C2 to C16alpha-hydroxylation products of E2. Treatment of 184-B5/BP, 184-B5/HER, and MDA-MB-231 cells to cytostatic dose of 50 microM I3C resulted in an 137%-210% increase in Q/P I3C ratio, a 4- to 18-fold increase in E2 metabolite ratio, a 2-fold increase in cellular apoptosis, and a 54%-61% inhibition of growth. The preventive efficacy of I3C on human mammary carcinogenesis may be due in part to its ability to regulate cell-cycle progression, increase the formation of antiproliferative E2 metabolite, and induce cellular apoptosis.

Interaction between a semisynthetic diet and indole-3-carbinol on mammary tumor incidence in Balb/cfC3H mice

This paper extends prior studies on the chemoprotective effect of indole-3-carbinol (I3C) on mammary and endometrial tumors in rodent models and focuses on the interplay between standard laboratory chow (Purina Lab Chow 5001), a high omega 6 fatty acid diet (AIN76A), and I3C on the incidence of mouse mammary tumor virus-induced (MMTV) mammary tumors in mice. While the protective effect of I3C was observed in mice maintained on the AIN76A diet from conception, a marked decrease in tumor incidence was observed, which was found to be directly related to the extent of time the mice were maintained on the Purina 5001 diet prior to the switch to the AIN76A control diet. This protective effect of the chow diet against MMTV-induced tumors has not been previously reported. The effects of the chow diet and I3C do not appear to be additive or synergistic.

Urinary estrogen metabolites and breast cancer: a case-control study

Preliminary studies suggest that the estrogen metabolite 16 alpha-hydroxyestrone is associated with breast cancer, whereas 2-hydroxyestrone is not. However, epidemiological studies evaluating this relationship and taking established risk factors for breast cancer into account are lacking. The purpose of this study was to examine the association of the ratio of the urinary estrogen metabolites (2-hydroxyestrone and 16 alpha-hydroxyestrone) and of the individual metabolites with breast cancer. A spot urine sample, a brief history, and clinical data were collected from breast cancer cases (n = 42) and from women coming to the hospital for a routine mammogram or attending a free breast cancer screening (n = 64). 2-Hydroxyestrone and 16 alpha-hydroxyestrone were measured by enzyme immunoassay, and the estrogen metabolite ratio (EMR; 2-hydroxyestrone:16 alpha-hydroxyestrone) was computed. Cases and controls were similar in terms of age (mean age of cases, 53.8 +/- 15.1 years, versus 54.2 +/- 10.4 years for controls; P = 0.9) and demographics. Mean EMR was not associated with breast cancer overall (1.67 +/- 0.80 versus 1.72 +/- 0.66; P = 0.7). However, in postmenopausal women, the mean EMR was significantly lower in cases compared to controls (1.41 +/- 0.73 versus 1.81 +/- 0.71; P = 0.05). The multivariate adjusted odds ratios for the intermediate and lowest tertiles of the EMR relative to the highest among postmenopausal women were 9.73 (95% confidence interval, 1.27-74.84) and 32.74 (95% confidence interval, 3.36-319.09), respectively. The test for trend was highly significant (P = 0.003). Analyses of the individual metabolites indicated that 16 alpha-hydroxyestrone was a strong risk factor. The EMR did not show any consistent associations with age, race/ethnicity, age at first birth, parity, body mass index, family history of breast cancer, smoking, or alcohol intake. These data suggest a strong, inverse association of the EMR and a strong positive association of 16 alpha-hydroxyestrone with breast cancer in postmenopausal women. Larger studies are needed to confirm these results and to assess the relationship of the EMR and of the individual metabolites with breast cancer, with attention to menopausal status and clinical factors and with adjustment for known breast cancer risk factors.

Effects of indole-3-carbinol on the metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in smokers

Indole-3-carbinol (I3C) is a component of the human diet, occurring as a conjugate in certain cruciferous vegetables. I3C protects against carcinogenesis in a variety of animal models by modifying carcinogen metabolism. In mice, I3C decreases lung tumor formation by the tobacco-specific nitrosamine 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by enhancing its hepatic clearance (M. A. Morse et al., Cancer Res., 50: 2613-2617, 1990). In this study, our goal was to determine whether I3C would have similar effects on NNK metabolism in smokers as it did in mice. Thirteen women took 400 mg of I3C on 5 consecutive days and maintained constant smoking habits during this period. Their urine was analyzed before and after the I3C treatment period for two metabolites of NNK: 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronide (NNAL-Gluc). I3C treatment resulted in decreased levels of urinary NNAL, NNAL-Gluc, and NNAL plus NNAL-Gluc, and increased NNAL-Gluc:NNAL ratio in 10 of the 13 women. The mean decreases in NNAL (-0.27 +/- 0.09 pmol/mg creatinine, -23.4%) and NNAL plus NNAL-Gluc (-0.43 +/- 0.16 pmol/mg creatinine, -10.9%) were statistically significant as was the increase in NNAL-Gluc:NNAL ratio (1.1 +/- 0.5, 39.9%). These changes in urinary metabolites of NNK were consistent with those seen in mice treated with I3C and NNK; they suggest that I3C increased hepatic metabolism of NNK in our smokers. This is the first study to examine the effects of I3C on metabolism of an exogenous carcinogen in humans.

Changes in levels of urinary estrogen metabolites after oral indole-3-carbinol treatment in humans

BACKGROUND

The oxidative metabolism of estrogens in humans is mediated primarily by cytochrome P450, many isoenzymes of which are inducible by dietary and pharmacologic agents. One major pathway, 2-hydroxylation, is induced by dietary indole-3-carbinol (I3C), which is present in cruciferous vegetables (e.g., cabbage and broccoli).

PURPOSE

Because the pool of available estrogen substrates for all pathways is limited, we hypothesized that increased 2-hydroxylation of estrogens would lead to decreased activity in competing metabolic pathways.

METHODS

Urine samples were collected from subjects before and after oral ingestion of I3C (6-7 mg/kg per day). In the first study, seven men received I3C for 1 week; in the second study, 10 women received I3C for 2 months. A profile of 13 estrogens was measured in each sample by gas chromatography-mass spectrometry.

RESULTS

In both men and women, I3C significantly increased the urinary excretion of C-2 estrogens. The urinary concentrations of nearly all other estrogen metabolites, including levels of estradiol, estrone, estriol, and 16alpha-hydroxyestrone, were lower after I3C treatment.

CONCLUSIONS

These findings support the hypothesis that I3C-induced estrogen 2-hydroxylation results in decreased concentrations of several metabolites known to activate the estrogen receptor. This effect may lower estrogenic stimulation in women.

IMPLICATIONS

I3C may have chemopreventive activity against breast cancer in humans, although the long-term effects of higher catechol estrogen levels in women require further investigation.

Quantifying estrogen metabolism: an evaluation of the reproducibility and validity of enzyme immunoassays for 2-hydroxyestrone and 16alpha-hydroxyestrone in urine

Rapid and simple enzyme immunoassays (EIAs) were recently developed to measure 2-hydroxyestrone and 16alpha-hydroxyestrone in unextracted urine. The balance between these competing estrogen metabolism pathways may serve as a biomarker of breast cancer risk. Before testing these assays in epidemiologic studies, we evaluated their reproducibility, and validity relative to gas chromatography-mass spectroscopy (GC-MS). Overnight 12-hr urine collections from five midfollicular premenopausal women, five midluteal premenopausal women, and five postmenopausal women were aliquoted and stored at -70 degrees C. Two aliquots from each woman were assayed with the EIAs in a random, blinded order, monthly over 4 months and 1 year later. Reproducibility over 4 months was good for both metabolites in premenopausal women (coefficient of variation = 8-14%) and satisfactory in postmenopausal women (approximately 19%). Reproducibility over 12 months remained good in premenopausal women, but was poor in postmenopausal women, with mean readings increasing 50 to 100%. Wide variation in estrogen metabolite levels enabled a single EIA measurement to characterize individual differences among premenopausal women in midfollicular (intraclass correlation coefficient = 98-99%) and midluteal phase (85-91%). A narrower range in metabolite levels among postmenopausal women reduced discrimination (78-82%). The correlation between EIA and GC-MS measurement was excellent for both metabolites (r>0.9), except for 2-hydroxyestrone in postmenopausal women (r=0.6). Analysis of absolute agreement suggested that both EIAs were less sensitive than GC-MS, and each detected nonspecific background. The low concentration of estrogen metabolites in urine from postmenopausal women may explain the problems with reproducibility and validity in this menstrual group. Accordingly, more sensitive EIAs have been developed and are now being evaluated.

Estradiol metabolism: an endocrine biomarker for modulation of human mammary carcinogenesis

The natural estrogen 17beta-estradiol (E2) has a profound influence on proliferation and neoplastic transformation of mammary epithelium. The role of cellular metabolism of E2 in mammary carcinogenesis, however, remains to be elucidated. Explant culture and cell culture models developed from noncancerous human mammary tissue were used to examine modulation of E2 metabolism in response to treatment with prototype rodent mammary carcinogens and the ability of the naturally occurring phytochemical indole-3-carbinol (13C) to influence E2 metabolism and regulate aberrant proliferation. In the two models, treatment with the chemical carcinogens 7,12-dimethylbenz[a]anthracene and benzo[a]pyrene altered the metabolism of E2 as determined from the radiometric (tritium release) and gas chromatography-mass spectrometry (GC-MS) assays. This alteration in E2 metabolism was accompanied by aberrant proliferation and abrogation of apoptosis as determined by the extent of replicative DNA synthesis, S-phase fraction and Sub G0 (apoptotic) peak. Exposure of carcinogen-initiated cultures to 13C resulted in induction of C2-hydroxylation of E2 and of apoptosis and downregulation of hyperproliferation. Determination of altered cellular metabolism of E2 in response to initiators and modulators of carcinogenesis and evaluation of cell cycle related markers for proliferation and apoptosis may provide a mechanism-oriented approach to validate E2 metabolism as an endocrine biomarker for induction and prevention of human mammary carcinogenesis.

Medical hypothesis: bifunctional genetic-hormonal pathways to breast cancer

As inherited germ line mutations, such as loss of BRCA1 or AT, account for less than 5% of all breast cancer, most cases involve acquired somatic perturbations. Cumulative lifetime exposure to bioavailable estradiol links most known risk factors (except radiation) for breast cancer. Based on a series of recent experimental and epidemiologic findings, we hypothesize that the multistep process of breast carcinogenesis results from exposure to endogenous or exogenous hormones, including phytoestrogens that directly or indirectly alter estrogen metabolism. Xenohormones are defined as xenobiotic materials that modify hormonal production; they can work bifunctionally, through genetic or hormonal paths, depending on the periods and extent of exposure. As for genetic paths, xenohormones can modify DNA structure or function. As for hormonal paths, two distinct mechanisms can influence the potential for aberrant cell growth: compounds can directly bind with endogenous hormone or growth factor receptors affecting cell proliferation or compounds can modify breast cell proliferation altering the formation of hormone metabolites that influence epithelial-stromal interaction and growth regulation. Beneficial xenohormones, such as indole-3-carbinol, genistein, and other bioflavonoids, may reduce aberrant breast cell proliferation, and influence the rate of DNA repair or apoptosis and thereby influence the genetic or hormonal microenvironments. Upon validation with appropriate in vitro and in vivo studies, biologic markers of the risk for breast cancer, such as hormone metabolites, total bioavailable estradiol, and free radical generators can enhance cancer detection and prevention.