Epidemiology of endocrine-related risk factors for breast cancer

Microdissection and SAGE as a combined tool to reveal gene expression in ductal carcinoma in situ of the breast

The interplay between cancer cells and the normal surrounding tissue is believed to influence the biological behavior of the tumor. However, the presence of multiple cell types within the prelevated tumor specimen may attenuate changes that occur specifically in the malignant cells within their microenvironment. To study gene expression of the malignant cells in situ, we used a new microdissection method to separate ductal carcinoma in situ (DCIS) cells from the surrounding stroma, immunological infiltrates, and endothelial cells. We applied an adapted microSAGE protocol, without total mRNA amplification, to study their gene expression profile. Three thousand two hundred one different transcripts were identified in a total of 29 534 observed tags. Of these unique tags, 88.3% matched known GenBank sequences and 11.7% represented unknown transcripts. As compared to a total DCIS SAGE library, microdissection combined with SAGE revealed additional genes expressed only in normal surrounding, probably stromal, cells and not or significantly less in DCIS tumor cells. This study demonstrates that microdissection can be combined with SAGE as a tool to study transcriptomes. This approach provides important new information on differential gene expression both in tumor cells and normal surrounding tissue. Several of the observed differences indeed disappear when the total tumor mass is analyzed.

The effect of CYP19 and COMT polymorphisms on exercise-induced fat loss in postmenopausal women

OBJECTIVE

To examine whether genetic polymorphisms in CYP19 [intron 4 (TTTA)n; n = 7 to 13 and a 3-base pair deletion, which is in strong linkage disequilibrium with the seven repeat] and COMT (Val108/158Met) modified the change in BMI, total and percentage body fat, or subcutaneous and intra-abdominal fat during a year-long exercise intervention trial. These genes metabolize estrogens and androgens, which are important in body fat regulation.

RESEARCH METHODS AND PROCEDURES

A randomized intervention trial was used, with an intervention goal of 225 min/wk of moderate-intensity exercise for one year. Participants (n = 173) were postmenopausal, 50 to 75 years old, sedentary, overweight or obese, and not taking hormone therapy at baseline.

RESULTS

Exercisers with two vs. no CYP19 11-repeat alleles had a larger decrease in total fat (-3.1 kg vs. -0.5 kg, respectively, p = 0.01) and percentage body fat (-2.4% vs. -0.6%, respectively, p = 0.001). Exercisers with the COMT Met/Met vs. Val/Val genotype had a smaller decrease in percentage fat (-0.7% vs. -1.9%, respectively, p = 0.05). Among exercisers, women with the COMT Val/Val genotype and at least one copy of the CYP19 11-repeat allele vs. those with neither genotype/allele had a significantly larger decrease in BMI (-1.0 vs. +0.1 kg/m2, respectively, p = 0.009), total fat (-2.9 vs. -0.5 kg, respectively, p = 0.004), and percentage body fat (-2.6% vs. -0.4%, respectively, p < 0.001).

DISCUSSION

Genetic polymorphisms in CYP19 and COMT may be important for body fat regulation and possibly modify the effect of exercise on fat loss in postmenopausal women.

A contemporary understanding of progesterone receptor function

Following the discovery of coactivators for nuclear receptors and the identification of a significant number of progesterone receptor (PR) target genes, our understanding of PR action has extended from its normally recognized functions to a wide variety of seemingly unlinked biological processes. Recent advances in defining the action of PR coactivators has revealed important mechanisms involving multiple layers of regulation in PR-mediated transcription. In this review, we will discuss the current understanding of PR physiology and the molecular basis of coactivator function in PR signaling events.

Breast cancer risk after caloric restriction during the 1944-1945 Dutch famine

BACKGROUND

Data from animal models suggest that caloric restriction may reduce the risk of breast cancer, although not all dietary regimens produce similar effects. We examined whether caloric restriction imposed as a consequence of the 1944-1945 Dutch famine reduced the risk of breast cancer in women participating in a Dutch breast cancer screening program.

METHODS

Between 1983 and 1986, approximately 15 000 women, aged 2 to 33 years during the 1944-1945 Dutch famine, responded to a questionnaire about their famine experience. A famine exposure score, graded as absent, moderate, or severe exposure, was derived from answers regarding hunger, cold, and weight loss. During follow-up until January 2000, 585 women with incident breast cancer were identified by the regional cancer registry. The relationship between famine exposure and breast cancer risk was assessed by weighted Cox regression models, in which person-years lived for the entire cohort was extrapolated from data from a random sample of 15% of the cohort.

RESULTS

Women who were severely exposed to the famine had a statistically significantly higher risk of breast cancer (hazard ratio [HR] = 1.48, 95% confidence interval [CI] = 1.09 to 2.01) than women who were not exposed. Women who were moderately exposed to the famine had a 13% increased risk of breast cancer (HR = 1.13, 95% CI = 0.92 to 1.38; P(trend) = 0.016). The association between famine exposure and breast cancer risk was stronger for women who were exposed between the ages of 2 and 9 years (severely exposed versus unexposed: HR = 2.01, 95% CI = 0.92 to 4.41) than for women who were exposed at older ages.

CONCLUSIONS

The risk of breast cancer was increased in women who were severely exposed to a short but severe famine decades earlier. This result is compatible with data from the few animal studies investigating effects of short-term, transient caloric restriction.

Progesterone prevents radiation-induced apoptosis in breast cancer cells

Sex steroid hormones play an essential role in the control of homeostasis in the mammary gland. Although the involvement of progesterone in cellular proliferation and differentiation is well established, its exact role in the control of cell death still remains unclear. As dysregulation of the apoptotic process plays an important role in the pathogenesis of breast cancer, we investigated the regulation of apoptosis by progesterone in various breast cancer cell lines. Our results show that progesterone treatment protects against radiation-induced apoptosis. This prevention appears to be mediated by the progesterone receptor and is unrelated to p53 status. There is also no correlation with the intrinsic hormonal effect on cell proliferation, as the presence of cells in a particular phase of the cell cycle. Surprisingly, progesterone partly allows bypassing of the irradiation-induced growth arrest in G(2)/M in PgR+ cells, leading to an increase in cell proliferation after irradiation. One consequence of this effect is a higher rate of chromosome damage in these proliferating progesterone-treated cells compared to what is observed in untreated irradiated cells. We propose that progesterone, by inhibiting apoptosis and promoting the proliferation of cells with DNA damage, potentially facilitates the emergence of genetic mutations that may play a role in malignant transformation.

Urinary endogenous sex hormone levels in postmenopausal women after caloric restriction in young adulthood

We investigated whether the 1944–1945 Dutch famine has affected postmenopausal sex hormone concentrations with data from 163 women (young adults during the famine). Urinary sex hormone concentrations showed modest elevations with increasing famine exposure. Effects were absent in parous women, but more pronounced in women who had never given birth.

Chylomicron margination, lipolysis, and vitamin a uptake in the lactating rat mammary gland: implications for milk retinoid content

We have reported previously that the concentration of vitamin A (VA) in the milk of lactating rats varies with dietary VA intake, even when plasma retinol concentration is unaffected. In the current study, we investigated the role of lipolysis in the uptake of chylomicron (CM) VA into mammary tissue of lactating rats and estimated the proportion of CM-VA that is associated with the mammary gland during CM clearance. Chylomicrons containing [(3)H]VA, mainly as retinyl esters, were prepared in donor rats and administered intravenously to lactating recipient rats. Chylomicron VA rapidly disappeared from plasma and appeared in mammary tissue (maximum within 2-3 mins), followed by a decline. Concomitantly, uptake by liver increased continuously, reaching a plateau within 20-30 mins. Active lipolysis in mammary tissue was necessary for rapid VA uptake, as significantly less CM-VA was recovered in mammary tissue of postlactating rats than of lactating rats, after heparin treatment in lactating rats, or after injection of preformed CM remnants in lactating rats. [(3)H]Vitamin A uptake by mammary tissue increased linearly with CM-VA dose over a 150-fold dose range (R(2) = 0.972, P = 0.0001), suggesting a high capacity for uptake and apparent first-order assimilation of CM-VA during CM remnant formation in situ. Model-based compartmental analysis using WinSAAM predicted that approximately 42% of CM-VA marginated, that is, were temporarily removed, from plasma to the mammary glands during lipolysis and that a total of 3.8% of CM-VA was transferred to mammary tissue. The model-predicted t(1/2) for CM remnants was 3.04 mins. The metabolism of CM-VA in the lactating mammary gland, in proportion to VA absorption and CM-VA contents, may explain how milk VA concentration varies even when plasma retinol levels are unchanged. The mechanism of CM margination and mammary gland uptake described here for VA may be similar for other lipophilic substances.

Physical activity in adolescence and young adulthood and breast cancer risk: a quantitative review

Physical activity habits are potentially modifiable and could therefore be targeted in a primary prevention strategy against breast cancer, provided there is causality and a sufficiently strong relationship. Our objective of this quantitative review was to provide a summary estimate of the association of moderate/vigorous recreational physical activity during adolescence/young adulthood with breast cancer risk, and to determine whether a dose-response relationship exists. Data sources included studies in humans relating physical activity to breast cancer risk, published between January 1966 and October 2002, identified on Medline, the Web of Science, from reference lists and related reviews. The main characteristics of each study, the point estimates of relative risk (RR) and confidence intervals (CI) were extracted from 19 case-control and four cohort studies. Comparing the highest to the lowest category of physical activity, the summary RR from the random effects model was 0.81 (95% CI 0.73-0.89). This almost 20% risk reduction proved to be fairly consistent, despite variation in populations and methods. Each one-hour increase of recreational physical activity/week during adolescence was associated with a 3% (95% CI 0-6%) risk reduction. Physical activity in 12-24-year-old females significantly reduces risk of breast cancer. Heterogeneity may be explained by different methods to measure activity.

Energetic factors and seasonal changes in ovarian function in women from rural Poland

Female mammals can optimize their fitness by temporal suppression of reproductive function in response to unfavorable environmental conditions. Since reproduction is energetically demanding for a human female, ovarian function is expected to be sensitive to factors influencing energy availability and metabolism. Dieting and exercise in women from industrial countries, and low-calorie diet and workload in women from developing countries, are often associated with ovarian suppression. This study shows that in Polish rural women seasonal changes in workload correlate with seasonal changes in indices of ovarian function (progesterone measured in saliva samples collected daily for six menstrual cycles for each subject). Mean levels of energy expenditure of the most work demanding weeks of the summer exceeded mean levels of energy expenditure during winter by 37%. Energy intake in this population was sufficient throughout the year. During the summer, when physical work was most intense, low values of progesterone levels were observed (178.2 pmol/L in July and 182.2 pmol/L in August), indicating ovarian suppression. Mean progesterone levels rose to 234.6 pmol/L in October when levels of energy expenditure were lower due to cessation of harvest-related activities. As indicated by several causal models tested through path analysis, energy expenditure was the only variable responsible for suppressed progesterone levels during the summer. Variables describing the nutritional status and energy balance did not correlate significantly with progesterone levels; neither body weight nor body fat or seasonal changes of these variables seem to influence ovarian function in this population. Thus work-related energy expenditure does not need to lead to negative energy balance in order to cause suppression of reproductive function in women.

Psychological stress and the risk of breast cancer: a case–control study

OBJECTIVE

To determine whether psychological stress, in the form of past life events and stress at work, was associated with the development of breast cancer.

METHODS

The study was based on a case-control study of 257 women with breast cancer operated during 1993-1998 in Szczecin (Poland) hospitals and 565 controls, free of any cancer diagnosis. The subjects were sent a detailed questionnaire including questions on sociodemographic data; lifestyle (lifetime recreational and sport activities, occupational physical activity, diet); reproductive history; experience of psychological stress. The subjects reported major stressful life events, stress of daily activity and experience of stress at work. Logistic regression analyses were used to estimate the odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

After adjustment for age and other potential confounders, we found that women with major life events, stress of daily activity, and depression had 3.7 times higher risk for breast cancer, compared to those which did not experience such stress (OR = 3.70; 95% CI, 2.61-5.26). Women who reported experience of stress at work had a nonsignificant 16% higher risk for breast cancer compared with those who reported no stress (OR = 1.16; 95% CI, 0.82-1.64). A higher proportion of cases (89.1%) than controls (71.1%) reported that their job was stressful, very fretful or very responsible or experienced a major life event (OR = 4.29; 95% CI, 2.66-6.92).

CONCLUSION

These findings suggest an association between major life events and breast cancer.

Association of CYP17, CYP19, CYP1B1, and COMT Polymorphisms with Serum and Urinary Sex Hormone Concentrations in Postmenopausal Women

Women with high circulating estrogen concentrations have an increased risk of breast cancer; thus, it is important to understand factors, including genetic variability, that influence estrogen concentrations. Several genetic polymorphisms that may influence sex hormone concentrations have been identified, including CYP17 (5'-untranslated region T-->C), CYP19 [intron 4 (TTTA)(n = 7-13) and a 3-bp deletion (-3)], CYP1B1 (Val(432)Leu), and COMT (Val(108/158)Met). We examined associations between these polymorphisms and serum concentrations of estrogens, androgens, and sex hormone-binding globulin and urinary concentrations of 2- and 16alpha-hydroxyestrone in 171 postmenopausal women, using data from the prerandomization visit of an exercise clinical trial. Participants were sedentary, not taking hormone therapy, and had a body mass index >24.0. Compared with noncarriers, women carrying two CYP19 7r(-3) alleles had 26% lower estrone (P < 0.001), 19% lower estradiol (P = 0.01), 23% lower free estradiol (P = 0.01), and 22% higher sex hormone-binding globulin concentrations (P = 0.06). Compared with noncarriers, women carrying at least one CYP19 8r allele had 20% higher estrone (P = 0.003), 18% higher estradiol (P = 0.02), and 21% higher free estradiol concentrations (P = 0.01). Women with the COMT Met/Met genotype had 28% higher 2-hydroxyestrone (P = 0.08) and 31% higher 16alpha-hydroxyestrone concentrations (P = 0.02), compared with Val/Val women. Few associations were found for CYP17 and CYP1B1 or with serum androgen concentrations. This study provides further evidence that genetic variation may appreciably alter sex hormone concentrations in postmenopausal women not taking hormone therapy.

Progesterone involvement in breast development and tumorigenesis--as revealed by progesterone receptor "knockout" and "knockin" mouse models

In light of recent clinical trials, the debate concerning the risks and benefits of progestin-based postmenopausal hormone replacement therapy (HRT) has reached a renewed level of urgency. Irrespective of the position taken, the consensus is that more basic research needs to be performed to address progesterone's fundamental role in mammary development and tumorigenesis. Towards this end, the progesterone receptor knockout (PRKO) mouse demonstrated that progesterone is essential for pregnancy-associated mammary gland ductal side-branching and alveologenesis and that these morphological changes are dependent on progesterone-induced mammary epithelial proliferation. Importantly, the PRKO mouse showed that the progesterone-proliferative signal significantly contributes to mammary tumor susceptibility in an established mammary tumor model. Insight into the cellular mechanism(s) by which progesterone affects mammary morphogenesis has been disclosed by a new PR-LacZ knockin mouse, which revealed that PR's spatial expression pattern undergoes precise choreographed distributional changes that precede key stages in postnatal mammary development. In the case of early pregnancy, the segregation of cells undergoing progesterone-induced proliferation from those that express PR implicates a paracrine mode of action for progesterone-induced mammary epithelial proliferation, whereas the preparturient decline of PR expression underscores the need to remove this signal for full functional differentiation of this tissue. Our findings support the proposal that the mammary gland's normal response to the progesterone-signal is dependent upon specific spatial organizational patterns of PR expression and that derailment in these cellular processes may contribute to abnormal mammary development, including cancer. This review concludes by emphasizing the need to identify the downstream molecular targets that mediate progesterone's effects in this tissue. Identification of such targets will not only enhance our mechanistic understanding of progesterone's role in mammary development and cancer, but may also facilitate the formulation of new design strategies in breast cancer diagnosis and/or treatment.

Historical reconstruction of wastewater and land use impacts to groundwater used for public drinking water: exposure assessment using chemical data and GIS

Land use in geographic areas that replenish groundwater and surface water resources is increasingly recognized as an important factor affecting drinking water quality. Efforts to understand the implications for health, particularly outcomes with long latency or critical exposure windows, have been hampered by lack of historical exposure data for unregulated pollutants. This limitation has hindered studies of the possible links between breast cancer risk and drinking water impacted by endocrine disrupting compounds and mammary carcinogens, for example. This paper describes a methodology to assess potential historical exposure to a broad range of chemicals associated with wastewater and land use impacts to 132 groundwater wells and one surface water body supplying drinking water to 18 public distribution systems on Cape Cod, MA. We calculated annual measures of impact to each distribution system and used the measures as exposure estimates for the residential addresses of control women in the Cape Cod Breast Cancer and Environment Study (Cape Cod Study). Impact was assessed using (1) historical chemical measurements of nitrate at the water supply sources (performed as required by the Safe Water Drinking Act) and (2) a geographic information system analysis of land use within the zones of contribution (ZOCs) delineated for each well in a state-mandated wellhead protection program. The period for which these impact estimates were developed (1972-1995) was constrained by the availability of chemical measurements and land use data and consideration of time required for groundwater transport of contaminants to the water supply wells. Trends in these estimates for Cape Cod suggest increasing impact to drinking water quality for land use over the study period. Sensitivity analyses were conducted to assess the effect on the distribution of controls' cumulative exposure estimates from (1) reducing the area of the ZOCs to reflect typical well operating conditions rather than extreme pumping conditions used for the regulatory ZOCs, (2) assuming residences received their drinking water entirely from the closest well or cluster of wells rather than a volume-weighted annual district-wide average, and (3) changing the travel time considered for contaminants to reach wells from land use sources. We found that the rank and distribution of controls' cumulative exposure estimates were affected most by the assumption concerning district mixing; in particular, assignment of exposure estimates based on impact values for the closest well(s) consistently produced a larger number of unexposed controls than when a district-wide average impact value was used. As expected, the results suggest that adequate characterization of water quality heterogeneity within water supplies is an important component of exposure assessment methodologies in health studies investigating impacted drinking water.

Diet and breast cancer: can dietary factors influence survival?

Breast cancer accounts for over one third of invasive cancers in women. Earlier detection and improved initial treatments have resulted in an increasing number of women who have completed standard treatments but who remain at risk for breast cancer recurrence or early death. Epidemiological studies have linked diet composition with prognosis, and many women attempt to modify their diets and improve nutritional status following diagnosis The hypothesis that dietary factors may reduce risk for secondary cancer events and increase survival in this population is currently under study in two large randomized clinical trials: the Women's Intervention Nutrition Study (WINS) and the Women's Healthy Eating and Living (WHEL) Study. The WHEL Study is testing the effect of a diet high in vegetables, fruit, and fiber, and low in fat, on disease-free survival in women with early stage breast cancer. Hypothesized mechanisms include effects of diet modification on gonadal hormones, retinoid-like activities of carotenoids, and other protective effects of biologically active dietary constituents.