A candidate gene approach to searching for low-penetrance breast and prostate cancer genes.

Most cases of breast and prostate cancer are not associated with mutations in known high-penetrance genes, indicating the involvement of multiple low-penetrance risk alleles. Studies that have attempted to identify these genes have met with limited success. The National Cancer Institute Breast and Prostate Cancer Cohort Consortium--a pooled analysis of multiple large cohort studies with a total of more than 5,000 cases of breast cancer and 8,000 cases of prostate cancer--was therefore initiated. The goal of this consortium is to characterize variations in approximately 50 genes that mediate two pathways that are associated with these cancers--the steroid-hormone metabolism pathway and the insulin-like growth factor signalling pathway--and to associate these variations with cancer risk.

A polymorphism in the CYP17 gene increases the risk of breast cancer.

We conducted a case-control study to determine whether a polymorphism in the CYP17 gene was associated with risk of breast cancer. We found an increased risk of advanced breast cancer in women carrying an A2 allele. The odds ratio was 2.5 [95% confidence interval (CI), 1.07-5.94] for regional or metastatic disease. Among controls, the A1/A1 genotype was associated with a later age at menarche. The reduced risk of breast cancer associated with a later age of menarche was largely limited to A1/A1 women: odds ratio, 0.47 (CI, 0.22-0.98) for breast cancer and later age at menarche among A1 homozygotes compared with 0.80 (CI, 0.51-1.27) for A1/A2 and A2/A2 genotypes. These findings suggest that the CYP17 genotype may be a biomarker for the onset of ovulation and advanced breast cancer risk.

Building a multigenic model of breast cancer susceptibility: CYP17 and HSD17B1 are two important candidates.

We conducted a nested case-control study to evaluate whether polymorphisms in two genes involved in estrogen metabolism, CYP17 and HSD17B1, were useful in developing a breast cancer risk model that could help discriminate women who are at higher risk of breast cancer. If polymorphisms in these genes affect the level of circulating estrogens, they may directly influence breast cancer risk. The base population for this study is a multiethnic cohort study that includes African-American, Non-Latina White, Japanese, Latina, and Native Hawaiian women. For this analysis, 1508 randomly selected controls and 850 incident breast cancer cases of the first four ethnic groups who agreed to provide a blood specimen were included (76 and 80% response rates, respectively). The CYP17 A2 allele and the HSD17B1 A allele were considered "high-risk" alleles. Subjects were then classified according to number of high-risk alleles. After adjusting for age, weight, and ethnicity, we found that carrying one or more high-risk alleles increases the risk of advanced breast cancer in a dose-response fashion. The risk among women carrying four high-risk alleles was 2.21 [95% confidence interval (CI), 0.98-5.00; P for trend = 0.03] compared with those who carried none. This risk was largely limited to women who were not taking hormone replacement therapy (relative risk, 2.60; 95% CI, 0.95-7.14) and was most pronounced among those weighing 170 pounds or less (RR, 3.05; 95% CI, 1.29-7.25). These findings suggest that breast cancer risk has a strong genetic component and supports the theory that the underlying mechanism of "complex traits" can be understood using a multigenic model of candidate genes.

Cytochrome P450c17alpha gene (CYP17) polymorphism predicts use of hormone replacement therapy.

We investigated whether a polymorphism in the cytochrome P450c17alpha gene (CYP17), which is associated with higher endogenous hormone levels, influences the use of hormone replacement therapy (HRT). The study included 749 postmenopausal women ages 44-75 years at baseline randomly selected from a larger multiethnic cohort. African-American, Japanese, Latina, and white women were included in the study. Women who carry the CYP17 A2/A2 genotype were about half as likely as women with the A1/A1 genotype to be current HRT users (odds ratio = 0.52; 95% confidence interval, 0.31-0.86). This association was present in all four racial/ethnic groups and for women above and below the median weight of 150 pounds. These findings suggest that the actual risk of breast cancer associated with HRT use may be higher than previously reported.

Cytochrome P450c17alpha gene (CYP17) polymorphism is associated with serum estrogen and progesterone concentrations.

An increased level of serum estrogen is one marker of breast cancer risk. We have recently reported that increased risk of advanced breast cancer is associated with a common allele of the cytochrome P450c17alpha gene (CYP17), designated A2. We now show that CYP17 genotype is associated with serum hormone levels among 83 young, nulliparous women. Serum estradiol (E2) levels measured around day 11 of the menstrual cycle were 11 and 57% higher (P = 0.04), respectively, among women hetero- and homozygous for the CYP17 A2 allele compared to A1/A1 women. Similarly, around cycle day 22, E2 levels were 7 and 28% higher (P = 0.06), and progesterone levels were 24 and 30% higher (P = 0.04), respectively. These data provide direct evidence of genetic control of serum hormone levels.

Risk of endometrial cancer and estrogen replacement therapy history by CYP17 genotype.

Common variants among genes coding for enzymes in sex steroid biosynthetic pathways may influence the risk of endometrial cancer. We examined the association between endometrial cancer risk and estrogen replacement therapy (ERT) by CYP17 genotype using 51 incident cases and 391 randomly selected controls from a multiethnic cohort in Hawaii and Los Angeles, California. The relative risk of endometrial cancer was calculated for ever use versus never use of ERT by CYP17 genotype (TT, TC, and CC). We found that women who reported ever taking ERT were more than twice as likely to develop endometrial cancer as women who never took ERT [odds ratio (OR), 2.24; 95% confidence interval (CI), 1.19-4.23]. Among these women, the risk of endometrial cancer was higher for women homozygous for the CYP17 T allele (OR, 4.10; 95% CI, 1.64-10.3), but not for women with the C allele (OR, 1.31; 95% CI, 0.53-3.21). These preliminary findings suggest that CYP17 or other variants in estrogen biosynthesis or metabolism pathways may be potential markers of endometrial cancer susceptibility due to ERT.

Declining cancer rates in the 1990s.

PURPOSE: To provide evidence of a substantial decline in cancer rates for the period 1991 through 1995 and characterize major risk factors that seem to be driving secular trends in cancer mortality and incidence. DESIGN: Incidence and mortality rates were calculated using national surveillance data collected through the Surveillance, Epidemiology, and End Results (SEER) program and the National Center for Health Statistics. RESULTS: All-sites cancer incidence and mortality fell in the period 1991 through 1995; this decline is largely attributable to decreases in the smoking-related cancers, especially lung cancer. Of the 20 leading incident cancers today, both incidence and mortality are decreasing among 11 sites for men and 12 for women. In men, the decline in mortality has been notable and is especially apparent for the smoking-related cancers, including those of the lung, oral cavity and pharynx, larynx, and, to a lesser extent, bladder. In women, all-sites mortality decreased only approximately 0.4% from 1991 through 1995. Three cancers continued to show substantial increases in mortality through 1995 for both men and women (liver, multiple myeloma, and non-Hodgkin's lymphoma), while incidence rates continued to climb for liver cancer, non-Hodgkin's lymphoma, and melanoma. CONCLUSION: Data from the SEER program on recent trends in cancer incidence and mortality show that cancer rates are generally on the decline, largely because of reductions in smoking-related cancers. A consistent increase in mortality rates due to liver cancer poses a new health care challenge, one that will require the development of an effective treatment for individuals currently infected with hepatitis C or B to prevent mortality rates from continuing to increase.

Determinants of DNA yield and quality from buccal cell samples collected with mouthwash.

Buccal cells are becoming an important source of genomic DNA in epidemiological studies, but little is known about the effect of different sampling conditions on DNA quality and yield. We used a mouthwash protocol to collect six daily buccal cell samples from 35 healthy volunteers. Twenty-four individuals (six men and 18 women) correctly completed the protocol and were included in paired analyses to determine whether "swish" time (30 s versus 60 s), toothbrushing before collection, or lag time between collection and DNA extraction (1 day versus 5, 10, or 30 days at room temperature) would affect sample quality and yield. Total DNA, human-specific DNA (hDNA), degradation of DNA, and ability to amplify by PCR were determined. hDNA yield did not significantly vary by "swish" time. However, toothbrushing 1 h before sample collection reduced the amount of hDNA by nearly 40% (34 microg versus 21 microg; P = 0.06). Median hDNA yields for samples that were held for 1, 5, 10, and 30 days before extraction were 32 microg (range, 4-196), 32 microg (2-194), 23 microg (3-80), and 21 microg (5-56), respectively. The 10- and 30-day samples had significantly less hDNA than those processed after 1 day (P = 0.01). PCR success rates for beta-globin gene fragments of length 268 bp, 536 bp, and 989 bp were 94% or better, and high molecular weight DNA (>23 kb) was found in all but one sample. These results suggest that buccal cells should be collected before brushing teeth and processed within 5 days of collection to maximize hDNA yield.

Coronary disease and stroke in patients with large-vessel peripheral arterial disease.

Previous reports have indicated an excess of mortality from coronary heart disease (CHD), cardiovascular disease (CVD), and all causes in subjects with large-vessel peripheral arterial disease (LV-PAD). However, there is little information available concerning the risk of nonfatal events (morbidity) in this patient group. In a population-based study of 67 patients with LV-PAD and 408 control subjects without this condition, nonfatal CHD and stroke, and total CVD events, morbidity and mortality were evaluated in both men and women. Those with LV-PAD had a 3-fold excess of CVD morbidity at baseline compared with control subjects of the same sex. However, the absolute CVD rates were greater in men than women. During the 10 years of follow-up, women with LV-PAD had more nonfatal CVD events than men, resulting in comparable overall morbidity rates. In logistic regression models adjusted for other CVD risk factors, total CVD morbidity and mortality combined with 2.5 times as great in men and 5 times as great in women with LV-PAD as in those without peripheral arterial disease. These results suggest that the total morbidity and mortality burden are dramatically increased in both men and women with LV-PAD.

IgE predicts future nonfatal myocardial infarction in men.

Established risk factors cannot explain all the variance in coronary heart disease (CHD). Immunoglobin E (IgE), a mediator of allergy, can affect platelets and arterial smooth muscle. We previously demonstrated a cross-sectional association between IgE and cardiovascular disease (CVD) in men. The present study evaluated this relationship prospectively in 278 men and 343 women followed for a mean of 8.9 years. There was an association between IgE and coronary disease in men, but not in women. There was no association for CVD, stroke, or all-cause mortality. The age-adjusted relative risk (RR) for coronary mortality in men with baseline IgE > or = 200 kU/L was 1.66 (p < or = 0.66), but for nonfatal myocardial infarction (MI) it was 6.46 (p < or = 0.01). This association was independent of smoking and other risk factors, and unrelated to allergy. Thus, elevated IgE was a strong independent prospective risk factor for nonfatal, but not fatal, MI in men.

T1 breast carcinoma in women 70 years of age and older may not require axillary lymph node dissection.

BACKGROUND: The current trend in breast cancer treatment is toward breast conservation and selective use of axillary lymph node dissection. Patient eligibility criteria for treatment without axillary dissection are evolving. METHODS: We retrospectively reviewed the tumor registry over a 10-year period at Naval Medical Center San Diego and included all women aged 70 and older with T1 breast carcinoma (n = 78). Data included tumor size, surgical therapy, post-operative therapy, recurrence, and survival. The women were divided into groups by the approach taken toward the axilla. RESULTS: No patient was given adjuvant chemotherapy. There were no axillary cancer recurrences in our patients. No statistically significant difference existed, regardless of the approach to the axilla, in recurrence or survival between groups. CONCLUSION: Axillary dissection in this population did not influence postoperative treatment, decrease recurrence, or improve survival. Our study suggests breast cancer treatment in this population should not include axillary dissection.

Comprehensive analysis of hormone and genetic variation in 36 genes related to steroid hormone metabolism in pre- and postmenopausal women from the breast and prostate cancer cohort consortium (BPC3).

CONTEXT: Sex steroids play a central role in breast cancer development. OBJECTIVE: This study aimed to relate polymorphic variants in 36 candidate genes in the sex steroid pathway to serum concentrations of sex steroid hormones and SHBG. DESIGN: Data on 700 genetic polymorphisms were combined with existing hormone assays and data on breast cancer incidence, within the European Prospective Investigation into Cancer and Nutrition (EPIC) and the Nurses' Health Study (NHS) cohorts; significant findings were reanalyzed in the Multiethnic Cohort (MEC). SETTING AND PARTICIPANTS: We analyzed data from a pooled sample of 3852 pre- and postmenopausal Caucasian women from EPIC and NHS and 454 postmenopausal women from MEC. MAIN OUTCOME MEASURES: Outcome measures were SHBG, testosterone, dehydroepiandrosterone (DHEAS), androstenedione, estrone (E1), and estradiol (E2) as well as breast cancer risk. RESULTS: Globally significant associations were found among pre- and postmenopausal women combined between levels of SHBG and the SHBG gene and between DHEAS and the FSHR and AKR1C3 genes. Among postmenopausal women, serum E1 and E2 were significantly associated with the genes CYP19 and FSHR, and E1 was associated with ESR1. None of the variants related to serum hormone levels showed any significant association with breast cancer risk. CONCLUSIONS: We confirmed associations between serum levels of SHBG and the SHBG gene and of E1 and E2 and the CYP19 and ESR1 genes. Novel associations were observed between FSHR and DHEAS, E1, and E2 and between AKR1C3 and DHEAS.

Future possibilities in the prevention of breast cancer: role of genetic variation in breast cancer prevention.

Risk factors for breast cancer are related to endogenous hormones and reproductive events. As such, traditional cancer prevention strategies are not easily applicable. Tamoxifen and other selective estrogen receptor modulators (SERMs) offer a new preventive strategy for some high-risk women, but have not yet been shown to be efficacious for all women. New tools to identify high-risk women are needed. One such tool is the development of a multigenic model of breast cancer susceptibility that can be used to screen women in order to identify those who carry a combination of alleles that puts them at significantly increased risk.

Hormonal carcinogenesis.

Hormone-related cancers, namely breast, endometrium, ovary, prostate, testis, thyroid and osteosarcoma, share a unique mechanism of carcinogenesis. Endogenous and exogenous hormones drive cell proliferation, and thus the opportunity for the accumulation of random genetic errors. The emergence of a malignant phenotype depends on a series of somatic mutations that occur during cell division, but the specific genes involved in progression of hormone-related cancers are currently unknown. In this review, the epidemiology of endometrial cancer and breast cancer are used to illustrate the paradigms of hormonal carcinogenesis. Then, new strategies for early detection and prevention of hormonal carcinogenesis are discussed. This includes developing polygenic models of cancer predisposition and the further development of safe and effective chemopreventives that block target sequence activity. We developed polygenic models for breast and prostate cancer after hypothesizing that functionally relevant sequence variants in genes involved in steroid hormone metabolism and transport would act together, and also interact with well-known hormonally related risk factors, to define a high-risk profile for cancer. A combination of genes each with minor variation in expressed activity could provide a degree of separation of risk that would be clinically useful as they could yield a large cumulative difference after several decades. The genes included in the breast cancer model are the 17beta-hydroxysteroid dehydrogenase 1 (HSD17B1) gene, the cytochrome P459c17alpha (CYP17) gene, the aromatase (CYP19) gene, and the estrogen receptor alpha (ER) gene. The prostate cancer model includes the androgen receptor gene (AR), steroid 5alpha-reductase type II (SRD5A2), CYP17 and the 3beta hydroxysteroid dehydrogenase (HSD3B2) gene. We present data from our multi-ethnic cohort to support these models.

The low HDL cholesterol/high triglyceride trait.

In 748 probands and 3,283 first-degree relatives from the Collaborative Lipid Research Clinics (LRC) Family Study, our specific aim was to examine the degree to which low (bottom decile) high density lipoprotein cholesterol (HDL-C, hypoalpha) and high (top decile) triglyceride (TG, hyperTG) levels occur conjointly (CT) and the extent to which these characteristics were shared within families. To control for family size and permit a comparison with the proband percentages, mean familial percentages of HDL-C/TG abnormalities were calculated. Concurrent low HDL-C and high TG levels were present in 2.7% of the probands, a value that was enriched to 12.7% (p = 0.003) of their associated first-degree relatives. If the proband had a low HDL-C value, 7.7% (p = 0.013) of relatives had CT. Familial (proband and at least one first-degree family member share the same lipoprotein/lipid phenotype) hypoalpha was observed in 2.4% of families while familial hyperTG was observed in 4.1%. Familial CT was seen in approximately 0.7%. If the proband had CT, 80% of their families had at least one other first-degree member with an HDL-C/TG abnormality, whereas the corresponding percentage for families associated with probands with only hypoalpha was 64% and for those with hyperTG alone, 54%. A broadly shared environmental factor cannot easily explain the familial association of hypoalpha, hyperTG, and CT. In probands with low HDL-C values alone or the conjoint low-HDL-C/high-TG trait, family screening is extremely valuable because low HDL-C/high TG is enriched in the respective family members, a conjoined trait closely associated with increased coronary heart disease risk.

Screening for peripheral arterial disease: the sensitivity, specificity, and predictive value of noninvasive tests in a defined population.

Large vessel peripheral arterial disease (LV-PAD) is a common condition that causes significant morbidity and disability. The authors evaluated the individual components of a comprehensive noninvasive vascular examination to identify the most sensitive and specific measurements for diagnosing LV-PAD. This cohort, initially screened between 1979 and 1981 in Rancho Bernardo, California, included 421 normal subjects and 63 subjects with LV-PAD. Segmental blood pressure ratios and flow velocities by Doppler ultrasound were used to define cases of LV-PAD. The sensitivity, specificity, positive predictive value, and negative predictive value of each individual component of the diagnostic algorithm were determined. Overall, measurements of posterior tibial flow showed the highest sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy. In addition, an absent or non-recordable posterior tibial peak forward flow, occurring in 96% of all limbs with isolated posterior tibial disease, or an ankle ratio < or = 0.8 considered in parallel yielded a test with sensitivity of 89%, specificity of 99%, positive predictive value of 90%, negative predictive value of 99%, and overall accuracy of 98%. These results indicate that the vast majority of LV-PAD cases can be detected with a single measurement using a handheld Doppler flowmeter employed at the ankle.

Use of prenatal services by Hispanic women in San Diego County. A comparison of urban and rural settings.

The purpose of this study was to investigate patterns of prenatal care use among urban and rural Hispanic women in San Diego County, California. A cohort study of Hispanic women delivering at one of five San Diego County hospitals between July 1991 and January 1992 was conducted (N = 587). Data were collected by in-person interview and medical record abstraction. Logistic regression was used to identify variables associated with late entry into prenatal care, while simultaneously adjusting for important confounding variables. Three factors were found to be significantly associated with late entry into prenatal care. Women who resided in urban areas were two times more likely to enter prenatal care late as compared to women who lived in rural areas (odds ratio = 2.11; 95% confidence intervals (CI) = 1.12, 4.0). Women who reported not having initially "wanted" the pregnancy were 2.2 times more likely to enter prenatal care late (95% CI = 1.05, 4.59). The risk of entering prenatal care late increased by 20% for each additional barrier to care that was reported (95% CI = 1.09, 1.34). Results indicate that timely entry into prenatal care may be improved among San Diego Hispanic women by targeting specific barriers to prenatal care identified in this study and by providing greater family planning assistance to this population to decrease unwanted pregnancies.

Genetic susceptibility to cancer from exogenous and endogenous exposures.

The past four decades of epidemiological research have yielded valuable information on the risks of populations to environmental exposures such as tobacco, asbestos, and dietary components. Prevention efforts have been focused on large-scale population-based interventions to minimize exposure to such external carcinogens. While some cancers are beginning to show a decline from changing environmental exposures, hormone-related cancers, such as breast and prostate, are becoming more prevalent. The development of these cancers appears to be closely related to endogenous exposures to circulating steroid hormones. Although prevention trials using antihormone agents are proving successful in some instances, the long-term control of these cancers necessitates a clearer understanding of the metabolism and transport of the relevant hormone in vivo. The revolution in molecular biology has provided powerful genetic tools for evaluating mechanisms of cancer causation as well as the potential to better define individual susceptibility. Using tobacco exposure as an example, we and others have demonstrated that polymorphisms in genes controlling aromatic amine metabolism provide at least a partial explanation for ethnic and individual susceptibility to bladder cancer. Similar studies have examined genetic polymorphisms in the metabolism of tobacco smoke and lung cancer risk, red meat and colorectal cancer, and aflatoxin and liver cancer. Our current studies have pursued a similar paradigm of genetic polymorphism and individual cancer susceptibility in prostate and breast carcinogenesis. We are evaluating polymorphisms in the steroid 5 alpha-reductase type II and androgen receptor genes in relation to prostate cancer based on the evidence that intracellular dihydrotestosterone is the critical "carcinogen." We are pursuing genetic polymorphisms affecting estradiol metabolism, including those in the 17 beta-hydroxysteroid dehydrogenase 2 and estrogen receptor genes as they relate to susceptibility to breast cancer. The potential role of a polymorphism in the cytochrome P450c 17 alpha gene in both breast and prostate cancers is also being examined.

Alcohol consumption increases the risk of fatal breast cancer (United States).

OBJECTIVE: To investigate the hypothesis that alcohol consumption increases the risk of breast cancer mortality. METHODS: We examined breast cancer mortality in relation to self-reported alcohol consumption in women from the American Cancer Society Cancer Prevention Study (CPS)-II. After 14 years of follow-up, 1,442 eligible breast cancer deaths were observed among 242,010 women. Cox proportional hazards models were constructed for total alcohol consumption and for beer, wine, and liquor separately. RESULTS: Total alcohol consumption was associated with increased risk of fatal breast cancer among post- but not pre- or perimenopausal women. Even less than one drink/day was associated with up to a 30% increase in breast cancer mortality among postmenopausal women compared to non-drinkers (RR = 1.3, 95% CI: 1.1-1.6 for women drinking 0.26-<1 drink/day). When examined separately, consumption of beer, wine, and liquor each increased the risk of breast cancer among postmenopausal women. We found no evidence that alcohol consumption was more deleterious among women at high risk for breast cancer compared to average-risk women. CONCLUSION: This study adds to the evidence that postmenopausal women can reduce their risk of breast cancer by avoiding or minimizing their use of alcohol.