Studies of dehydroepiandrosterone (DHEA) with the human estrogen receptor in yeast.

Dehydroepiandrosterone (DHEA) is a C19 adrenal steroid synthesized in the human adrenal cortex and serving as a biosynthetic precursor to testosterone and 17beta-estradiol. Despite the fact that it is one of the most abundant steroid hormones in circulation, the physiological role of DHEA in humans remains unclear. The action of DHEA itself, such as its interactions with receptors and nuclear transcription factors, is not well understood, and a specific DHEA receptor has yet to be identified. Although the activity of DHEA can be due to its metabolism into androgens and estrogens, DHEA has been shown to interact with the androgen receptor and the estrogen receptor (ER) in vitro. We demonstrate in this study that DHEA (3beta-Hydroxy-5alpha-androstan-17-one) inhibits 17beta-estradiol (E2) binding to its receptor in vivo in yeast. DHEA stimulates human ER dimerization in yeast, as determined by ER fusion protein interactions, GAL4 reconstitution and subsequent measurement of increased beta-galactosidase activity. DHEA causes an increase in estrogen response element-dependent beta-galactosidase activity, demonstrating that the ER dimer induced by DHEA is transcriptionally active, but at a concentration of DHEA about 1000 times greater than E2. Inclusion of the nuclear receptor co-activator RIP140 in the yeast enhances ER transactivation by DHEA or E2 in a ligand-dependent manner; moreover, only in the presence of RIP140 is DHEA able to stimulate beta-galactosidase activity to levels similar to those achieved by E2. Ligand-receptor interaction for other C19-steroids was also examined. While 5-androstene-3beta, 17beta-diol (ADIOL) displayed estrogenic activity in this system, 4-androstene-17-dione (androstenedione) and 4-androstene-17beta-ol,3-one (testosterone) did not. We have investigated whether DHEA can interact with the human ER in vivo. Our findings demonstrate a mechanism by which DHEA interacts directly with estrogen signaling systems; however, because DHEA is several orders of magnitude less potent than E2 in this system, we conclude that it essentially is not an estrogen agonist.

Strategies for identification and clinical evaluation of promising chemopreventive agents.

Strategies for chemopreventative drug development are based on the use of well-characterized agents, intermediate biomarkers correlating to cancer incidence, and suitable cohorts for efficacy studies. Since chemoprevention is applied over the long-term, chemopreventive drugs must have low toxicity. Strategies for enhancing chemopreventive drug efficacy and minimizing toxicity include combinations of drugs with complementary mechanisms and/or synergistic activity; coadministration of drugs to counter the toxicity of the chemopreventive agents; and pursuit of related compounds that retain efficacy with reduced side effects. Because of its slow development, cancer is not a feasible end point for clinical evaluation of chemoprevention, and so intermediate biomarkers that can serve as surrogate end points are crucial. Particularly important biomarkers are the morphometric and cytometric changes defining intraepithelial neoplasia (IEN). Cohorts for chemoprevention trials should have high incidences of the cancer or intermediate biomarker(s) under study within the trial duration.

Factors associated with surgical and radiation therapy for early stage breast cancer in older women.

BACKGROUND: In addition to demographic and health care-related characteristics, the age and physiologic status of women at the time of breast cancer diagnosis have been reported to influence receipt of standard treatments. Previous studies of the influence of age and comorbidity have not examined whether other patient-, region-, or health care-related characteristics altered the association of age and comorbidity with type of treatment received. PURPOSE: This study examined factors associated with receipt of breast-conserving surgery and radiation therapy, both of which are recommended treatments for breast cancer, among a cohort of 18,704 women aged 65 years or more who had breast cancer diagnosed during the period from 1985 through 1989. METHODS: A data file linking Medicare claims records to data from the Surveillance, Epidemiology, and End Results (SEER) Program of the U.S. National Cancer Institute was utilized. Logistic regression analysis was used to examine associations between patient, region, and hospital characteristics and the receipt of specific treatments. The likelihood test was used to assess the significance of observed associations (expressed as odds ratios [ORs]). Because of multiple comparisons, only those ORs with two-sided P values <.01 were considered statistically significant. RESULTS: The frequency of breast-conserving surgery was highest (54%) among women aged 80 years or more, who had two or more comorbid conditions and stage I disease. However, in general, the receipt of radiation therapy among women undergoing breast-conserving surgery declined markedly with age, irrespective of comorbidity status and disease stage. Between the ages of 65-69 years and 80 years or older, radiation therapy declined from 77% to 24% among women with no comorbid conditions and from 50% to 12% among women with two or more comorbid conditions. In regression models that included hospital, region, and patient characteristics as variables, age and comorbidity remained independently associated with the receipt of radiation therapy (OR = 0.12 and 95% confidence interval [CI] = 0.10-0.14 for women aged 80 years or more compared with women 65-69 years of age and OR of 0.33 [95% CI = 0.24-0.46] for women with two or more comorbid conditions versus no comorbid conditions). CONCLUSIONS: After adjustment for multiple clinical and nonclinical factors influencing treatment, chronologic age remains an important independent factor associated with the receipt of radiation therapy after breast-conserving surgery among women aged 65 years or more who were diagnosed with early stage breast cancer. IMPLICATIONS: Future studies should determine whether these differences in treatment patterns among older women result in increased morbidity (e.g., from recurrence), shortened disease-free or overall survival, or decreased quality of life.

Tamoxifen-associated eye disease. A review.

PURPOSE: The oral antiestrogen tamoxifen has demonstrated efficacy in the treatment of metastatic breast cancer and as adjuvant therapy in early-stage disease. Clinical trials of tamoxifen in chemoprevention of breast cancer among high-risk women have focused attention on potential adverse effects of long-term tamoxifen use, including the possibility of ocular toxicity. This review evaluates the published case reports, clinical series, and clinical trial data on ocular toxicities attributed to tamoxifen. Clinical issues of surveillance, differential diagnosis, and management of tamoxifen-related eye disease are discussed. DESIGN: National Library of Medicine online bibliographic services were used to identify case reports and clinical studies of ocular adverse effects that occurred in patients receiving tamoxifen published through the fall of 1994. The medical literature relevant to issues raised by the reports and studies was similarly identified and reviewed. RESULTS: Case reports and case series identify crystalline retinal deposits, macular edema, and corneal changes as potential tamoxifen ocular toxicities. Extensive retinal lesions and macular edema with visual impairment have been reported in a few patients receiving high-dose tamoxifen. Less extensive retinal changes may occur in patients receiving low doses for long periods, and isolated retinal crystals may be observed in patients without visual symptoms. CONCLUSION: Ocular toxicity is uncommon in the current clinical setting of long-term, low-dose tamoxifen use. Physicians should be aware of the potential for ocular toxicity among patients receiving the drug and should assure appropriate surveillance and prompt evaluation of visual complaints.

Risk biomarkers and current strategies for cancer chemoprevention.

Quantifiable, well-characterized cancer risk factors demonstrate the need for chemoprevention and define cohorts for chemopreventive intervention. For chemoprevention, the important cancer risk factors are those that can be measured quantitatively in the subject at risk. These factors, called risk biomarkers, can be used to identify cohorts for chemoprevention. Those modulated by chemopreventive agents may also be used as endpoints in chemoprevention studies. Generally, the risk biomarkers fit into categories based on those previously defined by Hulka: 1) carcinogen exposure, 2) carcinogen exposure/effect, 3) genetic predisposition, 4) intermediate biomarkers of cancer, and 5) previous cancers. Besides their use in characterizing cohorts for chemoprevention trials, some risk biomarkers can be modulated by chemopreventive agents. These biomarkers may be suitable surrogate endpoints for cancer incidence in chemoprevention intervention trials. The criteria for risk biomarkers defining cohorts and serving as endpoints are the same, except that those defining cohorts are not necessarily modulated by chemopreventive agents. A primary criterion is that the biomarkers fit expected biological mechanisms of early carcinogenesis-i.e., differential expression in normal and high-risk tissue, on or closely linked to the causal pathway for the cancer, and short latency compared with cancer. They must occur in sufficient number to allow their biological and statistical evaluation. Further, the biomarkers should be assayed reliably and quantitatively, measured easily, and correlated to cancer incidence. Particularly important for cancer risk screening in normal subjects is the ability to use noninvasive techniques that are highly specific, sensitive, and quantitative. Since carcinogenesis is a multipath process, single biomarkers are difficult to correlate to cancer, as they may appear on only one or a few of the many possible causal pathways. As shown in colorectal carcinogenesis, the risks associated with the presence of biomarkers may be additive or synergistic. That is, the accumulation of genetic lesions is the more important determinant of colorectal cancer compared with the presence of any single lesion. Thus, batteries of biomarker abnormalities, particularly those representing the range of carcinogenesis pathways, may prove more useful than single biomarkers both in characterizing cohorts at risk and defining modulatable risks. Risk biomarkers are already being integrated into many chemoprevention intervention trials. One example is the phase II trial of oltipraz inhibition of carcinogen-DNA adducts in a Chinese population exposed to aflatoxin B1. Also, urine samples from subjects in this trial will be screened for the effect of oltipraz on urinary mutagens. A second example is a chemoprevention protocol developed for patients at high risk for breast cancer; the cohort is defined both by hereditary risk and the presence of biomarker abnormalities. Modulation of the biomarker abnormalities is a proposed endpoint. Also, dysplastic lesions, such as prostatic intraepithelial neoplasia, oral leukoplakia and colorectal adenomas, have been used to define high-risk cohorts and as potential modulatable surrogate endpoints in chemoprevention trials.

Ethical and scientific considerations for chemoprevention research in cohorts at genetic risk for breast cancer.

Identification of cohorts at genetic risk for cancer offers unique research opportunities to explore the steps in carcinogenesis, from the inheritance of a predisposing mutation to the development of preinvasive lesions or overt malignancy, and to evaluate interventions to modulate the carcinogenic process. However, cancer prevention strategies for most inherited cancer predisposition syndromes are of unproven benefit, and the potential for adverse psychosocial effects and employment or insurance discrimination associated with genetic testing is substantial. Thus testing for genetic cancer risk remains highly controversial, and the National Center for Human Genome Research and the American Society of Human Genetics advise DNA testing for presymptomatic identification of cancer risk only in the setting of a carefully monitored research environment. The commercial availability of predictive genetic testing, particularly for inherited susceptibility to cancer, has focused attention not only on the urgent need for research in cancer prevention for cohorts at genetic cancer risk but also on ethical considerations surrounding clinical prevention research in genetic risk groups. This paper addresses the interrelationship of ethical and scientific issues in conducting chemoprevention research in these cohorts, especially for those studies which require presymptomatic testing for specific gene mutations as a study entry criterion or as a criterion for stratification. Practical approaches to study design and implementation issues for chemoprevention research in genetic risk cohorts are discussed, emphasizing the interactions of ethical and scientific considerations at all levels of the research process.

Strategy and planning for chemopreventive drug development: clinical development plans II.

This is the second publication of Clinical Development Plans from the National Cancer Institute, Division of Cancer Prevention and Control, Chemoprevention Branch and Agent Development Committee. The Clinical Development Plans summarize the status of promising chemopreventive agents regarding evidence for safety and chemopreventive efficacy in preclinical and clinical studies. They also contain the strategy for further development of these drugs, addressing pharmacodynamics, drug effect measurements, intermediate biomarkers for monitoring efficacy, toxicity, supply and formulation, regulatory approval, and proposed clinical trials. Sixteen new Clinical Development Plans are presented here: curcumin, dehydroepiandrosterone, folic acid, genistein, indole-3-carbinol, perillyl alcohol, phenethyl isothiocyanate, 9-cis-retinoic acid, 13-cis-retinoic acid, l-selenomethionine and 1, 4-phenylenebis(methylene)selenocyanate, sulindac sulfone, tea, ursodiol, vitamin A, and (+)-vorozole. The objective of publishing these plans is to stimulate interest and thinking among the scientific community on the prospects for developing these and future generations of chemopreventive drugs.

Strategies for phase II cancer chemoprevention trials: cervix, endometrium, and ovary.

Well-designed and conducted Phase II clinical trials are very important to cancer chemoprevention drug development. Three critical aspects govern the design and conduct of these trials--well-characterized agents, suitable cohorts, and reliable biomarkers for measuring efficacy that can serve as surrogate endpoints for cancer incidence. Requirements for the agent are experimental or epidemiological data showing chemopreventive efficacy, safety on chronic administration, and a mechanistic rationale for the chemopreventive activity observed. Agents that meet these criteria for chemoprevention of cervical cancer include antiproliferative drugs (e.g., 2-difluoromethylornithine), retinoids, folic acid, antioxidant vitamins and other agents that prevent cellular oxidative damage. Because of the significant cervical cancer risk associated with human papilloma virus (HPV) infection, agents that interfere with the activity of HPV products may also prove to be effective chemopreventives. In endometrium, unopposed estrogen exposure has been associated with cancer incidence. Thus, pure antiestrogens and progestins may be chemopreventive in this tissue. Ovarian cancer risk is correlated to ovulation frequency; therefore, oral contraceptives are potentially chemopreventive in the ovary. Recent clinical observations also suggest that retinoids, particularly all-trans-N-4-hydroxyphenylretinamide, may be chemopreventive in this tissue. The cohort should be suitable for measuring the chemopreventive activity of the agent and the intermediate biomarkers chosen. In the cervix, patients with cervical intraepithelial neoplasia (CIN) and in endometrium, patients with atypical hyperplasia, fit these criteria. Defining a cohort for a Phase II trial in the ovary is more difficult. This tissue is less accessible for biopsy; consequently, the presence of precancerous lesions is more difficult to confirm. The criteria for biomarkers are that they fit expected biological mechanisms (i.e., differential expression in normal and high-risk tissue, on or closely linked to the causal pathway for the cancer, modulated by chemopreventive agents, and short latency compared with cancer), may be assayed reliably and quantitatively, measured easily, and correlate to decrease cancer incidence. They must occur in sufficient incidence to allow their biological and statistical evaluation relevant to cancer. Since carcinogenesis is a multipath process, single biomarkers are difficult to validate as surrogate endpoints, perhaps appearing on only one or a few of the many possible causal pathways. Panels of biomarkers, particularly those representing the range of carcinogenesis pathways, may prove more useful as surrogate endpoints. It is important to avoid solely on biomarkers that do not describe cancer but represent isolated events that may or may not be on the causal pathway or otherwise associated with carcinogenesis. These include markers of normal cellular processes that may be increased or expressed during carcinogenesis. Chemoprevention trials should be designed to evaluate fully the two or three biomarkers that appear to be the best models of the cancer. Additional biomarkers should be considered only if they can be analyzed efficiently and the sample size allows more important biomarkers to be evaluated completely. Two types of biomarkers that stand out regarding their high correlation to cancer and their ability to be quantified are measures of intraepithelial neoplasia and indicators of cellular proliferation. Measurements made by computer-assisted image analysis that are potentially useful as surrogate endpoint biomarkers include nuclear polymorphism comprising nuclear size, shape (roundness), and texture (DNA distribution patterns); nucleolar size and number of nucleoli/nuclei; DNA ploidy, and proliferation biomarkers such as S-phase fraction and PCNA...

Tamoxifen's role in chemoprevention of breast cancer: an update.

Tamoxifen is an oral antiestrogen first used in metastatic breast cancer in the early 1970s. Large clinical trials were initiated in the late 1970s and early 1980s to test the drug's role as adjuvant therapy in early stage breast cancer. Observations of marked decreases in the development of contralateral breast cancer among tamoxifen recipients suggested potential for the drug in chemoprevention of breast cancer, and a large clinical trial to test the efficacy of tamoxifen in prevention of invasive breast cancer among women at increased risk was implemented in the United States in 1992. This paper reviews the rational for the clinical studies of tamoxifen as a chemopreventive agent for breast cancer and summarizes new information that has contributed to our understanding of tamoxifen's actions at the molecular and clinical levels. Current knowledge about the drug's mechanism of estrogenic and antiestrogenic action and its beneficial effects on blood lipids and bone metabolism will be presented. Recent research findings about DNA adduct formation and hepatic lesions, tamoxifen-associated gynecologic conditions, and the occurrence of second primary cancers in other organ systems will also be discussed.

The potential for hormonal prevention trials.

Breast and prostate cancer are significant causes of morbidity and mortality and are very similar in etiology, epidemiology, and modalities of treatment. Investigational strategies in the prevention of these malignancies also have strong parallels. The National Cancer Institute is sponsoring several large scale clinical trials involving hormonal manipulation and cancer prevention. In the Breast Cancer Prevention Trial, 16,000 women at high risk for breast cancer are being randomized to receive the antiestrogen agent tamoxifen or placebo for 5 years in an effort to determine if breast cancer development can be inhibited. In a similar trial, the Prostate Cancer Prevention Trial, 18,000 men older than 55 years of age will be randomized to receive finasteride, a 5-alpha-reductase inhibitor, or placebo to determine if inhibition of dihydrotestosterone synthesis in the prostate over a prolonged period will lead to a decreased incidence of prostate cancer. Both clinical trials offer the possibility of demonstrating that a hormonal intervention can decrease an individual's risk of developing breast or prostate cancer. They also have the potential of providing critical information about cancer risk, etiology, screening, and genetics, as well as quantifying the risks and benefits of specific preventive interventions.

Effect of a National Cancer Institute Clinical Alert on breast cancer practice patterns.

PURPOSE: This study evaluates the effect of the 1988 National Cancer Institute Clinical Alert regarding treatment of early-stage breast cancer on the patterns of treatment provided to patients. PATIENTS AND METHODS: Data analyzed were collected from the hospital and outpatient records of 12,534 female patients with a primary diagnosis of breast cancer (stages I and II) initially diagnosed during the years 1983 through 1989. RESULTS: Analyses revealed that the proportions of patients with a negative lymph node status diagnosed after the May 1988 Clinical Alert who received adjuvant treatment (tamoxifen and/or multidrug chemotherapy) were significantly greater than predicted from treatment trends established before the Alert's release. Proportions of patients with positive lymph node status receiving adjuvant therapy subsequent to the Alert's release, in contrast, did not fall outside the projected confidence intervals for that group. Additional analyses showed a significant effect of the Clinical Alert among several subgroups of node-negative patients. CONCLUSION: Findings suggest that the Clinical Alert mechanism, followed by publication in the peer-reviewed scientific literature, is an effective way to communicate important research findings to practitioners in the community. However, the Alert mechanism is controversial and should be used judiciously to ensure its credibility.

Statutory requirements for disclosure of breast cancer treatment alternatives.

Therapeutic options for breast cancer, particularly for early-stage disease, and increased patient participation in medical decision-making have oriented state legislatures toward ensuring that women with breast cancer have adequate information about treatment alternatives. Currently, 18 states have enacted statutes regarding physician disclosure of treatment alternatives to breast cancer patients. This paper reviews these statutes in the context of the requirements imposed on the physician as health care provider and the content of medical information presented to the patient as a consequence of the laws. State statutes were identified through the National Cancer Institute's State Cancer Legislative Database, and the statutory requirements were analyzed. For statutes requiring development of a written summary of treatment alternatives, the most recent summary was obtained through the responsible state agency, and informational content was analyzed for relevance to treatment decisions in early-stage disease. As a group, these laws address informed consent for treatment, physician behavior within the patient-physician relationship, and the medical information upon which treatment decisions are based. Individual statutes vary in the scope of the issues addressed, particularly in the responsibility placed on physicians, and treatment option summaries developed in response to this legislation vary widely in content and scope. Despite broad implications of these statutes in oncology practice, little is known about their effects on breast cancer care. Additional research is needed to define the impact of these statutes on breast cancer care, as such legislation is considered by other states for this and other diseases.

Adjuvant therapy for stage III colon cancer: economics returns to research and cost-effectiveness of treatment.

BACKGROUND: In 1989, the National Cancer Institute issued a clinical announcement advising physicians of the benefits of combined levamisole and fluorouracil as an adjuvant treatment for patients with stage III colon cancer. PURPOSE: We have estimated the cost-effectiveness of the combined treatment and estimated the social return on the National Institutes of Health (NIH) research investment that led to this innovative cancer treatment. METHODS: A computer simulation model, CAN*TROL, was used to estimate costs and benefits for a population cross-section receiving the adjuvant treatment. A method similar to "Q-TWiST" was used to assess the impact of quality-of-life adjustments. RESULTS: For a typical base-line case, the calculated cost-effectiveness is a very favorable $2094 per year of life saved. Using a variety of less favorable assumptions, cost-effectiveness is still less than $5000 per year of life saved, again a favorable value. Quality-of-life adjustments have a negligible effect on the cost-effectiveness outcome. The net present value of the return to the NIH research investment is estimated to be $1.66 billion. CONCLUSIONS: Under a wide range of reasonable assumptions, adjuvant therapy for stage III colon cancer appears to be a very cost-effective procedure. The investment in the research that resulted in this therapy promises to yield a high return.

After a treatment breakthrough: a comparison of trial and population-based data for advanced testicular cancer.

PURPOSE: To determine to what extent the benefits of cisplatin-based combination chemotherapy have been disseminated to all American men diagnosed with advanced testicular cancer. PATIENTS AND METHODS: One hundred seventy-two advanced testicular cancer cases from five population-based registries of the Surveillance, Epidemiology, and End Results (SEER) Program diagnosed from 1978 to 1984 were compared with 133 diagnostically comparable cases from the Memorial Sloan-Kettering Cancer Center (MSKCC) vinblastine, dactinomycin, and bleomycin (VAB) regimens 7 through 9. Exclusions were made in both series for cases with elevated markers only, abdominal disease only, or extragonadal tumors. Ratings of extent of disease using the Indiana University system (minimal/moderate or advanced) were available for the MSKCC cases, and were determined retrospectively on the SEER cases based on information abstracted from medical records. RESULTS: Among the SEER cases, 89% reported receiving chemotherapy, and 95% of these received cisplatin-containing regimens. Survival among the MSKCC patients was significantly better than for the SEER cases in the minimal/moderate extent of disease category (95% and 73% 3-year survival rate, respectively); however, the difference for advanced cases was only marginally significant (52% and 40% 3-year survival rates, respectively). Survival did not vary significantly by year of diagnosis in either series. CONCLUSION: Although most of the patients in the SEER series received cisplatin-based chemotherapy, this alone did not produce results equivalent to that in the MSKCC series. Since the patients were selected to be as diagnostically comparable as possible at baseline, remaining differences in survival may be due to adherence to a fixed regimen and level of dose-intensity, adequacy of diagnostic work-up, implementation of salvage therapies and debulking surgery, and unknown factors related to who is willing and able to travel to a tertiary care center for treatment. Whatever the reason for not achieving optimal results in the SEER series, the very modest survival improvements over the time period 1978 to 1984 indicates that the differences in outcome between the two series were basically stable over the study period.

Report from a National Cancer Institute (USA) workshop on quality of life assessment in cancer clinical trials.

To promote the inclusion of quality of life (QOL) end-points in clinical research on cancer, the National Cancer Institute (USA) sponsored a workshop on QOL assessment in cancer clinical trials in July, 1990. Experts in clinical trials and QOL research formed four working groups to identify current areas of cancer treatment in which QOL end-points are most important; to discuss methodologic problems in QOL assessment; to address common problems in implementing clinical studies with QOL end-points; and to consider statistical issues in design, implementation, and data analysis. Recommendations made by the working groups are summarized in this paper.

Potential role of tamoxifen in prevention of breast cancer.

Despite advances in early detection and treatment of breast cancer, primary prevention has not been well explored, especially for women at increased risk of disease due to reproductive factors and family history. There are, however, suggestions that primary prevention of breast cancer may be a realistic objective. Randomized clinical trials of adjuvant therapy for early-stage breast cancer have demonstrated a 35% decrease in contralateral breast cancers among women receiving tamoxifen compared with controls, suggesting a potential role for tamoxifen in chemoprevention of breast cancer in women at increased risk of the disease. Adjuvant therapy studies also demonstrate that tamoxifen is well tolerated by most patients and suggest additional health benefits from alterations in plasma lipid levels and stabilization of bone mineral loss in women receiving tamoxifen. Aspects of tamoxifen pharmacology, laboratory research, and clinical experience which support its investigation as a chemopreventive agent for breast cancer are summarized, and potential toxic effects are discussed.

Gastrointestinal effects of acute ferrous sulfate poisoning in rats.

Ferrous sulfate administered intragastrically to rats produced two types of intestinal lesions: corrosive injury to the stomach and upper part of the small intestine, and ileal infarcts associated with venous thrombosis in some animals given fatal doses. Iron was deposited at the interface of viable and necrotic mucosa and in blood vessels of all layers. By means of electron microscopy the iron deposits were located in the basement membrane of the vessels. Fatal doses were always associated with intestinal injury, although the time of death suggests that death was caused by absorption of iron rather than by the local injury.