Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The normal growth and development of the prostate requires the presence and action of androgens, which are also known risk factors in the origins of benign and malignant prostate disease. Paradoxically, the incidence of prostate disease increases with age when serum androgen levels are in decline and emerging evidence suggests that estrogens may also be important in the normal prostate, as well as in the etiology of prostate disease. Both estrogen receptor subtypes are present in the prostate, demonstrating that the gland responds directly to estrogens. Recent data suggests that estrogens play a role in prostate disease and has demonstrated that high doses of estrogens induce premalignant dysplasia and in combination with high doses of androgens, malignancy. The production of estrogens from androgens is mediated by the aromatase enzyme, the aberrant expression of which plays a critical role in the disease process in other tissues, most notably the breast. The prostate expresses aromatase within the stroma of benign tissue, while in malignancy there is an induction of epithelial expression with altered promoter utilisation. Although the presence of aromatase in the prostate and its aberrant expression in prostate cancer is significant, its role and contribution to prostate carcinogenesis remains unclear. Transgenic mouse models lacking aromatase (ArKO) and over-expressing aromatase (AROM+) have provided an ideal means to examine aromatase expression in the prostate. Studies using these animals may lead to a better understanding of the role that aromatase--and therefore estrogen--plays in the development and progression of prostate disease.
 ...
PMID:Aromatase and prostate cancer. 1649 60

Cytochrome P450 aromatase (aromatase), a product of the CYP19 gene, catalyzes the synthesis of estrogens from androgens. Given the significance of estrogen synthesis in hormone-dependent breast carcinogenesis, it is important to elucidate the mechanisms that regulate CYP19 expression. The main objective of this study was to define the interrelationship between HER-2/neu, cyclooxygenase-2 (COX-2), and aromatase in mammary tissue. Mammary aromatase activity and prostaglandin E(2) (PGE(2)) levels were increased in mice with mammary-targeted expression of a COX-2 transgene. In vitro, overexpressing COX-2 caused both increased PGE(2) production and aromatase activity, effects that were suppressed by celecoxib, a selective COX-2 inhibitor. Previously, we found that overexpression of HER-2/neu was associated with increased levels of COX-2 in human breast cancers. Here, we show that overexpression of HER-2/neu is also associated with increased aromatase activity. These results suggested the possibility that COX-2 was the functional intermediate linking HER-2/neu and aromatase. Consistent with this idea, COX-2 deficiency led to a gene dose-dependent reduction in mammary aromatase activity in a HER-2/neu transgenic mouse model. Complementary in vitro studies showed that HER-2/neu-mediated induction of PGE(2) synthesis and aromatase activity were suppressed by inhibiting COX-2. Collectively, our data indicate that COX-2 is the functional intermediate linking HER-2/neu and aromatase and suggest that inhibitors of PGE(2) synthesis will suppress estrogen biosynthesis in breast tissue.
 ...
PMID:HER-2/neu status is a determinant of mammary aromatase activity in vivo: evidence for a cyclooxygenase-2-dependent mechanism. 1670 80

Breast cancer is the most common cancer and the second most common cause of cancer death among women in the United States. While nonrandomized studies have reported that prophylactic mastectomy or oophorectomy can significantly reduce the risk of breast cancer, these approaches are unacceptable to the majority of women. Chemoprevention, which is defined as the prevention of cancer by pharmacological agents that inhibit or reverse the process of carcinogenesis, has thus increasingly become the focus of breast cancer prevention efforts. The first-generation selective estrogen receptor modulator (SERM) tamoxifen is the only US Food and Drug Administration- approved drug for breast cancer prevention and reduces the risk of breast cancer by as much as 50% in high-risk women. Raloxifene, a second-generation SERM, also has demonstrated efficacy for breast cancer prevention and is being compared with tamoxifen in a large randomized trial that has recently completed accrual. The aromatase inhibitors (AIs) decrease the incidence of contralateral breast cancer when used in the adjuvant setting and are being evaluated in ongoing primary prevention studies. In addition, a number of novel agents, including antiinflammatory drugs and retinoid derivatives, which appear to be of promise based on preclinical and epidemiological data, are under investigation. Several important challenges remain, including determination of the appropriate dose and duration of treatment when used in the primary prevention setting and development of new research models using surrogate end points for breast cancer incidence and mortality to permit more rapid clinical application of promising new agents.
 ...
PMID:Chemoprevention of breast cancer: tamoxifen, raloxifene, and beyond. 1685 70

Androgens are thought to cause prostate cancer, but there is little epidemiological support for this notion. Animal studies, however, demonstrate that androgens are very strong tumor promotors for prostate carcinogenesis after tumor-initiating events. Even treatment with low doses of testosterone alone can induce prostate cancer in rodents. Because testosterone can be converted to estradiol-17beta by the enzyme aromatase, expressed in human and rodent prostate, estrogen may be involved in prostate cancer induction by testosterone. When estradiol is added to testosterone treatment of rats, prostate cancer incidence is markedly increased and even a short course of estrogen treatment results in a high incidence of prostate cancer. The active testosterone metabolite 5alpha-dihydrotestosterone cannot be aromatized to estrogen and hardly induces prostate cancer, supporting a critical role of estrogen in prostate carcinogenesis. Estrogen receptors are expressed in the prostate and may mediate some or all of the effects of estrogen. However, there is also evidence that in the rodent and human prostate conversion occurs of estrogens to catecholestrogens. These can be converted to reactive intermediates that can adduct to DNA and cause generation of reactive oxygen species, and thus estradiol can be a weak DNA damaging (genotoxic) carcinogen. In the rat prostate DNA damage can result from estrogen treatment; this occurs prior to cancer development and at exactly the same location. Inflammation may be associated with prostate cancer risk, but no environmental carcinogenic risk factors have been definitively identified. We postulate that endogenous factors present in every man, sex steroids, are responsible for the high prevalence of prostate cancer in aging men, androgens acting as strong tumor promoters in the presence of a weak, but continuously present genotoxic carcinogen, estradiol-17beta.
 ...
PMID:Sex steroids and prostate carcinogenesis: integrated, multifactorial working hypothesis. 1726 65

Clifton Leaf, in his article "Why We're Losing the War on Cancer," presents criticisms of past research approaches and the small impact of this research thus far on producing cures or substantially extending the life of many cancer patients. It is true that gains in long-term survival for people with advanced cancers have been modest, hindered in part by the heterogeneity of tumors, which allows the cancers to persist using alternate molecular pathways and so evade many cancer therapeutics. In contrast, clinical trials have demonstrated that it is possible to reduce the incidence or improve cancer survival through prevention and early detection. Strides have been made in preventing or detecting early the four deadliest cancers in the United States (i.e., lung, breast, prostate, and colorectal). For example, 7-year follow-up data from the Breast Cancer Prevention Trial (BCPT) provides evidence that tamoxifen reduces the occurrence of invasive breast tumors by more than 40%; recent studies using aromatase inhibitors and raloxifene are also promising. The Prostate Cancer Prevention Trial (PCPT) showed that finasteride reduced prostate cancer incidence by 25%, and the ongoing Selenium and Vitamin E Cancer Prevention Trial (SELECT) is investigating selenium and vitamin E for prostate cancer prevention based on encouraging results from earlier studies. Living a healthy lifestyle, including regular physical activity, avoiding obesity, and eating primarily a plant-based diet has been associated with a lower risk of colorectal cancer. In addition, noninvasive stool DNA tests for early detection are being studied, which may lessen the reluctance of people to be screened for colorectal polyps and cancer. Behavioral and medical approaches for smoking prevention are ways to reduce the incidence of lung cancer, with antinicotine vaccines on the horizon that may help former smokers to avoid relapse. The US National Lung Screening Trial is testing whether early detection via spiral CT screening will reduce lung cancer mortality. Prevention and earlier detection offer efficient and practical strategies to reduce the cancer burden. Several of the suggestions Mr. Leaf makes, such as developing interdisciplinary collaborations and allocating resources to research earlier in the process of carcinogenesis, have become an integral strategy in the National Cancer Institute's (NCI) approach in the past decade, specifically in the realm of cancer prevention and early detection. For example, an aggressive program to identify biomarkers for earlier detection of cancer--the NCI's Early Detection Research Detection (EDRN)--has identified three promising biomarkers since its establishment in 2000. It collaborates with the National Institute of Standards and Technology and extramural scientists to develop validation standards and to identify the best technologies to use for systematic investigations. If these biomarkers can be validated, they might help to reduce cancer mortality.
 ...
PMID:A favorable view: progress in cancer prevention and screening. 1730 81

The abundance of fat tissue surrounding normal and malignant epithelial mammary cells raises the questions whether such "adipose milieu" is important in the local proinflammatory/genotoxic shift, which apparently promotes tumor development and worsens prognosis, and what conditions stimulate this shift, or "adipogenotoxicosis." We studied 95 mammary fat samples from 70 postmenopausal and 25 premenopausal breast cancer (BC) patients at a distance of 1.5-2.0 cm from tumors. The levels of leptin, adiponectin, TNFalpha and IL-6 release after 4-hr incubation of the samples were evaluated with ELISA, nitric oxide (NO) production by Griess reaction and lipid peroxidation by determination of thiobarbiturate-reactive products (TBRP). Infiltration of fat with macrophages (CD68-positive cells) and expression of cytochrome P450 1B1/estrogen 4-hydroxylase (CYP1B1) were detected by immunohistochemistry. Aromatase (CYP19) activity in mammary fat was measured by (3)H(2)O release from (3)H-1beta-androstenedione. In the postmenopausal BC patients, NO and TNFalpha production by adipose tissue explants increased independent of BMI and in parallel with decreasing leptin and, especially, adiponectin release. In the premenopausal patients, higher CYP1B1 expression and TBRP level were found in mammary fat, while higher aromatase activity was combined with higher CYP1B1 expression as well as NO and IL-6 production. In the postmenopausal group, impaired glucose tolerance was associated with higher IL-6 release production by fat and with higher IL-6/adiponectin ratio. Thus, signs of adipogenotoxicosis in mammary fat can be found in both pre- and postmenopausal BC patients. This condition is likely being maintained through estrogen- and glucose-related factors and mechanisms presumably associated with less favorable types of hormonal carcinogenesis.
 ...
PMID:Signs of proinflammatory/genotoxic switch (adipogenotoxicosis) in mammary fat of breast cancer patients: role of menopausal status, estrogens and hyperglycemia. 1739 26

In 1998, the concept of breast cancer prevention became a reality with the approval of tamoxifen to reduce the risk of developing breast cancer in women at increased risk for the disease. This approval was based on decades of research on selective estrogen receptor modulators providing an understanding of the role of the estrogen receptor in breast cell growth, and an appreciation of the carcinogenic process. Although results from the Breast Cancer Prevention Trial demonstrated a 49% reduction in breast cancer in women at increased risk, there were associated toxicities related to the estrogenic effects of tamoxifen; that is, deep vein thrombosis, pulmonary embolism, and endometrial cancer. In an effort to improve its benefit-risk profile, tamoxifen is now being compared with raloxifene, a selective estrogen receptor modulator approved for the treatment and prevention of osteoporosis. This equivalency prevention Study of Tamoxifen and Raloxifene completed accrual of 19 747 high-risk postmenopausal women in November 2004. Meanwhile, another class of estrogen-directed drugs, the aromatase inhibitors, have shown efficacy in breast cancer adjuvant trials, spawning a number of prevention trials that have recently been initiated. As with breast cancer the hormonal contribution to prostate carcinogenesis was the basis for the Prostate Cancer Prevention Trial which showed that finasteride, an androgen antagonist, reduces the incidence of prostate cancer compared to placebo.
 ...
PMID:Hormonal interventions to prevent hormonal cancers: breast and prostate cancers. 1741 94

High penetrance genes such as BRCA1 or BRCA2 account for only a small proportion of familial breast cancer in Chinese population. Estrogen has been proposed to participate in the proliferation and carcinogenesis of breast cancer. To investigate the association between genetic polymorphisms in genes encoding estrogen metabolizing, estrogen biosynthesizing enzyme and estrogen receptor and the breast cancer risk in BRCA1/BRCA2 negative Shanghai women, we conducted a case-control study including 114 cases with early-onset breast cancer or affected relatives and 121 healthy controls. The genotypes of estrogen receptor alpha (ERalpha), aromatase (CYP19), and catechol-O-methyltransferase (COMT) genes were analyzed by direct DNA-sequencing. Compared with H/H genotype of COMT Val158Met, COMT Val158Met L/L genotype was associated with a nonsignificantly elevated risk of breast cancer (OR: 3.72; 95% CI: 0.99-13.96, P=0.051). There was no statistically significant difference in genotype frequency of the ERalpha PvuII, ERalpha XbaI and CYP19 Arg264Cys polymorphism between controls and cases. When stratified by menopausal status, COMT Val158Met L/L (OR: 11.94; 95% CI: 1.48-96.03, P=0.02) and ERalpha PvuII P/p genotypes (OR: 2.67; 95% CI: 1.01-7.05, P=0.048) were associated with a significantly elevated risk of breast cancer in premenopausal women, and there was a association between ERalpha XbaI x/x genotype and the nonsignificantly increased risk of breast cancer in premenopausal women (OR: 6.88; 95% CI: 0.80-59.15, P=0.079). The multigenic analysis showed maybe these high risk genotypes had combined effect on breast cancer risk. Our findings suggest that polymorphism of genes involving estrogen-metabolizing pathway, estrogen- biosynthesizing pathway and estrogen receptor pathway may play an important role in the etiology of BRCA1/2 negative breast cancer with hereditary predisposing factors.
 ...
PMID:A multigenic study on breast cancer risk associated with genetic polymorphisms of ER Alpha, COMT and CYP19 gene in BRCA1/BRCA2 negative Shanghai women with early onset breast cancer or affected relatives. 1756 79

The estrogen receptor (ER) is the single most powerful predictor of breast cancer prognosis as well as an important contributor to the biology of carcinogenesis. In addition, endocrine therapy targeting ER directly (SERMS) or indirectly (aromatase inhibitors) forms the mainstay of adjuant therapy. Traditionally, human tumors are scored for the amount and presence of ER. However, this has centered on the population of ER found in the transformed epithelial cell nucleus. Over the last 40 years, it has been appreciated that additional cellular ER pools exist, in cytoplasm and at the plasma membrane. In this review, we discuss the important functions of extra-nuclear ER in breast cancer, including integration of function with nuclear ER.
 ...
PMID:Estrogen receptors outside the nucleus in breast cancer. 1759 74

Aromatase (CYP19) converts adrenal and ovarian androgens into estrogens, which supports the growth of estrogen-dependent breast cancers. Anti-aromatase agents are displacing antiestrogens as the first-line treatment for estrogen receptor positive breast cancers. Androgens can act as estrogen precursors, but besides this capability they can also directly act on breast cancer cells by binding to androgen receptors, which are present in the majority of breast cancer specimens. Epidemiological and clinical evidences suggest that higher levels of circulating androgen increase the risk of developing breast cancer. Androgen receptor gene polymorphisms which render the more transcriptionally active receptors have been related to a lower risk of breast cancer. It is currently accepted that androgens act as antiproliferative agents in the presence of estrogens in some breast cancer cell lines. However, emerging evidence suggests that direct androgenic activity might also stimulate cell growth in a subset of estrogen-resistant breast tumors. Here we discuss the supporting evidence which proposes that androgens themselves are actively involved in breast carcinogenesis and its clinical behaviour.
 ...
PMID:Androgens and androgen receptors in breast cancer. 1763 97


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>