UMLS:C0376358 - FACTA Search

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Query: UMLS:C0376358 (prostate cancer)
59,338 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cancer chemoprevention is a new approach in the management of cancer. Traditional cytotoxic chemotherapeutic approaches cannot cure most advanced solid malignancies. Chemoprevention can be defined as the use of non-cytotoxic drugs and natural agents to block the progression to invasive cancer. Chemoprevention can either prevent DNA damage that initiates the neoplastic transformation process or reverses the progression of pre-invasive lesions. Epidemiological observations, experimental evidence from animal carcinogenesis models, knock-out models, cancer cell lines and clinical trials have shown the efficacy of this approach. Recent advances in our understanding of carcinogenesis have led to the synthesis of new drugs that target specific receptors. Non-steroidal anti-inflammatory drugs target the prostaglandin pathway. The identification of the role of cyclooxygenase-2 in epithelial carcinogenesis led to the synthesis of selective cyclooxygenase-2 inhibitors (Celecoxib). Celecoxib was subsequently approved for the prevention of colon polyps in familial adenomatous polyposis after the completion of a randomized clinical trial. The large chemoprevention clinical trial with the selective estrogen receptor modulator, tamoxifen, showed the benefit of tamoxifen in the prevention of breast cancer in high-risk women. Retinoids and rexinoids target the retinoid receptors and have a role in chemoprevention of aerodigestive, hepatic and cervical neoplasia. Selenium, an inhibitor of the glutathione peroxidase system, is being tested in the chemoprevention of prostate cancer and lung cancer. The different isoforms of vitamin E (tocopherols) may be chemopreventive. Recent evidence indicates that gamma-tocopherol may be a more powerful chemopreventive than the alpha-tocopherol. The review details the rationale, experimental and clinical evidence and the drug targets of the chemopreventive agents that are currently in various phases of clinical development.
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PMID:Cancer chemoprevention drug targets. 1252 89

Prostate cancer chemoprevention (CP) can be defined as the use of natural and synthetic agents that inhibit, reverse or regress precancer and delay progression to invasive cancer. During the past two decades several CP strategies have evolved. The first generation of CP trials tested the efficacy of antioxidants and vitamins including B-carotene, vitamin A, retinol, 13 cis retinoic acid, vitamins E, C and selenium. Although these trials were disappointing, provocative hypotheses were generated for selenium and vitamin E that set the stage for future prostate trials. In the 1990s, the NCI launched a second generation of large CP trials aimed at breast and prostate cancer. One of these trials is the PCPT, testing the efficacy of a 5 alpha-reductase inhibitor-finasteride to prevent prostate cancer in 18,000 men. Although PCPT is still in progress, the NCI recently launched a second large primary prostate CP trial called SELECT, testing the efficacy of selenium and vitamin E in 32,400 men. The Prostate Cancer Progress Report to the Director of NCI in 1998 challenged the research community to design more efficient CP trials for prostate cancer. In response, the NCI has evolved a third generation of CP trials. This involves pharmacologically driven translational science research including agents and their targets, biomarker endpoints, suitable clinical models for testing agents and efficient trial designs employing high risk cohorts and surrogate endpoints. In summary, a dual strategy for CP is being developed which includes public health measures and a medical intervention approach.
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PMID:Evolving strategies for prostate cancer chemoprevention trials. 1268 72

Studies have been limited involving antioxidants as a mode of treatment for prostate cancer. The goal of this study was to develop alternative treatment and prevention for the invasive behavior of prostatic mutations by exploring the synergistic effects of several commercially available antioxidants. The specific aims were to examine the viability, proliferation, and morphology of human prostate cells in culture upon treatment of low and high doses of vitamin E, selenium, and lycopene alone or in combination. In phase I, groups were treated with physiological doses of the experimental agents. In phase II, the same groups were treated in combination to observe any synergistic effect. Upon treatment with selenium, lycopene, and vitamin E, vitamin E treated groups demonstrated the greatest effect on most assays in the study. Data obtained from this study did not demonstrate that the antioxidants would eradicate LNCaP prostatic carcinoma cells; however, the suppression of the metabolic pathways, cellular damage, and lowered prostatic specific antigen was observed.
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PMID:The synergistic effect of conventional and sustained delivery of antioxidants on LNCaP prostate cancer cell line. 1272 27

The etiology of prostate cancer remains virtually unknown. Although there are a number of new leads with regard to risk factors for prostate cancer, more research is required to confirm them. There is little purpose in conducting further case-control studies of prostate cancer-particularly since the use of PSA testing has become wide-spread. Instead, future epidemiologic studies should focus on prostate tumor subclassification, in terms of method of detection, markers of biological "aggressiveness," and genetic changes. Many of these new leads involve the possible influence of polymorphisms in key genes involved in important physiologic processes in the prostate. To fully explore the complexity of interrelationships between the several elements in these pathways will require large cohort studies in which blood is sampled prior to diagnosis. Such studies will be important for identifying which modifiable aspects of lifestyle (such as diet, alcohol, tobacco, physical activity) might be targeted for intervention, to reduce risk. The detection of early prostate cancers by PSA testing relatives of men with prostate cancer has affected the prevalence of phenocopies and, hence, the meaningfulness of risk estimation in prostate cancer families. Because multiple-case families form the substrate for gene hunting via linkage analysis, this phenocopy phenomenon is going to cause considerable confusion and wasted effort. Presently, men with a family history of prostate cancer can be provided with little advice in terms of preventive action. It is likely that one or more genetic mutations associated with a high risk for prostate cancer will be identified in the near future. Even so, the risks probably will be similar to those for mutations in the first two breast cancer genes--informative for very few families. It is difficult to foresee, as and when high-risk mutation carriers are identified, what advice should be offered to them: prophylactic prostatectomies seem to have less attraction than do prophylactic mastectomies for women at high risk of breast cancer. This issue becomes more complex when considering counseling on the basis of a genetic profile involving many low-risk polymorphisms. Hopefully, such genetic screening should occur only after its efficacy has been established; when there is a better understanding of prostate biology, tumor heterogeneity, and prognosis; and when there are proven treatment or prevention options available. Prevention is held to be better than cure, and there are some potentially interesting chemopreventive agents that require careful trial before public health initiatives can be promoted. Potential candidates include vitamin E, selenium, zinc, and lycopene as dietary supplements. There are other agents that may be appropriate for pharmaceutical development, including inhibitors of COX-2 and IGF-1 activity. It is important that chemoprevention trials are followed-up for a sufficient period of time and that other endpoints also are captured, because the supplementation of diets with superphysiologic doses of individual micronutrients sometimes has caused unexpected and unwanted results--for example, an 18% increase in lung cancers observed in the beta-carotene arm of the ATBC trial.
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PMID:The epidemiology of prostate cancer. 1273 98

Increased intake of vitamin E has been suggested to be protective against prostate cancer in men, but the effects of vitamin E on prostate growth and function remain poorly defined. The purpose of this study was to determine the effects of vitamin E deficiency on pubertal growth and maturation of the prostate in the rat. Animals were placed on a vitamin E deficient diet at 28 days of age and were followed for 15 and 26 weeks. Vitamin E deficient rats had a circulating vitamin E level of less than 1% of control animals and experienced a decrease in body and testis weight. The deficiency did not alter the weights of the ventral and dorsal lobes of the prostate. However, there was an increase in weight, DNA, and protein contents of the lateral lobe in control and vitamin E deficient rats from 15 to 26 weeks of treatment, but these increases were significantly lower in vitamin E deficient 26-week treated rats. The volume of secretion per milligram tissue was greater in the ventral than lateral or dorsal lobes. The volume of secretion and activity of the secretory 26 kDa protease in the ventral prostate was lower in vitamin E deficient rats at 15 weeks, but not at 26 weeks of treatment. In contrast, the relative protein content of lateral lobe secretion increased in both control and vitamin E deficient rats from 15 to 26 weeks of treatment. The lateral, but not ventral or dorsal, lobes of both control and vitamin E deficient rats were affected by chronic prostatitis as evidenced by infiltration of inflammatory cells. The lateral lobes also showed markedly elevated activities of the matrix metalloproteinases gelatinase A (MMP-2) and gelatinase B (MMP-9). These data indicate that vitamin E deficiency does not alter the growth of the prostatic lobes, nor the onset and extent of lateral lobe specific prostatitis, but it may delay some differentiated functions such as secretion of specific proteins in the ventral lobe. Thus, the effects of vitamin E in the prostate of the rat appear to be selective.
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PMID:Effect of vitamin E deficiency on the growth and secretory function of the rat prostatic complex. 1278 14

Recent epidemiological studies suggest an association between higher blood levels of insulin-like growth factor I (IGF-I) and increased risk of prostate cancer. We evaluated the association between prediagnostic levels of IGF-I and insulin-like growth factor binding protein 3 (IGFBP-3) and prostate cancer risk in a nested case-control study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. Within the same cohort (using different cases and controls who had sequential serum samples available) we also examined changes in serum IGF-I and IGFBP-3 levels over time by case status. The risk association study included incident prostate cancer cases (n = 100) diagnosed at least 5 years after baseline blood draw (range, 5-12 years; median 9 years) and frequency-matched (4:1) controls. The sequential serum study included all of the prostate cancer cases (n = 21) with prediagnostic (2-3 years before diagnosis) and diagnostic serum available, and pair-matched controls (1:1). An ELISA was used to quantitate serum levels of IGF-I and IGFBP-3 for both studies. The association between IGF-I or IGFBP-3 and prostate cancer risk was assessed using conditional logistic regression, and paired t tests were used to evaluate case-control differences in change in serum analytes over time. We found no significant association between either IGF-I or IGFBP-3 and prostate cancer risk. In a multivariate analysis, we observed an odds ratio of 0.52 (95% confidence interval, 0.23-1.16) for the fourth versus the first quartile of serum IGF-I. Serum IGF-I, but not IGFBP-3, increased significantly over time in cases (18% increase) but not controls (4% decrease; P = 0.02). In contrast to previous reports, we found no evidence to support a causal association between serum IGF-I or IGFBP-3 and the risk of prostate cancer. It is possible that serum IGF-I may be serving as a tumor marker rather than an etiologic factor in prostate cancer.
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PMID:Serum insulin-like growth factor I: tumor marker or etiologic factor? A prospective study of prostate cancer among Finnish men. 1287 96

Target populations for chemoprevention trials should include those at higher than average risk for the development of prostate cancer as defined by explicit epidemiologic and genetic criteria. Such populations include a "primary prevention" group without histologic or clinical evidence of cancer, and several clinical models of "secondary prevention," including those with clinically evident disease prior to definitive therapy and those at high risk of recurrence after therapy based on histology and/or biochemical status. Each risk group and clinical model has potential advantages and disadvantages, and the mechanisms which underlie disease development and progression in each group may be unique. These observations give rise to many potential clinical trials of specific agents. These trials should also include collection of data on potentially confounding influences on disease development and progression. Preclinical, epidemiologic, and Phase II data suggest that both selenium and vitamin E have potential efficacy in prostate cancer prevention. The experience of the Prostate Cancer Prevention Trial (PCPT) demonstrates the interest and dedication of healthy men to long-term studies of cancer prevention. SELECT, the Selenium and Vitamin E Cancer Prevention Trial, is an intergroup phase III, randomized, double-blind, placebo-controlled, population-based clinical trial designed to test the efficacy of selenium and vitamin E alone and in combination in the prevention of prostate cancer which builds on secondary analyses of large-scale chemoprevention trials for other cancers and the lessons of PCPT.
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PMID:Clinical models for testing chemopreventative agents in prostate cancer and overview of SELECT: the Selenium and Vitamin E Cancer Prevention Trial. 1290 56

Antioxidants, such as vitamin E, are being investigated for efficacy in prostate cancer prevention. In this study, we show that the antioxidant moiety of vitamin E, 2,2,5,7,8-pentamethyl-6-chromanol (PMCol), has antiandrogen activity in prostate carcinoma cells. In the presence of PMCol, the androgen-stimulated biphasic growth curve of LNCaP human prostate carcinoma cells was shifted to the right. The PMCol-induced growth shift was similar to that produced by treatment with the pure antiandrogen bicalutamide (i.e., Casodex), indicative of androgen receptor (AR) antagonist activity. The concentration of PMCol used was below the concentration required to affect cell growth or viability in the absence of androgen. Using an AR binding competition assay, PMCol was found to be a potent antiandrogen in both LNCaP and LAPC4 cells, with an IC(50) of approximately 10 micro M against 1 nM R1881 (methyltrienolone; a stable, synthetic androgen). Prostate-specific antigen release from LNCaP cells produced by androgen exposure with either 0.05 or 1.0 nM R1881 was inhibited 100% and 80%, respectively, by 30 micro M PMCol. Also, PMCol inhibited androgen-induced promoter activation in both LNCaP and LAPC4 cells. However, PMCol did not affect AR protein levels, suggesting that the inhibitory effects of PMCol on androgenic pathways were not due to decreased expression of the AR. Therefore, growth modulation by the antioxidant moiety of vitamin E in androgen-sensitive prostate carcinoma cells is due, at least in part, to its potent antiandrogenic activity.
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PMID:Androgen antagonist activity by the antioxidant moiety of vitamin E, 2,2,5,7,8-pentamethyl-6-chromanol in human prostate carcinoma cells. 1293 70

The effects of nine potential cancer chemopreventive agents on cell growth or clonogenic survival were evaluated in normal human prostate epithelial cells, an immortalized but non-tumorigenic human prostate epithelial cell line (267B1), a human benign prostatic hyperplasia (BPH) cell line (BRF-55T), and a human prostate cancer cell line (267B1/Ki-ras). Of the nine agents tested, 9-cis retinoic acid, liarozole fumarate, phenylenebis(methylene)-selenocyanate (p-XSC), and L-selenomethionine demonstrated much stronger growth inhibitory effects on prostate cancer cells than on the normal prostate epithelial cells, suggesting that these agents may be useful as prostate cancer chemopreventive agents. 9-cis retinoic acid, genistein, liarozole fumarate, p-XSC, L-selenomethionine and vitamin E also showed much stronger growth inhibitory effects on BRF-55T cells than on the normal prostate epithelial cells, indicating that these agents may also be useful for the prevention and treatment of BPH. Difluoromethylornithine (DFMO), DHEA analogue 8354 (fluasterone), and oltipraz did not show strong inhibitory effects on the growth or survival of normal prostate epithelial cells, 267B1 or 267B1/Ki-ras cells, suggesting that these agents may not be effective as prostate cancer preventive or therapeutic agents.
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PMID:In vitro evaluation of chemopreventive agents using cultured human prostate epithelial cells. 1453 35

The ongoing Selenium and Vitamin E Chemoprevention Trial is designed to evaluate the efficacy of these two agents, either individually or in combination, in reducing the incidence of prostate cancer in healthy men over 55 years of age. Little information, however, is available on the potential synergy between vitamin E and selenium in chemoprevention. The present study was aimed at addressing this gap of knowledge with the use of the androgen-unresponsive, p53-null, PC-3 human prostate cancer cell line. The growth-inhibitory activity of vitamin E appeared to be dependent on the chemical form. In our hands, D-alpha-tocopheryl succinate (VES) was much more potent than either DL-alpha-tocopherol or D-alpha-tocopheryl acetate. Combining VES with methylseleninic acid (MSA), a selenium metabolite, produced a synergistic effect on cell growth suppression. The synergy was accounted for primarily by an augmented apoptotic response. Poly(ADP-ribose) polymerase cleavage and activation of specific caspases were confirmed by Western blot analysis. The caspases that were commonly modulated by either VES or MSA included initiator caspases-8 and -10, as well as executioner caspases-3, -6, and -7. In contrast, caspase-9 was activated only by VES, whereas caspases-1 and -12 were activated only by MSA. Based on the above information, it is proposed that the mitochondrial pathway and the endoplasmic reticulum stress/cytokine signaling pathway might be involved in apoptosis induction by VES and MSA, respectively. These two pathways may act in a cooperative manner to switch on the full force of the apoptotic machinery when cells are treated with both VES and MSA.
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PMID:Synergy between selenium and vitamin E in apoptosis induction is associated with activation of distinctive initiator caspases in human prostate cancer cells. 1458 1

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