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  • 1
    ISSN: 1524-4741
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Chemoprevention, or intervention with chemical agents at the precancer stage to avoid or slow the development of the carcinogenic process, is one strategy to reduce both the incidence of breast cancer and its mortality. Systematic development of cancer chemopreventive drugs calls for evaluation of pre-clinical efficacy in well-characterized in vitro screens and animal cancer models. Highly promising agents are also included in traditional pre-clinical toxicity tests performed in two species. The most promising and least toxic agents enter clinical trials, including both phase I safety and pharmacokinetics evaluations and phase II and III efficacy studies. The use of populations with defined, measurable biologic alterations in tissue occurring prior to cancer development, i.e. intermediate biomarkers, is important to successful phase II chemoprevention trials. The intermediate biomarkers may be of several types, such as histological/premalignant lesions, proliferative, genetic/regulatory, differentiation-related, or biochemical. For example, ductal and lobular carcinoma in situ are premalignant lesions in the human breast. These lesions are tissue at very high risk of malignant progression and also have the potential to be modulated by chemopreventive agents. In addition, other types of biomarkers may be identified within the lesions. These biomarkers could then serve as surrogate trial end-points, instead of cancer incidence, for use in shorter, less costly trials.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @breast journal 1 (1995), S. 0 
    ISSN: 1524-4741
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Surrogate endpoint biomarkers (SEBs) are tissue changes observed in premalignant disease that highly correlate with cancer risk. They are urgently needed as endpoints in clinical trials of chemopreventive agents for breast premalignant disease because they require less time, money and effort compared to the conventional endpoint of cancer incidence reduction. The program of the Chemoprevention Branch, NCI, is supporting 30 clinical trials of various chemopreventive agents for premalignant disease in different organ systems that are being monitored by the SEBs of DNA aneuploidy, abnormally high proliferative index, abnormal nuclear morphometry (aberrant size, shape, texture, and pleomorphism) and nucleolar number, position in the nucleus, and morphometry. Evidence from the literature permits the expectation that in premalignant breast disease these SEBs, when measured by computer-assisted quantitative image analysis, will accurately predict the risk of recurrence of breast DCIS after lumpectomy.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 276 (1976), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Methods in cell science 2 (1976), S. 423-427 
    ISSN: 1573-0603
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-0603
    Keywords: Chemoprevention ; In vitro assays ; Drug screening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This issue reports the methods of twelve in vitro assays currently being used to screen potential chemopreventive agents for activity. These assays provide quantitative data to help determine the efficacy and prioritize agents for further development in whole animal screening. It is essential that such in vitro assays provide accurate, consistent, and relevant data to identify and prioritize agents with the most promise to prevent human cancer. The twelve assays presented in this volume are currently providing such data to the National Cancer Institute's Chemoprevention Program.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 131-137 
    ISSN: 0091-7419
    Keywords: actin filament bundles ; LETS protein ; cytoskeleton ; chick embryo fibroblasts ; triton cytoskeleton ; nonmuscle actin ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The Balb/3T3 and C3H/10T1/2 lines, noted for their marked postconfluence inhibition of proliferation and anchorage dependence, and frequently studied as nontumorigenic lines that are compared with tumorigenic sublines transformed with various agents, produced tumors within two to four months at low-cell dosage (3 × 104 cells) when implanted subcutaneously attached to 1 × 5 × 10 mm polycarbonate platelets. Platelets alone did not produce tumors. The cultured Balb/3T3 tumor cells showed loss of both postconfluence inhibition of proliferation and anchorage dependence. Tumors arising form attached Balb/3T3 cells in (BALB/c × C57B1/6)F1 hybrids were shown to be transplantable to BALB/c but not to C57B1/6 mice, proving that the tumors were derived form Balb/3T3 and not from host cells. The tumors exhibited unique transplantation rejection antigens that did not cross-react with each other. Scanning electronmicroscopy of Balb/3T3 cells and derive tumor cells on TeflonTeflon: Registered trademark of DuPont Plastics. substrates (on which only the tumor cells and not the parent Balb/3T3 cells could grow) revealed that the two cell types were remarkably similar in appearance, except that the tumor cells were larger and showed many more microvilli that tended to concentrate over the nucleus. We conclude that Balb/3T3 cells and C3H/10T1/2 cells are preneoplastic and give rise to spontaneously transformed clones when implanted in vivo attached to a solid substrate.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 9 (1978), S. 147-156 
    ISSN: 0091-7419
    Keywords: variant cell lines ; receptors ; cell surface properties ; concanavalin A ; colchicine ; tumorigenicity ; growth ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We report the use of three classes of variants from the long-established malignantly transformed LM cell line to demonstrate that the apparent mobility of cell surface receptors need not be dependent on the expression of the transformed phenotype in vitro.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 53 (1993), S. 44-44 
    ISSN: 0730-2312
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 53 (1993), S. 234-241 
    ISSN: 0730-2312
    Keywords: Breast cancer risk ; chemoprevention ; intermediate biomarkers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Early phase chemoprevention trials differ from standard therapeutic clinical trials because asymptomatic, healthy people are treated with a potentially toxic intervention for a prolonged period of time. Current subject selection protocols have relied upon epidemiological methods to identify highrisk individuals. Most available data provide risk estimates for various individual risk factors, but few have reported risk estimates for combinations of risk factors. Selection criteria for the large tamoxifen intervention trial (NSABP P1) were developed from the work of Gail et al. [1]. The Gail model takes into account non-genetic factors (e.g., nulliparity, age at menarche, preexisting pathological conditions) and genetic factors (family history). Using a lifetime risk of 10% of developing breast cancer as a standard to intervention trial. This approach has been criticized for being insufficiently selective (i.e., all women ≥60 yrs), but appears to be the best available method to select subjects for a chemoprevention trial. Other approaches have been based on identification of very high-risk women with acknowledged pathologic conditions [lobular carcinoma in situ, ductal carcinoma in situ (DCIS)]. Attempting to use these proliferative lesions as pathologic endpoints for drug effect has not been attempted. DCIS as a risk factor for tamoxifen intervention was excluded because of controversies over its management and because of frequent difficulties in distinguishing microinvasive from non-invasive lesions. Women treated for early stage breast cancer (Stage I) may be subjects for early stage chemopreventive interventions.We propose the use of intermediate endpoint biomarkers and genetic markers as entry criteria for early phase chemoprevention trials. For colorectal cancer chemoprevention, we have used a two-step selection process. The first step was based on epidemiologic risk assessment. Entry into the study required that a potential intermediate biomarker be positive and quantifiable. The relationship between modulation of a pre-transformational biomarker and development of cancer ultimately needs proof in a primary interventional trial; however, this methodology may permit screening of potential chemopreventive agents at lower cost and more rapid turn-around times. In early chemopreventive agent testing for breast cancer chemoprevention, we propose a similar two-step procedure. Epidemiological and/or pathological criteria for risk would be followed by a procedure to obtain cellular material. The cellular material would be assayed for pre-transformational cellular change.Identifying predictive genes in familial breast cancer cohorts such as the modified BRCA1 gene promises to select individuals at high familial and potentially physiological or environmental risk. The identification of the abnormal gene product in individuals and families will provide another important group of subjects for chemopreventive interventions. The identification of high-risk subjects for breast cancer chemoprevention, particularly those with familial genetic risk, carries important ethical problems. Such women may have difficulties obtaining health and life insurance, deciding to have children, and obtaining work. Chemoprevention trials with genetic selection criteria will need to develop methods of dealing with these issues.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0730-2312
    Keywords: Animal models ; carcinogenesis ; chemoprevention ; drug development ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In the NCI, Chemoprevention Branch drug development program, potential chemopreventive agents are evaluated for efficacy against chemical carcinogen-induced tumors in animal models. This paper summarizes the results of 144 agents in 352 tests using various animal efficacy models. Of these results, 146 were positive, representing 85 different agents.The target organs selected for the animals model are representative of high-incidence human cancers. The assays include inhibition of tumors induced by MNU in hamster trachea, DEN in hamster lung, AOM in rat colon (including inhibition of AOM-induced aberrant crypts), MAM in mouse colon, DMBA and MNU in rat mammary glands, DMBA promoted by TPA in mouse skin, and OH-BBN in mouse bladder.The agents tested may be classified into various pharmacological and chemical structural categories that are relevant to their chemopreventive potential. These categories include antiestrogens, antiinflammatories (e. g., NSAIDs), antioxidants, arachidonic acid metabolism inhibitors, GST and GSH enhancers, ODC inhibitors, protein kinase C inhibitors, retinoids and carotenoids, organosulfur compounds, calcium compounds, vitamin D3 and analogs, and phenolic compounds (e. g., flavonoids). The various categories of compounds have different spectra of efficacy in animal models. In hamster lung, GSH-enhancing agents and antioidants appear to have high potential for inhibiting carcinogenesis. In the colon, NSAIDs and other antiinflammatory agents appear particularly promising. Likewise, NSAIDs are very active in mouse bladder. In rat mammary glands, retinoids and antiestrogens (as would be expected) are efficacious. Several of the chemicals evaluated also appear to be promising chemopreventive agents based on their activity in several of the animal models. Particularly, the ODC inhibitor DFMO was active in the colon, mammary glands, and bladder models, while the dithiolthione, oltipraz, was efficacious in all the models listed above (i. e., lung, colon, mammary glands, skin, and bladder). 1994 Wiley-Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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