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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
    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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  • 3
    ISSN: 0730-2312
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: 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. © 1997 Wiley-Liss, Inc.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 63 (1996), S. 37-40 
    ISSN: 0730-2312
    Keywords: mammary cancer ; cancer genetics ; epigenetic ; chemoprevention ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Individual genetically determined susceptibility to cancer as well as acquired epigenetic and genetic organ specific alterations are important considerations in choosing target populations for chemopreventive trials. These individual epigenetic and genetic alterations can also serve as potential biomarkers for chemoprevention clinical trials. In order to model these potential markers for chemoprevention investigations, we are examining a series of interrelated rat models.Inbred rats vary in their susceptibility to mammary cancer induction by environmental agents. For example, the WF strain is highly susceptible to chemically induced mammary cancer while the Cop rat is almost completely resistant. The F344 is intermediate in susceptibility to chemically induced mammary cancer. These differential susceptibilities are inherited in a dominant pattern. For example, resistance is due to the inheritance of Mcs gene(s) which likely act by altering the differentiation lineage of mammary epithelial cells.As tumors form in the mammary glands of these rats, they acquire additional epigenetic and genetic alterations. Epigenetic initiation is a very frequent cellular event following carcinogen exposure which may predispose cells to genetic change including allelic imbalance. For example, following a standard dose of NMU or DMBA over 1% of cells are epigenetically initiated. During the carcinogenesis process, initiated cells may acquire genetic change such as oncogene activation and allelic imbalance. Interestingly, the pattern of allelic imbalance appears to be an inherited trait. For example, a non-random loss of heterozygosity (LOH) in rat chromosome 1 following DMBA only occurs in certain strains, such as Cop rats. Interestingly this change does not occur following initiation by ionizing radiation.It will thus be important to identify these epigenetic and genetic events which underlie mammary carcinogenesis as well as determine their patterns of inherited predisposition and temporal occurrence. Such knowledge is critical if we are to develop new molecular markers for chemoprevention trials. J. Cell. Biochem. 25S:37-40. © 1997 Wiley-Liss, Inc.
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  • 5
    ISSN: 0730-2312
    Keywords: chemoprevention ; genetic/regulatory biomarkers ; high-risk cohorts ; intraepithelial neoplasia ; phase II clinical trials, risk biomarkers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: 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. J. Cell. Biochem. 25S:1-14. © 1997 Wiley-Liss, Inc. This article is a U.S. Government work and, as such, is in the public domain in the United States of America.
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  • 6
    ISSN: 0730-2312
    Keywords: cancer chemopreventive agents ; drug development ; retinoids ; DFMO ; NSAIDs ; oltipraz ; Phase I clinical trials ; Phase II clinical trials ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Clinical chemoprevention trials of more than 30 agents and agent combinations are now in progress or being planned. The most advanced agents are well known and are in large Phase III chemoprevention intervention trials or epidemiological studies. These drugs include several retinoids [e.g., retinol, retinyl palmitate, all-trans-retinoic acid, and 13-cis-retinoic acid], calcium, βcarotene, vitamin E, tamoxifen, and finasteride. Other newer agents are currently being evaluated in or being considered for Phase II and early Phase III chemoprevention trials. Prominent in this group are all-trans-N-(4-hydroxy phenyl)retinamide (4-HPR) (alone and in combination with tamoxifen), 2-difluoromethylornithine (DFMO), nonsteroidal antiinflammatory drugs (aspirin, piroxicam, sulindac), oltipraz, and dehydroepiandrostenedione (DHEA).A third group is new agents showing chemopreventive activity in animal models, epidemiological studies, or in pilot clinical intervention studies. They are now in preclinical toxicology testing or Phase I safety and pharmacokinetics trials preparatory to chemoprevention efficacy trials. These agents include S-allyl-l-cysteine, curcumin, DHEA analog 8354 (fluasterone), genistein, ibuprofen, indole-3-carbinol, perillyl alcohol, phenethyl isothiocyanate, 9-cis-retinoic acid, sulindac sulfone, tea extracts, ursodiol, vitamin D analogs, and p-xylyl selenocyanate. A new generation of agents and agent combinations will soon enter clinical chemoprevention studies based primarily on promising chemopreventive activity in animal models and in mechanistic studies. Among these agents are more efficacious analogs of known chemopreventive drugs including novel carotenoids (e.g., α-carotene and lutein). Also included are safer analogs which retain the chemopreventive efficacy of the parent drug such as vitamin D3 analogs. Other agents of high interest are aromatase inhibitors (e.g., (+)-vorozole), and protease inhibitors (e.g., Bowman-Birk soybean trypsin inhibitor). Combinations are also being considered, such as vitamin E with l-selenomethionine. Analysis of signal transduction pathways is beginning to yield classes of potentially active and selective chemopreventive drugs. Examples are ras isoprenylation and epidermal growth factor receptor inhibitors. 1997 Wiley-Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America.
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  • 7
    ISSN: 0730-2312
    Keywords: CAAX motif ; farnesyltransferase inhibitor ; K-ras ; lung cancer ; monoterpene ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: This study was designed to test the chemopreventive potential of perillyl alcohol, an inhibitor of farnesyltransferase, in a mouse lung tumor bioassay. Perillyl alcohol is a naturally occurring monoterpene found in lavender, cherries, and mint. We have shown previously that the majority of lung tumors in this bioassay have an activating mutation in the K-ras gene, which occurs early in the development of mouse lung carcinogenesis. The Ras protein undergoes a series of post-translational modifications, the first of which is farnesylation at the cysteine of the C-terminal CAAX motif. These modifications lead to the anchoring of Ras p21 to the plasma membrane in its biologically active state. Activated Ras p21 couples growth regulatory signals from receptor tyrosine kinases to cytoplasmic second messengers. In a preliminary study, we determined the maximum tolerated dose of perillyl alcohol to be 75 mg/kg body weight. For the bioassay, 5-week-old male (C3H/HeJ X A/J) F1 hybrid mice were randomized into trial groups, and treated with perillyl alcohol three times per week i.p., starting 1 week prior to initiation with the carcinogen NNK, and continuing for 22 weeks after initiation. Our results show a 22% reduction in tumor incidence, and a 58% reduction in tumor multiplicity. Our study demonstrates that perillyl alcohol is an effective chemopreventive compound in the mouse lung tumor bioassay. J. Cell. Biochem. Suppl. 27:20-25. © 1998 Wiley-Liss, Inc.
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  • 8
    ISSN: 0730-2312
    Keywords: chemoprevention ; H-ras ; PCNA ; rat ; retinoid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Mammary tumors were induced in 48-52-day-old female Sprague-Dawley rats in metestrus or diestrus with a single jugular injection of MNU (50 mg/kg). Control rats received the saline vehicle (Group 4 n = 9). Rats were fed 4% Teklad diet containing either 0 (Group 3, n = 20) or 782 mg 4-HPR/kg diet. 4-HPR supplementation was initiated either 1 week prior to (Group 1, n = 14) or 4 weeks following MNU administration (Group 2, n = 19). Neither body weight nor food intake differed significantly between treatment groups. Feeding of 4-HPR 1 week prior to tumor induction reduced the number of tumors (0.8±.2) when compared to MNU control rats (2.1±.4). Immunohistochemical staining of mammary tumor sections for PCNA was quantitated by microdensitometry and expressed as an HSCORE. No differences in HSCORE were observed between tumor groups although the percentage of nuclear area occupied by intermediate and darkly stained nuclei was reduced in the late 4-HPR group. GC→AT transitions in codon 12 of the H-ras gene were detected in 50% (12/24) of MNU control tumors, 60% (6/10) of early 4-HPR tumors, and 38% (6/16) of late 4-HPR tumors. Mutation rates did not differ significantly between groups. 4-HPR appears to be a more effective chemopreventive when fed during the initiation period. J. Cell. Biochem. Suppl. 27:92-99. © 1998 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 67 (1997), S. 49-63 
    ISSN: 0730-2312
    Keywords: mouse lung ; genetic alteration ; aberrant gene expression ; surrogate endpoint biomarkers ; cancer chemoprevention ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Specific genetic alterations affecting known tumor suppressor genes and proto-oncogenes occur during mouse lung tumorigenesis. These include mutational activation of the K-ras gene, commonly seen at a frequency of about 80% in both spontaneously occurring and chemically induced adenomas and adenocarcinomas of the lung, suggesting that it is an early event that persists into malignancy. Allelic loss of the p16 tumor suppressor gene also is a frequent event, occurring in about 50% of mouse lung adenocarcinomas, but rarely in lung adenomas, suggesting that it may play a role in malignant conversion or progression of lung tumors. Other genetic alterations detected in mouse lung tumors include reduced expression of Rb and p16, and increased c-myc expression. Alterations of these genes are also common in the genesis of human lung cancer. Genetic linkage analysis to identify human lung cancer susceptibility genes is difficult due to the genetic heterogeneity and exposure to environmental risk factors. The mouse lung tumor model has become a valuable alternative for identifying such genes. Recently, loci responsible for mouse lung tumor susceptibility have been mapped to chromosomes 6, 9, 17, and 19, while those linked to lung tumor resistance have been mapped to chromosomes 4, 11, 12, and 18. Known candidate susceptibility or resistance genes include the K-ras proto-oncogene on chromosome 6, and the p16 tumor supressor gene on chromosome 4. With evidence of considerable overlap between the genetic alterations that underlie human and mouse lung tumorigenesis, the mouse lung tumor model has been expanded to include pre-clinical screening of chemopreventive agents against human lung cancer. Studies on the modulation of genetic defects in mouse lung tumors by known and potential chemopreventive agents should further the goal of developing an effective prevention and treatment of lung cancer. J. Cell. Biochem. Suppls. 28/29:49-63. © 1998 Wiley-Liss, Inc.
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  • 10
    ISSN: 0730-2312
    Keywords: Cervical cancer ; cervical intraepithelial neophsia (CIN) ; chemoprevention ; computer-assisted image analysis ; endometrial cancer ; intermediate biomarkers ; ovarian cancer ; Phase II trials ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: 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-wellcharacterized 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 cemopreventive 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 decreased 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 relying 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 FCNA CIN and atypical endometrial hyperplasia are both examples of intraepithelial neoplasia that meet the biomarker criteria and are the basis for quantifiable surrogate endpoints for Phase II chemoprevention trials.
    Additional Material: 3 Tab.
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