Janet Cliatt

National Cancer Institute (USA), Maryland, United States

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Publications (4)16.47 Total impact

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    ABSTRACT: Aberrant crypt foci (ACF) are considered the earliest identifiable preneoplastic colonic lesions; thus, a greater understanding of the nature of genetic changes underlying the transformation of normal colonic mucosa (NM) into ACF may provide insight into the mechanisms of carcinogenesis. ACF were identified by indigo carmine spraying onto colonic mucosa during colonoscopy and isolated as standard pinch biopsies of the mucosal areas containing the ACF. RNAs isolated from ACF and matched NM biopsies from the ascending and descending colons of 13 patients were analyzed on arrays containing 9128 cDNAs. Thirty-four differentially expressed (P < 0.001) genes were found in a paired comparison of the ACF and NM samples, and 25 of 26 matched pairs of ACF and NM could be correctly classified in leave-one-out cross-validation. Differential expression for seven of eight genes was confirmed by real-time reverse transcription-PCR. Furthermore, ACF and NM samples, including six pairs of ACF and NM samples that had not previously been analyzed by array hybridization, can be correctly classified on the basis of the overexpression in ACF of three selected genes (REG4, SRPN-B5, and TRIM29) evaluated by real-time reverse transcription-PCR. In a separate analysis of 13 biopsy pairs from either ascending or descending colon, ACF and NM samples could also be correctly classified by the gene expression patterns. Analysis of gene expression differences in ACF from the ascending and descending colon versus NM samples indicates that ACF from these distinct colonic locations are converging toward similar gene expression profiles and losing differences in gene expression characteristic of NM from the ascending versus descending colon.
    Cancer Epidemiology Biomarkers &amp Prevention 11/2006; 15(11):2253-62. · 4.56 Impact Factor
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    ABSTRACT: A clinical trial was recently conducted to evaluate the safety and efficacy of a selective inhibitor of cyclooxygenase-2 (celecoxib) in hereditary nonpolyposis colon cancer patients. In a randomized, placebo-controlled phase I/II multicenter trial, hereditary nonpolyposis colon cancer patients and gene carriers received either celecoxib at one of two doses or placebo. The goal was to evaluate the effects of these treatment arms on a number of endoscopic and tissue-based biomarker end points after 12 months of treatment. As part of this trial, we analyzed gene expression by cDNA array technology in normal descending (rectal) colonic mucosa of patients before and after treatment with celecoxib or placebo. We found that treatment of patients with celecoxib at recommended clinical doses (200 and 400 mg p.o. bid), in contrast to treatment with placebo, leads to changes in expression of >1,400 genes in the healthy colon, although in general, the magnitude of changes is <2-fold. Twenty-three of 25 pairs of colon biopsies taken before and after celecoxib treatment can be classified correctly by the pattern of gene expression in a leave-one-out cross-validation. Immune response, particularly T- and B-lymphocyte activation and early steps of inflammatory reaction, cell signaling and cell adhesion, response to stress, transforming growth factor-beta signaling, and regulation of apoptosis, are the main biological processes targeted by celecoxib as shown by overrepresentation analysis of the distribution of celecoxib-affected genes across Gene Ontology categories. Analysis of possible cumulative effects of celecoxib-induced changes in gene expression indicates that in healthy colon, celecoxib may suppress the immune response and early steps of inflammation, inhibit formation of focal contacts, and stimulate transforming growth factor-beta signaling.
    Cancer Epidemiology Biomarkers &amp Prevention 07/2006; 15(7):1382-91. · 4.56 Impact Factor
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    ABSTRACT: Distinct epidemiological and clinicopathological characteristics of colorectal carcinomas (CRCs) based on their anatomical location suggest different risk factors and pathways of transformation associated with proximal and distal colon carcinogenesis. These differences may reflect distinct biological characteristics of proximal and distal colonic mucosa, acquired in embryonic or postnatal development, that determine a differential response to uniformly distributed environmental factors. Alternatively, the differences in the epidemiology of proximal and distal CRCs could result from the presence of different procarcinogenic factors in the ascending versus descending colon, acting on cells with either similar or distinct biological characteristics. We applied cDNA microarray technology to explore the possibility that mucosal epithelium from adult proximal and distal colon can be distinguished by their pattern of gene expression. In addition, gene expression was studied in fetal (17-24 weeks gestation) proximal and distal colon. More than 1000 genes were expressed differentially in adult ascending versus descending colon, with 165 genes showing >2-fold and 49 genes showing >3-fold differences in expression. With almost complete concordance, biopsies of adult colonic epithelium can be correctly classified as proximal or distal by gene expression profile. Only 87 genes were expressed differently in ascending and descending fetal colon, indicating that, although anatomically relevant differences are already established in embryonic colon, additional changes in gene expression occur in postnatal development.
    Cancer Epidemiology Biomarkers &amp Prevention 08/2003; 12(8):755-62. · 4.56 Impact Factor
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    ABSTRACT: To determine the toxicities and pharmacokinetic effects of eniluracil (EU) given on two weekly dosing schedules with 5-fluorouracil (5-FU) and leucovorin (LV). A group of 26 patients received a single 24-h i.v. infusion of 5-FU 2300 mg/m(2) to provide a pharmacokinetic reference. After 2 weeks, patients received oral EU 20 mg plus LV 30 mg on days 1-3 with a single dose of 5-FU 15-29 mg/m(2) on day 2, or LV 30 mg on days 1-2 with a single dose of EU at least 1 h prior to 5-FU 29 mg/m(2) on day 2 weekly for 3 of 4 weeks. Diarrhea was the most common dose-limiting toxicity. The recommended dose of 5-FU is 29 mg/m(2) per day. EU on either schedule decreased 5-FU plasma clearance by 48 to 52-fold, prolonged the half-life to >5 h, and increased the percentage of 5-FU excreted in the urine from 2% to 64-66%. With EU, plasma fluoro-beta-alanine was not detected while urinary excretion was reduced to <1% of that seen with i.v. 5-FU alone. Marked increases in both plasma and urinary uracil were seen. Thymidylate synthase ternary complex formation was demonstrated in bone marrow mononuclear cells isolated 24 h after the first oral 5-FU dose; the average was 66.5% bound. Either a single 20-mg dose of EU given prior to or for 3 days around the oral 5-FU dose led to comparable effects on 5-FU pharmacokinetic parameters, and inhibition of dihydropyrimidine dehydrogenase and thymidylate synthase.
    Cancer Chemotherapy and Pharmacology 07/2003; 52(1):79-85. · 2.80 Impact Factor