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Whole-blood samples from women exposed to hormone replacement therapy

ABSTRACT: The American Women’s Health Initiative study published in July 2002 caused considerable concern among hormone replacement therapy (HRT) users and prescribers in many countries. This study is an exploratory research comparing the genome wide expression profile in whole blood samples according to HRT use. Within the Norwegian Women and Cancer study, 100 postmenopausal women (50 HRT users and 50 non-HRT users) born between 1943 and 1949 with normal to high body mass index and no other medication use were selected. After total RNA extraction, amplification and labelling, the samples were hybridized together with a common reference (Universal human reference RNA, Stratagen) to Agilent Human 1A oligoarrays (G4110b, Agilent Technologies, Palo Alto, CA) containing 20,173 unique genes. Differentially expressed genes were used to build a classifier using the nearest shrunken centroids method (PAM). Then, we tested the significant changes in single genes by different methods like t-test, Significance Analysis of Microarrays (SAM) and Bayesian ANOVA analysis (BAM). Results did not reveal any distinct gene list which predicted accurately HRT exposure (error rate = 0.45). Classifier performance slightly improved (error rate = 0.29) including only women who were using continuous combined HRT treatment. According to the small amplitude of expression alterations observed after HRT use in whole blood, large sample sizes are needed to identify significant single genes differentially expressed. However, significant enrichments in biologic process of genes with small changes after HRT use were observed (e.g. receptor and transporter activities, immune response, frizzled signalling pathway, actin filament organization, glycogen metabolism). Keywords: gene expression profile and exposure

ORGANISM(S): Homo sapiens

PROVIDER: GSE3492 | GEO | 2005/10/25

SECONDARY ACCESSION(S): PRJNA93315

REPOSITORIES: GEO

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Project description:Whole blood rather than purified peripheral blood mononuclear cells is likely to become the prime tissue using expression microarrays for disease predication or prognosis however excess of globin mRNA may reduce probe detection sensitivity. In our study, we assessed whether whole-blood or globin-reduced RNA gives the most robust and sensitive results to detect small gene expression changes in response to hormone replacement therapy exposure. Each sample (N = 12) were hybridized according to 3 different protocols: no globin reduction (controls), globin reduction using peptid nucleic acids (PNA) and using magnetic beads in the GlobinClear kit from Ambion. Finally, 7 and 4 technical replicates were conducted in no globin reduction and PNA groups, respectively. Both globin reduction approaches were mostly efficient at reducing globin RNA from cRNA. Samples processed by GlobinClear kit gave a very distinct gene expression profiles from the controls while samples processed with PNA gave an intermediary profile closest to the non globin reduction group with a slight increased sensitivity of transcript detection but a loss of reproducibility. Overall, no sign of higher sensitivity in detection of gene expression changes followed by hormone exposure was observed after globin reduction which was therefore judged not beneficial. Keywords: Groups comparaison To assess effect of globin reduction protocols on gene expression from whole-blood, we selected 12 postmenopausal women (6 HRT users and 6 non-HRT users) who were not using other medication than HRT at the time of blood sampling and in order to cover a wide body mass index (BMI) range in both HRT and non HRT users. The samples were also selected to contain the highest concentration of total extracted RNA. Each sample was hybridized according to 3 different protocols: no globin reduction (controls), globin reduction using PNAs, globin reduction using magnetic beads in the GlobinClear™ kit from Ambion. The reproducibility of the globin reduction method compared to the non globin reduction approach was investigated for the PNA method only since this method was the most effective and specific. We planned to conduct 7 technical replicates in each group (i.e. no globin reduction and PNA groups). During amplification process with PNA, 4 samples failed to reverse transcript long fragment of mRNA certainly due to inhibitory contamination and these arrays were therefore excluded from our analyses. One sample (sample 34) was amplified with PNA twice the same day to study technical reproducibility without amplification date effect. Finally, a total of 47 arrays were conducted including 7 and 4 technical replicates in no globin reduction and PNA group, respectively.

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Whole-blood samples from women exposed to hormone replacement therapy

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