Breast Cancer Cell Density: Imaging assay of the density- and context-dependence of small molecule perturbagen response in breast cancer cell lines. Dataset 1 of 3: Cell count and normalized growth rate inhibition values.

Project description:Introduction: Breast radiotherapy is currently â??one size fits allâ?? regardless of breast cancer subtype (eg. luminal, basal). However, recent clinical data suggests that radiation response may vary significantly among subtypes. Therefore, current practice leads to over- or under-treatment of women whose tumors are more or less radiation responsive. We hypothesized that this clinical variability may be due, in part, to differences in cellular radiation response. Methods: We exposed 16 biologically-diverse breast tumor cell lines to 0 or 5GY radiation. Microarray analysis was performed on RNA harvested from those cell lines. Samples were run in triplicate. Following quality assessment, differential gene expression analysis was performed using a two-way multiplicative linear mixed-effects model. A candidate radiation response biomarkers with biologically plausible role in radiation response, were identified and confirmed at the RNA and protein level with qPCR and Western blotting assays. Induction in human breast tumors was confirmed in 32 patients with paired pre- and post-radiation tumor samples using IHC and microarray analysis. Quantification of protein was performed in a blinded manner and included positive and negative controls. The objective of our study was to identify genomic determinants of radiation sensitivity using clinical samples as well as breast tumor cell lines. In order to identify differences in the radiation response gene expression profiles of specific breast cancer subtypes, we exposed 16 biologically-diverse breast tumor cell lines to 0 or 5GY radiation. Microarray analysis was performed on RNA harvested from those cell lines. Samples were run in triplicate. Following quality assessment, differential gene expression analysis was performed using a two-way multiplicative linear mixed-effects model. Candidate radiation response biomarker with a biologically plausible role in radiation response, were identified and confirmed at the RNA and protein level with qPCR and Western blotting assays. Induction of the genes of interest were further evaluated and confirmed in human breast tumors in 32 breast cancer patients with paired pre- and post-radiation tumor samples using IHC and microarray analysis assays.

Project description:Dioxin-like chemicals are well-known for their ability to upregulate expression of numerous genes via the AH receptor (AHR). However, recent transcriptomic analyses in several laboratories indicate that dioxin-like chemicals or AHR genotype itself also can downregulate levels of mRNAs encoded by numerous genes. The mechanism responsible for such downregulation is unknown. We hypothesized that microRNAs (miRNAs), which have emerged as powerful negative regulators of mRNA levels in several systems, might be responsible for mRNA downregulation in dioxin/AHR pathways. We conducted a thorough investigation to address the following questions: (1) does AHR genotype itself affect constitutive expression of microRNAs? (2) does TCDD affect microRNA levels and, if so, is this response dependent on the AHR? (3) does TCDD affect microRNA levels differently in animals that are sensitive to dioxin toxicity versus those that are dioxin-resistant? We used the Exiqon miRNA array platform as well as quantitative RT-PCR to measure miRNA levels in wildtype vs. Ahr-null mice. Treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in vivo caused few changes in miRNA levels in mouse livers and those changes that were statistically significant were of modest magnitude. AHR genotype had little effect on hepatic miRNA levels, either in constitutive expression or in response to TCDD M-bM-^@M-^S only a few miRNAs differed in expression between Ahr-null mice compared to mice with wildtype AHR. It is unlikely that mRNA downregulation by dioxins is mediated by miRNAs, nor are miRNAs likely to play a significant role in dioxin toxicity in adult mouse liver. Manuscript Submitted: Moffat ID, Boutros PC, Celius T, Pohjanvirta R & Okey AB. Micro-RNAs in rodent liver are refractory to dioxin treatment. Toxicological Sciences May, 2007. Keywords: miRNA expression, gene knockout, response to xenobiotics, genetic modification This was a two-factor, two-level design, the factors being genotype Ahr+/+ (WT) or Ahr-/- (KO) and treatment TCDD-treated (T) or vehicle control (C). Each total-RNA sample was separately labeled either with a Hy3- or a Hy5-fluorophore (Exiqon). Hy3- and Hy5-labeled samples were co-hybridized to an array. Dye-reversal was performed to eliminate dye bias. We tested 3 TCDD-treated and 3 control mice in the Ahr-/- groups and 4 TCDD-treated and 4 control mice in the Ahr+/+ groups. Technical replication of 1 TCDD-treated and 1 control mice in the Ahr-/- groups was performed. A loop design was used.

Dataset Information

Breast Cancer Cell Density: Imaging assay of the density- and context-dependence of small molecule perturbagen response in breast cancer cell lines. Dataset 3 of 3: Calculated dose-response metrics.

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