Biomedical subjects

Michael A Damore

Publications and source records attributed to Michael A Damore.

4 recordsLinked to original sources

PubMed2005

Use of a mixed tissue RNA design for performance assessments on multiple microarray formats.

The comparability and reliability of data generated using microarray technology would be enhanced by use of a common set of standards that allow accuracy, reproducibility and dynamic range assessments on multiple formats. We designed and tested a complex biological reagent for performance measurements on three commercial oligonucleotide array formats that differ in probe design and signal measurement methodology. The reagent is a set of two mixtures with different proportions of RNA for each of four rat tissues (brain, liver, kidney and testes). The design provides four known ratio measurements of >200 reference probes, which were chosen for their tissue-selectivity, dynamic range coverage and alignment to the same exemplar transcript sequence across all three platforms. The data generated from testing three biological replicates of the reagent at eight laboratories on three array formats provides a benchmark set for both laboratory and data processing performance assessments. Close agreement with target ratios adjusted for sample complexity was achieved on all platforms and low variance was observed among platforms, replicates and sites. The mixed tissue design produces a reagent with known gene expression changes within a complex sample and can serve as a paradigm for performance standards for microarrays that target other species.

Animals↗

PubMed2005

HER-2 overexpression differentially alters transforming growth factor-beta responses in luminal versus mesenchymal human breast cancer cells.

INTRODUCTION: Amplification of the HER-2 receptor tyrosine kinase has been implicated in the pathogenesis and aggressive behavior of approximately 25% of invasive human breast cancers. Clinical and experimental evidence suggest that aberrant HER-2 signaling contributes to tumor initiation and disease progression. Transforming growth factor beta (TGF-beta) is the dominant factor opposing growth stimulatory factors and early oncogene activation in many tissues, including the mammary gland. Thus, to better understand the mechanisms by which HER-2 overexpression promotes the early stages of breast cancer, we directly assayed the cellular and molecular effects of TGF-beta1 on breast cancer cells in the presence or absence of overexpressed HER-2. METHODS: Cell proliferation assays were used to determine the effect of TGF-beta on the growth of breast cancer cells with normal or high level expression of HER-2. Affymetrix microarrays combined with Northern and western blot analysis were used to monitor the transcriptional responses to exogenous TGF-beta1 in luminal and mesenchymal-like breast cancer cells. The activity of the core TGF-beta signaling pathway was assessed using TGF-beta1 binding assays, phospho-specific Smad antibodies, immunofluorescent staining of Smad and Smad DNA binding assays. RESULTS: We demonstrate that cells engineered to over-express HER-2 are resistant to the anti-proliferative effect of TGF-beta1. HER-2 overexpression profoundly diminishes the transcriptional responses induced by TGF-beta in the luminal MCF-7 breast cancer cell line and prevents target gene induction by a novel mechanism that does not involve the abrogation of Smad nuclear accumulation, DNA binding or changes in c-myc repression. Conversely, HER-2 overexpression in the context of the mesenchymal MDA-MB-231 breast cell line potentiated the TGF-beta induced pro-invasive and pro-metastatic gene signature. CONCLUSION: HER-2 overexpression promotes the growth and malignancy of mammary epithelial cells, in part, by conferring resistance to the growth inhibitory effects of TGF-beta. In contrast, HER-2 and TGF-beta signaling pathways can cooperate to promote especially aggressive disease behavior in the context of a highly invasive breast tumor model.

Blotting, Northern↗

PubMed2003

BACE1 (beta-secretase) knockout mice do not acquire compensatory gene expression changes or develop neural lesions over time.

The formation of Alzheimer's Abeta peptide is initiated when the amyloid precursor protein (APP) is cleaved by the enzyme beta-secretase (BACE1); inhibition of this cleavage has been proposed as a means of treating Alzheimer's disease. (AD) We have previously shown that young BACE1 knockout mice (BACE1 KO) do not generate Abeta but in other respects appear normal. Here we have extended this analysis to include both gene expression profiling and phenotypic assessment of older BACE1 KO animals to evaluate the impact of chronic Abeta deficiency. We did not detect global compensatory changes in neural gene expression in young BACE1 KO mice. In particular, expression of the beta-secretase homolog BACE2 was not upregulated. Furthermore, we found no structural alterations in any organ, including all central and peripheral neural tissues, of BACE1 KO mice up to 14 months of age. Aged BACE1 KO mice engineered to overexpress human APP (BACE1 KO/APPtg) did not develop amyloid plaques. These data provide evidence that neither beta-secretase nor Abeta plays a vital role in mouse physiology and that chronic beta-secretase inhibition could be a useful approach in treating AD.

Amyloid Precursor Protein Secretases↗

PubMed2002

Genes expressed during the IFN gamma-induced maturation of pre-B cells.

Interferon-gamma (IFN gamma) exerts diverse responses in B cell development ranging from growth arrest and apoptosis to proliferation and differentiation. IFN gamma stimulates murine 70Z/3 pre-B cells to express surface immunoglobulin (Ig) and this system serves as a useful model for the pre-B to immature B cell transition in B cell development. To analyze this developmental transition, we used a PCR-based subtractive hybridization in combination with miniarray screening to identify differentially-expressed genes in IFN gamma-stimulated compared with unstimulated 70Z/3 pre-B cells. The majority (44%) of the differentially-expressed genes obtained were known IFN gamma-inducible. These included multiple isolates from each of three multi-gene families, including two guanylate-binding protein (47 and 67kDa GBP) families of GTPases and the hematopoietic IFN gamma-inducible nuclear protein family (HIN-200). These multiple isolates of genes comprised the majority of the total isolated and sequenced clones. Other known IFN gamma-induced genes in this group included Ig kappa light chain and Ly-6, as well as genes with functions in antigen processing, cellular regulation, and cytoskeletal organization. Another 36% of the genes identified were previously known, but not known to be IFN gamma-inducible (e.g. pre-B cell enhancing factor, PBEF). The remaining 20% of the IFN gamma-induced isolates did not match entries in Genbank, and thus, may represent novel genes involved in IFN gamma responses and/or in the pre-B to immature B cell transition. Overall, the majority of the individual genes isolated were either not known to be IFN gamma responsive or were not previously known.

Animals↗