Unknown,Transcriptomics,Genomics,Proteomics

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Control shRNA- vs. obscurin shRNA-expressing MCF10A cells

ABSTRACT: Obscurins (~70-870kDa), encoded by the single OBSCN gene, are cytoskeletal proteins originally identified in striated muscles with structural and regulatory roles. Recently, analysis of 13,023 genes in breast and colorectal cancers identified OBSCN as one of the most frequently mutated genes, implicating it in cancer formation. Herein, we studied the expression profile of obscurins in breast, colon and skin cancer cell lines, and their involvement in cell survival. Immunoblot analysis demonstrated significant reduction of obscurins in cancer cells, resulting from decreased mRNA levels and/or the presence of mutant transcripts. In normal epithelium, obscurins localize in cytoplasmic puncta, the cell membrane and the nucleus. Accordingly, subcellular fractionation demonstrated the presence of two novel nuclear isoforms of ~110 and ~120kDa. Non-tumorigenic MCF10A breast epithelial cells stably transduced with shRNAs targeting giant obscurins exhibited increased viability (~30%) and reduced apoptosis (~20%) following exposure to the DNA damaging agent, etoposide. cDNA microarrays followed by Gene Ontology profiling indicated a substantial number of transcripts related to apoptosis and survival are differentially regulated upon obscurin knock-down. Quantitative RT-PCR further indicated that the anti-apoptotic genes BAG-4 and HAX-1 were up-regulated (1.5 and 1.4 fold, respectively), whereas initiator caspase-9 and death caspase-3 transcripts were down-regulated (0.8 and 0.6 fold, respectively). Our findings are the first to pinpoint critical roles for obscurins in cancer development by contributing to the regulation of cell survival. Two-condition experiment: control shRNA- vs. obscurin shRNA-expressing MCF10A cells exposed to 150 uM etoposide. 3 independent replicates per condition.

ORGANISM(S): Homo sapiens

SUBMITTER: Aikaterini Kontrogianni-Konstantopoulos

PROVIDER: E-GEOD-35494 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Bmi-1 and Mel-18 are close structural homologues that belong to the polycomb group (PcG) of transcriptional regulators of homeotic gene expression in development. They are believed to stably maintain repression of gene expression by altering the state of chromatin at specific promoters. A number of clinical and experimental observations have also implicated Bmi-1 in tumorigenesis and stem cell maintenance. Bmi-1 overexpression or amplification has been observed in a number of human malignancies, particularly in B-cell lymphomas, medulloblastomas and breast cancer. We report here that shRNA-mediated knock-down of either Bmi-1 or Mel-18 in human medulloblastoma DAOY cells results in the inhibition of proliferation, loss of clonogenic survival and anchorage-independent growth, and suppression of xenograft tumor formation in nude mice. Furthermore, overexpression of both Bmi-1 and Mel-18 significantly increased clonogenic survival of Rat1 fibroblasts. In contrast, stable downregulation of Bmi-1 or Mel-18 alone did not affect the growth of SK-OV-3 or U2OS cancer cell lines or normal human WI38 fibroblasts. Gene expression analysis of shRNA-expressing DAOY cells has demonstrated a significant overlap in the Bmi-1- and Mel-18-regulated genes and revealed novel gene targets under their control. Taken together, these results suggest that Bmi-1 and Mel-18 might have overlapping functions in human tumorigenesis. Experiment Overall Design: DAOY cells were transduced with the indicated lentiviral shRNA and stable cell lines were generated by selection in puromycin (1 Âµg/ml). 2 x 105 cells of each stable cell line were plated onto 60 mm dishes in triplicates and harvested 4 days later. Triplicate total RNA samples from shRNA-expressing and mock-transduced DAOY cells were isolated using affinity resin (Qiagen RNeasy Mini Kit, Qiagen AG). RNA Integrity and purity were assessed with the RNA 6000 Nano LabChip system on Bioanalyzer 2100 (Agilent Technologies). Gene array analysis was conducted at the Genomics Factory at Novartis PHARMA AG, Basel, Switzerland using Gene Chip Human Genome 133 2.0 Plus Expression Array (Affymetrix Inc.).

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Control shRNA- vs. obscurin shRNA-expressing MCF10A cells

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