Unknown,Transcriptomics,Genomics,Proteomics

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Transcriptional profiling of MMTV-tTA/TOP-ICN1 tumor derived cell lines comparing untreated (ICN1-On) cells to 24-hour doxcycline treated (ICN1-Off) samples

ABSTRACT: NOTCH activation has been recently implicated in human basal-like breast cancers associated with a poor prognosis. To address the role of Notch1 in mammary transformation and mammary tumor initiating cell activity, we developed a doxycycline-regulated model of Notch1-mediated mammary transformation. These mice develop mammary adenocarcinomas that express cytokeratin (CK) 8/18 and contain rare cells that also express keratin 14. In vivo limiting dilution analyses reveal that these mammary tumors exhibit functional heterogeneity and harbor a rare (1/2978) mammary tumor initiating cell population. Using this dox-regulated Notch1 mammary tumor model, we demonstrate that Notch1 inhibition results in mammary tumor regression in vivo and prevents disease recurrence in 4 of 6 tumors tested. Consistent with the in vivo data, Notch1 inhibition reduces mammary tumorsphere forming activity in vitro. Using doxycycline-responsive tumor derived cell lines, we also identify the embryonic stem cell transcription factor Nanog as a novel Notch1-regulated gene in mammospheres. These data indicate that Notch1 contributes to mammary tumor initiating activity and raises the possibility that NOTCH therapeutics may have efficacy in human basal-like breast cancers associated with NOTCH activation. Primary mammary tumors were isolated from two different MMTV-tTA/TOP-ICN1 transgenic mice, minced, enzymatically digested and converted to culture. To identify changes in gene expression in response to ICN1 suppression, tumor-derived cell lines 8534 and 8542 were left untreated (8534-Untreated; 8542-Untreated) or treated with 2ug/ml doxycycline for 24 hours (8534-Dox; 8542-Dox). Cells were collected by scraping and total RNA was isolated, followed by real-time PCR validation of NOTCH1 target gene modulation. RNA samples were further hybridized to Affymetrix mouse genome 430A2.0 arrays.

ORGANISM(S): Mus musculus

SUBMITTER: Matthew Simmons

PROVIDER: E-GEOD-34146 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Cyclin C was cloned as a growth-promoting G1 cyclin1,2, and several studies postulated a role for cyclin C in driving cell proliferation3-8 . Moreover, cyclin C, together with its kinase partner, the cyclin-dependent kinase CDK8, is believed to represent an essential component of basal transcriptional machinery where it globally represses gene expression9-13. However, the function of cyclin C in vivo has never been addressed. Here we show that in the living organism cyclin C acts as a haploinsufficient tumor suppressor, through its function of controlling Notch1 oncogene levels. Cyclin C activates an “orphan” CDK19 kinase14, as well as CDK8 and CDK3. These cyclin C-CDK complexes phosphorylate Notch1 intracellular domain (ICN1), which allows binding of ICN1 to Fbw7 and triggers ICN1 polyubiquitination. Genetic ablation of cyclin C blocks ICN1 phosphorylation, disrupts Fbw7 binding, and decreases ICN1 ubiquitination in vivo, thereby strongly elevating ICN1 levels in several compartments of cyclin C knockout mice. Cyclin C was cloned as a growth-promoting G1 cyclin1,2, and several studies postulated a role for cyclin C in driving cell proliferation3-8 . Moreover, cyclin C, together with its kinase partner, the cyclin-dependent kinase CDK8, is believed to represent an essential component of basal transcriptional machinery where it globally represses gene expression9-13. However, the function of cyclin C in vivo has never been addressed. Here we show that in the living organism cyclin C acts as a haploinsufficient tumor suppressor, through its function of controlling Notch1 oncogene levels. Cyclin C activates an “orphan” CDK19 kinase14, as well as CDK8 and CDK3. These cyclin C-CDK complexes phosphorylate Notch1 intracellular domain (ICN1), which allows binding of ICN1 to Fbw7 and triggers ICN1 polyubiquitination. Genetic ablation of cyclin C blocks ICN1 phosphorylation, disrupts Fbw7 binding, and decreases ICN1 ubiquitination in vivo, thereby strongly elevating ICN1 levels in several compartments of cyclin C knockout mice.

Dataset Information

Transcriptional profiling of MMTV-tTA/TOP-ICN1 tumor derived cell lines comparing untreated (ICN1-On) cells to 24-hour doxcycline treated (ICN1-Off) samples

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