Spontaneous Nf1 deletion and recurrent copy number alterations in mammary tumorigenesis
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
SUBMITTER: John Schimenti
PROVIDER: E-GEOD-37607 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Breast cancer is the most prevalent cancer in women 1, and most cases are believed to have a sporadic, rather than heritable basis 2. To identify breast cancer driver genes, we exploited the C3H-Mcm4Chaos3/Chaos3 (“Chaos3”) mouse model that, by virtue of bearing a defective DNA replicative helicase subunit that causes elevated genomic instability (GIN), sustains somatic alterations ultimately causing mammary adenocarcinomas 6. Array Comparative Genomic Hybridization (aCGH) analysis of Chaos3 mammary tumors revealed recurrent copy number alterations (CNAs), most notably deletion of the Neurofibromin 1 (Nf1) tumor suppressor gene in all cases. NF1, a negative regulator of RAS, is traditionally recognized for its role in driving the development of neurofibromas in the context of the human disease Neurofibromatosis Type 1, but not breast cancer. Genomic DNA from tumor and reference samples were hybridized to NimbleGen 3x720K mouse CGH arrays. Two reference samples were used independently. CNAs were visualized using Nimblegen, IGV, and KCsmart software 32. Select genes were validated via qPCR. Critical regions within each Chaos3 CNA were identified as the region with the greatest overlap across multiple Chaos3 tumors.
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Project description:Breast cancer is the most prevalent cancer in women, and most cases are believed to have a sporadic, rather than heritable basis. Therefore, a major challenge in cancer research is to determine the underlying genomic alterations leading to carcinogenesis and malignancy, and then use this information for personalized therapies. Genomic studies of human cancers that aim to identify causative mutations are complicated by the prevalence of passenger mutations, genetic heterogeneity, and the diversity of breast cancer etiologies and tumor subtypes. Mouse cancer models are powerful for untangling the genomic basis of cancers because genetic and phenotypic variation can be eliminated or controlled. To identify genes contributing to mammary tumorigenesis, we exploited the C3H-Mcm4Chaos3/Chaos3 (“Chaos3”) mouse model that, by virtue of bearing a defective DNA replicative helicase subunit that causes elevated genomic instability (GIN), sustains somatic alterations ultimately causing mammary adenocarcinomas. Genomic analysis of Chaos3 mammary tumors revealed recurrent copy number alterations (CNAs) of specific genomic regions, most notably deletion of the Neurofibromin 1 (Nf1) tumor suppressor gene in all cases. NF1, a negative regulator of RAS, is traditionally recognized for its role in driving the development of neurofibromas in the context of the human disease Neurofibromitosis but not breast cancer. We observed elevated RAS activation and increased sensitivity of both Chaos3 and human Nf1-mutated breast cancer lines to MAPK and/or PI3K/AKT pathway inhibitors. We also found striking overlap between Chaos3 CNAs and human breast cancer CNA data curated in public genomic databases, including Nf1 deletion. Together, our results indicate that spontaneous NF1 loss can drive breast cancer and suggests a potential therapeutic strategy in that subset of patients. reference x sample
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Project description:Breast cancer is the most prevalent cancer in women, and most cases are believed to have a sporadic, rather than heritable basis. Therefore, a major challenge in cancer research is to determine the underlying genomic alterations leading to carcinogenesis and malignancy, and then use this information for personalized therapies. Genomic studies of human cancers that aim to identify causative mutations are complicated by the prevalence of passenger mutations, genetic heterogeneity, and the diversity of breast cancer etiologies and tumor subtypes. Mouse cancer models are powerful for untangling the genomic basis of cancers because genetic and phenotypic variation can be eliminated or controlled. To identify genes contributing to mammary tumorigenesis, we exploited the C3H-Mcm4Chaos3/Chaos3 (“Chaos3”) mouse model that, by virtue of bearing a defective DNA replicative helicase subunit that causes elevated genomic instability (GIN), sustains somatic alterations ultimately causing mammary adenocarcinomas. Genomic analysis of Chaos3 mammary tumors revealed recurrent copy number alterations (CNAs) of specific genomic regions, most notably deletion of the Neurofibromin 1 (Nf1) tumor suppressor gene in all cases. NF1, a negative regulator of RAS, is traditionally recognized for its role in driving the development of neurofibromas in the context of the human disease Neurofibromitosis but not breast cancer. We observed elevated RAS activation and increased sensitivity of both Chaos3 and human Nf1-mutated breast cancer lines to MAPK and/or PI3K/AKT pathway inhibitors. We also found striking overlap between Chaos3 CNAs and human breast cancer CNA data curated in public genomic databases, including Nf1 deletion. Together, our results indicate that spontaneous NF1 loss can drive breast cancer and suggests a potential therapeutic strategy in that subset of patients.
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Project description:Tumor recurrence represents a significant clinical challenge in the treatment and management of breast cancer. To investigate whether copy number aberrations (CNAs) facilitate the re-emergence of tumor growth from residual disease we performed array comparative genomic hybridization (aCGH) on primary and recurrent mammary tumors from an inducible mouse model of type-I insulin-like growth factor receptor (IGF-IR) driven breast cancer. This genome-wide analysis revealed primary and recurrent tumors harbored distinct copy number aberrations (CNAs) with relapsed tumors containing an increased number of gene-level gains and losses. Remarkably, CNAs detected in primary tumors were largely devoid of annotated cancer genes while the vast majority of recurrent tumors harbored at least one CNA containing a known oncogene or tumor suppressor. Specifically, a subset of recurrent tumors carried gains at 6qA2 and 9qA2 which encode the Met and Yap1 oncogenes respectively. The most frequent CNA detected was a focal deletion at 4qC5 involving the Cdkn2a and Cdkn2b tumor suppressor genes. Integrative analysis revealed positive correlations between gene copy number and mRNA expression suggesting Met, Yap1 and Cdkn2a/b may serve as potential driver genes that promote tumor recurrence. Together, these findings indicate that tumor recurrence is facilitated by the acquisition of CNAs with oncogenic potential and provide a framework to dissect the molecular mechanisms that mediate tumor escape from dormancy.
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Project description:Tumor formation is in part driven by copy number alterations (CNAs), which can be measured using array Comparative Genomic Hybridization (aCGH). Identifying regions of DNA that are gained or lost in a significant fraction of tumor samples can facilitate identification of genes possibly related to the development of cancer. Until now, no method has been described that provides a statistical framework in which these regions can be identified without prior discretization of the aCGH data. Kernel Convolution - a Statistical Method for Aberrant Region deTection (KC-SMART) is a new approach which inputs continuous aCGH data to identify regions that are significantly aberrant across an entire tumor set. KC-SMART uses kernel convolution to generate a Kernel Smoothed Estimate (KSE) of CNAs across the genome, aggregated over all tumors. By varying the width of the kernel function, a scale space is created which enables the detection of aberrations of varying size. In an analysis of 89 human sporadic breast tumors KC-SMART performs better than a previously published method, STAC. Our method not only identified aberrations that are strongly associated with clinical parameters, but also showed stronger enrichment for known cancer genes in the detected regions. Furthermore, KC-SMART identifies 18 aberrant regions in mammary tumors from p53 conditional knock-out mice. These regions, combined with gene expression micro-array data, point to known cancer genes and novel candidate cancer genes. Keywords: Comparative Genomic Hybridization, aCGH
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Project description:BACKGROUND: The NF1 tumor suppressor gene is the main negative regulator of the RAS pathway and is frequently mutated in various cancers. Women with Neurofibromatosis Type I (NF1) – a tumor predisposition syndrome caused by a germline NF1 mutation – have an increased risk of developing aggressive breast cancer with poorer prognosis. The mechanisms by which NF1 mutation leads to breast cancer tumorigenesis are not well understood. Therefore, the objective of this work was to identify stromal alterations before tumor formation that result in the increased risk and poorer outcome seen among NF1 patients with breast cancer. METHODS: To accurately model the germline monoallelic NF1 mutations in NF1 patients, we utilized an Nf1-deficient rat model with accelerated mammary development and develops highly penetrant breast cancer. RESULTS: We identified increased collagen content in Nf1-deficient rat mammary glands before tumor formation that correlated with age of tumor onset. Additionally, gene expression analysis revealed that Nf1-deficient rat mammary mature adipocytes have increased collagen expression and shifted to a fibroblast and preadipocyte expression profile. This alteration in lineage commitment was also observed with in vitro differentiation but flow cytometry analysis did not show a change mammary adipose-derived mesenchymal stem cell abundance. CONCLUSION: Collectively, these studies uncovered the previously undescribed role of Nf1 in mammary collagen deposition and regulating adipocyte differentiation. In addition to unraveling the mechanism of tumor formation, further investigation of adipocytes and collagen modifications in preneoplastic mammary gland will create a foundation for developing early detection strategies of breast cancer among NF1 patients.
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2010-04-14 | E-GEOD-21259 | biostudies-arrayexpress