Unknown,Transcriptomics,Genomics,Proteomics

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Silencing of Irf7 pathways in breast cancer cells promotes bone metastasis through immune escape mechanisms

ABSTRACT: Breast cancer metastasis to bone is a critical determinant of long-term survival after treatment of primary tumors. We used a mouse model of spontaneous bone metastasis to determine new molecular mechanisms. Differential transcriptome comparisons of primary and metastatic tumor cells revealed that a substantial set of genes suppressed in bone metastases were highly enriched for promoter elements for the type I interferon (IFN) regulatory factor, Irf7, itself suppressed in mouse and human metastases. The critical function of the Irf7 pathway was demonstrated by restoration of exogenous Irf7 or systemic interferon administration, which significantly reduced bone metastases and prolonged metastasis free survival. Using mice deficient in the type I receptor (Ifnar1-/-) or mature B, T and NK cell responses (NOD Scid IL-2rÎ³-/- mice) we demonstrated that Irf7-driven suppression of metastasis was reliant on IFN signaling to host immune cells. Metastasis suppression correlated with decreased accumulation of myeloid-derived suppressor cells and increased CD4++, CD8 T cells and NK cells in the peripheral blood and was reversed by depletion of CD8+ cells and NK cells. Clinical importance of our findings was demonstrated as increased primary tumor Irf7 expression predicted prolonged bone and lung metastasis-free survival. Thus we report for the first time, a novel innate immune pathway, intrinsic to breast cancer cells, whose suppression in turn restricts systemic immunosurveillance to enable metastasis. This pathway may constitute a novel therapeutic target for restricting breast cancer metastases. Comparison of basal gene expression in breast cancer 4T1.2 cell line stably transfected using the pMSCV retroviral expression vector system with IRF7 or the base vector. Three independent experiments were performed comparing the IRF7 expressing cells to the base vector cells

ORGANISM(S): Mus musculus

SUBMITTER: Sam Forster

PROVIDER: E-GEOD-37828 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Using a multiorgan metastasis model of human NSCLC cells (ACC-LC319/bone2) in NK cell-depleted SCID mice, we attempted to identify genes involved in the organ-selective nature of lung cancer-metastasis process, especially bone metastasis. Genome-wide gene expression profile of 15 metastatic lesions from three organs (bone, lung and liver) in this mouse model revealed lot of genes that seemed to reflect the organ specificity of metastatic cells. Among bone-specifically-expressed genes, dozen of genes involved in cell adhesion, cytoskeleton/cell motility, extracellular matrix remodeling, and cell-cell signaling. The upregulation of 11 genes, some of them were either previously reported to be involved in metastatic characteristics, were confirmed by quantitative RT-PCR. The high ability for bone metastasis human lung adenocarcinoma cell line ACC-LC319/bone2 was established in our laboratory from the parental cell line ACC-LC319 (a kind gift from Dr T. Takahashi, Nagoya University, Nagoya, Japan). ACC-LC319 cells with low capacity of bone metastatic ability were selected in vivo for two cycles in bone metastasis mouse models. After two cycles of selection, the derivative cell line designated as ACC-LC319/bone2 showed increased bone metastatic ability compared to parental cell line (Otsuka S., Oncol Res 2009). In this multiorgan metastasis model, SCID mice were depleted NK cells, and two days later, these mice were intravenously injected 1x10^6 cells. The mice were followed up for clinical symptoms and signs of metastases, and were sacrificed on day 34 after tumor inoculation. Metastastic tissues in lung, liver and bone were collected and snap frozen in liquid nitrogen then keep at -80C until cryosection. Laser microbeam microdissection was used to capture pure population of cancer cells in each organ as well as mouse normal tissues in corresponding organ (i.e. the surrounding normal tissues with no microscopic metastasis). Totally, there were 19 samples, including one sample for metastases in each organ (bone, lung and liver) in five mice (i.e., 15 samples); one for each normal mouse tissue (i.e.,three samples); and one for the in vitro cell line (ACC-LC319/bone 2). DNA microarray were performed using Agilent platform, and the gene expression profile of metastases in bone were compared with the gene expression profile of metastases in other two organs (lung, liver). Those genes whose expression in mouse normal tissues was above the cut off value were excluded. The expression of genes in the in vitro cells was used as the universal normalization for the in vivo genes expression.

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Silencing of Irf7 pathways in breast cancer cells promotes bone metastasis through immune escape mechanisms

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