Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression alterations in human colon cancer xenograft treated with anti-VEGF antibody

ABSTRACT: Recent randomized clinical trial revealed the additional effect of bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor (VEGF)-A, to conventional chemotherapy on survival of patients with metastatic colorectal cancer. However, a number of preclinical reports indicate resistant mechanisms to anti-angiogenic therapy in several tumor models. We investigated the phenotypic alterations of colorectal cancer xenograft during antiangiogenic therapy. TK-4, a solid tumor strain derived from human colon cancer, was orthotopically implanted into cecal walls of nude mice and treated with anti-VEGF antibody or control IgG for 35 days. Gene expression was analyzed using microarrays (Human Gene 1.0ST Array, Affymetrix).

ORGANISM(S): Homo sapiens

SUBMITTER: Hirotoshi Kikuchi

PROVIDER: E-GEOD-47087 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Bevacizumab induces glioblastoma resistance in two in vivo xenograft models. Two cell lines were developed with acquired resistance to bevacizumab. Gene expression difference were analyzed between treated and untreated tumors. Purpose: Antiangiogenic therapy reduces vascular permeability and delays progression but may ultimately promote an aggressive treatment-resistant phenotype. The aim of the present study was to identify mechanisms responsible for glioblastoma resistance to antiangiogenic therapy. Experimental Design: Glioma stem cell (GSC) NSC11 and U87 cell lines with acquired resistance to bevacizumab were developed from orthotopic xenografts in nude mice treated with bevacizumab. Genome-wide analyses were used to identify changes in tumor subtype and specific factors associated with resistance. Results: Mice with established parental NSC11 and U87 cells responded to bevacizumab, whereas glioma cell lines derived at the time of acquired resistance to anti-VEGF therapy were resistant to bevacizumab and did not have prolongation of survival compared to untreated controls. Gene expression profiling comparing anti-VEGF therapy-resistant cell lines to untreated controls demonstrated an increase in genes associated with a mesenchymal origin, cellular migration/invasion, and inflammation. Gene Set Enrichment Analysis (GSEA) demonstrated that bevacizumab-treated tumors showed a highly significant correlation to published mesenchymal gene signatures. Mice bearing resistant tumors showed significantly greater infiltration of myeloid cells in NSC11 and U87 resistant tumors. Invasion-related genes were also upregulated in both NSC11 and U87 resistant cells, which had higher invasion rates in vitro compared with their respective parental cell lines. Conclusions: Our studies identify multiple pro-inflammatory factors associated with resistance and identify a proneural-to-mesenchymal transition (PMT) in tumors resistant to antiangiogenic therapy. Glioma cell lines were injected into the caudate of nude mice and were allowed to grow untreated (samples labeled control) or were treated with 10 mg/kg IP twice weekly with bevacizumab (samples labeled Avastin). At the time of animal death, tumor tissue from the mouse was removed, and RNA was isolated and analyzed using gene expression. U87R and NSC11R represent cells resistant to bevacizumab (Avastin).

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Gene expression alterations in human colon cancer xenograft treated with anti-VEGF antibody

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