Unknown,Transcriptomics,Genomics,Proteomics

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Transcription profiling by array of human Acute Lymphobastic Leukemia xenografts in mouse to validate the mouse model

ABSTRACT: Pre-clinical models that effectively recapitulate human disease are critical for expanding our knowledge of cancer biology and drug resistance mechanisms. For haematological malignancies, the non-obese diabetic/severe combined immunodeficient (NOD/SCID) mouse is one of the most successful models to study paediatric acute lymphoblastic leukaemia (ALL). However, for this model to be effective for studying engraftment and therapy responses at the whole genome level, careful molecular characterisation is essential.Here, we sought to validate species-specific gene expression profiling in the high engraftment continuous ALL NOD/SCID xenograft. Using the human Affymetrix whole transcript platform we analysed transcriptional profiles from engrafted tissues without prior cell separation of mouse cells and found it to return highly reproducible profiles in xenografts from individual mice. The model was further tested with experimental mixtures of human and mouse cells, demonstrating that the presence of mouse cells does not significantly skew expression profiles when xenografts contain 90% or more human cells. In addition, we present a novel in silico and experimental masking approach to identify probes and transcript clusters susceptible to cross-species hybridisation.We demonstrate species-specific transcriptional profiles can be obtained from xenografts when high levels of engraftment are achieved or with the application of transcript cluster masks. Importantly, this masking approach can be applied and adapted to other xenograft models where human tissue infiltration is lower. This model provides a powerful platform for identifying genes and pathways associated with ALL disease progression and response to therapy in vivo.

ORGANISM(S): Homo sapiens

SUBMITTER: Amy Samuels

PROVIDER: E-MEXP-2648 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Glucocorticoids are critical components of combination chemotherapy regimens in pediatric acute lymphoblastic leukemia (ALL). The pro-apoptotic BIM protein is an important mediator of glucocorticoid-induced apoptosis in normal and malignant lymphocytes, while the anti-apoptotic BCL2 confers resistance. The signaling pathways regulating BIM and BCL2 expression in glucocorticoid-treated lymphoid cells remain unclear. In this study, pediatric ALL patient-derived xenografts (PDXs) inherently sensitive or resistant to glucocorticoids were exposed to dexamethasone in vivo. In order to understand the basis for differential in vivo glucocorticoid sensitivity of PDXs, microarray analysis of gene expression was carried out on 5 each of dexamethasone-sensitive and resistant PDXs . This provided a global understanding of dexamethasone-induced signaling cascades in ALL cells in vivo, and especialy identified the genes that are involved in transducing the apoptotic signal, upstream of BIM/BCL2 dynamic interactions. ALL xenograft cells were inoculated by tail-vein injection into NOD/SCID mice, and engraftment was monitored weekly. When >70% %huCD45+ engraftment in the peripheral blood was apparent, which occurred 8-10 weeks post-transplantation, mice were treated with either dexamethasone (15 mg/kg) or vehicle control by intra-peritoneal (IP) injection, and culled at 8 hours following the treatment. Cell suspensions of spleens were prepared and mononuclear cells enriched to >97% human by density gradient centrifugation. RNA was extracted using the RNeasy Mini Kit (QIAGEN, Valencia, CA, USA), and RNA samples with integrity number (RIN) > 8.0 were amplified and hybridized onto Illumina HumanWG-6 v3 Expression BeadChips (6 samples/chip). All chips (with associated reagents) were purchased from Illumina, and scanned on the Illumina BeadArray Reader according to the manufacturer’s instructions. Microarray data were analyzed using the online modules in GenePattern. 10 xenografts were derived from patients of 5 dexamethasone-good responder and 5 dexamethasone-poor responder. Each xenograft was innoculated into 5-6 mice, and treated with dexamethasone (15 mg/kg) or vehicle control. In total spleen-harvest xenograft samples from 58 mice were analyzed using microarray.

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Transcription profiling by array of human Acute Lymphobastic Leukemia xenografts in mouse to validate the mouse model

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