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Gene expression profiles of MLL-AF4 acute lymphoblastic leukaemia blasts retrieved from central nervous system and spleen

ABSTRACT: Purpose: To investigate metabolic adaptation of leukaemia in two different microenvironments: central nervous system and spleen Methods: The SEM (MLL-AF4) cell-line representing a high-risk subtype was used. Cells were transplanted into immunodeficient mice. CNS tropism was demonstrated and blasts invaded the leptomeninges in a timeframe ranging from 4 to 5 weeks. At experimental endpoint, blasts were retrieved from the CNS and periphery (spleen), and their gene expression profiles were compared using RNA-sequencing. The raw reads were pre-processed with Cutadapt v.1.5 and Sickle v.0.940 software. Transcript expression quantification was performed using Kallisto v.0.42.4 software against combined human and mouse transcriptomes, Ensembl GRCh38.79 and GRCm38.78, respectively. Read counts related to human transcripts were collected, rounded, and summarized into gene specific read counts. Gene-based differential expression analysis was done with DESeq2 R-package. Preprocessed RNA expression data from RNA sequencing was analysed further using single sample gene set enrichment analysis (ssGSEA). Results: The human SEM cells’ gene expression profiles clustered according to site of colonization in the transplanted mice; CNS versus spleen. The top differentially expressed genes were associated with cellular metabolism or stress responses. ssGSEA analysis identified positive correlation of lipid and lipoprotein metabolism signatures in CNS-derived cells, with particular propensity towards fatty acid synthesis. On the other hand, oxidative phosphorylation processes, linked to fatty acid degradation, were negatively correlated with CNS involvement and enriched in SEM cells from the spleen of transplanted mice. Conclusions: We demonstrate that leukaemic cells undergo widespread dynamic rewiring of metabolism when switching from bone marrow to CNS microenvironments, resulting in altered therapeutic vulnerabilities. We observed a strong fatty-acid synthesis signature in CNS leukaemia, highlighting Stearoyl-CoA desaturase (SCD1) as a key player.

ORGANISM(S): Homo sapiens

PROVIDER: GSE135113 | GEO | 2020/07/08

REPOSITORIES: GEO

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Project description:Purpose: To investigate metabolic adaptation of leukaemia in two different microenvironments: central nervous system and spleen Methods: The REH (TEL-AML1) cell line representing a standard-risk subtype was used. Cells were transplanted into immunodeficient mice. CNS tropism was demonstrated and ALL blasts invaded the leptomeninges in a timeframe ranging from 4 to 5 weeks. At experimental endpoint, blasts were retrieved from the CNS and periphery (spleen), and their gene expression profiles were compared using RNA-sequencing. The raw reads were pre-processed with Cutadapt v.1.5 and Sickle v.0.940 software. Transcript expression quantification was performed using Kallisto v.0.42.4 software against combined human and mouse transcriptomes, Ensembl GRCh38.79 and GRCm38.78, respectively. Read counts related to human transcripts were collected, rounded, and summarized into gene specific read counts. Gene-based differential expression analysis was done with DESeq2 R-package. Preprocessed RNA expression data from RNA sequencing was analysed further using single sample gene set enrichment analysis (ssGSEA). Results: The human REH cells’ gene expression profiles clustered according to site of colonization in the transplanted mice; CNS versus spleen. Top differentially expressed genes were associated with cellular metabolism or stress responses. ssGSEA analysis identified positive correlation of lipid and lipoprotein metabolism signatures in CNS-derived cells, with particular propensity towards fatty acid synthesis. On the other hand, oxidative phosphorylation processes, linked to fatty acid degradation, were negatively correlated with CNS involvement and enriched in REH cells from the spleen of transplanted mice. Conclusions: We demonstrate that leukaemic cells undergo widespread dynamic rewiring of metabolism when switching from bone marrow to CNS microenvironments, resulting in altered therapeutic vulnerabilities. We observed a strong fatty-acid synthesis signature in CNS leukaemia, highlighting Stearoyl-CoA desaturase (SCD1) as a key player.

Project description:Background. Flow cytometry (FCM) identifies leukemic blasts in cerebrospinal fluid (CSF) in approximately 30% of children with acute lymphoblastic leukemia (ALL), whereas conventional cytospin preparations frequently miss such involvement. <br>Procedure. To explore biological properties of leukemic cells that migrate into central nervous system (CNS), we compared gene expression profiles of leukemic cells from 26 patients with CNS involvement and 138 patients without CNS leukemia as determined by FCM and/or cytospin preparations. Results were validated by real-time quantitative PCR (qPCR). <br>Results. We found the cysteine endopeptidase legumain (LGMN) that plays a role in hydrolysis of proteins and small molecules to be significantly differentially expressed between FCM+ and FCM- B-cell precursor (BCP) ALL patients. When LGMN expression was validated by qPCR it stayed differentially expressed between FCM+ and FCM- BCP-ALL patients (P=0.006), and also between FCM+ and cytospin-negative BCP-ALL patients (P=0.01). In multivariate regression analysis including sex, age and WBC, LGMN expression levels above population median were associated with an odds ratio of 9.1 for CNS involvement as determined by FCM compared with expression less than the median (95% CI, 1.26 to 65.50; P=0.03). Conclusions. The use of more sensitive methods for detecting and quantifying CNS involvement, such as FCM, may facilitate detection of markers of leukemia biology, such as LGMN, which could have therapeutical implications for future CNS-directed therapy.<br>FCM+: Patients had leukemic cells in the cerebrospinal fluid (CSF) detected by flow cytometry and no blood contamination. FCM-: Patients had no leukemic cells in the CSF detected by flow cytometry with or without blood contamination.<br>CNS1: No leukemic cells in CSF detected by cytospin examination with or without blood contamination and no other clinical signs of central nervous system (CNS) leukaemia. CNS2: CSF leukocyte count <5 x106/ÂµL with blasts on cytospin examination and no blood contamination. CNS3: CSF leukocyte count >5 x106/ÂµL with blasts on cytospin examination and no blood contamination, and/or cranial nerve palsy, and/or CNS leukaemia by neuroimaging.

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Gene expression profiles of MLL-AF4 acute lymphoblastic leukaemia blasts retrieved from central nervous system and spleen

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