Project description:Properties of cancer stem cells (CSC) involved in drug-resistance and relapse have significant effect on clinical outcome. Although tyrosine kinase inhibitors (TKIs) have dramatically improved survival of patients with chronic myelogenous leukemia (CML), TKIs have not fully cure CML due to TKI-resistant CML stem cells. Moreover, the relapse after discontinuation of TKIs has not been predicted in CML patients with best TKI-response. In our study, pre-hematoopoietic progenitor cells (pre-HPCs), a model of CML stem cells derived from CML-iPSCs identified a novel antigen of TKI-resistant CML cells. Even in the fraction reported as TKI-sensitive, the antigen+ cells showed TKI-resistance in CML patients. In addition, residual CML cells in patients with optimal TKI-response were concentrated in the antigen+ population.
Project description:Acquired imatinib resistance in chronic myelogenous leukemia (CML) can be the consequence of mutations in the kinase domain of BCR-ABL or increased protein levels. However, as in other malignancies, acquired resistance to cytostatic drugs is a common reason for treatment failure or disease progression. As a model for drug resistance, we developed a CML cell line resistant to cyclophosphamide (CP). Using oligonucleotide arrays, we examined changes in global gene expression. Selected genes were also examined by real-time PCR and flow cytometry. Neither the parent nor the resistant lines had mutations in their ATP binding domain. Filtering genes with a low-base line expression, a total of 239 genes showed significant changes (162 up- and 77 down-regulated) in the resistant clone. Most of the up-regulated genes were associated with metabolism, signal transduction, or encoded enzymes. The gene for aldehyde dehydrogenase 1 was over-expressed more than 2000 fold in the resistant clone. BCR-ABL was expressed in both cell lines to a comparable extent. When exposed to the tyrosine kinase inhibitors imatinib and nilotinib, both lines were sensitive. In conclusion, we found multiple genetic changes in a CML cell line resistant to CP related to metabolism, signal transduction or apoptosis. Despite these changes, the resistant cells retained sensitivity to tyrosine kinase inhibitors. Keywords: Cell type comparison
Project description:Acquired imatinib resistance in chronic myelogenous leukemia (CML) can be the consequence of mutations in the kinase domain of BCR-ABL or increased protein levels. However, as in other malignancies, acquired resistance to cytostatic drugs is a common reason for treatment failure or disease progression. As a model for drug resistance, we developed a CML cell line resistant to cyclophosphamide (CP). Using oligonucleotide arrays, we examined changes in global gene expression. Selected genes were also examined by real-time PCR and flow cytometry. Neither the parent nor the resistant lines had mutations in their ATP binding domain. Filtering genes with a low-base line expression, a total of 239 genes showed significant changes (162 up- and 77 down-regulated) in the resistant clone. Most of the up-regulated genes were associated with metabolism, signal transduction, or encoded enzymes. The gene for aldehyde dehydrogenase 1 was over-expressed more than 2000 fold in the resistant clone. BCR-ABL was expressed in both cell lines to a comparable extent. When exposed to the tyrosine kinase inhibitors imatinib and nilotinib, both lines were sensitive. In conclusion, we found multiple genetic changes in a CML cell line resistant to CP related to metabolism, signal transduction or apoptosis. Despite these changes, the resistant cells retained sensitivity to tyrosine kinase inhibitors. Experiment Overall Design: A CML cell line and a CP resistant subline were compared by gene array. In addition other markers, the expression of BCR-ABL and the sensitivity to tyrosine kinase inhibitors were tested.
Project description:In this report, we revealed that branched chain amino acid transaminase 1 (BCAT1) is highly enriched in both mouse and human TKI-resistant CML cells. Leukemia was almost completely abrogated upon BCAT1 knockdown during transplantation in a BCR-ABLT315I-induced murine TKI-resistant CML model . Moreover, knockdown of BCAT1 led to a dramatic decrease in the proliferation of TKI-resistant human leukemia cell lines. BCAA/BCAT1 signaling enhanced the phosphorylation of CREB, which is required for maintenance of TKI-resistant CML cells. Importantly, blockade of BCAA/BCAT1 signaling efficiently inhibited leukemogenesis both in vivo and in vitro.
Project description:To elucidate whether tyrosine kinase inhibitor (TKI) resistance in CML is associated with characteristic genomic alterations, we analyzed DNA samples from 45 TKI resistant CML patients with 250K single nucleotide polymorphism (SNP) arrays. From 20 patients, matched serial samples of pre-treatment and TKI resistance time points were available. 11 of the 45 TKI resistant patients had mutations of BCR-ABL1, including two T315I mutations. Besides known TKI resistance associated genomic lesions such as duplication of the BCR-ABL1 gene (n=8) and trisomy 8 (n=3), recurrent submicroscopic alterations including acquired uniparental disomy were detectable on chromosomes 1, 8, 9, 17, 19 and 22. On chromosome 22, newly acquired and recurrent deletions of the IGLC1 locus were detected in three patients, who had previously presented with lymphoid or myeloid blast crisis. This may support a hypothesis of TKI induced selection of subclones differentiating into immature B-cell progenitors as a mechanism of disease progression and evasion of TKI sensitivity. Keywords: SNP-chip
Project description:Global analysis of the effects of attenuated and VP3 mutant isolates of chicken anaemia virus on host gene expression using oligonucleotide arrays.
Project description:In vivo global analysis of the effects of attenuated and VP3 mutant isolates of chicken anaemia virus on host gene expression using oligonucleotide arrays.
Project description:Tyrosine kinase inhibitors (TKIs) have revolutionized chronic myelogenous leukemia (CML) management. Disease eradication, however, is hampered by innate resistance of leukemia initiating cells (LICs) to TKI-induced killing, which also provides the basis for subsequent emergence of TKI-resistant mutants. We report that EZH2, the catalytic subunit of Polycomb Repressive Complex 2 (PRC2), is overexpressed in CML LICs, required for colony formation, and survival and cell cycle progression of CML cell lines. A critical role for Ezh2 is supported by genetic studies in a mouse CML model. Inactivation of Ezh2 in conventional conditional mice and through CRISPR/Cas9-mediated gene editing prevents initiation and maintenance of disease and survival of LICs, irrespective of BCR/ABL1 mutational status, and extends survival. Expression of the Ezh2 homolog Ezh1 is reduced in Ezh2-deficient CML LICs, creating a scenario resembling complete loss of PRC2. EZH2-dependence of CML LICs raises prospects for improved therapy of TKI-resistant CML and/or eradication of disease by addition of EZH2 inhibitors.
Project description:Tyrosine kinase inhibitors (TKI) are highly effective in treatment of chronic myeloid leukemia (CML) but do not eliminate leukemia stem cells (LSC), which remain a potential source of relapse. TKI treatment effectively inhibits BCR-ABL kinase activity in CML LSC, suggesting that additional kinase-independent mechanisms contribute to LSC preservation. We investigated whether signals from the bone marrow (BM) microenvironment protect CML LSC from TKI treatment. Coculture with human BM mesenchymal stromal cells (MSC) significantly inhibited apoptosis and preserved CML stem/progenitor cells following TKI exposure, maintaining colony forming ability and engraftment potential in immunodeficient mice. We found that the N-Cadherin receptor plays an important role in MSC-mediated protection of CML progenitors from TKI. N-Cadherin-mediated adhesion to MSC was associated with increased cytoplasmic N-Cadherin-M-NM-2-catenin complex formation, as well as enhanced M-NM-2-catenin nuclear translocation and transcriptional activity. Increased exogenous Wnt-mediated M-NM-2-catenin signaling played an important role in MSC-mediated protection of CML progenitors from TKI treatment. Our results reveal a close interplay between N-Cadherin and the Wnt-M-NM-2-catenin pathway in protecting CML LSC during TKI treatment. Importantly, these results reveal novel mechanisms of resistance of CML LSC to TKI treatment, and suggest new targets for treatment designed to eradicate residual LSC in CML patients. RNA was obtained from CML CD34+ cells treated with or without IM (5M-NM-<M) and MSC for 96 hours, amplified, labeled and hybridized to GeneChip 1.0 arrays (Affymetrix, Santa Clara, CA). Microarray data analysis was performed using R (version 2.9) with genomic analysis packages from Bioconductor (version 2.4). The 33297 probes represented on the microarray were filtered by cross-sample mean, and for standard deviation of greater than the 25% quantile, yielding 18624 probes representing 12553 genes. Linear regression was used to model the gene expression with the consideration of a 2x2 factorial design and matched samples. Differentially expressed genes were identified by calculating empirical Bayes moderated t-statistic, and p-values were adjusted by FDR using the M-bM-^@M-^\LIMMAM-bM-^@M-^] package. Gene Set Enrichment Analysis (GSEA) was performed using GSEA software version 2.04 to detect enrichment of predetermined gene sets using t-scores from all genes for 1263 gene sets in the C2 (curated gene sets) category from the Molecular Signature Database (MsigDB).