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Therapy resistant primitive stem cells in chronic myelogenous leukemia are characterized by low c-Kit expression and altered SCF response

ABSTRACT: Leukemia stem cells (LSC) in chronic myelogenous leukemia (CML) resist elimination with tyrosine kinase inhibitors (TKI) and persist as a source of disease recurrence. LSC populations are heterogeneous, but the most primitive, drug-resistant subsets are not well characterized. Previous studies indicate that variable cell-surface expression of the c-Kit receptor identifies heterogeneous hematopoietic stem cells (HSC) populations. We found that c-Kit expression is reduced on CML LSC compared to normal HSC. Long-term engraftment and leukemia generation capacity was restricted to low c-Kit expressing (c-KitLow) LSC, which showed increased quiescence and inflammatory gene signatures expression. The c-Kit ligand, stem cell factor (SCF), expanded normal HSC but drove maturation of CML LSC. The proportion of c-Kitlow LT-HSC was increased with TKI treatment. Supplementary SCF treatment enhanced elimination of committed but not primitive CML LT-HSC in TKI-treated mice. Low c-Kit expression identifies primitive, treatment-resistant LSC subpopulations with distinct regulatory characteristics, that are critical therapeutic targets.

ORGANISM(S): Mus musculus

PROVIDER: GSE180496 | GEO | 2022/11/29

REPOSITORIES: GEO

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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).

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Therapy resistant primitive stem cells in chronic myelogenous leukemia are characterized by low c-Kit expression and altered SCF response

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