Project description:Heterogeneity of leukemia stem cells (LSCs) is involved in their collective chemoresistance. To eradicate LSCs, it is necessary to understand the mechanisms underlying their heterogeneity. Here, we aimed to identify signals responsible for variation in LSCs in human acute myeloid leukemia (AML). While healthy human hematopoietic stem/progenitor cells robustly expressed endothelial cell-selective adhesion molecule (ESAM), AML cells exhibited heterogeneous ESAM expression. Interestingly, ESAM- and ESAM+ AML cells were mutually interconvertible, and RNA sequencing revealed activation of TGFβ signaling in these cells. AML cells secreted TGFβ1, which autonomously activated TGFβ pathway and induced their phenotypic variation. Surprisingly, TGFβ signaling blockade inhibited the variation and proliferation of AML cells. Therefore, autonomous TGFβ signaling underlying LSC heterogeneity may be a promising therapeutic target.
Project description:Heterogeneity of leukemia stem cells (LSCs) is involved in their collective chemoresistance. To eradicate LSCs, it is necessary to understand the mechanisms underlying their heterogeneity. Here, we aimed to identify signals responsible for heterogeneity and variation of LSCs in human acute myeloid leukemia (AML). Monitoring expression levels of endothelial cell-selective adhesion molecule (ESAM), a hematopoietic stem cell-related marker, was useful to detect the plasticity of AML cells. While healthy human hematopoietic stem/progenitor cells robustly expressed ESAM, AML cells exhibited heterogeneous ESAM expression. Interestingly, ESAM- and ESAM+ leukemia cells obtained from AML patients were mutually interconvertible in culture. KG1a and CMK, human AML clones, also represented the heterogeneity in terms of ESAM expression. Single cell culture with ESAM- or ESAM+ AML clones recapitulated the phenotypic interconversion. The phenotypic alteration was regulated at the gene expression level, and RNA sequencing revealed activation of TGFβ signaling in these cells. AML cells secreted TGFβ1, which autonomously activated TGFβ pathway and induced their phenotypic variation. Surprisingly, TGFβ signaling blockade inhibited not only the variation but also the proliferation of AML cells. Therefore, autonomous activation of TGFβ signaling underlies the LSC heterogeneity, which may be a promising therapeutic target for AML.
Project description:Glioblastoma stem cells (GSCs) fate is controlled by environmental cues, among which cytokines play a crucial role. The transforming growth factor β (TGFβ) family signaling pathways controls GSCs. On one hand, TGFβ promotes cell proliferation in GBM, it induces the expression of platelet-derived growth factor-B (PDGFB). Moreover, TGFβ, via its signaling mediators Smad2/3, induces the expression of the cytokine leukemia inhibitory factor (LIF) and Sox4, which in turn enhances the expression of the stem cell transcription factor Sox2; this increases the self-renewal capacity of the GSCs and their stemness characteristics, and enhances the GSC tumor-initiating potential. On the other hand, Bone morphogenic proteins (BMPs) are known to promote GSC differentiation towards the astrocytic phenotype. To further understand which genes are regulated by TGFβ and BMP7 in GSCs we performed a microarray in the Affymetrix HTA2 platform in three different glioblastoma cell line, U2987, and two patient-derived glioblastoma stem cells, U3031MG and U3034MG, in the presence or absence of 5 ng/ml of TGFβ or 30 ng/ml BMP7 for 24 h, three biological replicates per condition.
Project description:Cholangiocarcinoma (CCA) is a devastating liver cancer characterized by high aggressiveness and resistance to therapy, which results to poor prognosis. Signals imposed by oncogenic pathways, such as transforming growth factor β (TGFβ) frequently contribute to CCA development. In this study, we explored novel effectors of the TGFβ pathway in CCA by gene expression profiling. We identified the long non-coding RNA LINC00313 as a novel target gene of TGFβ signalling in CCA cells. TGFβ induced LINC00313 expression in a TβRI/Smad-dependent manner. Subcellular fractionation showed that LINC00313 is a predominantly nuclear lncRNA. By integrating RNA-seq and ATAC-seq data from LINC00313 over-expressing cells, we observed that LINC00313 regulates the expression of several genes involved in the Wnt signalling pathway. As a proof of concept, we focused on the gene encoding transcription factor 7 (TCF7), a major effector that drives transcription of Wnt-target genes. LINC00313 gain of function resulted in increased TCF7 expression, while its loss of function diminished basal or TGFβ-induced TCF7 expression levels. Interestingly, LINC00313 enhanced basal or chemically induced TCF/LEF-dependent transcriptional responses, promoted colony-forming capacities of CCA cells in vitro and accelerated tumor growth in vivo. We also report that genes associated with LINC00313 over-expression recapitulate poor prognosis human CCA associated with a reduced overall survival and KRAS mutations. To decipher the underlying molecular functions of LINC00313, we identified its interacting proteins by performing an unbiased RNA pull-down assay followed by mass spectrometry. We demonstrated that actin-like 6A (ACTL6A), a subunit of the SWI/SNF chromatin remodelling complex specifically binds to LINC00313 and impacts TCF7 expression and TCF/LEF signalling output. Thus, we propose a model whereby TGFβ induces LINC00313, in order to regulate the expression of a subset of target genes, such as TCF7 possibly in co-operation with the SWI/SNF chromatin remodelling complex, via establishing direct interaction with ACTL6A. By regulating key genes of the Wnt pathway, LINC00313 fine-tunes Wnt/TCF/LEF-dependent transcriptional responses and boosts cholangiocarcinogenesis.
Project description:Cholangiocarcinoma (CCA) is a devastating liver cancer characterized by high aggressiveness and resistance to therapy, which results to poor prognosis. Signals imposed by oncogenic pathways, such as transforming growth factor β (TGFβ) frequently contribute to CCA development. In this study, we explored novel effectors of the TGFβ pathway in CCA by gene expression profiling. We identified the long non-coding RNA LINC00313 as a novel target gene of TGFβ signalling in CCA cells. TGFβ induced LINC00313 expression in a TβRI/Smad-dependent manner. Subcellular fractionation showed that LINC00313 is a predominantly nuclear lncRNA. By integrating RNA-seq and ATAC-seq data from LINC00313 over-expressing cells, we observed that LINC00313 regulates the expression of several genes involved in the Wnt signalling pathway. As a proof of concept, we focused on the gene encoding transcription factor 7 (TCF7), a major effector that drives transcription of Wnt-target genes. LINC00313 gain of function resulted in increased TCF7 expression, while its loss of function diminished basal or TGFβ-induced TCF7 expression levels. Interestingly, LINC00313 enhanced basal or chemically induced TCF/LEF-dependent transcriptional responses, promoted colony-forming capacities of CCA cells in vitro and accelerated tumor growth in vivo. We also report that genes associated with LINC00313 over-expression recapitulate poor prognosis human CCA associated with a reduced overall survival and KRAS mutations. To decipher the underlying molecular functions of LINC00313, we identified its interacting proteins by performing an unbiased RNA pull-down assay followed by mass spectrometry. We demonstrated that actin-like 6A (ACTL6A), a subunit of the SWI/SNF chromatin remodelling complex specifically binds to LINC00313 and impacts TCF7 expression and TCF/LEF signalling output. Thus, we propose a model whereby TGFβ induces LINC00313, in order to regulate the expression of a subset of target genes, such as TCF7 possibly in co-operation with the SWI/SNF chromatin remodelling complex, via establishing direct interaction with ACTL6A. By regulating key genes of the Wnt pathway, LINC00313 fine-tunes Wnt/TCF/LEF-dependent transcriptional responses and boosts cholangiocarcinogenesis.
Project description:Cellular senescence is an important in vivo mechanism that prevents the propagation of damaged cells. However, the precise mechanism(s) regulating senescence are not well characterized. Here, we find that ITGB3 (integrin beta 3 or β3) is epigenetically regulated by the Polycomb protein CBX7. β3 expression accelerates the onset of senescence in human primary fibroblasts, by activating the TGFβ pathway in a cell autonomous and non-cell autonomous manner. β3 levels are dynamically increased during oncogeneinduced senescence (OIS) through CBX7 epigenetic regulation. DNA-damage and therapy-induced senescence (TIS) also induce β3 expression. In fact, downregulation of β3 levels override OIS and TIS, independently of its ligand-binding activity. Moreover, cilengitide, a αvβ3 antagonist, has the ability to block the SASP without affecting proliferation. Finally, we show an increase in β3 levels during aging in mice and humans. Altogether, our data show that integrin β3 subunit is a marker and regulator of senescence.