PRC2 loss induces chemoresistance by repressing apoptosis in T cell acute lymphoblastic leukemia.
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ABSTRACT:
SUBMITTER: Aries IM
PROVIDER: S-EPMC6279404 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The tendency of mitochondria to undergo or resist BCL2-controlled apoptosis (so-called mitochondrial priming) is a powerful predictor of response to cytotoxic chemotherapy. To fully exploit this finding, it will be important to understand the molecular genetic contexts responsible for the relative mitochondrial priming of chemotherapy-sensitive versus resistant cell populations. Here, we report that mitochondrial apoptosis resistance in T-cell acute lymphoblastic leukemia (T-ALL) is mediated by inactivation of polycomb repressive complex 2 (PRC2). In T-ALL clinical samples from children with T-ALL treated on recent Dana-Farber Cancer Institute or Children’s Oncology Group clinical trials, we found that loss-of-function mutations in any of three core components of PRC2 (EZH2, EED or SUZ12) were associated with resistance to mitochondrial apoptosis. In human T-ALL cells, PRC2 depletion induced resistance to apoptosis induction by multiple chemotherapeutics with distinct mechanisms of action, including dexamethasone, doxorubicin and vincristine. PRC2 loss induced apoptosis resistance via transcriptional upregulation of the LIM domain transcription factor CRIP2, and subsequent downstream upregulation of the mitochondrial chaperone TRAP1. Importantly, TRAP1 overexpression was necessary to induce resistance to chemotherapy-induced apoptosis downstream of PRC2 inactivation, and pharmacologic inhibition of TRAP1 synergized with dexamethasone and doxorubicin. These findings demonstrate the importance of relative mitochondrial apoptotic priming as a prognostic factor in T-ALL, and implicate mitochondrial chaperone function as a molecular determinant of response to cancer chemotherapy, suggesting a rationale for targeted therapeutic intervention.
2018-10-18 | GSE112147 | GEO
Project description:Cell adhesion plays a critical role in the development of chemoresistance, which is a major issue in anti-cancer therapies. In this study, we have examined the role of the VLA-4 integrin, a major adhesion molecule of the immune system, in the chemoresistance of T-ALL cells. We found that attachment of Jurkat and HSB-2 T-ALL cells to VCAM-1, a VLA-4 ligand, inhibits doxorubicin-induced apoptosis. However, their adhesion to fibronectin, which is mainly mediated via VLA-5, had no effect. Even the presence of the chemoattractant SDF1α (Stromal cell-derived factor-1α), which enhances the adhesion of T-ALL cells to fibronectin, did not modify the sensitivity of the cells attached on fibronectin towards doxorubicin-induced apoptosis. Mechanistically, we found that VLA-4 promoted T-ALL chemoresistance by inducing doxorubicin efflux. Our results showed that cell adhesion to both fibronectin and VCAM-1-induced Focal adhesion kinase (FAK) phosphorylation in T-ALL cells. However, only cell adhesion to VCAM-1 led to PYK2 phosphorylation. Inhibition studies indicated that FAK is not involved in doxorubicin efflux and chemoresistance, whereas PYK2 inhibition abrogated both VLA-4-induced doxorubicin efflux and chemoresistance. Together, these results indicate that the VLA-4/PYK2 pathway could participate in T-ALL chemoresistance and its targeting could be beneficial to limit/avoid chemoresistance and patient relapse.
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Project description:Over the past decade, histone deacetylase inhibitors have increasingly been used to treat various malignancies. Tubacin (tubulin acetylation inducer) is a small molecule that inhibits histone deacetylase 6 (HDAC6) and induces acetylation of ?-tubulin. We observed a higher antiproliferative effect of tubacin in acute lymphoblastic leukemia (ALL) cells than in normal hematopoietic cells. Treatment with tubacin led to the induction of apoptotic pathways in both pre-B and T cell ALL cells at a 50% inhibitory concentration (IC(50)) of low micromolar concentrations. Acetylation of ?-tubulin increases within the first 30?min following treatment of ALL cells with tubacin. We also observed an accumulation of polyubiquitinated proteins and poly(ADP-ribose) polymerase (PARP) cleavage. Furthermore, the signaling pathways activated by tubacin appear to be distinct from those observed in multiple myeloma. In this article, we demonstrate that tubacin enhances the effects of chemotherapy to treat primary ALL cells in vitro and in vivo. These results suggest that targeting HDAC6 alone or in combination with chemotherapy could provide a novel approach to treat ALL.
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Project description:Deubiquitylating enzyme ubiquitin-specific protease 1 (USP1) has been reported to be aberrantly overexpressed in cancers, and it plays a critical role in regulating various cellular processes, such as cell proliferation, apoptosis, and cell differentiation. However, the role of USP1 in B-cell acute lymphoblastic leukemia (B-ALL) remains largely undefined. USP1 expression in 30 newly diagnosed B-ALL patients was detected by real-time PCR and western blot. We found that USP1 was generally upregulated in the bone marrow cells derived from B-ALL patients. Knockdown of USP1 by siRNA decreased B-ALL cell growth and induced apoptosis. Similarly, pharmacological inhibition of USP1 by SJB3-019A significantly repressed cell proliferation and triggered B-ALL cell apoptosis. Finally, we found that inhibition of USP1 downregulated the expression of ID1 and p-AKT, and upregulated ID1 expression could reverse the suppressive effects of USP1 inhibitor in B-ALL cells. Taken together, these results demonstrate that USP1 promote B-ALL progression at least partially via the ID1/AKT signaling pathway, and USP1 inhibitors might be promising therapeutic application for B-ALL.
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Project description:Acute lymphoblastic leukemia (ALL) is the most prevalent of pediatric cancers. Neuroepithelial cell-transforming 1 (NET1) has been associated with malignancy in a number of cancers, but the role of NET1 in ALL development is unclear. In the present study, we investigated the effect of NET1 gene in ALL cell proliferation and chemoresistance. We analyzed GEO microarray data comparing bone marrow expression profiles of pediatric B-cell ALL samples and those of age-matched controls. MTT and colony formation assays were performed to analyze cell proliferation. ELISA assays, Western blot analyses, and TUNEL staining were used to detect chemoresistance. We confirmed that NET1 was targeted by miR-206 using Western blot and luciferase reporter assays. We identified NET1 gene as one of the most significantly elevated genes in pediatric B-ALL. MTT and colony formation assays demonstrated that NET1 overexpression increases B-ALL cell proliferation in Nalm-6 cells. ELISA assays, Western blot analyses, and TUNEL staining showed that NET1 contributes to ALL cell doxorubicin resistance, whereas NET1 inhibition reduces resistance. Using the TargetScan database, we found that several microRNAs (miRNAs) were predicted to target NET1, including microRNA-206 (miR-206), which has been shown to regulate cancer development. To determine whether miR-206 targets NET1 in vitro, we transfected Nalm-6 cells with miR-206 or its inhibitor miR-206-in. Western blot assays showed that miR-206 inhibits NET1 expression and miR-206-in increases NET1 expression. Luciferase assays using wild-type or mutant 3'-untranslated region (3'-UTR) of NET1 confirmed these findings. We ultimately found that miR-206 inhibits B-ALL cell proliferation and chemoresistance induced by NET1. Taken together, our results provide the first evidence that NET1 enhances proliferation and chemoresistance in B-ALL cells and that miR-206 regulates these effects by targeting NET1. This study therefore not only contributes to a greater understanding of the molecular mechanisms underlying B-ALL progression but also opens the possibility for developing curative interventions.
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