Project description:Interferon is effective at inducing complete remissions in patients with Chronic Myelogenous Leukemia (CML), and evidence supports an immune mechanism. Here we show that the Type I Interferons (alpha and beta) regulate expression of the Interferon consensus sequence binding protein (ICSBP) in bcr-abl transformed cells and as shown previously for ICSBP, induce a vaccine-like immunoprotective effect in a murine model of bcr-abl induced leukemia. We identify the chemokines CCL6 and CCL9 as genes prominently induced by the Type I Interferons and ICSBP, and demonstrate that these immunomodulators are required for the immunoprotective effect of ICSBP expression. Insights into the role of these chemokines in the anti-leukemic response of interferons suggest new strategies for immunotherapy of CML.
Project description:Interferon is effective at inducing complete remissions in patients with Chronic Myelogenous Leukemia (CML), and evidence supports an immune mechanism. Here we show that the Type I Interferons (alpha and beta) regulate expression of the Interferon consensus sequence binding protein (ICSBP) in bcr-abl transformed cells and as shown previously for ICSBP, induce a vaccine-like immunoprotective effect in a murine model of bcr-abl induced leukemia. We identify the chemokines CCL6 and CCL9 as genes prominently induced by the Type I Interferons and ICSBP, and demonstrate that these immunomodulators are required for the immunoprotective effect of ICSBP expression. Insights into the role of these chemokines in the anti-leukemic response of interferons suggest new strategies for immunotherapy of CML. Experiment Overall Design: Total RNA was isolated from parental BaF3 cells as well as BaF3 cells expressing BCR-ABL, ICSBP, or both BCR-ABL and ICSBP. Using standard Affymetrix protocols the RNA samples were analyzed for gene expression using Affymetrix mouse 430_2 whole genome microarrays arrays. A threshold value of 50 was set for all genes and the list of genes filtered to include only those that had at least one Present flag ("P" flag) in one of the 4 conditions. For each gene, the ratio of its expression in a particular condition and its expression in parental BaF3 cells was determined. Only genes that had at least a 3-fold up or down change in expression were considered, leaving a set of 1431 genes for further analysis. K-means clustering with Gene cluster 3.0 was used to group these 1431 genes into 15 clusters and JavaTree was used to visualize the results.
Project description:Tyrosine kinase activity is the crucial enzymatic activity driving all known functions of the BCR-ABL protein and is required for protection from apoptosis by BCR-ABL, therefore, targeting this enzyme is an effective approach for therapeutic strategies. Recently, a novel structural entity, imatinib (STI571; Novartis, Basel, Switzerland), a potent and selective inhibitor of the tyrosine kinase activity of BCR-ABL, has shown promise against Ph-positive leukemia in human clinical trials. However, the emergence of imatinib resistance in patients with acute forms of Ph-positive leukemia has highlighted the need for overriding chemotherapy to eradicate this disease. AMN107 and BMS-354825 are clinically active “next-generation” BCR-ABL inhibitors. One potentially powerful approach is to use these compounds in combination with imatinib. The rationale for such approaches is that an inhibitor cocktail may target the widest range of resistant clones and thereby delay the onset of acquired drug resistance. More potent BCR-ABL inhibitors would be to target residual leukemia that persists in patients in whom imatinib induces durable remission but failed to eradicate the disease. From these points, our studies are performed to determine (1) the differences of molecular signaling pathways between BMS-354825 and imatinib (2) the mechanisms by which drug resistance of BMS-354825 and imatinib occur except for point mutation of BCR-ABL kinase domain. Keywords: drug sensitivity
Project description:Aberrant long noncoding RNA (lncRNA) expression has been described in many human malignancies, including leukemia. Philadelphia-positive (Ph+) chronic myeloid leukemia (CML) is a stem cell disease induced by Bcr-Abl hybrid gene. Here we attempt to identify lncRNAs associated with CML by analyzing lncRNA expression profiles in K562 cells when Bcr-Abl gene silenced. LncRNA microarray analysis revealed a group of lncRNAs that exhibit Bcr-Abl-dependent expression. In this study, we focused on lncRNA-X that was downregulated by Bcr-Abl, suggesting that lncRNA-X might have a function of tumor suppression. We showed that lncRNA-X over-expression delays Bcr-Abl-induced tumorigenesis in vivo, maybe through its effect on cell survival by modulating STAT5-dependent expression of anti-apoptotic Bcl-XL protein. We also demonstrated that lncRNA-X may affect tumor formation behavior of Bcr-Abl-transformed cells by regulating signaling pathways associated with leukemia stem cells of CML. Together, these results suggest that lncRNA-X suppresses Bcr-Abl-induced tumorigenesis, and the tumor suppressor function of lncRNA-X may be of significance for exploring novel therapeutic strategies for treating CML. This microarray was performed to identify lncRNAs associated with Bcr-Abl-induced chronic myeloid leukemia (CML).
Project description:Although Bcr-Abl kinase inhibitors have proven effective in the treatment of chronic myeloid leukemia (CML), they generally fail to completely eradicate Bcr-Abl+ leukemia cells. To identify genes whose inhibition sensitizes Bcr-Abl+ leukemias to killing by Bcr-Abl inhibitors, we performed an RNAi-based synthetic lethal screen with imatinib in CML cells. This screen identified numerous components of a Wnt/Ca2+/NFAT signaling pathway. Antagonism of this pathway led to impaired NFAT activity, decreased cytokine production and enhanced sensitivity to Bcr-Abl inhibition. Furthermore, NFAT inhibition with cyclosporin A facilitated leukemia cell elimination by the Bcr-Abl inhibitor dasatinib and markedly improved survival in a mouse model of Bcr-Abl+ acute lymphoblastic leukemia (ALL). Targeting this pathway in combination with Bcr-Abl inhibition could improve treatment of Bcr-Abl+ leukemias.
Project description:BCR-Abl is a driver oncogene that causes chronic myeloid leukemia and a subset of acute lymphoid leukemias. Although tyrosine kinase inhibitors provide an effective treatment for these diseases, they generally do not kill leukemic stem cells. Leukemic stem cells are cancer-initiating cells that compete with normal hematopoietic stem cells for the bone marrow niche. Using BCR-Abl as a model oncogene, we performed a drug screen based on competition between isogenic untransformed cells and BCR-Abl-transformed cells, and identified several compounds that selectively target BCR-Abl-transformed cells. Systems-level analysis of one of these novel compounds, DJ34, revealed that it induced depletion of c-Myc and activation of p53. c-Myc depletion occurred in a wide range of tumor types, including leukemia, lymphoma, lung, glioblastoma and breast cancer. Further analyses revealed that DJ34 interferes with c-Myc synthesis at the level of transcription, and we provide data showing that DJ34 is a DNA intercalator and topoisomerase II inhibitor. Physiologically, DJ34 induced apoptosis, cell cycle arrest and cell differentiation, and primary leukemic stem cells were particularly sensitive to DJ34. Taken together, we have identified a novel compound that dually targets c-Myc and p53 in a wide variety of cancers, and with particularly strong activity against leukemic stem cells.
Project description:To investigate the mechanism of telomerase regulation in BCR-ABL positive cells due to its clinical value, we studied the catalytic component of telomerase, TERT. Our results suggest that BCR-ABL plays an important role in regulating hTERT in K562 (BCR-ABL positive human leukemia) cells. When Gleevec inhibited the tyrosine kinase activity of BCR-ABL, phosphorylation of hTERT was downregulated, therefore suggesting a positive correlation between BCR-ABL and hTERT. Gleevec treatment inhibited hTERT at the mRNA level and significantly reduced telomerase activity (TA) in K562 cells, but not in HL60 or Jurkat cells. TRAP assay also revealed that Gleevec treatment significantly reduced TA specifically in K562 cells. Furthermore, translocation of hTERT from nucleoli to nucleoplasm was observed in K562 cells induced by Gleevec. Although Gleevec down-regulated hTERT mRNA level, the protein level of hTERT remained unchanged. Therefore, Gleevec-induced-TA decrease is not due to the alteration in telomerase subunits expression. It could be presumably due to posttranslational modification of hTERT, possibly through multiple signaling pathways. We have found that Gleevec reduced the tyrosine phosphorylation of hTERT by BCR-ABL, which is associated with the nucleoplasm localization of hTERT from nucleoli sequesters. These findings reveal unknown functions and regulations of telomerase by BCR-ABL. Using cRNA microarray, gene expression of Gleevec-treated and non-treated K562 (BCR-ABL positive) cells were compared against Gleevec-treated and non-treated HL60 (BCR-ABL deficient) cells.
Project description:One of the main objective of this study is to characterize Imatinib induced MSCs-mediated resistance evolution in BCR-ABL+ ALL. Tyrosine kinase inhibitor (TKI) Imatinib (IM) is used as a frontline therapy for BCR-ABL–positive (BCR-ABL+) acute lymphoblastic leukemia (ALL). However, resistance to IM therapy develops rapidly in a substantial proportion of treated patients, and the molecular mechanisms underlying the resistance are poorly understood. In this study, we identified a novel cascade of consequential events that are initiated by IM, which traverse through mesenchymal stem/stromal cells (MSCs) to leukemic cells, and lead to IM resistance. Our data showed that MSCs exposed to IM were decreased in their stemness and acquired a new functional status that enabled the formation of leukemic cell niches. These MSCs had increased expression of genes encoding chemo-attractants, adhesion molecules, and pro-survival stimulant growth factors. We found that BCR-ABL+ leukemic cells persistently exposed to IM were able to switch from BCR-ABL–driven signaling to growth factor–driven signaling for survival, and this switch was reversible. Blocking both the BCR-ABL–driven pathway and the growth factor–driven JAK pathway effectively eradicated the leukemic cell niches. Our findings illustrate TKI-induced, MSC-mediated drug resistance, suggesting an effective way to eliminate this type of drug resistance in patients with BCR-ABL+ ALL. Gene expression signatures were compared from triplicate samples of MSCs that were either treated with vehicle or imatinib for 32, 64 and 96 hours.
Project description:Although Bcr-Abl kinase inhibitors have proven effective in the treatment of chronic myeloid leukemia (CML), they generally fail to completely eradicate Bcr-Abl+ leukemia cells. To identify genes whose inhibition sensitizes Bcr-Abl+ leukemias to killing by Bcr-Abl inhibitors, we performed an RNAi-based synthetic lethal screen with imatinib in CML cells. This screen identified numerous components of a Wnt/Ca2+/NFAT signaling pathway. Antagonism of this pathway led to impaired NFAT activity, decreased cytokine production and enhanced sensitivity to Bcr-Abl inhibition. Furthermore, NFAT inhibition with cyclosporin A facilitated leukemia cell elimination by the Bcr-Abl inhibitor dasatinib and markedly improved survival in a mouse model of Bcr-Abl+ acute lymphoblastic leukemia (ALL). Targeting this pathway in combination with Bcr-Abl inhibition could improve treatment of Bcr-Abl+ leukemias. We utilized a genome-wide shRNA library in combination with microarray analysis to screen for gene targets in chronic myeloid leukemia cells that cooperate with imatinib.
Project description:Anti-leukemia immunity plays an important role for disease control and maintenance of tyrosine kinase inhibitor (TKI)-free remission in chronic myeloid leukemia (CML). Antigen-specific immunotherapy holds promise to strengthen immune control in CML, but requires the identification of CML-associated targets. In this study, we used a mass spectrometry-based approach to identify naturally presented HLA class I- and class II-presented peptides in 20 primary CML samples. Comparative HLA ligandome profiling using a comprehensive dataset of different hematological benign specimen delineated a novel panel of frequently expressed CML-exclusive peptides. These non-mutated target antigens are of particular relevance since our extensive data-mining approach demonstrated absence of naturally presented BCR-ABL- and ABL-BCR-derived HLA-presented peptides and the lack of frequent tumor-exclusive presentation of predescribed cancer/testis and leukemia-associated antigens. Functional characterization revealed spontaneous T-cell responses against the newly identified CML-associated peptides in CML patients and their ability to de novo induce multifunctional and cytotoxic antigen-specific T cells in healthy volunteers and CML patients. This characterizes these antigens as prime candidates for T cell-based immunotherapy approaches that may prolong TKI-free survival and even mediate cure of CML patients.