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: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:Precursor B-lineage acute lymphoblastic leukemia (pre-B ALL) can be subdivided into different categories based on genetic abnormalities. One type of pre-B ALL is characterized by the presence of the Philadelphia (Ph) chromosome, the derivative chromosome 22 that is one product of a reciprocal translocation between chromosomes 22 and 9. The 22/9 translocation fuses the 5’ part of the BCR gene to the 3’ end of the c-ABL gene. The resulting BCR/ABL fusion encodes a Bcr/Abl protein with deregulated Abl kinase activity. Two major fusion proteins are found in Ph-positive leukemias which differ in molecular weight and the size of the Bcr moiety. The P190 Bcr/Abl protein is common in Ph-positive ALL. Targeted tyrosine kinase inhibitors such as nilotinib are used therapeutically to treat this type of leukemia. The 22/9 translocation fuses the 5’ part of the BCR gene to the 3’ end of the c-ABL gene. The resulting BCR/ABL fusion encodes a Bcr/Abl protein with deregulated Abl kinase activity. Two major fusion proteins are found in Ph-positive leukemias which differ in molecular weight and the size of the Bcr moiety. The P190 Bcr/Abl protein is common in Ph-positive ALL. Targeted tyrosine kinase inhibitors such as nilotinib are used therapeutically to treat this type of leukemia.
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: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:The BCR-ABL oncogene, generated by Philadelphia chromosome, is present in about 95% human Chronic myeloid leukemia (CML) and 20~30% acute lymphoblastic leukemia (ALL). One of BCR-ABL isoforms, P210, is more often detected in CML and ALL patients. Although BCR-ABL kinase inhibitors are effective in controlling the diseases, they do not provide cure due to the development of drug resistance and the insensitivity of leukemia stem cells to these drugs. Identification of new therapeutic targets is critical. To identify potential target against leukemia stem cells, we studied gene expression in leukemia stem cells, which were identified in mice in our lab (Hu Y, Swerdlow S, Duffy TM, Weinmann R, Lee FY, Li S. 2006. Targeting multiple kinase pathways in leukemic progenitors and stem cells is essential for improved treatment of Ph+ leukemia. Proc Natl Acad Sci USA 103(45):16870-16875.). The sorted leukemia stem cells that expressed BCR-ABL were used for isolation of RNA, followed by the analysis of gene expression using the DNA microarray. The same lineage of non-BCR-ABL-expressing normal hematopoietic stem cells was used as control. We have identified some interesting genes that are up- or down-regulated by BCR-ABL in these leukemia stem cells. We are currently studying the functions of these identified genes. Keywords: Genetic modification
Project description:Chronic myelogenous leukemia (CML) is a malignant disease of the hematopoietic stem cell, characterized by the expression of the Bcr-Abl oncogene by leukemic cells. In order to analyze the molecular pathways modulated by Bcr-Abl, we have previously generated an inducible model of Bcr-Abl expression in the murine Ba/F3 cell line based on the Tet-OFF system. In the present study, through a microarray approach applied to cells grown with (Bcr-Abl-expression OFF) or without (Bcr-Abl-expression ON) doxycycline, a tetracycline analogue, we analyzed the gene expression variations upon Bcr-Abl expression.
Project description:Chronic myelogenous leukemia (CML) is a malignant disease of the hematopoietic stem cell, characterized by the expression of the Bcr-Abl oncogene by leukemic cells. In order to analyze the molecular pathways modulated by Bcr-Abl, we have previously generated an inducible model of Bcr-Abl expression in the murine Ba/F3 cell line based on the Tet-OFF system. In the present study, through a microarray approach applied to cells grown with (Bcr-Abl-expression OFF) or without (Bcr-Abl-expression ON) doxycycline, a tetracycline analogue, we analyzed the gene expression variations upon Bcr-Abl expression. Keywords: repeat sample
Project description:BCR-ABL positive acute lymphoblastic leukemia (ALL) cell survival is strongly dependent on the IRE1α-XBP1 branch of the Unfolded Protein Response (UPR). In the study at hand, we have focused on exploring the link between BCR-ABL1 and IRE1α to better understand whether a simultaneous pharmacological inhibition of both pathways could represent a beneficial therapeutic strategy in Philadelphia positive (Ph+) ALL. Therefore, the effect on the phosphoproteome of two inhibitors (MKC-8866 and Nilotinib) as well as a combination of both compounds was analysed in this study.
Project description:The biology of chronic myeloid leukemia (CML)-stem cells is still incompletely understood. Therefore, we previously developed an inducible transgenic mouse model in which stem cell targeted induction of BCR-ABL expression leads to chronic phase CML-like disease. Here, we now demonstrate that the disease is transplantable using BCR-ABL positive LSK cells (lin-Sca-1+c-kit+). Interestingly, the phenotype is enhanced when unfractionated bone marrow (BM) cells are transplanted. However, neither progenitor cells (lin-Sca-1-c-kit+) nor mature granulocytes (CD11b+Gr-1+), or potential stem cell niche cells were able to transmit the disease or alter the phenotype. The phenotype was largely independent of BCR ABL priming prior to transplant. However, BCR-ABL abrogated the potential of LSK cells to induce full blown disease in secondary recipients. Subsequently, we found that BCR-ABL increased the fraction of multipotent progenitor cells (MPP) at the expense of long term HSC (LT-HSC) in the BM. Microarray analyses of LSK cells revealed that BCR-ABL alters the expression of genes involved in proliferation, survival, and hematopoietic development. Our results suggest that BCR-ABL induces differentiation of LT-HSC and decreases their self renewal capacity. Furthermore, reversion of BCR-ABL eradicates mature cells while leukemic stem cells persist, giving rise to relapsed CML upon re-induction of BCR-ABL.