Engineering ABT-737 Resistance in MYC-driven Lymphomas Identifies DHX9 as a Drug Response Modifier
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
SUBMITTER: Ola Larsson
PROVIDER: E-GEOD-36938 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Many traditional cytotoxic agents used in the treatment of cancer function by eliciting an apoptotic response in tumor cells. However, evasion of apoptosis by BCL-2 family members is often deregulated prior to therapeutic intervention leading to treatment failure. To address this, ABT-737 was rationally designed to target BCL-2-like family members and has shown promising results against tumor cells dependent on BCL-2 for their survival. One shortcoming is that MCL-1, a member of the BCL-2 family is poorly inhibited by ABT-737 and is a major cause of resistance. To gain insight into biological pathways that could circumvent this resistance, we designed an shRNA screen to identify novel sensitizers to ABT-737 by engineering MYC driven lymphomas that were resistant to ABT-737 due to endogenous MCL-1 expression. Utilizing this model, we performed a shRNA drop-out screen and identified Dhx9 as a target whose suppression sensitizes cells to ABT-737. DHX9 loss lead to replicative stress signaling, which in turn potently induced the BH3-only proteins, NOXA and PUMA, in a p53-dependent manner to curtail MCL-1 activity. Induction of NOXA is essential for ABT-737 sensitization. Our results ascribe a novel role for DHX9 in the replicative stress pathway and link DHX9 activity to p53 function in vivo.
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Project description:RNA expression analysis was performed to compare patterns to sensitivity to BCL2 inhibitors (ABT-263). Overexpression of the prosurvival Bcl-2 family members (Bcl-2, Bcl-xL and Mcl-1) is commonly associated with tumor maintenance, progression and chemoresistance. We previously reported the discovery of ABT-737, a potent, small molecule Bcl-2 family protein inhibitor. A major limitation of ABT-737 is that it is not orally bioavailable. This may limit its use for chronic single agent treatment and the flexibility to dose in combination with parenteral chemotherapy. Here we report the discovery and biological properties of ABT-263, a potent, orally bioavailable Bad-like BH3 mimetic (Kiâ??s of < 1 nM for Bcl-2, Bcl-xL and Bcl-w). The oral bioavailability of ABT-263 in preclinical animal models is 20% - 50%, depending on formulation. ABT-263 disrupts Bcl-2/Bcl-xL interactions with pro-death proteins (e.g., Bim) in cells leading to the initiation of apoptosis within 2 hr post-treatment. In human tumor cells, ABT-263 rapidly induces Bax translocation, cytochrome c release and subsequent programmed cell death. Oral administration of ABT-263 alone induces complete tumor regressions in xenograft models of small cell lung cancer and acute lymphoblastic leukemia. In xenograft models of aggressive B-cell lymphoma and multiple myeloma where ABT-263 exhibits modest or no single agent activity, it significantly enhances the efficacy of clinically relevant therapeutic regimens. These data provide the rationale for clinical trials evaluating ABT-263 in SCLC and B-cell malignancies. The oral efficacy of ABT-263 should provide dosing flexibility to maximize clinical utility as both a single agent and in combination with standard chemotherapeutic regimens. Experiment Overall Design: Naive cell lines were isolated in duplicate or triplicate (only a single for H69AR) to determine RNA expression pattern.
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Project description:RNA expression analysis was performed to compare patterns to sensitivity to BCL2 inhibitors (ABT-263). Overexpression of the prosurvival Bcl-2 family members (Bcl-2, Bcl-xL and Mcl-1) is commonly associated with tumor maintenance, progression and chemoresistance. We previously reported the discovery of ABT-737, a potent, small molecule Bcl-2 family protein inhibitor. A major limitation of ABT-737 is that it is not orally bioavailable. This may limit its use for chronic single agent treatment and the flexibility to dose in combination with parenteral chemotherapy. Here we report the discovery and biological properties of ABT-263, a potent, orally bioavailable Bad-like BH3 mimetic (Kiâ??s of < 1 nM for Bcl-2, Bcl-xL and Bcl-w). The oral bioavailability of ABT-263 in preclinical animal models is 20% - 50%, depending on formulation. ABT-263 disrupts Bcl-2/Bcl-xL interactions with pro-death proteins (e.g., Bim) in cells leading to the initiation of apoptosis within 2 hr post-treatment. In human tumor cells, ABT-263 rapidly induces Bax translocation, cytochrome c release and subsequent programmed cell death. Oral administration of ABT-263 alone induces complete tumor regressions in xenograft models of small cell lung cancer and acute lymphoblastic leukemia. In xenograft models of aggressive B-cell lymphoma and multiple myeloma where ABT-263 exhibits modest or no single agent activity, it significantly enhances the efficacy of clinically relevant therapeutic regimens. These data provide the rationale for clinical trials evaluating ABT-263 in SCLC and B-cell malignancies. The oral efficacy of ABT-263 should provide dosing flexibility to maximize clinical utility as both a single agent and in combination with standard chemotherapeutic regimens. Keywords: cell line comparison
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Project description:MicroRNAs (miRNAs) have important roles in gene regulation. Dysregulation of miRNAs has been associated with tumorigenesis. Recent studies suggest miR-193b is a tumor suppressor gene. In a previous study, we reported that miR-193b represses cell proliferation and regulates cyclin D1 (CCND1) in melanoma. Now we demonstrate that miR-193b regulates myeloid cell leukemia sequence 1 (Mcl-1) in melanoma cells. miRNA microarray profiling revealed the miR-193b level in malignant melanomas was significantly downregulated compared to benign nevi, while a tissue microarray demonstrated overexpression of Mcl-1 in malignant melanoma. The Mcl-1 expressions were inversely correlated with the miR-193b levels in melanoma tissue samples, suggesting a potential regulatory role of miR-193b. Overexpression of miR-193b repressed Mcl-1 in melanoma cell lines. It is well known that Mcl-1 knockdown confers cell sensitivity to ABT-737, a small molecular inhibitor of Bcl-2, Bcl-XL and Bcl-w. We found miR-193b, through repressing Mcl-1 expression, could also sensitize melanoma cells that were refractory to ABT-737. Furthermore, miR-193b directly regulates Mcl-1 by targeting the 3’ untranslated region (3’UTR) of Mcl-1 mRNA. Interestingly, miR-193b may recognize sequences on the 3’UTR that do not base pair with its seed region. In conclusion, our study suggests the downregulation of miR-193b could be an early event during melanoma progression, and demonstrates miR-193b directly regulates Mcl-1 by targeting both seed and seedless sequences of the 3’ UTR.
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