Project description:Hhex encodes a homeobox transcriptional regulator that plays a key role in embryonic development and hematopoiesis. Hhex is highly expressed in NK cells and germline deletion of Hhex results in significant defects in lymphoid development, including NK cells. However, whether Hhex is intrinsically required throughout NK cell development or for NK cell function remains unknown. To investigate this, we generated mice that specifically lack Hhex in NK cells. Hhex was intrinsically required for NK cell homeostasis, while NK cell differentiation, IL-15 responsiveness and cytotoxic function were largely normal in the absence of Hhex. Unexpectedly, increased IL-15 availability failed to rescue Hhex-deficient NK cell homeostasis, suggesting that Hhex regulates developmental pathways extrinsic to those dependent on IL-15. Gene expression and functional genetic approaches revealed that Hhex promoted NK cell survival by repressing BIM expression, a key apoptotic mediator in NK cells. This study identifies Hhex as a novel transcription factor essential for NK cell biology.
Project description:Hhex encodes a homeobox transcriptional regulator important for embryonic development and hematopoiesis. Hhex is highly expressed in NK cells and its germline deletion results in significant defects in lymphoid development, including NK cells. To determine if Hhex is intrinsically required throughout NK cell development or for NK cell function, we generated mice that specifically lack Hhex in NK cells. NK cell numbers was dramatically reduced, while NK cell differentiation, IL-15 response and function at the cellular level remained largely normal in the absence of Hhex. Increased IL-15 availability failed to fully reverse NK lymphopenia following conditional Hhex deletion, suggesting that Hhex regulates developmental pathways extrinsic to those dependent on IL-15. Gene expression and functional genetic approaches revealed that Hhex regulates NK cell survival by repressing expression of the key apoptotic mediator, BIM. These data implicates Hhex as a novel transcription factor essential for NK cell homeostasis and immunity.
Project description:C-MYC (henceforth MYC) is one of the most frequently overexpressed oncogenes in human cancer and even modestly deregulated MYC expression can initiate ectopic proliferation in many post-mitotic, terminally differentiated cell types in vivo. Metazoan organisms have consequently evolved a number of mechanisms to counteract MYC's oncogenic potential, of which apoptosis is arguably the best understood. However, the mechanisms through which MYC induces apoptosis remains controversial, with some studies implicating p19ARF-mediated stabilization of p53, followed by induction of pro-apoptotic BH3 family member NOXA and PUMA, while others argue for more direct regulation of BH3 proteins, especially BIM. The debate likely stems from the use of different experimental systems, modes of perturbation, and quite possibly different levels of MYC expression. Here, we use a single experimental system to systematically evaluate the roles of p19ARF and BIM during MYC-induced apoptosis, in vitro, in vivo, and in combination with a widely used tumoricidal chemotherapeutic, Doxorubicin. We find a common specific requirement for BIM during MYC-induced apoptosis in multiple settings, which does not extend to the p53-responsive BH3 family member PUMA, and find no evidence of a role for p19ARF during MYC-induced apoptosis in the tissues examined. MYC-ER ChIP-Seq with HC20 anti-ER antibody in MCF10A cells performed on an Illumina IIx Genome Analyzer.
Project description:Here we showed that SOX7 was significantly downregulated in different cancer types, especially in lung and breast cancers. Low expression of SOX7 was associated with advanced stage of cancer with shorter overall survival. Cancer cells with loss of SOX7 promoted cell survival and colony formation, suppressed cellular apoptosis and produced a drug resistant phenotype against a variety of chemo/targeting therapeutic agents. Mechanistically, SOX7 induced cellular apoptosis through upregulation of genes associated with both P38 and apoptotic signaling pathway, as well as preventing the proteasome mediated degradation of pro-apoptotic protein BIM. Treatment of either a proteasome inhibitor MG132 or bortezomib, or with a p-ERK/MEK inhibitor U0126 attenuate the SOX7 promoted BIM degradation.
Project description:C-MYC (henceforth MYC) is one of the most frequently overexpressed oncogenes in human cancer and even modestly deregulated MYC expression can initiate ectopic proliferation in many post-mitotic, terminally differentiated cell types in vivo. Metazoan organisms have consequently evolved a number of mechanisms to counteract MYC's oncogenic potential, of which apoptosis is arguably the best understood. However, the mechanisms through which MYC induces apoptosis remains controversial, with some studies implicating p19ARF-mediated stabilization of p53, followed by induction of pro-apoptotic BH3 family member NOXA and PUMA, while others argue for more direct regulation of BH3 proteins, especially BIM. The debate likely stems from the use of different experimental systems, modes of perturbation, and quite possibly different levels of MYC expression. Here, we use a single experimental system to systematically evaluate the roles of p19ARF and BIM during MYC-induced apoptosis, in vitro, in vivo, and in combination with a widely used tumoricidal chemotherapeutic, Doxorubicin. We find a common specific requirement for BIM during MYC-induced apoptosis in multiple settings, which does not extend to the p53-responsive BH3 family member PUMA, and find no evidence of a role for p19ARF during MYC-induced apoptosis in the tissues examined.
Project description:HHEX KD led to the differential expression of genes in pathway or cellular function related to cell proliferation and anti-apoptosis
Project description:Purpose: Epithelial-to-mesenchymal transition (EMT) confers resistance to a number of targeted therapies and chemotherapies. However, it has been unclear why EMT promotes resistance, thereby impairing progress to overcome it. Experimental Design: We have developed several models of EMT-mediated resistance to EGFR inhibitors (EGFRi) in EGFR mutant lung cancers to evaluate a novel mechanism of EMT-mediated resistance. Results: We observed that mesenchymal EGFR mutant lung cancers are resistant to EGFRi-induced apoptosis via insufficient expression of BIM, preventing cell death despite potent suppression of oncogenic signaling following EGFRi treatment. Mechanistically, we observed that the EMT transcription factor ZEB1 inhibits BIM expression by binding directly to the BIM promoter and repressing transcription. De-repression of BIM expression by depletion of ZEB1 or treatment with the BH3 mimetic ABT-263 to enhance “free” cellular BIM levels both led to re-sensitization of mesenchymal EGFR mutant cancers to EGFR inhibitors. This relationship between EMT and loss of BIM is not restricted to EGFR mutant lung cancers as it was also observed in KRAS mutant lung cancers and large datasets including different cancer subtypes. Conclusions: Altogether, these data reveal a novel mechanistic link between EMT and resistance to lung cancer targeted therapies.
Project description:Paracetamol (acetaminophen, APAP) overdose severely damages mitochondria and triggers several apoptotic processes in hepatocytes, but the final outcome is fulminant necrotic cell death, resulting in acute liver failure and mortality. Here, we studied this switch of cell death modes and demonstrate a non-canonical role of the apoptosis-regulating BCL-2 homolog BIM/Bcl2l11 in promoting necrosis by regulating cellular bioenergetics. BIM deficiency enhanced total ATP production and shifted the bioenergetic profile towards glycolysis, resulting in persistent protection from APAP-induced liver injury. Modulation of glucose levels and deletion of mitofusins confirmed that severe APAP toxicity occurs only in cells dependent on oxidative phosphorylation. Glycolytic hepatocytes maintained elevated ATP levels and reduced ROS, which enabled lysosomal recycling of damaged mitochondria by mitophagy. The present study highlights how metabolism and bioenergetics affect drug-induced liver toxicity, and identifies BIM as important regulator of glycolysis, mitochondrial respiration, and oxidative stress signaling.