Medical Biology - Research Publications

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    Some mice lacking intrinsic, as well as death receptor induced apoptosis and necroptosis, can survive to adulthood.
    Ke, FFS ; Brinkmann, K ; Voss, AK ; Strasser, A (Springer Science and Business Media LLC, 2022-04-07)
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    Removal of BFL-1 sensitises some melanoma cells to killing by BH3 mimetic drugs
    Gangoda, L ; Schenk, RL ; Tai, L ; Szeto, P ; Cheung, JG ; Strasser, A ; Lessene, G ; Shackleton, M ; Herold, MJ (SPRINGERNATURE, 2022-04-04)
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    In vivo genome-editing screen identifies tumor suppressor genes that cooperate with Trp53 loss during mammary tumorigenesis
    Heitink, L ; Whittle, JR ; Vaillant, F ; Capaldo, BD ; Dekkers, JF ; Dawson, CA ; Milevskiy, MJG ; Surgenor, E ; Tsai, M ; Chen, H-R ; Christie, M ; Chen, Y ; Smyth, GK ; Herold, MJ ; Strasser, A ; Lindeman, GJ ; Visvader, JE (WILEY, 2022-01-26)
    Breast cancer is a heterogeneous disease that comprises multiple histological and molecular subtypes. To gain insight into mutations that drive breast tumorigenesis, we describe a pipeline for the identification and validation of tumor suppressor genes. Based on an in vivo genome-wide CRISPR/Cas9 screen in Trp53+/- heterozygous mice, we identified tumor suppressor genes that included the scaffold protein Axin1, the protein kinase A regulatory subunit gene Prkar1a, as well as the proof-of-concept genes Pten, Nf1, and Trp53 itself. Ex vivo editing of primary mammary epithelial organoids was performed to further interrogate the roles of Axin1 and Prkar1a. Increased proliferation and profound changes in mammary organoid morphology were observed for Axin1/Trp53 and Prkar1a/Trp53 double mutants compared to Pten/Trp53 double mutants. Furthermore, direct in vivo genome editing via intraductal injection of lentiviruses engineered to express dual short-guide RNAs revealed that mutagenesis of Trp53 and either Prkar1a, Axin1, or Pten markedly accelerated tumor development compared to Trp53-only mutants. This proof-of-principle study highlights the application of in vivo CRISPR/Cas9 editing for uncovering cooperativity between defects in tumor suppressor genes that elicit mammary tumorigenesis.
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    Transplantable programmed death ligand 1 expressing gastroids from gastric cancer prone Nfkb1(-/-) mice
    Low, JT ; Ho, G-Y ; Scott, M ; Tan, CW ; Whitehead, L ; Barber, K ; Yip, HYK ; Dekkers, JF ; Hirokawa, Y ; Silke, J ; Burgess, AW ; Strasser, A ; Putoczki, TL ; O'Reilly, LA (SPRINGERNATURE, 2021-11-17)
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    Flexible Usage and Interconnectivity of Diverse Cell Death Pathways Protect against Intracellular Infection
    Doerflinger, M ; Deng, Y ; Whitney, P ; Salvamoser, R ; Engel, S ; Kueh, AJ ; Tai, L ; Bachem, A ; Gressier, E ; Geoghegan, ND ; Wilcox, S ; Rogers, KL ; Garnham, AL ; Dengler, MA ; Bader, SM ; Ebert, G ; Pearson, JS ; De Nardo, D ; Wang, N ; Yang, C ; Pereira, M ; Bryant, CE ; Strugnell, RA ; Vince, JE ; Pellegrini, M ; Strasser, A ; Bedoui, S ; Herold, MJ (CELL PRESS, 2020-09-15)
    Programmed cell death contributes to host defense against pathogens. To investigate the relative importance of pyroptosis, necroptosis, and apoptosis during Salmonella infection, we infected mice and macrophages deficient for diverse combinations of caspases-1, -11, -12, and -8 and receptor interacting serine/threonine kinase 3 (RIPK3). Loss of pyroptosis, caspase-8-driven apoptosis, or necroptosis had minor impact on Salmonella control. However, combined deficiency of these cell death pathways caused loss of bacterial control in mice and their macrophages, demonstrating that host defense can employ varying components of several cell death pathways to limit intracellular infections. This flexible use of distinct cell death pathways involved extensive cross-talk between initiators and effectors of pyroptosis and apoptosis, where initiator caspases-1 and -8 also functioned as executioners when all known effectors of cell death were absent. These findings uncover a highly coordinated and flexible cell death system with in-built fail-safe processes that protect the host from intracellular infections.
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    Homeostatic apoptosis prevents competition-induced atrophy in follicular B cells
    Chappaz, S ; McArthur, K ; Kealy, L ; Law, CW ; Tailler, M ; Lane, RM ; Lieschke, A ; Ritchie, ME ; Good-Jacobson, KL ; Strasser, A ; Kile, BT (CELL PRESS, 2021-07-21)
    While the intrinsic apoptosis pathway is thought to play a central role in shaping the B cell lineage, its precise role in mature B cell homeostasis remains elusive. Using mice in which mature B cells are unable to undergo apoptotic cell death, we show that apoptosis constrains follicular B (FoB) cell lifespan but plays no role in marginal zone B (MZB) cell homeostasis. In these mice, FoB cells accumulate abnormally. This intensifies intercellular competition for BAFF, resulting in a contraction of the MZB cell compartment, and reducing the growth, trafficking, and fitness of FoB cells. Diminished BAFF signaling dampens the non-canonical NF-κB pathway, undermining FoB cell growth despite the concurrent triggering of a protective p53 response. Thus, MZB and FoB cells exhibit a differential requirement for the intrinsic apoptosis pathway. Homeostatic apoptosis constrains the size of the FoB cell compartment, thereby preventing competition-induced FoB cell atrophy.
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    Intact TP-53 function is essential for sustaining durable responses to BH3-mimetic drugs in leukemias
    Thijssen, R ; Diepstraten, ST ; Moujalled, D ; Chew, E ; Flensburg, C ; Shi, MX ; Dengler, MA ; Litalien, V ; MacRaild, S ; Chen, M ; Anstee, NS ; Reljic, B ; Gabriel, SS ; Djajawi, TM ; Riffkin, CD ; Aubrey, BJ ; Chang, C ; Tai, L ; Xu, Z ; Morley, T ; Pomilio, G ; Bruedigam, C ; Kallies, A ; Stroud, DA ; Bajel, A ; Kluck, RM ; Lane, SW ; Schoumacher, M ; Banquet, S ; Majewski, IJ ; Strasser, A ; Roberts, AW ; Huang, DCS ; Brown, FC ; Kelly, GL ; Wei, AH (AMER SOC HEMATOLOGY, 2021-05-20)
    Selective targeting of BCL-2 with the BH3-mimetic venetoclax has been a transformative treatment for patients with various leukemias. TP-53 controls apoptosis upstream of where BCL-2 and its prosurvival relatives, such as MCL-1, act. Therefore, targeting these prosurvival proteins could trigger apoptosis across diverse blood cancers, irrespective of TP53 mutation status. Indeed, targeting BCL-2 has produced clinically relevant responses in blood cancers with aberrant TP-53. However, in our study, TP53-mutated or -deficient myeloid and lymphoid leukemias outcompeted isogenic controls with intact TP-53, unless sufficient concentrations of BH3-mimetics targeting BCL-2 or MCL-1 were applied. Strikingly, tumor cells with TP-53 dysfunction escaped and thrived over time if inhibition of BCL-2 or MCL-1 was sublethal, in part because of an increased threshold for BAX/BAK activation in these cells. Our study revealed the key role of TP-53 in shaping long-term responses to BH3-mimetic drugs and reconciled the disparate pattern of initial clinical response to venetoclax, followed by subsequent treatment failure among patients with TP53-mutant chronic lymphocytic leukemia or acute myeloid leukemia. In contrast to BH3-mimetics targeting just BCL-2 or MCL-1 at doses that are individually sublethal, a combined BH3-mimetic approach targeting both prosurvival proteins enhanced lethality and durably suppressed the leukemia burden, regardless of TP53 mutation status. Our findings highlight the importance of using sufficiently lethal treatment strategies to maximize outcomes of patients with TP53-mutant disease. In addition, our findings caution against use of sublethal BH3-mimetic drug regimens that may enhance the risk of disease progression driven by emergent TP53-mutant clones.
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    Molecular mechanisms of cell death in neurological diseases
    Moujalled, D ; Strasser, A ; Liddell, JR (SPRINGERNATURE, 2021-06-07)
    Tightly orchestrated programmed cell death (PCD) signalling events occur during normal neuronal development in a spatially and temporally restricted manner to establish the neural architecture and shaping the CNS. Abnormalities in PCD signalling cascades, such as apoptosis, necroptosis, pyroptosis, ferroptosis, and cell death associated with autophagy as well as in unprogrammed necrosis can be observed in the pathogenesis of various neurological diseases. These cell deaths can be activated in response to various forms of cellular stress (exerted by intracellular or extracellular stimuli) and inflammatory processes. Aberrant activation of PCD pathways is a common feature in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), Alzheimer's disease, Parkinson's disease, and Huntington's disease, resulting in unwanted loss of neuronal cells and function. Conversely, inactivation of PCD is thought to contribute to the development of brain cancers and to impact their response to therapy. For many neurodegenerative diseases and brain cancers current treatment strategies have only modest effect, engendering the need for investigations into the origins of these diseases. With many diseases of the brain displaying aberrations in PCD pathways, it appears that agents that can either inhibit or induce PCD may be critical components of future therapeutic strategies. The development of such therapies will have to be guided by preclinical studies in animal models that faithfully mimic the human disease. In this review, we briefly describe PCD and unprogrammed cell death processes and the roles they play in contributing to neurodegenerative diseases or tumorigenesis in the brain. We also discuss the interplay between distinct cell death signalling cascades and disease pathogenesis and describe pharmacological agents targeting key players in the cell death signalling pathways that have progressed through to clinical trials.
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    BCL-W is dispensable for the sustained survival of select Burkitt lymphoma and diffuse large B-cell lymphoma cell lines
    Diepstraten, ST ; Chang, C ; Tai, L ; Gong, J-N ; Lan, P ; Dowell, AC ; Taylor, GS ; Strasser, A ; Kelly, GL (AMER SOC HEMATOLOGY, 2020-01-28)
    Dysregulated expression of BCL-2 family proteins allows cancer cells to escape apoptosis. To counter this, BH3-mimetic drugs that target and inhibit select BCL-2 prosurvival proteins to induce apoptosis have been developed for cancer therapy. Venetoclax, which targets BCL-2, has been effective as therapy for patients with chronic lymphocytic leukemia, and MCL-1-targeting BH3-mimetic drugs have been extensively evaluated in preclinical studies for a range of blood cancers. Recently, BCL-W, a relatively understudied prosurvival member of the BCL-2 protein family, has been reported to be abnormally upregulated in Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL), and Hodgkin lymphoma patient samples. Therefore, to determine if BCL-W would be a promising therapeutic target for B-cell lymphomas, we have examined the role of BCL-W in the sustained growth of human BL- and DLBCL-derived cell lines. We found that CRISPR/CAS9-mediated loss or short hairpin RNA-mediated knockdown of BCL-W expression in selected BL and DLBCL cell lines did not lead to spontaneous apoptosis and had no effect on their sensitivity to a range of BH3-mimetic drugs targeting other BCL-2 prosurvival proteins. Our results suggest that BCL-W is not universally required for the sustained growth and survival of human BL and DLBCL cell lines. Thus, targeting BCL-W in this subset of B-cell lymphomas may not be of broad therapeutic benefit.
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    MCL-1 is essential for survival but dispensable for metabolic fitness of FOXP3(+)regulatory T cells
    Teh, CE ; Robbins, AK ; Henstridge, DC ; Dewson, G ; Diepstraten, ST ; Kelly, G ; Febbraio, MA ; Gabriel, SS ; O'Reilly, LA ; Strasser, A ; Gray, DHD (SPRINGERNATURE, 2020-07-01)
    FOXP3+ regulatory T (Treg) cells are essential for maintaining immunological tolerance. Given their importance in immune-related diseases, cancer and obesity, there is increasing interest in targeting the Treg cell compartment therapeutically. New pharmacological inhibitors that specifically target the prosurvival protein MCL-1 may provide this opportunity, as Treg cells are particularly reliant upon this protein. However, there are two distinct isoforms of MCL-1; one located at the outer mitochondrial membrane (OMM) that is required to antagonize apoptosis, and another at the inner mitochondrial membrane (IMM) that is reported to maintain IMM structure and metabolism via ATP production during oxidative phosphorylation. We set out to elucidate the relative importance of these distinct biological functions of MCL-1 in Treg cells to assess whether MCL-1 inhibition might impact upon the metabolism of cells able to resist apoptosis. Conditional deletion of Mcl1 in FOXP3+ Treg cells resulted in a lethal multiorgan autoimmunity due to the depletion of the Treg cell compartment. This striking phenotype was completely rescued by concomitant deletion of the apoptotic effector proteins BAK and BAX, indicating that apoptosis plays a pivotal role in the homeostasis of Treg cells. Notably, MCL-1-deficient Treg cells rescued from apoptosis displayed normal metabolic capacity. Moreover, pharmacological inhibition of MCL-1 in Treg cells resistant to apoptosis did not perturb their metabolic function. We conclude that Treg cells require MCL-1 only to antagonize apoptosis and not for metabolism. Therefore, MCL-1 inhibition could be used to manipulate Treg cell survival for clinical benefit without affecting the metabolic fitness of cells resisting apoptosis.