Bcl-2 Family Research Articles

Abstract A024: Assessing Mitondiral Priming in Leukemia Using BH3 Complex Specific Antibodies (PRIMABS): Prediciting Patient Response to Apoptosis Inducing Drugs

Abstract Diagnostic tools for cancer therapy that enable oncologists to inform patients about the likely benefits of their treatment versus toxicity will empower patients to make evidence-based decisions about the management of their disease, and in some cases, their last phase of life. Here we provide a novel approach that measures key drug response features of individual cancer cells with the potential for providing prognostic/predictive diagnostic utility for practicing precision medicine. Most cancer treatments work though activation of the cell suicide program of apoptosis. This process is tightly regulated by the BCL-2 family of proteins whose members either prevent or promote cell death. The relative levels of, and the specific interactions between the pro-survival and pro-apoptotic family members that dictates the fate of all cells and determines their propensity to undergo apoptosis. Cells that more readily die in response to various stimuli are referred to as “primed”. Hence, the degree of priming of a tumor sample can be predictive of responses to anti-cancer drugs and can be established using a technique called “BH3 profiling”. The relevance of this method has been demonstrated but it has had only limited application. To address this limitation a unique panel of antibody-based reagents that are mitochondrial PRIMing state detecting Antibodies (PRIMABS), have been developed by our lab, as a novel approach to implementing personalized medicine and developing predicative diagnostic tests. These antibodies enable the degree of tumor cell priming to be determined directly, unlike BH3 profiling which is an indirect measure. The key innovation lies in the approach taken to determine the presence (or absence) of the critical pro-survival : pro-apoptotic protein complexes , as these are the principal determinants of cell priming.. Such PRIMAB reagents have hitherto not been available. Here we provide data outlining the methodology development as well as evidence demonstrating feasibility of PRIMABTM Dx platform for predicting AML and CLL patient response in retrospective studies. Our platform provides a PD biomarker that will become a clinical predictor of cancer cell response to treatments tat are intended to induce apopstosis in tumor cells. The PRIMABTM -DX platform will enable heretofore hard to achieve clinical applicability of priming measurements. This will be significant due to the important prognostic implications of PRIMAB-DxTM readouts and will provide insights into drug resistance and sensitivity mechanisms and lead to new treatment options for cancer patients. Citation Format: Michael Cardone. Assessing Mitondiral Priming in Leukemia Using BH3 Complex Specific Antibodies (PRIMABS): Prediciting Patient Response to Apoptosis Inducing Drugs [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr A024.

TMET-22. OVERCOMING RESISTANCE: PANOBINOSTAT SENSITIZES 2DG-RESISTANT PEDIATRIC HIGH-GRADE GLIOMAS WITH H3.3 K27M/G34R MUTATIONS TO APOPTOSIS

Abstract BACKGROUND Pediatric high-grade gliomas (pHGG) harboring H3.3 K27M/G34R mutations present formidable challenges in treatment due to their aggressiveness and resistance to standard chemotherapy. Our preliminary investigations have shown promising results, indicating that combining 2-deoxyglucose (2DG), a glycolytic inhibitor, with DNA-damaging agents synergistically inhibits pHGG growth. However, prolonged exposure to 2DG induces resistance, necessitating the exploration of alternative therapies. This study aims to investigate the potential of panobinostat, a histone deacetylase inhibitor, in sensitizing 2DG-resistant pHGG with H3.3 K27M/G34R mutations to apoptosis. METHODS Transcriptomic analysis via Illumina NovaSeq 6000 and metabolomic profiling employing Liquid Chromatography-High-Resolution Mass Spectrometry was used to delineate the molecular landscape of naive and 2DG-resistant pHGG cell lines. Functional assays, including the Agilent Seahorse Mito Stress Test and flow cytometry, assessed bioenergetics and mitochondrial dynamics. Intracellular NAD+ and NADH levels were quantified utilizing NAD+/NADH Glo assays, while apoptotic markers and metabolic stress were measured using the Annexin V-FITC Conjugates for Apoptosis Detection kit and western blot. RESULTS Comparative analysis revealed increased transketolase activity in 2DG-resistant cells, augmenting the interaction between the pentose phosphate pathway and glycolysis, resulting in elevated levels of NADPH and ATP. Additionally, these resistant cells displayed enhanced reliance on mitochondrial energy metabolism, as evidenced by substantial increases in mitochondrial membrane potential and mass, coupled with elevated NAD+ levels. Subsequent treatment with panobinostat induced a significant decrease in NAD+ biosynthesis and ATP generation. Furthermore, this intervention triggered the upregulation of pro-apoptotic BCL-2 family proteins, particularly BAX and BAK, concomitant with a notable reduction in mitochondrial membrane potential and the accumulation of reactive oxygen species. Consequently, heightened caspase-3 activity ensued, leading to significantly elevated cell death rates in 2DG-resistant gliomas. CONCLUSION Our findings highlight panobinostat as a promising therapy to resensitize 2DG-resistant pHGG cells to apoptosis, offering hope for treating these aggressive tumors with H3.3 K27M/G34R mutations.

Apoptosis: A Comprehensive Overview of Signaling Pathways, Morphological Changes, and Physiological Significance and Therapeutic Implications

Cell survival and death are intricately governed by apoptosis, a meticulously controlled programmed cell death. Apoptosis is vital in facilitating embryonic development and maintaining tissue homeostasis and immunological functioning. It is a complex interplay of intrinsic and extrinsic signaling pathways that ultimately converges on executing the apoptotic program. The extrinsic pathway is initiated by the binding of death ligands such as TNF-α and Fas to their respective receptors on the cell surface. In contrast, the intrinsic pathway leads to increased permeability of the outer mitochondrial membrane and the release of apoptogenic factors like cytochrome c, which is regulated by the Bcl-2 family of proteins. Once activated, these pathways lead to a cascade of biochemical events, including caspase activation, DNA fragmentation, and the dismantling of cellular components. Dysregulation of apoptosis is implicated in various disorders, such as cancer, autoimmune diseases, neurodegenerative disorders, and cardiovascular diseases. This article focuses on elucidating the molecular mechanisms underlying apoptosis regulation, to develop targeted therapeutic strategies. Modulating apoptotic pathways holds immense potential in cancer treatment, where promoting apoptosis in malignant cells could lead to tumor regression. This article demonstrates the therapeutic potential of targeting apoptosis, providing options for treating cancer and neurological illnesses. The safety and effectiveness of apoptosis-targeting drugs are being assessed in ongoing preclinical and clinical trials (phase I–III), opening the door for more effective therapeutic approaches and better patient outcomes.

Osteosarcoma cells depend on MCL-1 for survival, and osteosarcoma metastases respond to MCL-1 antagonism plus regorafenib in vivo

Osteosarcoma is the most common form of primary bone cancer, which primarily afflicts children and adolescents. Chemotherapy, consisting of doxorubicin, cisplatin and methotrexate (MAP) increased the 5-year osteosarcoma survival rate from 20% to approximately 60% by the 1980s. However, osteosarcoma survival rates have remained stagnant for several decades. Patients whose disease fails to respond to MAP receive second-line treatments such as etoposide and, in more recent years, the kinase inhibitor regorafenib. BCL-2 and its close relatives enforce cellular survival and have been implicated in the development and progression of various cancer types. BH3-mimetics antagonize pro-survival members of the BCL-2 family to directly stimulate apoptosis. These drugs have been proven to be efficacious in other cancer types, but their use in osteosarcoma has been relatively unexplored to date. We investigated the potential efficacy of BH3-mimetics against osteosarcoma cells in vitro and examined their cooperation with regorafenib in vivo. We demonstrated that osteosarcoma cell lines could be killed through inhibition of MCL-1 combined with BCL-2 or BCL-xL antagonism. Inhibition of MCL-1 also sensitized osteosarcoma cells to killing by second-line osteosarcoma treatments, particularly regorafenib. Importantly, we found that inhibition of MCL-1 with the BH3-mimetic S63845 combined with regorafenib significantly prolonged the survival of mice bearing pulmonary osteosarcoma metastases. Together, our results highlight the importance of MCL-1 in osteosarcoma cell survival and present a potential therapeutic avenue that may improve metastatic osteosarcoma patient outcomes.

Bax expression impacts postnatal retinal vascular development and hyperoxia sensitivity

Apoptosis plays prominent roles during organ development, maturation and homeostasis. In the retina, Bcl-2 family members function through the intrinsic cell death pathway with vital roles during vascular development and hyperoxia-mediated vessel obliteration during oxygen induced ischemic retinopathy (OIR). Bim, a BH3 only protein Bcl-2 family member, binds and activates Bax and/or Bak to facilitate apoptosis. In some systems deletion of both Bax and Bak are required to prevent cell loss, such as regression of ocular hyaloid vasculature. We previously showed Bim expression significantly impacts normal retinal vascular development and sensitivity to hyperoxia. Mice deficient in Bim (Bim-/-) show increased retinal vascular density and are protected from hyperoxia mediated vessel obliteration. Since Bim activates Bax, here we determined the impact lack of Bax expression has on these processes. Compared to Bax+/+ mice, retinas from Bax-/- mice had significantly increased numbers of retinal endothelial cells and pericytes. We also demonstrated that hyperoxia-mediated vessel obliteration during OIR was significantly decreased in the absence of Bax. Although the increased endothelial cell numbers were comparable to that of Bim-/- mice, the increased numbers of pericytes were not to the extent noted in Bim-/- mice. These changes were supported by partial protection of retinal vessels from hyperoxia in Bax-/- mice compared to that noted in Bim-/- mice. Thus, Bim-Bax driven pathway is sufficient to remove excess endothelial cells but not pericytes during postnatal retinal vascularization and hyperoxia-mediated vessel obliteration. Thus, additional Bim-mediated pathway(s) are required for removal of pericytes and hyperoxia-mediated vessel obliteration.

Oncogenic KRAS mutations modulate BAX-mediated cell death

Kirsten rat sarcoma viral oncogene homolog (KRAS) belongs to the GTPase RAS superfamily, which regulates several cell-signaling pathways involved in the control of important cellular functions, including apoptosis. Oncogenic mutations in KRAS are considered the most common gain-of-function mutations, affecting 30–50 % of colorectal cancer (CRC) patients. While RAS proteins usually play an anti-apoptotic role, little is known about the involvement of KRAS mutations in apoptosis regulation. Here, we aimed to elucidate the role of mutated human KRAS in the regulation of BAX, a key pro-apoptotic member of the Bcl-2 family. For this purpose, we took advantage of the simpler yeast model Saccharomyces cerevisiae, using cells deficient in the main yeast RAS isoform (ras2Δ) co-expressing wild-type KRAS (KRASWT) or the most frequent KRAS mutations found in CRC - KRASG12D, KRASG12V or KRASG13D, along with human BAX. We show that, in comparison with KRASWT, KRAS mutants confer resistance to BAX-induced death and cytochrome c (cyt c) release. The modulation of BAX by KRAS isoforms seems to result from a direct interaction between these proteins, as they co-localize at the mitochondria and there is evidence they may physically interact. We further show that acetic acid significantly increased cell death in cells expressing BAX and co-expressing oncogenic KRAS mutants, but not KRASWT. This suggests a potential mechanism explaining the increased sensitivity of CRC cells harboring a KRAS-activated pathway to acetate. These findings contribute to a clearer understanding of how KRAS regulate BAX function, a relevant aspect in tumor progression.

PX-478 induces apoptosis in acute myeloid leukemia under hypoxia by inhibiting the PI3K/AKT/mTOR pathway through downregulation of GBE1

Acute myeloid leukemia (AML) is a highly heterogeneous hematologic malignancy characterized by limited therapeutic options and a pronounced tendency for relapse. PX-478, a novel inhibitor of hypoxia-inducible factor 1-alpha (HIF-1α), has demonstrated antitumor activity across various cancer models, but its specific role in AML remains unexplored. This study aimed to explore the potential target and mechanism of PX-478-induced AML cell apoptosis. First, PX-478 induced AML cell apoptosis in vitro under hypoxia via modulation of the Bcl-2 family and activation of the mitochondria-mediated caspase cascade, exhibiting a concentration-dependent effect. Additionally, in vivo administration of PX-478 led to notable inhibition of subcutaneous AML xenograft growth in mice, coupled with increased tumor cell apoptosis. RNA sequencing and cellular studies revealed downregulation of the PI3K/AKT/mTOR signaling pathway in PX-478-treated cells. Consistently, cellular studies also implicated PI3K/AKT/mTOR pathway in PX-478-induced AML cell apoptosis. Furthermore, by screening for RNA sequencing differential genes and subsequent experimental verification, Glycogen branching enzyme 1 (GBE1) may be involved in PX-478-induced apoptosis in AML cells. We found that inhibiting GBE1 expression in AML cells (siGBE1) led to downregulation of the PI3K/AKT/mTOR pathway and induced apoptosis. In experiments using AML cells with reduced GBE1 expression (shGBE1), PX-478 treatment did not further downregulate the pathway or enhance apoptosis. Re-expression of GBE1 in shGBE1 cells alleviated apoptosis and reduced PX-478- induced apoptosis and pathway downregulation. In conclusion, our findings provide convincing evidence that PX-478 induces apoptosis by inhibiting the PI3K/AKT/mTOR pathway through downregulation of GBE1 in AML cells

Caspase-2 kills cells with extra centrosomes.

Centrosomes are membrane-less organelles that orchestrate a wide array of biological functions by acting as microtubule organizing centers. Here, we report that caspase-2-driven apoptosis is elicited in blood cells failing cytokinesis and that extra centrosomes are necessary to trigger this cell death. Activation of caspase-2 depends on the PIDDosome multi-protein complex, and priming of PIDD1 at extra centrosomes is necessary for pathway activation. Accordingly, loss of its centrosomal adapter, ANKRD26, allows for cell survival and unrestricted polyploidization in response to cytokinesis failure. Mechanistically, cell death is initiated upstream of mitochondria via caspase-2-mediated processing of the BCL2 family protein BID, driving BAX/BAK-dependent mitochondrial outer membrane permeabilization (MOMP). Remarkably, BID-deficient cells enforce apoptosis by engaging p53-dependent proapoptotic transcriptional responses initiated by caspase-2. Consistently, BID and MDM2 act as shared caspase-2 substrates, with BID being kinetically favored. Our findings document that the centrosome limits its own unscheduled duplication by the induction of PIDDosome-driven mitochondrial apoptosis to avoid potentially pathogenic polyploidization events.

Characterizing and Targeting of BCL-2 Family Members in Nasopharyngeal Carcinoma.

The success of BH3 mimetics in hematological malignancies has spurred interest in their application in solid tumors. We examined the expression of the BCL-2 family of molecules in NPC tumors and cell lines and explored the anticancer efficacy of BH3 mimetics invitro. Immunohistochemistry for BCL-2, MCL-1, BCL-xL, and transcriptomic analyses was conducted on NPC tumors. The efficacy of ABT-199, S63845, and ABT-737 were examined as monotherapy and in combination with cisplatin in NPC cell lines. RNA sequencing was performed to identify up and downregulated pathways in sensitive cell lines. One hundred and forty-nine EBV-positive NPC and 15 EBV-negative NPC were identified. Expression of BCL-2 was more frequent in EBV-positive NPC. BCL-2, MCL-1, and BCL-xL expression was not prognostic for overall survival. Marked sensitivity was seen with the combination of S63845 and cisplatin in NPC43. Our study demonstrates the therapeutic potential of combining cisplatin and S63845, which warrants further investigation.

RAS-mutant leukaemia stem cells drive clinical resistance to venetoclax.

Cancer driver mutations often show distinct temporal acquisition patterns, but the biological basis for this, if any, remains unknown. RAS mutations occur invariably late in the course of acute myeloid leukaemia, upon progression or relapsed/refractory disease1-6. Here, by using human leukaemogenesis models, we first show that RAS mutations are obligatory late events that need to succeed earlier cooperating mutations. We provide the mechanistic explanation for this in a requirement for mutant RAS to specifically transform committed progenitors of the myelomonocytic lineage (granulocyte-monocyte progenitors) harbouring previously acquired driver mutations, showing that advanced leukaemic clones can originate from a different cell type in the haematopoietic hierarchy than ancestral clones. Furthermore, we demonstrate that RAS-mutant leukaemia stem cells (LSCs) give rise to monocytic disease, as observed frequently in patients with poor responses to treatment with the BCL2 inhibitor venetoclax. We show that this is because RAS-mutant LSCs, in contrast to RAS-wild-type LSCs, have altered BCL2 family gene expression and are resistant to venetoclax, driving clinical resistance and relapse with monocytic features. Our findings demonstrate that a specific genetic driver shapes the non-genetic cellular hierarchy of acute myeloid leukaemia by imposing a specific LSC target cell restriction and critically affects therapeutic outcomes in patients.

Quantitative chemical proteomics reveals that phenethyl isothiocyanate covalently targets BID to promote apoptosis

Naturally occurring isothiocyanates (ITCs) found in cruciferous vegetables, such as benzyl isothiocyanate (BITC), phenethyl isothiocyanate (PEITC), and sulforaphane (SFN), have attracted significant research interest for their promising anti-cancer activity in vitro and in vivo. While the induction of apoptosis is recognized to play a key role in the anti-cancer effects of ITCs, the specific protein targets and associated upstream events underlying ITC-induced apoptosis remain unknown. In this study, we present a set of chemical probes that are derived from BITC, PEITC, and SFN and equipped with bioorthogonal alkynyl handles to systematically profile the target proteins of ITCs in live cancer cells. Using a competition-based quantitative chemical proteomics approach, we identify a range of candidate target proteins of ITCs enriched in biological processes such as apoptosis. We show that BID, an apoptosis regulator of the Bcl-2 family, is covalently modified by ITCs on its N-terminal cysteines. Functional characterization demonstrates that covalent binding to N-terminal cysteines of BID by PEITC results in conformational changes of the protein and disruption of the self-inhibitory interaction between N- and C-terminal regions of BID, thus unleashing the highly active C-terminal segment to exert downstream pro-apoptotic effects. Consistently, PEITC promotes the cleavage and mitochondrial translocation of BID, leading to a strong induction of apoptosis. We further show that mutation of N-terminal cysteines impairs the N- and C-terminal interaction of BID, relieving the self-inhibition and enhancing its apoptotic activity. Overall, our chemical proteomics profiling and functional studies not only reveal BID as the principal target of PEITC in mediating upstream events for the induction of apoptosis, but also uncover a novel molecular mechanism involving N-terminal cysteines within the first helix of BID in regulating its pro-apoptotic potential.

Apoptosis signaling is activated as a transient pulse in neurons.

Apoptosis is a fundamental process of all mammalian cells but exactly how it is regulated in different primary cells remains less explored. In most contexts, apoptosis is engaged to eliminate cells. However, postmitotic cells such as neurons must efficiently balance the need for developmental apoptosis versus the physiological needs for their long-term survival. Neurons are capable of reversing the commitment to death even after the point of cytochrome c release. This ability of neurons to recover from an apoptotic signal suggests that activation of the apoptotic pathway in neurons could be much more transient than is currently recognized. Here, we investigated whether the apoptotic pathway in neurons is a persistent signal or a transient pulse in continuous presence of apoptotic stimulus. We have examined this at three key steps in apoptotic signaling: phosphorylation of c-Jun, induction of the BH3-only family proteins and Bax activation. Strikingly, we found all three of these events occur as transient signals following Nerve Growth Factor (NGF) deprivation-induced apoptosis in sympathetic neurons. This transient apoptosis signal would effectively allow neurons to reset and permit recovery if the apoptotic stimulus is reversed. Excitingly, we have also discovered that a neuron's ability to recover from an apoptotic signal is dependent on expression of the anti-apoptotic Bcl-2 family protein Bcl-xL. Bcl-xL-deficient neurons lose the ability to recover from NGF deprivation even if NGF is restored. Additionally, we show that recovery from a previous exposure to NGF deprivation is protective against subsequent deprivation. Together, these results define a novel mechanism by which apoptosis is regulated in neurons where the transient pulse of the apoptotic signaling supports neuronal resilience.

ETFDH mutation involves excessive apoptosis and neurite outgrowth defect via Bcl2 pathway

The most common mutation in southern Chinese individuals with late-onset multiple acyl-coenzyme A dehydrogenase deficiency (MADD; a fatty acid metabolism disorder) is c.250G > A (p.Ala84Thr) in the electron transfer flavoprotein dehydrogenase gene (ETFDH). Various phenotypes, including episodic weakness or rhabdomyolysis, exercise intolerance, and peripheral neuropathy, have been reported in both muscular and neuronal contexts. Our cellular models of MADD exhibit neurite growth defects and excessive apoptosis. Given that axonal degeneration and neuronal apoptosis may be regulated by B-cell lymphoma (BCL)-2 family proteins and mitochondrial outer membrane permeabilization through the activation of proapoptotic molecules, we measured the expression levels of proapoptotic BCL-2 family proteins (e.g., BCL-2-associated X protein and p53-upregulated modulator of apoptosis), cytochrome c, caspase-3, and caspase-9 in NSC-34 cells carrying the most common ETFDH mutation. The levels of these proteins were higher in the mutant cells than in the wide-type cells. Subsequent treatment of the mutant cells with coenzyme Q10 downregulated activated protein expression and mitigated neurite growth defects. These results suggest that the activation of the BCL-2/mitochondrial outer membrane permeabilization/apoptosis pathway promotes apoptosis in cellular models of MADD and that coenzyme Q10 can reverse this effect. Our findings aid the development of novel therapeutic strategies for reducing axonal degeneration and neuronal apoptosis in MADD.

Role of layilin in regulating mitochondria-mediated apoptosis: a study on B cell lymphoma (BCL)-2 family proteins

BackgroundMalignant gliomas exhibit rapid tumor progression and resistance to treatment, leading to high lethality. One of the causes is the reduced progression of apoptosis in glioma cells. Layilin is a type 1 transmembrane protein with a C-type lectin motif in its extracellular domain. We previously reported that layilin is mainly localized to mitochondria or their close proximity and that layilin is essential for maintaining of the fragmented type of mitochondria. This study investigates the effects of layilin on mitochondria-mediated apoptosis, focusing on B cell lymphoma (BCL)-2 family proteins in a glioma cell line of A172 cells.ResultsWe compared the levels of pro-apoptotic BCL-2 family proteins of BAD, BAK, BAX, and BIM and anti-apoptotic BCL-2 family proteins of BCL-2 and BCL-XL between layilin- knockdown (KD) cells and control cells using western blot. The protein levels of BAD were significantly smaller in layilin-KD cells than in control cells, while those of BCL-2 were significantly larger. We then compared the mitochondrial membrane potential (ΔΨm) under p-trifluoromethoxyphenyl hydrazone (FCCP)-treated conditions using MT-1 staining. In layilin-KD cells, ΔΨm was significantly larger and FCCP-induced ΔΨm reduction was significantly lower than in control cells. Furthermore, we examined the levels of cell membrane-bound Annexin V and DNA-bound propidium idodide (PI) in layilin-KD cells with/without staurosporine (STS) treatment. Layilin-KD significantly decreased levels of cell membrane-bound Annexin V with/without STS treatment. On the other hand, PI levels were not changed by layilin-KD. We also investigated the amounts of the active caspase (CASP)-3, CASP-6, CASP-7, and poly (ADP-ribose) polymerase-1 (PARP1, cleaved form), as well as DNA fragmentation in layilin-KD cells under apoptotic conditions induced by STS, using western blot and the DNA ladder method, respectively. Under STS-treated conditions, the amounts of active CASP-3, CASP-7, and poly (ADP-ribose) PARP1 were significantly smaller in layilin-KD cells than in control cells. Accordingly, DNA fragmentation was significantly suppressed in layilin-KD cells compared to control cells under STS-treated conditions.ConclusionThis study demonstrates that layilin contributes to ΔΨm reduction to promote apoptosis by up-regulating BAD and down-regulating BCL-2 in glioma cells. Our data elucidates a new function of layilin: regulation of mitochondria-mediated apoptosis.

Inhibition of BAK-mediated apoptosis by the BH3-only protein BNIP5.

BCL-2 family proteins regulate apoptosis by initiating mitochondrial outer membrane permeabilization (MOMP). Activation of the MOMP effectors BAX and BAK is controlled by the interplay of anti-apoptotic BCL-2 proteins (e.g., MCL-1) and pro-apoptotic BH3-only proteins (e.g., BIM). Using a genome-wide CRISPR-dCas9 transactivation screen we identified BNIP5 as an inhibitor of BAK-, but not BAX-induced apoptosis. BNIP5 blocked BAK activation in different cell types and in response to various cytotoxic therapies. The BH3 domain of BNIP5 was both necessary and sufficient to block BAK activation. Mechanistically, the BH3 domain of BNIP5 acts as a selective BAK activator, but a poor de-repressor of complexes between BAK and pro-survival BCL-2 family proteins. By promoting the binding of activated BAK to MCL-1 or BCL-xL, BNIP5 inhibits apoptosis when BAX is absent. Based on our observations, BNIP5 can act functionally as an anti-apoptotic BH3-only protein.

The pro-apoptotic function of the C. elegans BCL-2 homolog CED-9 requires interaction with the APAF-1 homolog CED-4.

In Caenorhabditis elegans, apoptosis is inhibited by the BCL-2 homolog CED-9. Although canonically anti-apoptotic, CED-9 has a poorly understood pro-apoptotic function. CED-9 is thought to inhibit apoptosis by binding to and inhibiting the pro-apoptotic C. elegans APAF-1 homolog CED-4. We show that CED-9 or CED-4 mutations located in their CED-9-CED-4 binding regions reduce apoptosis without affecting the CED-9 anti-apoptotic function. These mutant CED-9 and CED-4 proteins are defective in a CED-9-CED-4 interaction in vitro and in vivo, revealing that the known CED-9-CED-4 interaction is required for the pro-apoptotic but not for the anti-apoptotic function of CED-9. The pro-apoptotic CED-9-CED-4 interaction occurs at mitochondria. In mammals, BCL-2 family members can activate APAF-1 via cytochrome c release from mitochondria. The conserved role of mitochondria in CED-9/BCL-2-dependent CED-4/APAF-1 activation is notable and suggests that understanding how CED-9 promotes apoptosis in C. elegans could inform the understanding of mammalian apoptosis and how disruptions of apoptosis promote certain human disorders.

Targeting Bcl-2 with Indole Scaffolds: Emerging Drug Design Strategies for Cancer Treatment.

The B-cell lymphoma-2 (Bcl-2) protein family plays a crucial role as a regulator in the process of apoptosis. There is a substantial body of evidence indicating that the upregulation of antiapoptotic Bcl-2 proteins is prevalent in several cancer cell lines and original tumour tissue samples. This phenomenon plays a crucial role in enabling tumour cells to avoid apoptosis, hence facilitating the development of resistant cells against chemotherapy. Therefore, the success rate of chemotherapy for cancer can be enhanced by the down-regulation of anti-apoptotic Bcl-2 proteins. Furthermore, the indole structural design is commonly found in a variety of natural substances and biologically active compounds, particularly those that possess anti-cancer properties. Due to its distinctive physicochemical and biological characteristics, it has been highly regarded as a fundamental framework in the development and production of anti-cancer drugs. As a result, a considerable range of indole derivatives, encompassing both naturally occurring and developed compounds, have been identified as potential candidates for the treatment of cancer. Several of these derivatives have advanced to clinical trials, while others are already being used in clinical settings. This emphasizes the significant role of indole in the field of research and development of anti-cancer therapeutics. This study provides an overview of apoptosis and the structural characteristics of Bcl-2 family proteins, and mainly examines the present stage and recent developments in Bcl-2 inhibitors with an indole scaffold embedded in their structure.

Caspase-3 interactins with calpain and cathepsin L: implications for protein stability and quality in fish fillets during postmortem storage

The degradation of structural proteins during fish postmortem storage is a critical factor affecting meat quality, leading to economic losses in the seafood industry. The complex interplay between caspase-3 and structural protein stability during fish postmortem storage remains largely unexplored. By treating grass carp fillets with a caspase-3 inhibitor, we establish a model for inhibiting apoptosis, delineating the role of caspase-3 in protein degradation. The effect of caspase-3 on grass carp proteins following postmortem storage and its cascade interaction with calpain and cathepsin L was further investigated. The result demonstrated that the destabilisation of the mitochondrial membrane during apoptosis led to modifications in the B-cell lymphoma (Bcl) family proteins, subsequently triggered the activation of caspase-9/caspase-3. Additionally, caspase-3 reduced the expression of the calpastatin and lysosomal membrane protein 1 (LAMP-1) gene, resulting in increased calpain and cathepsin L activity. SDS-PAGE and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis indicated that caspase-3 inhibitor treatment reduced actin fractures and preserved critical structural proteins. This investigation unveils the molecular mechanisms through which caspase-3 affects protein degradation in fish fillets during storage, providing valuable insights into the postmortem degradation processes.

Establishment of BCL-2 Inhibitors-Resistant B-cell Acute Lymphoblastic Leukemia Cell Lines and Study on Their Resistance Mechanisms

RS4;11 cell line was used to establish BCL-2 inhibitor-resistant cell lines of B-cell acute lymphoblastic leukemia (B-ALL) and explore the possible mechanisms of drug resistance. RS4;11 cell line was continuously induced and cultured by low and ascending concentrations of BCL-2 inhibitors navitoclax and venetoclax to construct navitoclax-resistant cell line RS4;11/Nav and venetoclax-resistant cell line RS4;11/Ven. The cell viability was detected by MTT assay, and the cell apoptosis was detected by flow cytometry. Differentially expressed genes (DEGs) between RS4;11 drug-resistant cell lines and parental cell line were detected by transcriptome sequencing technology (RNA-seq), and mRNA expression levels of DEGs between drug-resistant cell lines and parental cell line were detected by real-time PCR (RT-PCR). Western blot was used to detect the expression levels of BCL-2 family anti-apoptotic proteins in drug-resistant cell lines and parental cell line. The drug-resistant cell lines RS4;11/Nav and RS4;11/Ven were successfully established. The resistance index (RI) of RS4;11/Nav to navitoclax and RS4;11/Ven to venetoclax was 328.655±47.377 and 2 894.027±300.311, respectively. The results of cell apoptosis detection showed that compared with the drug-resistant cell lines, RS4;11 parental cell line were significantly inhibited by BCL-2 inhibitors, while the apoptosis rate of drug-resistant cell lines was not affected by the drugs. Western blot assay showed that the expression of anti-apoptotic proteins of BCL-2 family did not increase significantly in drug-resistant cell lines. RNA-seq, RT-PCR and Western blot assays showed that the expression of EP300 in drug-resistant cell lines was significantly higher than that in parental cell line (P <0.05). Drug-resistant B-ALL cell lines could be successfully established by exposing RS4;11 cell line to the ascending concentration of BCL-2 inhibitors, and the drug resistance mechanism may be related to the overexpression of EP300.

248 (PB236): Identification of inhibitors of BCL2 family members and glucose metabolism as effective combination partners of belinostat in T-cell lymphoma (TCL) cell lines

248 (PB236): Identification of inhibitors of BCL2 family members and glucose metabolism as effective combination partners of belinostat in T-cell lymphoma (TCL) cell lines