Inhibition Of Oxidative Phosphorylation Research Articles

Helicobacter pylori secretory Proteins-Induced oxidative stress and its role in NLRP3 inflammasome activation

Helicobacter pylori-associated stomach infection is a leading cause of gastric ulcer and related cancer. H. pylori modulates the functions of infiltrated immune cells to survive the killing by reactive oxygen and nitrogen species (ROS and RNS) produced by these cells. Uncontrolled immune responses further produce excess ROS and RNS which lead to mucosal damage. The persistent oxidative stress is a major cause of gastric cancer. H. pylori regulates nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs), nitric oxide synthase 2 (NOS2), and polyamines to control ROS and RNS release through lesser-known mechanisms. ROS and RNS produced by these pathways differentiate macrophages and T cells from protective to inflammatory phenotype. Pathogens-associated molecular patterns (PAMPs) induced ROS activates nuclear oligomerization domain (NOD), leucine rich repeats (LRR) and pyrin domain-containing protein 3 (NLRP3) inflammasome for the release of pro-inflammatory cytokines. This study evaluates the role of H. pylori secreted concentrated proteins (HPSCP) related oxidative stress role in NLRP3 inflammasome activation and macrophage differentiation. To perceive the role of ROS/RNS, THP-1 and AGS cells were treated with 10 μM diphenyleneiodonium (DPI), 50 μM salicyl hydroxamic acid (SHX), 5 μM Carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP), which are specific inhibitors of NADPH oxidase (NOX), Myeloperoxidase (MPO), and mitochondrial oxidative phosphorylation respectively. Cells were also treated with 10 μM of NOS2 inhibitor l-NMMA and 10 μM of N-acetyl cysteine (NAC), a free radical scavenger·H2O2 (100 μM) treated and untreated cells were used as positive controls and negative control respectively. The expression of gp91phox (NOX2), NOS2, NLRP3, CD86 and CD163 was analyzed through fluorescent microscopy. THP-1 macrophages growth was unaffected whereas the gastric epithelial AGS cells proliferated in response to higher concentration of HPSCP. ROS and myeloperoxidase (MPO) level increased in THP-1 cells and nitric oxide (NO) and lipid peroxidation significantly decreased in AGS cells. gp91phox expression was unchanged, whereas NOS2 and NLRP3 downregulated in response to HPSCP, but increased after inhibition of NO, ROS and MPO in THP-1 cells. HPSCP upregulated the expression of M1 and M2 macrophage markers, CD86 and CD163 respectively, which was decreased after the inhibition of ROS.This study concludes that there are multiple pathways which are generating ROS during H. pylori infection which further regulates other cellular processes. NO is closely associated with MPO and inhibition of NLRP3 inflammasome. The low levels of NO and MPO regulates gastrointestinal tract homeostasis and overcomes the inflammatory response of NLRP3. The ROS also plays crucial role in macrophage polarization hence alter the immune responses duing H. pylori pathogenesis.

Metabolic reprogramming driven by METTL1-mediated tRNA m7G modification promotes acquired anlotinib resistance in oral squamous cell carcinoma

Tyrosine kinase inhibitors (TKIs) are frequently utilized in the management of malignant tumors. Studies have indicated that anlotinib has a significant inhibitory effect on oral squamous cell carcinoma (OSCC). However, the mechanisms underlying the development of resistance with long-term anlotinib treatment remain obscure. Our research found that METTL1 expression was heightened in anlotinib-resistant OSCC cells. We observed that METTL1 played a role in fostering resistance to anlotinib in both transgenic mouse models and in vitro. Mechanistically, the elevated METTL1 levels in anlotinib-resistant OSCC cells contributed to enhanced global mRNA translation and stimulated oxidative phosphorylation (OXPHOS) through m7G tRNA modification. Bioenergetic profiling demonstrated that METTL1 drived a metabolic shift from glycolysis to OXPHOS in anlotinib-resistant OSCC cells. Additionally, inhibition of OXPHOS biochemically negated METTL1′s impact on anlotinib resistance. Overall, this study underscores the pivotal role of METTL1-mediated m7G tRNA modification in anlotinib resistance and lays the groundwork for novel therapeutic interventions to counteract resistance in OSCC.

TR-57 Treatment of SUM159 Cells Induces Mitochondrial Dysfunction without Affecting Membrane Potential.

Recent works identified ClpXP, mitochondrial caseinolytic protease, as the only target of imipridones, a new class of antitumor agents. Our study of the mechanism of imipridone derivative TR-57 action in SUM159 human breast cancer cells demonstrated mitochondrial fragmentation, degradation of mitochondrial mtDNA and mitochondrial dysfunction due to inhibition of Complex I and Complex II activity. Complete inhibition of oxidative phosphorylation accompanied 90, 94, 88 and 87% decreases in the content of Complex I, II, III and IV proteins, respectively. The content of the FOF1-ATPase subunits decreased sharply by approximately 35% after 24 h and remained unchanged up to 72 h of incubation with TR-57. At the same time, a disappearance of the ATPIF1, the natural inhibitor of mitochondrial FOF1-ATPase, was observed after 24 h exposure to TR-57. ATPase inhibitor oligomycin did not affect the mitochondrial membrane potential in intact SUM159, whereas it caused a 65% decrease in TR-57-treated cells. SUM159 cells incubated with TR57 up to 72 h retained the level of proteins facilitating the ATP transfer across the mitochondrial membranes: VDAC1 expression was not affected, while expression of ANT-1/2 and APC2 increased by 20% and 40%, respectively. Thus, our results suggest that although TR-57 treatment leads to complete inhibition of respiratory chain activity of SUM159 cells, hydrolysis of cytoplasmic ATP by reversal activity of FOF1-ATPase supports mitochondrial polarization.

Abstract C049: Loss of RNF43 creates an OXPHOS dependency in early pancreatic neoplasia

Abstract Pancreatic ductal adenocarcinoma (PDAC) has a dismal 5-year survival of 12%. RNF43 is frequently mutated in pancreatic cystic neoplasms, including intraductal papillary mucinous neoplasms (IPMNs), which are precursor lesions of PDAC. RNF43 encodes for an E3 ubiquitin ligase and was initially identified as a negative Wnt regulator. To elucidate the role of RNF43-mutated neoplasms in an organ specific context, we have generated a genetically engineered mouse model which has pancreas specific loss of RNF43 (Hosein, Gastroenterology 2022). In this study we examine some of the metabolic dependencies created by Rnf43 loss on the background of mutant Kras, and how the Kras;Rnf43 model differs from the commonly used Kras;p53 model of PDAC. We have generated cell lines harboring mutant Kras and bi-allelic loss of Rnf43 from the resulting lesions in these mice (henceforth referred to as Kras;Rnf43 lines).Isogenic Kras;Rnf43 cell lines with re-expression of full-length Rnf43 (Kras;Rnf43-RNF43OE) were generated to confirm if observed phenotypes were Rnf43 dependent. Single-cell RNA sequencing (scRNA-seq) was performed for comparison between murine PDAC arising in Kras;Rnf43 versus Kras;p53 mice. We further compared metabolic parameters in Kras;Rnf43 and Kras;Rnf43-RNF43OE cells using the Seahorse platform. Mitochondrial ultrastructure by transmission electron microscopy (TEM) was analyzed in Kras;Rnf43 compared to Kras;p53 cells. To visualize endoplasmic reticulum (ER)-mitochondria contact sites (ERMCS), a split green fluorescent protein-based contact site sensor (SPLICS) was transfected and analyzed. Compared to Kras;p53 PDAC, Kras;Rnf43 tumors demonstrated upregulated mitochondrial transcripts and gene signatures of ER stress. Further, the ER stress response protein IRE1 was markedly elevated in Kras;Rnf43 cells versus Kras;p53 cells. The Kras;Rnf43 lines had enhanced mitochondrial oxidative phosphorylation (OXPHOS) activity and demonstrated evidence of enhanced mitochondrial quality control. ERMCS is a dynamic contact region between ER and mitochondria, which regulates biological processes including calcium homeostasis, ER stress and mitochondrial dynamics. The Kras;Rnf43 cells had significantly increased ERMCS compared to Kras;p53 cells. Finally, using IACS-010759, a small molecule inhibitor of OXPHOS, we demonstrate that Kras;Rnf43 cells had both increased in vitro sensitivity as well as in vivo susceptibility to tumor growth inhibition in orthotopic models, which translated into increased overall survival of mice. In conclusion, we provide evidence showing that bi-allelic loss of RNF43 is associated with increased ER stress and enhanced IRE1 dependent stress response. ER stress is mitigated via increased mitochondrial OXPHOS and ERMCS. Importantly, our results suggest that this creates a metabolic synthetic essentiality in the context of RNF43 loss, providing an avenue to suppress the progression of RNF43-mutated IPMNs, and potentially other solid cancers by targeting mitochondrial OXPHOS. Citation Format: Akiko Sagara, Brandon Chen, Nathaniel G. Yee, Megan J. Siemann, Costas A. Lyssiotis, Yatrik M. Shah, Sonja M. Woermann, Anirban Maitra. Loss of RNF43 creates an OXPHOS dependency in early pancreatic neoplasia [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C049.

Abstract B058: Mutant GNAS drives glycolytic dependency in intraductal papillary mucinous neoplasms of the pancreas

Abstract Oncogenic “hotspot” mutations of KRAS and GNAS are two major driver alterations in Intraductal Papillary Mucinous Neoplasms (IPMNs), which are bona fide precursor lesions of pancreatic ductal adenocarcinoma (PDAC). We previously reported that pancreas-specific KrasG12D and GnasR201C expression caused IPMN development, with subsequent progression to PDAC in p48-Cre; LSL-KrasG12D; Rosa26R-LSL-rtTA-TetO-GnasR201C mice (referred to as “Kras;Gnas” mice). This study aimed to clarify the functional roles of mutant GNAS, thereby investigating therapeutic dependencies that exist in the context of mutant KRAS and GNAS co-expression in IPMN. We established cell lines derived from IPMN-associated PDAC in Kras;Gnas mice (referred to as “Kras;Gnas” cells), in which KrasG12D is constitutively active whereas GnasR201C expression is inducible by the addition of doxycycline. RNA-sequencing of Kras;Gnas cells identified the enrichment of glycolysis-related gene signatures upon GnasR201C induction. This was also confirmed on single cell RNA sequencing data of IPMN-associated PDAC in Kras;Gnas mice, when compared with tumors arising in mice expressing mutant KrasG12D alone. Genome-wide CRISPR/Cas9 screening identified multiple glycolysis-related genes as essential genes in the setting of KrasG12D and GnasR201C co-expression in Kras;Gnas cells. Further, Seahorse metabolic flux analyzer showed the enhancement of glycolysis by GnasR201C induction in Kras;Gnas cells. In vivo, 13C-hyperpolarized MRI (HP-MRI) revealed the enhancement of glycolytic flux (pyruvate to lactate conversion) in Kras;Gnas mice with concurrent GnasR201C expression, compared to mice with KrasG12D alone. The GNASR201C-expressing Kras;Gnas cells were also more susceptible to glycolysis inhibition either by glucose deprivation or upon exposure to inhibitors of glycolysis, when compared to cells with only KrasG12D expression. Knockout of Gpi1 or Slc2a1, two synthetic lethal glycolysis associated genes identified on CRISPR/Cas9 screening, significantly suppressed cell growth in GNASR201C-expressing Kras;Gnas cells both in vitro and in vivo. Of note, Gpi1 deletion increased compensatory ATP production from mitochondrial oxidative phosphorylation (OXPHOS) and autophagy in GNASR201C-expressing Kras;Gnas cells and as a result, these cells were more susceptible to both inhibitors of OXPHOS and of autophagy. We identified two candidate effector pathways downstream of GNASR201C activation - PKA/PFKFB3 and EPAC/DRP1 – which were responsible for the increased glycolytic activity observed via multiple orthogonal approaches in Kras;Gnas cells. The expression of phospho-PFKFB3, Gpi1, and Glut1 proteins were elevated in human IPMN lesions with GNAS mutations. In conclusion, the co-occurrence of hot spot GNAS mutations enhances glycolysis in IPMNs arising in the context of KRAS mutations. Targeting glycolysis might be a potential avenue for treatment and cancer interception in IPMN lesions with co-mutations of KRAS and GNAS. Citation Format: Yuki Makino, Kimal Rajapakshe, Nathaniel Yee, Megan Siemann, Jimin Min, Benson Chellakkan Selvanesan, Fredrik Thege, Akiko Sagara, Prasanta Dutta, Pratip Bhattacharya, Merve Dede, Traver Hart, Anirban Maitra. Mutant GNAS drives glycolytic dependency in intraductal papillary mucinous neoplasms of the pancreas [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B058.

An Open-Label Phase I Study of Metformin and Nelfinavir in Combination With Bortezomib in Patients With Relapsed and Refractory Multiple Myeloma

BackgroundIn preclinical models, combining a GLUT4 inhibitor with an oxidative phosphorylation inhibitor shows synergistic therapeutic potential against multiple myeloma (MM). Thus, this study evaluated the safety and tolerability of repurposing metformin, a complex I inhibitor, and nelfinavir, a GLUT4 inhibitor, in combination with bortezomib for the treatment of relapsed/refractory MM that had progressed on all standard of care therapies. Materials and MethodsThis trial utilized a 3 + 3 dose escalation design with 3 dose levels planned for up to a maximum of 6 (21-day) cycles. Metformin and nelfinavir were administered for 14 of 21 days, and subQ bortezomib was administered to a portion of patients on days 1, 8, and 15. The primary objective was to determine the maximal tolerated dose, and the secondary objective was to evaluate the safety and overall response rate (ORR) of this combination. ResultsNine patients were accrued with a median age of 65 (range: 42-81) and received a median of 7 prior lines of therapy (Range: 5-12). The first 3 patients received only metformin (500 mg BID) and nelfinavir (1250 mg BID) at the first dose level, with 1 patient experiencing an unconfirmed minimal response (MR) in the first cycle, 1 experiencing progressive disease after 1 cycle of treatment and 1 patient going off treatment prior to assessing response but with signs of progressive disease. Given the limited therapeutic activity, the upfront addition of bortezomib (1.3 mg/m2) was utilized for the subsequent 6 patients accrued. Three of these 6 patients went off study due to progressive disease, 1 patient achieved an unconfirmed partial response after 1 cycle of treatment but reported progressive disease in the subsequent cycle, 1 patient went off study to enter hospice, and the remaining patient experienced stable disease (SD) after receiving 6 cycles of clinical trial treatment. The study was closed before accrual to the next dose level was started. ConclusionThis is the first study to evaluate the safety and efficacy of this repurposed drug combination in this very difficult-to-treat population of relapsed and refractory MM. This was an overall negative study with no ORR observed. Fortunately, 1 patient experienced an SD response, allowing this combination to stabilize their disease until another novel therapy on a clinical trial was available.

Nitazoxanide in the Treatment of COVID-19: A paradigm for Antiviral Drugs Targeting Host-Infected Cells

Despite significant breakthroughs in the discovery of direct-acting antivirals for several viruses, there is a need for improvement. Thus, drugs able to target host-infected cells may prove valuable in enhancing the efficacy of antivirals and avoiding resistance due to viral genetic changes. In this context, we summarize in this review the current knowledge on nitazoxanide's potential for treating COVID-19. Our review highlights nitazoxanide's very specific mode of action, targeting cellular energy through inhibiting mitochondrial oxidative phosphorylation (OXPHOS) and stimulating the innate immune response. Thus, nitazoxanide lowers the cellular ATP content and this leads to impaired viral replication and assembly. However, since nitazoxanide only yields a mild OXPHOS inhibition, this does not affect cell viability. Preclinical results and some clinical studies have suggested that nitazoxanide might be helpful for treating COVID-19. Indeed, some clinical studies have shown a decrease in severe COVID19 evolution as well as in viral multiplication; yet the results are still debated. Overall, the available information suggests the potential of nitazoxanide in association with direct-acting antivirals. In fact, this may hold true for other viruses than SARS-CoV-2 in the future. The impact of nitazoxanide on COVID-19 should be viewed as a paradigm for antiviral drugs targeting host-infected cells, and nitazoxanide should be part of the therapeutic tools for future emerging virus-related pandemics.

A gold-based inhibitor of oxidative phosphorylation is effective against triple negative breast cancer

Triple-negative breast cancer (TNBC) is associated with metabolic heterogeneity and poor prognosis with limited treatment options. New treatment paradigms for TNBC remains an unmet need. Thus, therapeutics that target metabolism are particularly attractive approaches. We previously designed organometallic Au(III) compounds capable of modulating mitochondrial respiration by ligand tuning with high anticancer potency in vitro and in vivo. Here, we show that an efficacious Au(III) dithiocarbamate (AuDTC) compound induce mitochondrial dysfunction and oxidative damage in cancer cells. Efficacy of AuDTC in TNBC mouse models harboring mitochondrial oxidative phosphorylation (OXPHOS) dependence and metabolic heterogeneity establishes its therapeutic potential following systemic delivery. This provides evidence that AuDTC is an effective modulator of mitochondrial respiration worthy of clinical development in the context of TNBC. One sentence summaryMetabolic-targeting of triple-negative breast cancer by gold anticancer agent may provide efficacious therapy.

IDH1-mutant preleukemic hematopoietic stem cells can be eliminated by inhibition of oxidative phosphorylation.

Rare preleukemic hematopoietic stem cells (pHSCs) harboring only the initiating mutations can be detected at the time of AML diagnosis. pHSCs are the origin of leukemia and a potential reservoir for relapse. Using primary human samples and gene-editing to model isocitrate dehydrogenase 1 (IDH1) mutant pHSCs, we show epigenetic, transcriptional, and metabolic differences between pHSCs and healthy hematopoietic stem cells (HSCs). We confirm that IDH1 driven clonal hematopoiesis is associated with cytopenia, suggesting an inherent defect to fully reconstitute hematopoiesis. Despite giving rise to multilineage engraftment, IDH1-mutant pHSCs exhibited reduced proliferation, blocked differentiation, downregulation of MHC Class II genes, and reprogramming of oxidative phosphorylation metabolism. Critically, inhibition of oxidative phosphorylation resulted in complete eradication of IDH1-mutant pHSCs but not IDH2-mutant pHSCs or wildtype HSCs. Our results indicate that IDH1-mutant preleukemic clones can be targeted with complex I inhibitors, offering a potential strategy to prevent development and relapse of leukemia.

Simultaneous Modulation of Hypoxia And Metabolism in Glioblastoma for Enhanced Radio‐Immunotherapy

AbstractGlioblastoma (GBM) is the most invasive and lethal primary brain melanoma. The existing treatment modality is unable to achieve thorough elimination of GBM due to the aggressive nature, blood‐brain barrier (BBB), hypoxic environment, and heterogeneous cellular components. Herein, a radio‐immunotherapy regimen based on a versatile nanoplatform (G/APH‐M) is proposed to effectively kill quiescent cancer stem cells (CSCs) and proliferative cancer cells in GBM in a simultaneous manner. Among o ur prepared G/APH‐M, the coating of GL261 cell membrane guarantees the BBB‐penetrable delivery and homologous GBM‐targeting of the hollow Prussian blue loaded with oxidative phosphorylation inhibitor Gboxin and catalase‐mimetic nanozymes. After substantial tumor accumulation, the released Gboxin inhibits mitochondrial oxidative phosphorylation to kill CSCs, while the nanozymes catalyze the production of oxygen to enhance radiotherapy. Consequently, potent immunogenic cell death (ICD) of GBM is induced, which in combination with immune checkpoint inhibitors (αPD‐L1), achieving a potent therapeutic effect with an 80% survival rate in the orthotopic GBM model even at 60 days after the treatment. The synergistic modulation of hypoxia and metabolism based on G/APH‐M greatly intensifies the radio‐immunotherapy of GBM, which would inspire more comprehensive strategies targeting the multiple characteristics of GBM cells for clinical benefits.

Enhancing anti-AML activity of venetoclax by isoflavone ME-344 through suppression of OXPHOS and/or purine biosynthesis in vitro

Venetoclax (VEN), in combination with low dose cytarabine (AraC) or a hypomethylating agent, is FDA approved to treat acute myeloid leukemia (AML) in patients who are over the age of 75 or cannot tolerate standard chemotherapy. Despite high response rates to these therapies, most patients succumb to the disease due to relapse and/or drug resistance, providing an unmet clinical need for novel therapies to improve AML patient survival. ME-344 is a potent isoflavone with demonstrated inhibitory activity toward oxidative phosphorylation (OXPHOS) and clinical activity in solid tumors. Given that OXPHOS inhibition enhances VEN antileukemic activity against AML, we hypothesized that ME-344 could enhance the anti-AML activity of VEN. Here we report that ME-344 enhanced VEN to target AML cell lines and primary patient samples while sparing normal hematopoietic cells. Cooperative suppression of OXPHOS was detected in a subset of AML cell lines and primary patient samples. Metabolomics analysis revealed a significant reduction of purine biosynthesis metabolites by ME-344. Further, lometrexol, a purine biosynthesis inhibitor, synergistically enhanced VEN-induced apoptosis in AML cell lines. Interestingly, AML cells with acquired AraC resistance showed significantly increased purine biosynthesis metabolites and sensitivities to ME-344. Furthermore, synergy between ME-344 and VEN was preserved in these AraC-resistant AML cells. In vivo studies revealed significantly prolonged survival upon combination therapy of ME-344 and VEN in NSGS mice bearing parental or AraC-resistant MV4-11 leukemia compared to the vehicle control. This study demonstrates that ME-344 enhances VEN antileukemic activity against preclinical models of AML by suppressing OXPHOS and/or purine biosynthesis.

AMP-activated protein kinase (AMPK) suppresses Ibaraki virus propagation

The Ibaraki virus (IBAV) causes Ibaraki disease in cattle. Our previous studies have shown that IBAV uses macropinocytosis to enter the host cell and exit from the endosome to the cytosol in response to endosomal acidification. To further explore the mechanism of IBAV infection and replication, we examined the effect of inhibitors of mitochondrial oxidative phosphorylation, carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and antimycin A, on IBAV propagation. These inhibitors significantly suppressed IBAV propagation, with reduced cellular ATP levels resulting from suppression of ATP synthesis. Furthermore, we identified AMP-activated protein kinase (AMPK), which is activated by CCCP or antimycin A, as a key signaling molecule in IBAV suppression. We also observed that IBAV infection induces ATP depletion and increases AMPK activity. Our findings suggest that AMPK is a potential target in Ibaraki disease.

Cryptotanshinone suppresses ovarian cancer via simultaneous inhibition of glycolysis and oxidative phosphorylation

Ovarian cancer is one of the most lethal cancers in female reproductive system due to heterogeneity and lack of effective treatment. Targeting aerobic glycolysis, a predominant energy metabolism of cancer cells has been recognized a novel strategy to overcome cancer cell growth. However, the capability of cancer cells to undergo metabolic reprogramming guarantees their survival even when glycolysis is inhibited. Here in this study, we have shown that Cryptotanshinone (CT), a lipid-soluble bioactive anticancer molecule of Salvia miltiorrhiza, inhibits both glycolysis and oxidative phosphorylation (OXPHOS) in ovarian cancer cells leading to growth suppression and apoptosis induction. Our mechanistic study revealed that CT decreased glucose uptake and lactate production, and inhibited the kinase activity of LDHA and HK2. The molecular docking study showed that CT could directly bind with GLUT1, LDHA, HK2, PKM2 and complex-1. The immunoblotting data showed that CT decreased the expression of aberrantly activated glycolytic proteins includingGLUT1, LDHA, HK2, and PKM2. Besides, we found that CT inhibited mitochondrial ComplexⅠ activity, decreased the ratio of NAD+/NADH, and suppressed the generation of ATP and induced activation of AMPK, which controls energy-reducing processes. These in vitro findings were further validated using xenograft model. The findings of in vivo studies were in line with in vitro studies. Taken together, CT effectively suppressed glycolysis and OXPHOS, inhibited growth and induced apoptosis in ovarian cancer cells both in vitro and in vivo study models.

Intracellular Iron Controls HSC Metabolism By Affecting Mitochondrial Fitness

Iron is an important source of reactive oxygen species (ROS) within the cell and recent evidence highlighted its role in regulating HSC self-renewal and differentiation. However, whether and how iron influences HSC metabolism is still undetermined. Cellular metabolism is a key regulator of HSC maintenance and HSCs adapt their metabolic state to their function. Quiescent HSCs have low energy requirements and depend on anaerobic glycolysis, whereas active HSCs require high energy for proliferation and differentiation thus enhancing oxidative phosphorylation (OXPHOS), glycolysis and fatty acid oxidation (FAO). To explore which metabolic pathways are triggered by intracellular iron levels, we took advantage of the thalassemic Hbb th3/+mice ( th3), characterized by chronic iron overload (IO). We previously demonstrated an impaired function of th3 HSCs due to persistence into altered BM niche ( Aprile et al., 2020). Th3 HSCs showed higher levels of intracellular free reactive iron (1.7±0.2 calcein MFI fold to wt, p<0.0001) and interestingly iron specifically accumulated in the mitochondria. As a result, mitochondria are impaired, with low mass and activity, as assessed by decreased mitochondrial membrane potential ( th3 1068±167 vs. wt 3215±686 MFI TMRE, p<0.05). These data, together with a reduced expression of mitochondrial biogenesis and mitophagy genes, indicate an accumulation of damaged mitochondria. To demonstrate a direct effect of iron on mitochondrial fitness in HSCs, we treated wt mice with iron dextran. Consistently, IO wt HSCs showed reduced mitochondrial activity following intracellular iron accumulation. Since mitochondria are the major site of cellular ATP production mostly through OXPHOS, we measured the metabolic state of HSCs in ß-thalassemia. ATP levels in sorted th3 HSCs was halved than the one in wt mice ( th3 3.7±0.3 vs. wt 9.8±2.6 ATP nM, p<0.01). Inhibition of OXPHOS by oligomycin lowered the ATP content in wt cells with a minor effect in th3 HSCs, thus indicating a reduced OXPHOS-dependent metabolism, despite their active cycling profile. Since mitochondria are damaged and OXPHOS and glycolysis are the two main metabolic pathways involved in cellular ATP generation, we hypothesized increased glycolytic dependency to compensate for reduced OXPHOS in th3 HSCs. Indeed, in these cells we observed a positive enrichment of glycolytic genes, such as Tpi1, Gapdh and Pklr, and a 1.4-fold higher glucose uptake ( th3 2401±85 vs. wt 1639±163 MFI 2NBDG, p<0.05). In vivo administration of the iron chelator DFO normalized intracellular iron content and rescued mitochondrial dysfunction in th3 mice, indicating the reversibility of mitochondrial defects. Moreover, HSCs from DFO-treated mice showed reduced glucose uptake, thus demonstrating that IO causes mitochondrial defects and metabolic adaptations of HSCs. Excess iron is expected to give rise to ROS and, consistently, th3 HSCs displayed high mitochondrial ROS (mtROS) levels ( th3 5205±459 vs. wt 2507±756 MFI MitoSOX, p<0.01). I n vivo reduction of mtROS by MitoQ administration restored mitochondrial activity and decreased glucose uptake. Remarkably, MitoQ rescued the quiescence and self-renewal ability of th3 HSCs, as shown by superior chimerism in secondary transplantation of HSCs from MitoQ-treated th3 donors in lethally irradiated recipients ( th3 HSC+MitoQ 81.7±1.6 vs. untreated th3 HSC 34.9±14.6 vs. % of chimerism, p<0.05), thus indicating that IO-derived ROS impair HSC function by affecting mitochondrial fitness and bioenergetics. Preliminary results confirmed intracellular IO and mitochondrial defects also in HSCs from Townes mice, a model of sickle cell anemia characterized by IO. Collectively, our study revealed that increased intracellular iron and ROS levels alter HSC metabolic programs by inducing mitochondrial dysfunction. Since mitochondria are defective, IO HSCs are unable to produce appropriate levels of ATP through OXPHOS and rely on glycolysis, despite their active cycling activity. Finally, the rescue of mitochondrial activity can restore the functional defects of th3 HSCs.

Targeting Sumoylation Sensitizes Acute Myeloid Leukemia to Venetoclax Treatment

Acute myeloid leukemia (AML) is a hematopoietic cancer characterized by aberrant immature myeloid progenitor blasts in bone marrow and peripheral blood. Venetoclax (VEN), a BCL-2 inhibitor, is FDA-approved for AML treatment with hypomethylating agents (HMA). Despite the improvement of VEN and HMA, not all patients respond, and most patients develop resistance. This presents an urgent need for new therapies to overcome VEN resistance and enhance VEN efficacy. We propose SUMOylation inhibition as a novel therapy to address this need. SUMOylation regulates protein function by covalently attaching Small Ubiquitin-like MOdifier (SUMO) proteins to target proteins. SUMOylation plays an important role in tumor progression and immune response. Our study aims to evaluate the effects of SUMOylation inhibition on anti-AML activity of VEN and the mechanism. We firstly generated VEN-resistant cell lines Molm13-VR and MV411-VR by culturing Molm13 and MV4-11 cells in increasing doses of VEN. SUMO E1 (SAE2) and global SUMOylation levels were remarkably upregulated in VEN-resistant cell lines, suggesting SUMOylation plays a role in VEN resistance. We evaluated the antileukemic effects of TAK-981 (subasumstat), a novel and specific SUMO E1 inhibitor, alone and in combination with VEN, using AML cell lines and primary blasts isolated from refractory/relapsed (R/R) AML patients. Different AML cell lines and blast samples showed various sensitivities to VEN (IC 50 10nM ~ 5,000nM), but significant synergism was observed with TAK-981 and VEN in cell viability assay. TAK-981 synergized with VEN at inducing AML cell apoptosis determined by annexin-V staining with flow cytometry as well as increased levels of cleaved-PARP and cleaved caspase-3 by western blotting. The mechanism of action of VEN is dependent on BCL-2 mediated mitochondrial function and metabolism. We assessed mitochondrial membrane potential using TMRM probe. TAK-981 reduced mitochondrial membrane potential in both VEN-sensitive and resistant AML lines, further in combination with VEN. Because mitochondrial membrane potential is maintained by normal mitochondrial structure, we performed electron microscopy to determine mitochondrial structure. VEN had limited effect on mitochondria in resistant cells. However, TAK-981 induced abnormal ultrastructure mitochondria with fewer cristae, worsened by TAK-981+VEN combination. Since TAK-981 treatment caused mitochondrial structure defects, we determine the mitochondrial function using Seahorse XF assay. VEN decreased oxygen consumption rate (OCR), indicating inhibition of oxidative phosphorylation (OXPHOS), further suppressed by TAK-981. Metabolomic profiling by mass spectrometry indicated TAK-981+VEN treated AML cells displayed striking decreases in TCA cycle intermediates and reduced electron transport chain (ETC) activity. Pathway analysis of the metabolomics data revealed significant enrichment in amino acids metabolism. Notably, RNA-sequencing and GSEA analysis showed consistent findings that TAK-981+VEN showed suppressed signaling pathways in mitochondrial function, glycolysis and amino-acid metabolisms, indicating TAK-981 targeted mitochondrial metabolism to enhance VEN activity. We then determined whether TAK-981 enhanced antileukemic effect of VEN ex vivo and in vivo. TAK-981 synergized with VEN at reducing colony formation capacity in colony formation assay using leukemia stem cells (LSCs) isolated from relapse AML blasts. More importantly, TAK-981 showed remarkable therapeutic effect in patient-derived xenograft (PDX) mouse model engrafted with blasts isolated from R/R AML patients, and significantly synergized with VEN at extending mice survival in vivo. In conclusion, TAK-981 enhances the antileukemic activity of VEN by targeting mitochondria function and metabolism, offering a potent therapy for refractory/relapsed AML.

Minimal Residual Disease in Acute Myeloid Leukemia Following Induction Chemotherapy Can be Effectively Eradicated By Targeting Mitochondrial Metabolism

Acute myeloid leukemia (AML) stem cells (AMLSCs) AMLSCs and residual cytarabine (AraC)-resistant AML cells (constituting minimal residual disease, MRD) thought to be responsible for chemoresistance and treatment failure, were shown to be highly dependent on mitochondrial function for survival and thus are vulnerable to pharmacological blockade of the oxidative phosphorylation (OXPHOS) (Farge et al. Cancer Discov, 2017). Efficacy of OXPHOS inhibitor IACS-010759 (OXPHOS-i) was previously reported, demonstrating potent inhibition of mitochondrial complex I, OXPHOS suppression and growth inhibition of AML cells (Molina, et al. Nat Med, 2018). Here we evaluated OXPHOS dependency of AML MRD cells and determined impact of OXPHOS blockade on residual AML cells surviving standard chemotherapy (Doxorubicin/AraC, DA). Our results demonstrated that AML cell lines treated with AraC or DA induced accumulation of reactive oxygen species, mitochondrial superoxides, increased mitochondrial mass and mitochondrial membrane potential. AraC- and DA therapies in vitro were significantly enhanced by OXPHOS-i. OXPHOS dependency shown as a significantly increased basal and maximal oxygen consumption rate after AraC and DA treatment, was fully inhibited by OXPHOS-i, leading to complete mitochondrial collapse. OXPHOS inhibition in combination with DA translated into reduction of viable cell numbers, induction of apoptosis and differentiation in AraC-sensitive and AraC-resistant cell lines models. In vitro efficacy was also observed in engineered p53-mutated MOLM13 model, indicating that combination of OXPHOS-i and DA might successfully overcome p53 mutation-driven chemoresistance. These effects were further validated in a subset of AraC-resistant primary patient samples. Mechanistically, induction of ROS caused by OXPHOS-i addition upon DA contributed to differentiation and cell death, and was partially reversed by ROS scavengers. Next, the efficacy of IACS-010759 together with DA chemotherapy was evaluated in several chemotherapy-sensitive and -resistant animal models in vivo. DA/IACS-010759 combination significantly reduced leukemia burden and extended survival in OCI-AML3/Luc/GFP model and in FLT3-ITD + AML PDX model. In the latter, IACS-010759 led to the reduction of leukemia burden and delayed leukemia recurrence when administered post completion of DA. At the single-cell level, CyTOF analysis demonstrated that this combination reduced frequency of CD34 +CD38 lowCD123 +AML LSCs and facilitated differentiation of immature subpopulations (Fig.1A). Furthermore, addition of OXPHOS-i to DA extended survival of mice inoculated with chemoresistant PDX AML models. Finally, OXPHOS-i administered during consolidation phase significantly extended mice survival compared to standard of care arm, supporting clinical utility of OXPHOS inhibitors in AML (Fig.1B). In conclusion, our findings indicate that chemotherapy fosters mitochondrial respiration in AML, which could be abrogated by OXPHOS inhibitor at the LSCs and MRD level , in vitro and in vivo. While IACS-010759 (Yap et al. Nat Med 2023) showed toxicities impeding its clinical utility, our data advocate for combining mitochondrial targeting strategies with chemotherapy as a part of induction and consolidation treatment for improved control of MRD, eradication of AMLSC and extended response duration. Thus, further studies to identify compounds with improved safety profile are warranted.

Chronic lymphocytic leukemia patient-derived xenografts recapitulate clonal evolution to Richter transformation

Chronic lymphocytic leukemia (CLL) is a B-cell neoplasm with a heterogeneous clinical behavior. In 5–10% of patients the disease transforms into a diffuse large-B cell lymphoma known as Richter transformation (RT), which is associated with dismal prognosis. Here, we aimed to establish patient-derived xenograft (PDX) models to study the molecular features and evolution of CLL and RT. We generated two PDXs by injecting CLL (PDX12) and RT (PDX19) cells into immunocompromised NSG mice. Both PDXs were morphologically and phenotypically similar to RT. Whole-genome sequencing analysis at different time points of the PDX evolution revealed a genomic landscape similar to RT tumors from both patients and uncovered an unprecedented RT subclonal heterogeneity and clonal evolution during PDX generation. In PDX12, the transformed cells expanded from a very small subclone already present at the CLL stage. Transcriptomic analysis of PDXs showed a high oxidative phosphorylation (OXPHOS) and low B-cell receptor (BCR) signaling similar to the RT in the patients. IACS-010759, an OXPHOS inhibitor, reduced proliferation, and circumvented resistance to venetoclax. In summary, we have generated new RT-PDX models, one of them from CLL cells that mimicked the evolution of CLL to RT uncovering intrinsic features of RT cells of therapeutical value.

Biomarker Driven Strategies for Targeted Elimination of Hypoxia Adapted Lymphoma Cells

Large body of evidence suggests that hypoxia drives aggressive molecular features irrespective of cancer type. Non-Hodgkin lymphomas (NHL) are the most common hematologic malignancies characterized by widespread disease and frequent involvement of diverse hypoxic microenvironments (e.g., bone marrow, malignant effusions, large lymphoma masses). Impact of long-term hypoxia on the biology of lymphoma cells and its potential role in mediating drug resistance and disease relapses due to adaptive changes shaped by the hypoxic microenvironment remain only partially understood. In this study we analyzed impact of short- and long-term hypoxia on a panel of six lymphoma cell lines including diffuse large B-cell lymphoma (UPF4D, UPF8D), Burkitt lymphoma (Ramos, UPF9T), and mantle cell lymphoma (HBL2, MINO). Only 2 out of 8 tested lymphoma cell lines (Ramos, and HBL2) survived longer than 4 weeks under deep hypoxia (1% O2). The remaining tested lymphoma cell lines died by hypoxia-induced apoptosis (which could be inhibited by co-cultivation with pan-caspase inhibitor Z-VAD-FMK). The hypoxia-adapted (HA) Ramos and HBL2 cells had severely decreased proliferation rate accompanied by complex changes of the transcriptome, proteome, and metabolome. Seahorse analysis revealed significant inhibition of both oxidative phosphorylation and glycolytic pathways ( Figure 1). Of note, the whole-proteome profiling confirmed significant downregulation of proteins regulating oxidative phosphorylation, but significant upregulation of proteins regulating glycolysis. Sensitivity of HA cells to 2-deoxyglucose, an inhibitor of glycolysis was markedly increased ( Figure 1). The data suggest that under long-term deep hypoxia, lymphoma cells try to compensate for the decrease in ATP production from the oxidative phosphorylation process by boosting structural machinery of glycolysis, on which they became vitally dependent for survival. Despite the increased glycolytic machinary, however, the level of glycolysis decreases due to severe lack of oxygen. In our opinion, this is a clear representation of the Warburg effect, a hallmark of cancer based on the metabolic reprogramming of the cancer cells under hypoxia. Sensitivity of HA cells to a panel of the tested cytotoxic drugs (cytarabin, cisplatin, bortezomib) and targeted agents (venetoclax, S63545, A1155463, TRAIL, polatuzumab vedotin, IM-156, copanlisib) was either unchanged or increased (compared to sensitivity of the original cell lines cultured under normoxia). In contrast to so far published data, long-term hypoxia was not associated with acquired drug resistance in case of any of the tested agent. Of note, HA cells became significantly more sensitive to A1155463, an inhibitor of anti-apoptotic protein BCL-XL ( Figure 1). Unchanged levels of BCL-XL protein in HA cells and the respective normoxic cell lines (detected by western blotting) suggest that more complex mechanisms plausibly underlie the observed markedly increased sensitivity to A1155463. The whole-transcriptome and proteome analyses of both HA cell lines (compared to the parental cell lines cultured under normoxic conditions) detected among other complex changes signficant upregulation of P4HA1 (both mRNA, and protein), a prolyl hydroxylase involved in the stabilization of hypoxia-induced factor (HIF) 1 alpha, and putative oncogene associated with tumor aggressiveness. Transgenic (over)expression of P4HA1 in hypoxia-sensitive MINO cells effectively inhibited the hypoxia-induced apoptosis. Western blot analysis implemented on a panel of primary lymphoma cells revealed markedly higher expression of P4HA1 protein in the lymphoma cells obtained from malignant effusions (putative hypoxic microenvironment) compared to lymphoma cells obtained from leukemized blood (putative normoxic microenvironment). Our data suggest that P4HA1 positively impacts survival of lymphoma cells under hypoxia. In translation, P4HA1, BCL-XL, and structural proteins of the glycolytic pathway may represent novel drugable targets for more effective elimination of hypoxia-adapted lymphoma cells. Financial Support: Ministry of Health of the Czech Republic AZV NU23-03-00172, Grant Agency of the Czech Republic GA23-05377S, and National Institute for Cancer Research (EXCELES) LX22NPO5102.

Tachycardia-induced metabolic rewiring as a driver of contractile dysfunction.

Prolonged tachycardia-a risk factor for cardiovascular morbidity and mortality-can induce cardiomyopathy in the absence of structural disease in the heart. Here, by leveraging human patient data, a canine model of tachycardia and engineered heart tissue generated from human induced pluripotent stem cells, we show that metabolic rewiring during tachycardia drives contractile dysfunction by promoting tissue hypoxia, elevated glucose utilization and the suppression of oxidative phosphorylation. Mechanistically, a metabolic shift towards anaerobic glycolysis disrupts the redox balance of nicotinamide adenine dinucleotide (NAD), resulting in increased global protein acetylation (and in particular the acetylation of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase), a molecular signature of heart failure. Restoration of NAD redox by NAD+ supplementation reduced sarcoplasmic/endoplasmic reticulum Ca2+-ATPase acetylation and accelerated the functional recovery of the engineered heart tissue after tachycardia. Understanding how metabolic rewiring drives tachycardia-induced cardiomyopathy opens up opportunities for therapeutic intervention.

Mitochondrial Calcium Waves by Electrical Stimulation in Cultured Hippocampal Neurons.

Mitochondria are critical to cellular Ca2+ homeostasis via the sequestering of cytosolic Ca2+ in the mitochondrial matrix. Mitochondrial Ca2+ buffering regulates neuronal activity and neuronal death by shaping cytosolic and presynaptic Ca2+ or controlling energy metabolism. Dysfunction in mitochondrial Ca2+ buffering has been implicated in psychological and neurological disorders. Ca2+ wave propagation refers to the spreading of Ca2+ for buffering and maintaining the associated rise in Ca2+ concentration. We investigated mitochondrial Ca2+ waves in hippocampal neurons using genetically encoded Ca2+ indicators. Neurons transfected with mito-GCaMP5G, mito-RCaMP1h, and CEPIA3mt exhibited evidence of mitochondrial Ca2+ waves with electrical stimulation. These waves were observed with 200 action potentials at 40Hz or 20Hz but not with lower frequencies or fewer action potentials. The application of inhibitors of mitochondrial calcium uniporter and oxidative phosphorylation suppressed mitochondrial Ca2+ waves. However, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and N-methyl-d-aspartate receptor blockade had no effect on mitochondrial Ca2+ wave were propagation. The Ca2+ waves were not observed in endoplasmic reticula, presynaptic terminals, or cytosol in association with electrical stimulation of 200 action potentials at 40Hz. These results offer novel insights into the mechanisms underlying mitochondrial Ca2+ buffering and the molecular basis of mitochondrial Ca2+ waves in neurons in response to electrical stimulation.