Targeting mitochondria metabolism for cancer therapy

Cancer cell specific inhibition of Wnt/β-catenin signaling by forced intracellular acidification

Use of the diabetes type II drug Metformin is associated with a moderately lowered risk of cancer incidence in numerous tumor entities. Studying the molecular changes associated with the tumor-suppressive action of Metformin we found that the oncogene SOX4, which is upregulated in solid tumors and associated with poor prognosis, was induced by Wnt/β-catenin signaling and blocked by Metformin. Wnt signaling inhibition by Metformin was surprisingly specific for cancer cells. Unraveling the underlying specificity, we identified Metformin and other Mitochondrial Complex I (MCI) inhibitors as inducers of intracellular acidification in cancer cells. We demonstrated that acidification triggers the unfolded protein response to induce the global transcriptional repressor DDIT3, known to block Wnt signaling. Moreover, our results suggest that intracellular acidification universally inhibits Wnt signaling. Based on these findings, we combined MCI inhibitors with H⁺ ionophores, to escalate cancer cells into intracellular hyper-acidification and ATP depletion. This treatment lowered intracellular pH both in vitro and in a mouse xenograft tumor model, depleted cellular ATP, blocked Wnt signaling, downregulated SOX4, and strongly decreased stemness and viability of cancer cells. Importantly, the inhibition of Wnt signaling occurred downstream of β-catenin, encouraging applications in treatment of cancers caused by APC and β-catenin mutations.

Machine Learning Helps Identify New Drug Mechanisms in Triple-Negative Breast Cancer

This paper demonstrates the ability of mach- ine learning approaches to identify a few genes among the 23,398 genes of the human genome to experiment on in the laboratory to establish new drug mechanisms. As a case study, this paper uses MDA-MB-231 breast cancer single-cells treated with the antidiabetic drug metformin. We show that mixture-model-based unsupervised methods with validation from hierarchical clustering can identify single-cell subpopulations (clusters). These clusters are characterized by a small set of genes (1% of the genome) that have significant differential expression across the clusters and are also highly correlated with pathways with anticancer effects driven by metformin. Among the identified small set of genes associated with reduced breast cancer incidence, laboratory experiments on one of the genes, CDC42, showed that its downregulation by metformin inhibited cancer cell migration and proliferation, thus validating the ability of machine learning approaches to identify biologically relevant candidates for laboratory experiments. Given the large size of the human genome and limitations in cost and skilled resources, the broader impact of this work in identifying a small set of differentially expressed genes after drug treatment lies in augmenting the drug-disease knowledge of pharmacogenomics experts in laboratory investigations, which could help establish novel biological mechanisms associated with drug response in diseases beyond breast cancer.

Aspartate is a limiting metabolite for cancer cell proliferation under hypoxia and in tumours

As oxygen is essential for many metabolic pathways, tumour hypoxia may impair cancer cell proliferation1-4. However, the limiting metabolites for proliferation under hypoxia and in tumours are unknown. Here, we assessed proliferation of a collection of cancer cells following inhibition of the mitochondrial electron transport chain (ETC), a major metabolic pathway requiring molecular oxygen5. Sensitivity to ETC inhibition varied across cell lines, and subsequent metabolomic analysis uncovered aspartate availability as a major determinant of sensitivity. Cell lines least sensitive to ETC inhibition maintain aspartate levels by importing it through an aspartate/glutamate transporter, SLC1A3. Genetic or pharmacologic modulation of SLC1A3 activity markedly altered cancer cell sensitivity to ETC inhibitors. Interestingly, aspartate levels also decrease under low oxygen, and increasing aspartate import by SLC1A3 provides a competitive advantage to cancer cells at low oxygen levels and in tumour xenografts. Finally, aspartate levels in primary human tumours negatively correlate with the expression of hypoxia markers, suggesting that tumour hypoxia is sufficient to inhibit ETC and, consequently, aspartate synthesis in vivo. Therefore, aspartate may be a limiting metabolite for tumour growth, and aspartate availability could be targeted for cancer therapy.

The multifaceted contributions of mitochondria to cellular metabolism

Although classically appreciated for their role as the powerhouse of the cell, the metabolic functions of mitochondria reach far beyond bioenergetics. In this Review, we discuss how mitochondria catabolize nutrients for energy, generate biosynthetic precursors for macromolecules, compartmentalize metabolites for the maintenance of redox homeostasis and function as hubs for metabolic waste management. We address the importance of these roles in both normal physiology and in disease.

Caffeic Acid Targets AMPK Signaling and Regulates Tricarboxylic Acid Cycle Anaplerosis while Metformin Downregulates HIF-1α-Induced Glycolytic Enzymes in Human Cervical Squamous Cell Carcinoma Lines

The small molecules, natural antioxidant Caffeic Acid (trans-3,4-Dihydroxycinnamic acid CA) and anti-diabetic drug Metformin (Met), activate 5′-adenosine monophosphate-activated protein kinase (AMPK) and interfere with metabolic reprogramming in human cervical squamous carcinoma cells. Here, to gain more insight into the ability of CA, Met and the combination of both compounds to impair aerobic glycolysis (the “Warburg effect”) and disrupt bioenergetics of cancer cells, we employed the cervical tumor cell lines C-4I and HTB-35/SiHa. In epithelial C-4I cells derived from solid tumors, CA alleviated glutamine anaplerosis by downregulation of Glutaminase (GLS) and Malic Enzyme 1 (ME1), which resulted in the reduction of NADPH levels. CA treatment of the cells altered tricarboxylic acid (TCA) cycle supplementation with pyruvate via Pyruvate Dehydrogenase Complex (PDH), increased ROS formation and enhanced cell death. Additionally, CA and CA/Met evoked intracellular energetic stress, which was followed by activation of AMPK and the impairment of unsaturated FA de novo synthesis. In invasive HTB-35 cells, Met inhibited Hypoxia-inducible Factor 1 (HIF-1α) and suppressed the expression of the proteins involved in the “Warburg effect”, such as glucose transporters (GLUT1, GLUT3) and regulatory enzymes of glycolytic pathway Hexokinase 2 (HK2), 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 4 (PFKFB4), Pyruvate Kinase (PKM) and Lactate Dehydrogenase A (LDH). Met suppressed the expression of c-Myc, BAX and cyclin-D1 (CCND1) and evoked apoptosis in HTB-35 cells. In conclusion, both small molecules CA and Met are capable of disrupting energy homeostasis, regulating oxidative metabolism/glycolysis in cervical tumor cells in regard to specific metabolic phenotype of the cells. CA and Met may provide a promising approach in the prevention of cervical cancer progression.

A precision therapeutic strategy for hexokinase 1-null, hexokinase 2-positive cancers

Background

Precision medicine therapies require identification of unique molecular cancer characteristics. Hexokinase (HK) activity has been proposed as a therapeutic target; however, different hexokinase isoforms have not been well characterized as alternative targets. While HK2 is highly expressed in the majority of cancers, cancer subtypes with differential HK1 and HK2 expression have not been characterized for their sensitivities to HK2 silencing.

Methods

HK1 and HK2 expression in the Cancer Cell Line Encyclopedia dataset was analyzed. A doxycycline-inducible shRNA silencing system was used to examine the effect of HK2 knockdown in cultured cells and in xenograft models of HK1⁻HK2⁺ and HK1⁺HK2⁺ cancers. Glucose consumption and lactate production rates were measured to monitor HK activity in cell culture, and ¹⁸F-FDG PET/CT was used to monitor HK activity in xenograft tumors. A high-throughput screen was performed to search for synthetically lethal compounds in combination with HK2 inhibition in HK1⁻HK2⁺ liver cancer cells, and a combination therapy for liver cancers with this phenotype was developed. A metabolomic analysis was performed to examine changes in cellular energy levels and key metabolites in HK1⁻HK2⁺ cells treated with this combination therapy. The CRISPR Cas9 method was used to establish isogenic HK1⁺HK2⁺ and HK1⁻HK2⁺ cell lines to evaluate HK1⁻HK2⁺ cancer cell sensitivity to the combination therapy.

Results

Most tumors express both HK1 and HK2, and subsets of cancers from a wide variety of tissues of origin express only HK2. Unlike HK1⁺HK2⁺ cancers, HK1⁻HK2⁺ cancers are sensitive to HK2 silencing-induced cytostasis. Synthetic lethality was achieved in HK1⁻HK2⁺ liver cancer cells, by the combination of DPI, a mitochondrial complex I inhibitor, and HK2 inhibition, in HK1⁻HK2⁺ liver cancer cells. Perhexiline, a fatty acid oxidation inhibitor, further sensitizes HK1⁻HK2⁺ liver cancer cells to the complex I/HK2-targeted therapeutic combination. Although HK1⁺HK2⁺ lung cancer H460 cells are resistant to this therapeutic combination, isogenic HK1^KOHK2⁺ cells are sensitive to this therapy.

Conclusions

The HK1⁻HK2⁺ cancer subsets exist among a wide variety of cancer types. Selective inhibition of the HK1⁻HK2⁺ cancer cell-specific energy production pathways (HK2-driven glycolysis, oxidative phosphorylation and fatty acid oxidation), due to the unique presence of only the HK2 isoform, appears promising to treat HK1⁻HK2⁺ cancers. This therapeutic strategy will likely be tolerated by most normal tissues, where only HK1 is expressed.

Electronic supplementary material

The online version of this article (10.1186/s40170-018-0181-8) contains supplementary material, which is available to authorized users.

Mitofusin2 Induces Cell Autophagy of Pancreatic Cancer through Inhibiting the PI3K/Akt/mTOR Signaling Pathway

Aim

Pancreatic cancer is one of the most quickly fatal cancers around the world. Burgeoning researches have begun to prove that mitochondria play a crucial role in cancer treatment. Mitofusin2 (Mfn2) plays an indispensable role in mitochondrial fusion and adjusting function. However, the role and underlying mechanisms of Mfn2 on cell autophagy of pancreatic cancer is still unclear. Our aim was to explore the effect of Mfn2 on multiple biological functions involving cell autophagy in pancreatic cancer.

Methods

Pancreatic cancer cell line, Aspc-1, was treated with Ad-Mfn2 overexpression. Western blotting, caspase-3 activity measurement, and CCK-8 and reactive oxygen species (ROS) assay were used to examine the effects of Mfn2 on pancreatic cancer autophagy, apoptosis, cell proliferation, oxidative stress, and PI3K/Akt/mTOR signaling. The expression of tissue Mfn2 was detected by immunohistochemical staining. Survival analysis of Mfn2 was evaluated by OncoLnc.

Results

Mfn2 improved the expression of LC3-II and Bax and downregulated the expression of P62 and Bcl-2 in pancreatic cancer cells. Meanwhile, Mfn2 also significantly inhibited the expression of p-PI3K, p-Akt, and p-mTOR proteins in pancreatic cancer cells. In addition, Mfn2 inhibited pancreatic cancer cell proliferation and ROS production. Assessment of Kaplan-Meier curves showed that Mfn2⁻ pancreatic cancer has a worse prognosis than Mfn2⁺ pancreatic cancer has.

Conclusions

Our finding suggests that Mfn2 induces cell autophagy of pancreatic cancer through inhibiting the PI3K/Akt/mTOR signaling pathway. Meanwhile, Mfn2 also influences multiple biological functions of pancreatic cancer cells. Mfn2 may act as a therapeutic target in pancreatic cancer treatment.

Breaking down Leukemia Walls: Heteronemin, a Sesterterpene Derivative, Induces Apoptosis in Leukemia Molt4 Cells through Oxidative Stress, Mitochondrial Dysfunction and Induction of Talin Expression

Heteronemin, the most abundant secondary metabolite in the sponge Hippospongia sp., exhibited potent cytotoxic activity against several cancer cell lines. It increased the percentage of apoptotic cells and reactive oxygen species (ROS) in Molt4 cells. The use of ROS scavenger, N-acetyl cysteine (NAC), suppressed both the production of ROS from mitochondria and cell apoptosis that were induced by heteronemin treatment. Heteronemin upregulated talin and phosphorylated talin expression in Molt4 cells but it only upregulated the expression of phosphorylated talin in HEK293 cells. However, pretreatment with NAC reversed these effects. Talin siRNA reversed the activation of pro-apoptotic cleaved caspases 3 and 9. On the other hand, the downstream proteins including FAK and NF-κB (p65) were not affected. In addition, we confirmed that heteronemin directly modulated phosphorylated talin expression through ROS generation resulting in cell apoptosis, but it did not affect talin/FAK complex. Furthermore, heteronemin interfered with actin microfilament and caused morphology changes. Taken together, these findings suggest that the cytotoxic effect of heteronemin is associated with oxidative stress and induction of phosphorylated talin expression. Our results suggest that heteronemin represents an interesting candidate which can be further developed as a drug lead against leukemia.

A Novel Multiple-Read Screen for Metabolically Active Compounds Based on a Genetically Encoded FRET Sensor for ATP

Both glycolysis and mitochondrial energetics are targets of interest for developing antiproliferative cancer therapeutics. We developed a novel multiple-read assay based on long-term expression in K562 cells of a genetically encoded intramolecular Förster resonance energy transfer sensor for adenosine triphosphate (ATP). The assay, conducted in a fluorescent plate reader, can identify compounds that inhibit oxidative phosphorylation-dependent ATP production, glycolysis, or both after short-term treatment. We screened a National Cancer Institute (NCI) compound library, identifying inhibitors of oxidative phosphorylation-dependent ATP production and glycolysis. Three glycolysis inhibitors blocked hexokinase activity, demonstrating that our assay can serve as the initial step in a workflow to identify compounds that inhibit glycolysis via a defined desired mechanism. Finally, upon reviewing the literature, we found surprisingly little evidence that inhibiting glycolysis with small molecules is antiproliferative. Using NCI data on proliferation of K562 cells, we found that inhibitors of oxidative phosphorylation-dependent ATP production were no more antiproliferative than the overall library, whereas all glycolysis inhibitors were in the top third of most effective antiproliferative compounds. Our results thus present a powerful new way to screen for compounds that affect cellular metabolism and also provide important support for the idea that blocking glycosis is antiproliferative.

Mitochondria-targeted platinum(II) complexes induce apoptosis-dependent autophagic cell death mediated by ER-stress in A549 cancer cells

Agents with multiple modes of tumor cell death can be effective chemotherapeutic drugs. One example of a bimodal chemotherapeutic approach is an agent that can induce both apoptosis and autophagic death. Thus far, no clinical anticancer drug has been shown to simultaneously induce both these pathways. Mono-functional platinum complexes are potent anticancer drug candidates which act through mechanisms distinct from cisplatin. Here, we describe the synthesis and characterize of two mono-functional platinum complexes containing 8-substituted quinoline derivatives as ligands, [PtL₁Cl]Cl [L₁ = (Z)-1-(pyridin-2-yl)-N-(quinolin-8-ylmethylene) methanamine] (Mon-Pt-1) and [PtL₂Cl]Cl [L₂ = (Z)-2-(pyridin-2-yl)-N-(quinolin-8-ylmethylene) ethanamine] (Mon-Pt-2). In comparison to cisplatin, Mon-Pt-2 exhibited a greater in vitro cytotoxicity, was more effective in resistant cells and elicited a better anticancer effect. Mechanistic experiments indicate that Mon-Pt-2 mainly accumulates in mitochondria, and stimulates significant TrxR inhibition ROS release and an ER stress response, mediated by mitochondrial dysfunction, ultimately resulting in a simultaneous induction of apoptosis and autophagy. Importantly, compared to cisplatin, Mon-Pt-2 exhibits lower acute toxicity and better anticancer activity in a murine tumor model. To the best of our knowledge, Mon-Pt-2 is the first mono-functional platinum complex inducing pro-death autophagy and apoptosis of cancer cells.

Mitochondrial Delivery of Phenol Substructure Triggers Mitochondrial Depolarization and Apoptosis of Cancer Cells

Antitumor chemotherapy remains one of the most important challenge of the medicinal chemistry. Emerging research in chemotherapy is focused on exploiting the biochemical differences between cancer cell and normal cell metabolism in order to reduce the side effects and increase antitumor therapy efficacy. The higher mitochondrial transmembrane potential of cancer cells compared to not-transformed cells favors the intra-mitochondrial accumulation of cationic drugs in the former. This feature could be exploited to allow selective delivery of antineoplastic drugs to the cancer cells. In this work we designed and synthetized phenol derivatives joined to the triphenylphosphonium (TPP) cation, a well-known vector for mitochondrial targeting. Two designed phenol TPP-derivatives 1 and 2 show remarkable cytotoxic activity against different cancer cell lines, but were less toxic against normal cells. The differential cytotoxicity relied on the higher mitochondrial biogenesis and oxidative-phosphorylation metabolism of the former. By reducing mitochondrial mass and energetic metabolism, and increasing at the same time the levels of intra-mitochondrial reactive oxygen species, phenol TPP-derivatives 1 and 2 induced mitochondria depolarization and triggered a caspase 9/3-mediated apoptosis, limited to cancer cells. This work provides the rationale to further develop phenol TPP-derivatives targeting mitochondria as new and selective anticancer tools.

SIRT6 overexpression inhibits HIF1α expression and its impact on tumor angiogenesis in lung cancer

OBJECTIVE

To investigate the effect of silencing information regulator 6 (SIRT6) on HIF1α expression of cell line A549 in non-small cell lung cancer and on tumor angiogenesis in lung cancer.

METHODS

Cell line A549 in the logarithmic growth phase was transfected with Ad-SIRT6 and Ad-null respectively. According to the study design, the cells were divided into control group, Ad-null group and Ad-SIRT6 group. The HIF1α and HIF2α mRNA expression in each group were detected by real-time quantitative PCR (qPCR). The level of prolyl hydroxylase (PHD) 1-3 after 48 h of Ad-SIRT6-transfected cell line A549 and the levels of VEGF-C, VEGF-D, VEGFR-2 and VEGFR-3 in the supernatants were determined by ELISA. The nude mice were injected subcutaneously with Ad-null or Ad-SIRT6 transfected cell line A549. The tumor volume was observed at 6, 12, 18, 24 and 30 d after inoculation, and the tumor mass was weighed at 30 d. Also, microvessel density (MVD) and the number of positive HIF1α and VEGF cells were detected by immunohistochemistry. The VEGF and HIF1α levels in tumor tissue were detected by ELISA and qPCR respectively.

RESULTS

qPCR showed that the levels of HIF-1α mRNA, VEGF-C, VEGF-D, VEGFR-2 and VEGFR-3 in the supernatant were decreased, the level of PHD2 was increased (P<0.05), and the levels of HIF-2α mRNA, PHD1 and PHD3 did not change much (P>0.05) in the Ad-SIRT6 group as compared with those in the control group and Ad-null group. The tumor growth rate was decreased, and the tumor volume at 12-30 d after inoculation was less in the Ad-SIRT6 group than in the control group and Ad-null group (P<0.05); the tumor mass was also lower than that of control and Ad-null groups (P<0.05). Immunohistochemistry showed that MVD and the number of HIF-1α and VEGF positive cells were less in the Ad-SIRT6 group than in control and Ad-null groups (P<0.05); and HIF-1α and VEGF levels in tumor tissue were decreased in the Ad-SIRT6 group compared to the control and Ad-null groups (P<0.05). There were no significant differences in the above measurements between the control group and Ad-null group (P>0.05).

CONCLUSION

SIRT6 overexpression can inhibit HIF1α and VEGF expression, promoting PHD2 expression, which can inhibit angiogenesis and xenograft growth and may play a role in reducing HIF1α and VEGF expression.

Oxidative Phosphorylation as an Emerging Target in Cancer Therapy

Cancer cells have upregulated glycolysis compared with normal cells, which has led many to the assumption that oxidative phosphorylation (OXPHOS) is downregulated in all cancers. However, recent studies have shown that OXPHOS can be also upregulated in certain cancers, including leukemias, lymphomas, pancreatic ductal adenocarcinoma, high OXPHOS subtype melanoma, and endometrial carcinoma, and that this can occur even in the face of active glycolysis. OXPHOS inhibitors could therefore be used to target cancer subtypes in which OXPHOS is upregulated and to alleviate therapeutically adverse tumor hypoxia. Several drugs including metformin, atovaquone, and arsenic trioxide are used clinically for non-oncologic indications, but emerging data demonstrate their potential use as OXPHOS inhibitors. We highlight novel applications of OXPHOS inhibitors with a suitable therapeutic index to target cancer cell metabolism. Clin Cancer Res; 24(11); 2482-90. ©2018 AACR.

Activatable Semiconducting Theranostics: Simultaneous Generation and Ratiometric Photoacoustic Imaging of Reactive Oxygen Species In Vivo

Enhancing the generation of reactive oxygen species (ROS) is an effective anticancer strategy. However, it is a great challenge to control the production and to image ROS in vivo, both of which are vital for improving the efficacy and accuracy of cancer therapy. Herein, an activatable semiconducting theranostic nanoparticle (NP) platform is developed that can simultaneously enhance ROS generation while self-monitoring its levels through ratiometric photoacoustic (PA) imaging. The NP platform can further guide in vivo therapeutic effect in tumors. The theranostic NP platform is composed of: (i) cisplatin prodrug and ferric ion catalyst for ROS generation, a part of combination cancer therapy; and (ii) a ratiometric PA imaging nanoprobe consisting of inert semiconducting perylene-diimide (PDI) and ROS activatable near-infrared dye (IR790s), used in ratiometric PA imaging of ROS during cancer treatment. Ratiometric PA signals are measured at two near-infrared excitation wavelengths: 680 and 790 nm for PDI and IR790s, respectively. The measurements show highly accurate visualization of ^• OH generation in vivo. This novel ROS responsive organic theranostic NP allows not only synergistic cancer chemotherapy but also real-time monitoring of the therapeutic effect through ratiometric PA imaging.

Mitochondria-Targeted Honokiol Confers a Striking Inhibitory Effect on Lung Cancer via Inhibiting Complex I Activity

We synthesized a mitochondria-targeted honokiol (Mito-HNK) that facilitates its mitochondrial accumulation; this dramatically increases its potency and efficacy against highly metastatic lung cancer lines in vitro, and in orthotopic lung tumor xenografts and brain metastases in vivo. Mito-HNK is >100-fold more potent than HNK in inhibiting cell proliferation, inhibiting mitochondrial complex ?, stimulating reactive oxygen species generation, oxidizing mitochondrial peroxiredoxin-3, and suppressing the phosphorylation of mitoSTAT3. Within lung cancer brain metastases in mice, Mito-HNK induced the mediators of cell death and decreased the pathways that support invasion and proliferation. In contrast, in the non-malignant stroma, Mito-HNK suppressed pathways that support metastatic lesions, including those involved in inflammation and angiogenesis. Mito-HNK showed no toxicity and targets the metabolic vulnerabilities of primary and metastatic lung cancers. Its pronounced anti-invasive and anti-metastatic effects in the brain are particularly intriguing given the paucity of treatment options for such patients either alone or in combination with standard chemotherapeutics.

Targeted reversal and phosphorescence lifetime imaging of cancer cell metabolism via a theranostic rhenium(I)-DCA conjugate

Cancer cell metabolism is quite different from normal cells. Targeting cancer metabolism and untuning the tumor metabolic machine has emerged as a promising strategy for cancer therapy. We have developed a multi-functional Re-dca conjugate (Re-dca 2) by conjugating the metabolic modulator dichloroacetate (DCA) to mitochondria-targeted rhenium(I) complex, allowing its efficient penetration into cancer cells and selective accumulation in mitochondria, thus achieving the cancer cell metabolism reversal from glycolysis to glucose oxidation at pharmacologically relevant DCA doses. Mechanism studies confirm the inhibition effect of Re-dca 2 on the activity of pyruvate dehydrogenase kinase (PDK) and capture the metabolic reversal window in Re-dca 2 treated NCI-1229 cells at the early stage of drug treatment, resulting in selective killing of malignant cells cocultured with normal cells, significant inhibition of cancer cell metastasis and invasion, as well as excellent anti-angiogenesis activities in zebrafish embryos. By comparison, DCA-free Re(I) analogue is also investigated under the same conditions. Although this analogue also exhibits cytotoxicity due to the Re(I) core, metabolic reversal is not induced by this analogue and its anti-metastasis activity is much lower than Re-dca 2, indicating the synergistic effect of Re(I) core and DCA moiety on cancer therapy. In vivo anti-cancer investigations also indicate that the mitochondria-targeted Re-dca 2 can effectively inhibit the tumor growth without affecting the body weight of nude mice, and the therapeutic effect is much better than the DCA-free Re(I) analogue 2a. Simultaneously, the O₂-sensitive phosphorescent lifetimes of Re-dca 2 can be utilized for PLIM imaging of intracellular oxygen consumption, thus reflecting the Re-dca 2 induced glycolysis-to-glucose oxidation reversal at the early drug treatment stage. The excellent phosphorescence of Re-dca 2 can also be utilized for real-time tracking of mitochondrial morphological changes during treatment. In a word, rational design of phosphorescent metallodrug and metabolic modulator conjugates for synergistic treatment is a promising strategy for simultaneous untuning and tracking tumor metabolic machine, thus providing new clues for cancer therapy and mechanisms.

Biological and metabolic effects of IACS-010759, an OxPhos inhibitor, on chronic lymphocytic leukemia cells

Blood cells from patients with chronic lymphocytic leukemia (CLL) are replicationally quiescent but transcriptionally, translationally, and metabolically active. Recently, we demonstrated that oxidative phosphorylation (OxPhos) is a predominant pathway in CLL for energy production and is further augmented in the presence of the stromal microenvironment. Importantly, CLL cells from patients with poor prognostic markers showed increased OxPhos. From these data, we theorized that OxPhos can be targeted to treat CLL. IACS-010759, currently in clinical development, is a small-molecule, orally bioavailable OxPhos inhibitor that targets mitochondrial complex I. Treatment of primary CLL cells with IACS-010759 greatly inhibited OxPhos but caused only minor cell death at 24 and 48 h. In the presence of stroma, the drug successfully inhibited OxPhos and diminished intracellular ribonucleotide pools. However, glycolysis and glucose uptake were induced as compensatory mechanisms. To mitigate the upregulated glycolytic flux, we used 2-deoxy-D-glucose in combination with IACS-010759. This combination reduced both OxPhos and glycolysis and induced cell death. Consistent with these data, low-glucose culture conditions sensitized CLL cells to IACS-010759. Collectively, these data suggest that CLL cells adapt to use a different metabolic pathway when OxPhos is inhibited and that targeting both OxPhos and glycolysis pathways is necessary for biological effect.

Development of novel amino-quinoline-5,8-dione derivatives as NAD(P)H:quinone oxidoreductase 1 (NQO1) inhibitors with potent antiproliferative activities

Fourteen novel amino-quinoline-5,8-dione derivatives (6a-h and 7a-h) were designed and synthesized by coupling different alkyl- or aryl-amino fragments at the C6- or C7-position of quinoline-5,8-dione. All target compounds showed antiproliferative potency in the low micromolar range in both drug sensitive HeLaS3 and multidrug resistant KB-vin cell lines. Compounds 6h, 6d, 7a, and 7d exhibited more potent antiproliferative effects than the other compounds. Especially, compounds 6d and 7d displayed NQO1-dependent cytotoxicity and competitive NQO1 inhibitory effects in both drug sensitive HeLaS3 and multidrug resistant KB-vin cell lines. Furthermore, compounds 6h, 6d, 7a, and 7d induced a dose-dependent lethal mitochondrial dysfunction in both drug sensitive HeLaS3 and multidrug resistant KB-vin cells by increasing intracellular reactive oxygen species (ROS) levels. Notably, compound 7d selectively inhibited cancer cells, but not non-tumor liver cell proliferation in vitro, and significantly triggered HeLaS3 cell apoptosis by regulating apoptotic proteins of Bcl-2, Bax, and cleaved caspase-3 in a dose-dependent manner. Our findings suggest that these novel C6- or C7-substituted amino-quinoline-5,8-dione derivatives, such as 7d, could be further developed in the future as potent and selective antitumor agents to potentially circumvent multi-drug resistance (MDR).

Higher expression of A-kinase anchoring-protein 1 predicts poor prognosis in human hepatocellular carcinoma

A-kinase anchoring protein 1 (AKAP1) plays important regulatory roles in the regulation of mitochondrial function, oxidative metabolism, and cell survival. However, the expression pattern and prognostic value of AKAP1 in hepatocellular carcinoma (HCC) remains unclear. AKAP1 expression levels in tumor and matched non-tumor tissues were evaluated using reverse transcription-quantitative polymerase chain reaction and immunohistochemical staining. Kaplan-Meier and Cox regression analyses were used to analyze the survival rates. We found that AKAP1 protein expression was increased in HCC tissues, and high AKAP1 expression was associated with tumor size (P=0.024), Tumor-Node-Metastasis stage (P=0.0296) and portal vein thrombosis (P=0.00498). Kaplan-Meier survival analyses further revealed that high AKAP1 expression was associated with poor overall (P=0.004) and disease-free survival (DFS) (P=0.002) rates in patients with HCC. Multivariate survival analysis revealed that AKAP1 served as an independent poor prognostic factor for DFS rates. The findings of the present study indicated that AKAP1 expression may contribute to HCC progression. High AKAP1 expression could serve as a valuable prognostic biomarker in predicting the survival of patients with HCC following radical resection.

The Oncojanus Paradigm of Respiratory Complex I

Mitochondrial respiratory function is now recognized as a pivotal player in all the aspects of cancer biology, from tumorigenesis to aggressiveness and chemotherapy resistance. Among the enzymes that compose the respiratory chain, by contributing to energy production, redox equilibrium and oxidative stress, complex I assumes a central role. Complex I defects may arise from mutations in mitochondrial or nuclear DNA, in both structural genes or assembly factors, from alteration of the expression levels of its subunits, or from drug exposure. Since cancer cells have a high-energy demand and require macromolecules for proliferation, it is not surprising that severe complex I defects, caused either by mutations or treatment with specific inhibitors, prevent tumor progression, while contributing to resistance to certain chemotherapeutic agents. On the other hand, enhanced oxidative stress due to mild complex I dysfunction drives an opposite phenotype, as it stimulates cancer cell proliferation and invasiveness. We here review the current knowledge on the contribution of respiratory complex I to cancer biology, highlighting the double-edged role of this metabolic enzyme in tumor progression, metastasis formation, and response to chemotherapy.

PGC1α promotes cholangiocarcinoma metastasis by upregulating PDHA1 and MPC1 expression to reverse the Warburg effect

PGC1α acts as a central regulator of mitochondrial metabolism, whose role in cancer progression has been highlighted but remains largely undefined. Especially, it is completely unknown about the effect of PGC1α on cholangiocarcinoma (CCA). Here we showed that PGC1α overexpression had no impact on CCA growth despite the decreased expression of PGC1α in CCA compared with adjacent normal tissue. Instead, PGC1α overexpression-promoted CCA metastasis both in vitro and in vivo. Mechanistically, for the first time, we illuminated that PGC1α reversed the Warburg effect by upregulating the expression of pyruvate dehydrogenase E1 alpha 1 subunit and mitochondrial pyruvate carrier 1 to increase pyruvate flux into the mitochondria for oxidation, whereas simultaneously promoting mitochondrial biogenesis and fusion to mediate the metabolic switch to oxidative phosphorylation. On the one hand, enhanced mitochondrial oxidation metabolism correlated with elevated reactive oxygen species (ROS) production; on the other hand, increased PGC1α expression upregulated the expression levels of mRNA for several ROS-detoxifying enzymes. To this end, the ROS levels, which were elevated but below a critical threshold, did not inhibit CCA cells proliferation. And the moderately increased ROS facilitated metastatic dissemination of CCA cells, which can be abrogated by antioxidants. Our study suggests the potential utility of developing the PGC1α-targeted therapies or blocking PGC1α signaling axis for inhibiting CCA metastasis.

Phenformin-Induced Mitochondrial Dysfunction Sensitizes Hepatocellular Carcinoma for Dual Inhibition of mTOR

Purpose: Hepatocellular carcinoma (HCC) ranks second in cancer mortality and has limited therapeutic options. We recently described the synergistic effect of allosteric and ATP-site competitive inhibitors against the mTOR for the treatment of HCC. However, such inhibitors induce hyperglycemia and increase mitochondrial efficiency. Here we determined whether the mitochondrial complex I inhibitor phenformin could reverse both side effects, impose an energetic stress on cancer cells, and suppress the growth of HCC.Experimental Design: Human HCC cell lines were used in vitro to access the signaling and energetic impact of mTOR inhibitors and phenformin, either alone or in combination. Next, the therapeutic utility of these drugs alone or in combination was investigated preclinically in human orthotopic tumors implanted in mice, by analyzing their impact on the tumor burden and overall survival.Results: We found phenformin caused mitochondrial dysfunction and fragmentation, inducing a compensatory shift to glycolysis. In contrast, dual inhibition of mTOR impaired cell growth and glycolysis, while increasing mitochondrial fusion and efficiency. In a mouse model of human HCC, dual inhibition of mTOR, together with phenformin, was highly efficacious in controlling tumor burden. However, more strikingly, pretreatment with phenformin sensitized tumors to dual inhibition of mTOR, leading to a dramatic improvement in survival.Conclusions: Treatment of HCC cells in vitro with the biguanide phenformin causes a metabolic shift to glycolysis, mitochondrial dysfunction and fragmentation, and dramatically sensitizes orthotopic liver tumors to dual inhibition of mTOR. We therefore propose this therapeutic approach should be tested clinically in HCC. Clin Cancer Res; 24(15); 3767-80. ©2018 AACR.

Role of metabolism in cancer cell radioresistance and radiosensitization methods

BACKGROUND

Radioresistance is a major factor leading to the failure of radiotherapy and poor prognosis in tumor patients. Following the application of radiotherapy, the activity of various metabolic pathways considerably changes, which may result in the development of resistance to radiation.

MAIN BODY

Here, we discussed the relationships between radioresistance and mitochondrial and glucose metabolic pathways, aiming to elucidate the interplay between the tumor cell metabolism and radiotherapy resistance. In this review, we additionally summarized the potential therapeutic targets in the metabolic pathways.

SHORT CONCLUSION

The aim of this review was to provide a theoretical basis and relevant references, which may lead to the improvement of the sensitivity of radiotherapy and prolong the survival of cancer patients.

Omega-3 fatty acids, membrane remodeling and cancer prevention

Proteins are often credited as the macromolecule responsible for performing critical cellular functions, however lipids have recently garnered more attention as our understanding of their role in cell function and human health becomes more apparent. Although cellular membranes are the lipid environment in which many proteins function, it is now apparent that protein and lipid assemblies can be organized to form distinct micro- or nanodomains that facilitate signaling events. Indeed, it is now appreciated that cellular function is partly regulated by the specific spatiotemporal lipid composition of the membrane, down to the nanosecond and nanometer scale. Furthermore, membrane composition is altered during human disease processes such as cancer and obesity. For example, an increased rate of lipid/cholesterol synthesis in cancerous tissues has long been recognized as an important aspect of the rewired metabolism of transformed cells. However, the contribution of lipids/cholesterol to cellular function in disease models is not yet fully understood. Furthermore, an important consideration in regard to human health is that diet is a major modulator of cell membrane composition. This can occur directly through incorporation of membrane substrates, such as fatty acids, e.g., n-3 polyunsaturated fatty acids (n-3 PUFA) and cholesterol. In this review, we describe scenarios in which changes in membrane composition impact human health. Particular focus is placed on the importance of intrinsic lipid/cholesterol biosynthesis and metabolism and extrinsic dietary modification in cancer and its effect on plasma membrane properties.

Organometallic Gold(III) Complexes Similar to Tetrahydroisoquinoline Induce ER-Stress-Mediated Apoptosis and Pro-Death Autophagy in A549 Cancer Cells

Agents inducing both apoptosis and autophagic death can be effective chemotherapeutic drugs. In our present work, we synthesized two organometallic gold(III) complexes harboring C^N ligands that structurally resemble tetrahydroisoquinoline (THIQ): Cyc-Au-1 (AuL¹Cl₂, L¹ = 3,4-dimethoxyphenethylamine) and Cyc-Au-2 (AuL²Cl₂, L² = methylenedioxyphenethylamine). In screening their in vitro activity, we found both gold complexes exhibited lower toxicity, lower resistance factors, and better anticancer activity than those of cisplatin. The organometallic gold(III) complexes accumulate in mitochondria and induce elevated ROS and an ER stress response through mitochondrial dysfunction. These effects ultimately result in simultaneous apoptosis and autophagy. Importantly, compared to cisplatin, Cyc-Au-2 exhibits lower toxicity and better anticancer activity in a murine tumor model. To the best of our knowledge, Cyc-Au-2 is the first organometallic Au(III) compound that induces apoptosis and autophagic death. On the basis of our results, we believe Cyc-Au-2 to be a promising anticancer agent or lead compound for further anticancer drug development.

A mitochondria-targeting supramolecular photosensitizer based on pillar[5]arene for photodynamic therapy

A mitochondria-targeting supramolecular photosensitizer system TPP-QAS/WP5/DTAB was constructed based on a host-guest inclusion complex. The supramolecular system could efficiently release and activate TPP-QASs in an acidic environment, which have been demonstrated to preferentially accumulate in mitochondria. Singlet oxygen (¹O₂) could be in situ generated in mitochondria under light irradiation, further enhancing the PDT efficacy.

Mitochondria-Targeting Peptoids

Mitochondria-specific delivery methods offer a valuable tool for studying mitochondria-related diseases and provide breakthroughs in therapeutic development. Although several small-molecule and peptide-based transporters have been developed, peptoids, proteolysis-resistant peptidomimetics, are a promising alternative to current approaches. We designed a series of amphipathic peptoids and evaluated their cellular uptake and mitochondrial localization. Two peptoids with cyclohexyl residues demonstrated highly efficient cell penetration and mitochondrial localization without significant adverse effects on the cells and mitochondria. These mitochondria-targeting peptoids could facilitate the selective and robust targeted delivery of bioactive compounds, such as drugs, antioxidants, and photosensitizers, with minimal off-target effects.

Human Elongation Factor 4 Regulates Cancer Bioenergetics by Acting as a Mitochondrial Translation Switch

Mitochondria regulate cellular bioenergetics and redox states and influence multiple signaling pathways required for tumorigenesis. In this study, we determined that the mitochondrial translation elongation factor 4 (EF4) is a critical component of tumor progression. EF4 was ubiquitous in human tissues with localization to the mitochondria (mtEF4) and performed quality control on respiratory chain biogenesis. Knockout of mtEF4 induced respiratory chain complex defects and apoptosis, while its overexpression stimulated cancer development. In multiple cancers, expression of mtEF4 was increased in patient tumor tissues. These findings reveal that mtEF4 expression may promote tumorigenesis via an imbalance in the regulation of mitochondrial activities and subsequent variation of cellular redox. Thus, dysregulated mitochondrial translation may play a vital role in the etiology and development of diverse human cancers.Significance: Dysregulated mitochondrial translation drives tumor development and progression. Cancer Res; 78(11); 2813-24. ©2018 AACR.

Targeting CPT1A-mediated fatty acid oxidation sensitizes nasopharyngeal carcinoma to radiation therapy

Nasopharyngeal carcinoma (NPC) has a particularly high prevalence in southern China, southeastern Asia and northern Africa. Radiation resistance remains a serious obstacle to successful treatment in NPC. This study aimed to explore the metabolic feature of radiation-resistant NPC cells and identify new molecular-targeted agents to improve the therapeutic effects of radiotherapy in NPC. Methods: Radiation-responsive and radiation-resistant NPC cells were used as the model system in vitro and in vivo. Metabolomics approach was used to illustrate the global metabolic changes. ¹³C isotopomer tracing experiment and Seahorse XF analysis were undertaken to determine the activity of fatty acid oxidation (FAO). qRT-PCR was performed to evaluate the expression of essential FAO genes including CPT1A. NPC tumor tissue microarray was used to investigate the prognostic role of CPT1A. Either RNA interference or pharmacological blockade by Etomoxir were used to inhibit CPT1A. Radiation resistance was evaluated by colony formation assay. Mitochondrial membrane potential, apoptosis and neutral lipid content were measured by flow cytometry analysis using JC-1, Annexin V and LipidTOX Red probe respectively. Molecular markers of mitochondrial apoptosis were detected by western blot. Xenografts were treated with Etomoxir, radiation, or a combination of Etomoxir and radiation. Mitochondrial apoptosis and lipid droplets content of tumor tissues were detected by cleaved caspase 9 and Oil Red O staining respectively. Liquid chromatography coupled with tandem mass spectrometry approach was used to identify CPT1A-binding proteins. The interaction of CPT1A and Rab14 were detected by immunoprecipitation, immunofluorescence and in situ proximity ligation analysis. Fragment docking and direct coupling combined computational protein-protein interaction prediction method were used to predict the binding interface. Fatty acid trafficking was measured by pulse-chase assay using BODIPY C16 and MitoTracker Red probe. Results: FAO was active in radiation-resistant NPC cells, and the rate-limiting enzyme of FAO, carnitine palmitoyl transferase 1 A (CPT1A), was consistently up-regulated in these cells. The protein level of CPT1A was significantly associated with poor overall survival of NPC patients following radiotherapy. Inhibition of CPT1A re-sensitized NPC cells to radiation therapy by activating mitochondrial apoptosis both in vitro and in vivo. In addition, we identified Rab14 as a novel CPT1A binding protein. The CPT1A-Rab14 interaction facilitated fatty acid trafficking from lipid droplets to mitochondria, which decreased radiation-induced lipid accumulation and maximized ATP production. Knockdown of Rab14 attenuated CPT1A-mediated fatty acid trafficking and radiation resistance. Conclusion: An active FAO is a vital signature of NPC radiation resistance. Targeting CPT1A could be a beneficial regimen to improve the therapeutic effects of radiotherapy in NPC patients. Importantly, the CPT1A-Rab14 interaction plays roles in CPT1A-mediated radiation resistance by facilitating fatty acid trafficking. This interaction could be an attractive interface for the discovery of novel CPT1A inhibitors.

Epistructured catechins, EGCG and EC facilitate apoptosis induction through targeting de novo lipogenesis pathway in HepG2 cells

Background

Abnormally high expression of the mammalian de novo lipogenesis (DNL) pathway in various cancer cells promotes cell over-proliferation and resistance to apoptosis. Inhibition of key enzymes in the DNL pathway, namely, ATP citrate lyase, acetyl-CoA carboxylase, and fatty acid synthase (FASN) can increase apoptosis without cytotoxicity to non-cancerous cells, leading to the search for and presentation of novel selective and powerful targets for cancer therapy. Previous studies reported that epistructured catechins, epigallocatechin gallate (EGCG) and epicatechin (EC) exhibit different mechanisms regarding a strong inducer of apoptosis in various cancer cell lines. Thus, the current study investigated the growth inhibitory effect of EGCG and EC, on the enzyme expression and activity of the DNL pathway, which leads to the prominent activity of carnitine palmitoyl transferase-1 (CPT-1) mediating apoptosis in HepG2 cells.

Methods

The cytotoxicity on HepG2 cells of EGCG and EC was determined by MTT assay. Cell death caused by apoptosis, the dissipation of mitochondrial membrane potential (MMP), and cell cycle arrest were then detected by flow cytometry. We further investigated the decrease of fatty acid levels associated with DNL retardation, followed by evaluation of DNL protein expression. Then, the negative inhibitory effect of depleted fatty acid synthesis on malonyl-CoA synthesis followed by regulating of CPT-1 activity was investigated. Thereafter, we inspected the enhanced reactive oxygen species (ROS) generation, which is recognized as one of the causes of apoptosis in HepG2 cells.

Results

We found that EGCG and EC decreased cancer cell viability by increasing apoptosis as well as causing cell cycle arrest in HepG2 cells. Apoptosis was associated with MMP dissipation. Herein, EGCG and EC inhibited the expression of FASN enzymes contributing to decreasing fatty acid levels. Notably, this decrease consequently showed a suppressing effect on the CPT-1 activity. We suggest that epistructured catechin-induced apoptosis targets CPT-1 activity suppression mediated through diminishing the DNL pathway in HepG2 cells. In addition, increased ROS production was found after treatment with EGCG and EC, indicating oxidative stress mechanism-induced apoptosis. The strong apoptotic effect of EGCG and EC was specifically absent in primary human hepatocytes.

Conclusion

Our supportive evidence confirms potential alternative cancer treatments by EGCG and EC that selectively target the DNL pathway.

Repositioning chlorpromazine for treating chemoresistant glioma through the inhibition of cytochrome c oxidase bearing the COX4-1 regulatory subunit

Patients with glioblastoma have one of the lowest overall survival rates among patients with cancer. Standard of care for patients with glioblastoma includes temozolomide and radiation therapy, yet 30% of patients do not respond to these treatments and nearly all glioblastoma tumors become resistant. Chlorpromazine is a United States Food and Drug Administration-approved phenothiazine widely used as a psychotropic in clinical practice. Recently, experimental evidence revealed the anti-proliferative activity of chlorpromazine against colon and brain tumors. Here, we used chemoresistant patient-derived glioma stem cells and chemoresistant human glioma cell lines to investigate the effects of chlorpromazine against chemoresistant glioma. Chlorpromazine selectively and significantly inhibited proliferation in chemoresistant glioma cells and glioma stem cells. Mechanistically, chlorpromazine inhibited cytochrome c oxidase (CcO, complex IV) activity from chemoresistant but not chemosensitive cells, without affecting other mitochondrial complexes. Notably, our previous studies revealed that the switch to chemoresistance in glioma cells is accompanied by a switch from the expression of CcO subunit 4 isoform 2 (COX4-2) to COX4-1. In this study, chlorpromazine induced cell cycle arrest selectively in glioma cells expressing COX4-1, and computer-simulated docking studies indicated that chlorpromazine binds more tightly to CcO expressing COX4-1 than to CcO expressing COX4-2. In orthotopic mouse brain tumor models, chlorpromazine treatment significantly increased the median overall survival of mice harboring chemoresistant tumors. These data indicate that chlorpromazine selectively inhibits the growth and proliferation of chemoresistant glioma cells expressing COX4-1. The feasibility of repositioning chlorpromazine for selectively treating chemoresistant glioma tumors should be further explored.

The mitochondrial translation machinery as a therapeutic target in Myc-driven lymphomas

The oncogenic transcription factor Myc is required for the progression and maintenance of diverse tumors. This has led to the concept that Myc itself, Myc-activated gene products, or associated biological processes might constitute prime targets for cancer therapy. Here, we present an in vivo reverse-genetic screen targeting a set of 241 Myc-activated mRNAs in mouse B-cell lymphomas, unraveling a critical role for the mitochondrial ribosomal protein (MRP) Ptcd3 in tumor maintenance. Other MRP-coding genes were also up regulated in Myc-induced lymphoma, pointing to a coordinate activation of the mitochondrial translation machinery. Inhibition of mitochondrial translation with the antibiotic Tigecycline was synthetic-lethal with Myc activation, impaired respiratory activity and tumor cell survival in vitro, and significantly extended lifespan in lymphoma-bearing mice. We have thus identified a novel Myc-induced metabolic dependency that can be targeted by common antibiotics, opening new therapeutic perspectives in Myc-overexpressing tumors.

The interplay of reactive oxygen species and the epidermal growth factor receptor in tumor progression and drug resistance

Background

The epidermal growth factor receptor (EGFR) plays important roles in cell survival, growth, differentiation, and tumorigenesis. Dysregulation of the EGFR is a common mechanism in cancer progression especially in non-small cell lung cancer (NSCLC).

Main body

Suppression of the EGFR-mediated signaling pathway is used in cancer treatment. Furthermore, reactive oxygen species (ROS)-induced oxidative stress from mitochondrial dysfunction or NADPH oxidase (NOX) overactivation and ectopic expression of antioxidative enzymes were also indicated to be involved in EGFR-mediated tumor progression (proliferation, differentiation, migration, and invasion) and drug resistance (EGFR tyrosine kinase inhibitor (TKI)). The products of NOX, superoxide and hydrogen peroxide, are considered to be major types of ROS. ROS are not only toxic materials to cells but also signaling regulators of tumor progression. Oxidation of both the EGFR and downstream phosphatases by ROS enhances EGFR-mediated signaling and promotes tumor progression. This review primarily focuses on the recent literature with respect to the roles of the EGFR and ROS and correlations between ROS and the EGFR in tumor progression and EGFR TKI resistance.

Short conclusion

The evidence discussed in this article can serve as a basis for basic and clinical research to understand how to modulate ROS levels to control the development and drug resistance of cancers.

Metaboloptics: Visualization of the tumor functional landscape via metabolic and vascular imaging

Many cancers adeptly modulate metabolism to thrive in fluctuating oxygen conditions; however, current tools fail to image metabolic and vascular endpoints at spatial resolutions needed to visualize these adaptations in vivo. We demonstrate a high-resolution intravital microscopy technique to quantify glucose uptake, mitochondrial membrane potential (MMP), and SO₂ to characterize the in vivo phentoypes of three distinct murine breast cancer lines. Tetramethyl rhodamine, ethyl ester (TMRE) was thoroughly validated to report on MMP in normal and tumor-bearing mice. Imaging MMP or glucose uptake together with vascular endpoints revealed that metastatic 4T1 tumors maintained increased glucose uptake across all SO₂ (“Warburg effect”), and also showed increased MMP relative to normal tissue. Non-metastatic 67NR and 4T07 tumor lines both displayed increased MMP, but comparable glucose uptake, relative to normal tissue. The 4T1 peritumoral areas also showed a significant glycolytic shift relative to the tumor regions. During a hypoxic stress test, 4T1 tumors showed significant increases in MMP with corresponding significant drops in SO₂, indicative of intensified mitochondrial metabolism. Conversely, 4T07 and 67NR tumors shifted toward glycolysis during hypoxia. Our findings underscore the importance of imaging metabolic endpoints within the context of a living microenvironment to gain insight into a tumor’s adaptive behavior.

Mitochondria-Endoplasmic Reticulum Contact Sites Function as Immunometabolic Hubs that Orchestrate the Rapid Recall Response of Memory CD8+ T Cells

Glycolysis is linked to the rapid response of memory CD8⁺ T cells, but the molecular and subcellular structural elements enabling enhanced glucose metabolism in nascent activated memory CD8⁺ T cells are unknown. We found that rapid activation of protein kinase B (PKB or AKT) by mammalian target of rapamycin complex 2 (mTORC2) led to inhibition of glycogen synthase kinase 3β (GSK3β) at mitochondria-endoplasmic reticulum (ER) junctions. This enabled recruitment of hexokinase I (HK-I) to the voltage-dependent anion channel (VDAC) on mitochondria. Binding of HK-I to VDAC promoted respiration by facilitating metabolite flux into mitochondria. Glucose tracing pinpointed pyruvate oxidation in mitochondria, which was the metabolic requirement for rapid generation of interferon-γ (IFN-γ) in memory T cells. Subcellular organization of mTORC2-AKT-GSK3β at mitochondria-ER contact sites, promoting HK-I recruitment to VDAC, thus underpins the metabolic reprogramming needed for memory CD8⁺ T cells to rapidly acquire effector function.

VDAC Regulation: A Mitochondrial Target to Stop Cell Proliferation

Cancer metabolism is emerging as a chemotherapeutic target. Enhanced glycolysis and suppression of mitochondrial metabolism characterize the Warburg phenotype in cancer cells. The flux of respiratory substrates, ADP, and Pi into mitochondria and the release of mitochondrial ATP to the cytosol occur through voltage-dependent anion channels (VDACs) located in the mitochondrial outer membrane. Catabolism of respiratory substrates in the Krebs cycle generates NADH and FADH₂ that enter the electron transport chain (ETC) to generate a proton motive force that maintains mitochondrial membrane potential (ΔΨ) and is utilized to generate ATP. The ETC is also the major cellular source of mitochondrial reactive oxygen species (ROS). αβ-Tubulin heterodimers decrease VDAC conductance in lipid bilayers. High constitutive levels of cytosolic free tubulin in intact cancer cells close VDAC decreasing mitochondrial ΔΨ and mitochondrial metabolism. The VDAC-tubulin interaction regulates VDAC opening and globally controls mitochondrial metabolism, ROS formation, and the intracellular flow of energy. Erastin, a VDAC-binding molecule lethal to some cancer cell types, and erastin-like compounds identified in a high-throughput screening antagonize the inhibitory effect of tubulin on VDAC. Reversal of tubulin inhibition of VDAC increases VDAC conductance and the flux of metabolites into and out of mitochondria. VDAC opening promotes a higher mitochondrial ΔΨ and a global increase in mitochondrial metabolism leading to high cytosolic ATP/ADP ratios that inhibit glycolysis. VDAC opening also increases ROS production causing oxidative stress that, in turn, leads to mitochondrial dysfunction, bioenergetic failure, and cell death. In summary, antagonism of the VDAC-tubulin interaction promotes cell death by a "double-hit model" characterized by reversion of the proproliferative Warburg phenotype (anti-Warburg) and promotion of oxidative stress.

Impairing Powerhouse in Colon Cancer Cells by Hydrazide-Hydrazone-Based Small Molecule

Mitochondrion has emerged as one of the unconventional targets in next-generation cancer therapy. Hence, small molecules targeting mitochondria in cancer cells have immense potential in the next-generation anticancer therapeutics. In this report, we have synthesized a library of hydrazide-hydrazone-based small molecules and identified a novel compound that induces mitochondrial outer membrane permeabilization by inhibiting antiapoptotic B-cell CLL/lymphoma 2 (Bcl-2) family proteins followed by sequestration of proapoptotic cytochrome c. The new small molecule triggered programmed cell death (early and late apoptosis) through cell cycle arrest in the G2/M phase and caspase-9/3 cleavage in HCT-116 colon cancer cells, confirmed by an array of fluorescence confocal microscopy, cell sorting, and immunoblotting analysis. Furthermore, cell viability studies have verified that the small molecule rendered toxicity to a panel of colon cancer cells (HCT-116, DLD-1, and SW-620), keeping healthy L929 fibroblast cells unharmed. The novel small molecule has the potential to form a new understudied class of mitochondria targeting anticancer agent.

Targeting Mitochondrial Bioenergetics as a Therapeutic Strategy for Chronic Lymphocytic Leukemia

Altered cellular metabolism is considered a hallmark of cancer and is fast becoming an avenue for therapeutic intervention. Mitochondria have recently been viewed as an important cellular compartment that fuels the metabolic demands of cancer cells. Mitochondria are the major source of ATP and metabolites necessary to fulfill the bioenergetics and biosynthetic demands of cancer cells. Furthermore, mitochondria are central to cell death and the main source for generation of reactive oxygen species (ROS). Overall, the growing evidence now suggests that mitochondrial bioenergetics, biogenesis, ROS production, and adaptation to intrinsic oxidative stress are elevated in chronic lymphocytic leukemia (CLL). Hence, recent studies have shown that mitochondrial metabolism could be targeted for cancer therapy. This review focuses the recent advancements in targeting mitochondrial metabolism for the treatment of CLL.