Classification of mitocans, anti-cancer drugs acting on mitochondria

Targeting Mitochondria for Cancer Treatment

There is an increasing accumulation of data on the exceptional importance of mitochondria in the occurrence and treatment of cancer, and in all lines of evidence for such participation, there are both energetic and non-bioenergetic functional features of mitochondria. This analytical review examines three specific features of adaptive mitochondrial changes in several malignant tumors. The first feature is characteristic of solid tumors, whose cells are forced to rebuild their energetics due to the absence of oxygen, namely, to activate the fumarate reductase pathway instead of the traditional succinate oxidase pathway that exists in aerobic conditions. For such a restructuring, the presence of a low-potential quinone is necessary, which cannot ensure the conventional conversion of succinate into fumarate but rather enables the reverse reaction, that is, the conversion of fumarate into succinate. In this scenario, complex I becomes the only generator of energy in mitochondria. The second feature is the increased proliferation in aggressive tumors of the so-called mitochondrial (peripheral) benzodiazepine receptor, also called translocator protein (TSPO) residing in the outer mitochondrial membrane, the function of which in oncogenic transformation stays mysterious. The third feature of tumor cells is the enhanced retention of certain molecules, in particular mitochondrially directed cations similar to rhodamine 123, which allows for the selective accumulation of anticancer drugs in mitochondria. These three features of mitochondria can be targets for the development of an anti-cancer strategy.

Preclinical assessment of MAGMAS inhibitor as a potential therapy for pediatric medulloblastoma

Medulloblastoma, the most common pediatric brain malignancy, has Sonic Hedgehog (SHH) and non-SHH group3 subtypes. MAGMAS (Mitochondrial Associated Granulocyte Macrophage colony-stimulating factor Signaling molecules) encode for mitochondrial import inner membrane translocase subunit and is responsible for translocation of matrix proteins across the inner membrane. We previously reported that a small molecule MAGMAS inhibitor, BT9, decreases cell proliferation, migration, and oxidative phosphorylation in adult glioblastoma cell lines. The aim of our study was to investigate whether the chemotherapeutic effect of BT9 can be extended to pediatric medulloblastoma.

Methods

Multiple in vitro assays were performed using human DAOY (SHH activated tp53 mutant) and D425 (non-SHH group 3) cells. The impact of BT9 on cellular growth, death, migration, invasion, and metabolic activity were quantified using MTT assay, TUNEL staining, scratch wound assay, Matrigel invasion chambers, and seahorse assay, respectively. Survival following 50mg/kg BT9 treatment was assessed in vivo in immunodeficient mice intracranially implanted with D425 cells.

Results

Compared to control, BT9 treatment led to a significant reduction in medulloblastoma cell growth (DAOY, 24hrs IC50: 3.6uM, 48hrs IC50: 2.3uM, 72hrs IC50: 2.1uM; D425 24hrs IC50: 3.4uM, 48hrs IC50: 2.2uM, 72hrs IC50: 2.1uM) and a significant increase in cell death (DAOY, 24hrs p=0.0004, 48hrs p<0.0001; D425, 24hrs p=0.0001, 48hrs p=0.02). In DAOY cells, 3uM BT9 delayed migration, and significantly decreased DAOY and D425 cells invasion (p < 0.0001). Our in vivo study, however, did not extend survival in xenograft mouse model of group3 medulloblastoma compared to vehicle-treated controls.

Conclusions

Our in vitro data showed BT9 antitumor efficacy in DAOY and D425 cell lines suggesting that BT9 may represent a promising targeted therapeutic in pediatric medulloblastoma. These data, however, need to be further validated in animal models.

Mitochondria act as a key regulatory factor in cancer progression: Current concepts on mutations, mitochondrial dynamics, and therapeutic approach

The diversified impacts of mitochondrial function vs. dysfunction have been observed in almost all disease conditions including cancers. Mitochondria play crucial roles in cellular homeostasis and integrity, however, mitochondrial dysfunctions influenced by alterations in the mtDNA can disrupt cellular balance. Many external stimuli or cellular defects that cause cellular integrity abnormalities, also impact mitochondrial functions. Imbalances in mitochondrial activity can initiate and lead to accumulations of genetic mutations and can promote the processes of tumorigenesis, progression, and survival. This comprehensive review summarizes epigenetic and genetic alterations that affect the functionality of the mitochondria, with considerations of cellular metabolism, and as influenced by ethnicity. We have also reviewed recent insights regarding mitochondrial dynamics, miRNAs, exosomes that play pivotal roles in cancer promotion, and the impact of mitochondrial dynamics on immune cell mechanisms. The review also summarizes recent therapeutic approaches targeting mitochondria in anti-cancer treatment strategies.

The long non-coding RNA OTX2-AS1 promotes tumor growth and predicts response to BCL-2 inhibition in medulloblastoma

PURPOSE

Primary brain tumors are a leading cause of cancer-related death in children, and medulloblastoma is the most common malignant pediatric brain tumor. The current molecular characterization of medulloblastoma is mainly based on protein-coding genes, while little is known about the involvement of long non-coding RNAs (lncRNAs). This study aimed to elucidate the role of the lncRNA OTX2-AS1 in medulloblastoma.

METHODS

Analyses of DNA copy number alterations, methylation profiles, and gene expression data were used to characterize molecular alterations of OTX2-AS1 in medulloblastoma tissue samples. In vitro analyses of medulloblastoma cell models and orthotopic in vivo experiments were carried out for functional characterization of OTX2-AS1. High-throughput drug screening was employed to identify pharmacological inhibitors, while proteomics and metabolomics analyses were performed to address potential mechanisms of drug action.

RESULTS

We detected amplification and consecutive overexpression of OTX2 and OTX2-AS1 in a subset of medulloblastomas. In addition, OTX2-AS1 promoter methylation was linked to OTX2-AS1 expression. OTX2-AS1 knockout reduced medulloblastoma cell viability and cell migration in vitro and prolonged survival in the D283 orthotopic medulloblastoma mouse xenograft model. Pharmacological inhibition of BCL-2 suppressed the growth of OTX2-AS1 overexpressing medulloblastoma cells in vitro.

CONCLUSIONS

Our study revealed a pro-tumorigenic role of OTX2-AS1 in medulloblastoma and identified BCL-2 inhibition as a potential therapeutic approach to target OTX2-AS1 overexpressing medulloblastoma cells.

The mechanisms of action of mitochondrial targeting agents in cancer: inhibiting oxidative phosphorylation and inducing apoptosis

The tumor microenvironment affects the structure and metabolic function of mitochondria in tumor cells. This process involves changes in metabolic activity, an increase in the amount of reactive oxygen species (ROS) in tumor cells compared to normal cells, the production of more intracellular free radicals, and the activation of oxidative pathways. From a practical perspective, it is advantageous to develop drugs that target mitochondria for the treatment of malignant tumors. Such drugs can enhance the selectivity of treatments for specific cell groups, minimize toxic effects on normal tissues, and improve combinational treatments. Mitochondrial targeting agents typically rely on small molecule medications (such as synthetic small molecules agents, active ingredients of plants, mitochondrial inhibitors or autophagy inhibitors, and others), modified mitochondrial delivery system agents (such as lipophilic cation modification or combining other molecules to form targeted mitochondrial agents), and a few mitochondrial complex inhibitors. This article will review these compounds in three main areas: oxidative phosphorylation (OXPHOS), changes in ROS levels, and endogenous oxidative and apoptotic processes.

Mitochondrially targeted tamoxifen as anticancer therapy: case series of patients with renal cell carcinoma treated in a phase I/Ib clinical trial

Mitochondrially targeted anticancer drugs (mitocans) that disrupt the energy-producing systems of cancer are emerging as new potential therapeutics. Mitochondrially targeted tamoxifen (MitoTam), an inhibitor of mitochondrial respiration respiratory complex I, is a first-in-class mitocan that was tested in the phase I/Ib MitoTam-01 trial of patients with metastatic cancer. MitoTam exhibited a manageable safety profile and efficacy; among 37% (14/38) of responders, the efficacy was greatest in patients with metastatic renal cell carcinoma (RCC) with a clinical benefit rate of 83% (5/6) of patients. This can be explained by the preferential accumulation of MitoTam in the kidney tissue in preclinical studies. Here we report the mechanism of action and safety profile of MitoTam in a case series of RCC patients. All six patients were males with a median age of 69 years, who had previously received at least three lines of palliative systemic therapy and suffered progressive disease before starting MitoTam. We recorded stable disease in four, partial response in one, and progressive disease (PD) in one patient. The histological subtype matched clear cell RCC (ccRCC) in the five responders and claro-cellular carcinoma with sarcomatoid features in the non-responder. The number of circulating tumor cells (CTCs) was evaluated longitudinally to monitor disease dynamics. Beside the decreased number of CTCs after MitoTam administration, we observed a significant decrease of the mitochondrial network mass in enriched CTCs. Two patients had long-term clinical responses to MitoTam, of 50 and 36 weeks. Both patients discontinued treatment due to adverse events, not PD. Two patients who completed the trial in November 2019 and May 2020 are still alive without subsequent anticancer therapy. The toxicity of MitoTam increased with the dosage but was manageable. The efficacy of MitoTam in pretreated ccRCC patients is linked to the novel mechanism of action of this first-in-class mitochondrially targeted drug.

Z-ligustilide preferentially caused mitochondrial dysfunction in AML HL-60 cells by activating nuclear receptors NUR77 and NOR1

BACKGROUND

Nuclear receptors NUR77 and NOR1 were identified as critical targets in acute myeloid leukemia (AML) therapy. Previously, we showed that Z-ligustilide (Z-LIG) selectively targeted AML by restoring NUR77 and NOR1. However, its downstream mechanisms are yet to be elucidated.

METHODS

SRB staining assay was used to measure cell viability. Cell apoptosis, mitochondrial membrane potential and mitochondrial reactive oxygen species were analyzed using flow cytometry. The potential targets of Z-LIG in AML HL-60 cells were evaluated by RNA sequencing. Changes in RNA levels were measured using quantitative RT-qPCR and western blot analysis was used to detect the expression of proteins.

RESULTS

Z-LIG preferentially induced mitochondrial dysfunction in HL-60 cells compared with 293T cells. Furthermore, RNA sequencing revealed that mitochondrial transcription and translation might be potential Z-LIG targets inhibiting HL-60 cells. NUR77/NOR1 overexpression significantly reduced the mitochondrial ATP and mitochondrial membrane potential and increased mitochondrial reactive oxygen species in HL-60 cells but not in 293T cells. Moreover, Z-LIG induced mitochondrial dysfunction by restoring NUR77 and NOR1 in HL-60 cells. Compared with HL-60 cells, the apoptosis-inducing activities of NUR77/NOR1 and Z-LIG were significantly reduced in HL-60 ρ0 cells depleted in mitochondrial DNA (mt-DNA). Moreover, NUR77/NOR1 and Z-LIG downregulated mitochondrial transcription and translation related proteins in HL-60 cells. Notably, Z-LIG remarkably reduced mitochondrial ATP in primary AML cells and showed anti-AML activity in mouse models of human AML.

CONCLUSIONS

Collectively, our findings suggested that Z-LIG selectively induces mitochondrial dysfunction in AML HL-60 cells by restoring NUR77 and NOR1, a process associated with interference in mtDNA transcription.

MitoTam-01 Trial: Mitochondrial Targeting as Plausible Approach to Cancer Therapy. Comment on Yap et al. Complex I Inhibitor of Oxidative Phosphorylation in Advanced Solid Tumors and Acute Myeloid Leukemia: Phase I Trials. Nat. Med. 2023, 29, 115-126

A recent paper published in Nature Medicine reported on the Phase I clinical trial of a mitochondria-targeting anti-cancer agent IACS-01059 in patients with acute myeloid leukemia (AML) and solid tumors [...].

LRRK2 Knockout Confers Resistance in HEK-293 Cells to Rotenone-Induced Oxidative Stress, Mitochondrial Damage, and Apoptosis

Leucine-rich repeat kinase 2 (LRRK2) has been linked to dopaminergic neuronal vulnerability to oxidative stress (OS), mitochondrial impairment, and increased cell death in idiopathic and familial Parkinson's disease (PD). However, how exactly this kinase participates in the OS-mitochondria-apoptosis connection is still unknown. We used clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 LRRK2 knockout (KO) in the human embryonic kidney cell line 293 (HEK-293) to evaluate the cellular response to the mitochondrial inhibitor complex I rotenone (ROT), a well-known OS and cell death inducer. We report successful knockout of the LRRK2 gene in HEK-293 cells using CRISPR editing (ICE, approximately 60%) and flow cytometry (81%) analyses. We found that HEK-293 LRRK2 WT cells exposed to rotenone (ROT, 50 μM) resulted in a significant increase in intracellular reactive oxygen species (ROS, +7400%); oxidized DJ-1-Cys¹⁰⁶-SO₃ (+52%); phosphorylation of LRRK2 (+70%) and c-JUN (+171%); enhanced expression of tumor protein (TP53, +2000%), p53 upregulated modulator of apoptosis (PUMA, +1950%), and Parkin (PRKN, +22%); activation of caspase 3 (CASP3, +8000%), DNA fragmentation (+35%) and decreased mitochondrial membrane potential (ΔΨm, -58%) and PTEN induced putative kinase 1 (PINK1, -49%) when compared to untreated cells. The translocation of the cytoplasmic fission protein dynamin-related Protein 1 (DRP1) to mitochondria was also observed by colocalization with translocase of the outer membrane 20 (TOM20). Outstandingly, HEK-293 LRRK2 KO cells treated with ROT showed unaltered OS and apoptosis markers. We conclude that loss of LRRK2 causes HEK-293 to be resistant to ROT-induced OS, mitochondrial damage, and apoptosis in vitro. Our data support the hypothesis that LRRK2 acts as a proapoptotic kinase by regulating mitochondrial proteins (e.g., PRKN, PINK1, DRP1, and PUMA), transcription factors (e.g., c-JUN and TP53), and CASP3 in cells under stress conditions. Taken together, these observations suggest that LRRK2 is an important kinase in the pathogenesis of PD.

An Update on Tamoxifen and the Chemo-Preventive Potential of Vitamin E in Breast Cancer Management

Breast cancer (BC) is the most common female cancer in terms of incidence and mortality worldwide. Tamoxifen (Nolvadex) is a widely prescribed, oral anti-estrogen drug for the hormonal treatment of estrogen-receptor-positive BC, which represents 70% of all BC subtypes. This review assesses the current knowledge on the molecular pharmacology of tamoxifen in terms of its anticancer and chemo-preventive actions. Due to the importance of vitamin E compounds, which are widely taken as a supplementary dietary component, the review focuses only on the potential importance of vitamin E in BC chemo-prevention. The chemo-preventive and onco-protective effects of tamoxifen combined with the potential effects of vitamin E can alter the anticancer actions of tamoxifen. Therefore, methods involving an individually designed, nutritional intervention for patients with BC warrant further consideration. These data are of great importance for tamoxifen chemo-prevention strategies in future epidemiological studies.

Asiatic acid as a leading structure for derivatives combining sub-nanomolar cytotoxicity, high selectivity, and the ability to overcome drug resistance in human preclinical tumor models

Amides and rhodamine B conjugates of different pentacyclic triterpene acids have been shown outstanding cytotoxicity for human tumor cells. Starting from asiatic acid, a new rhodamine B hybrid has been synthesized, and its cytotoxic activity was investigated employing several human tumor cell lines (A375 (melanoma), HT29 (colorectal carcinoma), MCF7 (breast adenocarcinoma), A2780 (ovarian carcinoma), HeLa (cervical carcinoma), (NIH 3T3 (non-malignant murine fibroblasts). For these conjugates of this kind it has been established that the spacer attached to the carboxyl group at ring E governs the magnitude of the cytotoxicity. These asiatic acid - rhodamine B conjugates were highly cytotoxic for human tumor cell lines but also selective. For example, 7, an acetylated homopiperazinyl spacered rhodamine B conjugate, held an EC₅₀ = 0.8 nM for A2780 ovarian carcinoma cells. Additional staining experiments showed the rhodamine B conjugates to act as mitocans and to effect apoptosis. In further tests using 3D spheroid models of colorectal- and mamma carcinoma, 7 demonstrated activity in the lower nanomolar range and the ability to overcome resistance to clinically used standard chemotherapeutic drugs. Therefore 7 induces cytotoxic effects leading to an equal response in the chemotherapy of both sensitive and resistant tumor models. Analyses of mitochondrial function and glycolysis and respiration derived ATP production confirmed compound 7 to act as mitocan but also revealed a rapid perturbation of the cellular energy metabolism as the primary mechanism of action, which is completely different to conventional chemotherapeutic drugs and thereby explains the ability of compound 7 to overcome chemotherapeutic drug resistance.

Promising Strategy of mPTP Modulation in Cancer Therapy: An Emerging Progress and Future Insight

Cancer has been progressively a major global health concern. With this developing global concern, cancer determent is one of the most significant public health challenges of this era. To date, the scientific community undoubtedly highlights mitochondrial dysfunction as a hallmark of cancer cells. Permeabilization of the mitochondrial membranes has been implicated as the most considerable footprint in apoptosis-mediated cancer cell death. Under the condition of mitochondrial calcium overload, exclusively mediated by oxidative stress, an opening of a nonspecific channel with a well-defined diameter in mitochondrial membrane allows free exchange between the mitochondrial matrix and the extra mitochondrial cytosol of solutes and proteins up to 1.5 kDa. Such a channel/nonspecific pore is recognized as the mitochondrial permeability transition pore (mPTP). mPTP has been established for regulating apoptosis-mediated cancer cell death. It has been evident that mPTP is critically linked with the glycolytic enzyme hexokinase II to defend cellular death and reduce cytochrome c release. However, elevated mitochondrial Ca2+ loading, oxidative stress, and mitochondrial depolarization are critical factors leading to mPTP opening/activation. Although the exact mechanism underlying mPTP-mediated cell death remains elusive, mPTP-mediated apoptosis machinery has been considered as an important clamp and plays a critical role in the pathogenesis of several types of cancers. In this review, we focus on structure and regulation of the mPTP complex-mediated apoptosis mechanisms and follow with a comprehensive discussion addressing the development of novel mPTP-targeting drugs/molecules in cancer treatment.

Mitochondriotropic Derivative of Ethyl Ferulate, a Dietary Phenylpropanoid, Exhibits Enhanced Cytotoxicity in Cancer Cells via Mitochondrial Superoxide-Mediated Activation of JNK and AKT Signalling

Specific targeting of anti-cancer drugs to mitochondria is an emerging strategy to enhance cancer cell killing whilst simultaneously overcoming the problem of drug resistance, low bioavailability and limited clinical success of natural products. We have synthesized a mitochondria targeted derivative of Ethyl Ferulate (EF, a naturally occurring ester of ferulic acid), by conjugating it with triphenylphosphonium ion and compared its cytotoxicity with the parent molecule. Mito-Ethyl Ferulate (M-EF) was found to be more potent than EF (~ 400-fold) in inhibiting the growth of A549 and MCF-7 cells and suppressing the clonogenic potential of A549 cells. Notably, M-EF did not induce any cytotoxicity in normal cells (mouse normal fibroblast cells) up to a concentration of 25 μM. Furthermore, M-EF treatment induced significantly higher cell death in MCF-7 and A549 cells, as compared to EF via induction of apoptosis. M-EF treatment increased mitochondrial superoxide production and induced mitochondrial DNA damage and phosphorylation of JNK and AKT in A549 cells. Furthermore, M-EF induced increase in mitochondrial superoxide production and cytotoxicity was attenuated on pre-treatment with mitochondria-targeted antioxidant (mitoTEMPO) indicating the involvement of mitochondrial ROS in the cytotoxic effects of M-EF. Finally, in silico prediction revealed putative mitochondrial targets of M-EF which are known to regulate mitochondrial ROS and cell viability. In conclusion, the improved cytotoxic efficacy of M-EF exemplifies the use of mitochondria-specific drug delivery in future development of natural product based mitochondrial pharmacology.

Genetic mutations affecting mitochondrial function in cancer drug resistance

Mitochondria are organelles that serve as a central hub for physiological processes in eukaryotes, including production of ATP, regulation of calcium dependent signaling, generation of ROS, and regulation of apoptosis. Cancer cells undergo metabolic reprogramming in an effort to support their increasing requirements for cell survival, growth, and proliferation, and mitochondria have primary roles in these processes. Because of their central function in survival of cancer cells and drug resistance, mitochondria are an important target in cancer therapy and many drugs targeting mitochondria that target the TCA cycle, apoptosis, metabolic pathway, and generation of ROS have been developed. Continued use of mitochondrial-targeting drugs can lead to resistance due to development of new somatic mutations. Use of drugs is limited due to these mutations, which have been detected in mitochondrial proteins. In this review, we will focus on genetic mutations in mitochondrial target proteins and their function in induction of drug-resistance.

Plant-derived natural products and combination therapy in liver cancer

Liver cancer is one of the malignant cancers globally and seriously endangers human health because of its high morbidity and mortality. Plant-derived natural products have been evaluated as potential anticancer drugs due to low side effects and high anti-tumor efficacy. However, plant-derived natural products also have defects of poor solubility and cumbersome extraction process. In recent years, a growing numbers of plant derived natural products have been used in combination therapy of liver cancer with conventional chemotherapeutic agents, which has improved clinical efficacy through multiple mechanisms, including inhibition of tumor growth, induction of apoptosis, suppression of angiogenesis, enhancement of immunity, reversal of multiple drug resistance and reduction of side effects. The therapeutic effects and mechanisms of plant-derived natural products and combination therapy on liver cancer are reviewed to provide references for developing anti-liver-cancer strategies with high efficacy and low side effects.

Development of Spectral Nano-Flow Cytometry for High-Throughput Multiparameter Analysis of Individual Biological Nanoparticles

Correlated analysis of multiple biochemical parameters at the single-particle level and in a high-throughput manner is essential for insights into the diversity and functions of biological nanoparticles (BNPs), such as bacteria and subcellular organelles. To meet this challenge, we developed a highly sensitive spectral nano-flow cytometer (S-nFCM) by integrating a spectral recording module to a laboratory-built nFCM that is 4-6 orders of magnitude more sensitive in side scattering detection and 1-2 orders of magnitude more sensitive in fluorescence detection than conventional flow cytometers. An electron-multiplying charge-coupled device (EMCCD) was used to acquire the full fluorescence spectra of single BNPs upon holographic grating dispersion. Up to 10,000 spectra can be collected in 1 min with 2.1 nm resolution. The precision, linearity, and sensitivity were examined. Complete discernment of single influenza viruses against the background signal, discrimination of different strains of marine cyanobacteria in a mixed sample based on their spectral properties of natural fluorescence, classification of bacterial categories exhibiting different patterns of antigen expression, and multiparameter analysis of single mitochondria for drug discovery were successfully demonstrated.

Mitochondrially targeted tamoxifen in patients with metastatic solid tumours: an open-label, phase I/Ib single-centre trial

Background

Mitochondria present an emerging target for cancer treatment. We have investigated the effect of mitochondrially targeted tamoxifen (MitoTam), a first-in-class anti-cancer agent, in patients with solid metastatic tumours.

Methods

MitoTam was tested in an open-label, single-centre (Department of Oncology, General Faculty Hospital, Charles University, Czech Republic), phase I/Ib trial in metastatic patients with various malignancies and terminated oncological therapies. In total, 75 patients were enrolled between May 23, 2018 and July 22, 2020. Phase I evaluated escalating doses of MitoTam in two therapeutic regimens using the 3 + 3 design to establish drug safety and maximum tolerated dose (MTD). In phase Ib, three dosing regimens were applied over 8 and 6 weeks to evaluate long-term toxicity of MitoTam as the primary objective and its anti-cancer effect as a secondary objective. This trial was registered with the European Medicines Agency under EudraCT 2017-004441-25.

Findings

In total, 37 patients were enrolled into phase I and 38 into phase Ib. In phase I, the initial application of MitoTam via peripheral vein indicated high risk of thrombophlebitis, which was avoided by central vein administration. The highest dose with acceptable side effects was 5.0 mg/kg. The prevailing adverse effects (AEs) in phase I were neutropenia (30%), anaemia (30%) and fever/hyperthermia (30%), and in phase Ib fever/hyperthermia (58%) together with anaemia (26%) and neutropenia (16%). Serious AEs were mostly related to thromboembolic (TE) complications that affected 5% and 13% of patients in phase I and Ib, respectively. The only statistically significant AE related to MitoTam treatment was anaemia in phase Ib (p = 0.004). Of the tested regimens weekly dosing with 3.0 mg/kg for 6 weeks afforded the best safety profile with almost all being grade 1 (G1) AEs. Altogether, five fatalities occurred during the study, two of them meeting criteria for Suspected Unexpected Serious Adverse Events Reporting (SUSAR) (G4 thrombocytopenia and G5 stroke). MitoTam showed benefit evaluated as clinical benefit rate (CBR) in 37% patients with the largest effect in renal cell carcinoma (RCC) where four out of six patients reached disease stabilisation (SD), one reached partial response (PR) so that in total, five out of six (83%) patients showed CBR.

Interpretation

In this study, the MTD was established as 5.0 mg/kg and the recommended dose of MitoTam as 3.0 mg/kg given once per week via central vein with recommended preventive anti-coagulation therapy. The prevailing toxicity included haematological AEs, hyperthermia/fever and TE complications. One fatal stroke and non-fatal G4 thrombocytopenia were recorded. MitoTam showed high efficacy against RCC.

Funding

Smart Brain Ltd.

Translation

For the Czech translation of the abstract see Supplementary Materials section.

Phytochemical Targeting of Mitochondria for Breast Cancer Chemoprevention, Therapy, and Sensitization

Breast cancer is a common and deadly disease that causes tremendous physical, emotional, and financial burden on patients and society. Early-stage breast cancer and less aggressive subtypes have promising prognosis for patients, but in aggressive subtypes, and as cancers progress, treatment options and responses diminish, dramatically decreasing survival. Plants are nutritionally rich and biologically diverse organisms containing thousands of metabolites, some of which have chemopreventive, therapeutic, and sensitizing properties, providing a rich source for drug discovery. In this study we review the current landscape of breast cancer with a central focus on the potential role of phytochemicals for treatment, management, and disease prevention. We discuss the relevance of phytochemical targeting of mitochondria for improved anti-breast cancer efficacy. We highlight current applications of phytochemicals and derivative structures that display anti-cancer properties and modulate cancer mitochondria, while describing future applicability and identifying areas of promise.

Developing Bi-Gold Compound BGC2a to Target Mitochondria for the Elimination of Cancer Cells

Reactive oxygen species (ROS) homeostasis and mitochondrial metabolism are critical for the survival of cancer cells, including cancer stem cells (CSCs), which often cause drug resistance and cancer relapse. Auranofin is a mono-gold anti-rheumatic drug, and it has been repurposed as an anticancer agent working by the induction of both ROS increase and mitochondrial dysfunction. Hypothetically, increasing auranofin’s positive charges via incorporating more gold atoms to enhance its mitochondria-targeting capacity could enhance its anti-cancer efficacy. Hence, in this work, both mono-gold and bi-gold compounds were designed and evaluated to test our hypothesis. The results showed that bi-gold compounds generally suppressed cancer cells proliferation better than their mono-gold counterparts. The most potent compound, BGC2a, substantially inhibited the antioxidant enzyme TrxR and increased the cellular ROS. BGC2a induced cell apoptosis, which could not be reversed by the antioxidant agent vitamin C, implying that the ROS induced by TrxR inhibition might not be the decisive cause of cell death. As expected, a significant proportion of BGC2a accumulated within mitochondria, likely contributing to mitochondrial dysfunction, which was further confirmed by measuring oxygen consumption rate, mitochondrial membrane potential, and ATP production. Moreover, BGC2a inhibited colony formation and reduced stem-like side population (SP) cells of A549. Finally, the compound effectively suppressed the tumor growth of both A549 and PANC-1 xenografts. Our study showed that mitochondrial disturbance may be gold-based compounds’ major lethal factor in eradicating cancer cells, providing a new approach to developing potent gold-based anti-cancer drugs by increasing mitochondria-targeting capacity.

Polycationic peptide R7-G-Aβ25-35 selectively induces cell death in leukemia Jurkat T cells through speedy mitochondrial depolarization, and CASPASE-3 -independent mechanism

Background

Methods

Results

Conclusion

•

Polycationic arginine (R) residue bound Aβ25-35 peptide is cytotoxic to Jurkat cells.

•

R⁷-G-Aβ_25-35 is more effective killing leukemia cells than Aβ25-35-G-R⁷.

•

R⁷-G-Aβ_25-35 induces alteration of cell metabolism, and reduces cell proliferation.

•

R⁷-G-Aβ_25-35 provokes loss of ΔΨ_m and produces high amount of ROS.

•

R⁷-G-Aβ_25-35 is harmless to normal proliferative mesenchymal stromal cells.

Mitochondrial Genetic and Epigenetic Regulations in Cancer: Therapeutic Potential

Mitochondria are dynamic organelles managing crucial processes of cellular metabolism and bioenergetics. Enabling rapid cellular adaptation to altered endogenous and exogenous environments, mitochondria play an important role in many pathophysiological states, including cancer. Being under the control of mitochondrial and nuclear DNA (mtDNA and nDNA), mitochondria adjust their activity and biogenesis to cell demands. In cancer, numerous mutations in mtDNA have been detected, which do not inactivate mitochondrial functions but rather alter energy metabolism to support cancer cell growth. Increasing evidence suggests that mtDNA mutations, mtDNA epigenetics and miRNA regulations dynamically modify signalling pathways in an altered microenvironment, resulting in cancer initiation and progression and aberrant therapy response. In this review, we discuss mitochondria as organelles importantly involved in tumorigenesis and anti-cancer therapy response. Tumour treatment unresponsiveness still represents a serious drawback in current drug therapies. Therefore, studying aspects related to genetic and epigenetic control of mitochondria can open a new field for understanding cancer therapy response. The urgency of finding new therapeutic regimens with better treatment outcomes underlines the targeting of mitochondria as a suitable candidate with new therapeutic potential. Understanding the role of mitochondria and their regulation in cancer development, progression and treatment is essential for the development of new safe and effective mitochondria-based therapeutic regimens.

TPEN selectively eliminates lymphoblastic B cells from bone marrow pediatric acute lymphoblastic leukemia patients

B-cell acute lymphoblastic leukemia (B-ALL) is a hematologic disorder characterized by the abnormal proliferation and accumulation of immature B-lymphoblasts arrested at various stages of differentiation. Despite advances in treatment, a significant percentage of pediatric patients with precursor B-ALL still relapse. Therefore, alternative therapies are needed to improve the cure rates for pediatric patients. TPEN (N, N, N', N'-tetrakis(2-pyridylmethyl)-ethylenediamine) is a pro-oxidant agent capable of selectively inducing apoptosis in leukemia cell lines. Consequently, it has been suggested that TPEN could be a potential agent for oxidative therapy. However, it is not yet known whether TPEN can selectively destroy leukemia cells in a more disease-like model, for example, the bloodstream and bone marrow (BM), ex vivo. This investigation is an extension of a previous study that dealt with the effect of TPEN on ex vivo isolated/purified refractory B-ALL cells. Here, we evaluated the effect of TPEN on whole BM from nonleukemic patients (control) or pediatric patients diagnosed with de novo B-ALL or refractory B-ALL cells by analyzing the hematopoietic cell lineage marker CD34/CD19. Although TPEN was innocuous to nonleukemic BM (n = 3), we found that TPEN significantly induced apoptosis in de novo (n = 5) and refractory B-ALL (n = 6) leukemic cell populations. Moreover, TPEN significantly increased the counts of cells positive for the oxidation of the stress sensor protein DJ-1, a sign of the formation of H₂O₂, and significantly increased the counts of cells positive for the pro-apoptotic proteins TP53, PUMA, and CASPASE-3 (CASP-3), indicative of apoptosis, in B-ALL cells. We demonstrate that TPEN selectively eliminates B-ALL cells (CD34 + /CD19 +) but no other cell populations in BM (CD34 + /CD19-; CD34-/CD19 + ; CD34-/CD19-) independent of age, diagnosis status (de novo or refractory), sex, karyotype, or immunophenotype. Understanding TPEN-induced cell death in leukemia cells provides insight into more effective therapeutic oxidation-inducing anticancer agents.

Мitochondrial therapy of melanoma B16/F10, pathophysiological parameters of tumor regression

The aim is to evaluate the pathophysiological parameters of the efficacy of liver mitochondrial transplantation in animals with B16/F10 melanoma. Materials and methods. In our experiment we used female and male mice of BALB/c Nude strain (n=28). Experimental groups were as follows: the reference group (n=14) with B16/ F10 melanoma; the main group (n=14) with B16/F10 melanoma + mitochondrial therapy (MC therapy). Statistical analysis of results was carried out with the Statistica 10.0 software. Results. The subcutaneous tumor in the mice of both sexes became detectable on day 5 from the time of the tumor inoculation, and the regressive effect produced by MC therapy was recorded in the males beginning with day 8 of the tumor growth. At the end of the experiment, on day 22, the difference in the average volumes of the tumor node was reported to be 3.2 times, i.e. a significant inhibition of the tumor growth in the group of the males with MC therapy was revealed. In the females on day 5 of the tumor growth, differences in the volume of the tumor focus between the reference group and the group with MC therapy were not recorded, however, a statistically significant difference was found in the sex-related comparison of the groups of the animals with MC therapy. It was determined that in the females with MC therapy, the area of the tumor spot during that period (5 days) was 1.4 times (p<0.05) less than that in the corresponding group of the males. On day 8, in the females completed MC therapy, the tumor has not yet concentrated into a solid structure, but remained as a flat tumor entity, and only by day 12 the tumor has formed from a flat structure into a volumetric tumor type. As a result, by the end of the experiment, on day 22, smaller volumes of the tumor nodes remained in the group of females treated with MC therapy, and the difference with the reference group was 2.7 times (p<0.05). Conclusion. Thus, within the framework of the experiment, it has been found that the application of mitochondrial therapy using allogeneic liver mitochondria in the BALB/c Nude mice with B16/F10 melanoma retards the tumor growth in the mice of both sexes.

Targeting Energy Metabolism in Cancer Treatment

Cancer is the second most common cause of death worldwide after cardiovascular diseases. The development of molecular and biochemical techniques has expanded the knowledge of changes occurring in specific metabolic pathways of cancer cells. Increased aerobic glycolysis, the promotion of anaplerotic responses, and especially the dependence of cells on glutamine and fatty acid metabolism have become subjects of study. Despite many cancer treatment strategies, many patients with neoplastic diseases cannot be completely cured due to the development of resistance in cancer cells to currently used therapeutic approaches. It is now becoming a priority to develop new treatment strategies that are highly effective and have few side effects. In this review, we present the current knowledge of the enzymes involved in the different steps of glycolysis, the Krebs cycle, and the pentose phosphate pathway, and possible targeted therapies. The review also focuses on presenting the differences between cancer cells and normal cells in terms of metabolic phenotype. Knowledge of cancer cell metabolism is constantly evolving, and further research is needed to develop new strategies for anti-cancer therapies.

Recent Advances in Mitochondrial Diseases: from Molecular Insights to Therapeutic Perspectives

Mitochondria are double-membraned cytoplasmic organelles that are responsible for the production of energy in eukaryotic cells. The process is completed through oxidative phosphorylation (OXPHOS) by the respiratory chain (RC) in mitochondria. Thousands of mitochondria may be present in each cell, depending on the function of that cell. Primary mitochondria disorder (PMD) is a clinically heterogeneous disease associated with germline mutations in mitochondrial DNA (mtDNA) and/or nuclear DNA (nDNA) genes, and impairs mitochondrial structure and function. Mitochondrial dysfunction can be detected in early childhood and may be severe, progressive and often multi-systemic, involving a wide range of organs. Understanding epigenetic factors and pathways mutations can help pave the way for developing an effective cure. However, the lack of information about the disease (including age of onset, symptoms, clinical phenotype, morbidity and mortality), the limits of current preclinical models and the wide range of phenotypic presentations hamper the development of effective medicines. Although new therapeutic approaches have been introduced with encouraging preclinical and clinical outcomes, there is no definitive cure for PMD. This review highlights recent advances, particularly in children, in terms of etiology, pathophysiology, clinical diagnosis, molecular pathways and epigenetic alterations. Current therapeutic approaches, future advances and proposed new therapeutic plans will also be discussed.

In Vitro Effects of Mitochondria-Targeted Antioxidants in a Small-Cell Carcinoma of the Ovary of Hypercalcemic Type and in Type 1 and Type 2 Endometrial Cancer

Small-cell carcinoma of the ovary of hypercalcemic type (SCCOHT) and endometrial cancer from type 1 and type 2 are gynecological tumors that affect women worldwide. The treatment encompasses the use of cytotoxic drugs that are nonspecific and inefficient. “Mitocans”, a family of drugs that specifically target tumor cells’ mitochondria, might be a solution, as they conjugate compounds, such as antioxidants, with carriers, such as lipophilic cations, that direct them to the mitochondria. In this study, caffeic acid was conjugated with triphenylphosphonium (TPP), 4-picolinium, or isoquinolinium, forming 3 new compounds (Mito6_TPP, Mito6_picol., and Mito6_isoq.) that were tested on ovarian (COV434) and endometrial (Hec50co and Ishikawa) cancer cells. The results of MTT and neutral red assays suggested a time- and concentration-dependent decrease in cell viability in all tumor cell lines. The presence of apoptosis was indicated by the Giemsa and Höechst staining and by the decrease in mitochondrial membrane potential. The measurement of intracellular reactive oxygen species demonstrated the antioxidant properties of these compounds, which might be related to cell death. Generally, Mito6_TPP was more active at lower concentrations than Mito6_picol. or Mito6_isoq., but was accompanied by more cytotoxic effects, as shown by the lactate dehydrogenase release. Non-tumorous cells (HFF-1) showed no changes after treatment. This study assessed the potential of these compounds as anticancer agents, although further investigation is needed.

Potential-Independent Intracellular Drug Delivery and Mitochondrial Targeting

In this study, two types of the fluoroamphiphile analogs were synthesized and self-assembled into the "core-shell" micellar nanocarriers for intracellular delivery and organelle targeting. Using the fluorescent dyes or vitamin E succinate as the cargo, the drug delivery and targeting capabilities of the fluoroamphiphiles and their micelles were evaluated in the cell lines, tumor cell spheroids, and tumor-bearing mice. The "core-fluorinated" micelles exhibited favorable physicochemical properties and improved the cellular uptake of the cargo by around 20 times compared to their "shell-fluorinated" counterparts. The results also indicated that the core-fluorinated micelles underwent an efficient clathrin-mediated endocytosis and a rapid endosomal escape thereafter. Interestingly, the internalized fluoroamphiphile micelles preferentially accumulated in mitochondria, by which the efficacy of the loaded vitamin E succinate was boosted both in vitro and in vivo. Unlike the popularly used cationic mitochondrial targeting ligands, as a charge-neutral nanocarrier, the fluoroamphiphiles' mitochondrial targeting was potential independent. The mechanism study suggested that the strong binding affinity with the phospholipids, particularly the cardiolipin, played an important role in the fluoroamphiphiles' mitochondrial targeting. These charge-neutral fluoroamphiphiles might have great potential to be a simple and reliable tool for intracellular drug delivery and mitochondrial targeting.

Straightforward access to novel mitochondriotropics derived from 2-arylethanol as potent and selective antiproliferative agents

The necessity for developing novel cytostatic agents with improved activities and reduced side-effects to tackle cancer prompted us to investigate mitochondria-targeted compounds, an approach that is gaining attention for the selective transportation of cytotoxic agents. We envisioned the possibility of conjugating a phenethyl alcohol motif, decorated with a series of phenol-based substituents on the aryl moiety, with a triphenyl phosphonium scaffold (a mitochondria-directed vector), through a hydrocarbon chain of different lengths. Thus, such compounds that incorporate the phenethyl skeleton can be considered as masked phenolic compounds derived from relevant natural counterparts found in olive tree (e.g. tyrosol, hydroxytyrosol). Title compounds exhibited very strong in vitro antiproliferative activities against the panel of six human tumor cell lines tested, with GI₅₀ values ranging from the nanomolar (0.026 ± 0.010 μM for 36) to the submicromolar range in most of the cases; this represents an improvement of up to 350-fold compared to classical chemotherapeutic agents, like 5-fluorouracil or cisplatin. Interestingly, decrease in the linker length led to an increase of GI₅₀ values against non-tumor cells, thus allowing a remarkable improvement of selectivity (SI up to 269). The very promising antiproliferative activities prompted us to further investigate their behaviour against multidrug resistant cell lines (MDR). The results indicated a reduced sensitivity of the multidrug resistant cells to compounds, probably due to P-gp-mediated efflux of these antiproliferative agents. Interestingly, activities were completely restored to the same levels by co-administration of tariquidar, a well-known inhibitor of P-gp. Flow cytometry analysis on sensitive cell lines revealed a decrease in the percentage of cells in G1 phase accompanied by increase in S and G2/M phases. In addition, a significant increase in subG1 area, was observed. These results are compatible with the necrotic and apoptotic cell death detected in the Annexin V assay, and with the depolarization of the mitochondria membrane. Thus, the new mitochondriotropic agents reported herein can be considered as promising antiproliferative agents, endowed with remarkable potency and selectivity, including MDR cells, upon co-administration with a pump-efflux inhibitor.

Mitochondrion-Targeting PEGylated BODIPY Dyes for Near-Infrared Cell Imaging and Photodynamic Therapy

A series of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene-based photosensitizers (AmBXI, X = H, M, Br) featuring a cationic mitochondrion-targeting group and near-infrared (NIR) absorption was synthesized. After extending the photosensitizers’ π–π conjugation via Knoevenagel...

Alterations in sphingolipid composition and mitochondrial bioenergetics represent synergistic therapeutic vulnerabilities linked to multidrug resistance in leukemia

Modifications in sphingolipid (SL) metabolism and mitochondrial bioenergetics are key factors implicated in cancer cell response to chemotherapy, including chemotherapy resistance. In the present work, we utilized acute myeloid leukemia (AML) cell lines, selected to be refractory to various chemotherapeutics, to explore the interplay between SL metabolism and mitochondrial biology supportive of multidrug resistance (MDR). In agreement with previous findings in cytarabine or daunorubicin resistant AML cells, relative to chemosensitive wildtype controls, HL-60 cells refractory to vincristine (HL60/VCR) presented with alterations in SL enzyme expression and lipidome composition. Such changes were typified by upregulated expression of various ceramide detoxifying enzymes, as well as corresponding shifts in ceramide, glucosylceramide, and sphingomyelin (SM) molecular species. With respect to mitochondria, despite consistent increases in both basal respiration and maximal respiratory capacity, direct interrogation of the oxidative phosphorylation (OXPHOS) system revealed intrinsic deficiencies in HL60/VCR, as well as across multiple MDR model systems. Based on the apparent requirement for augmented SL and mitochondrial flux to support the MDR phenotype, we explored a combinatorial therapeutic paradigm designed to target each pathway. Remarkably, despite minimal cytotoxicity in peripheral blood mononuclear cells (PBMC), co-targeting SL metabolism, and respiratory complex I (CI) induced synergistic cytotoxicity consistently across multiple MDR leukemia models. Together, these data underscore the intimate connection between cellular sphingolipids and mitochondrial metabolism and suggest that pharmacological intervention across both pathways may represent a novel treatment strategy against MDR.

Gold(I) Complexes Bearing Alkylated 1,3,5-Triaza-7-phosphaadamantane Ligands as Thermoresponsive Anticancer Agents in Human Colon Cells

Overheating can affect solubility or lipophilicity, among other properties, of some anticancer drugs. These temperature-dependent changes can improve efficiency and selectivity of the drugs, since they may affect their bioavailability, diffusion through cell membrane or activity. One recent approach to create thermosensitive molecules is the incorporation of fluorine atoms in the chemical structure, since fluor can tune some chemical properties such as binding affinity. Herein we report the anticancer effect of gold derivatives with phosphanes derived from 1,3,5-triaza-7-phosphaadamantane (PTA) with long hydrocarbon chains and the homologous fluorinated chains. Besides, we analysed the influence of temperature in the cytotoxic effect. The studied gold(I) complexes with phosphanes derived from PTA showed antiproliferative effect on human colon carcinoma cells (Caco-2/TC7 cell line), probably by inhibiting cellular TrxR causing a dysfunction in the intracellular redox state. In addition, the cell cycle was altered by the activation of p53, and the complexes produce apoptosis through mitochondrial depolarization and the consequent activation of caspase-3. Furthermore, the results suggest that this cytotoxic effect is enhanced by hyperthermia and the presence of polyfluorinated chains.

Quercetin increases mitochondrial proteins (VDAC and SDH) and downmodulates AXL and PIM-1 tyrosine kinase receptors in NRAS melanoma cells

Melanoma is a type of skin cancer with low survival rates after it has metastasized. In order to find molecular differences that could represent targets of quercetin in anti-melanoma activity, we have chosen SKMEL-103 and SKMEL-28 melanoma cells and human melanocytes as models. Firstly, we observed that quercetin was able in reducing SKMEL-103 cell viability, but not in SKMEL-28. Besides that, quercetin treatment caused inhibition of AXL in both cell lines, but upregulation of PIM-1 in SKMEL-28 and downregulation in SKMEL-103. Moreover, HIF-1 alpha expression decreased in both cell lines. Interestingly, quercetin was more effective against SKMEL-103 than kinases inhibitors, such as Imatinib, Temsirolimus, U0126, and Erlotinib. Interestingly, we observed that while the levels of succinate dehydrogenase and voltage-dependent anion channel increased in SKMEL-103, both proteins were downregulated in SKMEL-28 after quercetin's treatment. Furthermore, AKT, AXL, PIM-1, ABL kinases were much more active and chaperones HSP90, HSP70 and GAPDH were highly expressed in SKMEL-103 cells in comparison with melanocytes. Our findings indicate, for the first time, that the efficacy of quercetin to kill melanoma cells depends on its ability in inhibiting tyrosine kinase and upregulating mitochondrial proteins, at least when SKMEL-103 and SKMEL-28 cells response were compared.

Molecular docking and simulation studies of phytocompounds derived from Centella asiatica and Andrographis paniculata against hexokinase II as mitocan agents

Hexokinase II (HK2), a glycolytic enzyme is commonly overexpressed in most cancer types. The overexpression of HK2 is reported to promote the survival of cancer cells by facilitating the constant ATP generation and protecting the cancer cell against apoptotic cell death. Hence, HK2 is considered as potential target of many mitochondria targeting anticancerous agents (referred to as mitocans). Most of the existing mitocans are synthetic and hence such compounds are observed to exhibit adverse effects, witnessed through many experimental outcomes. These limitations necessitates hunting for an alternative source of mitocans with minimum/no side effects. The need for an alternative therapy points towards the ethnomedicinal herbs, known for their minimal side effects and effectiveness. Henceforth recent studies have put forth the effort to utilize anticancer herbs in formulating naturally derived mitocans as an add-on to improve cancer therapeutics. So, our study aims to explore the HK2 targeting potential of phytocompounds from the selected anticancerous herbs Andrographis paniculata (AP) and Centella asiatica (CA). 60 phytocompounds collectively from CA and AP were docked against HK2 and drug-likeness prediction of the selected phytocompounds was performed to screen the best possible ligand for HK2. Furthermore, the docked complexes were subjected to molecular dynamics simulations (MDS) to analyse the molecular mechanism of protein-ligand interactions. The results of the study suggest that the natural compounds asiatic acid and bayogenin (from CA) and andrographolide (from AP) can bepotential natural mitocans by targeting HK2. Further experimental studies (in-vitro and in-vivo) are required to validate the results.

The Efficacy of Vitamin K, A Member Of Naphthoquinones in the Treatment of Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Redox dysregulation originating from metabolic alterations in cancer cells contributes to their proliferation, invasion, and resistance to therapy. Conversely, these features represent a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. Amongst them, Vitamin K (VitK) carries the potential against cancer stem cells, in addition to the rest of tumor mass.

OBJECTIVES

To assess the possible benefits and safety of VitK for cancer treatment using a systematic review and meta-analysis with a mixed-methods approach.

METHODS

We performed a systematic search on several electronic databases for studies comparing VitK treatment with and without combination to the control groups. For quantitative studies, fully or partially reported clinical outcomes such as recurrence rates, survival, overall response and adverse reactions were assessed. For qualitative studies, a narrative synthesis was accomplished.

RESULTS

Our analysis suggested that the clinical outcome of efficacy, the pooled hazard ratio for progression-free survival, and the pooled relative risk for overall survival, and overall response were significantly higher in the VitK therapy group compared to the placebo group (p<0.05). We did not observe any significant difference in the occurrence of adverse events between groups. Among qualitative studies, VitK treatment targeting myelodysplastic syndrome and advanced solid tumors resulted in 24.1% and 10% of clinical response, respectively.

CONCLUSION

VitK not only exerts antitumor effects against a wide range of tumor types, but it also has excellent synergism with other therapeutic agents.

Novel Mitochondria-targeted Drugs for Cancer Therapy

The search for mitochondria-targeted drugs has dramatically risen over the last decade. Mitochondria are essential organelles serving not only as a powerhouse of the cell but also as a key player in cell proliferation and cell death. Their central role in the energetic metabolism, calcium homeostasis and apoptosis makes them an intriguing field of interest for cancer pharmacology. In cancer cells, many mitochondrial signaling and metabolic pathways are altered. These changes contribute to cancer development and progression. Due to changes in mitochondrial metabolism and changes in membrane potential, cancer cells are more susceptible to mitochondria-targeted therapy. The loss of functional mitochondria leads to the arrest of cancer progression and/or a cancer cell death. Identification of mitochondrial changes specific for tumor growth and progression, rational development of new mitochondria-targeted drugs and research on delivery agents led to the advance of this promising area. This review will highlight the current findings in mitochondrial biology, which are important for cancer initiation, progression and resistance, and discuss approaches of cancer pharmacology with a special focus on the anti-cancer drugs referred to as 'mitocans'.

Type and position of linkage govern the cytotoxicity of oleanolic acid rhodamine B hybrids

Oleanolic acid/rhodamine B hybrids exhibit different cytotoxicity depending on the way these two structural elements are linked. While a hybrid holding a piperazinyl spacer at C-28 proved to be cytotoxic in the nano-molar concentration range, hybrids with a direct linkage of the Rho B residue to C-3 of the triterpenoid skeleton are cytotoxic only in the low micro-molar concentration range without any selectivity. This once again underlines the importance of selecting the right spacer and the most appropriate position on the skeleton of the triterpene to achieve the most cytotoxic hybrids possible.

Kaempferol Induces Cell Death and Sensitizes Human Head and Neck Squamous Cell Carcinoma Cell Lines to Cisplatin

Cisplatin is a first-line chemotherapeutic drug commonly used to treat patients with head and neck cancer; nevertheless, cisplatin resistance poses a main challenge for its clinical efficacy. Recent studies have shown that kaempferol, a natural flavonoid found in various plants and foods, has an anticancer effect. The following study evaluated the cytotoxic effects of kaempferol on head and neck tumor cells and their mechanism of action, evaluating the effects on proliferation, the oxygen consumption rate, transmembrane potential, tumor cell migration and induction of apoptosis. Moreover, we determined the effects of a combination of kaempferol and cisplatin on head and neck tumor cells. We found that kaempferol inhibited the oxygen consumption rate and decreased the intracellular ATP content in tumor cells. This novel mechanism may inhibit the migratory capacity and promote antiproliferative effects and apoptosis of tumor cells. Additionally, our in vitro data indicated that kaempferol may sensitize head and neck tumor cells to the effects of cisplatin. These effects provide new evidence for the use of a combination of kaempferol and cisplatin in vivo and their future applications in head and neck cancer therapy.

Mitochondria-targeted vitamin E succinate delivery for reversal of multidrug resistance

Inducing mitochondrial malfunction is an appealing strategy to overcome tumor multidrug resistance (MDR). Reported here a versatile mitochondrial-damaging molecule, vitamin E succinate (VES), is creatively utilized to assist MDR reversal of doxorubicin hydrochloride (DOX·HCl) via a nanovesicle platform self-assembled from amphiphilic polyphosphazenes containing pH-sensitive 1H-benzo-[d]imidazol-2-yl) methanamine (BIMA) groups. Driven by multiple non-covalent interactions, VES is fully introduced into the hydrophobic membrane of DOX·HCl-loaded nanovesicles with loading content of 23.5%. The incorporated VES also offers robust anti-leakage property toward DOX·HCl under normal physiological conditions. More importantly, upon release within acidic tumor cells, VES can target mitochondria and result in various dysfunctions including excessive generation of reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨ_m) loss, and inhibited adenosine triphosphate (ATP) synthesis, which contribute to cell apoptosis and insufficient energy supply for drug efflux pumps. Consequently, the killing-effect of DOX·HCl is significantly enhanced toward drug resistant cancer cells at the optimal mass ratio of DOX·HCl to VES. Further in vivo antitumor investigation on nude mice bearing xenograft drug-resistant human chronic myelogenous leukemia K562/ADR tumors verifies the extremely enhanced anti-tumor efficacy of the dual drug-loaded nanovesicle with the tumor inhibition rate (TIR) of 82.38%. Collectively, this study provides a s safe, facile and promising strategy for both precise drug delivery and MDR eradication to improve cancer therapy.

ONC212 is a Novel Mitocan Acting Synergistically with Glycolysis Inhibition in Pancreatic Cancer

ONC212 is a fluorinated imipridone with preclinical efficacy against pancreatic and other malignancies. Although mitochondrial protease ClpP was identified as an ONC212-binding target, the mechanism leading to cancer cell death is incompletely understood. We investigated mitochondrial dysfunction and metabolic rewiring triggered by ONC212 in pancreatic cancer, a deadly malignancy with an urgent need for novel therapeutics. We found ClpP is expressed in pancreatic cancer cells and is required for ONC212 cytotoxicity. ClpX, the regulatory binding partner of ClpP, is suppressed upon ONC212 treatment. Immunoblotting and extracellular flux analysis showed ONC212 impairs oxidative phosphorylation (OXPHOS) with decrease in mitochondrial-derived ATP production. Although collapse of mitochondrial function is observed across ONC212-treated cell lines, only OXPHOS-dependent cells undergo apoptosis. Cells relying on glycolysis undergo growth arrest and upregulate glucose catabolism to prevent ERK1/2 inhibition and apoptosis. Glucose restriction or combination with glycolytic inhibitor 2-deoxy-D-glucose synergize with ONC212 and promote apoptosis in vitro and in vivo Thus, ONC212 is a novel mitocan targeting oxidative metabolism in pancreatic cancer, leading to different cellular outcomes based on divergent metabolic programs.

Biological evaluation of mitochondria targeting small molecules as potent anticancer drugs

Cancer therapy targets specific metabolic pathways or a single gene. This may result in low therapeutic effects due to drug selectivity and drug resistance. Recent studies revealed that the mitochondrial membrane potential and transmembrane permeability of cancerous mitochondria are differed from normal mitochondria. Thus, chemotherapy targeting cancerous mitochondria could be an innovative and competent strategy for cancer therapy. Previously, our work with a novel group of mitochondria targeting small molecules presented promising inhibitory capability toward various cancer cell lines and suppressed adenosine triphosphate (ATP) generation. Therefore, it is critical to understand the anticancer effect and targeting mechanism of these small molecules. This study investigated the inhibitory activity of mitochondria targeting small molecules with human cervical cancer cells - HeLa to further explore their therapeutic potential. HeLa cells were exposed to 10 µM of synthesized compounds and presented elevation in intracellular reactive oxygen species (ROS) level, impaired mitochondrial membrane potential and upregulation of apoptosis as well as necrosis. In vivo, HeLa cell tumor-bearing BALB/c nude mice were treated with mitochondria targeting small molecules for 12 days consecutively. Throughout this chemotherapy study, no deleterious side effects nor the appearance of toxicity was observed. Furthermore, mitochondria targeting small molecules treated groups exhibited significant down-regulation with both tumor volume and tumor weight compared to the Doxorubicin (DOX) treated group. Thus, inhibition of mitochondrial ATP synthesis, activation of intracellular ROS production, down-regulation of mitochondrial membrane potential and upregulation of apoptosis and necrosis rates are the indications of cancer therapy. In this work, we examined the anticancer capability of four mitochondria targeting small molecules in vitro and in vivo, and demonstrated a novel therapeutic approach in cancer therapy with tremendous potential.

Targeting mitochondrial ion channels for cancer therapy

Pharmacological targeting of mitochondrial ion channels is emerging as a promising approach to eliminate cancer cells; as most of these channels are differentially expressed and/or regulated in cancer cells in comparison to healthy ones, this strategy may selectively eliminate the former. Perturbation of ion fluxes across the outer and inner membranes is linked to alterations of redox state, membrane potential and bioenergetic efficiency. This leads to indirect modulation of oxidative phosphorylation, which is/may be fundamental for both cancer and cancer stem cell survival. Furthermore, given the crucial contribution of mitochondria to intrinsic apoptosis, modulation of their ion channels leading to cytochrome c release may be of great advantage in case of resistance to drugs triggering apoptotic events upstream of the mitochondrial phase. In the present review, we give an overview of the known mitochondrial ion channels and of their modulators capable of killing cancer cells. In addition, we discuss state-of-the-art strategies using mitochondriotropic drugs or peptide-based approaches allowing a more efficient and selective targeting of mitochondrial ion channel-linked events.

Conjugation of Natural Triterpenic Acids with Delocalized Lipophilic Cations: Selective Targeting Cancer Cell Mitochondria

Currently, a new line of research on mitochondria-targeted anticancer drugs is actively developing in the field of biomedicine and medicinal chemistry. The distinguishing features of this universal target for anticancer agents include presence of mitochondria in the overwhelming majority, if not all types of transformed cells, crucial importance of these cytoplasmic organelles in energy production, regulation of cell death pathways, as well as generation of reactive oxygen species and maintenance of calcium homeostasis. Hence, mitochondriotropic anticancer mitocan agents, acting through mitochondrial destabilization, have good prospects in cancer therapy. Available natural pentacyclic triterpenoids are considered promising scaffolds for development of new mitochondria-targeted anticancer agents. These secondary metabolites affect the mitochondria of tumor cells and initiate formation of reactive oxygen species. The present paper focuses on the latest research outcomes of synthesis and study of cytotoxic activity of conjugates of pentacyclic triterpenoids with some mitochondria-targeted cationic lipophilic molecules and highlights the advantages of applying them as novel mitocan agents compared to their prototype natural triterpenic acids.

Modified Gold Nanoparticles for Efficient Delivery of Betulinic Acid to Cancer Cell Mitochondria

Advances in nanomedicine have seen the adaptation of nanoparticles (NPs) for subcellular delivery for enhanced therapeutic impact and reduced side effects. The pivotal role of the mitochondria in apoptosis and their potential as a target in cancers enables selective induction of cancer cell death. In this study, we examined the mitochondrial targeted delivery of betulinic acid (BA) by the mitochondriotropic TPP⁺-functionalized epigallocatechin gallate (EGCG)-capped gold NPs (AuNPs), comparing the impact of polyethylene glycol (PEG) and poly-L-lysine-graft-polyethylene glycol (PLL-g-PEG) copolymer on delivery efficacy. This included the assessment of their cellular uptake, mitochondrial localization and efficacy as therapeutic delivery platforms for BA in the human Caco-2, HeLa and MCF-7 cancer cell lines. These mitochondrial-targeted nanocomplexes demonstrated significant inhibition of cancer cell growth, with targeted nanocomplexes recording IC₅₀ values in the range of 3.12–13.2 µM compared to that of the free BA (9.74–36.31 µM) in vitro, demonstrating the merit of mitochondrial targeting. Their mechanisms of action implicated high amplitude mitochondrial depolarization, caspases 3/7 activation, with an associated arrest at the G0/G1 phase of the cell cycle. This nano-delivery system is a potentially viable platform for mitochondrial-targeted delivery of BA and highlights mitochondrial targeting as an option in cancer therapy.

S-Nitrosylation in Tumor Microenvironment

S-nitrosylation is a selective and reversible post-translational modification of protein thiols by nitric oxide (NO), which is a bioactive signaling molecule, to exert a variety of effects. These effects include the modulation of protein conformation, activity, stability, and protein-protein interactions. S-nitrosylation plays a central role in propagating NO signals within a cell, tissue, and tissue microenvironment, as the nitrosyl moiety can rapidly be transferred from one protein to another upon contact. This modification has also been reported to confer either tumor-suppressing or tumor-promoting effects and is portrayed as a process involved in every stage of cancer progression. In particular, S-nitrosylation has recently been found as an essential regulator of the tumor microenvironment (TME), the environment around a tumor governing the disease pathogenesis. This review aims to outline the effects of S-nitrosylation on different resident cells in the TME and the diverse outcomes in a context-dependent manner. Furthermore, we will discuss the therapeutic potentials of modulating S-nitrosylation levels in tumors.

Triphenilphosphonium Analogs of Chloramphenicol as Dual-Acting Antimicrobial and Antiproliferating Agents

In the current work, in continuation of our recent research, we synthesized and studied new chimeric compounds, including the ribosome-targeting antibiotic chloramphenicol (CHL) and the membrane-penetrating cation triphenylphosphonium (TPP), which are linked by alkyl groups of different lengths. Using various biochemical assays, we showed that these CAM-Cn-TPP compounds bind to the bacterial ribosome, inhibit protein synthesis in vitro and in vivo in a way similar to that of the parent CHL, and significantly reduce membrane potential. Similar to CAM-C4-TPP, the mode of action of CAM-C10-TPP and CAM-C14-TPP in bacterial ribosomes differs from that of CHL. By simulating the dynamics of CAM-Cn-TPP complexes with bacterial ribosomes, we proposed a possible explanation for the specificity of the action of these analogs in the translation process. CAM-C10-TPP and CAM-C14-TPP more strongly inhibit the growth of the Gram-positive bacteria, as compared to CHL, and suppress some CHL-resistant bacterial strains. Thus, we have shown that TPP derivatives of CHL are dual-acting compounds targeting both the ribosomes and cellular membranes of bacteria. The TPP fragment of CAM-Cn-TPP compounds has an inhibitory effect on bacteria. Moreover, since the mitochondria of eukaryotic cells possess qualities similar to those of their prokaryotic ancestors, we demonstrate the possibility of targeting chemoresistant cancer cells with these compounds.

Citrus-derived DHCP inhibits mitochondrial complex II to enhance TRAIL sensitivity via ROS-induced DR5 upregulation

Heat-modified citrus pectin, a water-soluble indigestible polysaccharide fiber derived from citrus fruits and modified by temperature treatment, has been reported to exhibit anticancer effects. However, the bioactive fractions and their mechanisms remain unclear. In this current study, we isolated an active compound, trans-4,5-dihydroxy-2-cyclopentene-l-one (DHCP), from heat-treated citrus pectin, and found that is induces cell death in colon cancer cells via induction of mitochondrial ROS. On the molecular level, DHCP triggers ROS production by inhibiting the activity of succinate ubiquinone reductase (SQR) in mitochondrial complex II. Furthermore, cytotoxicity, apoptotic activity, and activation of caspase cascades were determined in HCT116 and HT-29 cell-based systems, the results indicated that DHCP enhances the sensitivity of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), with DHCP-induced ROS accounting for the synergistic effect between DHCP and TRAIL. Furthermore, the combination of DHCP and TRAIL inhibits the growth of HCT116 and HT-29 xenografts synergistically. ROS significantly increases the expression of TRAIL death receptor 5 (DR5) via the p53 and C/EBP homologous protein pathways. Collectively, our findings indicate that DHCP has a favorable toxicity profile and is a new TRAIL sensitizer that shows promise in the development of pectin-based pharmaceuticals, nutraceuticals, and dietary agents aimed at combating human colon cancer.

Doxorubicin-transferrin conjugate alters mitochondrial homeostasis and energy metabolism in human breast cancer cells

Doxorubicin (DOX) is considered one of the most powerful chemotherapeutic agents but its clinical use has several limitations, including cardiomyopathy and cellular resistance to the drug. By using transferrin (Tf) as a drug carrier, however, the adverse effects of doxorubicin as well as drug resistance can be reduced. The main objective of this study was to determine the exact nature and extent to which mitochondrial function is influenced by DOX-Tf conjugate treatment, specifically in human breast adenocarcinoma cells. We assessed the potential of DOX-Tf conjugate as a drug delivery system, monitoring its cytotoxicity using the MTT assay and ATP measurements. Moreover, we measured the alterations of mitochondrial function and oxidative stress markers. The effect of DOX-Tf was the most pronounced in MDA-MB-231, triple-negative breast cancer cells, whereas non-cancer endothelial HUVEC-ST cells were more resistant to DOX-Tf conjugate than to free DOX treatment. A different sensitivity of two investigate breast cancer cell lines corresponded to the functionality of their cellular antioxidant systems and expression of estrogen receptors. Our data also revealed that conjugate treatment mediated free radical generation and altered the mitochondrial bioenergetics in breast cancer cells.

The Role of Mitochondria in the Chemoresistance of Pancreatic Cancer Cells

The first-line chemotherapies for patients with unresectable pancreatic cancer (PC) are 5-fluorouracil (5-FU) and gemcitabine therapy. However, due to chemoresistance the prognosis of patients with PC has not been significantly improved. Mitochondria are essential organelles in eukaryotes that evolved from aerobic bacteria. In recent years, many studies have shown that mitochondria play important roles in tumorigenesis and may act as chemotherapeutic targets in PC. In addition, according to recent studies, mitochondria may play important roles in the chemoresistance of PC by affecting apoptosis, metabolism, mtDNA metabolism, and mitochondrial dynamics. Interfering with some of these factors in mitochondria may improve the sensitivity of PC cells to chemotherapeutic agents, such as gemcitabine, making mitochondria promising targets for overcoming chemoresistance in PC.