(+)α-Tocopheryl succinate inhibits the mitochondrial respiratory chain complex I and is as effective as arsenic trioxide or ATRA against acute promyelocytic leukemia in vivo

Decoding mitochondria's role in immunity and cancer therapy

The functions of mitochondria, including energy production and biomolecule synthesis, have been known for a long time. Given the rising incidence of cancer, the role of mitochondria in cancer has become increasingly popular. Activated by components released by mitochondria, various pathways interact with each other to induce immune responses to protect organisms from attack. However, mitochondria play dual roles in the progression of cancer. Abnormalities in proteins, which are the elementary structures of mitochondria, are closely linked with oncogenesis. Both the aberrant accumulation of intermediates and mutations in enzymes result in the generation and progression of cancer. Therefore, targeting mitochondria to treat cancer may be a new strategy. Several drugs aimed at inhibiting mutated enzymes and accumulated intermediates have been tested clinically. Here, we discuss the current understanding of mitochondria in cancer and the interactions between mitochondrial functions, immune responses, and oncogenesis. Furthermore, we discuss mitochondria as hopeful targets for cancer therapy, providing insights into the progression of future therapeutic strategies.

AGO2 Protects Against Diabetic Cardiomyopathy by Activating Mitochondrial Gene Translation

BACKGROUND

Diabetes is associated with cardiovascular complications. microRNAs translocate into subcellular organelles to modify genes involved in diabetic cardiomyopathy. However, functional properties of subcellular AGO2 (Argonaute2), a core member of miRNA machinery, remain elusive.

METHODS

We elucidated the function and mechanism of subcellular localized AGO2 on mouse models for diabetes and diabetic cardiomyopathy. Recombinant adeno-associated virus type 9 was used to deliver AGO2 to mice through the tail vein. Cardiac structure and functions were assessed by echocardiography and catheter manometer system.

RESULTS

AGO2 was decreased in mitochondria of diabetic cardiomyocytes. Overexpression of mitochondrial AGO2 attenuated diabetes-induced cardiac dysfunction. AGO2 recruited TUFM, a mitochondria translation elongation factor, to activate translation of electron transport chain subunits and decrease reactive oxygen species. Malonylation, a posttranslational modification of AGO2, reduced the importing of AGO2 into mitochondria in diabetic cardiomyopathy. AGO2 malonylation was regulated by a cytoplasmic-localized short isoform of SIRT3 through a previously unknown demalonylase function.

CONCLUSIONS

Our findings reveal that the SIRT3-AGO2-CYTB axis links glucotoxicity to cardiac electron transport chain imbalance, providing new mechanistic insights and the basis to develop mitochondria targeting therapies for diabetic cardiomyopathy.

Vitamin E succinate mediated apoptosis by juxtaposing endoplasmic reticulum and mitochondria

Vitamin E succinate (VES) is an esterified form of natural α-tocopherol, has turned out to be novel anticancer agent. However, its anticancer mechanisms have not been illustrated. Previously, we reported VES mediated Ca2+ release from the endoplasmic reticulum (ER) causes mitochondrial Ca2+ overload, leading to mitochondrial depolarization and apoptosis. Here, we elucidated the mechanism of VES-induced Ca2+ transfer from ER to mitochondria by investigating the role of VES in ER-mitochondria contact formation. Transmission electron microscopic observation confirms VES mediated ER-mitochondria contact while fluorescence microscopic analysis revealed that VES increased mitochondria-associated ER membrane (MAM) formation. Pre-treatment with the inositol 1,4,5-triphosphate receptor (IP3R) antagonist 2-aminoethyl diphenylborinate (2-APB) decreased VES-induced MAM formation, suggesting the involvement of VES-induced Ca2+ efflux from ER in MAM formation. The ER IP3R receptor is known to interact with voltage-dependent anion channels (VDAC) via the chaperone glucose-regulated protein 75 kDa (GRP75) to bring ER and mitochondria nearby. Although we revealed that VES treatment does not affect GRP75 protein level, it increases GRP75 localization in the MAM. In addition, the inhibition of Ca2+ release from ER by 2-APB decreases GRP75 localization in the MAM, suggesting the possibility of Ca2+-induced conformational change of GRP75 that promotes formation of the IP3R-GRP75-VDAC complex and thereby encourages MAM formation. This study identifies the mechanism of VES-induced enhanced Ca2+ transfer from ER to mitochondria, which causes mitochondrial Ca2+ overload leading to apoptosis.

PML/RARa leukemia induced murine model for immunotherapy evaluation

Even though leukemia murine models are valuable tools for new drug therapy studies, most of these models consist of immunocompromised mice, which do not exhibit immune responses. In order to obtain an adequate leukemia model, we established an acute promyelocytic leukemia transplantation-based model (PML/RARa) in immunocompetent BALB/c mice, thus making it possible to study drug-induced cellular immune responses in leukemia. The development of PML/RARa leukemia was confirmed by leukocytosis (76.27 ± 21.8 vs. 3.40 ± 1.06; P < 0.0001), anemia (7.46 ± 1.86 vs. 15.10 ± 0.96; P < 0.0001), and thrombocytopenia (131.85 ± 39.32 vs. 839.50 ± 171.20; P < 0.0001), and the presence of blasts in the peripheral blood of mice (approximately 50% blasts; P < 0.0001), 15 days after the transplants. These findings were corroborated through differential counts, flow cytometry, and in vivo imaging, which indicated increased number of immature cells in the bone marrow (15.75 ± 3.30 vs 6.69 ± 0.55; P < 0.001), peripheral blood (7.88 ± 2.67 vs 1.22 ± 0.89; P < 0.001), and spleen (35.21 ± 4.12 vs 1.35 ± 0.86; P < 0.0001), as well as promyelocytes in the bone marrow (41.23 ± 4.80 vs 5.73 ± 1.50; P < 0.0001), peripheral blood (46.08 ± 7.52 vs 1.10 ± 0.59; P < 0.0001) and spleen (35.31 ± 8.26 vs 2.49 ± 0.29; P < 0.0001) of PML/RARa mice. Compared to basal conditions of untransplanted mice, the PML/RARa mice exhibited frequencies of T lymphocytes CD4 helper = 14.85 ± 2.91 vs 20.77 ± 2.9 in the peripheral blood (P < 0.05); 12.75 ± 1.33 vs 45.90 ± 2.02 in the spleen (P < 0.0001); CD8 cytotoxic = 11.27 ± 3.44 vs 11.05 ± 1.22 in the peripheral blood (P > 0.05); 10.48 ± 1.16 vs 30.02 ± 1.80 in the spleen (P < 0.0001); natural killer (NK) cells = 3.68 ± 1.35 vs 6.84 ± 0.52 in the peripheral blood (P < 0.001); 4.43 ± 0.57 vs 6.40 ± 1.14 in the spleen (P < 0.05); B cells 2.50 ± 0.60 vs 15.20 ± 5.34 in the peripheral blood (P < 0.001); 17.77 ± 4.39 vs 46.90 ± 5.92 in the spleen (P < 0.0001); neutrophils = 5.97% ± 1.88 vs 31.57 ± 9.14 (P < 0.0001); and monocytes = 6.45 ± 2.97 vs 15.85 ± 2.57 (P < 0.001), selected as classical (3.33 ± 3.40 vs 57.80 ± 16.51, P < 0.0001), intermediate (57.42 ± 10.61 vs 21.75 ± 5.90, P < 0.0001), and non-classical monocytes (37.51 ± 10.85 vs 18.08 ± 7.13, P < 0.05) in the peripheral blood; and as classically activated (M1) within in the bone marrow (3.70 ± 0.94 vs 1.88 ± 0.39, P < 0.05) and spleen 15.19 ± 3.32 vs 9.47 ± 1.61, P < 0.05), in addition to alternatively activated (M2) macrophages within the bone marrow (23.06 ± 5.25 vs 1.76 ± 0.74, P < 0.0001) and spleen (46.51 ± 11.18 vs 30.58 ± 2.64, P < 0.05) compartments. All-trans retinoic acid (ATRA) treatment of PML/RARa mice reduced blast (immature cells) in the bone marrow (8.62 ± 1.81 vs 15.76 ± 1.25; P < 0.05) and spleen (8.75 ± 1.31 vs 35.21 ± 1.55; P < 0.0001) with no changes in the peripheral blood (10.13 ± 3.33 vs 7.88 ± 1.01; P > 0.05), as well as reduced promyelocytes in the bone marrow (19.79 ± 4.84 vs 41.23 ± 1.81; P < 0.05), peripheral blood (31.65 ± 3.92 vs 46.09 ± 2.84; P < 0.05) and spleen (24.84 ± 2.03 vs 41.46 ± 2.39; P < 0.001), and increased neutrophils of the peripheral blood (35.48 ± 7.24 vs 7.83 ± 1.40; P < 0.05) which was corroborated by reducing of immature cells and increase of neutrophil in the stained smears from PML/RARa mice, thus confirming that this model can be used in drug development studies. Our results show the effective induction of PML/RARa leukemia in BALB/c mice, thus producing a low-priced and reliable tool for investigating cellular immune responses in leukemia.

Discovery of Alpha-Tocopheryl Succinate as a Cancer Treatment Agent Led to the Development of Methods to Potentially Improve the Efficacy of Cancer Therapy

The discovery of alpha-tocopheryl succinate (alpha-TS) as a cancer therapeutic agent markedly stimulated research with or without tumor therapeutic agents on cancer cells and normal cells. Results showed that alpha-TS treatment induced apoptosis in cancer cells and enhanced the apoptotic effects of tumor therapeutic agents on tumor cells in a synergistic manner without affecting the growth of normal cells. Liposomal alpha-TS was more effective than alpha-TS. Some tumors are difficult to treat with chemotherapeutic agents while some become resistant of such treatment. Using a nanotechnology technique, it was demonstrated that alpha-TS conjugated with a chemotherapeutic agent enhanced the levels of apoptosis and restored the sensitivity of tumor cells to that chemotherapeutic agent. The mechanisms of action of alpha-TS alone or in combination with therapeutic agents include the following: (a) inhibition of the expression of oncogenes C-myc and H-ras; (b) alterations in the levels of expression of numerous genes; (c) activation of caspases; (d) inhibition of angiogenesis; (e) destabilization of mitochondria and lysosomes; (f) inhibition of production of production of prostaglandin E2 (PGE2) and PGE2-mediated pro-inflammatory responses; (g) reduction of survivin signaling pathway; and (h) reduction of CD47 expression on the tumor cell surface causing enhancement of phagocytic activity of macrophages leading to engulfment of tumor cells. Despite impressive results in cell culture and in animal models, no studies with alpha-TS alone or in combination with cancer therapeutic agents in human cancer resistant to these therapies have been performed.

Recent advances of mitochondrial complex I inhibitors for cancer therapy: Current status and future perspectives

Mitochondrial complex I (CI) as a critical multifunctional respiratory complex of electron transport chain (ETC) in mitochondrial oxidative phosphorylation has been identified as vital and essence in ATP production, biosynthesis and redox balance. Recent progress in targeting CI has provided both insight and inspiration for oncotherapy, highlighting that the development of CI-targeting inhibitors is a promising therapeutic approach to fight cancer. Natural products possessing of ample scaffold diversity and structural complexity are the majority source of CI inhibitors, although low specificity and safety hinder their extensive application. Along with the gradual deepening in understanding of CI structure and function, significant progress has been achieved in exploiting novel and selective small molecules targeting CI. Among them, IACS-010759 had been approved by FDA for phase I trial in advanced cancers. Moreover, drug repurposing represents an effective and prospective strategy for CI inhibitor discovery. In this review, we mainly elaborate the biological function of CI in tumor progression, summarize the CI inhibitors reported in recent years and discuss the further perspectives for CI inhibitor application, expecting this work may provide insights into innovative discovery of CI-targeting drugs for cancer treatment.

Only one carbon difference determines the pro-apoptotic activity of α-tocopheryl esters

α-Tocopheryl succinate (TS), a redox-silent succinyl ester of natural α-Tocopherol, has emerged as a novel anti-cancer agent. However, the underlying mechanism is unclear. We found that the terminal dicarboxylic moiety of tocopheryl esters contributes to apoptosis induction and thus cytotoxicity. To further examine this relationship, we compared the pro-apoptotic activity of TS, which has four carbon atoms in the terminal dicarboxylic moiety, to that of a newly synthesized, tocopheryl glutarate (Tglu), which has five. Cytotoxicity assays in vitro confirmed that TS stimulated apoptosis, while Tglu was non-cytotoxic. In investigating biological mechanisms leading to these opposing effects, we found that TS caused an elevation of intracellular superoxide, but Tglu did not. TS increased intracellular Ca²⁺ in cultured cells, suggesting induction of endoplasmic reticulum (ER) stress; however, Tglu did not affect Ca²⁺ homeostasis. 1,4,5-trisphosphate (IP₃ ) receptor antagonist 2-Aminoethyl diphenylborinate (2-APB) decreased TS-induced intracellular Ca²⁺ , restored mitochondrial activity and cell viability in TS-treated cells, establishing the ER-mitochondria relationship in apoptosis induction. Moreover, real-time PCR, immunostaining and Western blotting assays revealed that TS downregulated glucose-regulated protein 78 (GRP78), which maintains ER homeostasis and promotes cell survival. Conversely, Tglu upregulates GRP78. Taken together, our results suggest a model in which TS-mediated superoxide production and GRP78 inhibition induce ER stress, which elevates intracellular Ca²⁺ and depolarizes mitochondria, leading to apoptosis. Because Tglu does not affect superoxide generation and increases GRP78 expression, it inhibits ER stress and is thereby non-cytotoxic. Our research provides insight into the structure-activity relationship of tocopheryl esters regarding the induction of apoptosis.

The Development and Clinical Applications of Oral Arsenic Trioxide for Acute Promyelocytic Leukaemia and Other Diseases

Appreciation of the properties of arsenic trioxide (ATO) has redefined the treatment landscape for acute promyelocytic leukaemia (APL) and offers promise as a treatment for numerous other diseases. The benefits of ATO in patients with APL is related to its ability to counteract the effects of PML::RARA, an oncoprotein that is invariably detected in the blood or bone marrow of affected individuals. The PML::RARA oncoprotein is degraded specifically by binding to ATO. Thus ATO, in combination with all-trans retinoic acid, has become the curative treatment for ATO. The multiple mechanisms of action of ATO has also paved the way for application in various condition encompassing autoimmune or inflammatory disorders, solid organ tumours, lymphomas and other subtypes of AML. The development of oral formulation of ATO (oral ATO) has reduced costs of treatment and improved treatment convenience allowing widespread applicability. In this review, we discuss the mechanisms of action of ATO, the development of oral ATO, and the applications of oral ATO in APL and other diseases.

C57BL/6 Mice Pretreated With Alpha-Tocopherol Show a Better Outcome of Trypanosoma cruzi Infection With Less Tissue Inflammation and Fibrosis

Chagas disease is accompanied by a multisystem inflammatory disorder that follows Trypanosoma cruzi infection. Alpha-tocopherol has been described as an antioxidant and a potential adjuvant to enhance immune responses to vaccines. Therefore, we have evaluated the immune response to T. cruzi infection upon alpha-tocopherol pre-administration. The results show that administration of alpha-tocopherol before the infection results in lower parasitemia and lower mortality of C57BL/6 mice infected with the Tulahuen T. cruzi strain. Alpha-tocopherol administration in normal C57BL/6 mice resulted in higher levels of IFN-γ production by T and NK cells before and after the infection with T. cruzi. More importantly, previous administration of alpha-tocopherol increased the production of IL-10 by T and myeloid suppressor cells and the formation of effector memory T cells while decreasing the expression of PD-1 on T cells. These results suggest that alpha-tocopherol may limit the appearance of dysfunctional T cells during the acute and early chronic phases of T. cruzi infection, contributing to control infection. In addition, alpha-tocopherol could diminish tissue inflammation and fibrosis in late acute disease. These results strongly suggest that alpha-tocopherol may be a helpful agent to be considered in Chagas disease.

Actinomycin D Targets NPM1c-Primed Mitochondria to Restore PML-Driven Senescence in AML Therapy

Acute myeloid leukemia (AML) pathogenesis often involves a mutation in the NPM1 nucleolar chaperone, but the bases for its transforming properties and overall association with favorable therapeutic responses remain incompletely understood. Here we demonstrate that an oncogenic mutant form of NPM1 (NPM1c) impairs mitochondrial function. NPM1c also hampers formation of promyelocytic leukemia (PML) nuclear bodies (NB), which are regulators of mitochondrial fitness and key senescence effectors. Actinomycin D (ActD), an antibiotic with unambiguous clinical efficacy in relapsed/refractory NPM1c-AMLs, targets these primed mitochondria, releasing mitochondrial DNA, activating cyclic GMP-AMP synthase signaling, and boosting reactive oxygen species (ROS) production. The latter restore PML NB formation to drive TP53 activation and senescence of NPM1c-AML cells. In several models, dual targeting of mitochondria by venetoclax and ActD synergized to clear AML and prolong survival through targeting of PML. Our studies reveal an unexpected role for mitochondria downstream of NPM1c and implicate a mitochondrial/ROS/PML/TP53 senescence pathway as an effector of ActD-based therapies.

SIGNIFICANCE

ActD induces complete remissions in NPM1-mutant AMLs. We found that NPM1c affects mitochondrial biogenesis and PML NBs. ActD targets mitochondria, yielding ROS which enforce PML NB biogenesis and restore senescence. Dual targeting of mitochondria with ActD and venetoclax sharply potentiates their anti-AML activities in vivo. This article is highlighted in the In This Issue feature, p. 2945.

The Combination of Gefitinib With ATRA and ATO Induces Myeloid Differentiation in Acute Promyelocytic Leukemia Resistant Cells

In approximately 15% of patients with acute myeloid leukemia (AML), total and phosphorylated EGFR proteins have been reported to be increased compared to healthy CD34⁺ samples. However, it is unclear if this subset of patients would benefit from EGFR signaling pharmacological inhibition. Pre-clinical studies on AML cells provided evidence on the pro-differentiation benefits of EGFR inhibitors when combined with ATRA or ATO in vitro. Despite the success of ATRA and ATO in the treatment of patients with acute promyelocytic leukemia (APL), therapy-associated resistance is observed in 5-10% of the cases, pointing to a clear need for new therapeutic strategies for those patients. In this context, the functional role of EGFR tyrosine-kinase inhibitors has never been evaluated in APL. Here, we investigated the EGFR pathway in primary samples along with functional in vitro and in vivo studies using several APL models. We observed that total and phosphorylated EGFR (Tyr992) was expressed in 28% and 19% of blast cells from APL patients, respectively, but not in healthy CD34⁺ samples. Interestingly, the expression of the EGF was lower in APL plasma samples than in healthy controls. The EGFR ligand AREG was detected in 29% of APL patients at diagnosis, but not in control samples. In vitro, treatment with the EGFR inhibitor gefitinib (ZD1839) reduced cell proliferation and survival of NB4 (ATRA-sensitive) and NB4-R2 (ATRA-resistant) cells. Moreover, the combination of gefitinib with ATRA and ATO promoted myeloid cell differentiation in ATRA- and ATO-resistant APL cells. In vivo, the combination of gefitinib and ATRA prolonged survival compared to gefitinib- or vehicle-treated leukemic mice in a syngeneic transplantation model, while the gain in survival did not reach statistical difference compared to treatment with ATRA alone. Our results suggest that gefitinib is a potential adjuvant agent that can mitigate ATRA and ATO resistance in APL cells. Therefore, our data indicate that repurposing FDA-approved tyrosine-kinase inhibitors could provide new perspectives into combination therapy to overcome drug resistance in APL patients.

Graphene nanoplatelets and reduced graphene oxide elevate the microalgal cytotoxicity of nano-zirconium oxide

Novel products often have a multitude of nanomaterials embedded; likewise within many products graphite-based products are decorated with nano-zirconium oxide (nZrO₂) because graphene is an ultrahigh conductive material whereas nZrO₂ is for instance fire-retardant. As a consequence, the pristine/isolated nanoparticle has unique beneficial properties but it is no longer the only compound that needs to be considered in risk assessment. Data on joint toxicological implications are particularly important for the hazard assessment of multicomponent nanomaterials. Here, we investigated the mechanisms underlying the cytotoxicity induced by the co-occurrence of nZrO₂ and two graphene nanomaterials including graphene nanoplatelets (GNPs) and reduced graphene oxide (RGO) to the freshwater algae Chlorella pyrenoidosa. Exposure to GNPs and/or RGO induced enhanced cytotoxicity of nZrO₂ to the algae. Intracellular oxidative stress and cellular membrane functional changes in C. pyrenoidosa were the reason for the enhancement of toxicity induced by the binary mixtures of GNPs/RGO and nZrO₂. Furthermore, mitochondria-generated ROS played a major role in regulating the treatment-induced cellular response in the algae. Observations of cellular superficial- and ultra-structures indicated that the binary mixtures provoked oxidative damage to the algal cells. RGO increased the cytotoxicity and the extent of cellular oxidative stress to a higher extent than GNPs. These findings provide new insights that are of use in the risk assessment of mixtures of graphene-based carbon nanomaterials and other ENPs, and fit the new ideas on product testing that respects the combination effects.

Mitochondria-acting carrier-free nanoplatform self-assembled by α-tocopheryl succinate carrying cisplatin for combinational tumor therapy

Unsatisfactory drug loading capability, potential toxicity of the inert carrier and the limited therapeutic effect of a single chemotherapy drug are all vital inhibitory factors of carrier-assisted drug delivery systems for chemotherapy. To address the above obstacles, a series of carrier-free nanoplatforms self-assembled by dual-drug conjugates was constructed to reinforce chemotherapy against tumors by simultaneously disrupting intratumoral DNA activity and inhibiting mitochondria function. In this nanoplatform, the mitochondria-targeting small-molecular drug, α-tocopheryl succinate (TOS), firstly self-assembled into nanoparticles, which then were used as the carrier to conjugate cisplatin (CDDP). Systematic characterization results showed that this nanoplatform exhibited suitable particle size and a negative surface charge with good stability in physicochemical environments, as well as pH-sensitive drug release and efficient cellular uptake. Due to the combined effects of reactive oxygen species (ROS) generation by TOS and DNA damage by CDDP, the developed nanoplatform could induce mitochondrial dysfunction and elevated cell apoptosis, resulting in highly efficient anti-tumor outcomes in vitro. Collectively, the combined design principles adopted for carrier-free nanodrugs construction in this study aimed at targeting different intracellular organelles for facilitating ROS production and DNA disruption can be extended to other carrier-free nanodrugs-dependent therapeutic systems.

Vitamin E TPGS 1000 Induces Apoptosis in the K562 Cell Line: Implications for Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a hematologic malignancy derived from the myeloid lineage molecularly characterized by t(9;22)(q34;q11) resulting in BCR-ABL1 gene fusion, which is known as Philadelphia (Ph) chromosome. Although tyrosine kinase inhibitors (TKIs) have restored and maintained the quality of life of patients with CML, an important minority of patients become resistant to first-and-second-generation TKIs and require an alternative treatment. The K562 cell (Ph+, p53-/-) line was treated with Vit E TPGS 1000 (20-80 μM) only or with other products of interest (e.g., antioxidant N-acetylcysteine (NAC), specific JNK and caspase-3 inhibitor SP600125, and NSCSI, respectively) for 24 h at 37°C. Cells were analyzed by fluorescence microscopy (FM), flow cytometry (FC), and Western blotting (WB) techniques. We show that TPGS induces apoptosis in K562 cells through H₂O₂ signaling mechanism comprising the activation of a minimal molecular cascade: the kinase JNK>the transcription factor c-JUN>the activation of BCL-only BH3 proapoptotic protein PUMA>loss of mitochondrial membrane potential (ΔΨ _m)>activation of caspase-3>chromatin condensation>fragmentation of DNA. Additionally, TPGS oxidizes the stress sensor protein DJ-1-Cys106-SH into DJ-1-Cys106-SO₃ and arrested the cell cycle in the S phase. Remarkably, NAC, SP600125, and NSCSI blocked TPGS-induced OS and apoptosis in K562. Since TPGS is safe in mice and humans, it is especially promising for preclinical and clinical CML leukemia research. Our findings support the view that oxidation therapy offers an important opportunity to eliminate CML.

(-)-Epigallocatechin-3-gallate induces apoptosis and differentiation in leukaemia by targeting reactive oxygen species and PIN1

(-)-Epigallocatechin-3-gallate (EGCG), the major active polyphenol extracted from green tea, has been shown to induce apoptosis and inhibit cell proliferation, cell invasion, angiogenesis and metastasis. Herein, we evaluated the in vivo effects of EGCG in acute myeloid leukaemia (AML) using an acute promyelocytic leukaemia (APL) experimental model (PML/RARα). Haematological analysis revealed that EGCG treatment reversed leucocytosis, anaemia and thrombocytopenia, and prolonged survival of PML/RARα mice. Notably, EGCG reduced leukaemia immature cells and promyelocytes in the bone marrow while increasing mature myeloid cells, possibly due to apoptosis increase and cell differentiation. The reduction of promyelocytes and neutrophils/monocytes increase detected in the peripheral blood, in addition to the increased percentage of bone marrow cells with aggregated promyelocytic leukaemia (PML) bodies staining and decreased expression of PML-RAR oncoprotein corroborates our results. In addition, EGCG increased expression of neutrophil differentiation markers such as CD11b, CD14, CD15 and CD66 in NB4 cells; and the combination of all-trans retinoic acid (ATRA) plus EGCG yield higher increase the expression of CD15 marker. These findings could be explained by a decrease of peptidyl-prolyl isomerase NIMA-interacting 1 (PIN1) expression and reactive oxygen species (ROS) increase. EGCG also decreased expression of substrate oncoproteins for PIN1 (including cyclin D1, NF-κB p65, c-MYC, and AKT) and 67 kDa laminin receptor (67LR) in the bone marrow cells. Moreover, EGCG showed inhibition of ROS production in NB4 cells in the presence of N-acetyl-L-cysteine (NAC), as well as a partial blockage of neutrophil differentiation and apoptosis, indicating that EGCG-activities involve/or are in response of oxidative stress. Furthermore, apoptosis of spleen cells was supported by increasing expression of BAD and BAX, parallel to BCL-2 and c-MYC decrease. The reduction of spleen weights of PML/RARα mice, as well as apoptosis induced by EGCG in NB4 cells in a dose-dependent manner confirms this assumption. Our results support further evaluation of EGCG in clinical trials for AML, since EGCG could represent a promising option for AML patient ineligible for current mainstay treatments.

Mitochondrial metabolism as a target for acute myeloid leukemia treatment

Acute myeloid leukemias (AML) are a group of aggressive hematologic malignancies resulting from acquired genetic mutations in hematopoietic stem cells that affect patients of all ages. Despite decades of research, standard chemotherapy still remains ineffective for some AML subtypes and is often inappropriate for older patients or those with comorbidities. Recently, a number of studies have identified unique mitochondrial alterations that lead to metabolic vulnerabilities in AML cells that may present viable treatment targets. These include mtDNA, dependency on oxidative phosphorylation, mitochondrial metabolism, and pro-survival signaling, as well as reactive oxygen species generation and mitochondrial dynamics. Moreover, some mitochondria-targeting chemotherapeutics and their combinations with other compounds have been FDA-approved for AML treatment. Here, we review recent studies that illuminate the effects of drugs and synergistic drug combinations that target diverse biomolecules and metabolic pathways related to mitochondria and their promise in experimental studies, clinical trials, and existing chemotherapeutic regimens.

α-Tocopherol Attenuates Oxidative Phosphorylation of CD34+ Cells, Enhances Their G0 Phase Fraction and Promotes Hematopoietic Stem and Primitive Progenitor Cell Maintenance

Alpha tocopherol acetate (αTOA) is an analogue of alpha tocopherol (αTOC) that exists in the form of an injectable drug. In the context of the metabolic hypothesis of stem cells, we studied the impact of αTOA on the metabolic energetic profile and functional properties of hematopoietic stem and progenitor cells. In ex vivo experiments performed on cord blood CD34⁺ cells, we found that αTOA effectively attenuates oxidative phosphorylation without affecting the glycolysis rate. This effect concerns complex I and complex II of the mitochondrial respiratory chain and is related to the relatively late increase (3 days) in ROS (Reactive Oxygen Species). The most interesting effect was the inhibition of Hypoxia-Inducible Factor (HIF)-2α (Hexpression, which is a determinant of the most pronounced biological effect-the accumulation of CD34⁺ cells in the G0 phase of the cell cycle. In parallel, better maintenance of the primitive stem cell activity was revealed by the expansion seen in secondary cultures (higher production of colony forming cells (CFC) and Severe Combined Immunodeficiency-mice (scid)-repopulating cells (SRC)). While the presence of αTOA enhanced the maintenance of Hematopoietic Stem Cells (HSC) and contained their proliferation ex vivo, whether it could play the same role in vivo remained unknown. Creating αTOC deficiency via a vitamin E-free diet in mice, we found an accelerated proliferation of CFC and an expanded compartment of LSK (lineage^negative Sca-1⁺cKit⁺) and SLAM (cells expressing Signaling Lymphocytic Activation Molecule family receptors) bone marrow cell populations whose in vivo repopulating capacity was decreased. These in vivo data are in favor of our hypothesis that αTOC may have a physiological role in the maintenance of stem cells. Taking into account that αTOC also exhibits an effect on proliferative capacity, it may also be relevant for the ex vivo manipulation of hematopoietic stem cells. For this purpose, low non-toxic doses of αTOA should be used.

Evolving Chemotherapy Free Regimens for Acute Promyelocytic Leukemia

With the treatment advances over the last three decades, acute promyelocytic leukemia (APL) has evolved from being the most malignant form of acute leukemia to a leukemia with excellent long term survival rates. In the present review, we have summarized data leading to the development of the currently used treatment regimens for APL, which incorporate either none or minimal chemotherapeutic drugs. We have discussed the historical aspects of APL treatment along with the challenges associated with chemotherapy-based approaches and our experience with the use of single agent arsenic trioxide (ATO) which was one of the first successful, non-chemotherapy approaches used for APL. Subsequently, we have reviewed the data from major clinical trials in low-intermediate risk APL and high risk APL which guide the current clinical practice in APL management. With accumulating data on oral ATO, we postulate that the treatment for low-intermediate risk APL will be a completely oral ATO + ATRA regimen in the future. While for high-risk APL, we believe that minimal anthracycline use with ATO + ATRA might become the standard of care soon. A number of promising non-chemotherapy drugs with pre-clinical data would merit clinical testing in the high risk and relapsed setting, with potential to translate to a complete oral chemotherapy free combination regimen in combination with ATO and ATRA.

α-Tocopherol Acetate Attenuates Mitochondrial Oxygen Consumption and Maintains Primitive Cells within Mesenchymal Stromal Cell Population

We present here the data showing, in standard cultures exposed to atmospheric O₂ concentration, that alpha-tocopherol acetate (α-TOA) has a positive impact on primitive cells inside mesenchymal stromal cell (MstroC) population, by maintaining their proliferative capacity. α-TOA decreases the O₂ consumption rate of MStroC probably by impacting respiratory chain complex II activity. This action, however, is not associated with a compensatory increase in glycolysis activity, in spite of the fact that the degradation of HIF-1α was decreased in presence of α-TOA. This is in line with a moderate enhancement of mtROS upon α-TOA treatment. However, the absence of glycolysis stimulation implies the inactivity of HIF-1α which might - if it were active - be related to the maintenance of stemness. It should be stressed that α-TOA might act directly on the gene expression as well as the mtROS themselves, which remains to be elucidated. Alpha-tocopherol acetate (α-TOA), a synthetic vitamin E ester, attenuates electron flow through electron transport chain (ETC) which is probably associated with a moderate increase in mtROS in Mesenchymal Stromal Cells. α-TOA action results in enhancement of the proliferative capacity and maintenance of the differentiation potential of the mesenchymal stem and progenitor cells.

In Vitro Inhibitory Effect of Succinic Acid on T-Cell Acute Lymphoblastic Leukemia Cell Lines

BACKGROUND AND AIMS

Although several treatment regimens for T-cell acute lymphoblastic leukemia (T-ALL), trouble is still ongoing that relapse of disease after therapies in both pediatric and adult patients. Hence, the demand for new alternative therapeutics that are antiproliferative for cancer cells but do not harm healthy cells in treatments is increasing day by day. This study aimed to investigate whether succinic acid show anti-proliferative and apoptotic effect of on T-ALL cell lines.

METHODS

Time and dose-dependent effects of succinic acid on T-ALL cell lines were determined by using WST-1, caspase-3/ bicinchoninic acid (BCA), and Annexin V-Fluorescein isothiocyanate (FITC) assays. We included the MRC-5 cell line in our study as a healthy control group.

RESULTS

Based on our findings, 25 and 50 mmol dosages of succinic acid has shown an apoptotic effect on T-ALL cell lines for 48 h treatment. Also, it has shown that after 48 h exposure of 25 and 50 mmol dosages of succinic acid has no significant cytotoxic effect in healthy MRC-5 cells. Apoptotic activity of succinic acid on CCRF-CEM cell line was caspase-3 dependent but not for MOLT-4. As a consequence, succinic acid was found to effect for T-ALL treatment in vitro and might also enlighten new study fields for different cancer experiments.

Mitochondria in cancer

The rediscovery and reinterpretation of the Warburg effect in the year 2000 occulted for almost a decade the key functions exerted by mitochondria in cancer cells. Until recent times, the scientific community indeed focused on constitutive glycolysis as a hallmark of cancer cells, which it is not, largely ignoring the contribution of mitochondria to the malignancy of oxidative and glycolytic cancer cells, being Warburgian or merely adapted to hypoxia. In this review, we highlight that mitochondria are not only powerhouses in some cancer cells, but also dynamic regulators of life, death, proliferation, motion and stemness in other types of cancer cells. Similar to the cells that host them, mitochondria are capable to adapt to tumoral conditions, and probably to evolve to ‘oncogenic mitochondria' capable of transferring malignant capacities to recipient cells. In the wider quest of metabolic modulators of cancer, treatments have already been identified targeting mitochondria in cancer cells, but the field is still in infancy.

Mitochondria as emerging targets for therapies against T cell acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) comprises a heterogeneous group of hematologic malignancies, arising from diverse genetic alterations in the early lymphocyte development. T-cell subtype of ALL (T-ALL) accounts for about 15% and 25% of ALL in children and adults, respectively. Being less frequent among ALL subtypes, T-ALL represents a high-risk factor for poor prognosis due to its aggressiveness and resistance to common antileukemic drugs. Mitochondria were widely explored recently as a target for anticancer treatment because they are involved in a metabolic reprogramming of a cancer cell and play key roles in reactive oxygen species generation, Ca²⁺ signaling, and cell death induction. Accordingly, a new class of anticancer compounds named mitocans has been developed, which target mitochondria at distinct crucial points to promote their dysfunction and subsequent cell death. The present review analyses the role of mitochondria in malignant reprogramming and emerging therapeutic strategies targeting mitochondria as an "Achilles' heel" in T-ALL, with an emphasis on BH3 mimetics, sequestering pro-survival BCL proteins and voltage-dependent anion channel (VDAC)1-directed drugs, which promote the suppression of aerobic glycolysis, VDAC1 closure, mitochondrial Ca²⁺ overload, stoppage of the oxidative phosphorylation, oxidative stress, and release of proapoptotic factors.

Vitamin E d-α-Tocopheryl Polyethylene Glycol Succinate (TPGS) Provokes Cell Death in Human Neuroblastoma SK-N-SH Cells via a Pro-Oxidant Signaling Mechanism

Neuroblastoma (NB) is the most common neoplasm during infancy. Unfortunately, NB is still a lethal cancer. Therefore, innovative curative therapies are immediately required. In this study, we showed the prodeath activity of TPGS in human NB SK-N-SH cancer cells. NB cells were exposed to TPGS (10-80 μM). We report for the first time that TPGS induces cell death by apoptosis in NB cells via a pro-oxidant-mediated signaling pathway. Certainly, H₂O₂ directly oxidizes DJ-1 cysteine¹⁰⁶-thiolate into DJ-1 cysteine¹⁰⁶-sulfonate, indirectly activates the transcription factors NF-kappaB, p53, and c-JUN, induces the upregulation of mitochondria regulator proteins BAX/PUMA, and provokes the loss of mitochondrial membrane potential (ΔΨ_m) and the activation of caspase-3/AIF, leading to nuclear disintegration, demonstrated by cellular and biochemical techniques such as fluorescence microscopy, flow cytometry, and Western blot analysis. Since TPGS is a U.S. Food and Drug Administration (FDA)-approved pharmaceutical excipient, this molecule might be used in clinical trials for NB treatment.

Dissolved organic matter and aluminum oxide nanoparticles synergistically cause cellular responses in freshwater microalgae

This study investigated the impact of dissolved organic matters (DOM) on the ecological toxicity of aluminum oxide nanoparticles (Al₂O₃NPs) at a relatively low exposure concentration (1 mg L^-1). The unicellular green alga Scenedesmus obliquus was exposed to Al₂O₃NP suspensions in the presence of DOM (fulvic acid) at various concentrations (1, 10, and 40 mg L^-1). The results show that the presence of DOM elevated the growth inhibition toxicity of Al₂O₃NPs towards S. obliquus in a dose-dependent manner. Moreover, the combination of DOM at 40 mg L^-1 and Al₂O₃NPs resulted in a synergistic effect. The relative contribution of Al-ions released from Al₂O₃NPs to toxicity was lower than 5%, indicating that the presence of the particles instead of the dissolved ions in the suspensions was the major toxicity sources, regardless of the presence of DOM. Furthermore, DOM at 10 and 40 mg L^-1 and Al₂O₃NPs synergistically induced the upregulation of intercellular reactive oxygen species levels and superoxide dismutase activities. Analysis of the plasma malondialdehyde concentrations and the observation of superficial structures of S. obliquus indicated that the mixtures of DOM and Al₂O₃NPs showed no significant effect on membrane lipid peroxidation damage. In addition, the presence of both DOM and Al₂O₃NPs contributed to an enhancement in both the mitochondrial membrane potential and the cell membrane permeability (CMP) in S. obliquus. In particular, Al₂O₃NPs in the presence of 10 and 40 mg L^-1 DOM caused a greater increase in CMP compared to Al₂O₃NPs and DOM alone treatments. In conclusion, these findings suggest that DOM at high concentrations and Al₂O₃NPs synergistically interrupted cell membrane functions and triggered subsequent growth inhibition toxicity.

PI3K signaling pathways modulated white spot syndrome virus (WSSV) replication in Procambarus clarkii

The PI3K/AKT signaling pathway is commonly exploited to regulate viral replication and affect the fate of infected cells. In the present study, a PI3K-specific inhibitor (LY294002) was employed to pretreat crayfish to evaluate the effects of PI3K/AKT signaling pathway in WSSV replication. The results showed that the WSSV copy numbers in crayfish pretreated with LY294002 were significantly lower than those in Tris-HCl pretreatment crayfish on the sixth and tenth day after WSSV infection. In semigranular cells, the apoptosis rates were up-regulated on the third day post-WSSV infection, and a significantly lower proportion of apoptosis cells were observed in LY294002-pretreatment group. The expression level of Bax, Bax inhibitor-1 and lectin mRNA in haemocytes of crayfish were increased after WSSV infection. After the secondary stimulation with Tris-HCl, the Bax expression level in LY294002-pretreatment crayfish was significantly higher than that of crayfish pretreated with Tris-HCl on the third or sixth day, but the Toll and lectin mRNA expression decreased significantly on the third, sixth and tenth day. The Bax mRNA expression levels in LY294002-WSSV group were significantly higher than those in Tris-HCl-WSSV group on the third and tenth day. The Bax inhibitor-1 mRNA expression levels in LY294002-WSSV group were significantly lower than those in Tris-HCl-WSSV crayfish on the third day. These results together indicated that the hosts PI3K/AKT signaling pathway play positive roles in WSSV replication through the balance between host cell apoptois and innate immune responses. This information is helpful to further understand the role of PI3K/AKT signaling pathway on WSSV replication in Decapoda crustaceans.

Vitamin E synthetic derivate-TPGS-selectively induces apoptosis in jurkat t cells via oxidative stress signaling pathways: implications for acute lymphoblastic leukemia

D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) is a water-soluble derivative of natural vitamin E commonly used as a drug delivery agent. Recently, TPGS alone has been reported to induce cell death in lung, breast and prostate cancer. However, the effect of TPGS on cancer cell viability remains unclear. Thus, this study was aimed to evaluate the cytotoxic effect of TPGS on human periphral blood lymphocytes (PBL) and on T cell acute lymphocytic leukemia (ALL) Jurkat clone E6-1 cells and its possible mechanism of action. PBL and Jurkat cells were treated with TPGS (10, 20, 40, 60, and 80 μM), and morphological changes in the cell nucleus, mitochondrial membrane potential (ΔΨm), and intracellular reactive oxygen species levels were determined by immune-fluorescence microscopy and flow cytometry. Cellular apoptosis markers were also evaluated by immunocytochemistry. In this study, TPGS induced apoptotic cell death in Jurkat cells, but not in PBL, in a dose-response manner with increasing nuclear DNA fragmentation, increasing cell cycle arrest, and decreasing ΔΨm. Additionally, TPGS increased dichlorofluorescein fluorescence intensity, indicative of H2O2 production, in a dose-independent fashion. TPGS increased DJ-1 Cys(106)-sulfonate, as a marker of intracellular stress and induced the activation of NF-κB, p53 and c-Jun transcription factors. Additionally, it increased the expression of apoptotic markers Bcl-2 related pro-apoptotic proteins Bax and PUMAand activated caspase-3. The antioxidant N-acetyl-L-cysteine and known pharmacological inhibitors protected the cells from the TPGS induced effects. In conclusion, TPGS selectively induces apoptosis in Jurkat cells through two independent but complementary H2O2-mediated signaling pathways. Our findings support the use of TPGS as a potential treatment for ALL.

ΔNp73 overexpression promotes resistance to apoptosis but does not cooperate with PML/RARA in the induction of an APL-leukemic phenotype

Here, we evaluated whether the overexpression of transcriptionally inactive ΔNp73 cooperates with PML/RARA fusion protein in the induction of an APL-leukemic phenotype, as well as its role in vitro in proliferation, myeloid differentiation, and drug-induced apoptosis. Using lentiviral gene transfer, we showed in vitro that ΔNp73 overexpression resulted in increased proliferation in murine bone marrow (BM) cells from hCG-PML/RARA transgenic mice and their wild-type (WT) counterpart, with no accumulation of cells at G2/M or S phases; instead, ΔNp73-expressing cells had a lower rate of induced apoptosis. Next, we evaluated the effect of ΔNp73 on stem-cell self-renewal and myeloid differentiation. Primary BM cells lentivirally infected with human ΔNp73 were not immortalized in culture and did not present significant changes in the percentage of CD11b. Finally, we assessed the impact of ΔNp73 on leukemogenesis or its possible cooperation with PML/RARA fusion protein in the induction of an APL-leukemic phenotype. After 120 days of follow-up, all transplanted mice were clinically healthy and, no evidence of leukemia/myelodysplasia was apparent. Taken together, our data suggest that ΔNp73 had no leukemic transformation capacity by itself and apparently did not cooperate with the PML/RARA fusion protein to induce a leukemic phenotype in a murine BM transplantation model. In addition, the forced expression of ΔNp73 in murine BM progenitors did not alter the ATRA-induced differentiation rate in vitro or induce aberrant cell proliferation, but exerted an important role in cell survival, providing resistance to drug-induced apoptosis.

Reactive oxygen species production triggers green tea-induced anti-leukaemic effects on acute promyelocytic leukaemia model

Green tea (GT) has been consumed as a beverage for thousands of years because of its therapeutic properties observed over time. Because there is no sufficient evidence supporting the protective role of tea intake during the development of acute myeloid leukaemia, we herein study GT extract effects on an acute promyelocytic leukaemia model. Our results demonstrated that GT reduces leucocytosis and immature cells (blasts) in peripheral blood, bone marrow (BM), and spleen of leukaemic mice, parallel with an increase of mature cells in the BM. In addition, GT induces apoptosis of cells in the BM and spleen, confirmed by activation of caspase-3, -8 and -9; GT reduces the malignant clones CD34⁺ and CD117+ in the BM and reduces CD117+ and Gr1+ immature myeloid cells in the spleen; GT increases intracellular reactive oxygen species (ROS) in the BM Gr1+ cells while reducing CD34⁺ and CD117+ cells; GT reduces CXCR4 expression on CD34⁺ and CD117+ cells, and reduces the nuclear translocation of HIF-1α. GT has anti-proliferative effects in leukaemia in vivo by inhibiting malignant clone expansion, probably by modulating the intracellular production of ROS.

Co-delivery nanocarriers targeting folate receptor and encapsulating 2-deoxyglucose and α-tocopheryl succinate enhance anti-tumor effect in vivo

A combination administration of chemical agents was highlighted to treat tumors. Recently, tumor cell has been found to be different from normal cell in metabolic manner. Most of cancer cells prefer aerobic glycolysis to mitochondrial oxidative phosphorylation (OXPHOS) to satisfy energy and biomass synthesis requirement to survive, grow and proliferate, which provides novel and potential therapeutic targets for chemotherapy. Here, 2-deoxy-d-glucose (2-DG), a potent inhibitor of glucose metabolism, was used to inhibit glycolysis of tumor cells; α-tocopheryl succinate (α-TOS), a water-insoluble vitamin E derivative, was chosen to suppress OXPHOS. Our data demonstrated that the combination treatment of 2-DG and α-TOS could significantly promote the anti-tumor efficiency in vitro compared with administration of the single drug. In order to maximize therapeutic activity and minimize negative side effects, a co-delivery nanocarrier targeting folate receptor (FR) was developed to encapsulate 2-DG and α-TOS simultaneously based on our previous work. Transmission electron microscope, dynamic light scattering method and UV-visible spectrophotometers were used to investigate morphology, size distribution and loading efficiency of the α-TOS-2-DG-loaded and FR-targeted nanoparticles (TDF NPs). The TDF NPs were found to possess a layer-by-layer shape, and the dynamic size was <100 nm. The final encapsulation efficiencies of α-TOS and 2-DG in TDF NPs were 94.3%±1.3% and 61.7%±7.7% with respect to drug-loading capacities of 8.9%±0.8% and 13.2%±2.6%, respectively. Almost no α-TOS release was found within 80 h, and release of 2-DG was sustained and slow within 72 h. The results of FR binding assay and fluorescence biodistribution revealed that TDF NPs could target FR highly expressed on tumor cell in vitro and in vivo. Further, in vivo anti-tumor experiments showed that TDF NPs had an improved biological function with less toxicity. Thus, our work indicates that the co-delivery TDF NPs have a great potential in tumor therapy.

Promyelocytic Leukemia Protein, a Protein at the Crossroad of Oxidative Stress and Metabolism

SIGNIFICANCE

Cellular metabolic activity impacts the production of reactive oxygen species (ROS), both positively through mitochondrial oxidative processes and negatively by promoting the production of reducing agents (including NADPH and reduced glutathione). A defined metabolic state in cancer cells is critical for cell growth and long-term self-renewal, and such state is intrinsically associated with redox balance. Promyelocytic leukemia protein (PML) regulates several biological processes, at least in part, through its ability to control the assembly of PML nuclear bodies (PML NBs). Recent Advances: PML is oxidation-prone, and oxidative stress promotes NB biogenesis. These nuclear subdomains recruit many nuclear proteins and regulate their SUMOylation and other post-translational modifications. Some of these cargos-such as p53, SIRT1, AKT, and mammalian target of rapamycin (mTOR)-are key regulators of cell fate. PML was also recently shown to regulate oxidation.

CRITICAL ISSUES

While it was long considered primarily as a tumor suppressor protein, PML-regulated metabolic switch uncovered that this protein could promote survival and/or stemness of some normal or cancer cells. In this study, we review the recent findings on this multifunctional protein.

FUTURE DIRECTIONS

Studying PML scaffolding functions as well as its fine role in the activation of p53 or fatty acid oxidation will bring new insights in how PML could bridge oxidative stress, senescence, cell death, and metabolism. Antioxid. Redox Signal. 26, 432-444.

α-Tocopheryl Succinate Affects Malignant Cell Viability, Proliferation, and Differentiation

The widespread occurrence of malignant tumors motivates great attention to finding and investigating effective new antitumor preparations. Such preparations include compounds of the vitamin E family. Among them, α-tocopheryl succinate (vitamin E succinate (VES)) has the most pronounced antitumor properties. In this review, various targets and mechanisms of the antitumor effect of vitamin E succinate are characterized. It has been shown that VES has multiple intracellular targets and effects, and as a result VES is able to induce apoptosis in tumor cells, inhibit their proliferation, induce differentiation, prevent metastasizing, and inhibit angiogenesis. However, VES has minimal effects on normal cells and tissues. Due to the variety of targets and selectivity of action, VES is a promising agent against malignant neoplasms. More detailed studies in this area can contribute to development of effective and safe chemotherapeutic preparations.

Carbohydrate-based amphiphilic nano delivery systems for cancer therapy

Nanoparticles (NPs) are novel drug delivery systems that have been attracting more and more attention in recent years, and have been used for the treatment of cancer, infection, inflammation and other diseases. Among the numerous classes of materials employed for constructing NPs, organic polymers are outstanding due to the flexibility of design and synthesis and the ease of modification and functionalization. In particular, NP based amphiphilic polymers make a great contribution to the delivery of poorly-water soluble drugs. For example, natural, biocompatible and biodegradable products like polysaccharides are widely used as building blocks for the preparation of such drug delivery vehicles. This review will detail carbohydrate based amphiphilic polymeric systems for cancer therapy. Specifically, it focuses on the nature of the polymer employed for the preparation of targeted nanocarriers, the synthetic methods, as well as strategies for the application and evaluation of biological activity. Applications of the amphiphilic polymer systems include drug delivery, gene delivery, photosensitizer delivery, diagnostic imaging and specific ligand-assisted cellular uptake. As a result, a thorough understanding of the relationship between chemical structure and biological properties facilitate the optimal design and rational clinical application of the resulting carbohydrate based nano delivery systems for cancer therapy.

Turn up the cellular power generator with vitamin E analogue formulation

The down regulation of the cellular power generator, adenosine triphosphate (ATP) synthase, in various cancer cells plays an obstructive role in mitochondria-mediated cell death. Cancer cells up-regulate ATPase inhibitory factor 1 (IF1) and down-regulate β-F1-ATPase of ATP synthase to enhance aerobic glycolysis for tumor growth via inhibiting total ATP synthase activity in the oxidative phosphorylation (OXPHOS) pathway. Alpha-tocopheryl succinate (α-TOS), one of the most bioactive derivatives of vitamin E, can selectively induce apoptosis in numerous cancer cells. The cancer cell selective apoptosis inducing property of α-TOS is correlated to: mitochondrial destabilization, inhibition of anti-apoptotic B cell lymphoma 2 (Bcl2) and protein kinase C (PKC), caspase 3 activation, production of mitochondrial reactive oxygen species (ROS), and inhibition of succinate dehydrogenase activity of mitochondrial complex II, and interaction with complex I to some extent. There is no report which elucidates the effects of α-TOS on the cellular power generator, complex V or ATP synthase. Here, we report the activation of mitochondrial ATP synthase using a suitably designed chemical formulation of α-TOS for the first time. A mitochondria targeted α-TOS nanoparticle formulation demonstrated enhanced cytotoxicity and mitochondrial activities in cancer cells by inhibiting Bcl2 protein and activating ATP synthase. The modulation of ATP synthase in cancer cells by the engineered formulation of α-TOS can be promising for solid cancers with compromised ATP synthase.

Tocopherols in cancer: An update

Tocopherols exist in four forms designated as α, β, δ, and γ. Due to their strong antioxidant properties, tocopherols have been suggested to reduce the risk of cancer. Cancer prevention studies with tocopherols have mostly utilized α-tocopherol. Large-scale clinical trials with α-tocopherol provided inconsistent results regarding the cancer-preventive activities of tocopherols. This review summarizes our current understanding of the anticancer activities of different forms of tocopherols based on follow-up of the clinical trials, recent epidemiological evidences, and experimental studies using in vitro and in vivo models. The experimental data provide strong evidence in support of the anticancer activities of δ-tocopherol, γ-tocopherol, and the natural tocopherol mixture rich in γ-tocopherol, γ-TmT, over α-tocopherol. Such outcomes emphasize the need for detailed investigation into the cancer-preventive activities of different forms of tocopherols to provide a strong rationale for intervention studies in the future.

The effect of alpha-tocopheryl succinate on succinate respiration in rat liver mitochondria

We compared the effect of alpha-tocopheryl succinate (TOS) on succinate-dependent respiration in rat liver mitochondria, homogenate and permeabilized hepatocytes in both a coupled and uncoupled state. In isolated mitochondria, a significant inhibitory effect was observed at a concentration of 5 microM, in liver homogenate at 25 microM and in permeabilized hepatocytes at 50 microM. The inhibitory effect of TOS on succinate respiration in an uncoupled state was less pronounced than in a coupled state in all the experimental models tested. When the concentration dependence of the TOS inhibitory effect was tested, the most sensitive in both states were isolated mitochondria; the most resistant were permeabilized hepatocytes.

Targeting mitochondrial function for the treatment of breast cancer

There are many approaches used to control breast cancer, although the most efficient strategy is the reactivation of apoptosis. Since mitochondria play an important role in cellular metabolism and homeostasis, as well as in the regulation of cell death pathways, we focus here on metabolic remodeling and mitochondrial alterations present in breast tumor cells. We review strategies including classes of compounds and delivery systems that target metabolic and specific mitochondrial alterations to kill tumor cells without affecting their normal counterparts. We present here the arguments for the improvement of already existent molecules and the design of novel promising anticancer drug candidates that target breast cancer mitochondria.

Active Pin1 is a key target of all-trans retinoic acid in acute promyelocytic leukemia and breast cancer

A common key regulator of oncogenic signaling pathways in multiple tumor types is the unique isomerase Pin1. However, available Pin1 inhibitors lack the required specificity and potency for inhibiting Pin1 function in vivo. By using mechanism-based screening, here we find that all-trans retinoic acid (ATRA)--a therapy for acute promyelocytic leukemia (APL) that is considered the first example of targeted therapy in cancer, but whose drug target remains elusive--inhibits and degrades active Pin1 selectively in cancer cells by directly binding to the substrate phosphate- and proline-binding pockets in the Pin1 active site. ATRA-induced Pin1 ablation degrades the protein encoded by the fusion oncogene PML-RARA and treats APL in APL cell and animal models as well as in human patients. ATRA-induced Pin1 ablation also potently inhibits triple-negative breast cancer cell growth in human cells and in animal models by acting on many Pin1 substrate oncogenes and tumor suppressors. Thus, ATRA simultaneously blocks multiple Pin1-regulated cancer-driving pathways, an attractive property for treating aggressive and drug-resistant tumors.

Targeting of leukemia-initiating cells in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML) with peculiar molecular, phenotypic and clinical features and unique therapeutic response to specific treatments. The disease is characterized by a single, pathognomonic molecular event, consisting of the translocation t(15;17) which gives rise to the PML/retinoic acid receptor α (RARα) hybrid protein. The development of this leukemia is mainly related to the fusion oncoprotein PML/RARα, acting as an altered RAR mediating abnormal signalling and repression of myeloid differentiation, with consequent accumulation of undifferentiated promyelocytes. The prognosis of APL has dramatically been improved with the introduction in therapy of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). The main effect of these two drugs is linked to the targeting of either RAR moiety of the PML/RARα molecule and induction of cell differentiation (ATRA) or of the PML moiety of the fusion protein and induction of leukemic cell apoptosis, including leukemic progenitors (mostly induced by ATO). These two drugs exhibited excellent synergism and determine a very high rate of durable remissions in low/intermediate-risk APLs, when administered in the absence of any chemotherapeutic drug. The strong synergism and the marked clinical efficacy of these two agents when administered together seem to be related to their capacity to induce PML/RARα degradation and complete eradication of leukemia stem cells.

Mitochondrially targeted vitamin E succinate modulates expression of mitochondrial DNA transcripts and mitochondrial biogenesis

AIMS

To assess the effect of mitochondrially targeted vitamin E (VE) analogs on mitochondrial function and biogenesis.

RESULTS

Mitochondrially targeted vitamin E succinate (MitoVES) is an efficient inducer of apoptosis in cancer cells. Here, we show that unlike its untargeted counterpart α-tocopheryl succinate, MitoVES suppresses proliferation of cancer cells at sub-apoptotic doses by way of affecting the mitochondrial DNA (mtDNA) transcripts. We found that MitoVES strongly suppresses the level of the displacement loop transcript followed by those of mtDNA genes coding for subunits of mitochondrial complexes. This process is coupled to the inhibition of mitochondrial respiration, dissipation of the mitochondrial membrane potential, and generation of reactive oxygen species. In addition, exposure of cancer cells to MitoVES led to decreased expression of TFAM and diminished mitochondrial biogenesis. The inhibition of mitochondrial transcription was replicated in vivo in a mouse model of HER2(high) breast cancer, where MitoVES lowered the level of mtDNA transcripts in cancer cells but not in normal tissue.

INNOVATION

Our data show that mitochondrially targeted VE analogs represent a novel class of mitocans that not only induce apoptosis at higher concentrations but also block proliferation and suppress normal mitochondrial function and transcription at low, non-apoptogenic doses.

CONCLUSIONS

Our data indicate a novel, selective anti-cancer activity of compounds that act by targeting mitochondria of cancer cells, inducing significant alterations in mitochondrial function associated with transcription of mtDNA-coded genes. These changes subsequently result in the arrest of cell proliferation.

In vivo selective imaging and inhibition of leukemia stem-like cells using the fluorescent carbocyanine derivative, DiOC5(3)

Elimination of leukemia stem cells (LSCs) is necessary for the destruction of malignant cell populations. Owing to the very small number of LSCs in leukemia cells, xenotransplantation studies are difficult in terms of functionally and pathophysiologically replicating clinical conditions of cell culture experiments. There is currently a limited number of lead compounds that target LSCs. Using the LSC-xenograft zebrafish screening method we previously developed, we found that the fluorescent compound 3,3'-dipentyloxacarbocyanine iodide (DiOC5(3)) selectively marked LSCs and suppressed their proliferation in vivo and in vitro. DiOC5(3) had no obvious toxicity to human umbilical cord blood CD34+ progenitor cells and normal zebrafish. It accumulated in mitochondria through organic anion transporter polypeptides that are overexpressed in the plasma membrane of LSCs, and induced apoptosis via ROS overproduction. DiOC5(3) also inhibited the nuclear translocation of NF-κB through the downregulation of LSC-selective pathways, as indicated from DNA microarray analysis. In summary, DiOC5(3) is a new type of anti-LSC compound available for diagnostic imaging and therapeutics that has the advantage of being a single fluorescent chemical.

Inhibition of mitochondrial glycerol-3-phosphate dehydrogenase by α-tocopheryl succinate

α-Tocopheryl succinate (TOS), a redox-silent analogue of vitamin E, suppresses cell growth in a number of clinical and experimental cancers, inhibits mitochondrial succinate dehydrogenase (SDH) and activates reactive oxygen species (ROS) generation. The aim of this study was to test whether TOS also inhibits glycerol-3-phosphate dehydrogenase (mGPDH), another flavoprotein-dependent enzyme of the mitochondrial respiratory chain because there are differences between electron transfer pathway from SDH and mGPDH to coenzyme Q pool. For our experiments brown adipose tissue mitochondria with high expression of mGPDH were used. Our data showed that inhibition of glycerol-3-phosphate (GP)-dependent oxygen consumption by TOS was more pronounced than the succinate (SUC)-dependent one (50% inhibition was reached at 10 μmol/l TOS vs. 80 μmol/l TOS, respectively). A comparison of the inhibitory effect of TOS on GP-oxidase, GP-cytochrome c oxidoreductase and GP-dehydrogenase activities showed that TOS directly interacts with the dehydrogenase. After TOS application the GP-dependent generation of ROS was highly depressed. It may thus be concluded that TOS-induced inhibition of mGPDH is more pronounced than TOS-induced inhibition of SDH and that the inhibitory effect of TOS for both substrates is exerted at different locations of the particular dehydrogenases. Our data indicate that the inhibition of mGPDH activity could also play a role in TOS-induced growth suppression in neoplastic cells.

The effects of bioactive compounds from plant foods on mitochondrial function: a focus on apoptotic mechanisms

Mitochondria are essential organelles for cellular integrity and functionality maintenance and their imparement is implicated in the development of a wide range of diseases, including metabolic, cardiovascular, degenerative and hyperproliferative pathologies. The identification of different compounds able to interact with mitochondria for therapeutic purposes is currently becoming of primary importance. Indeed, it is well known that foods, particularly those of vegetable origin, present several constituents with beneficial effects on health. This review summarizes and updates the most recent findings concerning the mechanisms through which different dietary compounds from plant foods affect mitochondria functionality in healthy and pathological in vitro and in vivo models, paying particular attention to the pathways involved in mitochondrial biogenesis and apoptosis.

α-Tocopheryl succinate pre-treatment attenuates quinone toxicity in prostate cancer PC3 cells

α-Tocopheryl succinate is one of the most effective analogues of vitamin E for inhibiting cell proliferation and inducing cell death in a variety of cancerous cell lines while sparing normal cells or tissues. αTocopheryl succinate inhibits oxidative phosphorylation at the level of mitochondrial complexes I and II, thus enhancing reactive oxygen species generation which, in turn, induces the expression of Nrf2-driven antioxidant/detoxifying genes. The cytoprotective role of Nrf2 downstream genes/proteins prompted us to investigate whether and how α-tocopheryl succinate increases resistance of PC3 prostate cancer cells to pro-oxidant damage. A 4h α-tocopheryl succinate pre-treatment increases glutathione intracellular content, indicating that the vitamin E derivative is capable of training the cells to react to an oxidative insult. We found that α-tocopheryl succinate pre-treatment does not enhance paraquat-/hydroquinone-induced cytotoxicity whereas it exhibits an additional/synergistic effect on H₂O₂₋/docetaxel-induced cytotoxicity. While glutathione and heme oxygenase-1 are not involved in α-tocopheryl succinate-induced adaptive response to paraquat,

NAD(P)H

quinone oxidoreductase seems to be responsible, at least in part, for the lack of the additional response. Silencing the gene and/or the inhibition of

NAD(P)H

quinone oxidoreductase activity counteracts the α-tocopheryl succinate-induced adaptive response. In conclusion, the adaptive response to α-tocopheryl succinate shows that the activation of Nrf2 can promote the survival of cancer cells in an unfavourable environment.

Synergy against PML-RARa: targeting transcription, proteolysis, differentiation, and self-renewal in acute promyelocytic leukemia

Pandolfi et al. provide an in-depth discussion on the synergism between all-trans-retinoic acid and arsenic trioxide treatment and their mechanisms of action on acute promyelocytic leukemia.

Acute promyelocytic leukemia (APL) is a hematological malignancy driven by a chimeric oncoprotein containing the C terminus of the retinoic acid receptor-a (RARa) fused to an N-terminal partner, most commonly promyelocytic leukemia protein (PML). Mechanistically, PML-RARa acts as a transcriptional repressor of RARa and non-RARa target genes and antagonizes the formation and function of PML nuclear bodies that regulate numerous signaling pathways. The empirical discoveries that PML-RARa–associated APL is sensitive to both all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO), and the subsequent understanding of the mechanisms of action of these drugs, have led to efforts to understand the contribution of molecular events to APL cell differentiation, leukemia-initiating cell (LIC) clearance, and disease eradication in vitro and in vivo. Critically, the mechanistic insights gleaned from these studies have resulted not only in a better understanding of APL itself, but also carry valuable lessons for other malignancies.

Tocopheramine succinate and tocopheryl succinate: mechanism of mitochondrial inhibition and superoxide radical production

Tocopherols (TOH) are lipophilic antioxidants which require the phenolic OH group for their redox activity. In contrast, non-redox active esters of α-TOH with succinate (α-TOS) were shown to possess proapoptotic activity in cancer cells. It was suggested that this activity is mediated via mitochondrial inhibition with subsequent O2(-) production triggering apoptosis and that the modification of the linker between the succinate and the lipophilic chroman may modulate this activity. However, the specific mechanism and the influence of the linker are not clear yet on the level of the mitochondrial respiratory chain. Therefore, this study systematically compared the effects of α-TOH acetate (α-TOA), α-TOS and α-tocopheramine succinate (α-TNS) in cells and submitochondrial particles (SMP). The results showed that not all cancer cell lines are highly sensitive to α-TOS and α-TNS. In HeLa cells α-TNS did more effectively reduce cell viability than α-TOS. The complex I activity of SMP was little affected by α-TNS and α-TOS while the complex II activity was much more inhibited (IC50=42±8μM α-TOS, 106±8μM α-TNS, respectively) than by α-TOA (IC50 >1000μM). Also the complex III activity was inhibited by α-TNS (IC50=137±6μM) and α-TOS (IC50=315±23μM). Oxygen consumption of NADH- or succinate-respiring SMP, involving the whole electron transfer machinery, was dose-dependently decreased by α-TOS and α-TNS, but only marginal effects were observed in the presence of α-TOA. In contrast to the similar inhibition pattern of α-TOS and α-TNS, only α-TOS triggered O2(-) formation in succinate- and NADH-respiring SMP. Inhibitor studies excluded complex I as O2(-) source and suggested an involvement of complex III in O2(-) production. In cancer cells only α-TOS was reproducibly able to increase O2(-) levels above the background level but neither α-TNS nor α-TOA. Furthermore, the stability of α-TNS in liver homogenates was significantly lower than that of α-TOS. In conclusion, this suggests that α-TNS although it has a structure similar to α-TOS is not acting via the same mechanism and that for α-TOS not only complex II but also complex III interactions are involved.