Targeting mitochondria for cancer therapy

Increasing the π-Expansive Ligands in Ruthenium(II) Polypyridyl Complexes: Synthesis, Characterization, and Biological Evaluation for Photodynamic Therapy Applications

Lack of selectivity is one of the main issues with currently used chemotherapies, causing damage not only to altered cells but also to healthy cells. Over the last decades, photodynamic therapy (PDT) has increased as a promising therapeutic tool due to its potential to treat diseases like cancer or bacterial infections with a high spatiotemporal control. Ruthenium(II) polypyridyl compounds are gaining attention for their application as photosensitizers (PSs) since they are generally nontoxic in dark conditions, while they show remarkable toxicity after light irradiation. In this work, four Ru(II) polypyridyl compounds with sterically expansive ligands were studied as PDT agents. The Ru(II) complexes were synthesized using an alternative route to those described in the literature, which resulted in an improvement of the synthesis yields. Solid-state structures of compounds [Ru(DIP)2phen]Cl2 and [Ru(dppz)2phen](PF6)2 have also been obtained. It is well-known that compound [Ru(dppz)(phen)2]Cl2 binds to DNA by intercalation. Therefore, we used [Ru(dppz)2phen]Cl2 as a model for DNA interaction studies, showing that it stabilized two different sequences of duplex DNA. Most of the synthesized Ru(II) derivatives showed very promising singlet oxygen quantum yields, together with noteworthy photocytotoxic properties against two different cancer cell lines, with IC50 in the micro- or even nanomolar range (0.06-7 μM). Confocal microscopy studies showed that [Ru(DIP)2phen]Cl2 and [Ru(DIP)2TAP]Cl2 accumulate preferentially in mitochondria, while no mitochondrial internalization was observed for the other compounds. Although [Ru(dppn)2phen](PF6)2 did not accumulate in mitochondria, it interestingly triggered an impairment in mitochondrial respiration after light irradiation. Among others, [Ru(dppn)2phen](PF6)2 stands out for its very good IC50 values, correlated with a very high singlet oxygen quantum yield and mitochondrial respiration disruption.

SLED1 Promoting Cell Proliferation and Inhibiting Apoptosis in Acute Myeloid Leukemia: a Study

In this study, we aimed to explore long non-coding RNA (lncRNA) sustained low-efficiency dialysis (SLED1) correlated with Bcl-2 apoptosis pathway in acute myeloid leukemia (AML). This study further aimed to determine its role in the regulation of AML progression and its action as a potential biomarker for better prognosis. AML microarray profiles GSE97485 and probe annotation from the Gene Expression Omnibus (GEO) database from the National Center for Biotechnology Information (NCBI) were detected using the GEO2R tool ( http://www.ncbi.nlm.nih.gov/geo/geo2r/ ). The expression of AML was downloaded from the TCGA database ( http://cancergenome.nih.gov/ ). The statistical analysis of the database was processed with R software. Bioinformatic analysis found that lncRNA SLED1 is highly expressed in AML patients and is associated with poor prognosis. We found that the increased SLED1 expression levels in AML were significantly correlated with FAB classification, human race, and age. Our study has shown that upregulation of SLED1 promoted AML cell proliferation and inhibited cell apoptosis in vitro; RNA sequencing showed increased expression of BCL-2 and indicated that SLED1 might promote the development of AML by regulating BCL-2. Our results showed that SLED1 could promote the proliferation and inhibit the apoptosis of AML cells. SLED1 might promote the development of AML by regulating BCL-2, but the mechanism involved in the progression of AML is unclear. SLED1 plays an important role in AML progression, may be applied as a rapid and economical AML prognostic indicator to predict the survival of AML patients, and help guide experiments for potential clinical drag targets.

A cell transmembrane peptide chimeric M(27-39)-HTPP targeted therapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent malignant tumor, with a growing incidence and death rate worldwide. The aims and challenges of treating HCC include targeting the tumor, entering the tumor tissue, inhibiting the spread and growth of tumor cells. M27-39 is a small peptide isolated from the antimicrobial peptide Musca domestica cecropin (MDC), whereas HTPP is a liver-targeting, cell-penetrating peptide obtained from the circumsporozoite protein (CSP) of Plasmodium parasites. In this study, M27-39 was modified by HTPP to form M(27-39)-HTPP, which targeted tumor penetration to treat HCC. Here, we revealed that M(27-39)-HTPP had a good ability to target and penetrate the tumor, effectively limit the proliferation, migration, and invasion, and induce the apoptosis in HCC. Notably, M(27-39)-HTPP demonstrated good biosecurity when administered at therapeutic doses. Accordingly, M(27-39)-HTPP could be used as a new, safe, and efficient therapeutic peptide for HCC.

Resveratrol Carbon Dots Disrupt Mitochondrial Function in Cancer Cells

Resveratrol, a natural polyphenol, exhibits beneficial health properties and has been touted as a potential anti-tumor agent. Here, we demonstrate potent anti-cancer effects of carbon dots (C-dots) synthesized from resveratrol. The mild synthesis conditions retained resveratrol functional moieties upon the carbon dots' (C-dots) surface, an important requisite for achieving specificity toward cancer cells and biological activities. Indeed, the disruptive effects of the resveratrol-C-dot were more pronounced in several cancer cell types compared to normal cells, underscoring targeting capabilities of the C-dots, a pertinent issue for the development of cancer therapeutics. In particular, we observed impairment of mitochondrial functionalities, including intracellular calcium release, inhibition of cytochrome-C oxidase enzyme activity, and mitochondrial membrane perturbation. Furthermore, the resveratrol C-dots were more potent than either resveratrol molecules alone, known anti-cancer polyphenolic agents such as curcumin and triphenylphosphonium, or C-dots prepared from different carbonaceous precursors. This study suggests that resveratrol-synthesized C-dots may have promising therapeutic potential as anti-cancer agents.

Mitochondria-targeting nano therapy altering IDH2-mediated EZH2/EZH1 interaction as precise epigenetic regulation in glioblastoma

Glioblastoma (GBM) is a complex brain cancer with frequent relapses and high mortality and still awaits effective treatment. Mitochondria dysfunction is a pathogenic condition in GBM and could be a prime therapeutic target for ceasing GBM progression. Strategies to overcome brain solid tumor barriers and selectively target mitochondria within specific cell types may improve GBM treatment. Here, we present hypericin-conjugated gold nanoparticles (PEG-AuNPs@Hyp) where hypericin is a mitochondrion-targeting agent exhibiting multimodal therapy by critically impacting the IDH2 gene (Isocitrate dehydrogenase) and its interaction with polycomb methyltransferase EZH1/2 for GBM therapy. It significantly localizes in mitochondria by enhanced cellular uptake in the human GBM cell lines/three-dimensional (3D) culture model under red-light exposure. It triggers oxidative stress and changes the mitochondrial potential, with increased Bax/Bcl2 ratio enhancing GBM cell death. The suppressed expression of mutated IDH2 and polycomb group of proteins upon PEG-AuNPs@Hyp/light exposure regulates mitochondria-targeting-mediated GBM metabolism with epigenetic repression of complex machinery function. Polyubiquitination and proteasomal degradation of EZH1 indicate the implication of these polycomb proteins in GBM progression. Chromatin immunoprecipitation reveals the IDH2 and EZH1/EZH2 direct interaction, confirming the role played by IDH2 in modulating the expression of EZH1 and EZH2. In vivo studies further displayed better tumor ablation in a GBM tumor-bearing nude mouse model. The present multimodal nanoformulation compromised the functional dependency of polycomb on mitochondrial IDH2 and established the mechanism of GBM inhibition.

Low-dose exposure to phytosynthesized gold nanoparticles combined with glutamine deprivation enhances cell death in the cancer cell line HeLa via oxidative stress-mediated mitochondrial dysfunction and G0/G1 cell cycle arrest

Cancer cells use nutrients like D-glucose (Glc) and L-glutamine (Q) more efficiently for their development. This increased nutritional dependency of malignant cells has been commonly employed in various in vitro and in vivo models of anticancer therapies. This study utilized a combination of a low dose (25 μg mL^-1) of S2, a phytosynthesized gold nanoparticle (AuNP) that was previously proven to be non-toxic, and deprivation of extracellular glutamine as an anticancer strategy in the human cervical cancer cell line HeLa. We discovered that 24 h Q deprivation led to a less significant decrease in the viability of HeLa cells while a low dose of S2 caused a non-significant reduction in the viability of HeLa cells. However, combining these two treatments resulted in highly significant inhibition of cell growth, as measured by the MTT test and morphological examination. Glutamine starvation in HeLa cells was found to induce cellular uptake of S2 via clathrin-mediated endocytosis, thus facilitating the improved antitumor effects of the combined treatment. Flow cytometry-based assays using fluorescent probes H₂DCFDA and MitoSOX Red confirmed that this combination therapy involved the development of oxidative stress conditions owing to a surplus of cytosolic reactive oxygen species (cytoROS) and mitochondrial superoxide (mtSOX) generation. Furthermore, the investigated combinatorial treatment also indicated mitochondrial inactivity and disintegration, as evidenced by the drop in the mitochondrial membrane potential (Δψ_m) and the decrease in the mitochondrial mass (mtMass) in a flow-cytometric assay utilizing the probes. Tetramethylrhodamine ethyl ester and MitoTracker Green FM, respectively. Cell cycle arrest in the G0/G1 phase, induction of cell death via apoptosis/necrosis, and inhibition of migration capacities of HeLa cells were also seen after the combined treatment. Thus, this research provides insight into a new combinatorial approach for reducing the dose of nanoparticles and increasing their efficacy to better inhibit the growth of human cervical cancer cells by leveraging their extracellular glutamine dependence.

Identification of Novel Cytochrome C1 (CYC1) Gene Expression in Oral Squamous Cell Carcinoma- An Evaluative Study

Introduction

Cytochrome C1 (CYC1) is an important subunit of mitochondrial complex III and plays a vital role in oxidative phosphorylation (OXPHOS) and reactive oxygen species generation. Overexpression of the CYC1 gene has been implicated in cancer development and its prognosis previously, but unexplored in head-and-neck squamous cell carcinomas (HNSCC), especially oral squamous cell carcinoma (OSCC).

Materials and Methods

CYC1 m-RNA expression and gene alterations were assessed using the Cancer Genome Atlas dataset in HNSCC and validated in OSCC tissues using real-time polymerase chain reaction (RT-PCR). The protein-protein interaction (PPI) network and functional enrichment pathways were also analysed.

Results

A thorough analysis of the TCGA (The Cancer Genome Atlas) database revealed that CYC1 was overexpressed in the HNSCC cases and the increased expression correlated with several parameters which involve the prediction of advanced diseases such as histopathological grade, tumour-node-metastasis staging, and nodal metastases (P < 0.05). The expression of CYC1 was validated using RT-PCR showing significant upregulation (P < 0.05) in OSCC tissue samples compared to the normal tissue counterparts. PPI network and functional analysis show the prominent role of CYC1 in OXPHOS, especially in electron transport chain III complex regulation.

Discussion

The study revealed that CYC1 is highly expressed in HNSCC, and is validated in the OSCC patient tissue samples compared to the normal counterparts and associated with advanced disease stages and grade of the tumour. CYC1 could be a novel promising therapeutic and prognostic marker in HNSCC, especially in OSCC.

The Apoptosis of Liver Cancer Cells Promoted by Curcumin/TPP-CZL Nanomicelles With Mitochondrial Targeting Function

The mitochondrion is one of the most important cellular organelles, and many drugs work by acting on mitochondria. Curcumin (Cur)-induced apoptosis of HepG2 in liver cancer cells is closely related to the function of inhibiting mitochondria. However, the mitochondrion-targeting curcumin delivery system was rarely been reported. It is important to develop a high-efficiency mitochondrion-targeting curcumin vector that can deliver curcumin into mitochondria directly. Here, a special mitochondrion-targeting delivery system based on triphenylphosphine bromide (TPP)-chitosan-g-poly-(N-3-carbobenzyloxy-l-lysine) (CZL) with TPP functional on the surface is designed to perform highly efficient mitochondria-targeting delivery for effective liver cancer cell killing in vitro. The TEM images showed that the nanomicelles were spherical; the results of fluorescence test showed that TPP-CZL nanomicelles could promote the cellular uptake of drugs and finally targeted to the mitochondria. The results of cell survival rate and Hoechst staining showed that curcumin/TPP-CZL nanomicelles could promote the apoptosis of liver cancer cells. Curcumin/TPP-CZL nanomicelles could significantly reduce the mitochondrial membrane potential, increase the expression of pro apoptotic protein Bcl-2, and reduce the expression of antiapoptotic Bax protein, and these results were significantly better than curcumin/CZL nanomicelles and curcumin. It is a potential drug delivery system with high efficiency to target mitochondria of liver cancer cells.

Rational Designs at the Forefront of Mitochondria-Targeted Gene Delivery: Recent Progress and Future Perspectives

Mitochondria play an essential role in cellular metabolism and generate energy in cells. To support these functions, several proteins are encoded in the mitochondrial DNA (mtDNA). The mutation of mtDNA causes mitochondrial dysfunction and ultimately results in a variety of inherited diseases. To date, gene delivery systems targeting mitochondria have been developed to ameliorate mtDNA mutations. However, applications of these strategies in mitochondrial gene therapy are still being explored and optimized. Thus, from this perspective, we herein highlight recent mitochondria-targeting strategies for gene therapy and discuss future directions for effective mitochondria-targeted gene delivery.

Construction of Hierarchical-Targeting pH-Sensitive Liposomes to Reverse Chemotherapeutic Resistance of Cancer Stem-like Cells

Cancer stem-like cells (CSLCs) have been considered to be one of the main problems in tumor treatment owing to high tumorigenicity and chemotherapy resistance. In this study, we synthesized a novel mitochondria-target derivate, triphentlphosphonium-resveratrol (TPP-Res), and simultaneously encapsulated it with doxorubicin (Dox) in pH-sensitive liposomes (PSL (Dox/TPP-Res)), to reverse chemotherapeutic resistance of CSLCs. PSL (Dox/TPP-Res) was approximately 165 nm in size with high encapsulation efficiency for both Dox and TPP-Res. Cytotoxicity assay showed that the optimal synergistic effect was the drug ratio of 1:1 for TPP-Res and Dox. Cellular uptake and intracellular trafficking assay indicated that PSL (Dox/TPP-Res) could release drugs in acidic endosomes, followed by mitochondrial targeting of TPP-Res and nucleus transports for Dox. The mechanisms for reversing the resistance in CSLCs were mainly attributed to a synergistic effect for reduction of mitochondrial membrane potential, activation of caspase cascade reaction, reduction of ATP level and suppression of the Wnt/β-catenin pathway. Further, in vivo assay results demonstrated that the constructed liposomes could efficiently accumulate in the tumor region and possess excellent antineoplastic activity in an orthotopic xenograft tumor model with no evident systemic toxicity. The above experimental results determined that PSL (Dox/TPP-Res) provides a new method for the treatment of heterogenecity tumors.

Fruiting body polysaccharides of Hericium erinaceus induce apoptosis in human colorectal cancer cells via ROS generation mediating caspase-9-dependent signaling pathways

The fruiting bodies of Hericium erinaceus (Bull.) Pers. are commonly used in China in the treatment of digestive system diseases. In this work, the polysaccharides from the fruiting bodies of Hericium erinaceus (HEFPs) were extracted, and their effects on human colorectal cancer cells (HCT-116 and DLD1) were investigated in vitro. Our results showed that HEFPs were mainly composed of arabinose, galactose, glucose, and mannose at a molar ratio of 8.99 : 11.15 : 1.2 : 1.97. They significantly inhibited the growth of these cells by inducing apoptosis by the modulation of Bax and Bcl-2 expression, which in turn induced the loss of mitochondrial membrane potential, leading to the activation of cleaved-caspase-9 and cleaved-caspase-3. These results suggested that HEFPs induced apoptosis via the caspase-9-depedent intrinsic mitochondrial pathway. Furthermore, HEFPs increased the level of reactive oxygen species (ROS) in HCT-116 and DLD1 cells. The addition of the antioxidant N-acetyl-l-cysteine reduced the ability of HEFPs to trigger the intrinsic mitochondrial pathway, indicating the role of ROS generation in the upstream pathway of HEFP-induced apoptosis. Therefore, the results described in this study could be of interest for further studies in finding functional foods or alternative therapeutic agents against colorectal cancer.

Mitochondria: Insights into Crucial Features to Overcome Cancer Chemoresistance

Mitochondria are key regulators of cell survival and are involved in a plethora of mechanisms, such as metabolism, Ca²⁺ signaling, reactive oxygen species (ROS) production, mitophagy and mitochondrial transfer, fusion, and fission (known as mitochondrial dynamics). The tuning of these processes in pathophysiological conditions is fundamental to the balance between cell death and survival. Indeed, ROS overproduction and mitochondrial Ca²⁺ overload are linked to the induction of apoptosis, while the impairment of mitochondrial dynamics and metabolism can have a double-faceted role in the decision between cell survival and death. Tumorigenesis involves an intricate series of cellular impairments not yet completely clarified, and a further level of complexity is added by the onset of apoptosis resistance mechanisms in cancer cells. In the majority of cases, cancer relapse or lack of responsiveness is related to the emergence of chemoresistance, which may be due to the cooperation of several cellular protection mechanisms, often mitochondria-related. With this review, we aim to critically report the current evidence on the relationship between mitochondria and cancer chemoresistance with a particular focus on the involvement of mitochondrial dynamics, mitochondrial Ca²⁺ signaling, oxidative stress, and metabolism to possibly identify new approaches or targets for overcoming cancer resistance.

Human ClpP protease, a promising therapy target for diseases of mitochondrial dysfunction

Human caseinolytic protease P (HsClpP), an ATP-dependent unfolding peptidase protein in the mitochondrial matrix, controls protein quality, regulates mitochondrial metabolism, and maintains the integrity and enzyme activity of the mitochondrial respiratory chain (RC). Studies show that abnormalities in HsClpP lead to mitochondrial dysfunction and various human diseases. In this review, we provide a comprehensive overview of the structure and biological function of HsClpP, and the involvement of its dysexpression or mutation in mitochondria for a panel of important human diseases. We also summarize the structural types and binding modes of known HsClpP modulators. Finally, we discuss the challenges and future directions of HsClpP targeting as promising approach for the treatment of human diseases of mitochondrial origin.

Endocytosis and Organelle Targeting of Nanomedicines in Cancer Therapy

Nanomedicines (NMs) have played an increasing role in cancer therapy as carriers to efficiently deliver therapeutics into tumor cells. For this application, the uptake of NMs by tumor cells is usually a prerequisite to deliver the cargo to intracellular locations, which mainly relies on endocytosis. NMs can enter cells through a variety of endocytosis pathways. Different endocytosis pathways exhibit different intracellular trafficking routes and diverse subcellular localizations. Therefore, a comprehensive understanding of endocytosis mechanisms is necessary for increasing cellular entry efficiency and to trace the fate of NMs after internalization. This review focuses on endocytosis pathways of NMs in tumor cells, mainly including clathrin- and caveolae-mediated endocytosis pathways, involving effector molecules, expression difference of those molecules between normal and tumor cells, as well as the intracellular trafficking route of corresponding endocytosis vesicles. Then, the latest strategies for NMs to actively employ endocytosis are described, including improving tumor cellular uptake of NMs by receptor-mediated endocytosis, transporter-mediated endocytosis and enabling drug activity by changing intracellular routes. Finally, active targeting strategies towards intracellular organelles are also mentioned. This review will be helpful not only in explicating endocytosis and the trafficking process of NMs and elucidating anti-tumor mechanisms inside the cell but also in rendering new ideas for the design of highly efficacious and cancer-targeted NMs.

Transcriptome Investigation and In Vitro Verification of Curcumin-Induced HO-1 as a Feature of Ferroptosis in Breast Cancer Cells

Ferroptosis is a form of oxidative cell death and has become a chemotherapeutic target for cancer treatment. Curcumin (CUR), a well-known cancer inhibitor, significantly inhibits the viability of breast cancer cells. Through transcriptomic analysis and flow cytometry experiments, it was found that after 48 hours of treatment of breast cancer cells at its half maximal inhibitory concentration (IC50), curcumin suppressed the viability of cancer cells via induction of ferroptotic death. Use of the ferroptosis inhibitor ferrostatin-1 and the iron chelator deferoxamine rescued cell death induced by curcumin. Furthermore, in subsequent cell validation experiments, the results showed that curcumin caused marked accumulation of intracellular iron, reactive oxygen species, lipid peroxides, and malondialdehyde, while glutathione levels were significantly downregulated. These changes are all manifestations of ferroptosis. Curcumin upregulates a variety of ferroptosis target genes related to redox regulation, especially heme oxygenase-1 (HO-1). Using the specific inhibitor zinc protoporphyrin 9 (ZnPP) to confirm the above experimental results showed that compared to the curcumin treatment group, treatment with ZnPP not only significantly improved cell viability but also reduced the accumulation of intracellular iron ions and other ferroptosis-related phenomena. Therefore, these data demonstrate that curcumin triggers the molecular and cytological characteristics of ferroptosis in breast cancer cells, and HO-1 promotes curcumin-induced ferroptosis.

On the nature of ceramide-mitochondria interactions - Dissection using comprehensive mitochondrial phenotyping

Sphingolipids are a unique class of lipids owing to their non-glycerol-containing backbone, ceramide, that is constructed from a long-chain aliphatic amino alcohol, sphinganine, to which a fatty acid is attached via an amide bond. Ceramide plays a star role in the initiation of apoptosis by virtue of its interactions with mitochondria, a control point for a downstream array of signaling cascades culminating in apoptosis. Many pathways converge on mitochondria to elicit mitochondrial outer membrane permeabilization (MOMP), a step that corrupts bioenergetic service. Although much is known regarding ceramides interaction with mitochondria and the ensuing cell signal transduction cascades, how ceramide impacts the elements of mitochondrial bioenergetic function is poorly understood. The objective of this review is to introduce the reader to sphingolipid metabolism, present a snapshot of mitochondrial respiration, elaborate on ceramides convergence on mitochondria and the upstream players that collaborate to elicit MOMP, and introduce a mitochondrial phenotyping platform that can be of utility in dissecting the fine-points of ceramide impact on cellular bioenergetics.

Liposome as drug delivery system enhance anticancer activity of iridium (III) complex

Herein an Ir(III) complex [Ir(Hppy)₂(HMNPIP)](PF₆) (Ir1, Hppy = 2-phenylpyridine, HMNPIP = 2-(1H-imidazo[4,5-f][1, 10]phenanthroline-3-yl)-6-methoxy-4-nitrophenol) was prepared and characterized. Due to the low anticancer activity of Ir1 when administered free drug, we prepared a liposome Ir1Lipo encapsulated form of Ir1 to improve the antitumor effect, furthermore, we explored the antitumor mechanism of both forms in vitro experiments on HepG2 cells. We investigated the inhibitory efficiency of Ir1 and Ir1Lipo on cell viability and proliferation using MTT (MTT = 3-(4,5-dimethylthiazole)-2,5-diphenltetraazolium bromide) and colony-forming assay. Intracellular accumulation of reactive oxygen species (ROS) was examined using a fluorescence microscope (High Content Screening System, ImageXpress Micro XLS System, Molecular Devices LLC, Sunnyvale, CA), programmed cell death cells stained with acridine orange/ethidium bromide (AO/EB) using flow cytometry detection and western blot have been performed. An in vivo study where HepG2 cells were transplanted into nude nice as xenografts. Tumour volume and body weight were monitored during the 10 days of administration. After encapsulation in liposomes Ir1Lipo displayed high potency against a variety of tumour cells in vitro, especially against HepG2 (IC₅₀ = 4.6 ± 0.5 μM). Mechanism studies indicated that Ir1Lipo initiated apoptosis by generating intracellular ROS that regulate lysosomal-mitochondrial dysfunction, followed by microtubule disruption that subsequently leads to a G0/G1 phase of cell cycle arrest. Additionally, Ir1Lipo significantly curbed tumour growth in nude mice. The tumour inhibitory rate was 51.2% (5.6 mg/kg). Therefore, liposome as a drug delivery system greatly enhances anticancer activity of Ir1 by a factor of relatively minor side effects.

The Role of Mitochondrial Dynamics and Mitophagy in Carcinogenesis, Metastasis and Therapy

Mitochondria are key cellular organelles and play vital roles in energy metabolism, apoptosis regulation and cellular homeostasis. Mitochondrial dynamics refers to the varying balance between mitochondrial fission and mitochondrial fusion that plays an important part in maintaining mitochondrial homeostasis and quality. Mitochondrial malfunction is involved in aging, metabolic disease, neurodegenerative disorders, and cancers. Mitophagy, a selective autophagy of mitochondria, can efficiently degrade, remove and recycle the malfunctioning or damaged mitochondria, and is crucial for quality control. In past decades, numerous studies have identified a series of factors that regulate mitophagy and are also involved in carcinogenesis, cancer cell migration and death. Therefore, it has become critically important to analyze signal pathways that regulate mitophagy to identify potential therapeutic targets. Here, we review recent progresses in mitochondrial dynamics, the mechanisms of mitophagy regulation, and the implications for understanding carcinogenesis, metastasis, treatment, and drug resistance.

A Novel Benzofuran Derivative Moracin N Induces Autophagy and Apoptosis Through ROS Generation in Lung Cancer

Introduction

The leaves of Morus alba L is a traditional Chinese medicine widely applied in lung diseases. Moracin N (MAN), a secondary metabolite extracted form the leaves of Morus alba L, is a potent anticancer agent. But its molecular mechanism remains unveiled.

Objective

In this study, we aimed to examine the effect of MAN on human lung cancer and reveal the underlying molecular mechanism.

Methods

MTT assay was conducted to measure cell viability. Annexin V-FITC/PI staining was used to detect cell apoptosis. Confocal microscope was performed to determine the formation of autophagosomes and autolysosomes. Flow cytometry was performed to quantify cell death. Western blotting was used to determine the related-signaling pathway.

Results

In the present study, we demonstrated for the first time that MAN inhibitd cell proliferation and induced cell apoptosis in human non-small-cell lung carcinoma (NSCLC) cells. We found that MAN treatment dysregulated mitochondrial function and led to mitochondrial apoptosis in A549 and PC9 cells. Meanwhile, MAN enhanced autophagy flux by the increase of autophagosome formation, the fusion of autophagsomes and lysosomes and lysosomal function. Moreover, mTOR signaling pathway, a classical pathway regualting autophagy, was inhibited by MAN in a time- and dose-dependent mannner, resulting in autophagy induction. Interestingly, autophagy inhibition by CQ or Atg5 knockdown attenuated cell apoptosis by MAN, indicating that autophagy serves as cell death. Furthermore, autophagy-mediated cell death by MAN can be blocked by reactive oxygen species (ROS) scavenger NAC, indicating that ROS accumulation is the inducing factor of apoptosis and autophagy. In summary, we revealed the molecular mechanism of MAN against lung cancer through apoptosis and autophagy, suggesting that MAN might be a novel therapeutic agent for NSCLC treatment.

Stepwise dual targeting and dual responsive polymer micelles for mitochondrion therapy

Methods to selectively destroy mitochondria of tumor cells and induce cell apoptosis with nanomedicine constitute challenges in cancer therapy. In the present study, we develop cell membrane/mitochondria dual targeting and pH/redox dual responsive nanoparticles for mitochondrion therapy. The nanoparticles are fabricated by the self-assembly of triphenylphosphonium (TPP) grafted poly(ethylene glycol)(PEG)-poly(d,l-lactide)(PLA) copolymers (TPP-PEG-ss-PLA) using disulfide bonds as the intermediate linkers. To shield the surface positive charge of the nanoparticles from TPP composition, chondroitin sulfate (CS) is employed to coat the nanoparticles, and this prolongs blood circulation while endowing an active targeting ability to the cell membrane. In acidic lyso-somes/endosomes, the negatively charged CS layer falls away to expose the TPP component. Subsequently, in the cyto-plasm, the nanoparticles can anchor to the mitochondrial outer membrane by TPP-mediated targeting, thereby inducing a decrease in the membrane potential and opening of the permeability transition pore. Thus, the overproduction of ROS in the mitochondria promotes cell apoptosis. The released DOX directly diffuse into the mitochondria, thereby resulting in mito-chondrial DNA damage. Therefore, the nanoparticles exhibit significant potential in terms of a new avenue for mitochondrion therapy in cancer treatment.

The Role of Mitochondrial Calcium Signaling in the Pathophysiology of Cancer Cells

The pioneering work of Richard Altman on the presence of mitochondria in cells set in motion a field of research dedicated to uncovering the secrets of the mitochondria. Despite limitations in studying the structure and function of the mitochondria, advances in our understanding of this organelle prompted the development of potential treatments for various diseases, from neurodegenerative conditions to muscular dystrophy and cancer. As the powerhouses of the cell, the mitochondria represent the essence of cellular life and as such, a selective advantage for cancer cells. Much of the function of the mitochondria relies on Ca²⁺ homeostasis and the presence of effective Ca²⁺ signaling to maintain the balance between mitochondrial function and dysfunction and subsequently, cell survival. Ca²⁺ regulates the mitochondrial respiration rate which in turn increases ATP synthesis, but too much Ca²⁺ can also trigger the mitochondrial apoptosis pathway; however, cancer cells have evolved mechanisms to modulate mitochondrial Ca²⁺ influx and efflux in order to sustain their metabolic demand and ensure their survival. Therefore, targeting the mitochondrial Ca²⁺ signaling involved in the bioenergetic and apoptotic pathways could serve as potential approaches to treat cancer patients. This chapter will review the role of Ca²⁺ signaling in mediating the function of the mitochondria and its involvement in health and disease with special focus on the pathophysiology of cancer.

The effect of anodal/cathodal biphasic electrical stimulation on insulin release

We studied the effects of electrical stimulation on insulin release from rat insulinoma (INS-1) cells. The anodal/cathodal biphasic stimulation (ACBPS) electrical waveform resulted in a voltage- and stimulation duration-dependent increase in insulin release. ACBPS elicited insulin release both in the presence and absence of glucose. Basal and ACBPS-induced insulin secretion could be inhibited by mitochondrial poisons and calcium channel blockers, indicating that insulin release was dependent on adenosine triphosphate (ATP) and the influx of calcium. ACBPS parameters that released insulin caused no detectable plasma membrane damage or cytotoxicity, although temporary morphological changes could be observed immediately after ACBPS. ACBPS did not alter the plasma membrane transmembrane potential but did cause pronounced uptake of MitoTracker Red into the mitochondrial membrane, indicating an increased mitochondrial membrane potential. While the ATP:ADP ratio after ACBPS did not change, the guanosine triphosphate (GTP) levels increased and increased GTP levels have previously been associated with insulin release in INS-1 cells. These results provide evidence that ACBPS can have significant biological effects on cells. In the case of INS-1 cells, ACBPS promotes insulin release without causing cytotoxicity.

Cell-penetrating peptide: a means of breaking through the physiological barriers of different tissues and organs

The selective infiltration of cell membranes and tissue barriers often blocks the entry of most active molecules. This natural defense mechanism prevents the invasion of exogenous substances and limits the therapeutic value of most available molecules. Therefore, it is particularly important to find appropriate ways of membrane translocation and therapeutic agent delivery to its target site. Cell penetrating peptides (CPPs) are a group of short peptides harnessed in this condition, possessing a significant capacity for membrane transduction and could be exploited to transfer various biologically active cargoes into the cells. Since their discovery, CPPs have been employed for delivery of a wide variety of therapeutic molecules to treat various disorders including cranial nerve involvement, ocular inflammation, myocardial ischemia, dermatosis and cancer. The promising results of CPPs-derived therapeutics in various tumor models demonstrated a potential and worthwhile scope of CPPs in chemotherapy. This review describes the detailed description of CPPs and CPPs-assisted molecular delivery against various tissues and organs disorders. An emphasis is focused on summarizing the novel insights and achievements of CPPs in surmounting the natural membrane barriers during the last 5 years.

Mitochondria-Targeted Two-Photon Fluorescent Photosensitizers for Cancer Cell Apoptosis via Spatial Selectability

Organelle-targeted photosensitizers have been reported to be effective cell apoptosis agents. Mitochondria is recognized as an ideal target for cancer treatment due to its central role in oxidative metabolism and apoptosis. Meanwhile, two-photon (TP) fluorescence microscopy has become a powerful tool for fluorescence imaging in biological events based on its minimizing photodamage/photobleaching and intrinsic 3D resolution in deep tissues and in vivo. In this study, a series of novel mitochondrial-targeted TP fluorescent photosensitizers (TP-tracers) are designed, synthesized, and systematically investigated. These TP-tracers exhibit extraordinary anti-interference capability among different cations, anions, and amino acids as well as the insensitivity to the changes of pH and complex biological environments. TP-tracers are further used in fluorescence living cells, Drosophila brains, and zebrafish imaging with low cytotoxicity, excellent mitochondria-targeting, and TP properties. The results demonstrate efficient mitochondria-targeting cell selective apoptosis based on TP-activated cancer cells with highly single cell selectivity, and the pharmacokinetic study reveals that MitoY2 does not have accumulation in rats. It is believed that these molecules hold great potential in TP-related smart phototherapy.

The impact of aneuploidy on cellular homeostasis

Genomic instability is a common feature of tumours that has a wide range of disruptive effects on cellular homeostasis. In this review we briefly discuss how instability comes about, then focus on the impact of gain or loss of DNA (aneuploidy) on oxidative stress. We discuss several mechanisms that lead from aneuploidy to the production of reactive oxygen species, including the effects on protein complex stoichiometry, endoplasmic reticulum stress and metabolic disruption. Each of these are involved in positive feedback loops that amplify relatively minor genetic changes into major cellular disruption or cell death, depending on the capacity of the cell to induce antioxidants or processes such as mitophagy that can moderate the disruption. Finally we examine the direct effects of reactive oxygen species on mitosis and how oxidative stress can compromise centrosome number, cytoskeletal integrity and signalling processes that are vital for mitotic fidelity.

Contribution of Mitochondrial Ion Channels to Chemo-Resistance in Cancer Cells

Mitochondrial ion channels are emerging oncological targets, as modulation of these ion-transporting proteins may impact on mitochondrial membrane potential, efficiency of oxidative phosphorylation and reactive oxygen production. In turn, these factors affect the release of cytochrome c, which is the point of no return during mitochondrial apoptosis. Many of the currently used chemotherapeutics induce programmed cell death causing damage to DNA and subsequent activation of p53-dependent pathways that finally leads to cytochrome c release from the mitochondrial inter-membrane space. The view is emerging, as summarized in the present review, that ion channels located in this organelle may account in several cases for the resistance that cancer cells can develop against classical chemotherapeutics, by preventing drug-induced apoptosis. Thus, pharmacological modulation of these channel activities might be beneficial to fight chemo-resistance of different types of cancer cells.

Autophagic and Apoptotic Pathways as Targets for Chemotherapy in Glioblastoma

Glioblastoma multiforme is the most malignant and aggressive type of brain tumor, with a mean life expectancy of less than 15 months. This is due in part to the high resistance to apoptosis and moderate resistant to autophagic cell death in glioblastoma cells, and to the poor therapeutic response to conventional therapies. Autophagic cell death represents an alternative mechanism to overcome the resistance of glioblastoma to pro-apoptosis-related therapies. Nevertheless, apoptosis induction plays a major conceptual role in several experimental studies to develop novel therapies against brain tumors. In this review, we outline the different components of the apoptotic and autophagic pathways and explore the mechanisms of resistance to these cell death pathways in glioblastoma cells. Finally, we discuss drugs with clinical and preclinical use that interfere with the mechanisms of survival, proliferation, angiogenesis, migration, invasion, and cell death of malignant cells, favoring the induction of apoptosis and autophagy, or the inhibition of the latter leading to cell death, as well as their therapeutic potential in glioma, and examine new perspectives in this promising research field.

Silibinin to improve cancer therapeutic, as an apoptotic inducer, autophagy modulator, cell cycle inhibitor, and microRNAs regulator

Silibinin is a natural plant polyphenol with high antioxidant and anticancer properties, which causes broad-spectrum efficacy against cancer, including cell cycle arrest and apoptosis in most cancer cell types. Silibinin, by modulating the apoptosis, cell cycle progression and autophagic pathways in various cellular and molecular routs might be used to design more effective anticancer strategies. Silibinin also regulates aberrant miRNAs expression linked to many aspects of cell biology in cancer. Maybe the most interesting aspect of silibinin is its ability to trigger multiple cellular signaling pathways to induce a particular biologic effect in various cell types. This review discusses investigations supporting the ability of silibinin to be as a natural modulator of involved cellular biological events in cancer progression. In this review, we introduce the salient features of silibinin therapy to optimize clinical outcomes for oncology patients. The goal of the treatments is to make it possible to eliminate the tumor with the minimum side effects and cure the patient in the early stage cancer. Therefore, plant extracts such as silibinin can be included in the treatments.

New highlights on the health-improving effects of sulforaphane

In this paper, we review recent evidence about the beneficial effects of sulforaphane (SFN), which is the most studied member of isothiocyanates, on both in vivo and in vitro models of different diseases, mainly diabetes and cancer. The role of SFN on oxidative stress, inflammation, and metabolism is discussed, with emphasis on those nuclear factor E2-related factor 2 (Nrf2) pathway-mediated mechanisms. In the case of the anti-inflammatory effects of SFN, the point of convergence seems to be the downregulation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), with the consequent amelioration of other pathogenic processes such as hypertrophy and fibrosis. We emphasized that SFN shows opposite effects in normal and cancer cells at many levels; for instance, while in normal cells it has protective actions, in cancer cells it blocks the induction of factors related to the malignity of tumors, diminishes their development, and induces cell death. SFN is able to promote apoptosis in cancer cells by many mechanisms, the production of reactive oxygen species being one of the most relevant ones. Given its properties, SFN could be considered as a phytochemical at the forefront of natural medicine.

Mitochondrial Targeted Therapies: Where Do We Stand in Mental Disorders?

The neurobiology of psychiatric disorders is still unclear, although changes in multiple neuronal systems, specifically the dopaminergic, glutamatergic, and gamma-aminobutyric acidergic systems as well as abnormalities in synaptic plasticity and neural connectivity, are currently suggested to underlie their pathophysiology. A growing body of evidence suggests multifaceted mitochondrial dysfunction in mental disorders, which is in line with their role in neuronal activity, growth, development, and plasticity. In this review, we describe the main endeavors toward development of treatments that will enhance mitochondrial function and their transition into clinical use in congenital mitochondrial diseases and chronic disorders such as types 1 and 2 diabetes, cardiovascular disorders, and cancer. In addition, we discuss the relevance of mitochondrial targeted treatments to mental disorders and their potential to become a novel therapeutic strategy that will improve the efficiency of the current treatments.

Mitochondria: promising organelle targets for cancer diagnosis and treatment

Mitochondrial-mediated tumor monitoring provides a new perspective on mitochondria-based therapy.

Critical Overview of the Use of Ru(II) Polypyridyl Complexes as Photosensitizers in One-Photon and Two-Photon Photodynamic Therapy

Photodynamic Therapy (PDT) is an emerging technique to treat certain types of cancer, bacterial, fungal, and viral infections, and skin diseases. In past years, different research groups developed new ruthenium-containing photosensitizers (PSs) with tuned photophysical and biological properties to better fit the requirements of PDT. In this Account, we report and discuss the latest results in this research area, emphasizing particularly our own research. For example, inspired by the DNA intercalating complex [Ru(bpy)₂(dppz)]²⁺ (bpy = 2,2'-bipyridine; dppz = (dipyrido[3,2-a:2',3'-c]phenazine), a series of ruthenium complexes bearing differently functionalized dppz ligands were synthesized to target DNA. The introduction of the substituents on the dppz ligand did not reduce much the affinity of the complexes to DNA but highly affected their cellular uptake. The most effective complex in this series, [Ru(bpy)₂(dppz-7-OMe)]²⁺, showed IC₅₀ values in the low micromolar range against several types of cancer cells upon light irradiation and, importantly, a high phototoxic index (PI) of >150. This value is comparable to or even better than several PSs used in clinics under comparable experimental conditions. This compound was found to localize in the nucleus and to induce DNA damage in HeLa cells upon light irradiation. Interestingly, cells in the mitotic phase were found to be more affected and to have a different mechanism of cell death (apoptosis) upon light irradiation than those in the interphase (paraptosis). To take advantage of that, the PS was combined with a cell cycle inhibitor to synchronize cells in the mitotic phase, further improving the phototoxicity by a factor of 3.6. In addition, our group recently demonstrated that [Ru(bphen)₂(benzene-1,2-dislufinate)] (bphen = 4,7-diphenyl-1,10-phenanthroline) localizes in mitochondria and has an IC₅₀ value of 0.62 μM with a PI of over 80 in HeLa cells upon light irradiation at 420 nm. Interestingly, this complex was also found to efficiently kill Gram-positive Staphylococcus aureus under light irradiation. Antimicrobial PDT (aPDT) is another field of research where Ru(II) polypyridyl complexes can play an interesting role to fight antibiotics resistance. [Ru(dqpCO₂Me)(ptpy)]²⁺ (dqpCO₂Me = 4-methylcarboxy-2,6-di(quinolin-8-yl)pyridine), ptpy = 4'-phenyl-2,2':6',2″-terpyridine) is additionally efficient against Gram-negative Escherichia coli. The efficacy of positively charged Ru(II) PSs is related to their affinity to the negatively charged membrane of Gram-negative bacteria. A drawback of many Ru(II) polypyridyl PSs is their low absorption in the biological optical window (600-900 nm) where light penetration depth into tissue is the highest. The lowest energy transition in the UV/Vis spectra of Ru(II) polypyridyl complexes is usually a metal-to-ligand charge-transfer band. To shift the absorption into this range, tuning of the ligand system, for example, by extending π-systems, has been described in the literature. Another approach to make excitation in the optical biological window possible is Two-Photon Absorption (2PA). High photon density is needed and usually confocal laser beams are used for excitation. In collaboration with the Chao group, a series of homoleptic Ru(II) complexes bearing tertiary alkyl ammonium substituted bipyridine ligands with two photon cross sections between 185 and 250 GM at around 800 nm was tested in vitro. They showed IC₅₀ values in the micromolar range and PIs between 103 and 313. The highly positive-charged complexes were found to enter the cell via endocytosis and to target lysosomes. Studies on 3D tumor cell spheroids, a model closer to real tumors than commonly used 2D cell monolayers, were also performed. It could be demonstrated that 2P-PDT treatment with 800 nm laser irradiation was significantly more effective than that with 450 nm laser irradiation.

A novel Fer/FerT targeting compound selectively evokes metabolic stress and necrotic death in malignant cells

Disruption of the reprogrammed energy management system of malignant cells is a prioritized goal of targeted cancer therapy. Two regulators of this system are the Fer kinase, and its cancer cell specific variant, FerT, both residing in subcellular compartments including the mitochondrial electron transport chain. Here, we show that a newly developed inhibitor of Fer and FerT, E260, selectively evokes metabolic stress in cancer cells by imposing mitochondrial dysfunction and deformation, and onset of energy-consuming autophagy which decreases the cellular ATP level. Notably, Fer was also found to associate with PARP-1 and E260 disrupted this association thereby leading to PARP-1 activation. The cooperative intervention with these metabolic pathways leads to energy crisis and necrotic death in malignant, but not in normal human cells, and to the suppression of tumors growth in vivo. Thus, E260 is a new anti-cancer agent which imposes metabolic stress and cellular death in cancer cells.

The tyrosine-kinases Fer/FerT associate with the mitochondrial electron transport chain in cancer cells supporting their metabolic reprogramming. Here the authors discover a compound that disrupts Fer /FerT activity and selectively induces cell death of cancer cell lines displaying anti-tumor activity in vivo.

Synergistic Activity of an Antimetabolite Drug and Tyrosine Kinase Inhibitors against Breast Cancer Cells

Antimetabolite drugs, including the adenosine deaminase inhibitor cladribine, have been shown to induce apoptosis in a variety of cancer cells, and have been widely used in clinical trials of various cancers in conjunction with tyrosine kinase inhibitors (TKIs). Combination treatment with cladribine and gefitinib or dasatinib is expected to have a synergistic inhibitory effect on breast cancer cell growth. Our results demonstrated that the combination treatment had synergistic activity against human breast cancer (MCF-7) cells, enhanced G₂/M cell arrest and reactive oxygen species (ROS) generation, and increased the loss of mitochondrial membrane potential and cell apoptosis. In addition, the combination treatment decreased Bcl-2 expression. Our results demonstrated that cladribine in combination with gefitinib or dasatinib exerted synergistic anticancer effects on MCF-7 cells by inducing cell cycle arrest, ROS production and apoptosis through the mitochondria-mediated intrinsic pathway.

Teaching the basics of cancer metabolism: Developing antitumor strategies by exploiting the differences between normal and cancer cell metabolism

This review of the basics of cancer metabolism focuses on exploiting the metabolic differences between normal and cancer cells. The first part of the review covers the different metabolic pathways utilized in normal cells to generate cellular energy, or ATP, and the glycolytic intermediates required to build the cellular machinery. The second part of the review discusses aerobic glycolysis, or the Warburg effect, and the metabolic reprogramming involving glycolysis, tricarboxylic acid cycle, and glutaminolysis in the context of developing targeted inhibitors in cancer cells. Finally, the selective targeting of cancer mitochondrial metabolism using positively charged lipophilic compounds as potential therapeutics and their ability to mitigate the toxic side effects of conventional chemotherapeutics in normal cells are discussed. I hope this graphical review will be useful in helping undergraduate, graduate, and medical students understand how investigating the basics of cancer cell metabolism could provide new insight in developing potentially new anticancer treatment strategies.

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Exploiting biochemical and metabolic differences between normal and cancer cells.

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Mitigating reverse Warburg effect in the tumor stroma or microenvironment to hinder tumor growth.

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Dual targeting of glycolysis and mitochondrial metabolism to inhibit tumor cell proliferation.

Direct Pharmacological Targeting of a Mitochondrial Ion Channel Selectively Kills Tumor Cells In Vivo

The potassium channel Kv1.3 is highly expressed in the mitochondria of various cancerous cells. Here we show that direct inhibition of Kv1.3 using two mitochondria-targeted inhibitors alters mitochondrial function and leads to reactive oxygen species (ROS)-mediated death of even chemoresistant cells independently of p53 status. These inhibitors killed 98% of ex vivo primary chronic B-lymphocytic leukemia tumor cells while sparing healthy B cells. In orthotopic mouse models of melanoma and pancreatic ductal adenocarcinoma, the compounds reduced tumor size by more than 90% and 60%, respectively, while sparing immune and cardiac functions. Our work provides direct evidence that specific pharmacological targeting of a mitochondrial potassium channel can lead to ROS-mediated selective apoptosis of cancer cells in vivo, without causing significant side effects.

Interplay of mitochondrial metabolism and microRNAs

Mitochondria are important organelles in cellular metabolism. Several crucial metabolic pathways such as the energy producing electron transport chain or the tricarboxylic acid cycle are hosted inside the mitochondria. The proper function of mitochondria depends on the import of proteins, which are encoded in the nucleus and synthesized in the cytosol. Micro-ribonucleic acids (miRNAs) are short non-coding ribonucleic acid (RNA) molecules with the ability to prevent messenger RNA (mRNA)-translation or to induce the degradation of mRNA-transcripts. Although miRNAs are mainly located in the cytosol or the nucleus, a subset of ~150 different miRNAs, called mitomiRs, has also been found localized to mitochondrial fractions of cells and tissues together with the subunits of the RNA-induced silencing complex (RISC); the protein complex through which miRNAs normally act to prevent translation of their mRNA-targets. The focus of this review is on miRNAs and mitomiRs with influence on mitochondrial metabolism and their possible pathophysiological impact.

CYC1 Predicts Poor Prognosis in Patients with Breast Cancer

Cytochrome c-1 (CYC1) is an important subunit of mitochondrial complex III. However, its role in tumor progression is unclear. We found that CYC1 was upregulated in breast tumor tissues, especially in tissues with lymph node metastasis. And higher expression of CYC1 correlates with poor prognosis in breast cancer patients using online databases and tools. Then we confirmed that CYC1 contributed to metastasis and proliferation in two highly metastatic human breast cancer cell lines. Digging into the biological function of CYC1, we found the activity of mitochondrial complex III decreased due to silencing CYC1. Then the ratio of AMP to ATP increased and AMPK was activated. Analyzing units of other mitochondrial complexes, we did not find knockdown of CYC1 expression reduced expression of any other unit of OXPHOS. We concluded that CYC1 promoted tumor metastasis via suppressing activation of AMPK and contributed to tumor growth via facilitating production of ATP. Our results indicated that CYC1 plays crucial roles in breast cancer progression and might be a predictive factor assisting future patient diagnosis.

Dual subcellular compartment delivery of doxorubicin to overcome drug resistant and enhance antitumor activity

In order to overcome drug resistant and enhance antitumor activity of DOX, a new pH-sensitive micelle (DOX/DQA-DOX@DSPE-hyd-PEG-AA) was prepared to simultaneously deliver DOX to nucleus and mitochondria. Drug released from DOX/DQA-DOX@DSPE-hyd-PEG-AA showed a pH-dependent manner. DOX/DQA-DOX@DSPE-hyd-PEG-AA induced the depolarization of mitochondria and apoptosis in MDA-MB-231/ADR cells and A549 cells, which resulted in the high cytotoxicity of DOX/DQA-DOX@DSPE-hyd-PEG-AA against MDA-MB-231/ADR cells and A549 cells. Confocal microscopy confirmed that DOX/DQA-DOX@DSPE-hyd-PEG-AA simultaneously delivered DQA-DOX and DOX to the mitochondria and nucleus of tumor cell. After DOX/DQA-DOX@DSPE-hyd-PEG-AA was injected to the tumor-bearing nude mice by the tail vein, DOX was mainly found in tumor tissue. But DOX was widely distributed in the whole body after the administration of free DOX. Compared with free DOX, the same dose of DOX/DQA-DOX@DSPE-hyd-PEG-AA significantly inhibited the growth of DOX-resistant tumor in tumor-bearing mice without obvious systemic toxicity. Therefore, dual subcellular compartment delivery of DOX greatly enhanced the antitumor activity of DOX on DOX-resistant tumor. DOX/DQA-DOX@DSPE-hyd-PEG-AA has the potential in target therapy for DOX-resistant tumor.

Amphipathic tail-anchoring peptide is a promising therapeutic agent for prostate cancer treatment

Amphipathic tail-anchoring peptide (ATAP) derived from the human anti-apoptotic protein Bfl-1 is a potent inducer of apoptosis by targeting mitochondria permeability transition. By linking ATAP to an internalizing RGD peptide (iRGD), selective targeting for ATAP to tumor cell was achieved. Confocal fluorescence microscopy showed that ATAP-iRGD could penetrate into cancer cells and distribute along the mitochondria network. ATAP-iRGD triggered mitochondria-dependent cell death through release of cytochrome c. In an effort to promote ATAP-iRGD physiochemical properties to approach clinic application, amino acid substitution and chemical modification were made with ATAP-iRGD to improve its bioactivity. One of these modified peptides, ATAP-iRGD-M8, was with improved stability and aqueous solubility without compromising in vitro cytotoxicity in cultured cancer cells. In vivo xenograft studies with multiple prostate cancer cell lines showed that intravenous administration of ATAP-iRGD-M8 suppressed tumor growth. Toxicological studies revealed that repetitive intravenous administration of ATAP-iRGD-M8 did not produce significant toxicity in the SV129 mice. Our data suggest that ATAP-iRGD-M8 is a promising agent with high selectivity and limited systemic toxicity for prostate cancer treatment.