Mechanistic evaluation of a novel small molecule targeting mitochondria in pancreatic cancer cells

Up-regulation of hypoxia-inducible factor antisense as a novel approach to treat ovarian cancer

Ovarian cancer (OC) is estimated to kill ~14,000 women in the United States in 2019. Current chemotherapies to treat OC initially show therapeutic efficacy but frequently drug resistance develops, at which point therapies with alternative targets are needed. Herein, we are describing a novel approach to sensitize these tumors to standard chemotherapies by increasing the transcription of hypoxia-inducible factor antisense.

Methods: Genome-wide Bru-seq analysis was performed to fully capture the nascent transcriptional signature of OC cells treated with the gp130 inhibitor, SC144. In vitro and in vivo analysis, including characterization of hypoxia and select protein expression, combination with standard of care chemotherapy and antitumor efficacy were performed to assess the biological activity of SC144 on induction of hypoxia in OC cells.

Results: Bru-seq analysis of OVCAR8 cells treated with SC144 shows upregulation of hypoxia related genes. In addition, transcription of hypoxia-inducible factor antisense (HIF1A-AS2) was induced that in turn reduced expression of HIF-1α and simultaneously increased expression of NDRG1. Furthermore, we observed decreased protein levels of EGFR, Met, c-Myc, cyclin D1, MMP-2, MMP-9 and TF, and phosphorylation of Src and P130-cas. SC144-induced alterations of HIF-1α and NDRG1 were also confirmed in prostate cancer cells. Ciclopirox olamine (CPX) induces a cellular transcriptional profile comparable to SC144, suggesting a similar cellular mechanism of action between these two compounds. In addition, SC144 sensitized OC cells to olaparib, carboplatin and cisplatin, and shows better in vivo efficacy than CPX.

Conclusion: Induction of hypoxic stress responses through inhibition of gp130 represents a novel approach to design effective anticancer treatments in combination with standard-of-care chemotherapy in OC and the efficacy reported here strongly supports their clinical development.

pH-Sensitive micelles with mitochondria-targeted and aggregation-induced emission characterization: synthesis, cytotoxicity and biological applications

Subcellular organelle-specific reagents for simultaneous tumor targeting, imaging, and treatment are of enormous interest in cancer therapy. Herein, we present a mitochondria targeting micelle (PEG-AIE-TPP) by conjugating a triphenylphosphonium (TPP) with a fluorogen which can undergo aggregation-induced emission (AIE). At first, the in vitro and in vivo properties of the PEG-AIE-TPP micelle were characterized in detail. It was found that the micelle was reasonably stable at physiological pH and highly sensitive to mildly acidic pH stimuli. Importantly, this micelle could selectively localize and accumulate in the mitochondria, thus generating an aggregation-induced emission (AIE) effect as confirmed by the green fluorescence. Additionally, the micelle exhibited selective cytotoxicity to cancer cells and negligible toxicity to normal cells in vitro. The in vivo imaging and ex vivo imaging results showed that the accumulation tendency of the micelle at the tumor region was obvious. We also further proved the biocompatible, tumor targeting ability and antitumor activity of the PEG-AIE-TPP micelle in MCF-7 tumor-bearing mice. Accordingly, this mitochondria-targeted therapeutic micelle with good stability, biocompatibility, and tumor-targeting and antitumor activity provides a potentially unique tumor-targeted system for cancer therapy.

Precisely Striking Tumors without Adjacent Normal Tissue Damage via Mitochondria-Templated Accumulation

Ignored damage in adjacent normal tissue is fatal especially in some specific tumor therapy such as brain tumors, but it remains a great challenge to conquer due to random drug diffusion and tumor complexity. Herein, we show that hyperthermia in mitochondria, an interparticle plasmonic coupling effect activated nanoevent, selectively strikes tumor tissues without damaging adjacent normal tissues. Spherical gold nanoparticles with a mitochondria-targeting moiety, triphenyl phosphonium, preferentially accumulated inside tumor mitochondria and reached the threshold to activate interparticle plasmonic coupling effect among gold nanoparticles, realizing selective light-thermal conversion and mitochondrial dysfunction in tumor, whereas little hyperthermia and mitochondrial dysfunction were observed in adjacent normal tissues. In vivo study revealed that the temperature increment in tumor tissue with irradiation was nearly 4-fold that in adjacent normal tissue. This subcellular organelle-templated accumulation strategy provides a therapeutic model for highly selective tumor therapy with negligible local side effects.

Self-Assembled Coumarin Nanoparticle in Aqueous Solution as Selective Mitochondrial-Targeting Drug Delivery System

The development of specifically targeted nanoparticles for subcellular organelles modified with a low-molecular-weight organic compound as drug nanocarriers can bring about wide applications in cancer therapy. However, their utility has been hampered by low selectivity, poor biodistribution, and limited efficiency. Herein, we report the aggregation behavior of a triphenylphosphonium-appended coumarin probe (TPP-C) in an aqueous solution and its applications as a mitochondria-targeting probe, and drug delivery carrier, which is a rare example for a low molecular-weight organic compound. The TPP-C formed homogeneous nanoparticles with small diameters in water as well as in mixtures of organic solvents and water. In pure water, the homogeneous nanoparticles induced J-aggregation, whereas in mixed solvents, the homogeneous nanoparticles induced H-aggregation. The luminescence intensities of nanoparticles originated from the aggregation-induced emission (AIE) effect in pure water and also in mixtures of organic solvents and water. These findings indicate that the AIE effect of TPP-C was dependent on the solvent. More interestingly, the TPP-C nanoparticles selectively accumulated in mitochondria. The TPP-C nanoparticles alone exhibited noncytotoxicity toward cancer cells. However, with the encapsulation of the anticancer drug doxorubicin (DOX) into the TPP-C nanoparticles, the DOX was efficiently delivered to the mitochondria. These results indicated that the proposed system demonstrates promise as a platform for future clinical medication, particularly for specific suborganelle-targeted drug delivery systems for cancer therapy.

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.

A metal-containing nucleoside that possesses both therapeutic and diagnostic activity against cancer

Nucleoside transport is an essential process that helps maintain the hyperproliferative state of most cancer cells. As such, it represents an important target for developing diagnostic and therapeutic agents that can effectively detect and treat cancer, respectively. This report describes the development of a metal-containing nucleoside designated Ir(III)-PPY nucleoside that displays both therapeutic and diagnostic properties against the human epidermal carcinoma cell line KB3-1. The cytotoxic effects of Ir(III)-PPY nucleoside are both time- and dose-dependent. Flow cytometry analyses validate that the nucleoside analog causes apoptosis by blocking cell cycle progression at G2/M. Fluorescent microscopy studies show rapid accumulation in the cytoplasm within 4 h. However, more significant accumulation is observed in the nucleus and mitochondria after 24 h. This localization is consistent with the ability of the metal-containing nucleoside to influence cell cycle progression at G2/M. Mitochondrial depletion is also observed after longer incubations (Δt ∼48 h), and this effect may produce additional cytotoxic effects. siRNA knockdown experiments demonstrate that the nucleoside transporter, hENT1, plays a key role in the cellular entry of Ir(III)-PPY nucleoside. Collectively, these data provide evidence for the development of a metal-containing nucleoside that functions as a combined therapeutic and diagnostic agent against cancer.

Untangling knots between autophagic targets and candidate drugs, in cancer therapy

Autophagy is an evolutionarily conserved lysosomal mechanism implicated in a wide variety of pathological processes, such as cancer. Autophagy can be regulated by a limited number of autophagy-related genes (Atgs) such as oncogenic Bcl-2/Bcl-XL , mTORC1, Akt and PI3KCI, and tumour suppressive proteins PI3KCIII, Beclin-1, Bif-1, p53, DAPKs, PTEN and UVRAG, which play their crucial roles in regulating autophagy-related cancer. As autophagy has a dual role in cancer cells, with tumour-promoting and tumour-suppressing properties, it has become an attractive target for a series of emerging small molecule drugs. In this review, we reveal new discoveries of related small molecules or chemical compounds that can regulate autophagic pathways and lead to pro-death or pro-survival autophagy, in different types of cancer. We discuss the knots between autophagic targets and candidate drugs, in the hope of shedding new light on exploiting new anti-tumour small molecule drugs for future cancer therapy.

Mitochondria-targeted cancer therapy using a light-up probe with aggregation-induced-emission characteristics

Subcellular organelle-specific reagents for simultaneous tumor targeting, imaging, and treatment are of enormous interest in cancer therapy. Herein, we present a mitochondria-targeting probe (AIE-mito-TPP) by conjugating a triphenylphosphine (TPP) with a fluorogen which can undergo aggregation-induced emission (AIE). Owing to the more negative mitochondrial membrane potential of cancer cells than normal cells, the AIE-mito-TPP probe can selectively accumulate in cancer-cell mitochondria and light up its fluorescence. More importantly, the probe exhibits selective cytotoxicity for studied cancer cells over normal cells. The high potency of AIE-mito-TPP correlates with its strong ability to aggregate in mitochondria, which can efficiently decrease the mitochondria membrane potential and increase the level of intracellular reactive oxygen species (ROS) in cancer cells. The mitochondrial light-up probe provides a unique strategy for potential image-guided therapy of cancer cells.

Tumor imaging and targeting potential of an Hsp70-derived 14-mer peptide

BACKGROUND

We have previously used a unique mouse monoclonal antibody cmHsp70.1 to demonstrate the selective presence of a membrane-bound form of Hsp70 (memHsp70) on a variety of leukemia cells and on single cell suspensions derived from solid tumors of different entities, but not on non-transformed cells or cells from corresponding 'healthy' tissue. This antibody can be used to image tumors in vivo and target them for antibody-dependent cellular cytotoxicity. Tumor-specific expression of memHsp70 therefore has the potential to be exploited for theranostic purposes. Given the advantages of peptides as imaging and targeting agents, this study assessed whether a 14-mer tumor penetrating peptide (TPP; TKDNNLLGRFELSG), the sequence of which is derived from the oligomerization domain of Hsp70 which is expressed on the cell surface of tumor cells, can also be used for targeting membrane Hsp70 positive (memHsp70+) tumor cells, in vitro.

METHODOLOGY/PRINCIPAL FINDINGS

The specificity of carboxy-fluorescein (CF-) labeled TPP (TPP) to Hsp70 was proven in an Hsp70 knockout mammary tumor cell system. TPP specifically binds to different memHsp70+ mouse and human tumor cell lines and is rapidly taken up via endosomes. Two to four-fold higher levels of CF-labeled TPP were detected in MCF7 (82% memHsp70+) and MDA-MB-231 (75% memHsp70+) cells compared to T47D cells (29% memHsp70+) that exhibit a lower Hsp70 membrane positivity. After 90 min incubation, TPP co-localized with mitochondrial membranes in memHsp70+ tumors. Although there was no evidence that any given vesicle population was specifically localized, fluorophore-labeled cmHsp70.1 antibody and TPP preferentially accumulated in the proximity of the adherent surface of cultured cells. These findings suggest a potential association between membrane Hsp70 expression and cytoskeletal elements that are involved in adherence, the establishment of intercellular synapses and/or membrane reorganization.

CONCLUSIONS/SIGNIFICANCE

This study demonstrates the specific binding and rapid internalization of TPP by tumor cells with a memHsp70+ phenotype. TPP might therefore have potential for targeting and imaging the large proportion of tumors (∼50%) that express memHsp70.

A selective mitochondrial-targeted chlorambucil with remarkable cytotoxicity in breast and pancreatic cancers

Nitrogen mustards, widely used as chemotherapeutics, have limited safety and efficacy. Mitochondria lack a functional nucleotide excision repair mechanism to repair DNA adducts and are sensitive to alkylating agents. Importantly, cancer cells have higher intrinsic mitochondrial membrane potential (Δψmt) than normal cells. Therefore, selectively targeting nitrogen mustards to cancer cell mitochondria based on Δψmt could overcome those limitations. Herein, we describe the design, synthesis, and evaluation of Mito-Chlor, a triphenylphosphonium derivative of the nitrogen mustard chlorambucil. We show that Mito-Chlor localizes to cancer cell mitochondria where it acts on mtDNA to arrest cell cycle and induce cell death, resulting in a 80-fold enhancement of cell kill in a panel of breast and pancreatic cancer cell lines that are insensitive to the parent drug. Significantly, Mito-Chlor delayed tumor progression in a mouse xenograft model of human pancreatic cancer. This is a first example of repurposing chlorambucil, a drug not used in breast and pancreatic cancer treatment, as a novel drug candidate for these diseases.

Artemether combined with shRNA interference of vascular cell adhesion molecule-1 significantly inhibited the malignant biological behavior of human glioma cells

Artemether is the derivative extracted from Chinese traditional herb and originally used for malaria. Artemether also has potential therapeutic effects against tumors. Vascular cell adhesion molecule-1 (VCAM-1) is an important cell surface adhesion molecule associated with malignancy of gliomas. In this work, we investigated the role and mechanism of artemether combined with shRNA interference of VCAM-1 (shRNA-VCAM-1) on the migration, invasion and apoptosis of glioma cells. U87 human glioma cells were treated with artemether at various concentrations and shRNA interfering technology was employed to silence the expression of VCAM-1. Cell viability, migration, invasiveness and apoptosis were assessed with MTT, wound healing, Transwell and Annexin V-FITC/PI staining. The expression of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and phosphorylated Akt (p-Akt) was checked by Western blot assay. Results showed that artemether and shRNA-VCAM-1 not only significantly inhibited the migration, invasiveness and expression of MMP-2/9 and p-Akt, but also promoted the apoptosis of U87 cells. Combined treatment of both displayed the maximum inhibitory effects on the malignant biological behavior of glioma cells. Our work revealed the potential therapeutic effects of artemether and antiVCAM-1 in the treatments of gliomas.