Shanta Dhar

A Prodrug of Two Approved Drugs, Cisplatin and Chlorambucil, for Chemo War Against Cancer

Cancer cells maintain normal mitochondrial glutathione as one of the defense mechanisms to inhibit mitochondrial membrane polarization and hence apoptosis. A combinational therapeutic modality Platin-Cbl, a prodrug of FDA-approved chemotherapeutic agents, cisplatin and chlorambucil (Cbl), was synthesized and characterized to explore the potential of this compound to initiate chemo war on cancer cells using the active drugs, cisplatin and Cbl, when delivered to the cellular power house mitochondrion using a targeted nanoparticle designed to get associated with this organelle. Platin-Cbl demonstrated significantly high cytotoxic activity across a number of tumor cell lines as well as in a cisplatin-resistant cancer cell line compared with cisplatin or its mixture with Cbl suggesting its unique potency in cisplatin-resistant tumors. A mitochondria-targeted nanoparticle formulation of Platin-Cbl allowed for its efficacious mitochondrial delivery. In vitro studies documented high potency of Platin-Cbl nanoparticle formulations. Cisplatin-resistant cells upon treatment with Platin-Cbl were still able to manage energy production to a certain extent via fatty acid pathway; the advantage of using T-Platin-Cbl-NP is that this nanoparticle treatment causes impairment of all metabolic pathways in cisplatin-resistant cells forcing the cells to undergo efficient apoptosis. This study highlights a combination of several beneficial effects for a cascade of events to overcome resistance associated with single drug therapy. Mol Cancer Ther; 16(4); 625–36. ©2017 AACR.

Targeting Hypoxia-Inducible Factor-1α/Pyruvate Dehydrogenase Kinase 1 Axis by Dichloroacetate Suppresses Bleomycin-induced Pulmonary Fibrosis

&NA; Hypoxia has long been implicated in the pathogenesis of fibrotic diseases. Aberrantly activated myofibroblasts are the primary pathological driver of fibrotic progression, yet how various microenvironmental influences, such as hypoxia, contribute to their sustained activation and differentiation is poorly understood. As a defining feature of hypoxia is its impact on cellular metabolism, we sought to investigate how hypoxia‐induced metabolic reprogramming affects myofibroblast differentiation and fibrotic progression, and to test the preclinical efficacy of targeting glycolytic metabolism for the treatment of pulmonary fibrosis. Bleomycin‐induced pulmonary fibrotic progression was evaluated in two independent, fibroblast‐specific, promoter‐driven, hypoxia‐inducible factor (Hif) 1A knockout mouse models and in glycolytic inhibitor, dichloroacetate‐treated mice. Genetic and pharmacological approaches were used to explicate the role of metabolic reprogramming in myofibroblast differentiation. Hypoxia significantly enhanced transforming growth factor‐&bgr;‐induced myofibroblast differentiation through HIF‐1&agr;, whereas overexpression of the critical HIF‐1&agr;‐mediated glycolytic switch, pyruvate dehydrogenase kinase 1 (PDK1) was sufficient to activate glycolysis and potentiate myofibroblast differentiation, even in the absence of HIF‐1&agr;. Inhibition of the HIF‐1&agr;/PDK1 axis by genomic deletion of Hif1A or pharmacological inhibition of PDK1 significantly attenuated bleomycin‐induced pulmonary fibrosis. Our findings suggest that HIF‐1&agr;/PDK1‐mediated glycolytic reprogramming is a critical metabolic alteration that acts to promote myofibroblast differentiation and fibrotic progression, and demonstrate that targeting glycolytic metabolism may prove to be a potential therapeutic strategy for the treatment of pulmonary fibrosis.

Radiobiology and the Renewed Potential for Nanoparticles

In a previous Oncology Scan, the Biology Editors discussed and nanomaterials offer considerable therapeutic potential, the synergy between radiation therapy and immunotherapy (1). In this edition, they examine the implications of nanotechnology. The clinical potential of nanotechnology has yet to be fully recognized (2). However, the past 2 decades have seen significant advances in nanotechnology-based tools in medicine. These developments have led to a myriad of conceptual design approaches that improve the therapeutic index of various drugs by overcoming the challenges of delivery (3). An example of such an interesting technology is the development of an injectable nanoparticle generator that consists of nanoporous silicon particles packaged with polymer conjugated doxorubicin (pDox) that self-assembles into nanometersized particles in solution (4). The Dox-loaded injectable nanoparticle generator preferentially accumulates at tumors, and then the polymer conjugated molecules assemble into nanoparticles and are released and internalized into tumor cells, yielding high intracellular concentrations of activated Dox. This nanoparticle-generator methodology delivered higher concentrations of Dox than was achieved by free drug and liposome-encapsulated doxorubicin (Doxil). This experimental concept was demonstrated in vivo by assessing growth inhibition of lung metastatic MDA-MB231 tumors. Gold nanoparticles have been the most widely adopted particles for radiation therapy studies because of their radiosensitizing properties and large dose enhancement factors due to the production of secondary electrons (5). This was elegantly reviewed by Schuemann et al in a recent article in this journal (6). In this report it was noted by the authors that preclinical animal studies have been largely confined to proof-of-principle experiments and modeling, but they propose that recent advances in nanotechnology will be realized as tangible therapeutic gains for clinical radiation therapy. This level of confidence and enthusiasm is supported by others within the nanoparticle field. King et al (7) highlight that nanotechnology

Centrifugation‐Free Magnetic Isolation of Functional Mitochondria Using Paramagnetic Iron Oxide Nanoparticles

Subcellular fractionation techniques are essential for cell biology and drug development studies. The emergence of organelle‐targeted nanoparticle (NP) platforms necessitates the isolation of target organelles to study drug delivery and activity. Mitochondria‐targeted NPs have attracted the attention of researchers around the globe, since mitochondrial dysfunctions can cause a wide range of diseases. Conventional mitochondria isolation methods involve high‐speed centrifugation. The problem with high‐speed centrifugation‐based isolation of NP‐loaded mitochondria is that NPs can pellet even if they are not bound to mitochondria. We report development of a mitochondria‐targeted paramagnetic iron oxide nanoparticle, Mito‐magneto, that enables isolation of mitochondria under the influence of a magnetic field. Isolation of mitochondria using Mito‐magneto eliminates artifacts typically associated with centrifugation‐based isolation of NP‐loaded mitochondria, thus producing intact, pure, and respiration‐active mitochondria.

Accessing Mitochondrial Targets Using NanoCargos

Mitochondria are membrane bound organelles that play essential roles for cell life, including energy production, apoptosis, redox balance, and regulation of calcium. Mitochondrial dysfunction is a hallmark for various diseases ranging from well-known diseases like cancer to rare genetic disorders like Barth’s syndrome. Accordingly, mitochondria have been identified as key targets for therapeutic intervention. Mitochondria targeting strategies using nanocargos are rapidly growing tools for delivery of therapeutic and/or diagnostic payloads to mitochondria. In this chapter, we will highlight specific mitochondrial targets for nanotechnology-based delivery vehicles, NanoCargos, and discuss intracellular uptake mechanisms for NanoCargos, as well as technological methods for investigating mechanism for NanoCargo internalization into mitochondria.