[Show abstract][Hide abstract] ABSTRACT: Base excision repair (BER) is an essential pathway for pancreatic ductal adenocarcinoma (PDA) survival. Attempts to target this repair pathway have failed due to lack of tumor-selectivity and very limited efficacy. The NAD(P)H:Quinone Oxidoreductase 1 (NQO1) bioactivatable drug, ß-lapachone (ARQ761 in clinical form), can provide tumor-selective and enhanced synergy with BER inhibition. ß-Lapachone undergoes NQO1-dependent futile redox cycling, generating massive intracellular hydrogen peroxide levels and oxidative DNA lesions that stimulate poly(ADP-ribose) polymerase 1 (PARP1) hyperactivation. Rapid NAD+/ATP depletion and programmed necrosis results. To identify BER modulators essential for repair of ß-lapachone-induced DNA base damage, a focused synthetic lethal RNAi screen demonstrated that silencing the BER scaffolding protein, XRCC1, sensitized PDA cells. In contrast, depleting OGG1 N-glycosylase spared cells from ß-lap-induced lethality and blunted PARP1 hyperactivation. Combining ß-lapachone with XRCC1 knockdown or methoxyamine (MeOX), an apyrimidinic/apurinic (AP)-modifying agent, led to NQO1-dependent synergistic killing in PDA, NSCLC, breast and head and neck cancers. OGG1 knockdown, dicoumarol-treatment or NQO1- cancer cells were spared. MeOX + ß-lapachone exposure resulted in elevated DNA double-strand breaks, PARP1 hyperactivation and TUNEL+ programmed necrosis. Combination treatment caused dramatic antitumor activity, enhanced PARP1-hyperactivation in tumor tissue, and improved survival of mice bearing MiaPaca2-derived xenografts, with 33% apparent cures. Significance: Targeting base excision repair (BER) alone has limited therapeutic potential for pancreatic or other cancers due to a general lack of tumor-selectivity. Here, we present a treatment strategy that makes BER inhibition tumor-selective and NQO1-dependent for therapy of most solid neoplasms, particularly for pancreatic cancer.
Full-text · Article · Nov 2015 · Scientific Reports
[Show abstract][Hide abstract] ABSTRACT: Endosomes, lysosomes and related catabolic organelles are a dynamic continuum of vacuolar structures that impact a number of cell physiological processes such as protein/lipid metabolism, nutrient sensing and cell survival. Here we develop a library of ultra-pH-sensitive fluorescent nanoparticles with chemical properties that allow fine-scale, multiplexed, spatio-temporal perturbation and quantification of catabolic organelle maturation at single organelle resolution to support quantitative investigation of these processes in living cells. Deployment in cells allows quantification of the proton accumulation rate in endosomes; illumination of previously unrecognized regulatory mechanisms coupling pH transitions to endosomal coat protein exchange; discovery of distinct pH thresholds required for mTORC1 activation by free amino acids versus proteins; broad-scale characterization of the consequence of endosomal pH transitions on cellular metabolomic profiles; and functionalization of a context-specific metabolic vulnerability in lung cancer cells. Together, these biological applications indicate the robustness and adaptability of this nanotechnology-enabled â detection and perturbation ' strategy.
Full-text · Article · Oct 2015 · Nature Communications
[Show abstract][Hide abstract] ABSTRACT: Current cancer chemotherapy lacks specificity and is limited by undesirable toxic side-effects, as well as a high rate of recurrence. Nanotechnology has the potential to offer paradigm-shifting solutions to improve the outcome of cancer diagnosis and therapy. β-Lapachone (β-lap) is a novel anticancer agent whose mechanism of action is highly dependent on NAD(P)H:quinone oxidoreductase 1 (NQO1), a phase II detoxifying enzyme overexpressed in solid tumors from a variety of cancer types. However, the poor water solubility of β-lap limits its clinical potential. A series of drug formulations were developed for systemic administration in preclinical evaluations. Encapsulation of β-lap into polymeric micelles showed less side-effects and higher maximum tolerated dose (MTD), prolonged blood circulation time and preferential accumulation in tumors with greatly improved safety and antitumor efficacy. The prodrug strategy of β-lap further decreases the crystallization of β-lap by introducing esterase degradable side chains to the rigid fused ring structure. β-Lap prodrugs considerably increased the stability, drug-loading content and delivery efficiency of nanoparticles. The optimized formulation of β-lap-dC3 prodrug micelles showed excellent antitumor efficacy in treating orthotopic non-small cell lung tumors that overexpress NQO1, with target validation using pharmacodynamic endpoints.
Preview · Article · Sep 2015 · Journal of Drug Targeting
[Show abstract][Hide abstract] ABSTRACT: To celebrate the success of the Journal of Controlled Release and the research covered in the journal, here we highlight some of the most cited research articles in the history of the journal. Based on the literature search in Google Scholar in July 2013, we identified ~30 research articles that have received most number of citations. Authors of these articles were invited to provide a commentary on these articles. This compilation of commentaries gives a historical perspective and current status of research covered in these articles.
[Show abstract][Hide abstract] ABSTRACT: Objective: Folate receptor (FR) expression, while known to be elevated in many types of cancer and inflammatory cells, has not been well characterized in head and neck squamous cell carcinoma (HNSCC). We hypothesized that tumor infiltrating inflammatory cells expressing FR-β could allow fluorescent visualization of HNSCC tumors using folate conjugated dyes even when FR expression in cancer cells is low. Study Design: Retrospective review of clinical pathologic specimens and in vivo animal study. Methods: A tissue microarray (TMA) with tumor and tumor free tissue from 22 patients with HNSCC was stained with antibodies to FR-α and FR-β. We characterized FR-β(+) cells by examining CD45, CD68, CD206 and TGF-β expression. To investigate fluorescent imaging, mice with orthotopic tumor xenografts were imaged in vivo after intravenous injections of folate conjugated fluorescein isothiocyanate (folate-FITC) and were histologically evaluated ex vivo. Results: All tumor samples demonstrated significant FR-β staining and negligible FR-α staining. FR-β(+) cells found in tumors coexpressed CD68 and had increased expression of CD206 and TGF-β characteristic of tumor-associated macrophages. In the xenograft models, tumors showed strong in vivo fluorescence after folate-FITC injection in contrast to surrounding normal tissues. Histologic examination of the xenograft tissue similarly showed folate-FITC uptake in areas of inflammatory cellular infiltrate. Conclusion: While HNSCC tumor cells do not express FR, HNSCC tumors contain a significant population of FR-β expressing macrophages. Folate conjugated fluorescent dye is able to specifically target and label tumor xenografts to permit macroscopic fluorescence imaging due to FR-β expression on the infiltrating inflammatory cells.
No preview · Article · Aug 2014 · The Laryngoscope
[Show abstract][Hide abstract] ABSTRACT: β-Lap prodrug micelle strategy improves the formulation properties of β-lap therapeutics. The resulting micelles yield apparent high β-lap solubility (>7 mg mL(-1) ), physical stability, and ability to reconstitute after lyophilization. In the presence of esterase, β-lap prodrugs are efficiently converted into parent drug (i.e., β-lap), resulting in NQO1-dependent lethality of NSCLC cells.
No preview · Article · Aug 2014 · Advanced Healthcare Materials
[Show abstract][Hide abstract] ABSTRACT: Traditional micelle self-assembly is driven by the association of hydrophobic segments of amphiphilic molecules forming distinctive core-shell nanostructures in water. Here we report a surprising chaotropic-anion-induced micellization of cationic ammonium-containing block copolymers. The resulting micelle nanoparticle consists of a large number of ion pairs (≈60 000) in each hydrophobic core. Unlike chaotropic anions (e.g. ClO4 (-) ), kosmotropic anions (e.g. SO4 (2-) ) were not able to induce micelle formation. A positive cooperativity was observed during micellization, for which only a three-fold increase in ClO4 (-) concentration was necessary for micelle formation, similar to our previously reported ultra-pH-responsive behavior. This unique ion-pair-containing micelle provides a useful model system to study the complex interplay of noncovalent interactions (e.g. electrostatic, van der Waals, and hydrophobic forces) during micelle self-assembly.
No preview · Article · Jul 2014 · Angewandte Chemie International Edition in English
[Show abstract][Hide abstract] ABSTRACT: pH is an important physiological parameter that plays a critical role in cellular and tissue homeostasis. Conventional small molecular pH sensors (e.g. fluorescein, Lysosensor) are limited by broad pH response and restricted fluorescent emissions. Previously, we reported the development of ultra-pH sensitive (UPS) nanoprobes with sharp pH response using fluorophores with small Stokes shifts (<40 nm). In this study, we expand the UPS design to a library of nanoprobes with operator-predetermined pH transitions and wide fluorescent emissions (400-820 nm). A copolymer strategy was employed to fine tune the hydrophobicity of the ionizable hydrophobic block, which led to desired transition pH based on standard curves. Interestingly, matching the hydrophobicity of the monomers was critical to achieve a sharp pH transition. To overcome the fluorophore limitations, we introduced copolymers conjugated with fluorescence quenchers (FQs). In the micelle state, the FQs effectively suppressed the emission of fluorophores regardless of their Stokes shifts, and further increased the fluorescence activation ratios. As a proof of concept, we generated a library of 10 nanoprobes each encoded with a unique fluorophore. The nanoprobes cover the entire physiologic range of pH (4-7.4) with 0.3 pH increments. Each nanoprobe maintained a sharp pH transition (on/off < 0.25 pH) and high fluorescence activation ratio (>50-fold between on and off states). The UPS library provides a useful toolkit to study pH regulation in many pathophysiological indications (e.g. cancer, lysosome catabolism) as well as establishing tumor-activatable systems for cancer imaging and drug delivery.
Preview · Article · Jul 2014 · Journal of the American Chemical Society
[Show abstract][Hide abstract] ABSTRACT: Phosphatidylserine (PS), normally restricted to the inner leaflet of the plasma membrane, becomes exposed on the outer surface of viable endothelial cells in tumor vasculature, but not in normal blood vessels. In the present study, we report the use of PGN635, a novel human monoclonal antibody that specifically targets PS, for in vivo molecular MRI of tumor vasculature. The F(ab')2 fragments of PGN635 were conjugated to polyethylene glycol (PEG) coated iron oxide nanoparticles (IO). Targeting specificity of the PS-targeted Nanoprobe, IO-PGN635F(ab')2 was first confirmed by in vitro MRI and histological staining. In vivo longitudinal MRI was then performed before and after i.v. injection of IO-PGN635F(ab')2 into mice bearing 4T1 breast tumors. T2-weighted MR images at 9.4 T revealed inhomogeneous signal loss in tumor as early as 2 h post injection. Furthermore, ionizing radiation induced a significant increase in PS exposure on tumor vascular endothelial cells, resulting in significantly enhanced and sustained tumor contrast (p < 0.05). Spatially heterogeneous MRI contrast correlated well with histological staining of tumor vascular endothelium. Our studies suggest that PS exposed within the lumen of tumor vasculature is a highly specific and useful biomarker for targeted MRI contrast agents.
No preview · Article · May 2014 · Journal of Biomedical Nanotechnology
[Show abstract][Hide abstract] ABSTRACT: Poly (ADP-ribose) polymerases (PARPs) are a family of related enzymes that share the ability to catalyze the transfer of ADP-ribose to target proteins. PARPs play an important role in various cellular processes, including modulation of chromatin structure, transcription, replication, recombination, and DNA repair. The role of PARP proteins in DNA repair is of particular interest, in view of the finding that certain tumors defective in homologous recombination mechanisms, may rely on PARP-mediated DNA repair for survival, and are sensitive to its inhibition. PARP inhibitors may also increase tumor sensitivity to DNA-damaging agents. Clinical trials of PARP inhibitors are investigating the utility of these approaches in cancer. The hyperactivation of PARP has also been shown to result in a specific programmed cell death pathway involving NAD+/ATP depletion, mu-calpain activation, loss of mitochondrial membrane potential, and the release of apoptosis inducing factor. Hyperactivation of the PARP pathway may be exploited to selectively kill cancer cells. Other PARP forms, including tankyrase 1 (PARP 5a), which plays an important role in enhancing telomere elongation by telomerase, have been found to be potential targets in cancer therapy. The PARP pathway and its inhibition thus offers a number of opportunities for therapeutic intervention in both cancer and other disease states.
No preview · Article · Mar 2014 · Critical Reviews in Eukaryotic Gene Expression
[Show abstract][Hide abstract] ABSTRACT: Stimuli-responsive nanomaterials are increasingly important in a variety of applications such as biosensing, molecular imaging, drug delivery and tissue engineering. For cancer detection, a paramount challenge still exists in the search for methods that can illuminate tumours universally regardless of their genotypes and phenotypes. Here we capitalized on the acidic, angiogenic tumour microenvironment to achieve the detection of tumour tissues in a wide variety of mouse cancer models. This was accomplished using ultra pH-sensitive fluorescent nanoprobes that have tunable, exponential fluorescence activation on encountering subtle, physiologically relevant pH transitions. These nanoprobes were silent in the circulation, and then strongly activated (>300-fold) in response to the neovasculature or to the low extracellular pH in tumours. Thus, we have established non-toxic, fluorescent nanoreporters that can nonlinearly amplify tumour microenvironmental signals, permitting the identification of tumour tissue independently of histological type or driver mutation, and detection of acute treatment responses much more rapidly than conventional imaging approaches.
[Show abstract][Hide abstract] ABSTRACT: Amide proton transfer (APT) imaging is one of the chemical exchange saturation transfer (CEST) imaging methods which images the exchange between protons of free tissue water and the amide groups (-NH) of endogenous mobile proteins and peptides. Previous work suggested the ability of APT imaging for characterization of the tumoral grade in the brain tumor. In this study, we tested the feasibility of in-vivo APT imaging of lung tumor and investigated whether the method could differentiate the tumoral types on orthotopic tumor xenografts from two malignant lung cancer cell lines. The results revealed that APT imaging is feasible to quantify lung tumors in the moving lung. The measured APT effect was higher in the tumor which exhibited more active proliferation than the other. The present study demonstrates that APT imaging has the potential to provide a characterization test to differentiate types or grade of lung cancer noninvasively, which may eventually reduce the need invasive needle biopsy or resection for lung cancer.
[Show abstract][Hide abstract] ABSTRACT: We report an jet rollable nanoimprint lithography tool as a low cost method to produce micro- and nano-structures rapidly over large areas. We integrated a piezoelectric nozzle to deposit resist in-line in a low-waste, high-precision manner. We demonstrate the capabilities of this system by creating a variety of microstructures in SU8 resist with high pattern transfer fidelity.
[Show abstract][Hide abstract] ABSTRACT: Imaging all the people: Using ionizable diblock copolymers a series of nanoprobes encoded with different (19) F reporters for specific pH transitions is prepared for use in MRI. The pH response of the nanoprobes is extremely sharp (ΔpHON/OFF ≈0.25 pH), and results from the disassembly of polymer micelles. A collection of three nanoprobes provides the proof of concept and allows for a qualitative measurement of environmental pH values.
No preview · Article · Jul 2013 · Angewandte Chemie International Edition
[Show abstract][Hide abstract] ABSTRACT: Improving patient outcome by personalized therapy involves a thorough understanding of an agent's mechanism of action. β-Lapachone (clinical forms, Arq501/Arq761) has been developed to exploit dramatic cancer-specific elevations in the phase II detoxifying enzyme, NAD(P)H:quinone oxidoreductase (NQO1). NQO1 is dramatically elevated in solid cancers, including primary and metastatic (e.g., triple-negative (ER-, PR-, Her2/Neu-)) breast cancers. To define cellular factors that influence the efficacy of β-lapachone using knowledge of its mechanism of action, we confirmed that NQO1 was required for lethality and mediated a futile redox cycle where ~120 moles of superoxide were formed per mole of β-lapachone in 5 min. β-Lapachone induced reactive oxygen species (ROS), stimulated DNA single strand break-dependent PARP1 hyperactivation, caused dramatic loss of essential nucleotides (NAD+/ATP) and elicited programmed necrosis in breast cancer cells. While PARP1 hyperactivation and NQO1 expression were major determinants of β-lapachone-induced lethality, alterations in catalase expression, including treatment with exogenous enzyme, caused marked cytoprotection. Thus, catalase is an important resistance factor, and highlights H2O2 as an obligate ROS for cell death from this agent. Exogenous superoxide dismutase (SOD) enhanced catalase-induced cytoprotection. β-Lapachone-induced cell death included AIF translocation from mitochondria to nuclei, TUNEL+ staining, atypical PARP1 cleavage, and GAPDH S-nitrosylation, which were abrogated by catalase. We predict that the ratio of NQO1:catalase activities in breast cancer versus associated normal tissue are likely to be the major determinants affecting the therapeutic window of β-lapachone and other NQO1 bioactivatable drugs.
Full-text · Article · Jul 2013 · Molecular Cancer Therapeutics
[Show abstract][Hide abstract] ABSTRACT: In this communication, we report that ionizable, tertiary amine-based block copolymers can be used as pH-responsive contrast agents for magnetic resonance imaging (MRI) through the chemical exchange saturation transfer (CEST) mechanism. The CEST signal is essentially "off" when the polymers form micelles near physiological pH but is activated to the "on" state when the micelles dissociate in an acidic environment.
Full-text · Article · Jun 2013 · Chemical Communications