Nano-Engineered Mesenchymal Stem Cells Increase Therapeutic Efficacy of Anticancer Drug Through True Active Tumor Targeting.

Tumor-targeted drug delivery has the potential to improve therapeutic efficacy and mitigate non-specific toxicity of anticancer drugs. However, current drug delivery approaches rely on inefficient passive accumulation of the drug carrier in the tumor. We have developed a unique, truly active tumor-targeting strategy that relies on engineering mesenchymal stem cells (MSC) with drug-loaded nanoparticles. Our studies using the A549 orthotopic lung tumor model show that nano-engineered MSCs carrying the anticancer drug paclitaxel (PTX) home to tumors and create cellular drug depots that release the drug payload over several days. Despite significantly lower doses of PTX, nano-engineered MSCs resulted in significant inhibition of tumor growth and superior survival. Anticancer efficacy of nano-engineered MSCs was confirmed in immunocompetent C57BL/6 albino female mice bearing orthotopic Lewis Lung Carcinoma (LL/2-luc) tumors. Furthermore, at doses that resulted in equivalent therapeutic efficacy, nano-engineered MSCs had no effect on white blood cell count, whereas PTX solution and PTX nanoparticle treatments caused leukopenia. Biodistribution studies showed that nano-engineered MSCs resulted in greater than 9-fold higher AUClung of PTX (1.5 µg.day/g) than PTX solution and nanoparticles (0.2 and 0.1 µg.day/g tissue, respectively) in the target lung tumors. Furthermore, the lung-to-liver and the lung-to-spleen ratios of PTX were several folds higher for nano-engineered MSCs relative to those for PTX solution and nanoparticle groups, suggesting that nano-engineered MSCs demonstrate significantly less off-target deposition. In summary, our results demonstrate that nano-engineered MSCs can serve as an efficient carrier for tumor-specific drug delivery and significantly improved anti-cancer efficacy of conventional chemotherapeutic drugs. Mol Cancer Ther; 17(6); 1196-206. ©2018 AACR.

Incorporation of lipolysis in monolayer permeability studies of lipid-based oral drug delivery systems.

Lipid-based drug delivery systems, a well-tolerated class of formulations, have been evaluated extensively to enhance the bioavailability of poorly soluble drugs. However, it has been difficult to predict the in vivo performance of lipid dosage forms based on conventional in vitro techniques such as cell monolayer permeability studies because of the complexity of the gastrointestinal processing of lipid formulations. In the current study, we explored the feasibility of coupling Caco-2 and Madin-Darby canine kidney monolayer permeability studies with lipolysis, a promising in vitro technique to evaluate lipid systems. A self-emulsifying lipid delivery system was formulated using a blend of oil (castor oil), surfactant (Labrasol® or PL497), and co-surfactant (lecithin). Formulations demonstrating high drug solubility and rapid self-emulsification were selected to study the effect of lipolysis on in vitro cell permeability. Lipolysis of the formulations was carried out using pancreatin as the digestive enzyme. All the digested formulations compromised monolayer integrity as indicated by lowered trans-epithelial electrical resistance (TEER) and enhanced Lucifer yellow (LY) permeability. Further, the changes in TEER value and LY permeability were attributable to the digestion products of the formulation rather than the individual lipid excipients, drug, digestion enzyme, or the digestion buffer. The digested formulations were fractionated into pellet, oily phase, and aqueous phase, and the effect of each of these on cell viability was examined. Interestingly, the aqueous phase, which is considered important for in vivo drug absorption, was responsible for cytotoxicity. Because lipid digestion products lead to disruption of cell monolayer, it may not be appropriate to combine lipolysis with cell monolayer permeability studies. Additional in vivo studies are needed to determine any potential side effects of the lipolysis products on the intestinal permeability barrier, which could determine the suitability of lipid-based systems for oral drug delivery.

Fibrinolytic Enzyme Cotherapy Improves Tumor Perfusion and Therapeutic Efficacy of Anticancer Nanomedicine.

Elevated interstitial fluid pressure and solid stress within tumors contribute to poor intratumoral distribution of nanomedicine. In this study, we hypothesized that the presence of fibrin in tumor extracellular matrix contributes to hindered intratumoral distribution of nanocarriers and that this can be overcome through the use of a fibrinolytic enzyme such as tissue plasminogen activator (tPA). Analysis of fibrin expression in human tumor biopsies showed significant fibrin staining in nearly all tumor types evaluated. However, staining was heterogeneous across and within tumor types. We determined the effect of fibrin on the diffusion, intratumoral distribution, and therapeutic efficacy of nanocarriers. Diffusivity of nanocarriers in fibrin matrices was limited and could be improved significantly by coincubation with tPA. In vivo, coadministration of tPA improved the anticancer efficacy of nanoparticle-encapsulated paclitaxel in subcutaneous syngeneic mouse melanoma and orthotopic xenograft lung cancer models. Furthermore, treatment with tPA led to decompression of blood vessels and improved tumor perfusion. Cotreatment with tPA resulted in greater intratumoral penetration of a model nanocarrier (Doxil), leading to enhanced availability of the drug in the tumor core. Fibrinolytics such as tPA are already approved for other indications. Fibrinolytic cotherapy is therefore a rapidly translatable strategy for improving therapeutic effectiveness of anticancer nanomedicine. Cancer Res; 77(6); 1465-75. ©2017 AACR.

Glycoengineered mesenchymal stem cells as an enabling platform for two-step targeting of solid tumors.

Current tumor targeted drug and diagnostic delivery systems suffer from a lack of selectivity for tumor cells. Here, we propose a two-step tumor targeting strategy based on mesenchymal stem cells (MSCs), which actively traffic to tumors. We developed glycoengineering protocols to induce expression of non-natural azide groups on the surface of MSCs without affecting their viability or tumor homing properties. Glycoengineered MSCs demonstrated active tumor homing in subcutaneous and orthotopic lung and ovarian tumor models. Subsequent systemic administration of dibenzyl cyclooctyne (DBCO)-labeled fluorophores or nanoparticles to MSC pretreated mice resulted in enhanced tumor accumulation of these agents through bio-orthogonal copper-free click chemistry. Further, administration of glycoengineered MSCs along with paclitaxel-loaded DBCO-functionalized nanoparticles resulted in significant (p < 0.05) inhibition of tumor growth and improved survival (p < 0.0001) in an orthotopic metastatic ovarian tumor model. These results provide evidence for the potential of MSC-based two-step targeting strategy to improve the tumor specificity of diagnostic agents and drugs, and thus potentially improve the treatment outcomes for patients diagnosed with cancer.

Heterometallic titanium-gold complexes inhibit renal cancer cells in vitro and in vivo.

Following recent work on heterometallic titanocene-gold complexes as potential chemotherapeutics for renal cancer, we report here on the synthesis, characterization and stability studies of new titanocene complexes containing a methyl group and a carboxylate ligand (mba = S-C6H4-COO-) bound to gold(I)-phosphane fragments through a thiolate group ([(η-C5H5)2TiMe(µ-mba)Au(PR3)]. The compounds are more stable in physiological media than those previously reported and are highly cytotoxic against human cancer renal cell lines. We describe here preliminary mechanistic data involving studies on the interaction of selected compounds with plasmid (pBR322) DNA used as a model nucleic acid, and with selected protein kinases from a panel of 35 protein kinases having oncological interest. Preliminary mechanistic studies in Caki-1 renal cells indicate that the cytotoxic and anti-migration effects of the most active compound 5 ([(η-C5H5)2TiMe(µ-mba)Au(PPh3)] involve inhibition of thioredoxin reductase and loss of expression of protein kinases that drive cell migration (AKT, p90-RSK, and MAPKAPK3). The co-localization of both titanium and gold metals (1:1 ratio) in Caki-1 renal cells was demonstrated for 5 indicating the robustness of the heterometallic compound in vitro. Two compounds were selected for further in vivo studies on mice based on their selectivity in vitro against renal cancer cell lines when compared to non-tumorigenic human kidney cell lines (HEK-293T and RPTC) and the favourable preliminary toxicity profile in C57BL/6 mice. Evaluation of Caki-1 xenografts in NOD.CB17-Prkdc SCID/J mice showed an impressive tumor reduction (67%) after treatment for 28 days (3 mg/kg/every other day) with heterometallic compound 5 as compared with the previously described [(η-C5H5)2Ti{OC(O)-4-C6H4-P(Ph2)AuCI}2] 3 which was non-inhibitory. These findings indicate that structural modifications on the ligand scaffold affect the in vivo efficacy of this class of compounds.

Nano-engineered mesenchymal stem cells as targeted therapeutic carriers.

Poor availability in deep-seated solid tumors is a significant challenge that limits the effectiveness of currently used anticancer drugs. Approaches that can specifically enhance drug delivery to the tumor tissue can potentially improve therapeutic efficacy. In our current studies, we used nano-engineered mesenchymal stem cells (nano-engineered MSCs) as tumor-targeted therapeutic carriers. In addition to their exquisite tumor homing capabilities, MSCs overexpress efflux transporters such as P-glycoprotein and are highly drug resistant. The inherent tumor-tropic and drug-resistant properties make MSCs ideal carriers for toxic payload. Nano-engineered MSCs were prepared by treating human MSCs with drug-loaded polymeric nanoparticles. Incorporating nanoparticles in MSCs did not affect their viability, differentiation or migration potential. Nano-engineered MSCs induced dose-dependent cytotoxicity in A549 lung adenocarcinoma cells and MA148 ovarian cancer cells in vitro. An orthotopic A549 lung tumor model was used to monitor the in vivo distribution of nanoengineered MSCs. Intravenous injection of nanoparticles resulted in non-specific biodistribution, with significant accumulation in the liver and spleen while nano-engineered MSCs demonstrated selective accumulation and retention in lung tumors. These studies demonstrate the feasibility of developing nano-engineered MSCs loaded with high concentration of anticancer agents without affecting their tumor-targeting or drug resistance properties.

In vitro and in vivo evaluation of water-soluble iminophosphorane ruthenium(II) compounds. A potential chemotherapeutic agent for triple negative breast cancer.

A series of organometallic ruthenium(II) complexes containing iminophosphorane ligands have been synthesized and characterized. Cationic compounds with chloride as counterion are soluble in water (70-100 mg/mL). Most compounds (especially highly water-soluble 2) are more cytotoxic to a number of human cancer cell lines than cisplatin. Initial mechanistic studies indicate that the cell death type for these compounds is mainly through canonical or caspase-dependent apoptosis, nondependent on p53, and that the compounds do not interact with DNA or inhibit protease cathepsin B. In vivo experiments of 2 on MDA-MB-231 xenografts in NOD.CB17-Prkdc SCID/J mice showed an impressive tumor reduction (shrinkage) of 56% after 28 days of treatment (14 doses of 5 mg/kg every other day) with low systemic toxicity. Pharmacokinetic studies showed a quick absorption of 2 in plasma with preferential accumulation in the breast tumor tissues when compared to kidney and liver, which may explain its high efficacy in vivo.

Enhancing therapeutic efficacy through designed aggregation of nanoparticles.

Particle size is a key determinant of biological performance of sub-micron size delivery systems. Previous studies investigating the effect of particle size have primarily focused on well-dispersed nanoparticles. However, inorganic nanoparticles are prone to aggregation in biological environments. In our studies, we examined the consequence of aggregation on superparamagnetic iron oxide (SPIO) nanoparticle-induced magnetic hyperthermia. Here we show that the extent and mechanism of hyperthermia-induced cell kill is highly dependent on the aggregation state of SPIO nanoparticles. Well-dispersed nanoparticles induced apoptosis, similar to that observed with conventional hyperthermia. Sub-micron size aggregates, on the other hand, induced temperature-dependent autophagy through generation of oxidative stress. Micron size aggregates caused rapid membrane damage, resulting in acute cell kill. Overall, this work highlights the potential for developing highly effective anticancer therapeutics through designed aggregation of nano delivery systems.

Encapsulation in nanoparticles improves anti-cancer efficacy of carboplatin.

Poor cellular uptake contributes to high dose requirement and limited therapeutic efficacy of the platinum-based anticancer drug carboplatin. Delivery systems that can improve the cellular accumulation of carboplatin will, therefore, likely improve its therapeutic potential. The objective of this study was to evaluate nanoparticles composed of the biodegradable polymer, poly(D, L-lactide-co-glycolide), for carboplatin delivery to tumor cells. Carboplatin-loaded nanoparticles were formulated by double emulsion-solvent evaporation technique. Nanoparticles demonstrated sustained release of carboplatin over 7 days. Cellular uptake of carboplatin encapsulated in nanoparticles was several fold higher than that with free carboplatin in A549 (lung) and MA148 (ovarian) tumor cells. In vitro cytotoxicity studies showed that encapsulation of carboplatin in nanoparticles resulted in a remarkable reduction in the IC50 of carboplatin in several cell lines (up to 280-fold in some cells). Confocal microscopic analysis revealed the presence of carboplatin nanoparticles in several cellular compartments including lysosomes, cytoplasm, and the nucleus. These results demonstrate an enhanced cellular uptake of carboplatin through encapsulation in PLGA nanoparticles and suggest that improved therapeutic efficacy and reduced toxicity may be achieved with this approach.

Inhalable magnetic nanoparticles for targeted hyperthermia in lung cancer therapy.

Lung cancer (specifically, non-small cell lung cancer; NSCLC) is the leading cause of cancer-related deaths in the United States. Poor response rates and survival with current treatments clearly indicate the urgent need for developing an effective means to treat NSCLC. Magnetic hyperthermia is a non-invasive approach for tumor ablation, and is based on heat generation by magnetic materials, such as superparamagnetic iron oxide (SPIO) nanoparticles, when subjected to an alternating magnetic field. However, inadequate delivery of magnetic nanoparticles to tumor cells can result in sub-lethal temperature change and induce resistance while non-targeted delivery of these particles to the healthy tissues can result in toxicity. In our studies, we evaluated the effectiveness of tumor-targeted SPIO nanoparticles for magnetic hyperthermia of lung cancer. EGFR-targeted, inhalable SPIO nanoparticles were synthesized and characterized for targeting lung tumor cells as well as for magnetic hyperthermia-mediated antitumor efficacy in a mouse orthotopic model of NSCLC. Our results show that EGFR targeting enhances tumor retention of SPIO nanoparticles. Further, magnetic hyperthermia treatment using targeted SPIO nanoparticles resulted in significant inhibition of in vivo lung tumor growth. Overall, this work demonstrates the potential for developing an effective anticancer treatment modality for the treatment of NSCLC based on targeted magnetic hyperthermia.

Effective elimination of cancer stem cells by magnetic hyperthermia.

Cancer stem cells (CSCs) are a subpopulation of cancer cells that have stem cell-like properties and are thought to be responsible for tumor drug resistance and relapse. Therapies that can effectively eliminate CSCs will, therefore, likely inhibit tumor recurrence. The objective of our study was to determine the susceptibility of CSCs to magnetic hyperthermia, a treatment that utilizes superparamagnetic iron oxide nanoparticles placed in an alternating magnetic field to generate localized heat and achieve selective tumor cell kill. SPIO NPs having a magnetite core of 12 nm were used to induce magnetic hyperthermia in A549 and MDA-MB-231 tumor cells. Multiple assays for CSCs, including side population phenotype, aldehyde dehydrogenase expression, mammosphere formation, and in vivo xenotransplantation, indicated that magnetic hyperthermia reduced or, in some cases, eliminated the CSC subpopulation in treated cells. Interestingly, conventional hyperthermia, induced by subjecting cells to elevated temperature (46 °C) in a water bath, was not effective in eliminating CSCs. Our studies show that magnetic hyperthermia has pleiotropic effects, inducing acute necrosis in some cells while stimulating reactive oxygen species generation and slower cell kill in others. These results suggest the potential for lower rates of tumor recurrence after magnetic hyperthermia compared to conventional cancer therapies.

Image-guided drug delivery in lung cancer.

Lung cancer continues to be the number one cause of cancer-related deaths in the USA. Early identification of the disease, availability of more effective drugs, and improved delivery of such drugs specifically to cancer cells are needed to decrease lung cancer-associated morbidity and mortality. The concept of image-guided drug delivery (IGDD), which envisions the utilization of imaging techniques for quantitative assessments of tumor-targeted drug delivery and therapeutic response, has the potential to make a significant impact in lung cancer. While the anatomic and physiological features of the lung pose distinct problems for imaging drug delivery, several new techniques are emerging that have the potential to overcome these problems. X-ray is a routinely used technique for diagnosing lung cancer; however, positron emission tomography (PET) and magnetic resonance imaging (MRI) are complementary approaches. PET- and MRI-based techniques (such as functional MRI) offer the possibility of imaging the delivery of specific molecules to cancer tissues in the lung. This paper reviews fundamentals of imaging with an emphasis on MRI and to some extent PET, since it will be argued that these techniques are the most promising for development in IGDD for lung cancer. Finally, key literature contributions will be highlighted, which exemplify the current successes in this area.

The use of nanoparticle-mediated targeted gene silencing and drug delivery to overcome tumor drug resistance.

Overexpression of drug efflux transporters such as P-glycoprotein (P-gp) enables cancer cells to develop resistance to multiple anticancer drugs. Functional inhibitors of P-gp have shown promising efficacy in early clinical trials, but their long-term safety is yet to be established. A novel approach to overcome drug resistance is to use siRNA-mediated RNA interference to silence the expression of the efflux transporter. Because P-gp plays an important role in the physiological regulation of endogenous and xenobiotic compounds in the body, it is important to deliver P-gp targeted siRNA and anticancer drug specifically to tumor cells. Further, for optimal synergy, both the drug and siRNA may need to be temporally colocalized in the tumor cells. In the current study, we investigated the effectiveness of simultaneous and targeted delivery of anticancer drug, paclitaxel, along with P-gp targeted siRNA, using poly(D,L-lactide-co-glycolide) nanoparticles to overcome tumor drug resistance. Nanoparticles were surface functionalized with biotin for active tumor targeting. Dual agent nanoparticles encapsulating the combination of paclitaxel and P-gp targeted siRNA showed significantly higher cytotoxicity in vitro than nanoparticles loaded with paclitaxel alone. Enhanced therapeutic efficacy of dual agent nanoparticles could be correlated with effective silencing of the MDR1 gene that encodes for P-gp and with increased accumulation of paclitaxel in drug-resistant tumor cells. In vivo studies in a mouse model of drug-resistant tumor demonstrated significantly greater inhibition of tumor growth following treatment with biotin-functionalized nanoparticles encapsulating both paclitaxel and P-gp targeted siRNA at a paclitaxel dose that was ineffective in the absence of gene silencing. These results suggest that that the combination of P-gp gene silencing and cytotoxic drug delivery using targeted nanoparticles can overcome tumor drug resistance.

A review of select recent patents on novel nanocarriers.

Nanocarriers offer several advantages in drug delivery including increased retention time in the body, the ability to solubilize hydrophobic cargo, and the ability to target specific tissues. These attributes have led to a large volume of research being dedicated to the development of novel nanocarriers and their use in treating disease. Many advances have been made in the synthesis and formulation of nanocarriers. For instance, flash precipitation and the use of rotary evaporator provide new methods for nanocarrier synthesis. Biomolecules like heparin and sarcosine have been successfully utilized for the synthesis of unique copolymers for use in nanocarrier systems. Also, the efficacy of nanocarrier targeting has been increased by taking advantage of unique microenvironments present in specific pathologies, utilization of phage properties, and scaffold systems for multiple targeting moieties. Finally, nanocarriers have been shown to provide immunomodulatory effects. This article provides a focused review of several recent patents covering the synthesis, composition and the use of novel nanocarriers.

Nanoparticle-mediated simultaneous and targeted delivery of paclitaxel and tariquidar overcomes tumor drug resistance.

Drug resistance is a major obstacle to the success of cancer chemotherapy. Overexpression of the drug-efflux transporter P-glycoprotein (P-gp) is a key factor contributing to tumor drug resistance. Third generation P-gp inhibitors like tariquidar have shown promising efficacy in early clinical trials. However, for maximum efficacy, it is important to limit the exposure of normal cells and tissues to the efflux inhibitor and the anticancer drug, and temporally colocalize the drug-inhibitor combination in the tumor cells. In this study, we investigated simultaneous and targeted delivery of anticancer drug, paclitaxel, with P-gp modulator, tariquidar, using poly(d,l-lactide-co-glycolide) nanoparticles to overcome tumor drug resistance. Nanoparticles were surface functionalized with biotin for active tumor targeting. Dual agent nanoparticles encapsulating the combination of paclitaxel and tariquidar showed significantly higher cytotoxicity in vitro than nanoparticles loaded with paclitaxel alone. Enhanced therapeutic efficacy of dual agent nanoparticles could be correlated with increased accumulation of paclitaxel in drug-resistant tumor cells. In vivo studies in a mouse model of drug-resistant tumor demonstrated significantly greater inhibition of tumor growth following treatment with biotin-functionalized nanoparticles encapsulating both paclitaxel and tariquidar at a paclitaxel dose that was ineffective in the absence of tariquidar. Taken together, these results suggest that the use of targeted, dual agent nanoparticles delivering a combination of P-gp modulator and anticancer drug is a very promising approach to overcome tumor drug resistance.