Combination Nanopreparations of a Novel Proapoptotic Drug - NCL-240, TRAIL and siRNA

Nano-TRAIL: a promising path to cancer therapy

Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand, also called apo-2 ligand (TRAIL/Apo-2L), is a cytokine that triggers apoptosis by binding to TRAIL-R1 (DR4) and TRAIL-R2 (DR5) death receptors. Apoptosis occurs through either the extrinsic or intrinsic pathway. The administration of recombinant human TRAIL (rhTRAIL) or TRAIL-receptor (TRAIL-R) agonists promotes apoptosis preferentially in cancerous cells over normal cells in vitro; this phenomenon has also been observed in clinical studies. The limited efficacy of rhTRAIL in clinical trials could be attributed to drug resistance, short half-life, targeted delivery issues, and off-target toxicities. Nanoparticles are excellent drug and gene delivery systems characterized by improved permeability and retention, increased stability and biocompatibility, and precision targeting. In this review, we discuss resistance mechanisms to TRAIL and methods to overcome TRAIL resistance by using nanoparticle-based formulations developed for the delivery of TRAIL peptides, TRAIL-R agonists, and TRAIL genes to cancer cells. We also discuss combinatorial approaches of chemotherapeutic drugs with TRAIL. These studies demonstrate TRAIL's potential as an anticancer agent.

Co-Delivery of siRNA and Chemotherapeutic Drug Using 2C5 Antibody-Targeted Dendrimer-Based Mixed Micelles for Multidrug Resistant Cancers

Multidrug resistance (MDR) observed in tumors significantly hinders the efficacy of chemotherapy. Downregulation of efflux proteins, such as P-glycoprotein (P-gp), using small interfering RNA (siRNA) can be an effective way to minimize the resistance in tumors. In this study, monoclonal antibody 2C5 (mAb 2C5)-PEG_7k-DOPE conjugates were post-inserted into the mixed dendrimer micelles containing generation 4 (G4) polyamidoamine (PAMAM)-PEG_2k-DOPE and PEG_5k-DOPE. The inherent amphiphilic nature of DOPE conjugates causes the copolymers to self-assemble to form a micelle, which can encapsulate hydrophobic chemotherapeutic drugs in its core. The siRNA electrostatically binds to the cationic charges on the G4 PAMAM dendrimer. The tumor-specific mAb 2C5 on the surface of these nano-preparations resulted in improved tumor targeting. This active targeting to tumors can cause increase in the drug and siRNA accumulation at the tumor site, and thereby minimizing the off-target effects. The micelles were shown to have higher cellular association and effectiveness in vitro. The immunomicelle preparation was also tested for cytotoxicity in breast (MDA-MB-231) and ovarian (SKOV-3TR) MDR cancer cell lines.

Simultaneous nanocarrier-mediated delivery of siRNAs and chemotherapeutic agents in cancer therapy and diagnosis: Recent advances

Recently, investigations have revealed that RNA interference (RNAi) has a remarkable potential to decrease cancer burden by downregulating genes. Among various RNAi molecules, small interfering RNA (siRNA) has been more attractive for this goal and is able to silence a target pathological path and promote the degradation of a certain mRNA, resulting in either gain or loss of function of proteins. Moreover, therapeutic siRNAs have exhibited low side effects compared to other therapeutic molecular candidates. Nevertheless, siRNA delivery has its own limitations including quick degradation in circulation, ineffective internalization and low passive uptake by cells, possible toxicity against off-target sites, and inducing unfavorable immune responses. Therefore, delivery tools must be able to specifically direct siRNAs to their target locations without inflicting detrimental effects on other sites. To conquer the mentioned problems, nanocarrier-mediated delivery of siRNAs, using inorganic nanoparticles (NPs), polymers, and lipids, has been developed as a biocompatible delivery approach. In this review, we have discussed recent advances in the siRNA delivery methods that employ nanoparticles, lipids, and polymers, as well as the inorganic-based co-delivery systems used to deliver siRNAs and anticancer agents to target cells.

TRAIL therapy and prospective developments for cancer treatment

Tumor Necrosis Factor (TNF) Related Apoptosis-Inducing Ligand (TRAIL), an immune cytokine of TNF-family, has received much attention in late 1990s as a potential cancer therapeutics due to its selective ability to induce apoptosis in cancer cells. TRAIL binds to cell surface death receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5) and facilitates formation of death-inducing signaling complex (DISC), eventually activating the p53-independent apoptotic cascade. This unique mechanism makes the TRAIL a potential anticancer therapeutic especially for p53-mutated tumors. However, recombinant human TRAIL protein (rhTRAIL) and TRAIL-R agonist monoclonal antibodies (mAb) failed to exert robust anticancer activities due to inherent and/or acquired resistance, poor pharmacokinetics and weak potencies for apoptosis induction. To get TRAIL back on track as a cancer therapeutic, multiple strategies including protein modification, combinatorial approach and TRAIL gene therapy are being extensively explored. These strategies aim to enhance the half-life and bioavailability of TRAIL and synergize with TRAIL action ultimately sensitizing the resistant and non-responsive cells. We summarize emerging strategies for enhanced TRAIL therapy in this review and cover a wide range of recent technologies that will provide impetus to rejuvenate the TRAIL therapeutics in the clinical realm.

In silico and in vitro identification of secoisolariciresinol as a re-sensitizer of P-glycoprotein-dependent doxorubicin-resistance NCI/ADR-RES cancer cells

P-glycoprotein (P-gp) is one of the highly expressed cancer cell efflux transporters that cause the failure of chemotherapy. To reverse P-gp induced multidrug resistance, we employed a flaxseed-derived lignan; secoisolariciresinol (SECO) that acts as an inhibitor of breast cancer resistance protein; another efflux transporter that shares some substrate/inhibitor specificity with P-gp. Molecular dynamics (MD) simulation identified SECO as a possible P-gp inhibitor. Comparing root mean square deviation (RMSD) of P-gp bound with SECO with that bound to its standard inhibitor verapamil showed that fluctuations in RMSD were lower in P-gp bound to SECO demonstrating higher stability of the complex of P-gp with SECO. In addition, the superimposition of P-gp structures after MD simulation showed that the nucleotide-binding domains of P-gp bound to SECO undertook a more central closer position compared with that bound to verapamil. Using rhodamine efflux assay on NCI/ADR-RES cancer cells, SECO was confirmed as a P-gp inhibitor, where cells treated with 25 or 50 µM of SECO showed significantly higher fluorescence intensity compared to control. Using MTT assay, SECO alone showed dose-dependent cytotoxicity, where 25 or 50 µM of SECO caused significantly less NCI/ADR-RES cellular viability compared to control. Furthermore, when 50 µM of SECO was added to doxorubicin (DOX), an anticancer drug, SECO significantly enhanced DOX-induced cytotoxicity compared to DOX alone. The combination index calculated by CompuSyn software indicated synergism between DOX and SECO. Our results suggest SECO as a novel P-gp inhibitor that can re-sensitize cancer cells during DOX chemotherapy.

Dual delivery nanoscale device for miR-345 and gemcitabine co-delivery to treat pancreatic cancer

A polymeric dual delivery nanoscale device (DDND) was designed for combined delivery of microRNA (miR-345) and gemcitabine (GEM) to treat pancreatic cancer (PC). This temperature and pH-responsive pentablock copolymer system was able to restore miR-345, making xenograft tumors more susceptible to GEM, the standard therapy for PC. Restoration using DDND treatment results in sonic hedgehog signaling down regulation, which decreases desmoplasia, thereby resulting in improved GEM perfusion to the tumor and better therapeutic outcomes. The release of miR-345 and GEM could be tuned by using the DDND in the form of micelles or in the form of thermoreversible gels, based on polymer concentration. The DDNDs enabled miR-345 stability and sustained co-release of miR-345 and GEM, thereby facilitating dose-sparing use of GEM. Further, enhanced in vitro cellular uptake due to amphiphilic character, and endosomal escape because of the cationic end blocks led to efficient transfection with DDNDs. The combined DDND treatment enabled efficient reduction in cell viability of Capan-1 and CD18/HPAF cells in vitro compared with either GEM or miR-345 treatment alone. Mice carrying xenograft tumors treated with DDNDs carrying both miR-345 and GEM combination therapy displayed reduced tumor growth and less metastasis in distant organs compared to individual drug treatments. Immunohistochemical analysis of the xenograft tissues revealed significant down regulation of desmoplastic reaction, SHH, Gli-1, MUC4, and Ki67 compared to control groups.

Iron(II)-Polypyridyl Complexes Inhibit the Growth of Glioblastoma Tumor and Enhance TRAIL-Induced Cell Apoptosis

A promising cancer-targeting agent for the induction of apoptosis in tumor necrosis factor (TNF) proteins, the TNF-related apoptosis-inducing ligand (TRAIL) ligand, has found limited applications in the treatment of cancer cells, owing to its resistance by cancer cell lines. Therefore, the rational design of anticancer agents that could sensitize cancer cells towards TRAIL is of great significance. Herein, we report that synthetic iron(II)-polypyridyl complexes are capable of inhibiting the proliferation of glioblastoma cancer cells and efficiently enhancing TRAIL-induced cell apoptosis. Mechanistic studies demonstrated that the synthesized complexes induced cancer-cell apoptosis through triggering the activation of p38 and p53 and inhibiting the activation of ERK. Moreover, uPA and MMP-2/MMP-9, among the most important metastatic regulatory proteins, were also found to be significantly alerted after the treatment. Furthermore, we also found that tumor growth in nude mice was significantly inhibited by iron complex Fe2 through the induction of apoptosis without clear systematic toxicity, as indicated by histological analysis. Taken together, this study provides evidence for the further development of metal-based anticancer agents and chemosensitizers of TRAIL for the treatment of human glioblastoma cancer cells.

Bioorthogonal strategies for site-directed decoration of biomaterials with therapeutic proteins

Emerging strategies targeting site-specific protein modifications allow for unprecedented selectivity, fast kinetics and mild reaction conditions with high yield. These advances open exciting novel possibilities for the effective bioorthogonal decoration of biomaterials with therapeutic proteins. Site-specificity is particularly important to the therapeutics' end and translated by targeting specific functional groups or introducing new functional groups into the therapeutic at predefined positions. Biomimetic strategies are designed for modification of therapeutics emulating enzymatic strategies found in Nature. These strategies are suitable for a diverse range of applications - not only for protein-polymer conjugation, particle decoration and surface immobilization, but also for the decoration of complex biomaterials and the synthesis of bioresponsive drug delivery systems. This article reviews latest chemical and enzymatic strategies for the biorthogonal decoration of biomaterials with therapeutic proteins and inter-positioned linker structures. Finally, the numerous reports at the interface of biomaterials, linkers, and therapeutic protein decoration are integrated into practical advice for design considerations intended to support the selection of productive ligation strategies.

In silico comparisons between natural inhibitors of ABCB1/P-glycoprotein to overcome doxorubicin-resistance in the NCI/ADR-RES cell line

To investigate compound-protein binding mode and molecular dynamic simulation of P-glycoprotein (P-gp), in silico studies were performed to compare 12 naturally occurring compounds using two softwares. The net results showed that piperine (PIP) had the best binding affinity. In vitro studies on doxorubicin (DOX)-resistant NCI/ADR-RES cells, known to express P-gp, showed that, dose-dependently, PIP significantly increased intracellular accumulation of rhodamine-123 and had cytotoxic effects accessed by MTT assay. In addition, PIP at 25 and 50μM significantly potentiated DOX-induced cytotoxicity on the same cell line. P-gp ATPase assay showed that both DOX and PIP had dose-dependent inhibition of orthovandate-sensitive ATPase activity, indicating they are both P-gp inhibitors, with IC₅₀ of 84±1 and 37±2μM, respectively. PIP did not show any activation of ATPase activity, while DOX did, indicating that P-gp does not accept PIP as a substrate. Using DOX at concentration 33.33μM together with PIP (100μM), DOX-mediated P-gp ATPase activity was decreased to levels 4-folds lower than DOX alone. In conclusion, both in silico and in vitro studies confirm that PIP is an inhibitor of P-gp mediated DOX efflux, suggesting PIP as a promising adjuvant to DOX cancer chemotherapy.

Targeting energy metabolism of cancer cells: Combined administration of NCL-240 and 2-DG

Cancer cells increase their metabolism to produce the energy and biomolecules necessary for growth and proliferation. Thus, energy metabolism pathways may serve as targets for anti-cancer therapy. NCL-240 is a second generation anti-cancer drug belonging to the PITenins class of PI3K-Akt inhibitors. Our analysis suggested that NCL-240 caused disruptions in mitochondrial oxidative phosphorylation and up-regulated glycolysis, as evidenced by the loss of NMR peaks for the amino acid products derived from the TCA cycle along with presence of only lactate peaks and the loss of glucose peaks. NCL-240 was combined with 2-deoxy-d-glucose (2-DG) in early proof-of-concept studies on multiple cell lines. 2-DG enhanced cell death response to NCL-240 administration, with cytotoxicity results similar to those under hypoglycemic conditions. In further studies, NCL-240 encapsulated in phosphatidylcholine/cholesterol liposomes was combined with freely dissolved 2-DG. Cell cycle analysis of sensitive and resistant strains of A2780 cells treated with combinations of NCL-240/2-DG pointed to a G0/G1 phase arrest for 80-90% of the total, indicating an inability to grow and divide. Cytotoxicity studies with in vitro cancer cell monolayer models confirmed the results of cell cycle analysis. Significant improvements in cytotoxicity with combination treatments over control and individual treatments were seen in multiple cell lines. NCI/ADR-RES cancer cell spheroids further demonstrated the effectiveness of a NCL-240/2-DG combination.

Combination antitumor therapy with targeted dual-nanomedicines

Combination therapy is one of the important treatment strategies for cancer at present. However, the outcome of current combination therapy based on the co-administration of conventional dosage forms is suboptimal, due to the short half-lives of chemodrugs, their deficient tumor selectivity and so forth. Nanotechnology-based targeted delivery systems show great promise in addressing the associated problems and providing superior therapeutic benefits. In this review, we focus on the combination of therapeutic strategies between different nanomedicines or drug-loaded nanocarriers, rather than the co-delivery of different drugs via a single nanocarrier. We introduce the general concept of various targeting strategies of nanomedicines, present the principles of combination antitumor therapy with dual-nanomedicines, analyze their advantages and limitations compared with co-delivery strategies, and overview the recent advances of combination therapy based on targeted nanomedicines. Finally, we reviewed the challenges and future perspectives regarding the selection of therapeutic agents, targeting efficiency and the gap between the preclinical and clinical outcome.

Targeting of Micelles and Liposomes Loaded with the Pro-Apoptotic Drug, NCL-240, into NCI/ADR-RES Cells in a 3D Spheroid Model

PURPOSE

To develop transferrin (Tf)-targeted delivery systems for the pro-apoptotic drug, NCL-240, and to evaluate the efficacy of this delivery system in ovarian cancer NCI/ADR-RES cells, grown in vitro in a 3D spheroid model.

METHODS

Tf-targeted PEG-PE-based micellar and ePC/CHOL-based liposomal delivery systems for NCL-240 were prepared. NCI/ADR-RES cells were used to generate spheroids by a non-adhesive liquid overlay technique. Spheroid growth and development were monitored by size (diameter) analysis and H&E staining. The targeted formulations were compared to untargeted ones in terms of their degree of spheroid association and penetration. A cell viability analysis with NCL-240-loaded micelles and liposomes was performed to assess the effectiveness of Tf-targeting.

RESULTS

Tf-targeted polymeric micelles and Tf-targeted liposomes loaded with NCL-240 were prepared. NCI/ADR-RES cells generated spheroids that demonstrated the presence of a distinct necrotic core along with proliferating cells in the spheroid periphery, partly mimicking in vivo tumors. The Tf-targeted micelles and liposomes had a deeper spheroid penetration as compared to the untargeted delivery systems. Cell viability studies using the spheroid model demonstrated that Tf-mediated targeting markedly improved the cytotoxicity profile of NCL-240.

CONCLUSION

Transferrin targeting enhanced delivery and effectiveness of micelles and liposomes loaded with NCL-240 against NCI/ADR-RES cancer cells in a 3D spheroid model.