Sterically stabilized anti-idiotype immunoliposomes improve the therapeutic efficacy of doxorubicin in a murine B-cell lymphoma model

A robust post-insertion method for the preparation of targeted siRNA LNPs

Targeted delivery of nucleic acids is gaining momentum due to improved efficacy, selectivity, increased circulation time and enhanced tissue retention in target cells. Using nucleic acid-based therapies previously undruggable targets have proven now to be amenable for treatment. Currently, several methods for preparing targeted or labelled delivery vehicles for nucleic acids are based on liposomal formulations. Lipid nanoparticles (LNPs) are structurally different from liposomes and these methods should therefore be evaluated before being translated to siRNA LNPs preparation protocols. Here, we describe a robust and facile method for the preparation of targeted or fluorescently labelled siRNA LNPs. Using a copper free strain-promoted azide-alkyne cycloaddition (SPAAC) we demonstrate that post-insertion of ligand-lipid conjugates into preformed LNPs is superior to direct-surface modification because it preserves the physicochemical parameters of the LNPs. We found that the time point of solvent removal by dialysis is critical and affects the hydrodynamic diameter of the LNPs; post-insertion after dialysis shows the smallest increase in hydrodynamic diameter and polydispersity index (PDI). The post-insertion of ligand-lipid conjugates also proceeded with rapid kinetics and high efficacy over a wide temperature range. Using this optimised protocol, we generated siRNA LNPs containing both targeting and fluorescent tracking ligands allowing us to monitor siRNA LNP uptake kinetics in dependence of the targeting ligand. In aggregate, we describe a robust approach for the generation of targeted and labelled siRNA LNPs that allows their controlled and facile decoration with ligand combinations.

Bi-Functional Radiotheranostics of 188Re-Liposome-Fcy-hEGF for Radio- and Chemo-Therapy of EGFR-Overexpressing Cancer Cells

Epidermal growth factor receptor (EGFR) specific therapeutics is of great importance in cancer treatment. Fcy-hEGF fusion protein, composed of yeast cytosine deaminase (Fcy) and human EGF (hEGF), is capable of binding to EGFR and enzymatically convert 5-fluorocytosine (5-FC) to 1000-fold toxic 5-fluorocuracil (5-FU), thereby inhibiting the growth of EGFR-expressing tumor cells. To develop EGFR-specific therapy, ¹⁸⁸Re-liposome-Fcy-hEGF was constructed by insertion of Fcy-hEGF fusion protein onto the surface of liposomes encapsulating of ¹⁸⁸Re. Western blotting, MALDI-TOF, column size exclusion and flow cytometry were used to confirm the conjugation and bio-activity of ¹⁸⁸Re-liposome-Fcy-hEGF. Cell lines with EGFR expression were subjected to treat with ¹⁸⁸Re-liposome-Fcy-hEGF/5-FC in the presence of 5-FC. The ¹⁸⁸Re-liposome-Fcy-hEGF/5-FC revealed a better cytotoxic effect for cancer cells than the treatment of liposome-Fcy-hEGF/5-FC or ¹⁸⁸Re-liposome-Fcy-hEGF alone. The therapeutics has radio- and chemo-toxicity simultaneously and specifically target to EGFR-expression tumor cells, thereby achieving synergistic anticancer activity.

Therapeutic Efficacy Evaluation of Pegylated Liposome Encapsulated With Vinorelbine Plus 111In Repeated Treatments in Human Colorectal Carcinoma With Multimodalities of Molecular Imaging

BACKGROUND/AIM

In precision therapy, liposomal encapsulated chemotherapeutic drugs have been developed to treat cancers by achieving higher drug accumulation in the tumor compared to normal tissues/organs.

MATERIALS AND METHODS

We developed a novel chemoradiotherapeutic approach via nanoliposomes conjugated with vinorelbine (VNB) and ¹¹¹In (¹¹¹In-VNB-liposome) and examined their pharmacokinetics, biodistribution, maximum tolerance dose, and toxicity in a NOD/SCID mouse model.

RESULTS

Pharmacokinetic results showed that the area under the curve (AUC) of PEGylated liposomes was about 17-fold higher than that of the free radioisotope. Tumor growth inhibition by ¹¹¹In-VNB-liposome was significantly higher than that of the control (p<0.05).

CONCLUSION

The tumors in NOD/SCID mice bearing HT-29/tk-luc xenografts were significantly suppressed by ¹¹¹In-VNB-liposomes. The study proposed repeated treatments with a novel liposome-mediated radiochemotherapy and validation of therapeutic efficacy via imaging.

Aspartate-modified doxorubicin on its N-terminal increases drug accumulation in LAT1-overexpressing tumors

L-type amino acid transporter 1 (LAT1), overexpressed on the membrane of various tumor cells, is a potential target for tumor-targeting therapy. This study aimed to develop a LAT1-mediated chemotherapeutic agent. We screened doxorubicin modified by seven different large neutral amino acids. The aspartate-modified doxorubicin (Asp-DOX) showed the highest affinity (Km = 41.423 μmol/L) to LAT1. Aspartate was attached to the N-terminal of DOX by the amide bond with a free carboxyl and a free amino group on the α-carbon atom of the Asp residue. The product Asp-DOX was characterized by HPLC/MS. In vitro, Asp-DOX exerted stronger inhibition on the cancer cells overexpressing LAT1 and the uptake of Asp-DOX was approximately 3.5-fold higher than that of DOX in HepG2 cells. Pharmacokinetic data also showed that Asp-DOX was expressed over a longer circulation time (t1/2 = 49.14 min) in the blood compared to DOX alone (t1/2 = 15.12 min). In HepG2 and HCT116 tumor-bearing mice, Asp-DOX achieved 3.1-fold and 6.4-fold accumulation of drugs in tumor tissue, respectively, than those of the unmodified DOX. More importantly, treatment of tumor-bearing mice with Asp-DOX showed a significantly stronger inhibition of tumor growth than mice treated with free DOX in HepG2 tumor models. Furthermore, after Asp modification, Asp-DOX avoided MDR mediated by P-glycoprotein. These results suggested that the Asp-DOX modified drug may provide a new treatment strategy for tumors that overexpress LAT1 and MDR1.

External beam radiotherapy synergizes ¹⁸⁸Re-liposome against human esophageal cancer xenograft and modulates ¹⁸⁸Re-liposome pharmacokinetics

External beam radiotherapy (EBRT) treats gross tumors and local microscopic diseases. Radionuclide therapy by radioisotopes can eradicate tumors systemically. Rhenium 188 ((188)Re)-liposome, a nanoparticle undergoing clinical trials, emits gamma rays for imaging validation and beta rays for therapy, with biodistribution profiles preferential to tumors. We designed a combinatory treatment and examined its effects on human esophageal cancer xenografts, a malignancy with potential treatment resistance and poor prognosis. Human esophageal cancer cell lines BE-3 (adenocarcinoma) and CE81T/VGH (squamous cell carcinoma) were implanted and compared. The radiochemical purity of (188)Re-liposome exceeded 95%. Molecular imaging by NanoSPECT/CT showed that BE-3, but not CE81T/VGH, xenografts could uptake the (188)Re-liposome. The combination of EBRT and (188)Re-liposome inhibited tumor regrowth greater than each treatment alone, as the tumor growth inhibition rate was 30% with EBRT, 25% with (188)Re-liposome, and 53% with the combination treatment at 21 days postinjection. Combinatory treatment had no additive adverse effects and significant biological toxicities on white blood cell counts, body weight, or liver and renal functions. EBRT significantly enhanced the excretion of (188)Re-liposome into feces and urine. In conclusion, the combination of EBRT with (188)Re-liposome might be a potential treatment modality for esophageal cancer.

The influence of blood on targeted microbubbles

The ability to successfully target the delivery of drugs and other therapeutic molecules has been a key goal of biomedical research for many decades. Despite highly promising in vitro results, however, successful translation of targeted drug delivery into clinical use has been extremely limited. This study investigates the significance of the characteristics of whole blood, which are rarely accounted for in vitro assays, as a possible explanation for the poor correlation between in vitro and in vivo experiments. It is shown using two separate model systems employing either biochemical or magnetic targeting that blood causes a substantial reduction in targeting efficiency relative to saline under the same flow conditions. This finding has important implications for the design of targeted drug delivery systems and the assays used in their development.

Imaging, autoradiography, and biodistribution of (188)Re-labeled PEGylated nanoliposome in orthotopic glioma bearing rat model

The (188)Re-labeled pegylated nanoliposome (abbreviated as (188)Re-Liposome) was prepared and evaluated for its potential as a theragnostic agent for glioma. (188)Re-BMEDA complex was loaded into the pegylated liposome core with pH 5.5 ammonium sulfate gradient to produce (188)Re-Liposome. Orthotopic Fischer344/F98 glioma tumor-bearing rats were prepared and intravenously injected with (188)Re-Liposome. Biodistribution, pharmacokinetic study, autoradiography (ARG), histopathology, and nano-SPECT/CT imaging were conducted for the animal model. The result showed that (188)Re-Liposome accumulated in the brain tumor of the animal model from 0.28%±0.09% injected dose (ID)/g (n=3) at 1 hour to a maximum of 1.95%±0.35% ID/g (n=3) at 24 hours postinjection. The tumor-to-normal brain uptake ratio (T/N ratio) increased from 3.5 at 1 hour to 32.5 at 24 hours. Both ARG and histopathological images clearly showed corresponding tumor regions with high T/N ratios. Nano-SPECT/CT detected a very clear tumor image from 4 hours till 48 hours. This study reveals the potential of (188)Re-Liposome as a theragnostic agent for brain glioma.

Clinical development of liposome-based drugs: formulation, characterization, and therapeutic efficacy

Research on liposome formulations has progressed from that on conventional vesicles to new generation liposomes, such as cationic liposomes, temperature sensitive liposomes, and virosomes, by modulating the formulation techniques and lipid composition. Many research papers focus on the correlation of blood circulation time and drug accumulation in target tissues with physicochemical properties of liposomal formulations, including particle size, membrane lamellarity, surface charge, permeability, encapsulation volume, shelf time, and release rate. This review is mainly to compare the therapeutic effect of current clinically approved liposome-based drugs with free drugs, and to also determine the clinical effect via liposomal variations in lipid composition. Furthermore, the major preclinical and clinical data related to the principal liposomal formulations are also summarized.

Biodistribution and pharmacokinetics of 188Re-liposomes and their comparative therapeutic efficacy with 5-fluorouracil in C26 colonic peritoneal carcinomatosis mice

BACKGROUND

Nanoliposomes are designed as carriers capable of packaging drugs through passive targeting tumor sites by enhanced permeability and retention (EPR) effects. In the present study the biodistribution, pharmacokinetics, micro single-photon emission computed tomography (micro-SPECT/CT) image, dosimetry, and therapeutic efficacy of (188)Re-labeled nanoliposomes ((188)Re-liposomes) in a C26 colonic peritoneal carcinomatosis mouse model were evaluated.

METHODS

Colon carcinoma peritoneal metastatic BALB/c mice were intravenously administered (188)Re-liposomes. Biodistribution and micro-SPECT/CT imaging were performed to determine the drug profile and targeting efficiency of (188)Re-liposomes. Pharmacokinetics study was described by a noncompartmental model. The OLINDA|EXM computer program was used for the dosimetry evaluation. For therapeutic efficacy, the survival, tumor, and ascites inhibition of mice after treatment with (188)Re-liposomes and 5-fluorouracil (5-FU), respectively, were evaluated and compared.

RESULTS

In biodistribution, the highest uptake of (188)Re-liposomes in tumor tissues (7.91% ± 2.02% of the injected dose per gram of tissue [%ID/g]) and a high tumor to muscle ratio (25.8 ± 6.1) were observed at 24 hours after intravenous administration. The pharmacokinetics of (188)Re-liposomes showed high circulation time and high bioavailability (mean residence time [MRT] = 19.2 hours, area under the curve [AUC] = 820.4%ID/g*h). Micro-SPECT/CT imaging of (188)Re-liposomes showed a high uptake and targeting in ascites, liver, spleen, and tumor. The results were correlated with images from autoradiography and biodistribution data. Dosimetry study revealed that the (188)Re-liposomes did not cause high absorbed doses in normal tissue but did in small tumors. Radiotherapeutics with (188)Re-liposomes provided better survival time (increased by 34.6% of life span; P < 0.05), tumor and ascites inhibition (decreased by 63.4% and 83.3% at 7 days after treatment; P < 0.05) in mice compared with chemotherapeutics of 5-fluorouracil (5-FU).

CONCLUSION

The use of (188)Re-liposomes for passively targeted tumor therapy had greater therapeutic effect than the currently clinically applied chemotherapeutics drug 5-FU in a colonic peritoneal carcinomatosis mouse model. This result suggests that (188)Re-liposomes have potential benefit and are safe in treating peritoneal carcinomatasis of colon cancer.

Therapeutic efficacy evaluation of 111In-labeled PEGylated liposomal vinorelbine in murine colon carcinoma with multimodalities of molecular imaging

In our previous studies using combined radioisotopes with chemotherapeutic liposomal drugs (i.e., (111)In-labeled polyethylene glycol (PEG)ylated liposomal vinorelbine) we have reported possible therapeutic efficiency in tumor growth suppression. Nevertheless, the challenge remains as to whether this chemotherapy has a therapeutic effect as good as that of combination therapy. The goal of this study was to investigate the real therapeutic effectiveness of 6 mol% PEG (111)In-vinorelbine liposomes via the elevation of the radiation dosage and reduction in the concentration of chemotherapeutic agents.

METHODS

Murine colon carcinoma cells transfected with dual-reporter genes (CT-26/tk-luc) were xenografted into BALB/c mice. The biodistribution was estimated to determine the drug profile and targeting efficiency of (111)In-vinorelbine liposomes. Bioluminescence imaging and (18)F-FDG small-animal PET were applied to monitor the therapeutic response after drug administration. The survival in vivo was estimated and linked with the toxicologic and histopathologic analyses to determine the preclinical safety and feasibility of the nanomedicine.

RESULTS

Effective long-term circulation of radioactivity in the plasma was achieved by 6 mol% PEG (111)In-vinorelbine liposomes, and this dose showed significantly lower uptake in the reticuloendothelial system than that of 0.9 mol% PEG (111)In-vinorelbine liposomes. Selective tumor uptake was represented by cumulative deposition, and the maximum accumulation was at 48 h after injection. The combination therapy exhibited an additive effect for tumor growth suppression as tracked by caliper measurement, bioluminescence imaging, and small-animal PET. Furthermore, an improved survival rate and reduced tissue toxicity were closely correlated with the toxicologic and histopathologic results.

CONCLUSION

The results demonstrated that the use of 6 mol% PEG (111)In-vinorelbine liposomes for passively targeted tumor therapy displayed an additive effect with combined therapy, not only by prolonging the circulation rate because of a reduction in the phagocytic effect of the reticuloendothelial system but also by enhancing tumor uptake. Thus, this preclinical study suggests that 6 mol% PEG (111)In-vinorelbine liposomes have the potential to increase the therapeutic index and reduce the toxicity of the passively nanotargeted chemoradiotherapies.

Pharmacokinetics, micro-SPECT/CT imaging and therapeutic efficacy of (188)Re-DXR-liposome in C26 colon carcinoma ascites mice model

The pharmacokinetics and internal radionuclide therapy of intraperitoneally administrated (188)Re-N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA)-labeled pegylated liposomal doxorubicin ((188)Re-DXR-liposome) were investigated in the C26 murine colon carcinoma ascites mouse model. After intraperitoneal administration of the nanotargeted bimodality (188)Re-DXR-liposome, the ascites and tumor accumulation of the radioactivity were observed, the levels of radioactivity within the ascites were maintained at relatively higher levels before 48 h and the levels of radioactivity in the tumor were maintained at steady levels after 4 h. The AUC((o-->infinity)) of (188)Re-DXR-liposome in blood, ascites and tumor was 9.3-, 4.2- and 4.7-fold larger than that of (188)Re-BMEDA, respectively. The maximum tolerated dose of intraperitoneally administrated (188)Re-DXR-liposome was determined in normal BALB/c mice. The survival, tumor and ascites inhibition of mice after (188)Re-DXR-liposome (22.2 MBq of (188)Re, 5 mg/kg of DXR) treatment were evaluated. Consequently, radiochemotherapeutics of (188)Re-DXR-liposome attained better survival time, tumor and ascites inhibition (decreased by 49% and 91% at 4 days after treatment; P<.05) in mice than radiotherapeutics of (188)Re-liposome or chemotherapeutics of Lipo-Dox did. Therefore, intraperitoneal administration of novel (188)Re-DXR-liposome could provide a benefit and promising strategy for delivery of passive nanotargeted bimodality radiochemotherapeutics in oncology applications.

Lipid-based nanoparticles as pharmaceutical drug carriers: from concepts to clinic

In recent years, various nanotechnology platforms in the area of medical biology, including both diagnostics and therapy, have gained remarkable attention. Moreover, research and development of engineered multifunctional nanoparticles as pharmaceutical drug carriers have spurred exponential growth in applications to medicine in the last decade. Design principles of these nanoparticles, including nanoemulsions, dendrimers, nano-gold, liposomes, drug-carrier conjugates, antibody-drug complexes, and magnetic nanoparticles, are primarily based on unique assemblies of synthetic, natural, or biological components, including but not limited to synthetic polymers, metal ions, oils, and lipids as their building blocks. However, the potential success of these particles in the clinic relies on consideration of important parameters such as nanoparticle fabrication strategies, their physical properties, drug loading efficiencies, drug release potential, and, most importantly, minimum toxicity of the carrier itself. Among these, lipid-based nanoparticles bear the advantage of being the least toxic for in vivo applications, and significant progress has been made in the area of DNA/RNA and drug delivery using lipid-based nanoassemblies. In this review, we will primarily focus on the recent advances and updates on lipid-based nanoparticles for their projected applications in drug delivery. We begin with a review of current activities in the field of liposomes (the so-called honorary nanoparticles), and challenging issues of targeting and triggering will be discussed in detail. We will further describe nanoparticles derived from a novel class of amphipathic lipids called bolaamphiphiles with unique lipid assembly features that have been recently examined as drug/DNA delivery vehicles. Finally, an overview of an emerging novel class of particles (based on lipid components other than phospholipids), solid lipid nanoparticles and nanostructured lipid carriers will be presented. We conclude with a few examples of clinically successful formulations of currently available lipid-based nanoparticles.

Biodistribution, pharmacokinetics and imaging of 188Re-BMEDA-labeled pegylated liposomes after intraperitoneal injection in a C26 colon carcinoma ascites mouse model

Nanoliposomes are important carriers capable of packaging drugs for various delivery applications through passive targeting tumor sites by enhanced permeability and retention effect. Radiolabeled liposomes have potential applications in radiotherapy and diagnostic imaging. The purpose of this study was to investigate the biodistribution, pharmacokinetics and imaging of nanotargeted (188)Re-N,N-bis (2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA)-labeled pegylated liposomes (RBLPL) and unencapsulated (188)Re-BMEDA after intraperitoneal (ip) injection in a C26 colon carcinoma ascites mouse model. The nanopegylated liposomes were labeled with (188)Re-BMEDA. The labeling efficiency of RBLPL was 82.3+/-4.5%. In vitro stability of RBLPL in normal saline at room temperature and in rat plasma at 37 degrees C for 72 h was 92.01+/-1.31% and 82.4+/-1.64%, respectively. The biodistribution studies indicated that the radioactivity in ascites was 69.96+/-14.08 percentage injected dose per gram (% ID/g) at 1h to 5.99+/-1.97% ID/g at 48 h after ip administration of RBLPL. The levels of radioactivity in tumor were progressive accumulation to a maximum of 6.57+/-1.7% ID/g at 24 h. The radioactivity of (188)Re-BMEDA in ascites reached the maximum level of 54.89+/-5.91% ID/g at 1 h and declined rapidly with time. Pharmacokinetic studies revealed that the terminal half-life, total body clearance and area under the curve of RBLPL were 5.3-, 9.5- and 9.4-fold higher than that of (188)Re-BMEDA in blood, respectively. These results suggested that the long circulation, bioavailability and localization of RBLPL in tumor and ascites sites, which also demonstrate that the ip administration of RBLPL is a potential multifunctional nanoradiotherapeutics and imaging agents on a C26 colon carcinoma ascites mouse model.

Tumor-targeted hyaluronan nanoliposomes increase the antitumor activity of liposomal Doxorubicin in syngeneic and human xenograft mouse tumor models

Naturally occurring high-Mr hyaluronan, bound to the surface of nanoliposomes (denoted targeted hyaluronan liposomes, or tHA-LIP), is a candidate for active targeting to tumors, many of which overexpress the hyaluronan receptors CD44 and RHAMM. The surface-bound hyaluronan also provides a hydrophilic coat that, similar to polyethylene glycol, may promote long-term circulation. We recently reported the successful targeting of mitomycin C, mediated by tHA-LIP, in tumor-bearing syngeneic mice. Hypothesizing that this targeting is carrier-specific, rather than drug-specific, we report here studies with doxorubicin (DXR)-loaded tHA-LIP, in syngeneic and human xenograft models. Saline, free DXR, DXR-loaded nontargeted liposomes (nt-LIP), and Doxil served as controls. The tHA-LIP were long-circulating, more than all controls, in healthy and tumor-bearing (C57BL/6/B16F10.9; BALB/c/C-26) mice. Mediated by tHA-LIP, DXR accumulation in tumor-bearing lungs was 30-, 6.7-, and 3.5-fold higher than free DXR, nt-LIP, and Doxil, respectively. Key indicators of therapeutic responses--tumor progression, metastatic burden, and survival--were superior (P < .001) in animals receiving DXR-loaded tHA-LIP compared with controls, in tumor-bearing syngeneic mice (BDF1/P388/ADR ascites, C57BL/6/B16F10.9 lung metastasis, and BALB/c/C-26 solid tumors), and in nude mice bearing PANC-1 solid tumors. In conclusion, tHA-LIP, performing as tumor-targeted carriers, have the potential to join the arsenal of carrier-formulated anticancer drugs.

Les systèmes colloïdaux de délivrance de médicaments ont-ils aidé à répondre aux espérances thérapeutiques des découvertes de biotechnologie ?

New and fascinating advances in biotechnology have open new perspectives since the use of monoclonal antibodies for therapeutic application, particularly cancer, has been approved. Over the last two decades, numerous research teams have demonstrated that the progression of cancer is often associated with an over-expression of one or several proteins, called tumor antigens. In order to target tumors specifically, researchers have tried to couple monoclonal antibodies with colloid vectors such as liposomes, nanoparticles, and emulsions containing cytotoxic compounds. Use of these conjugated vector-antibody systems for the treatment of cancer is designed to target cancerous cells while sparing healthy cells. We present here a discussion on the synergy between biotechnology and modern molecular pharmotechnology, opening new horizons for therapy.

Selection of aptamers with high affinity and high specificity against C595, an anti-MUC1 IgG3 monoclonal antibody, for antibody targeting

Targeting of antibodies has found a number of applications in assays, anti-idiotypic therapies and vaccine design with a number of anti-idiotypic Abs generated and used in clinical applications, and some currently in clinical trials. Meanwhile, aptamers are a novel and particularly interesting targeting modality, with a unique ability to bind to a variety of targets. Aptamers offer unique benefits compared to other targeting agents, due to their high affinity and selectivity, relatively small size and in vitro synthesis, making them attractive alternatives to Abs and peptides. Aptamers have already been selected against a number of Abs for various applications. We now present a novel methodology for the selection of aptamers against Abs, which minimises the number of steps used and results in molecules that bind to the target Ab with high affinity and specificity. We have used the well-characterised anti-MUC1 monoclonal Ab C595 as an exemplar for raising aptamers against Abs. The methodology is based on the adsorption of the Ab to the surface of a PCR tube and the performance of SELEX selections in the PCR tube, based on elution steps resulting from the denaturation of the Ab on the first PCR amplification cycle. After 10 rounds of selection and amplification, selected aptamers have been characterised using a number of techniques, including fluorescence quenching, ELISA and competition ELISA procedures and a FRET type assay. Aptamers were found to bind their target Ab with a higher affinity than its natural antigenic peptide, as observed in fluorescent quenching and FRET experiments. Furthermore, they were able to displace the antigens from the antibody binding pocket in competition assays. This methodology offers the possibility of rapidly selecting aptamers for antibody targeting that could be used as diagnostic, imaging or therapeutic agents, or as recognition units in immunoassays, and can be potentially useful in raising aptamers against other protein targets.

A novel peptide specifically binding to nasopharyngeal carcinoma for targeted drug delivery

Nasopharyngeal carcinoma (NPC) is a common cancer among Chinese living in southern China, Taiwan, and Singapore. The 5-year survival rate in the early stage of NPC has been reported as high as 90 to 95% with the use of radiotherapy, but in the advanced cases, even with the use of both chemotherapy and radiotherapy, the survival rate is still <50%. To improve the survival rate, we identify a 12-mer peptide (L-peptide) specifically binding to NPC cells with a phage displayed random peptide library. The L-phage and synthetic L-peptide bound to the tumor cell surfaces of most NPC cell lines and biopsy specimens, but not normal nasal mucosal cells, and the L-peptide-linked liposomes containing fluorescent substance (L-peptide-Lipo-HPTS) were capable of binding to and translocating across plasma membranes. L-Peptide-linked liposomes that carried doxorubicin (L-peptide-Lipo-Dox) caused marked cytotoxicity in NPC cells. In SCID mice bearing NPC xenografts, the L-phages specifically bound to the tumor mass, an effect that was inhibited by competition with synthetic L-peptide. In addition, the L-peptide-Lipo-Dox suppressed tumor growth better than Lipo-Dox. These results indicate that the novel L-peptide specifically binds NPC cells and is a good candidate for targeted drug delivery to NPC solid tumors.

In vitro cytotoxic study of immunoliposomal doxorubicin targeted to human CD34+ leukemic cells

The expression of CD34 antigen in acute myelogenous leukemias is considered an unfavourable prognosis marker for response to anticancer drugs and duration of remission. This study investigated the applicability of long-circulating immunoliposomes loaded with doxorubicin targeted to CD34 antigen present on MDR(+) human myelogenous leukemia KG-1a cell line. Immunoliposomal doxorubicin showed a higher cytotoxicity against KG-1a cells than non-targeted liposomal doxorubicin, but it did not improve over that of free drug. Although no reversal of doxorubicin resistance was found to occur through its liposomal encapsulation, a therapeutic benefit can be obtained by the selective cytotoxicity observed. Endocytosis studies demonstrated that, after binding to CD34 antigen, the immunoliposomes are not internalized by the KG-1a cells and so the cytotoxic effect might be due to drug released into the space near the cell membrane. Thus, immunotargeting of liposomal doxorubicin to CD34(+) leukemic cells may only provide an ex vivo strategy for site-selective CD34(+) leukemia cell killing.

Loading mitomycin C inside long circulating hyaluronan targeted nano-liposomes increases its antitumor activity in three mice tumor models

The frequent overexpression of the hyaluronan receptors CD44 and RHAMM in cancer cells opens the door for targeting by the naturally-occurring high-M(r) hyaluronan. This is the first time effective in vivo tumor targeting is reported for mitomycin C (MMC) loaded inside nano-sized hyaluronan-liposomes (denoted tHA-LIP). The severe adverse effects of free MMC made it a rational candidate for an effective targeted carrier. In vitro, loading MMC inside tHA-LIP increased drug potency 100-fold, in cells overexpressing, but not in cells underexpressing, hyaluronan receptors. Both types of liposomes were non-toxic and reduced MMC-related toxicity in healthy C57BL/6 mice. In 3 tumor models, BALB/c bearing C-26 solid tumors; C57BL/6 bearing B16F10.9 or (separately) D122 lung metastasis, tHA-LIP were long-circulating, 7-fold and 70-fold longer than nt-LIP and free MMC, respectively. tHA-LIP-mediated MMC accumulation in tumor-bearing lungs was 20% of injected dose, compared to 0.6% and 4% with free drug and nt-LIP, respectively. Tumor-free lungs showed low accumulation, irrespective of drug formulation. Key indicators of therapeutic responses, tumor progression, metastatic burden and survival, were superior (p < 0.001) in animals receiving MMC-loaded tHA-LIP, no treatment, MMC-loaded nt-LIP and free drug. In conclusion, tHA-LIP perform as tumor-targeted carriers, with promising prospects for treatment of tumors overexpressing hyaluronan receptors.

Ligand-targeted liposomal anticancer drugs

Antibody or ligand-mediated targeting of liposomal anticancer drugs to antigens expressed selectively or over-expressed on tumor cells is increasingly being recognized as an effective strategy for increasing the therapeutic indices of anticancer drugs. This review summarizes some recent advances in the field of ligand-targeted liposomes (LTLs) for the delivery of anticancer drugs. New approaches used in the design and optimization of LTLs is discussed and the advantages and potential problems associated with their therapeutic applications are described. New technologies are widening the spectrum of ligands available for targeting and are allowing choices to be made regarding affinity, internalization and size. The time is rapidly approaching where we will see translation of anticancer drugs entrapped in LTLs to the clinic.

Enhanced gene delivery to HER-2-overexpressing breast cancer cells by modified immunolipoplexes conjugated with the anti-HER-2 antibody

Cationic liposome-mediated gene delivery to tumors has met with only limited success due to the low transfection efficiency and lack of target specificity. We developed a gene delivery system for HER-2-overexpressing cells by adding modified anti-HER-2 Fab' fragments to liposome/DNA complexes (lipoplexes). The modified anti-HER-2-Fab' was conjugated to liposomes containing cationic lipids such as 1,2-dioleoyl-3-(trimethylammonium) propane and cholesterol (1:1 w/w) using a maleimido-polyethyleneglycol-3400-1,2-dioleoyl-3-sn-phosphatidylethanolamine linker. The specific modification constricted the sizes of these immunolipoplexes to a range of 0.3- 0.7 microm, and they remained stable for a longer duration of time compared to the lipoplex controls (0.8-3.2 microm at 4 h). In addition, a 10-fold increase in luciferase activity was achieved after transfecting human breast cancer SK-BR3 cells with immunolipoplexes as compared to the control lipoplexes. Flow cytometry analysis demonstrated that 80% of SK-BR3 cells expressed the green fluorescent protein (GFP) 48 h after being transfected with immunolipoplexes, while only 40% of those with control lipoplexes and 3% of those with naked DNA alone expressed GFP. Furthermore, the anti-HER-2 immunolipoplexes showed specific enhancement of transfection efficiency in HER-2-overexpressing SK-BR3 cells (a 6-fold increase in luciferase activity) but not in HER-2-negative MCF-7 breast cancer cells. The enhancement of gene delivery by anti-HER-2 immunoliposomes was not affected by the presence of serum. These results demonstrate the feasibility of improving target-specific gene delivery to HER-2-overexpressing cells by insertion of lipid-modified anti-HER-2-Fab' into the preformed liposomes.

Translocation of liposomes into cancer cells by cell-penetrating peptides penetratin and tat: a kinetic and efficacy study

Unlike conventional liposomes, sterically stabilized liposomes, with their smaller volume of distribution and reduced clearance, preferentially convey encapsulated drugs into tumor sites. Despite these improvements, intracellular delivery is hampered by the stable drug retention of the liposomes, which diminishes the efficacy of the liposomal drug. To facilitate uptake of liposomal drugs into cells, two cell-penetrating peptides, penetratin (PEN) and TAT, derived from the HIV-1 TAT protein, were studied. In contrast to control peptides, both TAT and PEN enhanced the translocation efficiency of liposomes in proportion to the number of peptides attached to the liposomal surface. A peptide number of as few as five could enhance the intracellular delivery of liposomes. The kinetics of uptake was peptide- and cell-type dependent. Intracellular accumulation of TAT-liposomes increased with incubation time, but PEN-liposomes peaked at 1 h and then declined gradually. After treatment with 1 microg/ml doxorubicin equivalents of liposome for 2 h, TAT increased the doxorubicin uptake of A431 cells by 12-fold. However, the improvement of uptake of liposomal doxorubicin was not reflected by cytotoxicity in vitro or tumor control in vivo. Our results demonstrated that merely adding CPP to a liposome encapsulating anticancer drug was inadequate in improving its antitumor activity. An additional approach to enhance the intracellular release of the encapsulated drug is obviously necessary.

Simple and efficient liposomal encapsulation of topotecan by ammonium sulfate gradient: stability, pharmacokinetic and therapeutic evaluation

Topotecan (TPT), a topoisomerase I inhibitor, is presently undergoing clinical evaluation worldwide. Previous studies have shown that entrapping TPT within multi-lamellar vesicle liposome can stabilize the lactone moiety, which is structurally important for biological activity. However, low drug:lipid ratios due to the amphipathic character and small entrapment volume in the unilamellar vesicle limits the development of pharmaceutically acceptable liposomal formulation. With an aim to improve on this drawback, we herein describe a method that utilizes the ammonium sulfate gradient to entrap TPT into liposomes. By this method, the encapsulation efficiency was over 90% and a drug:lipid molar ratio as high as 1:5.4 was reached. In comparison with free drug, liposome-encapsulated TPT is more stable in physiological conditions and shows higher in vitro cytotoxicity. Because of increased blood circulation time, the initial plasma concentration and area under the plasma concentration of liposomal drugs were 14 and 40 times, respectively, of those of free drug. Furthermore, liposome encapsulation enhanced the antitumor activity of TPT in syngeneic murine C-26 and human HTB-9 xenograft models in vivo. At a dose of 5 mg/kg, the tumor growth delay of liposomal formulation was significantly than that of free TPT. Based on these results, we believe that this liposomal TPT formulation is worthy of further clinical study.

Preparation of long-circulating immunoliposomes using PEG-cholesterol conjugates: effect of the spacer arm between PEG and cholesterol on liposomal characteristics

Poly(ethylene glycol)-coated liposomes were prepared with two new synthesised pegylated cholesterol (Chol) derivatives linked via carbamate bond. Poly(ethylene glycol) (PEG) was directly linked to Chol (PEG-Chol) or through a space arm of diaminebutane (PEG-L-Chol). In buffer, the physicochemical properties of PC/Chol liposomes (2/1, molar ratio) containing up to 10 mol% of pegylated Chol derivatives did not change significantly and the PEG layer at liposome surface inhibited the agglutination of biotin-liposomes induced by streptavidin. On the other hand, in serum, PEG-L-Chol seemed to reduce the interactions of liposomes with serum proteins, much more than PEG-Chol. The low steric hindrance of PEG-Chol derivative may be due to the slow conformational transition rate of the polymer, since PEG may be deeper located in the membrane. The coupling efficiency of the ligand to the functionalised amino group at the polymer end was also affected, but, its antigen-binding activity was preserved. The basic physical-chemical characteristics studied in this work are relevant to assess the application of pegylated Chol liposomes as drug delivery systems.

In vitro and in vivo comparison of immunoliposomes made by conventional coupling techniques with those made by a new post-insertion approach

Ligand-targeted liposomes have the potential to increase the therapeutic efficacy of antineoplastic agents. Recently, a combinatorial approach to the preparation of ligand-targeted liposomes has been developed, termed the post-insertion technique, which will facilitate the production of targeted liposomes. In this paper, Stealth immunoliposomes (SIL) coupled to anti-CD19 made by either a conventional coupling technique (SIL[anti-CD19]), or by the post-insertion technique (PIL[anti-CD19], were compared with respect to their in vitro binding and cytotoxicity and their ability to improve in vivo survival in tumor-bearing mice. The in vitro binding and uptake of PIL[anti-CD19] by CD19-expressing, B-cell lymphoma (Namalwa) cells was similar to that of SIL[anti-CD19] and both were significantly higher than binding of non-targeted liposomes (SL). In addition, no significant differences were found between the respective in vitro cytotoxicities of doxorubicin-loaded PIL[anti-CD19] or SIL[anti-CD19], or in their in vivo therapeutic efficacy in a murine model of human B-lymphoma. Overall, the results demonstrate that the post-insertion technique is a simple, flexible and effective means for preparing targeted liposomal drugs for clinical applications.

Recombinant antibodies: a novel approach to cancer diagnosis and therapy

Recombinant antibodies and their fragments currently represent over 30% of all biological proteins undergoing clinical trials for diagnosis and therapy. These reagents dominate the cancer-targeting field, as highlighted by the recent approval of the first engineered therapeutic antibodies by the Food and Drugs Administration (FDA). Last year, important advances have been made in the design, selection and production of recombinant antibodies. The natural immune repertoire and somatic cell affinity maturation has been superseded by large antibody display libraries and rapid molecular evolution strategies. These novel libraries and selection methods have enabled the rapid isolation of high-affinity cancer targeting and antiviral antibodies, the latter capable of redirecting viruses for gene therapy applications. In alternative strategies for cancer diagnosis and therapy, recombinant antibody fragments have been fused to radioisotopes, drugs, toxins, enzymes and biosensor surfaces. Antibody-directed cancer pre-targeting followed by prodrug activation (ADEPT) has proved a most promising therapeutic strategy. Multi-specific antibodies have been effective for cytotoxic T-cell recruitment and antibody-fusion proteins have delivered enhanced immunotherapeutic and vaccination strategies. The new millennium is indeed an exciting time for the design, selection and formulation of a range of new antibody-based products for cancer diagnosis and therapy.

Molecular imaging of stretch-induced tissue factor expression in carotid arteries with intravascular ultrasound

RATIONALE AND OBJECTIVES

Molecular imaging with targeted contrast agents enables tissues to be distinguished by detecting specific cell-surface receptors. In the present study, a ligand-targeted acoustic nanoparticle system is used to identify angioplasty-induced expression of tissue factor by smooth muscle cells within carotid arteries.

METHODS

Pig carotid arteries were overstretched with balloon catheters, treated with tissue factor-targeted or a control nanoparticle system, and imaged with intravascular ultrasound before and after treatment.

RESULTS

Tissue factor-targeted emulsions bound and increased the echogenicity and gray-scale levels of overstretched smooth muscle cells within the tunica media, versus no change in contralateral control arteries. Expression of stretch-induced tissue factor in carotid artery media was confirmed by immunohistochemistry.

CONCLUSIONS

The potential for abnormal thrombogenicity of balloon-injured arteries, as reflected by smooth muscle expression of tissue factor, was imaged using a novel, targeted, nanoparticulate ultrasonic contrast agent.

Pegylated liposomal doxorubicin in treating a case of advanced hepatocellular carcinoma with severe hepatic dysfunction and pharmacokinetic study

BACKGROUND

There is lack of effective and safe chemotherapy for advanced hepatocellular carcinoma. Polyethylene glycol-coated (pegylated) liposomal doxorubicin (PLD) has long circulation time and enhanced drug accumulation in the tumor tissues. It has significant activity in Kaposi's sarcoma, breast and ovarian cancers and the acute adverse effects of free drug are reduced.

PATIENTS AND METHODS

A patient with advanced hepatocellular carcinoma was treated with PLD and a pharmacokinetic study was performed. Initial serum total and direct bilirubin were 3.6 and 6.8 folds of upper normal, respectively, and an indocyanine green clearance test at 15 minutes was 26.3% (normal < 15%).

RESULTS

Compared to cases with normal liver function, increased volume of distribution of doxorubicin correlated with a large amount of ascites (P < 0.05). The clearance of drug was unexpectedly higher than in cases with normal liver function (P < 0.05). According to the pharmacokinetic studies, the disposition of PLD in this case has not been retarded even in the presence of severe liver dysfunction. Only minimal toxicities including grade 2 stomatitis and moderate leukopenia were observed. The tumor had a partial remission and the patient survived nine months after PLD treatment.

CONCLUSION

PLD could serve as a safe and effective treatment for hepatocellular carcinoma even in the presence of impaired liver function. Its role in treating advanced hepatocellular carcinoma is worthy of further study.

Immunoliposomes for the targeted delivery of antitumor drugs

This review presents an overview of the field of immunoliposome-mediated targeting of anticancer agents. First, problems that are encountered when immunoliposomes are used for systemic anticancer drug delivery and potential solutions are discussed. Second, an update is given of the in vivo results obtained with immunoliposomes in tumor models. Finally, new developments on the utilization of immunoliposomes for the treatment of cancer are highlighted.

Monoclonal antibody drug conjugates in the treatment of cancer

Monoclonal antibodies directed to tumor-associated antigens have been chemically conjugated to drugs with different mechanisms of action and different levels of potency. Monoclonal-antibody-directed drug delivery has the potential to both improve efficacy and reduce systemic toxicity. Several immunoconjugates have demonstrated impressive antigen-specific antitumor activity in preclinical models. Phase I trials of a calicheamicin immunoconjugate for treatment of acute myeloid leukemia and a doxorubicin immunoconjugate for treatment of carcinoma have recently been completed.

Recombinant antibody constructs in cancer therapy

Recombinant antibodies and their fragments now represent over 30% of all biological proteins undergoing clinical trials for diagnosis and therapy. The focus on antibodies as the ideal cancer-targeting reagents recently culminated in approval by the Food and Drugs Administration for the first engineered therapeutic antibodies. In the past year, important advances have been made in the design, selection and production of new types of engineered antibodies. Innovative selection methods have enabled the isolation of high-affinity cancer-targeting and antiviral antibodies, the latter capable of redirecting viruses for gene therapy applications. In other strategies for cancer diagnosis and therapy, recombinant antibody fragments have been fused to radioisotopes, drugs, toxins, enzymes and biosensor surfaces. Bispecific antibodies and related fusion proteins have been produced for cancer immunotherapy, effectively enhancing the human immune response in anticancer vaccines and T cell recruitment strategies.