Search

Accumulation of liposomal drugs into human tumors has substantial variability influencing the probability of positive response to the therapy. Therefore, it becomes very important to identify the eligibility of patients for various treatment options. The existing strategies of tumor stratification using companion diagnostics are based on the assumption that the initial and subsequent doses of nanoparticles (NP) behave in a sufficiently similar manner to enable a valuable prognosis. Here, we use a combination of in vivo imaging techniques to validate the applicability of magnetic liposomes (ML) as a reliable tool to predict whether or not the tumor would respond to nanomedicine therapy. The results demonstrated that liposome biodistribution, interactions with immune cells, and extravasation behavior in tumors were not affected by the pretreatment with liposomes 24 h prior to the repeat dosing. Co-administration of liposomal doxorubicin (DXR) and liposomes loaded with maghemite NP resulted in a high colocalization rate between two nanomedicines in tumors suggesting that neither contrast agent, nor chemotherapeutics altered biodistribution of liposomes. Based on magnetic resonance imaging of 4T1 tumors performed before and 6 h after ML treatment, animals were classified into high and low accumulation subgroups. Higher ML deposition in tumors was associated with a reduction in lesion size and enhanced survival in animals treated with liposomal DXR, but not with DXR alone. Given that liposomes are the most numerous class of clinically approved nanomedicines the development of safe and cost-effective liposomal companion diagnostic suitable for non-invasive imaging is of paramount importance for improving the efficacy of cancer therapy., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Liposomes are the most extensively used nanocarriers in cancer therapy. Despite the advantages these vehicles provide over free drugs, there are still limitations with regards to the efficiency of liposomes delivery to tumors and off-target accumulation. A better understanding of nanodrugs extravasation mechanisms in different tumor types and normal vessels is needed to improve their antitumor activity. We used intravital microscopy to track for fluorescent liposomes behavior in xenograft tumor models (murine breast cancer 4T1 and melanoma B16, human prostate cancer 22Rv1) and normal skin and identified two distinct extravasation patterns. Microleakage, a local perivascular nanoparticle deposition, was found both in malignant and healthy tissues. This type of liposomes leakage does not provide access to tumor cells and is presumably responsible for drug deposition in normal tissues. In contrast, macroleakage penetrated deep into tissues and localized predominantly on the tumor-host interface. Although neutrophils did not uptake liposomes, their extravasation appeared to initiate both micro- and macroleakages. Based on neutrophils and liposomes extravasation dynamics, we hypothesized that microleakage and macroleakage are subsequent steps of the extravasation process corresponding to liposomes transport through endothelial and subendothelial barriers. Of note, extravasation spots were detected more often in the proximity of neutrophils, and across studied tumor types, neutrophils counts correlated with leakage frequencies. Reduced liposomes accumulation in 4T1 tumors upon Ly6G depletion further corroborated neutrophils role in nanoparticles delivery. Elucidating liposomes extravasation routes has a potential to help improve existing strategies and develop effective nanodrugs for cancer therapy.

We studied internalization of vector nanocarriers loaded with plasmid DNA into C6 glioma cells. For improving selectivity of plasmid delivery, the liposomes were conjugated with monoclonal antibodies to VEGF and its receptor VEGFR2. Flow cytofluorometry and laser scanning confocal microscopy showed more intensive (more than 2-fold) internalization and accumulation of antibody-vectorized liposomes in C6 glioma cells in comparison with the control (liposomes conjugated with non-specific antibodies and non-vectorized liposomes). Using quantitative analysis of fluorescent signal, we showed that cationic immunoliposomes significantly more effective delivered pCop-Green-N plasmid DNA and ensured effective transfection of C6 glioma cells.

Targeted delivery of anticancer drugs to brain tumors, especially glioblastoma multiforme, which is the most frequent and aggressive type, is one of the important objectives in nanomedicine. Vascular endothelial growth factor (VEGF) and its receptor type II (VEGFR2) are promising targets because they are overexpressed by not only core tumor cells but also by migrated glioma cells, which are responsible for resistance and rapid progression of brain tumors. The purpose of the present study was to develop the liposomal drug delivery system combining enhanced loading capacity of cisplatin and high binding affinity to glioma cells. This was achieved by using of highly soluble cisplatin analogue, cis-diamminedinitratoplatinum(II), and antibodies against the native form of VEGF or VEGFR2 conjugated to liposome surface. The developed drug delivery system revealed sustained drug release profile, high affinity to antigens, and increased uptake by glioma C6 and U-87 MG cells. Pharmacokinetic study on glioma C6-bearing rats revealed prolonged blood circulation time of the liposomal formulation. The above features enabled the present drug delivery system to overcome both poor pharmacokinetics typical for platinum formulations and low loading capacity typical for conventional liposomal cisplatin formulations.

The efficiency of conventional chemotherapy for aggressive tumors in the CNS remains low and new strategies for the targeted delivery of anti-tumor substances are now actively developed. Pegylated liposomes covalently conjugated with monoclonal antibodies to VEGF synthesized by us are nanoparticle characterized by narrow size distribution and high dispersion stability. Immunochemical activity of antibodies after conjugation was 70% of initial level. The anti-VEGF liposomes developed by us were highly specific for VEGF(+) tumor cells (in vitro and in vivo). Intravenous injection of VEGF-liposomes to rats with intracranial C6 glioma was followed by their specific accumulation in the malignant tissues and engulfment by glioma cells, which attested to target delivery and selective accumulation of anti-VEGF-liposomes in the brain tumor. Thus, the use of targeting molecules can significantly increase the distribution and efficiency of delivery of nanocontainers to a tumor characterized by hyperexpression of the target proteins.

The selectivity of PEGylated immunoliposomes based on monoclonal antibodies against GFAP and the E2 extracellular loop of connexin 43 (MAbE2Cx43) with respect to the focus of a glioma was estimated in experiments on animals with intracranial C6 glioma. Stealth immunoliposomes were labeled with 2 alternative labels, a fluorescent (Dil C18) and a paramagnetic (Gd-DTPA) one. Fluorescent-labeled liposomal nanocontainers were detected at the periphery of the glioma, where the target antigens were overexpressed, 48 hours after injection. Dynamic T1 MRI of rats injected with paramagnetic immunoliposomes carrying MAbE2Cx43 showed distinct accumulation of the paramagnetic contrast agent at the periphery of the glioma, which began 6 hours after administration. These data suggest that immunoliposomal nanocontainers based on antibodies against GFAP and the E2 extracellular fragment of connexin 43 are suitable for targeted delivery of diagnostic and therapeutic drugs to the peritumoral invasion zone of high-grade gliomas., From the Clinical Editor: PEGylated immunoliposomes based on monoclonal antibodies against GFAP and the E2 extracellular loop of connexin 43 were investigated in animals with intracranial C6 glioma. These immunoliposomal nanocontainers were found suitable for targeted delivery of diagnostic and therapeutic drugs to the peritumoral invasion zone of high-grade gliomas., (2012 Elsevier Inc. All rights reserved.)

Immunoliposomal container system for targeted delivery of minor interfering RNA into Schwann cells was developed. Monoclonal antibodies to myelin basic protein served as the vector. Analysis by sandwich ELISA of myelin basic protein showed specific suppression of the target protein gene expression in Schwann cells after incubation with PEG-conjugated immunoliposomes loaded with minor interfering RNA blocking the synthesis of myelin basic protein. Prospects of effective use of this system for targeting of minor interfering RNA for the treatment of diseases of genetic etiology are discussed.

PEGylated (stealth) immunoliposomes covalently linked to antibodies against human gliofibrillary acidic protein (GFAP) were prepared by coupling the thiolated monoclonal anti-GFAP antibodies, D4, with a maleimide derivative of the phosphatidyl ethanolamine of the liposomal membrane. Depending on the initial protein-to-lipid ratios, the immunoliposomes prepared (with a diameter of about 70 nm) were coupled with 60 to 240 molecules of the antibodies. In vitro experiments with cultures of the embryonic rat brain astrocytes demonstrated a specific binding of these immunoliposomes, which could be inhibited by the preincubation of the cells with free non-coupled D4 but not with non-specific antibodies. Administered intravenously into rats, the immunoliposomes exhibited a kinetic behaviour typical for the PEGylated liposomes: after 24 h, approximately 20% of the doses injected were still present in the blood; the elimination rate constants were 0.05-0.09 h(-1), the elimination half-lives were 8-15 h. With such a systemic longevity, as well as with such a specificity, these immunoliposomes, non-penetrating through intact blood-brain barrier (BBB), should be useful in delivering pharmacological agents to glial brain tumours (which continue to express GFAP) or to other pathological loci in the brain with a partially disintegrated BBB.

Polyethylene glycol (PEG)ylated (stealth) immunoliposomes directed against human gliofibrillary acidic protein (GFAP) were prepared by coupling the thiolated monoclonal anti-GFAP antibodies with a maleimide derivative of phosphatidyl ethanolamine of the liposomal membrane. Experiments with cell cultures demonstrated specific and competitive binding of these immunoliposomes to embryonic rat brain astrocytes. Administered intravenously into rats, the immunoliposomes displayed typical kinetics with elimination half-lives of 8-15 hr. Being incapable of penetrating the unimpaired blood-brain barrier (BBB), these immunoliposomes, nevertheless, may be useful in delivering drugs to glial brain tumors (which continue to express GFAP) or to other pathological loci in the brain with a partially disintegrated BBB.

Anthracycline antibiotics with significant antitumor activity are widely used for treatment of various oncologic diseases in spite of their poor pharmacokinetics and severe side-effects. To improve the efficacy of treatment of oncologic patients, liposomal formulations of the anthracycline antibiotics, such as Doxil, TLC D-99, and DaunoXome, have been developed. Pharmacokinetic parameters of liposomal doxorubicin and daunorubicin differ markedly from the parameters of their free formulations. Liposomal anthracyclines display a prolonged circulation time, reduced clearance, smaller volume of distribution, and lower toxicity. Doxil and DaunoXome have been licensed for treatment of AIDS-related Kaposi's sarcoma. Entrapment of anthracycline antibiotics into liposomes coupled with monoclonal antibodies enhances their uptake by tumor cells.

The attempts to use liposomes as containers for the transport of therapeutic drugs have been undertaken during the recent 40 years. However, the first success was achieved only in the 80-ies, when the sterically stabilized liposomes were invented. It was found that the liposome biological layer modified through, adding to it, certain polymers prolonged the blood circulation and reduced the capture of liposomes by RES cells. Elaboration of immunoliposomes, i.e. those conjugated with antibodies, was the next step in the path of perfecting the liposomes as a transport tool for the sake of binding with target-cells and to ensure the address-oriented delivery of drugs to a pathology focus. Preclinical and clinical testing of liposome-form of antitumor drugs witnessed to their lower toxicity and better pharmacokinetic indices; besides, they selectively accumulate themselves in tumor cells and have a more pronounced therapeutic effect even at lower doses of drugs in case of tumors resistant to the already made chemotherapy.