Oxaliplatin targeting to angiogenic vessels by PEGylated cationic liposomes suppresses the angiogenesis in a dorsal air sac mouse model

Platinum-based chemotherapy: trends in organic nanodelivery systems

Despite the investment in platinum drugs research, cisplatin, carboplatin and oxaliplatin are still the only Pt-based compounds used as first line treatments for several cancers, with a few other compounds being approved for administration in some Asian countries. However, due to the severe and worldwide impact of oncological diseases, there is an urge for improved chemotherapeutic approaches. Furthermore, the pharmaceutical application of platinum complexes is hindered by their inherent toxicity and acquired resistance. Nanodelivery systems rose as a key strategy to overcome these challenges, with recognized versatility and ability towards improving the safety, bioavailability and efficacy of the available drugs. Among the known nanocarriers, organic systems have been widely applied, taking advantage of their potential as drug vehicles. Researchers have mainly focused on the development of lipidic and polymeric carriers, including supramolecular structures, with an overall improvement of encapsulated platinum complexes. Herein, an overview of recent trends and strategies is presented, with the main focus on the encapsulation of platinum compounds into organic nanocarriers, showcasing the evolution in the design and development of these promising systems. This comprehensive review highlights formulation methods as well as characterization procedures, providing insights that may be helpful for the development of novel platinum nanocarriers aiming at future pharmaceutical applications.

Selective Protein of Interest Degradation through the Split-and-Mix Liposome Proteolysis Targeting Chimera Approach

Proteolysis Targeting Chimera (PROTAC) technology represents a promising new approach for target protein degradation using a cellular ubiquitin-proteasome system. Recently, we developed a split-and-mix nanoplatform based on peptide self-assembly, which could serve as a self-adjustable platform for multifunctional applications. However, the lower drug efficacy limits further biomedical applications of peptide-based SM-PROTAC. In this study, we develop a novel split-and-mix PROTAC system based on liposome self-assembly (LipoSM-PROTAC), concurrent with modification of FA (folate) to enhance its tumor-targeting capabilities. Estrogen receptors (ERα) were chosen as the protein of interest (POI) to validate the efficacy of Lipo degraders. Results demonstrate that this PROTAC can be efficiently and selectively taken up into the cells by FA receptor-positive cells (FR+) and degrade the POI with significantly reduced concentration. Compared to the peptide-based SM-PROTACs, our designed LipoSM-PROTAC system could achieve therapeutic efficacy with a lower concentration and provide opportunities for clinical translational potential. Overall, the LipoSM-based platform shows a higher drug efficacy, which offers promising potential applications for PROTAC and other biomolecule regulations.

Doxorubicin-loaded liposomes surface engineered with the matrix metalloproteinase-2 cleavable polyethylene glycol conjugate for cancer therapy

Background

Colorectal cancer is one of the prominent leading causes of fatality worldwide. Despite recent advancements within the field of cancer therapy, the cure rates and long-term survivals of patients suffering from colorectal cancer have changed little. The application of conventional chemotherapeutic agents like doxorubicin is limited by some drawbacks such as cardiotoxicity and hematotoxicity. Therefore, nanotechnology has been exploited as a promising solution to address these problems. In this study, we synthesized and compared the anticancer efficacy of doxorubicin-loaded liposomes that were surface engineered with the 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-matrix metalloproteinase-2 (MMP-2) cleavable peptide-polyethylene glycol (PEG) conjugate. The peptide linker was used to cleave in response to the upregulated MMP-2 in the tumor microenvironment, thus exposing a positive charge via PEG-deshielding and enhancing liposomal uptake by tumor cells/vasculature. Liposomal formulations were characterized in terms of size, surface charge and morphology, drug loading, release properties, cell binding and uptake, and cytotoxicity.

Results

The formulations had particle sizes of ~ 100-170 nm, narrow distribution (PDI ˂ 0.2), and various surface charges (- 10.2 mV to + 17.6 mV). MMP-2 overexpression was shown in several cancer cell lines (C26, 4T1, and B16F10) as compared to the normal NIH-3T3 fibroblast cells by gelatin zymography and qRT-PCR. In vitro results demonstrated enhanced antitumor efficacy of the PEG-cleavable cationic liposomes (CLs) as compared to the commercial Caelyx^® (up to fivefold) and the chick chorioallantoic membrane assay showed their great antiangiogenesis potential to target and suppress tumor neovascularization. The pharmacokinetics and efficacy studies also indicated higher tumor accumulation and extended survival rates in C26 tumor-bearing mice treated with the MMP-2 cleavable CLs as compared to the non-cleavable CLs with no remarkable sign of toxicity in healthy tissues.

Conclusion

Altogether, the MMP-2-cleavable CLs have great potency to improve tumor-targeted drug delivery and cellular/tumor-vasculature uptake which merits further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12645-023-00169-8.

Oral administration of sodium bicarbonate can enhance the therapeutic outcome of Doxil® via neutralizing the acidic tumor microenvironment

The pH of the tumor microenvironment in solid tumors is reported to be more acidic than that of normal tissues. The pH is controlled by over-expression of several transporters that are associated with the progression, angiogenesis, and metastasis of solid tumors. Antitumor effects of weak-base anticancer agents, such as doxorubicin (DXR), could be reduced in an acidic environment because of increases in the ionized form of the drug under these conditions, reducing its membrane penetrability. In our previous studies, we demonstrated that oral administration of sodium bicarbonate (NaHCO₃) can neutralize the acidic tumor microenvironment and enhance the effects of small molecule anticancer drugs. However, it is not known whether or not increasing the tumor pH by oral administration of NaHCO₃ leads to enhanced antitumor effects of lipidic nanoparticle formulations of weak-base anticancer drugs, such as Doxil®. In this study, we investigated the antitumor efficacy of Doxil® in combination with oral administration of NaHCO₃ in a Colon26 tumor-bearing mouse model. NaHCO₃ clearly enhanced the tumor-growth inhibitory effect of Doxil® without exacerbating any systemic side effects. In vitro studies indicated that high levels of DXR were internalized into cells at neutral pH. These studies demonstrate that the neutralization of acidic tumor microenvironment by an oral administration of NaHCO₃ could be a promising approach to enhance the therapeutic outcomes of Doxil®.

In vitro and in vivo Evaluation of a Novel Estrogen-Targeted PEGylated Oxaliplatin Liposome for Gastric Cancer

Background

Chemotherapy is still the main first-line treatment for advanced metastatic gastric cancer, but it has the limitations of serious side effects and drug resistance. Conventional liposome has been substantially used as drug carriers, but they lack targeting character with lower drug bioavailability in tumor tissues. Based on the above problems, a novel estrogen-targeted PEGylated liposome loaded with oxaliplatin (ES-SSL-OXA) was prepared to further improve the metabolic behavior, the safety profile, and the anti-tumor efficacy of oxaliplatin.

Methods

Four kinds of oxaliplatin (OXA) liposomes were prepared by film hydration method. The obtained formulations were characterized in terms of entrapment efficiency (EE), particle size, and so on by HPLC and DLS (dynamic light scanning). The morphology of ES-SSL-OXA was detected by transmission electron microscope (TEM). The in vitro and in vivo targeting effect of ES-SSL-OXA was verified by fluorescence microscopy and in vivo imaging system in gastric cancer cells (SGC-7901) and tumor-bearing athymic mice. The in vitro and in vivo antitumor efficacies of ES-SSL-OXA were investigated on SGC-7901 cells and athymic tumor-bearing mice. Pharmacokinetic, biodistribution, and acute toxicity tests of ES-SSL-OXA were performed on ICR mice.

Results

The ES-SSL-OXA exhibited an average particle size of about 153.37 nm with an encapsulation efficiency of 46.20% and low leakage rates at 4°C and 25°C. In vivo and in vitro targeting study confirmed that ES-SSL-OXA could effectively target the tumor site. The antitumor activity demonstrated the strongest inhibition in tumor growth of ES-SSL-OXA. Pharmacokinetics and acute toxicity study showed that ES-SSL-OXA could significantly improve the metabolic behavior and toxicity profile of oxaliplatin.

Conclusion

In this study, a novel estrogen-targeted long-acting liposomal formulation of OXA was successfully prepared. ES fragment effectively targeted the delivery system to tumor tissues which highly express estrogen receptor, providing a promising therapeutic method for gastric cancer in clinic.

Liposomalization of Oxaliplatin Exacerbates the Non-Liposomal Formulation-Induced Decrease of Sweet Taste Sensitivity in Rats

Here, we investigated whether or not the characteristics of the oxaliplatin-induced sweet taste sensitivity were altered by PEGylated liposomalization of oxaliplatin (liposomal oxaliplatin), which enhances its anticancer efficacy. Liposomal oxaliplatin and oxaliplatin were intravenously and intraperitoneally, respectively, administered to male Sprague-Dawley rats at the total dose of 8 mg/kg. A brief-access test for evaluation of sweet taste sensitivity on day 7 revealed that both liposomal oxaliplatin and oxaliplatin decreased the sensitivity of rats, the degree with the former being greater than in the case of the latter. Liposomalization of oxaliplatin increased the accumulation of platinum in lingual non-epithelial tissues, through which taste nerves passed. The lingual platinum accumulation induced by not only liposomal oxaliplatin but also oxaliplatin was decreased on cooling of the tongue during the administration. In the current study, we revealed that liposomalization of oxaliplatin exacerbated the oxaliplatin-induced decrease of sweet taste sensitivity by increasing the accumulation of platinum/oxaliplatin in lingual non-epithelial tissues. These findings may suggest that reduction of liposomal oxaliplatin distribution to the tongue on cooling during the administration prevents exacerbation of the decrease of sweet taste sensitivity, maintaining the quality of life and chemotherapeutic outcome in patients.

Recent Advancements of Nanomedicine towards Antiangiogenic Therapy in Cancer

Angiogenesis is a process of generation of de-novo blood vessels from already existing vasculature. It has a crucial role in different physiological process including wound healing, embryonic development, and tumor growth. The methods by which therapeutic drugs inhibit tumor angiogenesis are termed as anti-angiogenesis cancer therapy. Developments of angiogenic inhibiting drugs have various limitations causing a barrier for successful treatment of cancer, where angiogenesis plays an important role. In this context, investigators developed novel strategies using nanotechnological approaches that have demonstrated inherent antiangiogenic properties or used for the delivery of antiangiogenic agents in a targeted manner. In this present article, we decisively highlight the recent developments of various nanoparticles (NPs) including liposomes, lipid NPs, protein NPs, polymer NPs, inorganic NPs, viral and bio-inspired NPs for potential application in antiangiogenic cancer therapy. Additionally, the clinical perspectives, challenges of nanomedicine, and future perspectives are briefly analyzed.

Recent advances of nanomedicines for liver cancer therapy

This review highlights recent advancements in nanomedicines for liver cancer therapy.

Antitumor activities of novel glycyrrhetinic acid-modified curcumin-loaded cationic liposomes in vitro and in H22 tumor-bearing mice

At present, the chemotherapy of advanced inoperable liver cancer is limited with serious side effects. Curcumin possesses multiple cancer preventive activities and low safety concerns. However, its poor solubility and instability in water pose significant pharmacological barriers to its clinical application. In this study, we presented a novel delivery system – the glycyrrhetinic acid modified curcumin-loaded cationic liposomes (GAMCLCL) and investigated its antitumor activities on HepG2 cells in vitro and in H22 tumor-bearing mice. The experimental results demonstrated that GAMCLCL was a cationic liposome and could be Intravenous administration. Compared to free curcumin, GAMCLCL exhibited stronger antitumor activities in vitro and in vivo. The antitumor results of GAMCLCL after intravenous administration were very similar to those after intratumoral administration. The main activities of GAMCLCL and curcumin included inhibition of HepG2 cell proliferation, inhibition of tumor growth, reduction of tumor microvascular density, down-regulation of the expression of VEGF protein, and up-regulation of the expression of Caspases3 protein in H22 tumor tissues. Furthermore, GAMCLCL improved the parameters of WBC, RBC, ALT, CRE, LDH of H22 tumor-bearing mice. Curcumin is a nontoxic natural compound with definite antitumor activities, its antitumor effects can be enhanced by preparation of GAMCLCL.

Micro-/nano-sized delivery systems of ginsenosides for improved systemic bioavailability

Ginsenosides, dammarane-type triterpene saponins obtained from ginseng, have been used as a natural medicine for many years in the Orient due to their various pharmacological activities. However, the therapeutic potential of ginsenosides has been largely limited by the low bioavailability of the natural products caused mainly by low aqueous solubility, poor biomembrane permeability, instability in the gastrointestinal tract, and extensive metabolism in the body. To enhance the bioavailability of ginsenosides, diverse micro-/nano-sized delivery systems such as emulsions, polymeric particles, and vesicular systems have been investigated. The delivery systems improved the bioavailability of ginsenosides by enhancing solubility, permeability, and stability of the natural products. This mini-review aims to provide comprehensive information on the micro-/nano-sized delivery systems for increasing the bioavailability of ginsenosides, which may be helpful for designing better delivery systems to maximize the versatile therapeutic potential of ginsenosides.

Intratumoral Visualization of Oxaliplatin within a Liposomal Formulation Using X-ray Fluorescence Spectrometry

Microsynchrotron radiation X-ray fluorescence spectrometry (μ-SR-XRF) is an X-ray procedure that utilizes synchrotron radiation as an excitation source. μ-SR-XRF is a rapid, nondestructive technique that allows mapping and quantification of metals and biologically important elements in cell or tissue samples. Generally, the intratumor distribution of nanocarrier-based therapeutics is assessed by tracing the distribution of a labeled nanocarrier within tumor tissue, rather than by tracing the encapsulated drug. Instead of targeting the delivery vehicle, we employed μ-SR-XRF to visualize the intratumoral microdistribution of oxaliplatin (l-OHP) encapsulated within PEGylated liposomes. Tumor-bearing mice were intravenously injected with either l-OHP-containing PEGylated liposomes (l-OHP liposomes) or free l-OHP. The intratumor distribution of l-OHP within tumor sections was determined by detecting the fluorescence of platinum atoms, which are the main elemental components of l-OHP. The l-OHP in the liposomal formulation was localized near the tumor vessels and accumulated in tumors at concentrations greater than those seen with the free form, which is consistent with the results of our previous study that focused on fluorescent labeling of PEGylated liposomes. In addition, repeated administration of l-OHP liposomes substantially enhanced the tumor accumulation and/or intratumor distribution of a subsequent dose of l-OHP liposomes, presumably via improvements in tumor vascular permeability, which is also consistent with our previous results. In conclusion, μ-SR-XRF imaging efficiently and directly traced the intratumor distribution of the active pharmaceutical ingredient l-OHP encapsulated in liposomes within tumor tissue. μ-SR-XRF imaging could be a powerful means for estimating tissue distribution and even predicting the pharmacological effect of nanocarrier-based anticancer metal compounds.

Platinum (II) complex-nuclear localization sequence peptide hybrid for overcoming platinum resistance in cancer therapy

Platinum therapy represents first line of treatment in many malignancies but its high systemic toxicity limits the therapeutic dosage. Herein, we report the synthesis of carboplatin-like complexes with azide and alkyne functional groups and the formation of a platinum (II) - nuclear localization sequence peptide (Pt-NLS) hybrid to improve the import of platinum (II) complexes directly into the cell's nucleus. The Pt-NLS hybrid successfully enters cells and their nuclei, forming Pt-induced nuclear lesions. The in vitro efficacy of Pt-NLS is high, superior to native carboplatin at the same concentration. The methodology used is simple and cost-effective and most importantly can easily be extended to load the Pt (II) onto other supports, opening new possibilities for enhanced delivery of Pt (II) therapy.

Modulation of antitumor immunity contributes to the enhanced therapeutic efficacy of liposomal oxaliplatin in mouse model

Immune modulation of the tumor microenvironment has been reported to participate in the therapeutic efficacy of many chemotherapeutic agents. Recently, we reported that liposomal encapsulation of oxaliplatin (l-OHP) within PEGylated liposomes conferred a superior antitumor efficacy to free l-OHP in murine colorectal carcinoma-bearing mice through permitting preferential accumulation of the encapsulated drug within tumor tissue. However, the contribution of the immune-modulatory properties of liposomal l-OHP and/or free l-OHP to the overall antitumor efficacy was not elucidated. In the present study, therefore, we investigated the effect of liposomal encapsulation of l-OHP within PEGylated liposomes on the antitumor immunity in both immunocompetent and immunodeficient mice. Liposomal l-OHP significantly suppressed the growth of tumors implanted in immunocompetent mice, but not in immunodeficient mice. In immunocompetent mice, liposomal l-OHP increased the tumor MHC-1 level and preserved antitumor immunity through decreasing the number of immune suppressor cells, including regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages, which collectively suppress CD8⁺ T cell-mediated tumor cells killing. In contrast, free l-OHP ruined antitumor immunity. These results suggest that the antitumor efficacy of liposomal l-OHP is attributed, on the one hand, to its immunomodulatory effect on tumor immune microenvironment that is superior to that of free l-OHP, and on the other hand, to its direct cytotoxic effect on tumor cells.

Liposomal Delivery Systems: Design Optimization and Current Applications

The liposome, a closed phospholipid bilayered vesicular system, has received considerable attention as a pharmaceutical carrier of great potential over the past 30 years. The ability of liposomes to encapsulate both hydrophilic and hydrophobic drugs, coupled with their biocompatibility and biodegradability, make liposomes attractive vehicles in the field of drug delivery. In addition, great technical advances such as remote drug loading, triggered release liposomes, ligand-targeted liposomes, liposomes containing combinations of drugs, and so on, have led to the widespread use of liposomes in diverse areas as delivery vehicles for anti-cancer, bio-active molecules, diagnostics, and therapeutic agents. In this review, we summarize design optimization of liposomal systems and invaluable applications of liposomes as effective delivery systems.

Metronomic chemotherapy and nanocarrier platforms

The therapeutic concept of administering chemotherapeutic agents continuously at lower doses, relative to the maximum tolerated dose (MTD) without drug-free breaks over extended periods -known as "metronomic chemotherapy"- is a promising approach for anti-angiogenic cancer therapy. In comparison with MTD chemotherapy regimens, metronomic chemotherapy has demonstrated reduced toxicity. However, as a monotherapy, metronomic chemotherapy has failed to provide convincing results in clinical trials. Therapeutic approaches including combining the anti-angiogenic "metronomic" therapy with conventional radio-/chemo-therapy and/or targeted delivery of chemotherapeutic agents to tumor tissues via their encapsulation with nanocarrier-based platforms have proven to potentiate the overall therapeutic outcomes. In this review, therefore, we focused on the mutual contribution made by nanoscale drug delivery platforms to the therapeutic efficacy of metronomic-based chemotherapy. In addition, the influence that the dosing schedule has on the overall therapeutic efficacy of metronomic chemotherapy is discussed.

Preparation and Evaluation of Oxaliplatin Thermosensitive Liposomes with Rapid Release and High Stability

Oxaliplatin (OXP) was reported to show low anti-tumor activity when used alone and to display side effects; this low activity was attributed to high partitioning to erythrocytes and low accumulation in tumors. Thermosensitive liposomes (TSL) were considered able to specifically deliver drugs to heated tumors and to resolve the OXP distribution problem. Regretfully, TSL encapsulating doxorubicin did not demonstrate significant improvement in progression-free survival. Drug release below 41°C and significant leakage were considered major reasons for the failure. The purpose of this study was to acquire OXP TSL with rapid release at the triggered temperature and high stability at body temperature and at storage temperatures. A small quantity of poloxamer 188 was introduced into the TSL formulation to stabilize the encapsulated drug. It was shown that the addition of poloxamer 188 had no influence on the TSL characteristics. More than 90% of OXP was released within 10 min at 42°C, and less than 15% was released within 60 min at temperatures below 39°C. TSL were stable at 37°C for 96 h and at 4°C for 6 months. The anti-tumor activity of TSL at the dose of 2.5 mg/kg was certified to be equal to those of OXP injection and non-thermosensitive liposomes (NTSL) at the dose of 5 mg/kg, and significant improvement of tumor inhibition was observed in TSL compared with injection and NTSL at the same dose. It was also shown from the histological transmutation of tumors that TSL had stronger anti-tumor activity. Therefore, it could be concluded that TSL composed of a proper amount of poloxamer had rapid release and high stability, and OXP TSL would be anticipated to exert prominent anti-tumor activity in the clinic.

A novel glycyrrhetinic acid-modified oxaliplatin liposome for liver-targeting and in vitro/vivo evaluation

In this study, oxaliplatin (OX) liposomes surface-modified with glycyrrhetinic acid (GA) were developed by the film-dispersion method. Their morphology, physical and chemical properties, and in vitro release performance were investigated. The transmission electron microscope (TEM) image showed that most liposomes were spherical particles with similar size and uniform dispersion. Both OX-liposomes and GA-OX-liposomes had an average size of 90 nm. They were negatively charged, with zeta potentials of −20.6 and −21.3 mV, respectively, and the entrapment efficiency values of both were higher than 94%. In vitro data showed that the application of liposomes could prolong the OX release. The relatively high correlation coefficient values obtained from analyzing the amount of drug released versus the square root of time depicted that release followed the Weibull model. No significant changes were observed after the addition of GA to the liposomes. In vivo, the relatively long time to reach the maximum plasma concentration of OX-liposomes suggested a sustained-release profile of liposomes, which was consistent with the results of the in vitro release study. The increased area under the curve and maximum plasma concentration of OX-liposomes and GA-OX-liposomes demonstrated an increased absorption. The drug concentration in tissues indicated that the GA-modified liposomes delivered OX mainly to liver after intravenous administration. In addition, no severe signs, such as appearance of epithelial necrosis or sloughing of epithelial cells, were detected in histology studies.

Selective delivery of oxaliplatin to tumor tissue by nanocarrier system enhances overall therapeutic efficacy of the encapsulated oxaliplatin

Oxaliplatin (trans-l-diaminocyclohexane oxalatoplatinum; l-OHP), a third-generation platinum antitumor drug, is currently approved in combination with 5-flurouracil (5-FU)/leucovorin (FOLFOX) for standard first- and second-line treatment of metastatic or advanced-stage colorectal cancer. Despite l-OHP's better tolerability in comparison with other platinum compounds such as cisplatin and carboplatin, its clinical efficiency is limited by the dose-limiting side effects including cumulative neurotoxicity and acute dysesthesias. In addition, like other platinum chemotherapeutic agents, l-OHP therapy is limited by reduced accumulation levels in tumor tissues, nonselective accumulation in healthy organs and/or tissues, inactivation by conjugation with glutathione, and the development of drug resistance. Accordingly, successful outcome of cancer treatment using l-OHP requires selective delivery of a relatively high concentration of the drug to tumor tissues. In this review we focus on utilization of different drug-delivery vehicles such as liposomes, polymeric nanocarriers, and carbon nanotubes in enhancing selective delivery of l-OHP to tumor tissues and consequently improving overall efficacy of l-OHP-containing drug-delivery systems.

Nanomaterial-induced autophagy: a new reversal MDR tool in cancer therapy?

Most of the therapeutic strategies to counteract cancer imply killing of malignant cells. The most exploited cell death mechanism in cancer therapies is apoptosis, but recently, a lot of papers report that other mechanisms, mainly autophagy, could represent a new line of attack in the fight against cancer. One of the limitations for the effectiveness of the approved clinical treatments is the phenomenon of multidrug resistance (MDR) which enables the cancer cells to develop resistance to therapy, especially for chemotherapy. The MDR mechanisms include (a) decreased uptake of drug, (b) reduced intracellular drug concentration by efflux pumps, (c) altered cell cycle checkpoints, (d) altered drug targets, (e) increased metabolism of drugs, (f) induced emergency response genes to impair apoptotic pathway, and (g) altered drug detoxification. Great efforts have been made to reverse MDR. Currently, autophagy and nanosized drug delivery systems (DDSs) belonging to nanomaterials (NMs) provide alternative strategies to circumvent MDR. Nanosized DDSs are very promising tools to accumulate chemotherapeutics at targeting sites and control temporal and spatial drug release into tumor cells. On the other hand, autophagy could overrule drug resistance upon its activation by ensuring cell death via switching its prosurvival role to a prodeath one or by mediating the occurrence of cell death, i.e., apoptosis or necrosis. Likewise, the autophagy inhibition could counteract MDR by sensitizing the cells to anticancer molecules, i.e., Src family tyrosine kinase (SFK) inhibitors or 5-fluorouracil. Noteworthy, autophagy has been recently indicated to be a common cellular response to NMs, corroborating the fascinating idea of the exploitation of NM-induced autophagy in nanomedicine therapy. This review focuses on recently published literature about the relationship between MDR reversal and NMs or autophagy pointing to hypothesize a pivotal role of autophagy modulation induced by NMs in counteracting MDR.

Sequential treatment of oxaliplatin-containing PEGylated liposome together with S-1 improves intratumor distribution of subsequent doses of oxaliplatin-containing PEGylated liposome

We recently reported that combination therapy with metronomic S-1 dosing and oxaliplatin (l-OHP)-containing PEGylated liposomes improved antitumor activity in a murine colorectal tumor model. However, little is known about the mechanism underlying such improved therapeutic efficacy. Here we investigated the impact of combined treatment on biodistribution, tumor accumulation and intratumor distribution of test PEGylated liposomes and on the structure of tumor vasculature in a solid tumor. The combined treatment clearly enhanced tumor accumulation and intratumor distribution of a subsequent test dose of PEGylated liposome as a result of on the one hand prolonging blood circulation of test liposome and on the other hand the alteration in tumor microenvironment. The l-OHP-containing PEGylated liposomes contributed predominantly to the enhanced tumor accumulation and altered tumor distribution of test liposome. On the other hand, metronomic S-1 dosing contributed to the altered tumor distribution but not the tumor accumulation of test liposome. The antitumor effect of the combined treatment, reflected by the proportion of apoptotic cells in the tumor, was approximately equally accounted for by each of the two treatments, leading to a roughly additive effect. In conclusion, 1-OHP-containing PEGylated liposome together with S-1 enhanced intratumor influx, leading to improved antitumor activity of subsequently injected 1-OHP-containing PEGylated liposomes and/or S-1. This strategy we propose, which is clinically applicable, may overcome the problems related to the use of EPR effect-based nanocarrier systems.

Abrogation of the accelerated blood clearance phenomenon by SOXL regimen: promise for clinical application

We recently proposed an S-1 combined with oxaliplatin (SOXL) regimen, a combination treatment consisting of oral metronomic S-1 dosing and intravenous administration of oxaliplatin (l-OHP) containing PEGylated liposomes, which showed potent antitumor activity in vivo. PEGylated liposomes induce what is referred to as the "accelerated blood clearance (ABC) phenomenon" upon repeated administration and consequently lose their long-circulating characteristics. This phenomenon seems to pose an impediment for the clinical application and use of PEGylated liposomal formulations. In the present study, l-OHP-containing PEGylated liposomes in the SOXL regimen significantly attenuated the ABC phenomenon in a dose-dependent manner through suppression of the anti-PEG IgM response, which allowed an enhanced hepatic uptake of subsequently injected test PEGylated liposomes. In tumor-bearing mice, the abrogation of the ABC phenomenon restored intratumor accumulation of subsequently injected PEGylated liposomes. Consequently, the therapeutic efficacy of the SOXL regimen over the combination of the free form of the drugs was credited not only with the selective delivery of drugs to the tumor tissue but also with ensuring an adequate accumulation of subsequent doses within the tumor tissue. The SOXL regimen we proposed may hold promise as a safe and effective treatment regimen for advanced colorectal cancer.

PEG-liposomal oxaliplatin induces apoptosis in human colorectal cancer cells via Fas/FasL and caspase-8

Since cellular uptake of PEG [poly(ethylene glycol)]-liposomal L-OHP (oxaliplatin) induces bioactive changes in CRC (colorectal cancer), we have investigated its apoptotic effect and anticancer mechanism. Human CRC SW480 cells were treated with PEG-liposomal L-OHP and a caspase-8 inhibitor [Z-IETD-FMK (benzyloxycarbonyl-Ile-Glu-Thr-dl-Asp-fluoromethylketone)]. Apoptosis was measured by FCM (flow cytometry) and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay. Expression of Fas/FasL and cytochrome c was detected using FCM and an immunofluorescence assay. Expression of caspase-8, Bid, caspase-9, caspase-7 and activated caspase-3 (P17) was examined by Western blot analyses. The results indicated that PEG-liposomal L-OHP (28 μg/ml L-OHP) induced marked apoptosis in SW480 cells compared with 28 μg/ml free L-OHP. The expression levels of Fas, FasL, cytochrome c, caspase-9, caspase-7 and activated caspase-3 proteins were up-regulated, with a corresponding increase in apoptosis; however, expression of caspase-8 and Bid were down-regulated as apoptosis increased. When cells were treated with Z-IETD-FMK, apoptosis was inhibited, but there was little impact on the expression of Fas, FasL, cytochrome c, Bid, caspase-9, caspase-7 and activated caspase-3. These findings indicate that PEG-liposomal L-OHP enhances the anticancer potency of the chemotherapeutic agent; moreover, Fas/FasL and caspase-8 signalling pathways play a key role in mediating PEG-liposomal L-OHP-induced apoptosis.

Hepatocellular carcinoma targeting effect of PEGylated liposomes modified with lactoferrin

A hepatocellular carcinoma targeting lactoferrin (Lf) modified PEGylated liposome system was developed for improving drug efficacies to hepatic cancer cells. In this present work, PEGylated liposomes (PLS) were successfully prepared by the thin film hydration method combined with peglipid post insertion. Lf was covalently conjugated to the distal end of DSPE-PEG2000-COOH lipid by amide bound and loaded onto PEGylated liposomes surface as the targeting ligand. To confirm the targeting efficacies to hepatic cancer, coumarin-6 and DiR were encapsulated as fluorescent probes. The confocal microscopy and flow cytometry demonstrated that Lf conjugated PEGylated liposomes (Lf-PLS) were efficiently associated by HepG2 cells, while limited interaction was found for liposomes modified with a negative control protein. A similar pharmacokinetic behavior was observed in pharmacokinetics study of the liposomal formulations. Meanwhile, the in vivo imaging of liposomes in HepG2 tumor bearing mice indicated that Lf-PLS achieved more accumulation in tumor compared with PLS without Lf conjugated. The significant in vitro and in vivo results suggested that Lf-PLS might be a promising drug delivery system for hepatocellular carcinoma therapy with low toxicity.

Combination therapy with metronomic S-1 dosing and oxaliplatin-containing PEG-coated cationic liposomes in a murine colorectal tumor model: synergy or antagonism?

Combination therapy with 2 or more drugs with different mechanisms of action has been considered a promising strategy for the effective treatment of advanced and metastatic cancers. However, the rational design of combination therapy represents a potential prerequisite for its effectiveness. Recently, we showed that the combination of oral metronomic S-1 dosing with oxaliplatin (l-OHP)-containing PEG-coated "neutral" liposomes exerted excellent antitumor activity. In addition, we recently designed a PEG-coated "cationic" liposome for dual-targeting delivery of l-OHP to tumor endothelial cells and tumor cells in a solid tumor. This targeted liposomal l-OHP formulation showed efficient antitumor activity in a murine tumor model, compared with l-OHP-containing PEG-coated "neutral" liposomes. In the present study, we investigated the issue of whether metronomic S-1 dosing with l-OHP-containing PEG-coated "cationic" liposomes creates synergy. Unfortunately, metronomic S-1 dosing resulted in impaired delivery of PEG-coated "cationic" liposomes into tumor tissue, presumably by decreasing the binding sites on tumor blood vessels available for the liposomes. The anticipated cytotoxic synergistic effect of the combination treatment was not achieved. Instead, the combination treatment showed lower antitumor efficacy than l-OHP-containing PEG-coated "cationic" liposomes alone. These results suggest that the combined treatment of S-1 and l-OHP-containing PEG-coated "cationic" liposomes seems to be antagonistic rather than synergistic.

Oxaliplatin long-circulating liposomes improved therapeutic index of colorectal carcinoma

Background

Cytotoxic drugs are non-selective between normal and pathological tissue, and this poses a challenge regarding the strategy for treatment of tumors. To achieve sufficient antitumor activity for colorectal carcinoma, optimization of the therapeutic regimen is of great importance. We investigated the ability of oxaliplatin long-circulating liposomes (PEG-liposomal L-oHP) to provide an improved therapeutic index of colorectal carcinoma.

Results

We determined that PEG- liposomes conjugated with cells at 2 h, with a mean fluorescence intensity that was enhanced upon extended induction time. The PEG-liposomal L-oHP induced a significant apoptotic response as compared with free L-oHP, 23.21% ± 3.38% vs. 16.85% ± 0.98%, respectively. Fluorescence imaging with In-Vivo Imaging demonstrated that PEG- liposomes specifically targeted tumour tissue. After intravenous injections of PEG-liposomal L-oHP or free L-oHP, the tumour volume suppression ratio was 26.08% ± 12.43% and 18.19% ± 7.09%, respectively, the percentage increased life span (ILS%) was 45.36% and 76.19%, respectively, and Bcl-2, Bax mRNA and protein expression in tumour tissue was 0.27-fold vs. 0.88-fold and 1.32-fold vs. 1.61-fold compared with free L-oHP, respectively.

Conclusion

The PEG-liposomal L-oHP exhibited a tendency to target tumour tissue and demonstrated a significantly greater impact on apoptosis compared to free oxaliplatin.

Drug delivery strategies for therapeutic angiogenesis and antiangiogenesis

INTRODUCTION

Angiogenesis is essential to human biology and of great clinical significance. Excessive or reduced angiogenesis can result in, or exacerbate, several disease states, including tumor formation, exudative age-related macular degeneration (AMD) and ischemia. Innovative drug delivery systems can increase the effectiveness of therapies used to treat angiogenesis-related diseases.

AREAS COVERED

This paper reviews the basic biology of angiogenesis, including current knowledge about its disruption in diseases, with the focus on cancer and AMD. Anti- and proangiogenic drugs available for clinical use or in development are also discussed, as well as experimental drug delivery systems that can potentially improve these therapies to enhance or reduce angiogenesis in a more controlled manner.

EXPERT OPINION

Laboratory and clinical results have shown pro- or antiangiogenic drug delivery strategies to be effective in drastically slowing disease progression. Further research in this area will increase the efficacy, specificity and duration of these therapies. Future directions with composite drug delivery systems may make possible targeting of multiple factors for synergistic effects.

Combination therapy of metronomic S-1 dosing with oxaliplatin-containing polyethylene glycol-coated liposome improves antitumor activity in a murine colorectal tumor model

Metronomic chemotherapy has been advocated recently as a novel chemotherapeutic regimen. Polyethylene glycol (PEG)-coated liposomes are well known to accumulate in solid tumors by virtue of the highly permeable angiogenic blood vessels characteristic for growing tumor tissue, the so-called "enhanced permeability and retention (EPR) effect". To expand the range of applications and investigate the clinical value of the combination strategy, the therapeutic benefit of metronomic S-1 dosing in combination with oxaliplatin (l-OHP)-containing PEG-coated liposomes was evaluated in a murine colon carcinoma-bearing mice model. S-1 is an oral fluoropyrimidine formulation and metronomic S-1 dosing is a promising alternative to infused 5-FU in colorectal cancer therapy. Therefore, the combination of S-1 with l-OHP may be an alternative to FOLFOX (infusional 5-FU/leucovorin (LV) in combination with l-OHP), which is a first-line therapeutic regimen of a colorectal carcinoma. The combination of oral metronomic S-1 dosing with intravenous administration of liposomal l-OHP formulation exerted excellent antitumor activity without severe overlapping side-effects, compared with either metronomic S-1 dosing, free l-OHP or liposomal l-OHP formulation alone or metronomic S-1 dosing plus free l-OHP. We confirmed that the synergistic antitumor effect is due to prolonged retention of l-OHP in the tumor on account of the PEG-coated liposomes, presumably via alteration of the tumor microenvironment caused by the metronomic S-1 treatment. The combination regimen proposed here may be a breakthrough in treatment of intractable solid tumors and an alternative to FOLFOX in advanced colorectal cancer therapy with acceptable tolerance and preservation of quality of life (QOL).

Targeting anticancer drugs to tumor vasculature using cationic liposomes

Liposomal drug delivery systems improve the therapeutic index of chemotherapeutic agents, and the use of cationic liposomes to deliver anticancer drugs to solid tumors has recently been recognized as a promising therapeutic strategy to improve the effectiveness of conventional chemotherapeutics. This review summarizes the selective targeting of cationic liposomes to tumor vasculature, the merits of incorporating the polymer polyethylene-glycol (PEG), and the impact of the molar percent of the cationic lipid included in cationic liposomes on liposomal targeting efficacy. In addition, the discussion herein includes the therapeutic benefit of a dual targeting approach, using PEG-coated cationic liposomes in vascular targeting (of tumor endothelial cells), and tumor targeting (of tumor cells) of anticancer drugs. Cationic liposomes have shown considerable promise in preclinical xenograft models and are poised for clinical development.

Recent advances in tumor vasculature targeting using liposomal drug delivery systems

Tumor vessels possess unique physiological features that might be exploited for improved drug delivery. The targeting of liposomal anticancer drugs to tumor vasculature is increasingly recognized as an effective strategy to obtain superior therapeutic efficacy with limited host toxicity compared with conventional treatments. This review introduces recent advances in the field of liposomal targeting of tumor vasculature, along with new approaches that can be used in the design and optimization of liposomal delivery systems. In addition, cationic liposome is focused on as a promising carrier for achieving efficient vascular targeting. The clinical implications are discussed of several approaches using a single liposomal anticancer drug formulation: dual targeting, vascular targeting (targeting tumor endothelial cells) and tumor targeting (targeting tumor cells).

An optical and microPET assessment of thermally-sensitive liposome biodistribution in the Met-1 tumor model: Importance of formulation

The design of delivery vehicles that are stable in circulation but can be activated by exogenous energy sources is challenging. Our goals are to validate new imaging methods for the assessment of particle stability, to engineer stable and activatable particles and to assess accumulation of a hydrophilic model drug in an orthotopic tumor. Here, liposomes were injected into the tail vein of FVB mice containing bilateral Met-1 tumors and imaged in vivo using microPET and optical imaging techniques. Cryo-electron microscopy was applied to assess particle shape prior to injection, ex vivo fluorescence images of dissected tissues were acquired, excised tissue was further processed with a cell-digest preparation and assayed for fluorescence. We find that for a stable particle, in vivo tumor images of a hydrophilic model drug were highly correlated with PET images of the particle shell and ex vivo fluorescence images of processed tissue, R(2)=0.95 and R(2)=0.99 respectively. We demonstrate that the accumulation of a hydrophilic model drug is increased by up to 177 fold by liposomal encapsulation, as compared to accumulation of the drug at 24 hours.

Sequential administration with oxaliplatin-containing PEG-coated cationic liposomes promotes a significant delivery of subsequent dose into murine solid tumor

Recently, we designed a PEG-coated cationic liposome to achieve dual targeting delivery of l-OHP to both tumor endothelial cells and tumor cells in a solid tumor. The targeted liposomal l-OHP formulation showed an efficient antitumor activity in a murine tumor model after three sequential liposomal l-OHP injections. This led us to assume that prior dosing with liposomes might enhance the intra-tumoral accumulation of a subsequent dose, and hence improve the therapeutic efficacy of entrapped l-OHP. The present study shows that while a single liposomal l-OHP injection does not enhance tumor accumulation of subsequent test-PEG-coated cationic liposomes, two sequential injections of liposomal l-OHP do. Cumulative cytotoxic effects of l-OHP delivered by PEG-coated cationic liposomes led to deep diffusion of a subsequent dose of liposomal l-OHP in solid tumor presumably as a result of the enlarged intra-tumoral interstitial space. Our study suggests that sequential injections of a targeted liposomal anticancer drug is of significant clinical and practical importance in enhancing the delivery of adequate quantities of anticancer agents into intractable solid tumors, and thereby may achieve a significant anticancer efficacy.