Simultaneous active intracellular delivery of doxorubicin and C6-ceramide shifts the additive/antagonistic drug interaction of non-encapsulated combination

Nucleolin‑based targeting strategies in cancer treatment: Focus on cancer immunotherapy (Review)

The benefits of treating several types of cancers using immunotherapy have recently been established. The overexpression of nucleolin (NCL) in a number of types of cancer provides an attractive antigen target for the development of novel anticancer immunotherapeutic treatments. NCL is a multifunctional protein abundantly distributed in the nucleus, cytoplasm and cell membrane. It influences carcinogenesis, and the proliferation, survival and metastasis of cancer cells, leading to cancer progression. Additionally, the meta‑analysis of total and cytoplasmic NCL overexpression indicates a poor prognosis of patients with breast cancer. The AS1411 aptamers currently appear to have therapeutic action in the phase II clinical trial. The authors' research group has recently explored the anticancer function of NCL through the activation of T cells by dendritic cell‑based immunotherapy. The present review describes and discusses the mechanisms through which the multiple functions of NCL can participate in the progression of cancer. In addition, the studies that define the utility of NCL‑dependent anticancer therapies are summarized, with specific focus being paid to cancer immunotherapeutic approaches.

Quantum Dot-Based Screening Identifies F3 Peptide and Reveals Cell Surface Nucleolin as a Therapeutic Target for Rhabdomyosarcoma

Active drug delivery by tumor-targeting peptides is a promising approach to improve existing therapies for rhabdomyosarcoma (RMS), by increasing the therapeutic effect and decreasing the systemic toxicity, e.g., by drug-loaded peptide-targeted nanoparticles. Here, we tested 20 different tumor-targeting peptides for their ability to bind to two RMS cell lines, Rh30 and RD, using quantum dots Streptavidin and biotin-peptides conjugates as a model for nanoparticles. Four peptides revealed a very strong binding to RMS cells: NCAM-1-targeting NTP peptide, nucleolin-targeting F3 peptide, and two Furin-targeting peptides, TmR and shTmR. F3 peptide showed the strongest binding to all RMS cell lines tested, low binding to normal control myoblasts and fibroblasts, and efficient internalization into RMS cells demonstrated by the cytoplasmic delivery of the Saporin toxin. The expression of the nucleophosphoprotein nucleolin, the target of F3, on the surface of RMS cell lines was validated by competition with the natural ligand lactoferrin, by colocalization with the nucleolin-binding aptamer AS1411, and by the marked sensitivity of RMS cell lines to the growth inhibitory nucleolin-binding N6L pseudopeptide. Taken together, our results indicate that nucleolin-targeting by F3 peptide represents a potential therapeutic approach for RMS.

Nucleolin Overexpression Predicts Patient Prognosis While Providing a Framework for Targeted Therapeutic Intervention in Lung Cancer

Simple Summary

Despite the clinical benefit of new anticancer therapies, such as immune checkpoint inhibitors, lung cancer remains the most frequent cause of cancer-related death worldwide, thus supporting the need to develop novel anticancer treatments. Endothelial cells of the tumor-associated vasculature are easily accessible to drugs administered intravenously, besides having greater genetic stability than neoplastic cells and thus lowering the risk of developing drug resistance. In this respect, the identification of alternative targets, and therapeutic strategies, within the tumor vasculature is of high relevance. Accordingly, this work aimed at characterizing nucleolin expression in patient-derived pulmonary carcinomas and further validating nucleolin as a novel target to mediate successful therapeutic interventions against human lung cancers. The highlighted prognostic value of nucleolin points towards the applicability of nucleolin-based targeting strategies against nucleolin^high pulmonary carcinomas, present in every disease stage, in a clinical trial setting.

Abstract

Notwithstanding the advances in the treatment of lung cancer with immune checkpoint inhibitors, the high percentage of non-responders supports the development of novel anticancer treatments. Herein, the expression of the onco-target nucleolin in patient-derived pulmonary carcinomas was characterized, along with the assessment of its potential as a therapeutic target. The clinical prognostic value of nucleolin for human pulmonary carcinomas was evaluated through data mining from the Cancer Genome Atlas project and immunohistochemical detection in human samples. Cell surface expression of nucleolin was evaluated by flow cytometry and subcellular fraction Western blotting in lung cancer cell lines. Nucleolin mRNA overexpression correlated with poor overall survival of lung adenocarcinoma cancer patients and further predicted the disease progression of both lung adenocarcinoma and squamous carcinoma. Furthermore, a third of the cases presented extra-nuclear expression, contrasting with the nucleolar pattern in non-malignant tissues. A two- to twelve-fold improvement in cytotoxicity, subsequent to internalization into the lung cancer cell lines of doxorubicin-loaded liposomes functionalized by the nucleolin-binding F3 peptide, was correlated with the nucleolin cell surface levels and the corresponding extent of cell binding. Overall, the results suggested nucleolin overexpression as a poor prognosis predictor and thus a target for therapeutic intervention in lung cancer.

Modelling the impact of nucleolin expression level on the activity of F3 peptide-targeted pH-sensitive pegylated liposomes containing doxorubicin

Strategies targeting nucleolin have enabled a significant improvement in intracellular bioavailability of their encapsulated payloads. In this respect, assessment of the impact of target cell heterogeneity and nucleolin homology across species (structurally and functionally) is of major importance. This work also aimed at mathematically modelling the nucleolin expression levels at the cell membrane, binding and internalization of pH-sensitive pegylated liposomes encapsulating doxorubicin and functionalized with the nucleolin-binding F3 peptide (PEGASEMP), and resulting cytotoxicity against cancer cells from mouse, rat, canine, and human origin. Herein, it was shown that nucleolin expression levels were not a limitation on the continuous internalization of F3 peptide-targeted liposomes, despite the saturable nature of the binding mechanism. Modeling enabled the prediction of nucleolin-mediated total doxorubicin exposure provided by the experimental settings of the assessment of PEGASEMP's impact on cell death. The former increased proportionally with nucleolin-binding sites, a measure relevant for patient stratification. This pattern of variation was observed for the resulting cell death in nonsaturating conditions, depending on the cancer cell sensitivity to doxorubicin. This approach differs from standard determination of cytotoxic concentrations, which normally report values of incubation doses rather than the actual intracellular bioactive drug exposure. Importantly, in the context of development of nucleolin-based targeted drug delivery, the structural nucleolin homology (higher than 84%) and functional similarity across species presented herein, emphasized the potential to use toxicological data and other metrics from lower species to infer the dose for a first-in-human trial.

Targeted liposomal doxorubicin/ceramides combinations: the importance to assess the nature of drug interaction beyond bulk tumor cells

One of the major assets of anticancer nanomedicine is the ability to co-deliver drug combinations, as it enables targeting of different cellular populations and/or signaling pathways implicated in tumorigenesis and thus tackling tumor heterogeneity. Moreover, drug resistance can be circumvented, for example, upon co-encapsulation and delivery of doxorubicin and sphingolipids, as ceramides. Herein, the impact of short (C6) and long (C18) alkyl chain length ceramides on the nature of drug interaction, within the scope of combination with doxorubicin, was performed in bulk triple-negative breast cancer (TNBC) cells, as well as on the density of putative cancer stem cells and phenotype, including live single-cell tracking. C6- or C18-ceramide enabled a synergistic drug interaction in all conditions and (bulk) cell lines tested. However, differentiation among these two ceramides was reflected on the migratory potential of cancer cells, particularly significant against the highly motile MDA-MB-231 cells. This effect was supported by the downregulation of the PI3K/Akt pathway enabled by C6-ceramide and in contrast with C18-ceramide. The decrease of the migratory potential enabled by the targeted liposomal combinations is of high relevance in the context of TNBC, due to the underlying metastatic potential. Surprisingly, the nature of the drug interaction assessed at the level of bulk cancer cells revealed to be insufficient to predict whether a drug combination enables a decrease in the percentage of the master regulators of tumor relapse as ALDH^+/high putative TNBC cancer stem cells, suggesting, for the first time, that it should be extended further down to this level.

The Enhanced Efficacy of Intracellular Delivery of Doxorubicin/C6-Ceramide Combination Mediated by the F3 Peptide/Nucleolin System Is Supported by the Downregulation of the PI3K/Akt Pathway

Simple Summary

Targeted nanomedicine-based approaches that aim at the simultaneous delivery of synergistic drug combinations to multiple cellular populations are of high relevance for tackling heterogeneity on solid tumors. Considering that cancer stem cells (CSC) may originate from non-stem cancer cells, single-drug regimens targeting only one of these cell populations could enable tumors to evade treatments. As such, the identification of a common marker, such as nucleolin, might result in a therapeutic advantage. The results herein generated suggested a transversal role of nucleolin in the internalization of F3 peptide-targeted pegylated pH-sensitive liposomes into bulk ovarian cancer cells, including putative CSC-enriched ovarian cells. The intracellular delivery of a drug combination such as the one tested herein was relevant in the context of cell lines with higher intrinsic resistances to doxorubicin. The enhanced efficacy of the F3 peptide-targeted liposomal combination of doxorubicin/C6-ceramide was supported by the downregulation of the Akt pathway, within a specific range of basal level of expression.

Abstract

Targeting multiple cellular populations is of high therapeutic relevance for the tackling of solid tumors heterogeneity. Herein, the ability of pegylated and pH-sensitive liposomes, functionalized with the nucleolin-binding F3 peptide and containing doxorubicin (DXR)/C6-ceramide synergistic combination, to target, in vitro, ovarian cancer, including ovarian cancer stem cells (CSC), was assessed. The underlying molecular mechanism of action of the nucleolin-mediated intracellular delivery of C6-ceramide to cancer cells was also explored. The assessment of overexpression of surface nucleolin expression by flow cytometry was critical to dissipate differences identified by Western blot in membrane/cytoplasm of SKOV-3, OVCAR-3 and TOV-112D ovarian cancer cell lines. The former was in line with the significant extent of uptake into (bulk) ovarian cancer cells, relative to non-targeted and non-specific counterparts. This pattern of uptake was recapitulated with putative CSC-enriched ovarian SKOV-3 and OVCAR-3 sub-population (EpCAM^high/CD44^high). Co-encapsulation of DXR:C6-ceramide into F3 peptide-targeted liposomes improved cytotoxic activity relative to liposomes containing DXR alone, in an extent that depended on the intrinsic resistance to DXR and on the incubation time. The enhanced cytotoxicity of the targeted combination was mechanistically supported by the downregulation of PI3K/Akt pathway by C6-ceramide, only among the nucleolin-overexpressing cancer cells presenting a basal p-Akt/total Akt ratio lower than 1.

A Novel Combinational Nanodrug Delivery System Induces Synergistic Inhibition of Lung Adenocarcinoma Cells In vitro

Background:

The combination of two or more therapeutic drugs is an attractive approach to improve the treatment of experimental tumors. Leveraging nanocarriers for combinational drug delivery can allow control over drug biological fate and promote co-localization in the same area of the body. However, there are certain concerns regarding the biodegradability and potential longterm toxicity arising from these synthetic nanoscale carriers.

Objective:

Our aim was to develop a combinational nanodrug delivery system formed by selfassembling of amphiphilic drug molecules.minimizing potential toxicities associated with using additional synthetic nanocarriers.

Methods:

A novel prodrug chlorambucil gemcitabine conjugate was synthesized, this prodrug was used for the encapsulation of an additional hydrophobic anticancer drug paclitaxel, taking the form of combinational nanodrugs. Particle size and zeta potential were evaluated, cytotoxicity assay and apoptosis/cell cycle analysis were also performed to validate the anticancer efficacy of the combinational nanodrugs.

Results:

The combinational nanodrugs were acquired by means of nanoprecipitation. In A549 lung adenocarcinoma cell line, cellular assays revealed that co-delivery of low dosage paclitaxel with chlorambucil gemcitabine conjugate can act synergistically to inhibit cell growth and induce accumulation of cells in the G2/M phase with a concomitant decrease in G0/G1 compartment.

Conclusion:

Chlorambucil gemcitabine conjugate and paclitaxel can co-assemble into composite nanoparticles by a nanoprecipitation process and the resulting combinational nanodrugs showed a synergistic anticancer effect. This synthetic nanocarrier-free approach might broaden the nanodrug concept and have potential in cancer therapy.

Cancer Stem Cells and Nucleolin as Drivers of Carcinogenesis

Cancer, one of the most mortal diseases worldwide, is characterized by the gain of specific features and cellular heterogeneity. Clonal evolution is an established theory to explain heterogeneity, but the discovery of cancer stem cells expanded the concept to include the hierarchical growth and plasticity of cancer cells. The activation of epithelial-to-mesenchymal transition and its molecular players are widely correlated with the presence of cancer stem cells in tumors. Moreover, the acquisition of certain oncological features may be partially attributed to alterations in the levels, location or function of nucleolin, a multifunctional protein involved in several cellular processes. This review aims at integrating the established hallmarks of cancer with the plasticity of cancer cells as an emerging hallmark; responsible for tumor heterogeneity; therapy resistance and relapse. The discussion will contextualize the involvement of nucleolin in the establishment of cancer hallmarks and its application as a marker protein for targeted anticancer therapies

In Vitro and In Vivo Tumor Models for the Evaluation of Anticancer Nanoparticles

Multiple studies about tumor biology have revealed the determinant role of the tumor microenvironment in cancer progression, resulting from the dynamic interactions between tumor cells and surrounding stromal cells within the extracellular matrix. This malignant microenvironment highly impacts the efficacy of anticancer nanoparticles by displaying drug resistance mechanisms, as well as intrinsic physical and biochemical barriers, which hamper their intratumoral accumulation and biological activity.Currently, two-dimensional cell cultures are used as the initial screening method in vitro for testing cytotoxic nanocarriers. However, this fails to mimic the tumor heterogeneity, as well as the three-dimensional tumor architecture and pathophysiological barriers, leading to an inaccurate pharmacological evaluation.Biomimetic 3D in vitro tumor models, on the other hand, are emerging as promising tools for more accurately assessing nanoparticle activity, owing to their ability to recapitulate certain features of the tumor microenvironment and thus provide mechanistic insights into nanocarrier intratumoral penetration and diffusion rates.Notwithstanding, in vivo validation of nanomedicines remains irreplaceable at the preclinical stage, and a vast variety of more advanced in vivo tumor models is currently available. Such complex animal models (e.g., genetically engineered mice and patient-derived xenografts) are capable of better predicting nanocarrier clinical efficiency, as they closely resemble the heterogeneity of the human tumor microenvironment.Herein, the development of physiologically more relevant in vitro and in vivo tumor models for the preclinical evaluation of anticancer nanoparticles will be discussed, as well as the current limitations and future challenges in clinical translation.

Mendonça L, Matos L, Prata MJ, S. Jurado A, Pedroso de Lima MC, Alves S. Lysosomal Storage Disease-Associated Neuropathy: Targeting Stable Nucleic Acid Lipid Particle (SNALP)-Formulated siRNAs to the Brain as a Therapeutic Approach

More than two thirds of Lysosomal Storage Diseases (LSDs) present central nervous system involvement. Nevertheless, only one of the currently approved therapies has an impact on neuropathology. Therefore, alternative approaches are under development, either addressing the underlying enzymatic defect or its downstream consequences. Also under study is the possibility to block substrate accumulation upstream, by promoting a decrease of its synthesis. This concept is known as substrate reduction therapy and may be triggered by several molecules, such as small interfering RNAs (siRNAs). siRNAs promote RNA interference, a naturally occurring sequence-specific post-transcriptional gene-silencing mechanism, and may target virtually any gene of interest, inhibiting its expression. Still, naked siRNAs have limited cellular uptake, low biological stability, and unfavorable pharmacokinetics. Thus, their translation into clinics requires proper delivery methods. One promising platform is a special class of liposomes called stable nucleic acid lipid particles (SNALPs), which are characterized by high cargo encapsulation efficiency and may be engineered to promote targeted delivery to specific receptors. Here, we review the concept of SNALPs, presenting a series of examples on their efficacy as siRNA nanodelivery systems. By doing so, we hope to unveil the therapeutic potential of these nanosystems for targeted brain delivery of siRNAs in LSDs.

Transcriptomic insight into salinomycin mechanisms in breast cancer cell lines: synergistic effects with dasatinib and induction of estrogen receptor β

BACKGROUND

Tumors are heterogeneous in nature, composed of different cell populations with various mutations and/or phenotypes. Using a single drug to encounter cancer progression is generally ineffective. To improve the treatment outcome, multiple drugs of distinctive mechanisms but complementary anticancer activities (combination therapy) are often used to enhance antitumor efficacy and minimize the risk of acquiring drug resistance. We report here the synergistic effects of salinomycin (a polyether antibiotic) and dasatinib (a Src kinase inhibitor).

METHODS

Functionally, both drugs induce cell cycle arrest, intracellular reactive oxygen species (iROS) production, and apoptosis. We rationalized that an overlapping of the drug activities should offer an enhanced anticancer effect, either through vertical inhibition of the Src-STAT3 axis or horizontal suppression of multiple pathways. We determined the toxicity induced by the drug combination and studied the kinetics of iROS production by fluorescence imaging and flow cytometry. Using genomic and proteomic techniques, including RNA-sequencing (RNA-seq), reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western Blot, we subsequently identified the responsible pathways that contributed to the synergistic effects of the drug combination.

RESULTS

Compared to either drug alone, the drug combination showed enhanced potency against MDA-MB-468, MDA-MB-231, and MCF-7 human breast cancer (BC) cell lines and tumor spheroids. The drug combination induces both iROS generation and apoptosis in a time-dependent manner, following a 2-step kinetic profile. RNA-seq data revealed that the drug combination exhibited synergism through horizontal suppression of multiple pathways, possibly through a promotion of cell cycle arrest at the G1/S phase via the estrogen-mediated S-phase entry pathway, and partially via the BRCA1 and DNA damage response pathway.

CONCLUSION

Transcriptomic analyses revealed for the first time, that the estrogen-mediated S-phase entry pathway partially contributed to the synergistic effect of the drug combination. More importantly, our studies led to the discoveries of new potential therapeutic targets, such as E2F2, as well as a novel drug-induced targeting of estrogen receptor β (ESR2) approach for triple-negative breast cancer treatment, currently lacking of targeted therapies.

Multifunctional, CD44v6-Targeted ORMOSIL Nanoparticles Enhance Drugs Toxicity in Cancer Cells

Drug-loaded, PEGylated, organic-modified silica (ORMOSIL) nanoparticles prepared by microemulsion condensation of vinyltriethoxysilane (VTES) were investigated as potential nanovectors for cancer therapy. To target cancer stem cells, anti-CD44v6 antibody and hyaluronic acid (HA) were conjugated to amine-functionalized PEGylated ORMOSIL nanoparticles through thiol-maleimide and amide coupling chemistries, respectively. Specific binding and uptake of conjugated nanoparticles were studied on cells overexpressing the CD44v6 receptor. Cytotoxicity was subsequently evaluated in the same cells after the uptake of the nanoparticles. Internalization of nanocarriers loaded with the anticancer drug 3N-cyclopropylmethyl-7-phenyl-pyrrolo- quinolinone (MG2477) into cells resulted in a substantial increase of the cytotoxicity with respect to the free formulation. Targeting with anti-CD44v6 antibodies or HA yielded nanoparticles with similar effectiveness, in their optimized formulation.

Surface engineering of nanomaterials with phospholipid-polyethylene glycol-derived functional conjugates for molecular imaging and targeted therapy

In recent years, phospholipid-polyethylene glycol-derived functional conjugates have been widely employed to decorate different nanomaterials, due to their excellent biocompatibility, long blood circulation characteristics, and specific targeting capability. Numerous in vivo studies have demonstrated that nanomedicines peripherally engineered with phospholipid-polyethylene glycol-derived functional conjugates show significantly increased selective and efficient internalization by target cells/tissues. Targeting moieties including small-molecule ligands, peptides, proteins, and antibodies are generally conjugated onto PEGylated phospholipids to decorate liposomes, micelles, hybrid nanoparticles, nanocomplexes, and nanoemulsions for targeted delivery of diagnostic and therapeutic agents to diseased sites. In this review, the synthesis methods of phospholipid-polyethylene glycol-derived functional conjugates, biophysicochemical properties of nanomedicines decorated with these conjugates, factors dominating their targeting efficiency, as well as their applications for in vivo molecular imaging and targeted therapy were summarized and discussed.

Nucleolin-based targeting strategies for cancer therapy: from targeted drug delivery to cytotoxic ligands

Cancer is currently the second leading cause of death worldwide and current therapeutic approaches remain ineffective in several cases. Therefore, there is a need to develop more efficacious therapeutic agents, especially for subtypes of cancer lacking targeted therapies. Limited drug penetration into tumors impairs the efficacy of therapies targeting cancer cells. One of the strategies to overcome this problem is targeting the more accessible tumor vasculature via molecules such as nucleolin, which is expressed at the surface of cancer and angiogenic endothelial cells, thus enabling a dual cellular targeting strategy. In this review, we present and discuss nucleolin-based targeting strategies that have been developed for cancer therapy, with a special focus on recent antibody-based approaches.

Co-delivery of Doxorubicin and Ceramide in a Liposomal Formulation Enhances Cytotoxicity in Murine B16BL6 Melanoma Cell Lines

This study reports co-delivery of doxorubicin (DOX) and ceramide in a liposomal system in B16BL6 melanoma cell lines for enhanced cytotoxic effects. Different types of ceramides (C6-ceramide, C8-ceramide, and C8-glucosylceramide) and lipids (1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)) were considered in the preparation of liposomes. DOX was encapsulated within liposome, and ceramide was used as the component of the lipid bilayer. The formulations were optimized for size and size distribution, zeta potential, and DOX encapsulation efficiency (EE). Cytotoxic effect on B16BL6 melanoma cell lines was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The ceramide based liposome formulations generally provided a mean diameter < 181 nm, a zeta potential, + 35 mV, and EE > 90% DOX EE. Co-delivery of DOX and C8-ceramide with DOTAP liposomes demonstrated significantly higher cytotoxicity as compared to DOX liposomes without ceramide (P < 0.001), and also showed enhanced cellular uptake by B16BL6 cell lines. This study provides basis for developing a co-delivery system of DOX and ceramide for lowering the dose and dose-related side effects of DOX for the treatment of melanoma.

Nucleolin is expressed in patient-derived samples and glioblastoma cells, enabling improved intracellular drug delivery and cytotoxicity

One of the major challenges in Glioblastoma (GBM) therapy relates with the existence of glioma stem-like cells (GSCs), known to be chemo- and radio-resistant. GSCs and non-stem GBM cells have the ability to interchange, emphasizing the importance of identifying common molecular targets among those cell sub-populations. Nucleolin overexpression has been recently associated with breast cancer sub-populations with different stem-like phenotype. The goal of this work was to evaluate the potential of cell surface nucleolin as a target in GBM cells. Different levels of nucleolin expression resulted in a 3.4-fold higher association of liposomes targeting nucleolin (functionalized with the nucleolin-binding F3 peptide) in U87, relative to GBM11 glioblastoma cells. Moreover, nucleolin was suggested as a potential marker in OCT4-, NANOG-positive GSC, and in the corresponding non-stem GBM cells, as well as in SOX2-positive GSC. Doxorubicin delivered by liposomes targeting nucleolin enabled a level of cytotoxicity that was 2.5- or 4.6-fold higher compared to the non-targeted counterparts. Importantly, an overexpression of nucleolin was also observed in cells of patient-derived samples, as compared with normal brain. Overall, these results suggested nucleolin as a therapeutic target in GBM.

Ceramide-Fabricated Co-Loaded Liposomes for the Synergistic Treatment of Hepatocellular Carcinoma

Combination therapy is one of the important methods to improve therapeutic effect on the treatment of hepatocellular carcinoma (HCC). Sorafenib (SF) is a canonical US Food and Drug Administration-approved multikinase molecule inhibitor against HCC. However, therapeutic benefit with Sorafenib alone was usually unsatisfactory. Ceramide (CE) is an endogenous bioactive sphingolipid, which has a strong potential to suppress various tumors. The combination of SF and CE was hoping to exert maximum synergistic antitumor effect through different tumor-suppressible mechanisms. In this respect, SF and CE co-loaded liposomes (SF/CE-liposomes) were developed to verify synergistic antitumor efficacy. The optimal molar ratio of SF and CE was determined through combination index. SF/CE-liposomes were prepared by thin-film hydration method, which exhibited spherical or ellipsoidal shape. Particle size of SF/CE-liposomes was 174 ± 4 nm with homogeneous distribution. Release profile of SF demonstrated that addition of CE imposed no significant impact on the release of SF. SF/CE-liposomes exhibited acceptable stability in different media and desirable storage stability over 30 days at 4°C. In vitro cellular uptake confirmed that SF/CE-liposomes could be efficiently internalized into HepG2 cells. In vitro cytotoxicity evaluation indicated that SF/CE-liposomes exhibited higher cytotoxicity on HepG2 cells. IC₅₀ value of SF/CE-liposomes was 11.5 ± 0.44 μM, which was significantly lower than that of SF-liposomes (^**p < 0.01). Evaluation of in vivo synergistic effect on H22-bearing mice verified that SF/CE-liposomes achieved robust antitumor activity in preventing tumor growth. All results suggested that SF/CE-liposomes might be served as an efficient co-delivery system for improving therapeutic efficacy of HCC.

Meeting the needs of breast cancer: A nucleolin's perspective

A major challenge in the management of breast cancer disease has been the development of metastases. Finding new molecular targets and the design of targeted therapeutic approaches to improve the overall survival and quality of life of these patients is, therefore, of great importance. Nucleolin, which is overexpressed in cancer cells and tumor-associated blood vessels, have been implicated in various processes supporting tumorigenesis and angiogenesis. Additionally, its overexpression has been demonstrated in a variety of human neoplasias as an unfavorable prognostic factor, associated with a high risk of relapse and low overall survival. Hence, nucleolin has emerged as a relevant target for therapeutic intervention in cancer malignancy, including breast cancer. This review focus on the contribution of nucleolin for cancer disease and on the development of therapeutic strategies targeting this protein. In this respect, it also provides a critical analysis about the potential and pitfalls of nanomedicine for cancer therapy.

Ceramide-containing liposomes with doxorubicin: time and cell-dependent effect of C6 and C12 ceramide

Doxorubicin, a widely used chemotherapeutic drug, has several potential high-risk side effects including cardiomyopathy. Furthermore, cellular resistance to this drug develops with time. By using liposomes as carrier vesicles both the side effects and drug resistance might be avoided. In this study we have investigated the cytotoxic effect of doxorubicin encapsulated in liposomes with and without ceramides containing 6 or 12 carbon atoms in the N-amidated fatty acyl chains. The short-chain ceramide species were included in the liposomal compositions due to their pro-apoptotic properties, which might cause a synergistic anticancer effect. We demonstrate that the ceramide species enhance the liposomal doxorubicin toxicity in a cell-specific manner. The C6-ceramide effect is most pronounced in cervical cancer cells (HeLa) and colon cancer cells (HCT116), whereas the C12-ceramide effect is strongest in breast cancer cells (MDA-MB-231). Moreover, the study reveals the importance of investigating cell toxicity at several time points and in different cell-lines, to assess drug-and formulation-induced cytotoxic effects in vitro. Furthermore, our data show that the cytotoxicity obtained with the nanocarriers in vitro, does not necessarily reflect their ability to inhibit tumor growth in vivo. We speculate that the larger effect of Caelyx® than our liposomes in vivo is due to a greater in vivo stability of Caelyx®.

The cancer stem cell phenotype as a determinant factor of the heterotypic nature of breast tumors

Gathering evidence supports the existence of a population of cells with stem-like characteristics, named cancer stem cells (CSC), which is involved not only in tumor recurrence but also in tumorigenicity, metastization and drug resistance. Several markers have been used to identify putative CSC sub-populations in different cancers. Notwithstanding, it has been acknowledged that breast CSC may originate from non-stem cancer cells (non-SCC), interconverting through an epithelial-to-mesenchymal transition-mediated process, and presenting several deregulated canonical and developmental signaling pathways. These support the heterogeneity that, directly or indirectly, influences fundamental biological features supporting breast tumor development. Accordingly, CSC have increasingly become highly relevant cellular targets. In this review, we will address the stemness concept in cancer, setting the perspective on CSC and their origin, by exploring their relation and regulation within the tumor microenvironment, in the context of emerging therapeutic targets. Within this framework, we will discuss nucleolin, a protein that has been associated with angiogenesis and, more recently, with the stemness phenotype, becoming a common denominator between CSC and non-SCC for multicellular targeting.

The design of peptide-amphiphiles as functional ligands for liposomal anticancer drug and gene delivery

Liposomal nanomedicine has led to clinically useful cancer therapeutics like Doxil and DaunoXome. In addition, peptide-functionalized liposomes represent an effective drug and gene delivery vehicle with increased cancer cell specificity, enhanced tumor-penetrating ability and high tumor growth inhibition. The goal of this article is to review the recently published literature of the peptide-amphiphiles that were used to functionalize liposomes, to highlight successful designs that improved drug and gene delivery to cancer cells in vitro, and cancer tumors in vivo, and to discuss the current challenges of designing these peptide-decorated liposomes for effective cancer treatment.

Enhanced Cytotoxicity of Folic Acid-Targeted Liposomes Co-Loaded with C6 Ceramide and Doxorubicin: In Vitro Evaluation on HeLa, A2780-ADR, and H69-AR Cells

Current research in cancer therapy is beginning to shift toward the use of combinational drug treatment regimens. However, the efficient delivery of drug combinations is governed by a number of complex factors in the clinical setting. Therefore, the ability to synchronize the pharmacokinetics of the individual therapeutic agents present in combination not only to allow for simultaneous tumor accumulation but also to allow for a synergistic relationship at the intracellular level could prove to be advantageous. In this work, we report the development of a novel folic acid-targeted liposomal formulation simultaneously co-loaded with C6 ceramide and doxorubicin [FA-(C6+Dox)-LP]. In vitro cytotoxicity assays showed that the FA-(C6+Dox)-LP was able to significantly reduce the IC50 of Dox when compared to that after the treatment with the doxorubicin-loaded liposomes (Dox-LP) as well as the untargeted drug co-loaded (C6+Dox)-LP on HeLa, A2780-ADR, and H69-AR cells. The analysis of the cell cycle distribution showed that while the C6 liposomes (C6-LP) did not cause cell cycle arrest, all the Dox-containing liposomes mediated cell cycle arrest in HeLa cells in the G2 phase at Dox concentrations of 0.3 and 1 μM and in the S phase at the higher concentrations. It was also found that this arrest in the S phase precedes the progression of the cells to apoptosis. The targeted FA-(C6+Dox)-LP were able to significantly enhance the induction of apoptotic events in HeLa cell monolayers as compared to the other treatment groups. Next, using time-lapse phase holographic imaging microscopy, it was found that upon treatment with the FA-(C6+Dox)-LP, the HeLa cells underwent rapid progression to apoptosis after 21 h as evidenced by a drastic drop in the average area of the cells after loss of cell membrane integrity. Finally, upon evaluation in a HeLa spheroid cell model, treatment with the FA-(C6+Dox)-LP showed significantly higher levels of cell death compared to those with C6-LP and Dox-LP. Overall, this study clearly shows that the co-delivery of C6 ceramide and Dox using a liposomal platform significantly correlates with an antiproliferative effect due to cell cycle regulation and subsequent induction of apoptosis and thus warrants its further evaluation in preclinical animal models.

Nucleolin overexpression in breast cancer cell sub-populations with different stem-like phenotype enables targeted intracellular delivery of synergistic drug combination

Breast cancer stem cells (CSC) are thought responsible for tumor growth and relapse, metastization and active evasion to standard chemotherapy. The recognition that CSC may originate from non-stem cancer cells (non-SCC) through plastic epithelial-to-mesenchymal transition turned these into relevant cell targets. Of crucial importance for successful therapeutic intervention is the identification of surface receptors overexpressed in both CSC and non-SCC. Cell surface nucleolin has been described as overexpressed in cancer cells as well as a tumor angiogenic marker. Herein we have addressed the questions on whether nucleolin was a common receptor among breast CSC and non-SCC and whether it could be exploited for targeting purposes. Liposomes functionalized with the nucleolin-binding F3 peptide, targeted simultaneously, nucleolin-overexpressing putative breast CSC and non-SCC, which was paralleled by OCT4 and NANOG mRNA levels in cells from triple negative breast cancer (TNBC) origin. In murine embryonic stem cells, both nucleolin mRNA levels and F3 peptide-targeted liposomes cellular association were dependent on the stemness status. An in vivo tumorigenic assay suggested that surface nucleolin overexpression per se, could be associated with the identification of highly tumorigenic TNBC cells. This proposed link between nucleolin expression and the stem-like phenotype in TNBC, enabled 100% cell death mediated by F3 peptide-targeted synergistic drug combination, suggesting the potential to abrogate the plasticity and adaptability associated with CSC and non-SCC. Ultimately, nucleolin-specific therapeutic tools capable of simultaneous debulk multiple cellular compartments of the tumor microenvironment may pave the way towards a specific treatment for TNBC patient care.

Targeting cancer cells in the tumor microenvironment: opportunities and challenges in combinatorial nanomedicine

Cancer therapies of the future will rely on synergy between drugs delivered in combination to achieve both maximum efficacy and decreased toxicity. Nanoscale drug delivery vehicles composed of highly tunable nanomaterials ('nanocarriers') represent the most promising approach to achieve simultaneous, cell-selective delivery of synergistic ratios of combinations of drugs within solid tumors. Nanocarriers are currently being used to co-encapsulate and deliver synergistic ratios of multiple anticancer drugs to target cells within solid tumors. Investigators exploit the unique environment associated with solid tumors, termed the tumor microenvironment (TME), to make 'smart' nanocarriers. These sophisticated nanocarriers exploit the pathological conditions in the TME, thereby creating highly targeted nanocarriers that release their drug payload in a spatially and temporally controlled manner. The translational and commercial potential of nanocarrier-based combinatorial nanomedicines in cancer therapy is now a reality as several companies have initiated human clinical trials.

Co-delivery of doxorubicin and PEGylated C16-ceramide by nanoliposomes for enhanced therapy against multidrug resistance

Aim: To develop novel nanoliposomes (Lip-ADR-Cer) codelivering doxorubicin (ADR) and PEGylated C16 ceramide (PEG-ceramide C16) to overcome multidrug resistance. Materials & methods: The antitumor activity and mechanism of Lip-ADR-Cer were evaluated. Results & conclusion: The IC50 of Lip-ADR-Cer after 48-h treatment with the MCF-7/ADR and HL-60/ADR cancer cells, both being ADR resistant, was 2.2- and 1.4-fold effective respectively versus the general nanoliposomes with no PEG-ceramide C16 (Lip-ADR). The antitumor assay in mice bearing MCF-7/ADR or HL-60/ADR xenograft tumors confirmed the superior antitumor activity of Lip-ADR-Cer over Lip-ADR. We found that the improved therapeutic effect of Lip-ADR-Cer may be attributed to both of the cytotoxic effect of PEG-ceramide C16 and glucosylceramide synthase overexpression in multidrug resistance cells.