Efficient overcoming of drug resistance to anticancer nucleoside analogs by nanodelivery of active phosphorylated drugs

Exploring the physicochemical properties of the integration of Tristearoyl uridine in Langmuir monolayers: An approach to cell membrane modeling for prodrugs

Understanding the mechanisms by which drugs interact with cell membranes is crucial for unraveling the underlying biochemical and biophysical processes that occur on the surface of these membranes. Our research focused on studying the interaction between an ester-type derivative of tristearoyl uridine and model cell membranes composed of lipid monolayers at the air-water interface. For that, we selected a specific lipid to simulate nontumorigenic cell membranes, namely 1,2-dihexadecanoyl-sn-glycero-3-phospho-l-serine. We noted significant changes in the surface pressure-area isotherms, with a noticeable shift towards larger areas, which was lower than expected for ideal mixtures, indicating monolayer condensation. Furthermore, the viscoelastic properties of the interfacial film demonstrated an increase in both the elastic and viscous parameters for the mixed film. We also observed structural alterations using vibrational spectroscopy, which revealed an increase in the all-trans to gauche conformers ratio. This confirmed the stiffening effect of the prodrug on the lipid monolayer. In summary, this study indicates that this lipophilic prodrug significantly impacts the lipid monolayer's thermodynamic, rheological, electrical, and molecular characteristics. This information is crucial for understanding how the drug interacts with specific sites on the cellular membrane. It also has implications for drug delivery, as the drug's passage into the cytosol may involve traversing the lipid bilayer.

Negative value of CD10-/CD34- immunophenotype in pediatric leukemia and development of a related cell line model for investigating drug resistance

PURPOSE

Appropriate sub-classification of leukemia according to the immunophenotypic characteristics of the malignant cells may improve therapeutic strategies. The aim of this study was to investigate the prognostic value of CD10/CD34 surface markers in pediatric acute lymphoblastic leukemia (pALL).

PATIENTS AND METHODS

A retrospective cohort study was performed in 79 children with ALL. Possible correlation between leukemia prognosis and CD10 CD34 immunophenotype was assessed using Kaplan-Meier and Cox regression analyses. A CD10- CD34- pre-B-ALL cell line was generated from a patient with resistant ALL. RN95 was characterized using light microscopy, immunophenotyping, karyotyping, and Western blotting. Drug sensitivity and resistant genes' expression profile were assessed using MTT and RT-PCR assays.

RESULTS

Kaplan-Meier analysis showed negative correlation between CD10/CD34 double negativity and patients' 2- and 5-year disease-free survival (DFS). Multivariate analysis indicated that the absence of CD10 and CD34 expression in the ALL patients was an independent negative prognostic marker for 2- and 5-year DFS. A novel cell line model, RN95, was developed with similar immunophenotype from a primary relapsed sample. Cells showed p53 positive functionality and demonstrated partial sensitivity to Vincristine, but complete resistance to Cytarabine. Overexpression of ABCB1, ABCA2, and ABCA3 was detected.

CONCLUSION

In the current study, simultaneous absence of CD10 and CD34 cell surface markers was introduced as an unfavorable prognostic factor in pediatric B-ALL. Moreover, a special cell line was established to help delineation of novel therapeutics for B-ALL drug resistance.

The evolution of nucleosidic analogues: self-assembly of prodrugs into nanoparticles for cancer drug delivery

Nucleoside and nucleotide analogs are essential tools in our limited arsenal in the fight against cancer. However, these structures face severe drawbacks such as rapid plasma degradation or hydrophilicity, limiting their clinical application. Here, different aspects of nucleoside and nucleotide analogs have been exposed, while providing their shortcomings. Aiming to improve their fate in the body and combating their drawbacks, two different approaches have been discussed, the prodrug and nanocarrier technologies. Finally, a novel approach called "PUFAylation" based on both the prodrug and nanocarrier technologies has been introduced, promising to be the supreme method to create a novel nucleoside or nucleotide analog based formulation, with enhanced efficacy and highly reduced toxicity.

Molecular Information on the Potential of Europium Complexes for Local Recognition of a Nucleoside-Based Drug by Using Nanostructured Interfaces Assembled as Langmuir-Blodgett Films

The production of nanostructured materials for biological and medical applications may be applied toward the conjugation of adequate substances to boost the stimulus response of sensors and diagnostic probes. In this sense, Langmuir-Blodgett films constituted of bioinspired and biomimetic materials have attracted attention because of the ease of manipulation of the molecular architecture. In this paper, we employed a nucleoside-based drug, which was linked with a sterol hydrophobic moiety (3',4'-acetonide-uridine-succinate-cholesterol conjugate) to provide it an amphiphilic character. The drug was spread on the air-water interface, alone or mixed with stearic acid, forming Langmuir monolayers, and the complex Eu(tta)₃(H₂O)₂ was incorporated in the drug-containing monolayer. Interactions at the air-water interface between stearic acid, the drug, and the europium complex were then investigated with tensiometry, surface potential, infrared spectroscopy, and Brewster angle microscopy. The Langmuir films were transferred to solid supports as Langmuir-Blodgett films, which presented luminescent properties that could be tuned according to the molecular architecture. We believe that these results can serve as a novel approach to characterize and assemble materials organized in the molecular scale for medical applications.

Molecular simulation and in vitro evaluation of chitosan nanoparticles as drug delivery systems for the controlled release of anticancer drug cytarabine against solid tumours

The present work is an attempt to integrate the molecular simulation studies with in vitro cytotoxicity of cytarabine-loaded chitosan nanoparticles and exploring the potential of this formulation as therapeutics for treating solid tumours. The molecular simulation was performed using GROMACS v5.4 in which, chitosan polymer (CHT; six molecules) was used to study the encapsulation and release of a single molecule of cytarabine. Root Mean Square Deviation (RMSD) of the Cα atom of cytarabine (CBR) molecule shows that CBR starts to diffuse out of the CHT polymer binding pocket around 10.2 ns, indicated by increased fluctuation of RMSD at pH 6.4, while the drug diffusion is delayed at pH 7.4 and starts diffusing around 17.5 ns. Cytarabine-loaded chitosan nanoparticles (CCNP), prepared by ionic gelation method were characterized for encapsulation efficiency, particle size and morphology, zeta potential, crystallinity and drug release profile at pH 6.4 and 7.4. CCNPs showed 64% encapsulation efficiency with an average diameter of 100 nm and zeta potential of + 53.9 mV. It was found that cytarabine existed in amorphous state in nanoformulation. In vitro release studies showed 70% cytarabine was released from the chitosan-based nanoformulation release at pH 6.4, which coincides with the pH of tumour microenvironment. Cytotoxicity against breast cancer cell line (MCF 7) was higher for nanoformulation compared to free cytarabine. Haemocompatibility studies showed that chitosan-based nanoformulation is safe, biocompatible and nonhaemolytic in nature; hence, can be used as a safe drug delivery system. Taken together, our study suggests that chitosan nanoformulation would be an effective strategy for the pH-dependent release of cytarabine against solid tumours and might impart better therapeutic efficiency.

Transporter-targeted cholic acid-cytarabine conjugates for improved oral absorption

Cytarabine has a poor oral absorption due to its rapid deamination and poor membrane permeability. Bile acid transporters are highly expressed both in enterocytes and hepatocytes and to increase the oral bioavailability and investigate the potential application of cytarabine for liver cancers, a transporter- recognizing prodrug strategy was applied to design and synthesize four conjugates of cytarabine with cholic acid (CA), chenodeoxycholic acid (CDCA), hyodeoxycholic acid (HDCA) and ursodeoxycholic acid (UDCA). The anticancer activities against HepG2 cells were evaluated by MTT assay and the role of bile acid transporters during cellular transport was investigated in a competitive inhibition experiment. The in vitro and in vivo metabolic stabilities of these conjugates were studied in rat plasma and liver homogenates. Finally, an oral bioavailability study was conducted in rats. All the cholic acid-cytarabine conjugates (40μM) showed potent antiproliferative activities (up to 70%) against HepG2 cells after incubation for 48h. The addition of bile acids could markedly reduce the antitumor activities of these conjugates. The N(4)-ursodeoxycholic acid conjugate of cytarabine (compound 5) exhibited optimal stability (t1/2=90min) in vitro and a 3.9-fold prolonged half-life of cytarabine in vivo. More importantly, compound 5 increased the oral bioavailability 2-fold compared with cytarabine. The results of the present study suggest that the prodrug strategy based on the bile acid transporters is suitable for improving the oral absorption and the clinical application of cytarabine.

How can nanomedicines overcome cellular-based anticancer drug resistance?

This review discusses the mechanisms of anticancer drug resistance according to its cellular level of action and outlines the nanomedicine-based strategies adopted to overcome it.

Increasing Tumor Accessibility with Conjugatable Disulfide-Bridged Tumor-Penetrating Peptides for Cancer Diagnosis and Treatment

Tumor-homing peptides with tissue-penetrating properties increase the efficacy of targeted cancer therapy by delivering an anticancer agent to the tumor interior. LyP-1 (CGNKRTRGC) and iRGD (CRGDKGPDC) are founding members of this class of peptides. The presence of the cysteines forming the cyclizing disulfide bond complicates conjugation of these peptides with other molecules, such as drugs. Here, we report the synthesis of conjugatable disulfide-bridged peptides and their conjugation to biologically important molecules. We have synthesized the LyP-1, iRGD, and CRGDC (GACRGDCLGA) peptides with a cysteine or maleimidohexanoic acid added externally at N-terminus of the sequences. Subsequent conjugation to payloads yielded stable compounds in which the tumor-homing properties of the peptide and the biological activity of the payload were retained.

Synthesis, properties, and biological activity of boranophosphate analogs of the mRNA cap: versatile tools for manipulation of therapeutically relevant cap-dependent processes

Modified mRNA cap analogs aid in the study of mRNA-related processes and may enable creation of novel therapeutic interventions. We report the synthesis and properties of 11 dinucleotide cap analogs bearing a single boranophosphate modification at either the α-, β- or γ-position of the 5',5'-triphosphate chain. The compounds can potentially serve either as inhibitors of translation in cancer cells or reagents for increasing expression of therapeutic proteins in vivo from exogenous mRNAs. The BH3-analogs were tested as substrates and binding partners for two major cytoplasmic cap-binding proteins, DcpS, a decapping pyrophosphatase, and eIF4E, a translation initiation factor. The susceptibility to DcpS was different between BH3-analogs and the corresponding analogs containing S instead of BH3 (S-analogs). Depending on its placement, the boranophosphate group weakened the interaction with DcpS but stabilized the interaction with eIF4E. The first of the properties makes the BH3-analogs more stable and the second, more potent as inhibitors of protein biosynthesis. Protein expression in dendritic cells was 2.2- and 1.7-fold higher for mRNAs capped with m2 (7,2'-O)GppBH3pG D1 and m2 (7,2'-O)GppBH3pG D2, respectively, than for in vitro transcribed mRNA capped with m2 (7,3'-O)GpppG. Higher expression of cancer antigens would make mRNAs containing m2 (7,2'-O)GppBH3pG D1 and m2 (7,2'-O)GppBH3pG D2 favorable for anticancer immunization.

Application of ProTide technology to gemcitabine: a successful approach to overcome the key cancer resistance mechanisms leads to a new agent (NUC-1031) in clinical development

Gemcitabine is a nucleoside analogue commonly used in cancer therapy but with limited efficacy due to a high susceptibility to cancer cell resistance. The addition of a phosphoramidate motif to the gemcitabine can protect it against many of the key cancer resistance mechanisms. We have synthesized a series of gemcitabine phosphoramidate prodrugs and screened for cytostatic activity in a range of different tumor cell lines. Among the synthesized compounds, one in particular (NUC-1031, 6f) was shown to be potent in vitro. Importantly, compared with gemcitabine, 6f activation was significantly less dependent on deoxycytidine kinase and on nucleoside transporters, and it was resistant to cytidine deaminase-mediated degradation. Moreover, 6f showed a significant reduction in tumor volumes in vivo in pancreatic cancer xenografts. The ProTide 6f is now in clinical development with encouraging efficacy signals in a Phase I/II study, which strongly supports the ProTide approach to generate promising new anticancer agents.

Reversal of multidrug resistance by stimuli-responsive drug delivery systems for therapy of tumor

Multidrug resistance (MDR) is a major obstacle to successful cancer therapy, especially for chemotherapy. The new drug delivery system (DDS) provides promising approaches to reverse MDR, for which the poor cellular uptake and insufficient intracellular drug release remain rate-limiting steps for reaching the drug concentration level within the therapeutic window. Stimulus-coupled drug delivery can control the drug-releasing pattern temporally and spatially, and improve the accumulation of chemotherapeutic agents at targeting sites. In this review, the applications of DDS which is responsive to different types of stimuli in MDR cancer therapy is introduced, and the design, construction, stimuli-sensitivity and the effect to reverse MDR of the stimuli-responsive DDS are discussed.

Biophysics of cell membrane lipids in cancer drug resistance: Implications for drug transport and drug delivery with nanoparticles

In this review, we focus on the biophysics of cell membrane lipids, particularly when cancers develop acquired drug resistance, and how biophysical changes in resistant cell membrane influence drug transport and nanoparticle-mediated drug delivery. Recent advances in membrane lipid research show the varied roles of lipids in regulating membrane P-glycoprotein function, membrane trafficking, apoptotic pathways, drug transport, and endocytic functions, particularly endocytosis, the primary mechanism of cellular uptake of nanoparticle-based drug delivery systems. Since acquired drug resistance alters lipid biosynthesis, understanding the role of lipids in cell membrane biophysics and its effect on drug transport is critical for developing effective therapeutic and drug delivery approaches to overcome drug resistance. Here we discuss novel strategies for (a) modulating the biophysical properties of membrane lipids of resistant cells to facilitate drug transport and regain endocytic function and (b) developing effective nanoparticles based on their biophysical interactions with membrane lipids to enhance drug delivery and overcome drug resistance.

Recent trends in cancer drug resistance reversal strategies using nanoparticles

INTRODUCTION

Resistance to chemotherapy is a major obstacle in the successful amelioration of tumors in many cancer patients. Resistance is either intrinsic or acquired, involving mechanisms such as genetic aberrations, decreased influx and increased efflux of drugs. Strategies for the reversal of resistance involve the alteration of enzymes responsible for drug resistance, the modulation of proteins regulating apoptosis mechanisms and improving the uptake of drugs using nanotechnology. Novel strides in the reversal of drug resistance are emerging, involving the use of nanotechnology, targeting stem cells, etc.

AREAS COVERED

This paper reviews the most recent cancer drug reversal strategies involving nanotechnology for targeting cancer cells and cancer stem cells (CSCs), for enhanced uptake of micro- and macromolecular inhibitors.

EXPERT OPINION

Nanotechnology used in conjunction with existing therapies, such as gene therapy and P-glycoprotein inhibition, has been shown to improve the reversal of drug resistance; the mechanisms involved in this include specific targeting of drugs and nucleotide therapeutics, enhanced cellular uptake of drugs and improved bioavailability of drugs with poor physicochemical characteristics. Important strategies in the reversal of drug resistance include: a multifunctional nanoparticulate system housing a targeting moiety; therapeutics to kill resistant cancer cells and CSCs; cytotoxic drugs and a tumor microenvironment stimuli-responsive element, to release the encapsulated therapeutics.

Drug-induced nanocarrier assembly as a strategy for the cellular delivery of nucleotides and nucleotide analogues

The natural nucleotide adenosine triphosphate (ATP) and nucleotide analogues such as azidothymidine triphosphate (AZT-TP) display important pharmacological activities for the treatment of ischemia and HIV infections, respectively. Their clinical use is, however, limited mostly due to their hydrophilicity, which highly restricts their diffusion into the target cells. Few nanocarriers have been proposed to address the challenge of ATP/AZT-TP cellular delivery, but the loading efficiency, preparation complexity, and efficient cellular delivery remain important barriers to their development. In this study, we propose an original, straightforward and versatile design of nucleotide and nucleotide analogue nanocarriers based on the natural polysaccharide chitosan (CS). We show that the drugs ATP and AZT-TP can induce ionotropic gelation of CS, leading to CS/ATP and CS/AZT-TP nanoparticles with high drug entrapment efficiency and loading rate-up to 44%. Such nanocarriers release ATP and AZT-TP in physiological media and allow an efficient in vitro cellular delivery of these molecules down to the cell cytoplasm.

Application of activated nucleoside analogs for the treatment of drug-resistant tumors by oral delivery of nanogel-drug conjugates

A majority of nanoencapsulated drugs that have shown promise in cancer chemotherapy are administered intravenously. Development of effective oral nanoformulations presents a very challenging medical goal. Here, we describe successful applications of innovative polymeric nanogels in the form of conjugates with activated nucleoside analogs for oral administration in cancer chemotherapy. Previously, we reported the synthesis of amphiphilic polyvinyl alcohol and dextrin-based nanogel conjugates with the phosphorylated 5-FU nucleoside Floxuridine and demonstrated their enhanced activity against regular and drug-resistant cancers (T.H. Senanayake, G. Warren, S.V. Vinogradov, Novel anticancer polymeric conjugates of activated nucleoside analogs, Bioconjug. Chem. 22 (2011) 1983-1993). In this study, we synthesized and evaluated oral applications of nanogel conjugates of a protected Gemcitabine, the drug never used in oral therapies. These conjugates were able to quickly release an active form of the drug (Gemcitabine 5'-mono-, di- and triphosphates) by specific enzymatic activities, or slowly during hydrolysis. Gemcitabine conjugates demonstrated up to 127 times higher in vitro efficacy than the free drug against various cancer cells, including the lines resistant to nucleoside analogs. Surprisingly, these nanogel-drug conjugates were relatively stable in gastric conditions and able to actively penetrate through the gastrointestinal barrier based on permeability studies in Caco-2 cell model. In tumor xenograft models of several drug-resistant human cancers, we observed an efficient inhibition of tumor growth and extended the life-span of the animals by 3 times that of the control with orally treated Gemcitabine- or Floxuridine-nanogel conjugates. Thus, we have demonstrated a potential of therapeutic nanogel conjugates with the activated and stabilized Gemcitabine as a successful oral drug form against Gemcitabine-resistant and other drug-resistant tumors.

Gemcitabine versus Modified Gemcitabine: a review of several promising chemical modifications

Gemcitabine, an anticancer agent which acts against a wide range of solid tumors, is known to be rapidly deaminated in blood to the inactive metabolite 2',2'-difluorodeoxyuridine and to be rapidly excreted by the urine. Moreover, many cancers develop resistance against this drug, such as loss of transporters and kinases responsible for the first phosphorylation step. To increase its therapeutic levels, gemcitabine is administered at high doses (1000 mg/m(2)) causing side effects (neutropenia, nausea, and so forth). To improve its metabolic stability and cytotoxic activity and to limit the phenomena of resistance many alternatives have emerged, such as the synthesis of prodrugs. Modifying an anticancer agent is not new; paclitaxel or ara-C has been subjected to such changes. This review summarizes the various chemical modifications that can be found in the 4-(N)- and 5'-positions of gemcitabine. They can provide (i) a protection against deamination, (ii) a better storage and (iii) a prolonged release in the cell, (iv) a possible use in the case of deoxycytidine kinase deficiency, and (v) transporter deficiency. These new gemcitabine-based sysems have the potential to improve the clinical outcome of a chemotherapy strategy.

Overcoming nucleoside analog chemoresistance of pancreatic cancer: a therapeutic challenge

Clinical refractoriness to nucleoside analogs (e.g., gemcitabine, capecitabine) is a major scientific problem and is one of the main reasons underlying the extremely poor prognostic state of pancreatic cancer. The drugs' effects are suboptimal partly due to cellular mechanisms limiting their transport, activation, and overall efficacy. Nonetheless, novel therapeutic approaches are presently under study to circumvent nucleoside analog resistance in pancreatic cancer. With these new approaches come additional challenges to be addressed. This review describes the determinants of chemoresistance in the gemcitabine cytotoxicity pathways, provides an overview of investigational approaches for overcoming chemoresistance, and discusses new challenges presented. Understanding the future directions of the field may assist in the successful development of novel treatment strategies for enhancing chemotherapeutic efficacy in pancreatic cancer.

Cancer stem cells and drug resistance: the potential of nanomedicine

Properties of the small group of cancer cells called tumor-initiating or cancer stem cells (CSCs) involved in drug resistance, metastasis and relapse of cancers can significantly affect tumor therapy. Importantly, tumor drug resistance seems to be closely related to many intrinsic or acquired properties of CSCs, such as quiescence, specific morphology, DNA repair ability and overexpression of antiapoptotic proteins, drug efflux transporters and detoxifying enzymes. The specific microenvironment (niche) and hypoxic stability provide additional protection against anticancer therapy for CSCs. Thus, CSC-focused therapy is destined to form the core of any effective anticancer strategy. Nanomedicine has great potential in the development of CSC-targeting drugs, controlled drug delivery and release, and the design of novel gene-specific drugs and diagnostic modalities. This review is focused on tumor drug resistance-related properties of CSCs and describes current nanomedicine approaches, which could form the basis of novel combination therapies for eliminating metastatic and CSCs.