Polymer conjugates: nanosized medicines for treating cancer

NIR light responsive core-shell nanocontainers for drug delivery

A novel near infrared (NIR)-triggered anticancer drug delivery system has been successfully constructed. Firstly, upconversion nanoparticles (UCNPs, NaYF₄:Tm,Yb@NaYF₄) were synthesized as a core and mesoporous silica (mSiO₂) as a shell to assemble the core-shell nanostructure (UCNP@mSiO₂) as the host. Supramolecular nanovalves based on α-cyclodextrin (α-CD) torus encircling a pimelic acid thread and being held in place by a cleavable stopper (nitrobenzyl alcohol) were used as nanoscopic caps to block the pore and inhibit drug diffusion. Upon irradiation with a 980 nm laser on the nanocomposites, the emitted ultraviolet light (UV, 360 nm) photocleaved the o-nitrobenzyl (ONB) photolabile group, causing these α-CD caps to dissociate from the stalk and release the drug. The "Ladder" pulsatile release-profiles, regulated by varying the intensity and time duration of NIR irradiation, further reveal the light-triggered release performance. In addition, without NIR irradiation, few immaturities ensure the high pharmacological efficacy. Moreover, the elaborate cell experiments, by using HeLa as model cancer cells, were also carried out to reveal the good biocompatibility, fast uptake and NIR light-sensitive toxicity. Therefore, the novel NIR light-triggered drug delivery system displays great potential for cancer therapy.

Mechanism study of peptide GMBP1 and its receptor GRP78 in modulating gastric cancer MDR by iTRAQ-based proteomic analysis

Background

Multidrug resistance (MDR) is a major obstacle to the treatment of gastric cancer (GC). Using a phage display approach, we previously obtained the peptide GMBP1, which specifically binds to the surface of MDR gastric cancer cells and is subsequently internalized. Furthermore, GMBP1 was shown to have the potential to reverse the MDR phenotype of gastric cancer cells, and GRP78 was identified as the receptor for this peptide. The present study aimed to investigate the mechanism of peptide GMBP1 and its receptor GRP78 in modulating gastric cancer MDR.

Methods

Fluorescence-activated cell sorting (FACS) and immunofluorescence staining were used to investigate the subcellular location and mechanism of GMBP1 internalization. iTRAQ was used to identify the MDR-associated downstream targets of GMBP1. Differentially expressed proteins were identified in GMBP1-treated compared to untreated SGC7901/ADR and SGC7901/VCR cells. GO and KEGG pathway analyses of the differentially expressed proteins revealed the interconnection of these proteins, the majority of which are involved in MDR. Two differentially expressed proteins were selected and validated by western blotting.

Results

GMBP1 and its receptor GRP78 were found to be localized in the cytoplasm of GC cells, and GRP78 can mediate the internalization of GMBP1 into MDR cells through the transferrin-related pathway. In total, 3,752 and 3,749 proteins were affected in GMBP1-treated SGC7901/ADR and SGC7901/VCR cells, respectively, involving 38 and 79 KEGG pathways. Two differentially expressed proteins, CTBP2 and EIF4E, were selected and validated by western blotting.

Conclusion

This study explored the role and downstream mechanism of GMBP1 in GC MDR, providing insight into the role of endoplasmic reticulum stress protein GRP78 in the MDR of cancer cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1361-3) contains supplementary material, which is available to authorized users.

Acetalated-dextran as valves of mesoporous silica particles for pH responsive intracellular drug delivery

A pH-sensitive drug release system using acetalated-dextran as valves was designed to manipulate smart intracellular release of anticancer drugs.

Synthesis of an acid-labile polymeric prodrug DOX-acetal-PEG-acetal-DOX with high drug loading content for pH-triggered intracellular drug release

PEGylated doxorubicin (DOX) prodrugs with high drug loading content have been prepared via a combination of CuAAC “click” reaction and ammonolysis reaction, which can be used for pH-triggered delivery of doxorubicin.

Smart branched polymer drug conjugates as nano-sized drug delivery systems

Branched polymers own special properties derived from their intrinsic characteristics. These properties make them ideal candidates to be used as carriers for an improved generation of polymer-drug conjugates.

Polymer-doxycycline conjugates as fibril disrupters: an approach towards the treatment of a rare amyloidotic disease

The term amyloidosis describes neurological diseases where an abnormal protein is misfolded and accumulated as deposits in organs and tissues, known as amyloid, disrupting their normal function. In the most common familial amyloid polyneuropathy (FAP), transthyretin (TTR) displays this role primarily affecting the peripheral nervous system (PNS). Advanced stages of this inherited rare amyloidosis, present as fibril deposits that are responsible for disease progression. In order to stop disease progression, herein we designed an efficient family of nanoconjugates as fibril disrupters. These polymer conjugates are based on doxycycline (doxy), already in phase II trials for Alzheimer's disease, covalently linked to poly-l-glutamic acid (PGA). The conjugates were rationally designed, looking at drug loading and drug release rate by adequate linker design, always considering the physiological conditions at the molecular target site. Conjugation of doxycycline exhibited greater potential towards TTR fibril disaggregation in vitro compared to the parent drug. Exhaustive physico-chemical evaluation of these polymer-drug conjugates concluded that drug release was unnecessary for activity, highlighting the importance of an appropriate linker. Furthermore, biodistribution studies through optical imaging (OI) and the use of radiolabelled polymer-drug conjugates demonstrated conjugate safety profile and renal clearance route of the selected PGA-doxy candidate, settling the adequacy of our conjugate for future in vivo evaluation. Furthermore, preliminary studies in an FAP in vivo model at early stages of disease development showed non-organ toxicity evidences. This nanosized-system raises a promising treatment for advanced stages of this rare amyloidotic disease, and also presents a starting point for possible application within other amyloidosis-related diseases, such as Alzheimer's disease.

Dry powders for oral inhalation free of lactose carrier particles

Dry powder inhaler (DPI) products have traditionally comprised a simple formulation of micronised drug mixed with a carrier excipient, typically lactose monohydrate. The presence of the carrier is aimed at overcoming issues of poor flowability and dispersibility, associated with the cohesive nature of small, micronised active pharmaceutical ingredient (API) particles. Both the powder blend and the DPI device must be carefully designed so as to ensure detachment of the micronised drug from the carrier excipient on inhalation. Over the last two decades there has been a significant body of research undertaken on the design of carrier-free formulations for DPI products. Many of these formulations are based on sophisticated particle engineering techniques; a common aim in formulation design of carrier-free products being to reduce the intrinsic cohesion of the particles, while maximising dispersion and delivery from the inhaler. In tandem with the development of alternative formulations has been the development of devices designed to ensure the efficient delivery and dispersion of carrier-free powder on inhalation. In this review we examine approaches to both the powder formulation and inhaler design for carrier-free DPI products.

Comparative study of the antitumor activity of Nab-paclitaxel and intraperitoneal solvent-based paclitaxel regarding peritoneal metastasis in gastric cancer

Intraperitoneal (i.p.) chemotherapy with paclitaxel (PTX) has been shown to be a promising treatment strategy for peritoneal metastasis. The present study focused on the comparative evaluation of the therapeutic efficacy of nanoparticle albumin-bound PTX (Nab-PTX) and i.p. administration of the conventional solvent-based PTX (Sb-PTX). We also investigated the difference in antitumor activity depending on the route of administration in the Nab-PTX treatment. Nab-PTX was administered i.p. or intravenously (i.v.) and Sb-PTX was administered i.p. at equitoxic and equal doses to nude mice bearing gastric cancer OCUM-2MD3 cell subcutaneous and peritoneal xenografts. Therapeutic efficacy of Sb-PTX and Nab-PTX was evaluated as inhibition of tumor growth using a peritoneal metastatic model with subcutaneous xenografts. The survival rate was also investigated using mouse peritoneal models. For assessment of subcutaneous tumors, the change in tumor volume was measured, and for assessment of peritoneal tumors, the weight of ascitic fluid and the total peritoneal tumor burden were measured for each individual mouse. At equitoxic doses, treatment with Nab-PTX resulted in a greater reduction in the size of subcutaneous tumors and the weight of ascites and peritoneal burden as compared with i.p. Sb-PTX (p<0.05). Treatment with i.p. and i.v. Nab-PTX also achieved greater survival benefit than i.p. Sb-PTX (p<0.05). In contrast, there was no significant difference in the degree of tumor reduction and the survival time between both drugs at equal doses. With regard to the route of administration, the antitumor efficacy of Nab-PTX after i.v. administration was equivalent to the efficacy after i.p. administration. These results suggest that i.v. Nab-PTX may be another encouraging treatment option that can target peritoneal dissemination in gastric cancer.

pH-Sensitive cationic copolymers of different macromolecular architecture as potential dexamethasone sodium phosphate delivery systems

This paper describes the synthesis and characterization of cationic copolymers with different macromolecular architecture and drug delivery properties of the corresponding dexamethasone sodium phosphate (DSP)-loaded systems. Copolyelectrolytes comprising poly[2-(acryloyloxy)ethyl] trimethylammonium chloride (PAETMAC) and poly(ethylene glycol) blocks as well as a tri-arm star-shaped PAETMAC were synthesized using cerium(IV) ion-mediated polymerization method. The obtained copolyelectrolytes and corresponding ionic associates with DSP have been characterized by (1)H NMR, Fourier Transform Infrared spectroscopy, and differential scanning calorimetry. The average diameter, size distribution, and ζ-potential of the copolymers and DSP-copolymer ionic associates were determined by dynamic light scattering, and particles were visualized by scanning electron microscopy and transmission electron microscopy. The biocompatibility and cytotoxicity of obtained copolymers were determined. In vitro drug release experiments were carried out to estimate the ability of the obtained nanoparticles for sustained release of DSP for a period of 24 h.

Efficacy of polyMPC-DOX prodrugs in 4T1 tumor-bearing mice

We report the in vivo efficacy, in tumor-bearing mice, of cancer prodrugs consisting of poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) conjugated to doxorubicin (DOX). Our synthesis of polyMPC-DOX conjugates established prodrugs with tunable drug loading, pH sensitive release kinetics, and a maximum tolerated dose in the range of 30-50 mg/kg (DOX equivalent) in healthy mice. Here we show prolonged circulation of polyMPC-DOX, with a measured in vivo half-life (t1/2) 8 times greater than that of the free drug. We observed reduced drug uptake in healthy tissue, and 2-3 times enhanced drug accumulation in tumors for polyMPC-DOX prodrugs compared to free DOX, using BALB/c mice bearing 4T1 tumors. Prolonged survival and reduced tumor growth were observed in mice receiving the polyMPC-DOX prodrug treatment. Moreover, we evaluated immunogenicity of polyMPC-DOX prodrugs by examining complete blood count (CBC) and characteristic cytokine responses, demonstrating no apparent innate or adaptive immune system response.

PEG-like nanoprobes: multimodal, pharmacokinetically and optically tunable nanomaterials

“PEG-like Nanoprobes” (PN’s) are pharmacokinetically and optically tunable nanomaterials whose disposition in biological systems can be determined by fluorescence or radioactivity. PN’s feature a unique design where a single PEG polymer surrounds a short fluorochrome and radiometal bearing peptide, and endows the resulting nanoprobe with pharmacokinetic control (based on molecular weight of the PEG selected) and optical tunability (based on the fluorochrome selected), while the chelate provides a radiolabeling option. PN’s were used to image brain capillary angiography (intravital 2-photon microscopy), tumor capillary permeability (intravital fluorescent microscopy), and the tumor enhanced permeability and retention (EPR) effect (¹¹¹In-PN and SPECT). Clinical applications of PN’s include use as long blood half-life fluorochromes for intraoperative angiography, for measurements of capillary permeability in breast cancer lesions, and to image EPR by SPECT, for stratifying patient candidates for long-circulating nanomedicines that may utilize the EPR mechanism.

Synthetic polyglutamylation of dual-functional MTX ligands for enhanced combined cytotoxicity of poly(I:C) nanoplexes

The antifolate drug methotrexate (MTX) can serve as a dual-functional ligand in antitumoral drug delivery, inducing both a folate receptor mediated cellular uptake and an intracellular cytotoxic action. Bioactivity of MTX however changes by conjugation; the activity can be affected by the hampered intracellular conversion to more potent poly-γ-glutamyl derivatives. Therefore, in a cancer combination therapy approach for the codelivery of cytotoxic dsRNA polyinosinic-polycytidylic acid poly(I:C), a set of molecularly precise oligo(ethanamino)amides were synthesized comprising poly(ethylene glycol) conjugated MTX ligands. The conjugates differed in the number of additional glutamic acid residues to investigate the effect of different degrees of synthetic "a priori" polyglutamylation. The bioactivity of these compounds concerning dihydrofolate reductase (DHFR) inhibition, cytotoxicity, nucleic acid binding potency, cellular uptake of poly(I:C) polyplexes, and combined antifolate/poly(I:C) toxicity was investigated. Synthetic polyglutamylation had a crucial impact on several stages of efficient poly(I:C) delivery and combined MTX cytotoxicity. DHFR inhibition of the conjugates significantly increased with increasing polyglutamate chain length. The library member with highest glutamylation degree even outperformed free MTX in direct comparison. Studies in KB cells showed the corresponding enhanced cytotoxicity by polyglutamylation. Also poly(I:C) polyplexes of the glutamylated MTX variants exhibited higher cellular uptake in the folate receptor positive cell line. Finally, a synergistic combined cytotoxicity of polyglutamylated MTX ligands and complexed poly(I:C) cargo was observed in transfected KB cells. The present structure-activity relationship study of MTX-based ligands pinpoints the concept of synthetic polyglutamylation as a promising approach for optimizing bioactivity of antifolate conjugates, which might be considered as a useful tool also in context of other drug delivery systems.

Bridging cancer biology and the patients' needs with nanotechnology-based approaches

Cancer remains as stressful condition and a leading cause of death in the western world. Actual cornerstone treatments of cancer disease rest as an elusive alternative, offering limited efficacy with extensive secondary effects as a result of severe cytotoxic effects in healthy tissues. The advent of nanotechnology brought the promise to revolutionize many fields including oncology, proposing advanced systems for cancer treatment. Drug delivery systems rest among the most successful examples of nanotechnology. Throughout time they have been able to evolve as a function of an increased understanding from cancer biology and the tumor microenvironment. Marketing of Doxil® unleashed a remarkable impulse in the development of drug delivery systems. Since then, several nanocarriers have been introduced, with aspirations to overrule previous technologies, demonstrating increased therapeutic efficacy besides decreased toxicity. Spatial and temporal targeting to cancer cells has been explored, as well as the use of drug combinations co-encapsulated in the same particle as a mean to take advantage of synergistic interactions in vivo. Importantly, targeted delivery of siRNA for gene silencing therapy has made its way to the clinic for a "first in man" trial using lipid-polymeric-based particles. Focusing in state-of-the-art technology, this review will provide an insightful vision on nanotechnology-based strategies for cancer treatment, approaching them from a tumor biology-driven perspective, since their early EPR-based dawn to the ones that have truly the potential to address unmet medical needs in the field of oncology, upon targeting key cell subpopulations from the tumor microenvironment.

Drug development for intraperitoneal chemotherapy against peritoneal carcinomatosis from gastrointestinal cancer

Intraperitoneal (IP) chemotherapy for peritoneal carcinomatosis (PC) from gastrointestinal cancer has been investigated and applied clinically for several decades. Cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy have been considered to be the optimal treatment options for selected patients with colorectal and gastric cancers with PC. Accumulating evidence suggests that the administration of IP paclitaxel for patients with PC from gastric cancer may improve the patient survival. The pharmacokinetics of such treatment should be considered to optimize IP chemotherapy. In addition, newly emerging molecular-targeted therapies and research into new drug delivery systems, such as nanomedicine or controlled absorption/release methods, are essential to improve the effects of IP chemotherapy. This review summarizes the current status and future prospects of IP chemotherapy for the treatment of gastrointestinal cancer.

Nanotechnology for targeted cancer therapy

Cancer nanotechnology is currently under intense development for applications in cancer imaging, molecular diagnosis and targeted therapy. The basic rationale is that nanometer-sized particles, such as biodegradable micelles, semiconductor quantum dots and iron oxide nanocrystals, have functional or structural properties that are not available from either molecular or macroscopic agents. When linked with biotargeting ligands, such as monoclonal antibodies, peptides or small molecules, these nanoparticles are used to target malignant tumors with high affinity and specificity. In the 'mesoscopic' size range of 5-100 nm in diameter, nanoparticles also have large surface areas and functional groups for conjugating to multiple diagnostic (e.g., optical, radioisotopic or magnetic) and therapeutic (e.g., anticancer) agents. Recent advances have led to multifunctional nanoparticle probes for molecular and cellular imaging, nanoparticle drugs for targeted therapy, and integrated nanodevices for early cancer detection and screening. These developments have opened exciting opportunities for personalized oncology in which cancer detection, diagnosis and therapy are tailored to each individual's molecular profile, and also for predictive oncology, in which genetic/molecular information is used to predict tumor development, progression and clinical outcome.

pH-responsive drug release from porous zinc sulfide nanospheres based on coordination bonding

A pH responsive system is reported based on the “COOH–Zn²⁺–drug” architecture via coordination bonding in ZnS nanospheres' mesopores.

A pH and thermosensitive choline phosphate-based delivery platform targeted to the acidic tumor microenvironment

Solid tumors generally exhibit an acidic microenvironment which has been recognized as a potential route to distinguishing tumor from normal tissue for purposes of drug delivery or imaging. To this end we describe a pH and temperature sensitive polymeric adhesive that can be derivatized to carry drugs or other agents and can be tuned synthetically to bind to tumor cells at pH 6.8 but not at pH 7.4 at 37 °C. The adhesive is based on the universal reaction between membrane phosphatidyl choline (PC) molecules and polymers derivatized with multiple copies of the inverse motif, choline phosphate (CP). The polymer family we use is a linear copolymer of a CP terminated tetraethoxymethacrylate and dimethylaminoethyl (DMAE) methacrylate, the latter providing pH sensitivity. The copolymer exhibits a lower critical solution temperature (LCST) just below 37 °C when the DMAE is uncharged at pH 7.4 but the LCST does not occur when the group is charged at pH 6.8 due to the ionization hydrophilicity. At 37 °C the polymer binds strongly to mammalian cells at pH 6.8 but does not bind at pH 7.4, potentially targeting tumor cells existing in an acidic microenvironment. We show the binding is strong, reversible if the pH is raised and is followed rapidly by cellular uptake of the fluorescently labeled material. Drug delivery utilizing this dually responsive family of polymers should provide a basis for targeting tumor cells with minimal side reactions against untransformed counterparts.

LHRH-targeted nanogels as a delivery system for cisplatin to ovarian cancer

Targeted drug delivery using multifunctional polymeric nanocarriers is a modern approach for cancer therapy. Our purpose was to prepare targeted nanogels for selective delivery of chemotherapeutic agent cisplatin to luteinizing hormone-releasing hormone (LHRH) receptor overexpressing tumor in vivo. Building blocks of such delivery systems consisted of innovative soft block copolymer nanogels with ionic cores serving as a reservoir for cisplatin (loading 35%) and a synthetic analogue of LHRH conjugated to the nanogels via poly(ethylene glycol) spacer. Covalent attachment of (D-Lys6)-LHRH to nanogels was shown to be possible without loss in either the ligand binding affinity or the nanogel drug incorporation ability. LHRH-nanogel accumulation was specific to the LHRH-receptor positive A2780 ovarian cancer cells and not toward LHRH-receptor negative SKOV-3 cells. The LHRH-nanogel cisplatin formulation was more effective and less toxic than equimolar doses of free cisplatin or untargeted nanogels in the treatment of receptor-positive ovarian cancer xenografts in mice. Collectively, the study indicates that LHRH mediated nanogel-cisplatin delivery is a promising formulation strategy for therapy of tumors that express the LHRH receptor.

A peptide derived from phage display library exhibits anti-tumor activity by targeting GRP78 in gastric cancer multidrug resistance cells

Multidrug resistance (MDR) remains a significant challenge to the clinical treatment of gastric cancer (GC). In the present study, using a phage display approach combined with MTT assays, we screened a specific peptide GMBP1 (Gastric cancer MDR cell-specific binding peptide), ETAPLSTMLSPY, which could bind to the surface of GC MDR cells specifically and reverse their MDR phenotypes. Immunocytochemical staining showed that the potential receptor of GMBP1 was located at the membrane and cytoplasm of MDR cells. In vitro and in vivo drug sensitivity assays, FACS analysis and Western blotting confirmed that GMBP1 was able to re-sensitize MDR cells to chemical drugs. Western blotting and proteomic approaches were used to screen the receptor of GMBP1, and GRP78, a MDR-related protein, was identified as a receptor of GMBP1. This result was further supported by immunofluoresence microscopy and Western blot. Additionally, Western blotting demonstrated that pre-incubation of GMBP1 in MDR cells greatly diminished MDR1, Bcl-2 and GRP78 expression but increased the expression of Bax, whereas downregulation of GRP78, function as a receptor and directly target for GMBP1, only inhibited MDR1 expression. Our findings suggest that GMBP1 could re-sensitize GC MDR cells to a variety of chemotherapeutic agents and this role might be mediated partly through down-regulating GRP78 expression and then inhibiting MDR1 expression. These findings indicate that peptide GMBP1 likely recognizes a novel GRP78 receptor and mediates cellular activities associated with the MDR phenotype, which provides new insight into research on the management of MDR in gastric cancer cells.

Anti-cancer effects of newly developed chemotherapeutic agent, glycoconjugated palladium (II) complex, against cisplatin-resistant gastric cancer cells

Background

Cisplatin (CDDP) is the most frequently used chemotherapeutic agent for various types of advanced cancer, including gastric cancer. However, almost all cancer cells acquire resistance against CDDP, and this phenomenon adversely affects prognosis. Thus, new chemotherapeutic agents that can overcome the CDDP-resistant cancer cells will improve the survival of advanced cancer patients.

Methods

We synthesized new glycoconjugated platinum (II) and palladium (II) complexes, [PtCl₂ (L)] and [PdCl₂ (L)]. CDDP-resistant gastric cancer cell lines were established by continuous exposure to CDDP, and gene expression in the CDDP-resistant gastric cancer cells was analyzed. The cytotoxicity and apoptosis induced by [PtCl₂ (L)] and [PdCl₂ (L)] in CDDP-sensitive and CDDP-resistant gastric cancer cells were evaluated. DNA double-strand breaks by drugs were assessed by evaluating phosphorylated histone H2AX. Xenograft tumor mouse models were established and antitumor effects were also examined in vivo.

Results

CDDP-resistant gastric cancer cells exhibit ABCB1 and CDKN2A gene up-regulation, as compared with CDDP-sensitive gastric cancer cells. In the analyses of CDDP-resistant gastric cancer cells, [PdCl₂ (L)] overcame cross-resistance to CDDP in vitro and in vivo. [PdCl₂ (L)] induced DNA double-strand breaks.

Conclusion

These results indicate that [PdCl₂ (L)] is a potent chemotherapeutic agent for CDDP-resistant gastric cancer and may have clinical applications.