Comparison of active and passive targeting of docetaxel for prostate cancer therapy by HPMA copolymer-RGDfK conjugates

Emerging frontiers in nanomedicine targeted therapy for prostate cancer

Prostate cancer is a prevalent cancer in men, often treated with chemotherapy. However, it tumor cells are clinically grows slowly and is heterogeneous, leading to treatment resistance and recurrence. Nanomedicines, through targeted delivery using nanocarriers, can enhance drug accumulation at the tumor site, sustain drug release, and counteract drug resistance. In addition, combination therapy using nanomedicines can target multiple cancer pathways, improving effectiveness and addressing tumor heterogeneity. The application of nanomedicine in prostate cancer treatment would be an important strategy in controlling tumor dynamic process as well as improve survival. Thus, this review highlights therapeutic nanoparticles as a solution for prostate cancer chemotherapy, exploring targeting strategies and approaches to combat drug resistance.

HPMA copolymer-collagen hybridizing peptide conjugates targeted to breast tumor extracellular matrix

The extracellular matrix (ECM) is dynamically involved in many aspects of cell growth and survival, and it plays an active role in cancer etiology. In comparison to healthy ECM, tumor associated ECM shows high collagen deposition and remodeling activity, which results in an increased amount of denatured collagen strands in tumor tissues. Capitalizing on this distinguishing feature, we developed tumor-localizing polymeric carriers that selectively bind to denatured collagen in the tumor ECM. We synthesized N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers with their side chains conjugated to collagen hybridizing peptides (CHPs). HPMA copolymer-CHP conjugates exhibited selective affinity to denatured collagen and localized to tumors in an orthotopic MDA-MB-231 murine breast cancer model. The conjugates had increased tumor localization compared to copolymers with scrambled peptides in the side chains, as well as increased retention compared to free CHPs. Such conjugates show promise as carriers for ECM-acting drugs and imaging agents in the management of diseases characterized by high ECM remodeling activity.

Combinatorial approaches of nanotherapeutics for inflammatory pathway targeted therapy of prostate cancer

Prostate cancer (PC) is the most prevalent male urogenital cancer worldwide. PC patients presenting an advanced or metastatic cancer succumb to the disease, even after therapeutic interventions including radiotherapy, surgery, androgen deprivation therapy (ADT), and chemotherapy. One of the hallmarks of PC is evading immune surveillance and chronic inflammation, which is a major challenge towards designing effective therapeutic formulations against PC. Chronic inflammation in PC is often characterized by tumor microenvironment alterations, epithelial-mesenchymal transition and extracellular matrix modifications. The inflammatory events are modulated by reactive nitrogen and oxygen species, inflammatory cytokines and chemokines. Major signaling pathways in PC includes androgen receptor, PI3K and NF-κB pathways and targeting these inter-linked pathways poses a major therapeutic challenge. Notably, many conventional treatments are clinically unsuccessful, due to lack of targetability and poor bioavailability of the therapeutics, untoward toxicity and multidrug resistance. The past decade witnessed an advancement of nanotechnology as an excellent therapeutic paradigm for PC therapy. Modern nanovectorization strategies such as stimuli-responsive and active PC targeting carriers offer controlled release patterns and superior anti-cancer effects. The current review initially describes the classification, inflammatory triggers and major inflammatory pathways of PC, various PC treatment strategies and their limitations. Subsequently, recent advancement in combinatorial nanotherapeutic approaches, which target PC inflammatory pathways, and the mechanism of action are discussed. Besides, the current clinical status and prospects of PC homing nanovectorization, and major challenges to be addressed towards the advancement PC therapy are also addressed.

HPMA-based polymeric conjugates in anticancer therapeutics

Polymer therapeutics has gained prominence due to an attractive structural polymer chemistry and its applications in diseases therapy. In this review, we discussed the development and capabilities of N-(2-hydroxypropyl) methacrylamide (HPMA) and HPMA-drug conjugates in cancer therapy. The design, architecture, and structural properties of HPMA make it a versatile system for the synthesis of polymeric conjugations for biomedical applications. Research suggests that HPMA could be a possible alternative for polymers such polyethylene glycol (PEG) in biomedical applications. Although numerous clinical trials of HPMA-drug conjugates are ongoing, yet no product has been successfully brought to the market. Thus, further research is required to develop HPMA-drug conjugates as successful cancer therapeutics.

Integrin-Mediated Delivery of Drugs and Nucleic Acids for Anti-Angiogenic Cancer Therapy: Current Landscape and Remaining Challenges

Angiogenesis, sprouting of new blood vessels from pre-existing vasculatures, plays a critical role in regulating tumor growth. Binding interactions between integrin, a heterodimeric transmembrane glycoprotein receptor, and its extracellular matrix (ECM) protein ligands govern the angiogenic potential of tumor endothelial cells. Integrin receptors are attractive targets in cancer therapy due to their overexpression on tumor endothelial cells, but not on quiescent blood vessels. These receptors are finding increasing applications in anti-angiogenic therapy via targeted delivery of chemotherapeutic drugs and nucleic acids to tumor vasculatures. The current article attempts to provide a retrospective account of the past developments, highlight important contemporary contributions and unresolved set-backs of this emerging field.

Tumor targeting with docosahexaenoic acid-conjugated docetaxel for inhibiting lung cancer metastasis to bone

Docetaxel (DTX) is currently used as a first- or second-line drug treatment for patients with lung cancer, however, it is less effective for the treatment of patients with bone metastasis of lung cancer. This is primarily due to the fact that docetaxel is nonspecific. In the present study, docosahexaenoic acid (DHA) was selected as a tumor-targeting ligand, and DHA-conjugated DTX (DTX-DHA) was prepared for inhibiting lung cancer metastasis to bone. The anti-cancer activity assay revealed that DTX-DHA exhibited a similar antitumor efficacy to DTX in vitro. The maximum tolerated dose of DTX-DHA was increased compared with that of DTX. The present study results indicated that DTX-DHA exhibited an improved inhibition efficacy of lung cancer metastasis to bone in comparison with DTX in vivo. Encouragingly, the mean survival time of the DTX-DHA group (30.60 days) was increased compared with the DTX group (26.10 days; P<0.01). Furthermore, the results of cell migration and osteoclast-induced formation assays suggested that DTX-DHA inhibited lung cancer metastasis to bone primarily by affecting lung cancer cell migration. These results indicate that DTX-DHA may exhibit a potential therapeutic effect against lung cancer metastasis to bone.

Synergistic Targeting and Efficient Photodynamic Therapy Based on Graphene Oxide Quantum Dot-Upconversion Nanocrystal Hybrid Nanoparticles

Locating nanotherapeutics at the active sites, especially in the subcellular scale, is of great importance for nanoparticle-based photodynamic therapy (PDT) and other nanotherapies. However, subcellular targeting agents are generally nonspecific, despite the fact that the accumulation of a nanoformulation at active organelles leads to better therapeutic efficacy. A PDT nanoformulation is herein designed by using graphene oxide quantum dots (GOQDs) with rich functional groups as both the supporter for dual targeting modification and the photosensitizer for generating reactive oxygen species, and upconversion nanoparticles (UCNs) as the transducer of excitation light. A tumor-targeting agent, folic acid, and a mitochondrion-targeting moiety, carboxybutyl triphenylphosphonium, are simultaneously attached onto the UCNs-GOQDs hybrid nanoparticles by surface modification, and a synergistic targeting effect is obtained for these nanoparticles according to both in vitro and in vivo experiments. More significant cell death and a higher extent of mitochondrion damage are observed compared to the results of UCNs-GOQDs nanoparticles with no or just one targeting moiety. Furthermore, the PDT efficacy on tumor-bearing mice is also effectively improved. Overall, the current work presents a synergistic strategy to enhance subcellular targeting and the PDT efficacy for cancer therapy, which may also shed light on other kinds of nanotherapies.

Peptide ligand-modified nanomedicines for targeting cells at the tumor microenvironment

Since their initial discovery more than 30years ago, tumor-homing peptides have become an increasingly useful tool for targeted delivery of therapeutic and diagnostic agents into tumors. Today, it is well accepted that cells at the tumor microenvironment (TME) contribute in many ways to cancer development and progression. Tumor-homing peptide-decorated nanomedicines can interact specifically with surface receptors expressed on cells in the TME, improve cellular uptake of nanomedicines by target cells, and impair tumor growth and progression. Moreover, peptide ligand-modified nanomedicines can potentially accumulate in the target tissue at higher concentrations than would small conjugates, thus increasing overall target tissue exposure to the therapeutic agent, enhance therapeutic efficacy and reduce side effects. This review describes the most studied peptide ligands aimed at targeting cells in the TME, discusses major obstacles and principles in the design of ligands for drug targeting and provides an overview of homing peptides in ligand-targeted nanomedicines that are currently in development for cancer therapy and diagnosis.

Modulating angiogenesis with integrin-targeted nanomedicines

Targeting angiogenesis-related pathologies, which include tumorigenesis and metastatic processes, has become an attractive strategy for the development of efficient guided nanomedicines. In this respect, integrins are cell-adhesion molecules involved in angiogenesis signaling pathways and are overexpressed in many angiogenic processes. Therefore, they represent specific biomarkers not only to monitor disease progression but also to rationally design targeted nanomedicines. Arginine-glycine-aspartic (RGD) containing peptides that bind to specific integrins have been widely utilized to provide ligand-mediated targeting capabilities to small molecules, peptides, proteins, and antibodies, as well as to drug/imaging agent-containing nanomedicines, with the final aim of maximizing their therapeutic index. Within this review, we aim to cover recent and relevant examples of different integrin-assisted nanosystems including polymeric nanoconstructs, liposomes, and inorganic nanoparticles applied in drug/gene therapy as well as imaging and theranostics. We will also critically address the overall benefits of integrin-targeting.

Integrin-targeted nano-sized polymeric systems for paclitaxel conjugation: a comparative study

The generation of rationally designed polymer therapeutics via the conjugation of low molecular weight anti-cancer drugs to water-soluble polymeric nanocarriers aims to improve the therapeutic index. Here, we focus on applying polymer therapeutics to target two cell compartments simultaneously - tumour cells and angiogenic endothelial cells. Comparing different polymeric backbones carrying the same therapeutic agent and targeting moiety may shed light on any correlation between the choice of polymer and the anti-cancer activity of the conjugate. Here, we compared three paclitaxel (PTX)-bound conjugates with poly-l-glutamic acid (PGA, 4.9 mol%), 2-hydroxypropylmethacrylamide (HPMA, 1.2 mol%) copolymer, or polyethyleneglycol (PEG, 1:1 conjugate). PGA and HPMA copolymers are multivalent polymers that allow the conjugation of multiple compounds within the same polymer backbone, while PEG is a bivalent commercially available Food and Drug Administration (FDA)-approved polymer. We further conjugated PGA-PTX and PEG-PTX with the integrin α_vβ₃-targeting moiety RGD (5.5 mol% and 1:1 conjugate, respectively). We based our selection on the overexpression of integrin α_vβ₃ on angiogenic endothelial cells and several types of cancer cells. Our findings suggest that the polymer structure has major effect on the conjugate's activity on different tumour compartments. A multivalent PGA-PTX-E-[c(RGDfK)₂] conjugate displayed a stronger inhibitory effect on the endothelial compartment, showing a 50% inhibition of the migration of human umbilical vein endothelial cell cells, while a PTX-PEG-E-[c(RGDfK)₂] conjugate possessed enhanced anti-cancer activity on MDA-MB-231 tumour cells (IC₅₀ = 20 nM versus IC₅₀ 300 nM for the PGA conjugate).

Docetaxel‐loaded solid lipid nanoparticles: a novel drug delivery system

Over the past few years, taxanes have emerged as a new class of anticancer drugs. Docetaxel (DTX) the prototype of this class has been approved for the treatment of broad range of cancers. However, to date the commercial preparation of DTX (Taxotere^®) is accompanying adverse side effects, intolerance, and poor solubility, which can be overcome by encapsulating them using solid lipid nanoparticles (SLNs). SLNs represent versatile delivery system of drugs with newer forms such as polymer–solid lipid hybrid, surface modified and long circulating nanoparticles bringing forth improved prospects for cancer chemotherapy. In this review, the authors have discussed the current uses of various SLNs formulations of DTX with key emphasis on controlled and site‐specific drug delivery along with enhanced antitumour activity elucidated via in vitro and in vivo studies. Furthermore, the review article highlights few approaches that can be used in combination with existing DTX‐loaded SLNs to supplement DTX drug delivery.

Enhanced efficacy of combination heat shock targeted polymer therapeutics with high intensity focused ultrasound

Combination of polymer therapeutics and hyperthermia has been shown to enhance accumulation in selectively heated tumor tissue. The additional use of heat shock (HS)-targeting towards tumor tissues can further enhance accumulation and retention, and improve therapeutic outcomes. In this work, high intensity focused ultrasound (HIFU) was used to generate hyperthermia in prostate tumor tissue. Upregulation of the cell surface HS receptor glucose regulated protein 78 kDa (GRP78) was observed after treatment with HIFU hyperthermia which was then targeted by specific HS-targeting peptides. We used the peptide sequence WDLAWMFRLPVG attached to the side chains of water-soluble N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing docetaxel (DOC) conjugated via a lysosomally degradable linker. It was shown that HIFU-mediated HS-targeted copolymer-DOC conjugates improved treatment efficacy in a murine prostate tumor xenograft model. These results show that the use of HIFU hyperthermia in combination with HS-targeted polymer-drug conjugates has potential to improve therapeutic outcomes in prostate cancer treatment.

PEG based anti-cancer drug conjugated prodrug micelles for the delivery of anti-cancer agents

Development of polymer prodrug conjugates has evolved recently in the nano-medicine field for cancer diagnosis and treatment. This review focuses on the development of different types of PEG based polymer drug conjugates used for the delivery of anti-cancer agents.

Novel folate-targeted docetaxel-loaded nanoparticles for tumour targeting: in vitro and in vivo evaluation

Cholesterol-PEG₁₀₀₀-FA (folic acid) was synthesized as a stabilizer to encapsulate DTX, for the construction of a promising targeted delivery system for breast cancer therapy.

Strategies of polymeric nanoparticles for enhanced internalization in cancer therapy

In order to achieve long circulation time and high drug accumulation in the tumor sites via the EPR effects, anticancer drugs have to be protected by non-fouling polymers such as poly(ethylene glycol) (PEG), poly(ethylene oxide) (PEO), dextran, and poly(acrylic acid) (PAA). However, the dense layer of stealth polymer also prohibits efficient uptake of anticancer drugs by target cancer cells. For cancer therapy, it is often more desirable to accomplish rapid cellular uptake after anticancer drugs arriving at the pathological site, which could on one hand maximize the therapeutic efficacy and on the other hand reduce probability of drug resistance in cells. In this review, special attention will be focused on the recent potential strategies that can enable drug-loaded polymeric nanoparticles to rapidly recognize cancer cells, leading to enhanced internalization.

Effective suppression of the Kirsten rat sarcoma viral oncogene in pancreatic tumor cells via targeted small interfering RNA delivery using nanoparticles

OBJECTIVES

The objective of this study was to establish an efficient carrier for small interfering RNA (siRNA) delivery targeting pancreatic tumor cells.

METHODS

A copolymer consisting of a single-chain variable fragment targeted to human CD44 variant 6 (scFv(CD44v6)) functional group conjugated to polyethylene glycol-poly-L-lysine was synthesized and assembled into micelles encapsulating the siRNAs. Flow cytometry and Western blot assays were performed to evaluate the transfection efficiency and gene-silencing effect of the siRNAs. Afterward, (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, Transwell, soft agar colony formation, and enzyme-linked immunosorbent assays were performed to evaluate the biological functions of PANC-1 cells after Kirsten rat sarcoma viral oncogene knockdown. In vivo assays were performed using a BALB/c (nu/nu) mouse model subcutaneously injected with PANC-1 xenografts. Real-time in vivo fluorescence imaging was used to monitor the tumor homing of the nanoparticles.

RESULTS

The scFv(CD44v6) enabled more efficient delivery of siRNAs and exhibited enhanced gene silencing compared with nontargeted nanoparticles. Furthermore, targeted delivery of the siRNAs induced a potent inhibitory effect on cell proliferation, colony formation, invasion, and vascular endothelial growth factor production. The animal assays revealed that single-chain variable fragment nanoparticles accumulated in the tumor tissue and enhanced the inhibition of tumor growth in vivo.

CONCLUSIONS

The scFv(CD44v6)-conjugated nanocarriers provide a highly efficient and safe platform for systemic gene therapy for pancreatic cancer.

In vitro synergistic action of geldanamycin- and docetaxel-containing HPMA copolymer-RGDfK conjugates against ovarian cancer

HPMA copolymer-RGDfK (HPMA-RGDfK) conjugates bearing either aminohexylgeldanamycin (AHGDM) or docetaxel (DOC) were synthesized and characterized. In vitro stability and binding were evaluated. Cytotoxicity toward ovarian cancer cells was evaluated and the ability of the conjugates to induce cell death was assessed by combination index analysis. Conjugates bearing AHGDM were more stable and exhibited slower drug release than those bearing DOC. Both conjugates demonstrated the ability to bind to avb3 integrins. In combination, HPMA-RGDfK conjugates demonstrated marked synergism as compared to their non-targeted counterparts and free drug controls. HPMA-RGDfK conjugates bearing AHGDM and DOC induce synergistic cytotoxicity in vitro, suggesting their potential as a promising combination therapy.

The influence of bile salt on the chemotherapeutic response of docetaxel-loaded thermosensitive nanomicelles

The primary aim of this work was to investigate the potential of bile salt, sodium taurocholate (NaTC), in improving the bioavailability and anti-tumor efficacy of docetaxel (DCT) upon rectal administration. Poloxamer-based nanomicelles with thermosensitive and mucoadhesive properties were prepared using the cold method. The optimized nanomicellar formulation was evaluated in terms of physicochemical and viscoelastic parameters. Nanomicelles containing bile salt maintained sufficient gelation strength (234×10² mPa·s) and mucoadhesive force (17.3×10² dyne/cm²) to be retained in the upper part of the rectum. They significantly enhanced the DCT internalization across the rectal mucosa and showed a high plasma level during the first 4 hours of the study period, compared to nanomicelles with no bile salt. As a result, a slightly higher rectal bioavailability of ~33% was observed in nanomicelles containing bile salt, compared to ~28% from the latter system. The higher pharmacokinetic parameters for rectally administered DCT/P407/P188/Tween 80/NaTC (0.25%/11%/15%/10%/0.1% by weight, respectively) resulted in significant anti-tumor efficacy. However, the tumor regression rate for the NaTC group was not statistically different from that for nanomicelles without NaTC. Therefore, overall results suggest that thermosensitive nanomicelles could be a potential dosage form for improvement of the bioavailability and chemotherapeutic profile of DCT.

Preparation, characterization, and antitumor activities of folate-decorated docetaxel-loaded human serum albumin nanoparticles

CONTEXT

Docetaxel is now a major antitumor drug in clinical use for the treatment of a variety of tumors. The ethanol/Tween 80 solvent required in the formulation to increase the docetaxel solubility is at least partly responsible for the hypersensitivity reaction, decreased uptake by tumor tissue, and increased exposure to other body compartments.

OBJECTIVE

The present study was aimed at developing hydrosoluble DTX-FA-HSANPs targeting tumor cells and to investigate antitumor activities of the nanoparticles.

MATERIALS AND METHODS

The DTX-HSANPs were prepared using a desolvation technique and the carboxylic groups of NHS-folate were conjugated with the amino groups of the human serum albumin nanoparticles, and studied their size and zeta potential, drug loading efficiency, surface morphology, release properties in vitro, and antitumor activities.

RESULTS

The spherical nanoparticles obtained were negatively charged with a zeta potential of about -30 mV and characterized around 150 nm with a narrow size distribution. Drug loading efficiency was approximately 17.2%. The folate-decorated nanoparticles targeted a human hepatoma cell line effectively. The in vitro drug release of DTX-FA-HSANPs in the first 96 h corresponded with the following equation: Q = 18.87851 - 0.13866t + 0.21276t² - 0.00704t³ + 0.0000847854t⁴ - 0.00000034991t⁵ (R² = 0.98155). Moreover, the in vitro antitumor activities of DTX-FA-HSANPs were close to the activities of the positive control (docetaxel). The in vivo inhibition ratios of DTX-FA-HSANPs and docetaxel were 66.2% and 59.5%, respectively, at a dose of 5 mg/kg.

DISCUSSION AND CONCLUSION

In light of the observed antitumor activities, it would be of considerable interest to collect sufficient data for the clinical application of docetaxel-loaded nanoparticles.

Tumor Targeting via Integrin Ligands

Selective and targeted delivery of drugs to tumors is a major challenge for an effective cancer therapy and also to overcome the side-effects associated with current treatments. Overexpression of various receptors on tumor cells is a characteristic structural and biochemical aspect of tumors and distinguishes them from physiologically normal cells. This abnormal feature is therefore suitable for selectively directing anticancer molecules to tumors by using ligands that can preferentially recognize such receptors. Several subtypes of integrin receptors that are crucial for cell adhesion, cell signaling, cell viability, and motility have been shown to have an upregulated expression on cancer cells. Thus, ligands that recognize specific integrin subtypes represent excellent candidates to be conjugated to drugs or drug carrier systems and be targeted to tumors. In this regard, integrins recognizing the RGD cell adhesive sequence have been extensively targeted for tumor-specific drug delivery. Here we review key recent examples on the presentation of RGD-based integrin ligands by means of distinct drug-delivery systems, and discuss the prospects of such therapies to specifically target tumor cells.

Overcoming the stromal barrier for targeted delivery of HPMA copolymers to pancreatic tumors

Delivery of macromolecules to pancreatic cancer is inhibited by a dense extracellular matrix composed of hyaluronic acid, smooth muscle actin and collagen fibers. Hyaluronic acid causes a high intratumoral fluidic pressure which prevents diffusion and penetration into the pancreatic tumor. This study involves the breaking down of hyaluronic acid by treating CAPAN-1 xenograft tumors in athymic nu/nu mice with targeted N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers radiolabeled with (111)In for single photon emission computerized tomography (SPECT) imaging. Two targeting strategies were investigated including αvβ3 integrin and HER2 receptors. HPMA copolymers were targeted to these receptors by conjugating short peptide ligands cRGDfK and KCCYSL to the side chains of the copolymer. Results demonstrate that tumor targeting can be achieved in vivo after treatment with hyaluronidase. This approach shows promise for enhanced delivery of polymer-peptide conjugates to solid tumors.

How nanotechnology can enhance docetaxel therapy

Docetaxel has been recognized as one of the most efficient anticancer drugs over the past decade; however, its poor water solubility and systemic toxicity have greatly limited its clinical application. In recent decades, the emergence of nanotechnology has provided new drug delivery systems for docetaxel, which can improve its water solubility, minimize the side effects and increase the tumor-targeting distribution by passive or active targeting. This review focuses on the research progress in nanoformulations related to docetaxel delivery – such as polymer-based, lipid-based, and lipid-polymer hybrid nanocarriers, as well as inorganic nanoparticles – addressing their structures, characteristics, preparation, physicochemical properties, methods by which drugs are loaded into them, and their in vitro and in vivo efficacies. Further, the targeted ligands used in the docetaxel nanoformulations, such as monoclonal antibodies, peptides, folic acid, transferrin, aptamers and hyaluronic acid, are described. The issues to overcome before docetaxel nanoformulations can be used in clinical and commercial applications are also discussed.

Passive and active hepatoma tumor targeting of new N-(2-hydroxypropyl)methacrylamide copolymer conjugates: synthesis, characterization, and evaluation in vitro and in vivo

Human hepatocellular carcinoma (HCC) is one of the major causes of death worldwide. To investigate the relative importance of active and passive targeting strategies, the synthesis, characterization, in vitro uptake, and in vivo biodistribution of specific sulfapyridine HPMA (HPMA: N-(2-hydroxypropyl methacrylamide)) copolymer (sulfapyridine: SPD) conjugates, nonspecific HPMA copolymer conjugates, and DTPA are described in this study. The poly(HPMA)-SPD-DTPA (DTPA: diethylenetriaminepentaacetic acid), poly(HPMA)-DTPA, and DTPA conjugates were radiolabeled with the radionuclide (99m)Tc and tested for uptake by cultured H22 cells. The cellular accumulation of poly(HPMA)-SPD-DTPA-(99m)Tc complex was found to be time-dependent. The poly(HPMA)-SPD-DTPA-(99m)Tc tracer exhibited rapid uptake kinetics in cell culture with a t(1/2) of ~5 min. The uptake of poly(HPMA)-SPD-DTPA-(99m)Tc was significantly higher than that of poly(HPMA)-DTPA-(99m)Tc, indicating that the uptake of the poly(HPMA)-SPD-DTPA-(99m)T was active binding. The uptake of poly(HPMA)-DTPA-(99m)Tc was significantly higher than that of DTPA-(99m)Tc, suggesting that the uptake of the poly(HPMA)-DTPA-(99m)T was passive binding. Twenty-four hour necropsy data in the hepatocellular carcinoma tumor model showed significantly higher (p < 0.001) tumor localization for poly(HPMA)-SPD-DTPA-(99m)Tc (4.98 ± 0.48%ID/g [percentage injected dose per gram tissue]) compared with poly(HPMA)-DTPA-(99m)Tc (2.69 ± 0.15% ID/g) and DTPA-(99m)Tc (0.83 ± 0.03%ID/g). Moreover, higher T/B for poly(HPMA)-SPD-DTPA-(99m)Tc indicated reduced extravazation of the targeted polymeric conjugates in normal tissues. Specific molecular targeting and nonspecific vascular permeability are both significant in the relative tumor localization of poly(HPMA)-SPD-DTPA-(99m)Tc. Extravascular leak in nonspecific organs appears to be a major factor in reducing the T/B for the sulfapyridine molecules. Thus, the poly(HPMA)-SPD-DTPA is expected to be used as the potential macromolecular targeting carrier for hepatoma carcinoma in mice.

Synergistic enhancement of cancer therapy using a combination of heat shock protein targeted HPMA copolymer-drug conjugates and gold nanorod induced hyperthermia

In the field of nanomedicine, selective delivery to cancer cells is a common goal, where active targeting strategies are often employed to increase tumor accumulation. In this study, tumor hyperthermia was utilized as a means to increase the active delivery of heat shock protein (HSP) targeted N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-drug conjugates. Following hyperthermia, induced expression of cell surface heat shock protein (HSP) glucose regulated protein 78 kDa (GRP78) was utilized for targeted drug therapy. Conjugates bearing the anticancer agents aminohexylgeldanamycin (AHGDM), docetaxel (DOC), or cisplatin and the GRP78 targeting peptide WDLAWMFRLPVG were synthesized and characterized. Binding to cell surface expressed heat shock protein GRP78 on the surface of human prostate cancer DU145 cells was evaluated. HSP targeted AHGDM and DOC conjugates demonstrated active binding comparable to native targeting peptide. They were then assessed in vitro for the ability to synergistically induce cytotoxicity in combination with moderate hyperthermia (43 °C, 30 min). HSP targeted DOC conjugates exhibited high potency against DU145 cells with an IC₅₀ of 2.4 nM. HSP targeted AHGDM and DOC conjugates demonstrated synergistic effects in combination with hyperthermia with combination index values of 0.65 and 0.45 respectively. Based on these results, HSP targeted DOC conjugates were selected for in vivo evaluation. In DU145 tumor bearing mice, a single treatment of tumor hyperthermia, induced via gold nanorod mediated plasmonic photothermal therapy, and intravenous administration of HSP targeted HPMA copolymer-docetaxel at 10mg/kg resulted in maintained tumor regression for a period of 30 days. These results demonstrate the potential for tumor hyperthermia to increase the delivery of HSP targeted macromolecular chemotherapeutics.

Docetaxel-loaded thermosensitive and bioadhesive nanomicelles as a rectal drug delivery system for enhanced chemotherapeutic effect

PURPOSE

To investigate the potential of thermosensitive and biadhesive nanomicelles in improving the bioavailability of docetaxel (DCT) and its chemotherapeutic effect.

METHOD

DCT-loaded nanomicelles were prepared by emulsufication and characterized in terms of physico-chemical and visco-elastic parameters. The optimzed formulation was evaluated for in vivo localization, pharmacokinetic and anti-tumor efficacy.

RESULTS

The hydrodynamic size of DCT-loaded nanomicelles was approximately 13 nm and the nanomicelles exhibited a sufficient gelation strength (9250 mPa·s) and bioadhesive force (2100 dyn/cm²) to be retained in the upper part of rectum. We observed a high rectal bioavailability of 29% DCT compared to that following oral administration in rats, as it successfully evaded the multidrug efflux transporters and hepatic first-pass metabolism. Plasma concentration around ∼50 ng/mL was maintained throughout the study period (12 h) while Taxotere® attained subtherapeutic range within 4 h of drug administration. Results also revealed that the rectally administered DCT-loaded nanomicelles exhibited a significant anti-tumor effect (200 mm³) with a reduced toxicity profile when compared to orally administered DCT (950 mm³). Furthermore, histological study showed that the rectal mucosa was completely intact with no signs of irritation upon treatment with DCT-loaded nanomicelles.

CONCLUSIONS

Taken together, our novel thermosensitive and biadhesive nanomicelles demonstrated the ability to improve the bioavailability and chemotherapeutic potential of DCT in vivo. To the best of our knowledge, this is the first report describing the rectal delivery of DCT-loaded nanomicelles.

Efficacious hepatoma-targeted nanomedicine self-assembled from galactopeptide and doxorubicin driven by two-stage physical interactions

Polymers bearing pendant galactosyl group are attractive for targeted intracellular antitumor drug delivery to hepatoma cells (e.g. HepG2 and SMMC7721 cells) with asialoglycoprotein receptor (ASGP-R). Herein, a series of galactopeptides was synthesized through ring-opening polymerization of L-glutamate N-carboxyanhydride, deprotection of benzyl group and subsequent Huisgens cycloaddition "click" reaction with azide-modified galactosyl group. The copolypeptides were revealed to have excellent hemocompatibilities, and cell and tissue compatibilities, which rendered their potential for drug delivery applications. The hepatoma-targeted micellar nanoparticle (i.e. nanomedicine) was fabricated by cooperative self-assembly of galactopeptide and doxorubicin (DOX) induced by two-stage physical interactions. In vitro DOX release from nanomedicine was accelerated in the intracellular acidic condition. Through the recognition between galactose ligand and ASGP-R of HepG2 cells, the endocytosis of galactosylated nanomedicine was significantly promoted, which was demonstrated by confocal laser scanning microscopy and flow cytometry. Remarkably, the galactose-decorated nanomedicine retained much higher antitumor activity toward HepG2 cells in contrast to the nanomedicine without galactosyl group in vitro and in vivo. The above superiorities indicated that the galactosylated nanomedicine possessed great promising for hepatoma-targeted chemotherapy.

Synthesis, characterization, and in vivo evaluation of tumor targeting N-(2-hydroxypropyl)methacrylamide copolymer conjugates containing sulfamethazine groups

Recent studies have identified that sulfadiazine derivatives can be concentrated in the hepatocellular carcinoma tissue. Herein, we report the synthesis, characterization, and evaluation of a novel sulfamethazine N-(2-hydroxypropyl)methacrylamide copolymer conjugates for tumor targeting. N-(3-Aminopropyl)methacrylamide-diethylenetriaminepentaacetic acid monomer 1, methacryloyl-sulfamethazine monomer 2, poly( N-(2-hydroxypropyl)methacrylamide)-sulfamethazine-diethylenetriaminepentaacetic acid conjugate 4, and poly( N-(2-hydroxypropyl)methacrylamide)-sulfamethazine-diethylenetriaminepentaacetic acid-99mTc were successfully synthesized and characterized. Poly( N-(2-hydroxypropyl)methacrylamide)-diethylenetriaminepentaacetic acid conjugate 3, diethylenetriaminepentaacetic acid-99mTc, and poly( N-(2-hydroxypropyl)methacrylamide)-diethylenetriaminepentaacetic acid-99mTc were also synthesized and characterized for comparison (99mTc: metastable technetium-99). A 24-h necropsy data in the hepatocellular carcinoma tumor model showed significantly higher ( p < 0.001) tumor localization for poly( N-(2-hydroxypropyl)methacrylamide)-sulfamethazine-diethylenetriaminepentaacetic acid-99mTc (4.82%ID/g ± 0.46%ID/g (percentage injected dose per gram tissue)) compared with poly( N-(2-hydroxypropyl)methacrylamide)-diethylenetriaminepentaacetic acid-99mTc (2.69%ID/g ± 0.15%ID/g) and diethylenetriaminepentaacetic acid-99mTc (0.83%ID/g ± 0.03%ID/g). Moreover, higher tumor/organ ratios for poly( N-(2-hydroxypropyl)methacrylamide)-sulfamethazine-diethylenetriaminepentaacetic acid-99mTc indicated reduced extravasation of the targeted polymeric conjugates in normal tissues. Thus, the poly( N-(2-hydroxypropyl)methacrylamide)-sulfamethazine-diethylenetriaminepentaacetic acid can potentially be used as a macromolecular targeting carrier for hepatocellular carcinoma in mice.

RGD-Binding Integrins in Prostate Cancer: Expression Patterns and Therapeutic Prospects against Bone Metastasis

Prostate cancer is the third leading cause of male cancer deaths in the developed world. The current lack of highly specific detection methods and efficient therapeutic agents for advanced disease have been identified as problems requiring further research. The integrins play a vital role in the cross-talk between the cell and extracellular matrix, enhancing the growth, migration, invasion and metastasis of cancer cells. Progression and metastasis of prostate adenocarcinoma is strongly associated with changes in integrin expression, notably abnormal expression and activation of the β₃ integrins in tumour cells, which promotes haematogenous spread and tumour growth in bone. As such, influencing integrin cell expression and function using targeted therapeutics represents a potential treatment for bone metastasis, the most common and debilitating complication of advanced prostate cancer. In this review, we highlight the multiple ways in which RGD-binding integrins contribute to prostate cancer progression and metastasis, and identify the rationale for development of multi-integrin antagonists targeting the RGD-binding subfamily as molecularly targeted agents for its treatment.

Docetaxel nanotechnology in anticancer therapy

Taxanes have been recognized as a family of very efficient anticancer drugs, but the formulation in use for the two main taxanes-Taxol for paclitaxel and Taxotere for docetaxel-have shown dramatic side effects. Whereas several new formulations for paclitaxel have recently appeared, such as Abraxane and others currently in various phases of clinical trials, there is no new formulation in clinical trials for the other main taxane, docetaxel, except BIND-014, a polymeric nanoparticle, which recently entered phase I clinical testing. Therefore, we review herein the state of the art and recent abundance in published results of academic approaches toward nanotechnology-based drug-delivery systems containing nanocarriers and targeting agents for docetaxel formulations. These efforts will certainly enrich the spectrum of docetaxel treatments in the near future. Taxotere's systemic toxicity, low water solubility, and other side effects are significant problems that must be overcome. To avoid the limitations of docetaxel in clinical use, researchers have developed efficient drug-delivery assemblies that consist of a nanocarrier, a targeting agent, and the drug. A wide variety of such engineered nanosystems have been shown to transport and eventually vectorize docetaxel more efficiently than Taxotere in vitro, in vivo, and in pre-clinical administration. Recent progress in drug vectorization has involved a combined therapy and diagnostic ("theranostic") approach in a single drug-delivery vector and could significantly improve the efficiency of such an anticancer drug as well as other drug types.

Polymeric conjugates for drug delivery

The field of polymer therapeutics has evolved over the past decade and has resulted in the development of polymer-drug conjugates with a wide variety of architectures and chemical properties. Whereas traditional non-degradable polymeric carriers such as poly(ethylene glycol) (PEG) and N-(2-hydroxypropyl methacrylamide) (HPMA) copolymers have been translated to use in the clinic, functionalized polymer-drug conjugates are increasingly being utilized to obtain biodegradable, stimuli-sensitive, and targeted systems in an attempt to further enhance localized drug delivery and ease of elimination. In addition, the study of conjugates bearing both therapeutic and diagnostic agents has resulted in multifunctional carriers with the potential to both "see and treat" patients. In this paper, the rational design of polymer-drug conjugates will be discussed followed by a review of different classes of conjugates currently under investigation. The design and chemistry used for the synthesis of various conjugates will be presented with additional comments on their potential applications and current developmental status.

Biological evaluation of RGDfK-gold nanorod conjugates for prostate cancer treatment

Selective delivery of gold nanorods (GNRs) to sites of prostate tumor angiogenesis is potentially advantageous for localized photothermal therapy. Here, we report the cellular uptake and biodistribution of GNRs surface functionalized with the cyclic RGDfK peptide. The GNRs were synthesized to have a surface plasmon resonance (SPR) peak at 800?nm and grafted with a thiolated poly(ethylene glycol) (PEG) corona with or without RGDfK. The binding and uptake of the targeted (RGDfK) and untargeted GNRs were evaluated in DU145 prostate cancer and human umbilical vein endothelial cells (HUVEC) by high-resolution dark field microscopy, inductively coupled plasma mass spectrometry (ICP-MS), and transmission electron microscopy (TEM). The biodistribution of both GNRs was then evaluated in prostate tumor bearing mice. Targeting of the RGDfK surface-modified GNRs was confirmed in vitro due to selective binding and uptake by endothelial cells. Tumor targeting was not observed in vivo, however, due to fast clearance of the RGDfK-GNRs from the blood. Further modifications of the nanoparticle?s surface properties are needed to enhance localization of the targetable system in sites of tumor angiogenesis.