Luteinizing hormone-releasing hormone receptor-targeted deslorelin-docetaxel conjugate enhances efficacy of docetaxel in prostate cancer therapy

Au/Doc/Quer@PDA/A10-3.2 Nanoparticles for targeted treatment of docetaxel-resistant prostate cancer

Docetaxel (Doc), as a first-line chemotherapy drug for prostate cancer (PC), often loses its therapeutic efficacy due to acquired resistance and lack of targeting specificity. Therefore, there is a need to develop a novel drug that can overcome Doc resistance and enhance its targeting ability to inhibit PC progression. In this study, we prepared Au/Doc/Quer@PDA/A10-3.2 nanoparticles (NPs) composite drug by encapsulating Doc and quercetin (Quer) within polydopamine (PDA)-coated Au NPs and further modifying them with RNA oligonucleotide aptamer A10-3.2. A10-3.2 was used for specific targeting of prostate-specific membrane antigen (PSMA)-positive PC cells (LNCaP). Quer was employed to reverse the resistance of Doc-resistant cell line (LNCaP/R) to Doc. Physical characterization using ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) confirmed the successful preparation of Au/Doc/Quer@PDA/A10-3.2 NPs. Fluorescence imaging and flow cytometry experiments demonstrated the targeting ability of Au/Doc/Quer@PDA/A10-3.2 NPs towards PSMA-positive LNCaP/R cells. Cell proliferation, apoptosis, invasion, and migration experiments revealed that Quer reversed the resistance of LNCaP/R cells to Doc. Immunoblotting experiments further confirmed the mechanism behind sensitization of chemotherapy by Quer. Finally, we evaluated the therapeutic efficacy of Au/Doc/Quer@PDA/A10-3.2 NPs in a mouse model of PC. In conclusion, this study synthesized and validated a novel nano-composite drug (Au/Doc/Quer@PDA/A10-3.2 NPs) for combating Doc-resistant PC, which could potentially be applied in clinical treatment of PC.

Integrin αvβ3 and LHRH Receptor Double Directed Nano-Analogue Effective Against Ovarian Cancer in Mice Model

Introduction

The high mortality rate of malignant ovarian cancer is attributed to the absence of effective early diagnosis methods. The LHRH receptor is specifically overexpressed in most ovarian cancers, and the integrin αvβ3 receptor is also overexpressed on the surface of ovarian cancer cells. In this study, we designed LHRH analogues (LHRHa)/RGD co-modified paclitaxel liposomes (LHRHa-RGD-LP-PTX) to target LHRH receptor-positive ovarian cancers more effectively and enhance the anti-ovarian cancer effects.

Methods

LHRHa-RGD-LP-PTX liposomes were prepared using the thin film hydration method. The morphology, physicochemical properties, cellular uptake, and cell viability were assessed. Additionally, the cellular uptake mechanism of the modified liposomes was investigated using various endocytic inhibitors. The inhibitory effect of the formulations on tumor spheroids was observed under a microscope. The co-localization with lysosomes was visualized using confocal laser scanning microscopy (CLSM), and the in vivo tumor-targeting ability of the formulations was assessed using the IVIS fluorescent imaging system. Finally, the in vivo anti-tumor efficacy of the formulations was evaluated in the armpits of BALB/c nude mice.

Results

The results indicated that LHRHa-RGD-LP-PTX significantly enhanced cellular uptake in A2780 cells, increased cytotoxicity, and hand a more potent inhibitory effect on tumor spheroids of A2780 cells. It also showed enhanced co-localization with endosomes or lysosome in A2780 cells, improved tumor-targeting capability, and demonstrated an enhanced anti-tumor effect in LHRHR-positive ovarian cancers.

Conclusion

The designed LHRHa-RGD-LP-PTX liposomes significantly enhanced the tumor-targeting ability and therapeutic efficacy for LHRH receptor-positive ovarian cancers.

In-vivo studies of targeted and localized cancer drug release from microporous poly-di-methyl-siloxane (PDMS) devices for the treatment of triple negative breast cancer

Triple-negative breast cancer (TNBC) treatment is challenging and frequently characterized by an aggressive phenotype and low prognosis in comparison to other subtypes. This paper presents fabricated implantable drug-loaded microporous poly-di-methyl-siloxane (PDMS) devices for the delivery of targeted therapeutic agents [Luteinizing Hormone-Releasing Hormone conjugated paclitaxel (PTX-LHRH) and Luteinizing Hormone-Releasing Hormone conjugated prodigiosin (PG-LHRH)] for the treatment and possible prevention of triple-negative cancer recurrence. In vitro assessment using the Alamar blue assay demonstrated a significant reduction (p < 0.05) in percentage of cell growth in a time-dependent manner in the groups treated with PG, PG-LHRH, PTX, and PTX-LHRH. Subcutaneous triple-negative xenograft breast tumors were then induced in athymic female nude mice that were four weeks old. Two weeks later, the tumors were surgically but partially removed, and the device implanted. Mice were observed for tumor regrowth and organ toxicity. The animal study revealed that there was no tumor regrowth, six weeks post-treatment, when the LHRH targeted drugs (LHRH-PTX and LHRH-PGS) were used for the treatment. The possible cytotoxic effects of the released drugs on the liver, kidney, and lung are assessed using quantitative biochemical assay from blood samples of the treatment groups. Ex vivo histopathological results from organ tissues showed that the targeted cancer drugs released from the implantable drug-loaded device did not induce any adverse effect on the liver, kidneys, or lungs, based on the results of qualitative toxicity studies. The implications of the results are discussed for the targeted and localized treatment of triple negative breast cancer.

Multiplatform Metabolomics Studies of Human Cancers With NMR and Mass Spectrometry Imaging

The status of metabolomics as a scientific branch has evolved from proof-of-concept to applications in science, particularly in medical research. To comprehensively evaluate disease metabolomics, multiplatform approaches of NMR combining with mass spectrometry (MS) have been investigated and reported. This mixed-methods approach allows for the exploitation of each individual technique's unique advantages to maximize results. In this article, we present our findings from combined NMR and MS imaging (MSI) analysis of human lung and prostate cancers. We further provide critical discussions of the current status of NMR and MS combined human prostate and lung cancer metabolomics studies to emphasize the enhanced metabolomics ability of the multiplatform approach.

Polypeptides-Drug Conjugates for Anticancer Therapy

Polypeptides are an important class of biodegradable polymers that have been widely used in drug delivery field. Owing to the controllable synthesis and robust side chain-functionalization ability, polypeptides have long been ideal candidates for conjugation with anticancer drugs. The chemical conjugation of anticancer drugs with polypeptides, termed polypeptides-drug conjugates, has demonstrated several advantages in improving pharmacokinetics, enhancing drug targeting, and controlling drug release, thereby leading to enhanced therapeutic outcomes with reduced side toxicities. This review focuses on the recent advances in the design and preparation of polypeptides-drug conjugates for enhanced anticancer therapy. Strategies for conjugation of different types of drugs, including small-molecule chemotherapeutic drugs, proteins, vascular disrupting agents, and gas molecules, onto polypeptides backbone are summarized. Finally, the challenges and future perspectives on the development of innovative polypeptides-drug conjugates for clinical cancer treatment are also presented.

Dissecting the Hormonal Signaling Landscape in Castration-Resistant Prostate Cancer

Understanding the molecular mechanisms underlying prostate cancer (PCa) progression towards its most aggressive, castration-resistant (CRPC) stage is urgently needed to improve the therapeutic options for this almost incurable pathology. Interestingly, CRPC is known to be characterized by a peculiar hormonal landscape. It is now well established that the androgen/androgen receptor (AR) axis is still active in CRPC cells. The persistent activity of this axis in PCa progression has been shown to be related to different mechanisms, such as intratumoral androgen synthesis, AR amplification and mutations, AR mRNA alternative splicing, increased expression/activity of AR-related transcription factors and coregulators. The hypothalamic gonadotropin-releasing hormone (GnRH), by binding to its specific receptors (GnRH-Rs) at the pituitary level, plays a pivotal role in the regulation of the reproductive functions. GnRH and GnRH-R are also expressed in different types of tumors, including PCa. Specifically, it has been demonstrated that, in CRPC cells, the activation of GnRH-Rs is associated with a significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic activity. This antitumor activity is mainly mediated by the GnRH-R-associated Gαi/cAMP signaling pathway. In this review, we dissect the molecular mechanisms underlying the role of the androgen/AR and GnRH/GnRH-R axes in CRPC progression and the possible therapeutic implications.

Gonadotropin-Releasing Hormone Receptors in Prostate Cancer: Molecular Aspects and Biological Functions

Pituitary Gonadotropin-Releasing Hormone receptors (GnRH-R) mediate the activity of the hypothalamic decapeptide GnRH, thus playing a key role in the regulation of the reproductive axis. Early-stage prostate cancer (PCa) is dependent on serum androgen levels, and androgen-deprivation therapy (ADT), based on GnRH agonists and antagonists, represents the standard therapeutic approach for PCa patients. Unfortunately, the tumor often progresses towards the more aggressive castration-resistant prostate cancer (CRPC) stage. GnRH receptors are also expressed in CRPC tissues, where their binding to both GnRH agonists and antagonists is associated with significant antiproliferative/proapoptotic, antimetastatic and antiangiogenic effects, mediated by the Gαi/cAMP signaling cascade. GnRH agonists and antagonists are now considered as an effective therapeutic strategy for CRPC patients with many clinical trials demonstrating that the combined use of these drugs with standard therapies (i.e., docetaxel, enzalutamide, abiraterone) significantly improves disease-free survival. In this context, GnRH-based bioconjugates (cytotoxic drugs covalently linked to a GnRH-based decapeptide) have been recently developed. The rationale of this treatment is that the GnRH peptide selectively binds to its receptors, delivering the cytotoxic drug to CRPC cells while sparing nontumor cells. Some of these compounds have already entered clinical trials.

Synthesis and Antiproliferative Activities of Conjugates of Paclitaxel and Camptothecin with a Cyclic Cell-Penetrating Peptide

Cell-penetrating peptide [WR]₅ has been previously shown to be an efficient molecular transporter for various hydrophilic and hydrophobic molecules. The peptide was synthesized using Fmoc/tBu solid-phase chemistry, and one arginine was replaced with one lysine to enable the conjugation with the anticancer drugs. Paclitaxel (PTX) was functionalized with an esterification reaction at the C2' hydroxyl group of PTX with glutaric anhydride and conjugated with the cyclic peptide [W(WR)₄K(βAla)] in DMF to obtain the peptide-drug conjugate PTX1. Furthermore, camptothecin (CPT) was modified at the C(20)-hydroxyl group through the reaction with triphosgene. Then, it was conjugated with two functionalized cyclic peptides through a formyl linker affording two different conjugates, namely CPT1 and CPT2. All the conjugates showed better water solubility as compared to the parent drug. The cytotoxicity assay of the drugs and their conjugates with the peptides were evaluated in the human breast cancer MCF-7 cell line. PTX inhibited cell proliferation by 39% while the PTX-peptide conjugate inhibited the proliferation by ~18% after 72 h incubation. On the other hand, CPT, CPT1, and CPT2 reduced the cell proliferation by 68%, 39%, and 62%, respectively, in the MCF-7 cell lines at 5 µM concentration after 72 h incubation.

Cancer-targeted delivery systems based on peptides

There is a growing interest for the discovery of new cancer-targeted delivery systems for drug delivery and diagnosis. A synopsis of the bibliographic data will be presented on bombesin, neurotensin, octreotide, Arg-Gly-Asp, luteinizing hormone-releasing hormone and other peptides. Many of them have reached the clinics for therapeutic or diagnostic purposes, and have been utilized as carriers of known cytotoxic agents such as doxorubicin, paclitaxel, cisplatin, methotrexate or dyes and radioisotopes. In our article, recent advances in the development of peptides as carriers of cytotoxic drugs or radiometals will be analyzed.

Preparation, characterization, drug release and computational modelling studies of antibiotics loaded amorphous chitin nanoparticles

We present a computational investigation of binding affinity of different types of drugs with chitin nanocarriers. Understanding the chitn polymer-drug interaction is important to design and optimize the chitin based drug delivery systems. The binding affinity of three different types of anti-bacterial drugs Ethionamide (ETA) Methacycline (MET) and Rifampicin (RIF) with amorphous chitin nanoparticles (AC-NPs) were studied by integrating computational and experimental techniques. The binding energies (BE) of hydrophobic ETA, hydrophilic MET and hydrophobic RIF were -7.3kcal/mol, -5.1kcal/mol and -8.1kcal/mol respectively, with respect to AC-NPs, using molecular docking studies. This theoretical result was in good correlation with the experimental studies of AC-drug loading and drug entrapment efficiencies of MET (3.5±0.1 and 25± 2%), ETA (5.6±0.02 and 45±4%) and RIF (8.9±0.20 and 53±5%) drugs respectively. Stability studies of the drug encapsulated nanoparticles showed stable values of size, zeta and polydispersity index at 6°C temperature. The correlation between computational BE and experimental drug entrapment efficiencies of RIF, ETA and MET drugs with four AC-NPs strands were 0.999 respectively, while that of the drug loading efficiencies were 0.854 respectively. Further, the molecular docking results predict the atomic level details derived from the electrostatic, hydrogen bonding and hydrophobic interactions of the drug and nanoparticle for its encapsulation and loading in the chitin-based host-guest nanosystems. The present results thus revealed the drug loading and drug delivery insights and has the potential of reducing the time and cost of processing new antibiotic drug delivery nanosystem optimization, development and discovery.

A conjugate of methotrexate and an analog of luteinizing hormone releasing hormone shows increased efficacy against prostate cancer

LHRH receptor, is over-expressed in a variety of human tumors and, is a potential binding site for targeted metastatic prostate cancer therapy. The objectives of our study were to synthesize a bioconjugate of the LHRH analog [DLys⁶]-LHRH and the anti-tumor agent methotrexate and test the hypothesis that [DLys⁶]-LHRH-MTX targets and inhibits prostate cancer cell growth in vitro and in vivo. The results of in vitro studies, showed that both [DLys⁶]-LHRH-MTX and MTX displayed superior cytotoxicity against prostate cancer cells in a concentration-dependent manners, with IC₅₀ concentrations for PC-3 cells of, 1.02 ± 0.18 μmol/L and 6.34 ± 1.01 μmol/L; for DU-145 cells, 1.53 ± 0.27 μmol/L and 8.03 ± 1.29 μmol/L; and for LNCaP cells, 1.93 ± 0.19 μmol/L and 9.68 ± 1.24 μmol/L, respectively. The IC₅₀ values of [DLys⁶]-LHRH-MTX and MTX were 110.77 ± 15.31 μmol/L and 42.33 ± 7.25 μmol/L, respectively. Finally, [DLys⁶]-LHRH-MTX significantly improved the anti-tumor activity of MTX in nude mice bearing PC-3 tumor xenografts. The inhibition ratios of tumor volume and tumor weight in the [DLys⁶]-LHRH-MTX treated group were significantly higher than those in the MTX-treated group. Tumor volume doubling time was also significantly extended from 6.13 days in control animals to 9.67 days in mice treated with [DLys⁶]-LHRH-MTX. In conclusion, [DLys⁶]-LHRH -MTX may be useful in treating prostate cancer.

Luteinizing hormone-releasing hormone peptide tethered nanoparticulate system for enhanced antitumoral efficacy of paclitaxel

Aim: Paclitaxel (PTX) is an effective anticancer agent used in the therapy of a wide variety of cancers. However, the drug is difficult to formulate due to its low solubility, and therefore, it is administered under slow infusion with castor oil/ethanol solution as surfactant that causes serious side effects. This investigation investigates leutinizing hormone releasing hormone (LHRH)-tethered nanparticulate system as modality for cancer-specific delivery of PTX and therefore minimizing the adverse effects. Materials & methods: LHRH-tethered poly(lactic-co-glycolic acid) copolymer with poly ethylene glycol side chain was synthesized, characterized and employed to formulate PTX-loaded nanoparticulate system. Results & conclusion: The developed nanoparticulate appears to be proficient in carrying as well as targeted delivery of PTX with improved therapeutic efficacy and better safety.

Targeted delivery of a novel peptide–docetaxel conjugate to MCF-7 cells through neuropilin-1 receptor: reduced toxicity and enhanced efficacy of docetaxel

A novel peptide docetaxel conjugate selectively kills NRP-1 overexpressing breast cancer cells, enhances anticancer activity of docetaxel without affecting the NRP-1 negative cells.

Recent discoveries and developments of androgen receptor based therapy for prostate cancer

The main focus of this review is to discuss the discoveries and developments of various therapies for prostate cancer.

Effect of lipidated gonadotropin-releasing hormone peptides on receptor mediated binding and uptake into prostate cancer cells in vitro

Gonadotropin-releasing hormone (GnRH) receptors are overexpressed on many cancer cells but not on primary cell lines. This study was designed to investigate the targeting ability and uptake of dendritic lipidated [Gln(1)]-GnRH peptide analogues on receptor-positive prostate cancer PC-3 cells relative to receptor-negative ovarian carcinoma SKOV-3 cells for potential application in drug delivery. Direct antiproliferative effect of these was investigated on three GnRH-receptor positive cancer cells, PC-3, LNCaP and DU145. A significant dose dependent growth inhibitory effect was produced in DU145 cells by 5 dendrimers giving an IC50 value of 22-35 μM. All compounds were non-toxic to the normal peripheral blood mononuclear cells.

FROM THE CLINICAL EDITOR

This study demonstrates the use of specific dendritic lapidated GnRH analogues in growth inhibition of GnRH receptor positive prostate cancer cell lines, suggesting potential future clinical use of this or similar strategies to address GnRH receptor positive cancer cells.

Prostate cancer relevant antigens and enzymes for targeted drug delivery

Chemotherapy is one of the most widely used approaches in combating advanced prostate cancer, but its therapeutic efficacy is usually insufficient due to poor specificity and associated toxicity. Lack of targeted delivery to prostate cancer cells is also the primary obstacles in achieving feasible therapeutic effect of other promising agents including peptide, protein, and nucleic acid. Consequently, there remains a critical need for strategies to increase the selectivity of anti-prostate cancer agents. This review will focus on various prostate cancer-relevant antigens and enzymes that could be exploited for prostate cancer targeted drug delivery. Among various targeting strategies, active targeting is the most advanced approach to specifically deliver drugs to their designated cancer cells. In this approach, drug carriers are modified with targeting ligands that can specifically bind to prostate cancer-specific antigens. Moreover, there are several specific enzymes in the tumor microenvironment of prostate cancer that can be exploited for stimulus-responsive drug delivery systems. These systems can specifically release the active drug in the tumor microenvironment of prostate cancer, leading to enhanced tumor penetration efficiency.

GnRH receptors in cancer: from cell biology to novel targeted therapeutic strategies

The crucial role of pituitary GnRH receptors (GnRH-R) in the control of reproductive functions is well established. These receptors are the target of GnRH agonists (through receptor desensitization) and antagonists (through receptor blockade) for the treatment of steroid-dependent pathologies, including hormone-dependent tumors. It has also become increasingly clear that GnRH-R are expressed in cancer tissues, either related (i.e. prostate, breast, endometrial, and ovarian cancers) or unrelated (i.e. melanoma, glioblastoma, lung, and pancreatic cancers) to the reproductive system. In hormone-related tumors, GnRH-R appear to be expressed even when the tumor has escaped steroid dependence (such as castration-resistant prostate cancer). These receptors are coupled to a G(αi)-mediated intracellular signaling pathway. Activation of tumor GnRH-R by means of GnRH agonists elicits a strong antiproliferative, antimetastatic, and antiangiogenic (more recently demonstrated) activity. Interestingly, GnRH antagonists have also been shown to elicit a direct antitumor effect; thus, these compounds behave as antagonists of GnRH-R at the pituitary level and as agonists of the same receptors expressed in tumors. According to the ligand-induced selective-signaling theory, GnRH-R might assume various conformations, endowed with different activities for GnRH analogs and with different intracellular signaling pathways, according to the cell context. Based on these consistent experimental observations, tumor GnRH-R are now considered a very interesting candidate for novel molecular, GnRH analog-based, targeted strategies for the treatment of tumors expressing these receptors. These agents include GnRH agonists and antagonists, GnRH analog-based cytotoxic (i.e. doxorubicin) or nutraceutic (i.e. curcumin) hybrids, and GnRH-R-targeted nanoparticles delivering anticancer compounds.

Targeted chemotherapy of endometrial, ovarian and breast cancers with cytotoxic analogs of luteinizing hormone-releasing hormone (LHRH)

Receptors luteinizing hormone-releasing hormone (LHRH) are expressed in about 80 % of human endometrial and ovarian cancers and account for more than 50 % of breast cancers including triple negative breast cancers. Apart from the pituitary and reproductive organs, no other organs or hematopoietic stem cells express LHRH (GnRH) receptors. Thus, these receptors can be regarded as an ideal target for a personalized medicine approach in cancer therapy. AEZS-108 (formerly known as AN-152) in which doxorubin is linked to the LHRH agonist [D: -Lys(6)]LHRH, appears to be the most advanced compound in late stage clinical development. Results of phase I and phase II clinical trials in patients with gynecological cancers demonstrated anticancer activity without any cardiotoxicity even in highly pretreated patients. AEZS-108 is therefore being considered for phase II trials in triple negative breast cancers and phase III studies in advanced endometrial cancers positive for LHRH-receptor. EP-100 is a membrane-disrupting peptide targeted to LHRH receptors, which is undergoing early clinical studies in ovarian cancer patients.

Synthesis, characterization, and in vivo efficacy evaluation of PGG-docetaxel conjugate for potential cancer chemotherapy

Aim

This work is intended to develop and evaluate a biopolymeric poly(L-γ-glutamylglutamine) (PGG)–docetaxel (DTX) conjugate that can spontaneously self-assemble in aqueous solutions to become nanoparticles.

Methods

DTX was covalently attached to hydrophilic PGG by direct esterification, and the conjugate was characterized by proton nuclear magnetic resonance spectroscopy, molecular weight gel permeation chromatography, solubility, size distribution and morphology, and hemolysis. Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. Dynamic light scattering, transmission electron microscopy, and atomic force microscopy revealed the particle size, distribution and morphology of the PGG–DTX conjugate. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460.

Results

Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. The conjugate formed nanoparticles with an average diameter of 30 nm in spherical shape and unimodal particle size distribution. The conjugate exhibited about 2% hemolysis at 10 mg/mL, compared with 56% for Tween 80^® at 0.4 mg/mL, and 33% for Cremophor EL^® at 10 mg/mL. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460. As expected, conjugated DTX exhibited lower cytotoxicity compared to that of free DTX, in concentration-dependent manner. However, PGG–DTX showed better antitumor activity in NCI-H460 lung cancer-bearing mice with minimal weight loss compared to that of free DTX.

Conclusion

The PGG–DTX conjugate may be considered as an attractive and promising polymeric DTX conjugate for non-small cell lung cancer treatment.

Receptor-targeted nanocarriers for therapeutic delivery to cancer

Efficient and site-specific delivery of therapeutic drugs is a critical challenge in clinical treatment of cancer. Nano-sized carriers such as liposomes, micelles, and polymeric nanoparticles have been investigated for improving bioavailability and pharmacokinetic properties of therapeutics via various mechanisms, for example, the enhanced permeability and retention (EPR) effect. Further improvement can potentially be achieved by conjugation of targeting ligands onto nanocarriers to achieve selective delivery to the tumour cell or the tumour vasculature. Indeed, receptor-targeted nanocarrier delivery has been shown to improve therapeutic responses both in vitro and in vivo. A variety of ligands have been investigated including folate, transferrin, antibodies, peptides and aptamers. Multiple functionalities can be incorporated into the design of nanoparticles, e.g., to enable imaging and triggered intracellular drug release. In this review, we mainly focus on recent advances on the development of targeted nanocarriers and will introduce novel concepts such as multi-targeting and multi-functional nanoparticles.

Luteinizing hormone-releasing hormone receptor-mediated delivery of mitoxantrone using LHRH analogs modified with PEGylated liposomes

A sterically stabilized, mitoxantrone-loaded liposome, tailored to target luteinizing hormone-releasing hormone (LHRH) receptor overexpressing cells, was developed to promote the efficiency of intracellular delivery of mitoxantrone through receptor-mediated endocytosis. Liposomes were prepared by lipid film hydration and an ultrasound dispersion process. Thiolated gonadorelin with affinity for the LHRH receptor was chemically coupled to N-[(3-maleimide-1-oxopropyl) aminopropyl polyethylene glycol-carbamyl] distearoyl-l-phosphatidyl-ethanolamine via a thioether bond and subsequently inserted into polyethylene glycol-grafted liposomes. The liposome was characterized in terms of its size, ligand density, drug loading, and leakage properties. The targeting nature and antitumor effects of the liposomes were evaluated in vitro using cultured MCF-7 breast cancer cells. A protein assay of ligand coupling to the liposomal surface indicated that more than 60% of the LHRH peptides were inserted into the liposome bilayer. Up to 1.0 mg/mL of stable liposomal mitoxantrone loading was achieved, with approximately 98% of this being entrapped within the liposomes. In vitro cell culture studies revealed that the gonadorelin-modified liposomes bound to their target cells had significantly higher affinity and better antitumor efficiency than generic drug-loaded liposomes. These events were presumed to occur through specific interactions of the LHRH with its cognate receptors on the cell surface. It was concluded that the targeting properties of the delivery system would potentially improve the therapeutic benefits of mitoxantrone, as compared with nontargeted liposomes.

Targeted drug and gene delivery systems for lung cancer therapy

PURPOSE

To evaluate the efficacy of a novel docetaxel derivative of deslorelin, a luteinizing hormone-releasing hormone (LHRH) agonist, and its combination in vivo with RGD peptide conjugated nanoparticles encapsulating an antiangiogenic, anti-vascular endothelial growth factor (VEGF) intraceptor (Flt23k; RGD-Flt23k-NP) in H1299 lung cancer cells and/or xenografts in athymic nude BALB/c mice.

EXPERIMENTAL DESIGN

The in vitro and in vivo efficacy of the deslorelin-docetaxel conjugate was evaluated in H1299 cells and xenografts in athymic nude mice. Coadministration of deslorelin-docetaxel conjugate and RGD-Flt23k-NP was tested in vivo in mice. Tumor inhibition, apoptosis, and VEGF inhibition were estimated in each of the treatment groups.

RESULTS

The conjugate enhanced in vitro docetaxel efficacy by 13-fold in H1299 cells compared with docetaxel at 24 hours, and this effect was inhibited following reduction of LHRH receptor expression by an antisense oligonucleotide. Combination of the conjugate with the RGD-Flt23k-NP in vivo resulted in an 82- and 15-fold tumor growth inhibition on day 39 following repeated weekly i.v. injections and a single intratumoral (i.t.) injection, respectively. These effects were significantly greater than individual targeted therapies or docetaxel alone. Similarly, apoptotic indices for the combination therapy were 14% and 10% in the i.v. and i.t. groups, respectively, and higher than the individual therapies. Combination therapy groups exhibited greater VEGF inhibition in both the i.v. and i.t. groups.

CONCLUSIONS

Docetaxel efficacy was enhanced by LHRH receptor-targeted deslorelin conjugate and further improved by combination with targeted antiangiogenic nanoparticle gene therapy. Combination of novel targeted therapeutic approaches described here provides an attractive alternative to the current treatment options for lung cancer therapy.