Paclitaxel–octreotide conjugates in tumor growth inhibition of A549 human non-small cell lung cancer xenografted into nude mice

Nanotechnology-Based Strategy for Enhancing Therapeutic Efficacy in Pancreatic Cancer: Receptor-Targeted Drug Delivery by Somatostatin Analog

A novel nanotechnology-based drug delivery system (DDS) targeted at pancreatic cancer cells was developed, characterized, and tested. The system consisted of liposomes as carriers, an anticancer drug (paclitaxel) as a chemotherapeutic agent, and a modified synthetic somatostatin analog, 5-pentacarbonyl-octreotide, a ligand for somatostatin receptor 2 (SSTR2), as a targeting moiety for pancreatic cancer. The cellular internalization, cytotoxicity, and antitumor activity of the DDS were tested in vitro using human pancreatic ductal adenocarcinoma (PDAC) cells with different expressions of the targeted SSTR2 receptors, and in vivo on immunodeficient mice bearing human PDAC xenografts. The targeted drug delivery system containing paclitaxel exhibited significantly enhanced cytotoxicity compared to non-targeted DDS, and this efficacy was directly related to the levels of SSTR2 expression. It was found that octreotide-targeted DDS proved exceptionally effective in suppressing the growth of PDAC tumors. This study underscores the potential of octreotide-targeted liposomal delivery systems to enhance the therapeutic outcomes for PDAC compared with non-targeted liposomal DDS and Paclitaxel-Cremophor® EL, suggesting a promising avenue for future cancer therapy innovations.

Somatostatin and Somatostatin Receptors in Tumour Biology

Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.

Smart Sensors and Microtechnologies in the Precision Medicine Approach against Lung Cancer

BACKGROUND AND RATIONALE

The therapeutic interventions against lung cancer are currently based on a fully personalized approach to the disease with considerable improvement of patients' outcome. Alongside continuous scientific progresses and research investments, massive technologic efforts, innovative challenges, and consolidated achievements together with research investments are at the bases of the engineering and manufacturing revolution that allows a significant gain in clinical setting.

AIM AND METHODS

The scope of this review is thus to focus, rather than on the biologic traits, on the analysis of the precision sensors and novel generation materials, as semiconductors, which are below the clinical development of personalized diagnosis and treatment. In this perspective, a careful revision and analysis of the state of the art of the literature and experimental knowledge is presented.

RESULTS

Novel materials are being used in the development of personalized diagnosis and treatment for lung cancer. Among them, semiconductors are used to analyze volatile cancer compounds and allow early disease diagnosis. Moreover, they can be used to generate MEMS which have found an application in advanced imaging techniques as well as in drug delivery devices.

CONCLUSIONS

Overall, these issues represent critical issues only partially known and generally underestimated by the clinical community. These novel micro-technology-based biosensing devices, based on the use of molecules at atomic concentrations, are crucial for clinical innovation since they have allowed the recent significant advances in cancer biology deciphering as well as in disease detection and therapy. There is an urgent need to create a stronger dialogue between technologists, basic researchers, and clinicians to address all scientific and manufacturing efforts towards a real improvement in patients' outcome. Here, great attention is focused on their application against lung cancer, from their exploitations in translational research to their application in diagnosis and treatment development, to ensure early diagnosis and better clinical outcomes.

Octreotide and Octreotide-derived delivery systems

Pharmaceutical peptide Octreotide is a somatostatin analog with targeting and therapeutic abilities. Over the last decades, Octreotide has been developed and approved to treat acromegaly and neuroendocrine tumours, and Octreotide-based radioactive conjugates have been leveraged clinically to detect small neuroendocrine tumour sites. Meanwhile, variety of Octreotide-derived delivery strategies have been proposed and explored for tumour targeted therapeutics or diagnostics in preclinical or clinical settings. In this review, we especially focus on the preclinical development and applications of Octreotide-derived drug delivery systems, diagnostic nanosystems, therapeutic nanosystems and multifunctional nanosystems, we also briefly discuss challenges and prospects of these Octreotide-derived delivery systems.

The development of peptide-drug conjugates (PDCs) strategies for paclitaxel

INTRODUCTION

Paclitaxel is a powerful and effective anti-tumor drug with wide clinical application. However, there are still some limitations, including poor water solubility, low specificity, and susceptibility to drug resistance. The peptide-drug conjugates (PDCs) represent a rising class of therapeutic drugs, which combines small-molecule chemotherapeutic drugs with highly flexible peptides through a cleavable or non-cleavable linker. When this strategy is applied, the therapeutic effects of paclitaxel can be improved.

AREAS COVERED

In this review, we discuss the application of the PDCs strategy in paclitaxel, including two parts: the tumor targeting peptide-paclitaxel conjugates and the cell penetrating peptide-paclitaxel conjugates.

EXPERT OPINION

Combining drugs with multifunctional peptides covalently is an effective strategy for delivering paclitaxel to tumors. Depending on different functional peptides, conjugates can increase the water solubility of paclitaxel, tumor permeability of paclitaxel, the accumulation of paclitaxel in tumor tissues, and enhance the antitumor effect of paclitaxel. In addition, due to the change of cell entry mechanism, partial conjugates can restore the therapeutic activity of paclitaxel against resistant tumors. Notably, in order to better translate into the clinical field in the future, more research should be conducted to ensure the safety and effectiveness of peptide-paclitaxel conjugates.

Targeted paclitaxel-octreotide conjugates inhibited the growth of paclitaxel-resistant human non-small cell lung cancer A549 cells in vitro

The application of chemotherapy in non‐small cell lung cancer (NSCLC) is limited by the toxicity to normal cells and the development of multi‐drug resistance. Targeted chemotherapy using cytotoxic analogs against specific receptors on cancer cells could be a less toxic and more efficacious approach. We identified that the expressions of somatostatin receptor (SSTR) 2 and 5 in tumor tissues from NSCLC patients were higher than those in the adjacent normal tissues by immunohistochemistry, and therefore, cytotoxic somatostatin analogues might be applied for SSTRs‐mediated targeted therapy against NSCLC. Two cytotoxic analogs, paclitaxel‐octreotide (PTX‐OCT) and 2paclitaxel‐octreotide (2PTX‐OCT), were synthesized by linking one or two molecules of paclitaxel to one molecule of somatostatin analog octreotide. PTX‐OCT and 2PTX‐OCT significantly inhibited the growth and induced apoptosis of SSTR2‐ and SSTR5‐positive A549 cells, compared with the control (p < 0.01), and had less inhibitory effect on SSTR2‐ and SSTR5‐negative H157 cells than paclitaxel (p < 0.01). Moreover, compared with paclitaxel, PTX‐OCT conjugates induced lower expression of MDR‐1 gene both in vitro and in vivo. Three A549 paclitaxel‐resistant cell lines were established through different approaches, and the paclitaxel‐resistant cell showed higher sensitivity to PTX‐OCT conjugates than to paclitaxel, which might be because of the differential MDR‐related gene expressions and cell‐cycle distribution in paclitaxel‐resistant A549 cells. Our results suggested that PTX‐OCT conjugates could be potentially used for SSTRs‐mediated targeted therapy for NSCLC, especially for those with paclitaxel resistance and induced less multidrug resistance.

Peptide-Drug Conjugates and Their Targets in Advanced Cancer Therapies

Cancer became recently the leading cause of death in industrialized countries. Even though standard treatments achieve significant effects in growth inhibition and tumor elimination, they cause severe side effects as most of the applied drugs exhibit only minor selectivity for the malignant tissue. Hence, specific addressing of tumor cells without affecting healthy tissue is currently a major desire in cancer therapy. Cell surface receptors, which bind peptides are frequently overexpressed on cancer cells and can therefore be considered as promising targets for selective tumor therapy. In this review, the benefits of peptides as tumor homing agents are presented and an overview of the most commonly addressed peptide receptors is given. A special focus was set on the bombesin receptor family and the neuropeptide Y receptor family. In the second part, the specific requirements of peptide-drug conjugates (PDC) and intelligent linker structures as an essential component of PDC are outlined. Furthermore, different drug cargos are presented including classical and recent toxic agents as well as radionuclides for diagnostic and therapeutic approaches. In the last part, boron neutron capture therapy as advanced targeted cancer therapy is introduced and past and recent developments are reviewed.

Small-molecule compounds target paraptosis to improve cancer therapy

According to its different occurrence mechanism, programmed cell death (PCD) is divided into apoptosis, autophagy, necrosis, paraptosis and so on. Paraptosis is morphologically different from apoptosis and autophagy, which exhibit cytoplasmic vacuolation derived from the ER, independent of caspase, absence of apoptotic morphology. Recent researches have implied that a variety of small molecule compounds, such as celastrol, curcumin, can induce paraptosis-associated cell death as the reagent to enhance anti-cancer activity. A better understanding of paraptosis will lay the foundation to develop new therapeutic strategies to treat human cancers that make full use of small-molecule compounds.

The nuclear export inhibitor aminoratjadone is a potent effector in extracellular-targeted drug conjugates

The concept of targeted drug conjugates has been successfully translated to clinical practice in oncology. Whereas the majority of cytotoxic effectors in drug conjugates are directed against either DNA or tubulin, our study aimed to validate nuclear export inhibition as a novel effector principle in drug conjugates. For this purpose, a semisynthetic route starting from the natural product ratjadone A, a potent nuclear export inhibitor, has been developed. The biological evaluation of ratjadones functionalized at the 16-position revealed that oxo- and amino-analogues had very high potencies against cancer cell lines (e.g. 16R-aminoratjadone 16 with IC50 = 260 pM against MCF-7 cells, or 19-oxoratjadone 14 with IC50 = 100 pM against A-549 cells). Mechanistically, the conjugates retained a nuclear export inhibitory activity through binding CRM1. To demonstrate a proof-of-principle for cellular targeting, folate- and luteinizing hormone releasing hormone (LHRH)-based carrier molecules were synthesized and coupled to aminoratjadones as well as fluorescein for cellular efficacy and imaging studies, respectively. The Trojan-Horse conjugates selectively addressed receptor-positive cell lines and were highly potent inhibitors of their proliferation. For example, the folate conjugate FA-7-Val-Cit-pABA-16R-aminoratjadone had an IC50 of 34.3 nM, and the LHRH conjugate d-Orn-Gose-Val-Cit-pABA-16R-aminoratjadone had an IC50 of 12.8 nM. The results demonstrate that nuclear export inhibition is a promising mode-of-action for extracellular-targeted drug conjugate payloads.

Peptide ligand-mediated targeted drug delivery of nanomedicines

Targeted drug delivery is emerging as a promising strategy to achieve better clinical outcomes. Actively targeted drug delivery that utilizes overexpressed receptors or antigens on diseased tissues is receiving increasing scrutiny, especially due to the uncertainty of existence of the enhanced permeability and retention (EPR) effect in cancer patients. Peptide ligands are advantageous over other classes of targeting ligands due to their accessibility of high-throughput screening, ease of synthesis, high specificity and affinity, etc. In this review, we briefly summarize the resources of peptide ligands and discuss the pitfalls and perspectives of peptide ligand-mediated targeted delivery of nanomedicines.

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.

Exploiting cancer's phenotypic guise against itself: targeting ectopically expressed peptide G-protein coupled receptors for lung cancer therapy

Lung cancer, claiming millions of lives annually, has the highest mortality rate worldwide. This advocates the development of novel cancer therapies that are highly toxic for cancer cells but negligibly toxic for healthy cells. One of the effective treatments is targeting overexpressed surface receptors of cancer cells with receptor-specific drugs. The receptors-in-focus in the current review are the G-protein coupled receptors (GPCRs), which are often overexpressed in various types of tumors. The peptide subfamily of GPCRs is the pivot of the current article owing to the high affinity and specificity to and of their cognate peptide ligands, and the proven efficacy of peptide-based therapeutics. The article summarizes various ectopically expressed peptide GPCRs in lung cancer, namely, Cholecystokinin-B/Gastrin receptor, the Bombesin receptor family, Bradykinin B1 and B2 receptors, Arginine vasopressin receptors 1a, 1b and 2, and the Somatostatin receptor type 2. The autocrine growth and pro-proliferative pathways they mediate, and the distinct tumor-inhibitory effects of somatostatin receptors are then discussed. The next section covers how these pathways may be influenced or 'corrected' through therapeutics (involving agonists and antagonists) targeting the overexpressed peptide GPCRs. The review proceeds on to Nano-scaled delivery platforms, which enclose chemotherapeutic agents and are decorated with peptide ligands on their external surface, as an effective means of targeting cancer cells. We conclude that targeting these overexpressed peptide GPCRs is potentially evolving as a highly promising form of lung cancer therapy.

Lycorine possesses notable anticancer potentials in on-small cell lung carcinoma cells via blocking Wnt/β-catenin signaling and epithelial-mesenchymal transition (EMT)

Lycorine, an natural isoquinoline alkaloid has reportedly that possesses multi-anticancer activity. However, to date, the anticancer feature of lycorine in non-small cell lung carcinoma (NSCLC) has still not fully been spelled out. The present study mainly focused on the molecular mechanism of lycorine against NSCLC in vitro and vivo. The results showed that lycorine evidently inhibited proliferation of A549 and H460 with IC₅₀ values were 10.83 ± 1.14 μM and 12.35 ± 1.13 μM, while caused slight cytotoxicity in normal pulmonary epithelial Beas-2B cells, and arrested cell cycle in G0/G1 phase. Hoechst DNA-binding staining showed that typical characteristics of nuclear morphology apoptosis, AnnexinV-FITC/PI staining revealed the early-period apoptosis and the dissipation of mitochondrial membrane potential (Δψm) were also captured after lycorine treatment. Moreover, lycorine effectively repressed the Wnt/β-catenin signaling and reversed epithelial-mesenchymal transition (EMT). In addition, lycorine also intervened the caspase-mediated mitochondrial apoptosis pathway. Furthermore, A549/Luc tumor xenograft model was also corroborated that lycorine significantly suppressed the growth and metastasis of the lung tumor. These data highlight the significance of lycorine as potential anti-neoplastic agents to combat NSCLC.

Somatostatin receptor targeted liposomes with Diacerein inhibit IL-6 for breast cancer therapy

Selective targeting to the tumor niche remains a major challenge in successful cancer therapy. Somatostatin receptor 2 (SSTR2) is overexpressed in breast cancer cells thus making this receptor an attractive target for selective guidance of ligand-conjugated drug liposomes to the tumor site. In this study, a synthetic somatostatin analogue (SST) was used as SSTR2 targeting agent and Diacerein was employed as therapeutic molecule. Diacerein loaded liposomes (DNL) were prepared and they were further decorated with the synthetic and stable analogue of somatostatin (SST-DNL). Fabricated liposomes were nano-size in range and biocompatible. SST-DNL displayed significantly better anti-tumor efficacy as compared to free Diacerein (DN) and DNL in breast cancer models. Enhanced apoptosis in breast cancer cells was detected in SST-DNL treated groups as monitored by cell cycle analysis and changes in expression level of apoptotic/anti-apoptotic proteins Bcl-2, Bax, cleaved Caspase 3 and PARP. SST-DNL more effectively inhibited the oncogenic IL-6/IL-6R/STAT3/MAPK/Akt signalling pathways as compared to DN or DNL in cancer cells. In addition, SST-DNL effectively suppressed angiogenesis and cancer cell invasion. In vivo tumor growth in a MDA-MB-231 mouse xenograft model was significantly suppressed following SST-DNL treatment. In xenograft model, immunohistochemistry of Ki-67 and CD-31 indicated that SST-DNL improved the anti-proliferative and anti-angiogenic impacts of Diacerein. In vivo pharmacokinetic studies in rats showed enhanced circulation time in the DNL or SST-DNL treated groups as compared to free DN. Considering all of these findings, we conclude that SST-DNL provides a novel strategy with better efficacy for breast cancer therapy.

Synthetic paclitaxel-octreotide conjugate reverses the resistance of paclitaxel in A2780/Taxol ovarian cancer cell line

The high mortality of ovarian cancer is partly due to the frequent resistance of ovarian cancer to current chemotherapy agents such as paclitaxel and platinum. Somatostatin analogue (SSTA) has been shown to inhibit the proliferation of some tumors through binding to somatostatin receptor (SSTR) and activation of Ras-, Rapl- and B-Raf-dependent extracellular signal-regulated kinase 2 (Erk2). It was reported that paclitaxel-octreotide conjugate (POC) exhibited enhanced tumor growth inhibition with reduced toxicity. In the present study, we prepared the POC and investigated its effects and mechanism for the reversal of drug resistance in paclitaxel-resistant ovarian cancer cell line. We demonstrated that treatment with POC led to more cell apoptosis than either paclitaxel or octreotide (OCT) alone. Moreover, the expression of multidrug resistance 1 (MDR1) and vascular endothelial growth factor (VEGF) mRNA, and protein decreased in a dose-dependent manner while the expression of SSTR remained stable following treatment with POC. Although the exact action, in vivo effects and pharmacologic kinetics of POC remain to be investigated, we have demonstrated the feasibility for the synthesis of POC, and more significantly, provided a potential approach to overcome the resistance of ovarian cancer against taxol. The findings also shed some new light on the mechanisms underlying the development of resistance to taxol by ovarian cancer cells.

Receptor selective ruthenium-somatostatin photosensitizer for cancer targeted photodynamic applications

The efficient conjugation of a ruthenium complex and the peptide hormone somatostatin is presented. The resultant biohybrid offers valuable features for photodynamic therapy such as remarkable cellular selectivity, rapid cell uptake by receptor-mediated endocytosis, efficient generation of (1)O2 upon irradiation, potent phototoxicity as well as low cytotoxicity in the "off"-state.

Tumor targeted delivery of octreotide-periplogenin conjugate: Synthesis, in vitro and in vivo evaluation

Periplogenin (PPG), a cardiac glycoside prepared from Cortex periplocae, with similar structure to bufalin, has been found to induce apoptosis in many tumor cells. However, lots of cardiac glycosides possessing strong antitumor activity in vitro have still not passed phase I clinical trials, mostly due to poor tumor selectivity and systemic toxicity. To overcome this drawback, we designed octreotide-periplogenin (OCT-PPG) conjugate by coupling PPG-succinate to the amino-terminal end of octreotide. In comparison with free PPG, the conjugate exhibited significantly stronger cytotoxicity on HepG2 cells (SSTRs overexpression) but much less toxicity in L-02 cells. After intravenous injection of OCT-PPG conjugate into H22 tumor-bearing mice, its total accumulation in tumor was 2.3 fold higher than that of free PPG, but was 0.71- and 0.84-fold lower in heart and liver, respectively, suggesting somatostatin-mediated target delivery of PPG into the tumor tissue and reduced distribution in heart and liver. In vivo studies using H22 tumor model in mice confirmed the remarkable therapeutic effect of this conjugate. These results suggested that OCT-PPG conjugate could provide a new approach for clinical application of cardiac glycosides and as a targeting agent for cancer therapy.

Drug delivery and release systems for targeted tumor therapy

Most toxic agents currently used for chemotherapy show a narrow therapeutic window, because of their inability to distinguish between healthy and cancer cells. Targeted drug delivery offers the possibility to overcome this issue by selectively addressing structures on the surface of cancer cells, therefore reducing undesired side effects. In this broad field, peptide-drug conjugates linked by intracellular cleavable structures have evolved as highly promising agents. They can specifically deliver toxophores to tumor cells by targeting distinct receptors overexpressed in cancer. In this review, we focus on these compounds and describe important factors to develop a highly efficient peptide-drug conjugate. The necessary properties of tumor-targeting peptides are described, and the different options for cleavable linkers used to connect toxic agents and peptides are discussed, and synthetic considerations for the introduction of these structures are reported. Furthermore, recent examples and current developments of peptide-drug conjugates are critically evaluated with a special focus on the applied linker structures and their future use in cancer therapy.

Lanreotide-conjugated PEG-DSPE micelles: an efficient nanocarrier targeting to somatostatin receptor positive tumors

Lanreotide is an octapeptide analog of endogenous somatostatin, specifically binding with tumors over-express somatostatin receptor 2 (SSTR2). In this study, we conjugated lanreotide to 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (poly-(ethylene glycol))-2000] (PEG-DSPE), constructed active targeted micelles (lanreotide-PM), characterized their in vitro and in vivo targeting effect, and explored the receptor mediated transportion. The uptake of lanreotide-PM was found to be related to the expression level of SSTR2 in different cell lines and the competitive inhibition phenomenon indicated that the cellular uptake of lanreotide-PM was via a receptor meditated mechanism. In vivo, more lanreotide-PM accumulated in SSTR2 high expression tumor xenografts, endocytosed by the tumor cells, induced more apoptosis of tumor cells, and suppressed tumor growth efficiently. In conclusion, lanreotide-modified micelles containing antitumor drugs provide a promising strategy for the treatment of SSTR-expressing tumors.

Nanoparticle ligand presentation for targeting solid tumors

Among the many scientific advances to come from the study of nanoscience, the development of ligand-targeted nanoparticles to eliminate solid tumors is predicted to have a major impact on human health. There are many reports describing novel designs and testing of targeted nanoparticles to treat cancer. While the principles of the technology are well demonstrated in controlled lab experiments, there are still many hurdles to overcome for the science to mature into truly efficacious targeted nanoparticles that join the arsenal of agents currently used to treat cancer in humans. One of these hurdles is overcoming unwanted biodistribution to the liver while maximizing delivery to the tumor. This almost certainly requires advances in both nanoparticle stealth technology and targeting. Currently, it continues to be a challenge to control the loading of ligands onto polyethylene glycol (PEG) to achieve maximal targeting. Nanoparticle cellular uptake and subcellular targeting of genes and siRNA also remain a challenge. This review examines the types of ligands that have been most often used to target nanoparticles to solid tumors. As the science matures over the coming decade, careful control over ligand presentation on nanoparticles of precise size, shape, and charge will likely play a major role in achieving success.

Comparison of active and passive targeting of doxorubicin for somatostatin receptor 2 positive tumor models by octreotide-modified HPMA copolymer-doxorubicin conjugates

Somatostatin receptor 2 (SSTR2), specifically over-expressed on many tumor cells, is a potential receipt for active targeting in cancer therapy. In the present study, octreotide (Oct), which had high affinity to SSTR2, was attached to N-(2-hydroxypropyl) methacrylamide (HPMA) polymeric system to enhance the antitumor efficiency of the anticancer drug doxorubicin (DOX). Two kinds of cell lines (HepG2 and A549), which overexpress SSTR2, were chosen as cell models. Compared with non-modified conjugates, Oct-modified conjugates exhibited superior cytotoxicity and intracellular uptake on both HepG2 and A549 cell lines. This might be due to the mechanism of receptor-mediated endocytosis. Subsequently, the in vivo biodistribution and antitumor activity evaluations showed that Oct modification significantly improved the tumor accumulation and antitumor efficacy of HPMA copolymer conjugates in SSTR2 over-expressed Kunming mice bearing H22 tumor xenografts. In summary, Oct-modified HPMA polymer-DOX conjugates might be a promising system for the treatment of SSTR2 over-expressed cancers.

Toxins from the Caribbean sea anemone Bunodeopsis globulifera increase cisplatin-induced cytotoxicity of lung adenocarcinoma cells

Background

Lung cancer causes 1.4 million deaths worldwide while non-small-cell lung cancer (NSCLC) represents 80-85% of the cases. Cisplatin is a standard chemotherapy against this type of cancer; however, tumor cell resistance to this drug limits its efficacy. Sea anemones produce compounds with pharmacological activities that may be useful for augmenting cisplatin efficacy. This study aimed to evaluate the pharmacological activities of crude venom (CV) from the sea anemone Bunodeopsis globulifera and four derived fractions (F1, F2, F3 and F4) to test their increase efficiency cisplatin cytotoxicity in human lung adenocarcinoma cells.

Results

Pre-exposure to CV, F1 and F2 fractions increases cisplatin cytotoxicity in human lung adenocarcinoma cells under specific conditions. Exposure to CV at 50 μgmL^-1 induced a reduction of approximately 50% in cell viability, while a similar cytotoxic effect was observed when cell culture was exposed to F1 at 25 μgmL ^-1 or F2 at 50 μgmL^-1. The cell culture exposure to F1 (10 μgmL^-1) fraction combined with cisplatine (25 μM) provoked a decrease in MTT reduction until 65.57% while F2 (25 μgmL^-1) fraction combined with cisplatin (10 μM) provoked a decrease in MTT reduction of 72.55%.

Conclusions

The F1 fraction had the greatest effect on the lung adenocarcinoma cell line compared with CV and F2. The combination of antineoplastic drugs and sea anemone toxins might allow a reduction of chemotherapeutic doses and thus mitigate side effects.

Characterization of PEG-iron oxide hydrogel nanocomposites for dual hyperthermia and paclitaxel delivery

Hyperthermia, the heating of tissue from 41 to 45 °C, has been shown to improve the efficacy of cancer therapy when used in conjunction with irradiation and/or chemotherapy. In this work, hydrogel nanocomposites have been developed that can control the delivery of both heat and a chemotherapeutic agent (e.g. paclitaxel). The nanocomposites studied involve a stealth, poly(ethylene glycol) (PEG)-based system comprised of PEG (n = 1000) methyl ether methacrylate and PEG (n = 400) dimethacrylate with iron oxide nanoparticles physically entrapped within the hydrogel matrices. The capability of the hydrogel nanocomposites to be heated in an alternating magnetic field was demonstrated. The heating of the hydrogel systems was dependent on the crosslinking of the hydrogel network where hydrogels with lower swelling ratios were found to heat to a greater extent than those with higher ratios. In addition, paclitaxel was shown to exhibit non-Fickian release from the hydrogel systems, with the amount of drug released dependent on the hydrogel network structure. Three cell lines: M059K (glioblastoma), MDA MB 231 (breast carcinoma), and A549 (lung adenocarcinoma) were exposed to paclitaxel only, hyperthermia only, and both paclitaxel and hyperthermia to determine if a synergistic cytotoxic effect was possible for these cell lines. The efficacy of paclitaxel was greater with hyperthermia for the A549 cells; however, the M059K and MDA MB 231 did not show the same response.

Targeting the transposase domain of the DNA repair component Metnase to enhance chemotherapy

Previous studies have shown that the DNA repair component Metnase (SETMAR) mediates resistance to DNA damaging cancer chemotherapy. Metnase has a nuclease domain that shares homology with the Transposase family. We therefore virtually screened the tertiary Metnase structure against the 550,000 compound ChemDiv library to identify small molecules that might dock in the active site of the transposase nuclease domain of Metnase. We identified eight compounds as possible Metnase inhibitors. Interestingly, among these candidate inhibitors were quinolone antibiotics and HIV integrase inhibitors, which share common structural features. Previous reports have described possible activity of quinolones as antineoplastic agents. Therefore, we chose the quinolone ciprofloxacin for further study, based on its wide clinical availability and low toxicity. We found that ciprofloxacin inhibits the ability of Metnase to cleave DNA and inhibits Metnase-dependent DNA repair. Ciprofloxacin on its own did not induce DNA damage, but it did reduce repair of chemotherapy-induced DNA damage. Ciprofloxacin increased the sensitivity of cancer cell lines and a xenograft tumor model to clinically relevant chemotherapy. These studies provide a mechanism for the previously postulated antineoplastic activity of quinolones, and suggest that ciprofloxacin might be a simple yet effective adjunct to cancer chemotherapy.

Hyaluronic acid-paclitaxel conjugate inhibits growth of human squamous cell carcinomas of the head and neck via a hyaluronic acid-mediated mechanism

Chemotherapeutic regimens incorporating taxanes significantly improve outcomes for patients with squamous cell carcinomas of the head and neck (SCCHN). However, treatment with taxanes is limited by toxicities, including bone marrow suppression and peripheral neuropathies. We proposed that conjugating taxanes to targeting carrier molecules would increase antitumor efficacy and decrease toxicity. The cell surface proteoglycan, CD44, is expressed on most SCCHNs, and we hypothesized that it is an attractive candidate for targeted therapy via its natural ligand, hyaluronic acid (HA). We determined whether HA-paclitaxel conjugates were able to decrease tumor growth and improve survival in orthotopic nude mouse human SCCHN xenograft models. HA-paclitaxel concentration-dependent growth inhibition of human SCCHN cell lines OSC-19 and HN5 in vitro, very similarly to free paclitaxel treatment. Tumor cell uptake of FITC-labeled HA-paclitaxel was significantly blocked with free HA, indicating the dependence of uptake on CD44. HA-paclitaxel administered intravenously once per week for three weeks at 120 mg/kg paclitaxel equivalents, far above the paclitaxel maximum tolerated dose, exerted superior tumor growth control to that of paclitaxel in both orthotopic OSC-19-luciferase and HN5 xenograft models in vivo. Mouse survival following HA-paclitaxel administration was prolonged compared with that of controls in mice implanted with either of these xenografts. Mice treated with HA-paclitaxel displayed increased TUNEL(+) cells in tumor tissue, as well as markedly reduced microvessel density compared to those treated with free paclitaxel. No acute histopathological changes were observed in mice treated with HA-paclitaxel. Thus, we conclude that HA-paclitaxel effectively inhibits tumor growth in human SCCHN xenografts via an HA-mediated mechanism and this conjugate should be considered for further preclinical development for this disease.

Effect of octreotide-polyethylene glycol(100) monostearate modification on the pharmacokinetics and cellular uptake of nanostructured lipid carrier loaded with hydroxycamptothecine

A new conjugate, octreotide-polyethylene glycol(100) monostearate (OPMS), was developed for the enhancement of targeting delivery of hydroxycamptothecine (HCPT) loaded in nanostructured lipid carrier (NLC). 2 × 10(-3) and 5 × 10(-3) mmol of OPMS were respectively used to modify NLC so that the targeted nanocarriers with low and high ligand density were obtained. For comparison, the pegylated NLCs without octreotide were prepared by adding equal molar amounts of polyethylene glycol(100) monostearate (PGMS). The relation between the modification levels and properties of various NLCs were studied in vivo and in vitro. At a high modification level, a slower release rate of HCPT and the more stable nanocarriers was achieved. At the same time, the fixed aqueous layer thickness (FALT) and average surface density of PEG chains (SD(PEG)) was increased, but the distance (D) between two neighboring PEG grafting sites became narrower. The in vivo pharmacokinetic study in healthy rat indicated that the modified NLCs had a longer circulation than NLC (P < 0.05) due to pegylation effect and OPMS modified NLCs had larger MRT and AUC(0-t) than that of PGMS modified NLCs at the same modification level. Furthermore, the florescence microscopy observation also showed the targeting effect of octreotide modification on somatostatin receptors (SSTRs) of tumor cell (SMMC-7721). The uptake of SMMC-7721 was much more than that of normal liver cell (L02) for OPMS modified NLC, and the highest uptake was observed for 5 × 10(-3) mmol of OPMS modified one. No obvious difference was found among the L02 uptake of OPMS modified NLCs and NLC, but their uptake was higher than that of PGMS modified NLCs. All the results indicated that the OPMS highly modified NLCs would improve the effect of antitumor therapy by inhibiting the degradation, evading RES and enhancing the drug uptake of tumor cells.

A novel octreotide modified lipid vesicle improved the anticancer efficacy of doxorubicin in somatostatin receptor 2 positive tumor models

Octreotide (Oct) is a potential ligand due to its high affinity to somatostatin receptors (SSTRs), especially subtype 2 (SSTR2), as many tumor cells specifically overexpress SSTR2. In this study, we conjugated Oct to the PEG end of DSPE-PEG and prepared a novel doxorubicin (DOX)-loaded and Oct-modified sterically stabilized liposomes (Oct-SSL-DOX), in order to facilitate intracellular delivery of chemotherapeutic agent to the related tumor cells through active targeting and finally improve its antitumor activity. Three cells were proved to be different in expression level of SSTR2 and were used as model or control. It was demonstrated by fluorescence spectrophotometry, confocal laser scanning microscopy and flow cytometry that active sterically stabilized liposomes (SSL) increased intracellular delivery of DOX in SSTR2-positive cells, through a mechanism of receptor-mediated endocytosis. Compared to SSL, Oct modification on SSL exhibited little effect on the physicochemical properties of SSL. However, it reduced the circulation time of loaded-DOX to some extent in rats, increased cytotoxicity in SSTR2-positive tumor cells, enhanced drug accumulation in tumor tissue and improved anticancer efficacy in SSTR2-overexpressing tumor model. The correlation was found among intracellular uptake, cytotoxicity, drug distribution in tumor and pharmacodynamics of Oct-SSL-DOX, but not the pharmacokinetics based on plasma drug concentration. In summary, octreotide-modified SSL might be a promising system for the treatment of SSTR2-overexpressing cancers.

Receptor-mediated tumor targeting based on peptide hormones

IMPORTANCE OF THE FIELD

Tumor targeting with peptides is based on the discovery that receptors for many regulatory peptides are overexpressed in tumor cells, compared with their expression in normal tissues. Consequently, these peptides and their analogues can be used as carriers/targeting moieties for the preparation of diagnostic and therapeutic agents that have increased selectivity and decreased peripheral toxicity.

AREAS COVERED IN THIS REVIEW

Here an overview is given of the most relevant gonadotropin-releasing hormone (GnRH) and somatostatin derivatives, as well as of their applications in cancer diagnosis and therapy. For this purpose, recently published data in these areas (mostly articles published from 2000 to 2009) were reviewed.

WHAT THE READER WILL GAIN

In contrast to other regulatory peptides that stimulate the tumor growth, GnRH and somatostatin derivatives have inhibitory effect; therefore, they were used primarily for the preparation of various conjugates to be used in targeted chemotherapy, targeted radiotherapy, photodynamic therapy, boron neutron capture therapy and cancer diagnosis. Some of these conjugates have already found clinical applications, whereas others are now in preclinical and clinical trials.

TAKE HOME MESSAGE

Tumor targeting with hormone peptides provides a basis for the development of new diagnostic and therapeutic approaches for cancer.

Surface activation and targeting strategies of superparamagnetic iron oxide nanoparticles in cancer-oriented diagnosis and therapy

The advanced fabrication and surface engineering of superparamagnetic iron oxide nanoparticles (SPIONs) could offer excellent physiochemical features for noninvasive tumor imaging and drug delivery. The key issues of realization of maximized selective cancer targeting of SPIONs are minimization of uptake by macrophages, preferential binding to cancerous cells over neighboring normal cells, visualization of tumor cells prior to and after treatment and triggered drug release into target cells in a controlled fashion. In this article, we summarize the current status of fabrication of multifunctional SPION-based nanodevices specially designed for cancer-oriented diagnosis and therapy, with a focus on potential malignancy-targeting ligands’ identification and development as nanocarriers. A number of examples of passive and active targeting strategies – lymphoangiogenesis markers, cellular metabolite receptors, extracellular matrix component receptors, neuropeptide receptors and receptor-mediated bypass of the blood–brain barrier – are described in detail.