VIP-targeted Cytotoxic Nanomedicine for Breast Cancer

Revisiting the roles of cAMP signalling in the progression of prostate cancer

Prostate cancer is one of the most common cancers in men and one of the top causes of death in men worldwide. Development and function of both normal prostate cells and early-stage prostate cancer cells are dependent on the cross-talk between androgen signalling systems and a variety of other transduction pathways which drive differentiation of these cells towards castration-resistance. One such signalling pathway is the ubiquitous cAMP signalling axis which functions to activate spatially restricted pools of cAMP effectors such as protein kinase A (PKA). The importance of both PKA and cAMP in the development of prostate cancer, and their interactions with the androgen receptor, were the focus of a review by Merkle and Hoffmann in 2010. In this updated review, we revisit this topic with analysis of current PKA-related prostate cancer literature and introduce novel information on the relevance of another cAMP effector, the exchange protein directly activated by cAMP (EPAC).

Lipid-Based Nanocarrier Systems for Drug Delivery: Advances and Applications

Lipid-based nanocarriers have been extensively investigated for drug delivery due to their advantages including biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity. However, the shortcomings of traditional lipid-based nanocarriers such as insufficient targeting, capture by the reticuloendothelial system, and fast elimination limit the efficiency of drug delivery and therapeutic efficacy. Therefore, a series of multifunctional lipid-based nanocarriers have been developed to enhance the accumulation of drugs in the lesion site, aiming for improved diagnosis and treatment of various diseases. In this review, we summarized the advances and applications of lipid-based nanocarriers from traditional to novel functional lipid preparations, including liposomes, stimuli-responsive lipid-based nanocarriers, ionizable lipid nanoparticles, lipid hybrid nanocarriers, as well as biomembrane-camouflaged nanoparticles, and further discussed the challenges and prospects of this system. This exploration may give a complete idea viewing the lipid-based nanocarriers as a promising choice for drug delivery system, and fuel the advancement of pharmaceutical products by materials innovation and nanotechnology.

Receptor-Mediated Targeted Delivery of Surface-ModifiedNanomedicine in Breast Cancer: Recent Update and Challenges

Breast cancer therapeutic intervention continues to be ambiguous owing to the lack of strategies for targeted transport and receptor-mediated uptake of drugs by cancer cells. In addition to this, sporadic tumor microenvironment, prominent restrictions with conventional chemotherapy, and multidrug-resistant mechanisms of breast cancer cells possess a big challenge to even otherwise optimal and efficacious breast cancer treatment strategies. Surface-modified nanomedicines can expedite the cellular uptake and delivery of drug-loaded nanoparticulate constructs through binding with specific receptors overexpressed aberrantly on the tumor cell. The present review elucidates the interesting yet challenging concept of targeted delivery approaches by exploiting different types of nanoparticulate systems with multiple targeting ligands to target overexpressed receptors of breast cancer cells. The therapeutic efficacy of these novel approaches in preclinical models is also comprehensively discussed in this review. It is concluded from critical analysis of related literature that insight into the translational gap between laboratories and clinical settings would provide the possible future directions to plug the loopholes in the process of development of these receptor-targeted nanomedicines for the treatment of breast cancer.

The past, present, and future of breast cancer models for nanomedicine development

Even given recent advances in nanomedicine development of breast cancer treatment in recent years and promising results in pre-clinical models, cancer nanomedicines often fail at the clinical trial stage. Limitations of conventional in vitro models include the lack of representation of the stromal population, the absence of a three-dimensional (3D) structure, and a poor representation of inter-tumor and intra-tumor heterogeneity. Herein, we review those cell culture strategies that aim to overcome these limitations, including cell co-cultures, advanced 3D cell cultures, patient-derived cells, bioprinting, and microfluidics systems. The in vivo evaluation of nanomedicines must consider critical parameters that include the enhanced permeability and retention effect, the host's immune status, and the site of tumor implantation. Here, we critically discuss the advantages and limitations of current in vivo models and report how the improved selection and application of breast cancer models can improve the clinical translation of nanomedicines.

Targeting breast cancer using pirarubicin-loaded vasoactive intestinal peptide grafted sterically stabilized micelles

In this study the chemotherapeutic agent Pirarubicin (PRB) which is known for its serious side effects was actively targeted to the breast cancer cells by uploading it to the biocompatible and biodegradable Sterically Stabilized Micelles (SSMs) made of 1,2- Distearoyl- sn- glycero‑3- phosphoethanolamine- N- methoxy‑ polyethylene glycol 2000 (DSPE-PEG₂₀₀₀) to enhance efficacy and reduce toxicity. Vasoactive intestinal peptide (VIP), the receptors of which are overexpressed on the breast cancer cells, was grafted on the surface of the micelles. To the best of our knowledge this is the first report on active targeting of PRB to tumor site. For this purpose, PRB loaded VIP grafted SSMs (PRB-SSM-VIP) were synthesized and characterized. The in vitro efficiency of PRB-SSM-VIP along with SSM and free PRB was investigated on the MCF-7 breast cancer cells and the in vivo effects were studied on the 4T1 breast cancer bearing nude mice. Solubilizing 300 µg of PRB using 2.81 mg of DSPE-PEG₂₀₀₀ resulted in obtaining monodispersed particles of 12.16 ± 2.7 nm with slow drug release profile. Incorporation of PRB within the hydrophobic DSPE core of SSM was confirmed using differential scanning calorimetry (DSC) and the spherical shape of the synthesized particles was demonstrated using atomic force microscope (AFM). Both in vitro and in vivo studies showed significantly higher activity of PRB-SSM-VIP compared to free PRB. In vivo imaging showed successful accumulation of PRB-SSM-VIP at the tumor site and 98.8% tumor eradication was obtained with no signs of side effects. Current study suggests that SSM-VIP could be used as new drug delivery system for targeting PRB to the breast cancer cells.

Computational studies of micellar and nanoparticle nanomedicines

The review highlights recent computational modeling of micellar and nanoparticle nanomedicines, which elucidates their functional roles in atomistic details.

Expression and localization of VPAC1, the major receptor of vasoactive intestinal peptide along the length of the intestine

Vasoactive intestinal peptide (VIP) is an endogenous neuropeptide with a broad array of physiological functions in many organs including the intestine. Its actions are mediated via G protein-coupled receptors, and vasoactive intestinal peptide receptor 1 (VPAC1) is the key receptor responsible for majority of VIP's biological activity. The distribution of VPAC1 along the length of the gastrointestinal tract and its subcellular localization in intestinal epithelial cells have not been fully characterized. The current studies were undertaken to determine VPAC1 distribution and localization so that VIP-based therapies can be targeted to specific regions of the intestine. The results indicated that the mRNA levels of VPAC1 showed an abundance pattern of colon > ileum > jejunum in the mouse intestine. In parallel, the VPAC1 protein levels were higher in the mouse colon, followed by the ileum and jejunum. Immunofluorescence studies in mouse colon demonstrated that the receptor was specifically localized to the luminal surface, as was evident by colocalization with the apical marker villin but not with the basolateral marker Na+/K+-ATPase. In the human intestine, VPAC1 mRNA expression exhibited a distribution similar to that in mouse intestine and was highest in the sigmoid colon. Furthermore, in the human colon, VPAC1 also showed predominantly apical localization. The physiological relevance of the expression and apical localization of VPAC1 remains elusive. We speculate that apical VPAC1 in intestinal epithelial cells may have relevance in recognizing secreted peptides in the intestinal lumen and therefore supports the feasibility of potential therapeutic and targeting use of VIP formulations via oral route to treat gastrointestinal diseases.NEW & NOTEWORTHY These studies for the first time present comprehensive data on the relative characterization of vasoactive intestinal peptide (VIP) receptors in the intestinal mucosa. Vasoactive intestinal peptide receptor 1 (VPAC1) was identified as the predominant receptor with higher levels in the colon compared with the small intestine and was mainly localized to the apical membrane. In addition, the findings in the human tissues were consistent with VPAC1 expression in the mouse intestine and open possibilities to target colonic tissues with VIP for treating diseases such as inflammatory bowel disease.

Cytoprotective effect of neuropeptides on cancer stem cells: vasoactive intestinal peptide-induced antiapoptotic signaling

Cancer stem cells (CSCs) are increasingly considered to be responsible for tumor initiation, metastasis and drug resistance. The drug resistance mechanisms activated in CSCs have not been thoroughly investigated. Although neuropeptides such as vasoactive intestinal peptide (VIP) can promote tumor growth and activate antiapoptotic signaling in differentiated cancer cells, it is not known whether they can activate antiapoptotic mechanisms in CSCs. The objectives of this study are to unravel the cytoprotective effects of neuropeptides and identify antiapoptotic mechanisms activated by neuropeptides in response to anticancer drug treatment in CSCs. We enriched and purified CSCs (CD44^+/high/CD24^-/low or CD133⁺ population) from breast and prostate cancer cell lines, and demonstrated their stemness phenotype. Of the several neuropeptides tested, only VIP could protect CSCs from drug-induced apoptosis. A functional correlation was found between drug-induced apoptosis and dephosphorylation of proapoptotic Bcl2 family protein BAD. Similarly, VIP-induced cytoprotection correlated with BAD phosphorylation at Ser112 in CSCs. Using pharmacological inhibitors and dominant-negative proteins, we showed that VIP-induced cytoprotection and BAD phosphorylation are mediated via both Ras/MAPK and PKA pathways in CSCs of prostate cancer LNCaP and C4-2 cells, but only PKA signaling was involved in CSCs of DUVIPR (DU145 prostate cancer cells ectopically expressing VIP receptor) and breast cancer MCF7 cells. As each of these pathways partially control BAD phosphorylation at Ser112, both have to be inhibited to block the cytoprotective effects of VIP. Furthermore, VIP is unable to protect CSCs that express phosphorylation-deficient mutant-BAD, suggesting that BAD phosphorylation is essential. Thus, antiapoptotic signaling by VIP could be one of the drug resistance mechanisms by which CSCs escape from anticancer therapies. Our findings suggest the potential usefulness of VIP receptor inhibition to eliminate CSCs, and that targeting BAD might be an attractive strategy for development of novel therapeutics.

Vincristine and ɛ-viniferine-loaded PLGA-b-PEG nanoparticles: pharmaceutical characteristics, cellular uptake and cytotoxicity

The objective of this study was to prepare the ɛ-viniferine and vincristine-loaded PLGA-b-PEG nanoparticle and to investigate advantages of these formulations on the cytotoxicity of HepG2 cells. Prepared nanoparticle has shown a homogeneous distribution with 113 ± 0.43 nm particle size and 0.323 ± 0.01 polydispersity index. Zeta potential was determined as -35.03 ± 1.0 mV. The drug-loading percentages were 6.01 ± 0.23 and 2.01 ± 0.07 for ɛ-viniferine and vincristine, respectively. The cellular uptake efficiency of coumarin-6-loaded nanoparticles was increased up to 87.8% after 4 h. Nanoparticles loaded with high concentrations of both drugs showed a cytotoxic effect on HepG2 cells, having the percentage of cell viability of between 43.23% and 47.37%. Unfortunately, the percentage of apoptotic cells after treated with drugs-loaded nanaoparticles (10.93%) was similar to free forms of drugs (12.1%) that might be due to low ɛ-viniferine release in biological pH at 24 h.

A review of the ligands and related targeting strategies for active targeting of paclitaxel to tumours

It has been 30 years since the discovery of the anti-tumour property of paclitaxel (PTX), which has been successfully applied in clinic for the treatment of carcinomas of the lungs, breast and ovarian. However, PTX is poorly soluble in water and has no targeting and selectivity to tumour tissue. Recent advances in active tumour targeting of PTX delivery vehicles have addressed some of the issues related to lack of solubility in water and non-specific toxicities associated with PTX. These PTX delivery vehicles are designed for active targeting to specific cancer cells by the addition of ligands for recognition by specific receptors/antigens on cancer cells. This article will focus on various ligands and related targeting strategies serving as potential tools for active targeting of PTX to tumour tissues, illustrating their use in different tumour models. This review also highlights the need of further studies on the discovery of receptors in different cells of specific organ and ligands with binding efficiency to these specific receptors.

Vasoactive intestinal peptide/pituitary adenylate cyclase activating polypeptide, and their receptors and cancer

PURPOSE OF REVIEW

To summarize the roles of vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase activating polypeptide (PACAP) and their receptors (VPAC1, VPAC2, PAC1) in human tumors as well as their role in potential novel treatments.

RECENT FINDINGS

Considerable progress has been made in understanding of the effects of VIP/PACAP on growth of various tumors as well as in the signaling cascades involved, especially in the role of transactivation of the epidermal growth factor family. The overexpression of VPAC1/2 and PAC1 on a number of common neoplasms (breast, lung, prostate, central nervous system and neuroblastoma) is receiving increased attention both as a means of tumor imaging the location and extent of these tumors, as well as for targeted directed treatment, by coupling cytotoxic agents to VIP/PACAP analogues.

SUMMARY

VIP/PACAP has prominent growth effects on a number of common neoplasms, which frequently overexpressed the three subtypes of their receptors. The increased understanding of their signaling cascades, effect on tumor growth/differentiation and the use of the overexpression of these receptors for localization/targeted cytotoxic delivery are all suggesting possible novel tumor treatments.

Targeted Sterically Stabilized Phospholipid siRNA Nanomedicine for Hepatic and Renal Fibrosis

Since its discovery, small interfering RNA (siRNA) has been considered a potent tool for modulating gene expression. It has the ability to specifically target proteins via selective degradation of messenger RNA (mRNA) not easily accessed by conventional drugs. Hence, RNA interference (RNAi) therapeutics have great potential in the treatment of many diseases caused by faulty protein expression such as fibrosis and cancer. However, for clinical application siRNA faces a number of obstacles, such as poor in vivo stability, and off-target effects. Here we developed a unique targeted nanomedicine to tackle current siRNA delivery issues by formulating a biocompatible, biodegradable and relatively inexpensive nanocarrier of sterically stabilized phospholipid nanoparticles (SSLNPs). This nanocarrier is capable of incorporating siRNA in its core through self-association with a novel cationic lipid composed of naturally occuring phospholipids and amino acids. This overall assembly protects and delivers sufficient amounts of siRNA to knockdown over-expressed protein in target cells. The siRNA used in this study, targets connective tissue growth factor (CTGF), an important regulator of fibrosis in both hepatic and renal cells. Furthermore, asialoglycoprotein receptors are targeted by attaching the galactosamine ligand to the nanocarries which enhances the uptake of nanoparticles by hepatocytes and renal tubular epithelial cells, the major producers of CTGF in fibrosis. On animals this innovative nanoconstruct, small interfering RNA in sterically stabilized phospholipid nanoparticles (siRNA-SSLNP), showed favorable pharmacokinetic properties and accumulated mostly in hepatic and renal tissues making siRNA-SSLNP a suitable system for targeting liver and kidney fibrotic diseases.

A new lipid-based nano formulation of vinorelbine

Vinorelbine (VLB) is a semi-synthetic Vinca alkaloid which is currently used in treatment of different cancer types mainly advanced breast cancer (ABC) and advanced/metastatic non-small cell lung cancer (NSCLC). However, its marketed formulation has been reported to have serious side effects, such as granulocytopenia, which is the major dose-limiting toxicity. Other unwanted effects include venous discoloration and phlebitis proximal to the site of injection, as well as localized rashes and urticaria, blistering, and skin sloughing. Our long-term aim in synthesizing a novel nanomicellar vinorelbine formulation is to reduce or even eliminate these side effects and increase drug activity by formulating the drug in a lipid-based system as a nanomedicine targeted to the site of action. To this end, the purpose of this study was to prepare, characterize, and determine the in vitro efficacy of vinorelbine-loaded sterically stabilized, biocompatible, and biodegradable phospholipid nanomicelles (SSM; size, ∼15 nm). Our results indicated that vinorelbine incorporate at high quantities and within the interface between the core and palisade sections of the micelles. Incorporation ratio of drug within sterically stabilized micelles increased as the total amount of drug in the system increased, and no drug particles were formed at the highest drug concentrations tested. The nanomicellar formulation of vinorelbine was ∼6.7-fold more potent than vinorelbine dissolved in DMSO on MCF-7 cell line. Collectively, these data indicate that vinorelbine-loaded SSM can be developed as a new, safe, stable, and effective nanomedicine for the treatment of breast and lung cancers.

Multifunctional polymeric micelles for delivery of drugs and siRNA

Polymeric micelles, self-assembling nano-constructs of amphiphilic copolymers with a core-shell structure have been used as versatile carriers for delivery of drugs as well as nucleic acids. They have gained immense popularity owing to a host of favorable properties including their capacity to effectively solubilize a variety of poorly soluble pharmaceutical agents, biocompatibility, longevity, high stability in vitro and in vivo and the ability to accumulate in pathological areas with compromised vasculature. Moreover, additional functions can be imparted to these micelles by engineering their surface with various ligands and cell-penetrating moieties to allow for specific targeting and intracellular accumulation, respectively, to load them with contrast agents to confer imaging capabilities, and incorporating stimuli-sensitive groups that allow drug release in response to small changes in the environment. Recently, there has been an increasing trend toward designing polymeric micelles which integrate a number of the above functions into a single carrier to give rise to “smart,” multifunctional polymeric micelles. Such multifunctional micelles can be envisaged as key to improving the efficacy of current treatments which have seen a steady increase not only in hydrophobic small molecules, but also in biologics including therapeutic genes, antibodies and small interfering RNA (siRNA). The purpose of this review is to highlight recent advances in the development of multifunctional polymeric micelles specifically for delivery of drugs and siRNA. In spite of the tremendous potential of siRNA, its translation into clinics has been a significant challenge because of physiological barriers to its effective delivery and the lack of safe, effective and clinically suitable vehicles. To that end, we also discuss the potential and suitability of multifunctional polymeric micelles, including lipid-based micelles, as promising vehicles for both siRNA and drugs.

Solubilization of therapeutic agents in micellar nanomedicines

We use atomistic molecular dynamics simulations to reveal the binding mechanisms of therapeutic agents in PEG-ylated micellar nanocarriers (SSM). In our experiments, SSM in buffer solutions can solubilize either ≈11 small bexarotene molecules or ≈6 (2 in low ionic strength buffer) human vasoactive intestinal peptide (VIP) molecules. Free energy calculations reveal that molecules of the poorly water-soluble drug bexarotene can reside at the micellar ionic interface of the PEG corona, with their polar ends pointing out. Alternatively, they can reside in the alkane core center, where several bexarotene molecules can self-stabilize by forming a cluster held together by a network of hydrogen bonds. We also show that highly charged molecules, such as VIP, can be stabilized at the SSM ionic interface by Coulombic coupling between their positively charged residues and the negatively charged phosphate headgroups of the lipids. The obtained results illustrate that atomistic simulations can reveal drug solubilization character in nanocarriers and be used in efficient optimization of novel nanomedicines.

A novel peptide nanomedicine for treatment of pancreatogenic diabetes

Pancreatogenic diabetes (PD) is a potentially fatal disease that occurs secondary to pancreatic disorders. The current anti-diabetic therapy for PD is fraught with adverse effects that can increase morbidity. Here we investigated the efficacy of novel peptide nanomedicine: pancreatic polypeptide (PP) in sterically stabilized micelles (SSM) for management of PD. PP exhibits significant anti-diabetic efficacy but its short plasma half-life curtails its therapeutic application. To prolong and improve activity of PP in vivo, we evaluated the delivery of PP in SSM. PP-SSM administered to rats with PD, significantly improved glucose tolerance, insulin sensitivity and hepatic glycogen content compared to peptide in buffer. The studies established the importance of micellar nanocarriers in protecting enzyme-labile peptides in vivo and delivering them to target site, thereby enhancing their therapeutic efficacy. In summary, this study demonstrated that PP-SSM is a promising novel anti-diabetic nanomedicine and therefore should be further developed for management of PD.

FROM THE CLINICAL EDITOR

Pancreatic peptide was earlier demonstrated to address pancreatogenic diabetes, but its short half-life represented major difficulties in further development for therapeutic use. PP-SSM (pancreatic polypeptide in sterically stabilized micelles) is a promising novel anti-diabetic nanomedicine that enables prolonged half-life and increased bioactivity of PP, as shown in this novel study, paving the way toward clinical studies in the near future.