ATN-161 Peptide Functionalized Reversibly Cross-Linked Polymersomes Mediate Targeted Doxorubicin Delivery into Melanoma-Bearing C57BL/6 Mice

Targeting Injectable Hydrogels: The Role of Diphenylalanine Peptide Derivative in the Gelation Dynamics of Pluronic® F127

The fluorenyl methyl oxycarbonyl phenylalanyl-phenylalanine methyl ester (Fmoc-Phe-Phe-Ome) was synthetized using the liquid phase synthesis strategy. This derivative was separated by hydrophobic interaction chromatography, its purity was analyzed by RP-HPLC and it was characterized by mass spectrometry. This extremely hydrophobic peptide conjugate was incorporated into aqueous solutions of Pluronic® F127 at low temperatures (below 10 °C). The temperature induced sol-gel transition was investigated by rheological measurements. A delay of the sol-gel transition, caused by the presence of low concentrations of Fmoc-Phe-Phe-Ome (up to 1%), enables better control of the gelation process. The viscoelastic properties of hybrid networks were investigated at 37 °C in different shear conditions. The Pluronic/peptide systems reported herein provide promising alternatives for developing innovative injectable gels as suitable platforms in cancer treatment.

Importance of integrin transmembrane helical interactions for antagonistic versus agonistic ligand behavior: Consequences for medical applications

Integrins are well-characterized receptors involved in cell adhesion and signaling. With six approved drugs, they are recognized as valuable therapeutic targets. Here, we explore potential activation mechanisms that may clarify the agonist versus antagonist behavior of integrin ligands. The reorganization of the transmembrane domain (TMD) in the integrin receptor, forming homooligomers within focal adhesions, could be key to the understanding of the agonistic properties of integrin ligands at substoichiometric concentrations. This has significant implications for medical applications. While we focus on the RGD peptide-recognizing integrin subfamily, we propose that these mechanistic insights may also apply to other integrin subtypes. For application of integrin ligands in medicine it is essential to consider this mechanism and its consequences for affinity and bioavailability.

Bioresponsive Polymeric Nanoparticles: From Design, Targeted Therapy to Cancer Immunotherapy

Bioresponsive polymeric nanoparticles (NPs) that are capable of delivering and releasing therapeutics and biotherapeutics to target sites have attracted vivid interest in cancer therapy and immunotherapy. In contrast to enthusiastic evolution in the academic world, the clinical translation of these smart systems is scarce, partly due to concerns about safety, stability, complexity, and scalability. The moderate targetability, responsivity, and benefits are other concerns. In the past 17 years, we have devoted ourselves to exploring elegant strategies to address the above basic and translational problems by introducing diverse functional groups and/or targeting ligands to safe biomedical materials, such as biodegradable polymers and water-soluble polymers. This minimal modification is critical for further clinical translation. We have tailor-made various bioresponsive NPs including shell-sheddable and/or acid-sensitive biodegradable NPs, disulfide-cross-linked biodegradable micelles and polymersomes, and blood-brain barrier (BBB)-permeable NPs, to target different tumors. This perspective provides an overview of our work path toward targeted nanomedicines and personalized vaccines, which might inspire clinical translation and future research on cancer therapy.

Polymersome Membrane Engineering with Active Targeting or Controlled Permeability for Responsive Drug Delivery

Polymersomes have been extensively investigated for drug delivery as nanocarriers for two decades due to a series of advantages including high stability under physiological conditions, simultaneous encapsulation of hydrophilic and hydrophobic drugs inside inner cavities and membranes, respectively, and facile adjustment of membrane and surface properties, as well as controlled drug release through incorporation of stimuli-responsive components. Despite these features, polymersome nanocarriers frequently suffer from nontargeting delivery and poor membrane permeability. In recent years, polymersomes have been functionalized for more efficient drug delivery. The surface shells were explored to be modified with diverse active targeting groups to improve disease-targeting delivery. The membrane permeability of the polymersomes was adjusted by incorporation of the stimuli-responsive components for smart controlled transportation of the encapsulated drugs. Therefore, being the polymersome-biointerface, tailorable properties can be introduced by its carefully modulated engineering. This review elaborates on the role of polymersome membranes as a platform to incorporate versatile features. First, we discuss how surface functionalization facilitates the directional journey to the targeting sites toward specific diseases, cells, or intracellular organelles via active targeting. Moreover, recent advances in the past decade related to membrane permeability to control drug release are also summarized. We finally discuss future development to promote polymersomes as in vivo drug delivery nanocarriers.

Therapeutic targeting of anoikis resistance in cutaneous melanoma metastasis

The acquisition of resistance to anoikis, the cell death induced by loss of adhesion to the extracellular matrix, is an absolute requirement for the survival of disseminating and circulating tumour cells (CTCs), and for the seeding of metastatic lesions. In melanoma, a range of intracellular signalling cascades have been identified as potential drivers of anoikis resistance, however a full understanding of the process is yet to be attained. Mechanisms of anoikis resistance pose an attractive target for the therapeutic treatment of disseminating and circulating melanoma cells. This review explores the range of small molecule, peptide and antibody inhibitors targeting molecules involved in anoikis resistance in melanoma, and may be repurposed to prevent metastatic melanoma prior to its initiation, potentially improving the prognosis for patients.

Co-delivery of gemcitabine and paclitaxel plus NanoCpG empowers chemoimmunotherapy of postoperative "cold" triple-negative breast cancer

Triple-negative breast cancer (TNBC) due to lack of clear target and notorious "cold" tumor microenvironment (TME) is one of the most intractable and lethal malignancies. Tuning "cold" TME into "hot" becomes an emerging therapeutic strategy to TNBC. Herewith, we report that integrin-targeting micellar gemcitabine and paclitaxel (ATN-mG/P, ATN sequence: Ac-PhScNK-NH₂) cooperating with polymersomal CpG (NanoCpG) effectively "heated up" and treated TNBC. ATN-mG/P exhibited greatly boosted apoptotic activity in 4T1 cells, induced potent immunogenic cell death (ICD), and efficiently stimulated maturation of bone marrow-derived dendritic cells (BMDCs). Remarkably, in a postoperative TNBC model, ATN-mG/P combining with NanoCpG promoted strong anti-cancer immune responses, showing a greatly augmented proportion of mature DCs and CD8⁺ T cells while reduced immune-suppressive myeloid-derived suppressor cells (MDSCs) and regulatory T cells (T_reg), which led to complete inhibition of lung metastasis and 60% mice tumor-free. The co-delivery of gemcitabine and paclitaxel at desired ratio in combination with NanoCpG provides a unique platform for potent chemoimmunotherapy of "cold" tumors like TNBC.

Delivery of Theranostic Nanoparticles to Various Cancers by Means of Integrin-Binding Peptides

Active targeting of tumors is believed to be the key to efficient cancer therapy and accurate, early-stage diagnostics. Active targeting implies minimized off-targeting and associated cytotoxicity towards healthy tissue. One way to acquire active targeting is to employ conjugates of therapeutic agents with ligands known to bind receptors overexpressed onto cancer cells. The integrin receptor family has been studied as a target for cancer treatment for almost fifty years. However, systematic knowledge on their effects on cancer cells, is yet lacking, especially when utilized as an active targeting ligand for particulate formulations. Decoration with various integrin-targeting peptides has been reported to increase nanoparticle accumulation in tumors ≥ 3-fold when compared to passively targeted delivery. In recent years, many newly discovered or rationally designed integrin-binding peptides with excellent specificity towards a single integrin receptor have emerged. Here, we show a comprehensive analysis of previously unreviewed integrin-binding peptides, provide diverse modification routes for nanoparticle conjugation, and showcase the most notable examples of their use for tumor and metastases visualization and eradication to date, as well as possibilities for combined cancer therapies for a synergetic effect. This review aims to highlight the latest advancements in integrin-binding peptide development and is directed to aid transition to the development of novel nanoparticle-based theranostic agents for cancer therapy.

Polymeric nanocarriers: A promising tool for early diagnosis and efficient treatment of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is the third most prevalent type of cancer for incidence and second for mortality worldwide. Late diagnosis and inconvenient and expensive current diagnostic tools largely contribute to the progress of the disease. The use of chemotherapy in the management of CRC significantly reduces tumor growth, metastasis, and morbidity rates. However, poor solubility, low cellular uptake, nonspecific distribution, multiple drug resistance and unwanted adverse effects are still among the major drawbacks of chemotherapy that limit its clinical significance in the treatment of CRC. Owing to their remarkable advantages over conventional therapies, the use of nanotechnology-based delivery systems especially polymeric nanocarriers (PNCs) has revolutionized many fields including disease diagnosis and drug delivery.

AIM OF REVIEW

In this review, we shed the light on the current status of using PNCs in the diagnosis and treatment of CRC with a special focus on targeting strategies, surface modifications and safety concerns for different types of PNCs in colonic cancer delivery.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The review explores the current progress on the use of PNCs in the diagnosis and treatment of CRC with a special focus on the role of PNCs in improvement of cellular uptake, drug targeting and co-delivery of chemotherapeutic agents. Possible toxicity and biocompatibility issues related to the use of PNCs and imitations and future recommendation for the use of those smart carriers in the diagnosis and treatment of CRC are also discussed.

Chenodeoxycholic acid inhibits lung adenocarcinoma progression via the integrin α5β1/FAK/p53 signaling pathway

BACKGROUND

Lung cancer is the leading cause of cancer-associated death worldwide and is classified into non-small cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). NSCLC accounts for approximately 80%-85% of all lung cancer cases. Chenodeoxycholic acid (CDCA), a primary bile acid, has been reported to inhibit carcinoma cell proliferation. Here, we aimed to determine the effects and mechanism of action of CDCA against lung adenocarcinoma (LUAD).

METHODS

Western blotting and quantitative real-time polymerase chain reaction were used to evaluate the protein and mRNA expression levels in LUAD cell lines, respectively. Cell Counting Kit-8 and clone formation assays were performed to evaluate the proliferation ability of different cell types in vitro. Tumor cell motility was evaluated using Transwell assays. The transcriptional profile of A549 cells treated with CDCA was determined through RNA sequencing analysis. A xenograft model was established to evaluate the effects of CDCA on LUAD progression in vivo.

RESULTS

CDCA inhibited LUAD cell proliferation, migration, and invasion. Furthermore, it promoted apoptosis in LUAD cells. Mechanistically, CDCA inhibited the integrin α5β1 signaling pathway in LUAD cells by inhibiting the expression of the α5 and β1 subunits of integrin and phosphorylated FAK. Moreover, CDCA induced an increase in the levels of p53, a downstream gene of the integrin α5β1/FAK pathway. In addition, CDCA significantly decreased tumor volume in mice without inducing significant toxicity.

CONCLUSIONS

Our findings indicate that CDCA attenuates LUAD pathogenesis in vitro and in vivo via the integrin α5β1/FAK/p53 axis.

Doxorubicin Delivered via ApoE-Directed Reduction-Sensitive Polymersomes Potently Inhibit Orthotopic Human Glioblastoma Xenografts in Nude Mice

Purpose

Glioblastoma multiforme (GBM) poorly responds to chemotherapy owing to the existence of blood-brain barriers (BBB). It has been a long desire to develop BBB-permeable vehicles to facilitate drug targeting to GBM.

Method and Results

Here, we report that doxorubicin hydrochloride loaded in ApoE peptide-functionalized reduction-sensitive polymersomes (ApoE-PS-DOX) induces potent therapy of orthotopic U-87 MG model in nude mice. ApoE-PS-DOX with varying amount of ApoE (10~30 mol%) all had stable DOX loading and small sizes (< 90 nm). As revealed by flow cytometry, confocal microscopy, apoptosis and MTT assays, ApoE-PS-DOX with 20 mol.% ApoE induced the best cellular uptake and inhibitory effect to U-87 MG cells, which were much better than the non-targeted PS-DOX and liposomal doxorubicin (Lipo-DOX) used in the clinic. ApoE-PS-DOX revealed a pharmacokinetic profile comparable to PS-DOX but induced considerably better growth inhibition of orthotopically xenografted U-87 MG tumors in nude mice than PS-DOX and Lipo-DOX, leading to significant survival benefits with a median survival time of 44 days, which was almost doubled relative to the phosphate-buffered saline (PBS) group. Moreover, in contrast to mice treated with Lipo-DOX and PS-DOX, ApoE-PS-DOX group exhibited little body weight loss, signifying that ApoE-PS-DOX not only has low side effects but also can effectively inhibit glioblastoma invasion.

Conclusion

This ApoE-docked multifunctional polymersomal doxorubicin induces potent and safe chemotherapy of orthotopic U-87 MG model in nude mice offering an alternative treatment modality for GBM.

Nanoporous Gold Monolith for High Loading of Unmodified Doxorubicin and Sustained Co-Release of Doxorubicin-Rapamycin

Nanoparticles (NPs) have been widely explored for delivering doxorubicin (DOX), an anticancer drug, to minimize cardiotoxicity. However, their efficiency is marred by a necessity to chemically modify DOX, NPs, or both and low deposition of the administered NPs on tumors. Therefore, alternative strategies should be developed to improve therapeutic efficacy and decrease toxicity. Here we report the possibility of employing a monolithic nanoporous gold (np-Au) rod as an implant for delivering DOX. The np-Au has very high DOX encapsulation efficiency (>98%) with maximum loading of 93.4 mg cm-3 without any chemical modification required of DOX or np-Au. We provide a plausible mechanism for the high loading of DOX in np-Au. The DOX sustained release for 26 days from np-Au in different pH conditions at 37 °C, which was monitored using UV-Vis spectroscopy. Additionally, we encased the DOX-loaded np-Au with rapamycin (RAPA)-trapped poly(D,L-lactide-co-glycolide) (PLGA) to fabricate an np-Au@PLGA/RAPA implant and optimized the combinatorial release of DOX and RAPA. Further exploiting the effect of the protein corona around np-Au and np-Au@PLGA/RAPA showed zero-order release kinetics of DOX. This work proves that the np-Au-based implant has the potential to be used as a DOX carrier of potential use in cancer treatment.

Targeting self-assembled F127-peptide polymer with pH sensitivity for release of anticancer drugs

The treatment of breast cancer mainly relies on chemotherapy drugs, which present significant side effects.

SP94 peptide mediating highly specific and efficacious delivery of polymersomal doxorubicin hydrochloride to hepatocellular carcinoma in vivo

The effective treatment of hepatocellular carcinoma (HCC) requires development of novel drug formulations that selectively kill HCC cells while sparing healthy liver cells. Here, we designed and investigated HCC-specific peptide, SP94 (SFSIIHTPILPLGGC), decorated smart polymersomal doxorubicin hydrochloride (SP94-PS-DOX) for potent treatment of orthotopic human SMMC-7721 HCC xenografts. SP94-PS-DOX was fabricated by post ligand-modification, affording robust nano-formulations with a diameter of ∼ 76 nm and DOX content of 9.9 wt.%. The internalization of SP94-PS-DOX by SMMC-7721 cells showed a clear dependence on SP94 surface densities, in which 30 % SP94 resulted in ca. 3-fold better cellular uptake over non-targeted control (PS-DOX). In accordance, SP94-PS-DOX exhibited superior inhibition of SMMC-7721 cells to PS-DOX and clinical liposome injections (Lipo-DOX). Notably, a remarkable tumor deposition of 14.9 %ID/g and tumor-to-normal liver ratio of ca. 6.9 was observed for SP94-PS-DOX in subcutaneous SMMC-7721 HCC xenografts. More interestingly, SP94-PS-DOX under 10 mg DOX/kg induced far better therapeutic efficacy toward orthotopic SMMC-7721 HCC models than PS-DOX and Lipo-DOX controls giving substantial survival benefits and little adverse effects. The remarkable specificity and therapeutic outcomes lend SP94-PS-DOX promising for targeted HCC therapy.

Dithiolane-Crosslinked Poly(ε-caprolactone)-Based Micelles: Impact of Monomer Sequence, Nature of Monomer, and Reducing Agent on the Dynamic Crosslinking Properties

Dithiolanes are used to obtain dynamic and reversible crosslinks between polymer chains. Copolymers of two different dithiolane-containing cyclic carbonate monomers and ε-caprolactone (CL) were synthesized by ring-opening polymerization using a methoxy-poly(ethylene glycol) (mPEG) initiator and different catalysts (diphenyl phosphate (DPP), methanesulfonic acid (MSA), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), or Sn(Oct)2). Each catalyst required a different temperature, which had a pronounced influence on the reactivity ratio of the monomers and occurrence of transesterification reactions and, therefore, the monomer sequence. Self-crosslinkable copolymers were obtained when the dithiolane units were connected closely to the polymer backbone, whereas the presence of a linker unit between the dithiolane and the backbone prevented self-crosslinking. The former amphiphilic PEGylated block copolymers formed micelles by nanoprecipitation in the aqueous environment and crosslinked spontaneously by disulfide exchange during subsequent dialysis. These dithiolane-crosslinked micelles showed reduction-responsive dissociation in the presence of 10 mM glutathione, making them promising drug delivery systems for the intracellularly triggered cargo release.

Polymer Nanocontainers for Intracellular Delivery

Carriers for intracellular delivery are required to overcome limitations of therapeutic agents such as low specificity, systemic toxicity, high clearance rate, and low therapeutic index. Nanocontainers comprised of an aqueous core and a polymer shell have received increasing attention because they readily combine stimuli response to improve intracellular payload release and surface modification to enhance selectivity towards the desired region of action. This Minireview summarizes the design and properties of polymer nanocontainers for intracellular delivery, classified according to the polymer architecture.

Double Switch Biodegradable Porous Hollow Trinickel Monophosphide Nanospheres for Multimodal Imaging Guided Photothermal Therapy

Due to the limitation of inorganic nanomaterials in present clinical applications induced by their inherent nonbiodegradability and latent long-term side effects, we successfully prepared double switch degradable and clearable trinickel monophosphide porous hollow nanospheres (NiP PHNPs) modified with bovine serum albumin (BSA). Attributed to their acidic and oxidative double switch degradation capacities, NiP PHNPs can be effectively excreted from mice without long-term toxicity. Moreover, because of the paramagnetic and high molar extinction coefficient property resulting from the strong absorption in the second near-infrared light (NIR II) biowindow, NiP PHNPs have potential to be used for photoacoustic imaging (PAI) and T₁-weighted magnetic resonance imaging (MRI) guided photothermal ablation of tumors in the NIR II biowindow. Specifically, it is interesting that the hollow structure and acidic degradation property enable NiP PHNPs to act as intelligent drug carriers with an on-demand release ability. These findings highlight the great potential of NiP PHNPs in the cancer theranostics field and inspire us to further broaden the bioapplications of transition metal phosphides.

Oncoprotein Inhibitor Rigosertib Loaded in ApoE-Targeted Smart Polymersomes Reveals High Safety and Potency against Human Glioblastoma in Mice

The unbiased cytotoxicity and blood-brain barrier (BBB) impermeability render common chemotherapeutics nonviable for treating glioblastoma (GBM) patients. Although rigosertib (RGS), a RAS effector protein inhibitor, has shown low toxicity to healthy cells and high efficacy toward various cancer cells by inactivating PI3K-Akt, it hardly overcomes the BBB barricade. Here, we report that RGS loaded in apolipoprotein E derived peptide (ApoE)-targeted chimaeric polymersomes (ApoE-CP) is safe and highly potent against human GBM in vivo. ApoE-CP exhibited stable loading of RGS in its lumen, giving RGS nanoformulations (ApoE-CP-RGS) with a size of 60 nm and reduction-triggered drug release behavior. Notably, ApoE-CP-RGS induction markedly enhanced the G2/M cell cycle arrest and inhibitory effect in U-87 MG glioblastoma cells compared with the nontargeted CP-RGS and free RGS. The therapeutic outcomes in orthotopic U-87 MG GBM models demonstrated that ApoE-CP-RGS brought about effective GBM inhibition, greatly prolonged survival time, and depleted adverse effects. Rigosertib formulated in ApoE-targeted chimaeric polymersomes has emerged as a novel, highly specific, efficacious, and nontoxic treatment for glioblastoma.

Low-toxicity transferrin-guided polymersomal doxorubicin for potent chemotherapy of orthotopic hepatocellular carcinoma in vivo

Hepatocellular carcinoma (HCC) remains one of the most lethal malignancies. The current chemotherapy with typically low tumor uptake and high toxicity reveals a poor anti-HCC efficacy. Here, we report transferrin-guided polycarbonate-based polymersomal doxorubicin (Tf-Ps-Dox) as a low-toxic and potent nanotherapeutic agent for effective treatment of liver tumor using a transferrin receptor (TfR)-positive human liver tumor SMMC-7721 model. Tf-Ps-Dox was facilely fabricated with small size of ca. 75 nm and varying Tf densities from 2.2% to 7.0%, by postmodification of maleimide-functionalized Ps-Dox (Dox loading content of 10.6 wt%) with thiolated transferrin. MTT assays showed that Tf-Ps-Dox had an optimal Tf surface density of 3.9%. The cellular uptake, intracellular Dox level, and anticancer efficacy of Tf-Ps-Dox to SMMC-7721 cells were inhibited by supplementing free transferrin, which supports that Tf-Ps-Dox is endocytosed through TfR. Interestingly, Tf-Ps-Dox exhibited a high accumulation of 8.5%ID/g (percent injected dose per gram of tissue) in subcutaneous SMMC-7721 tumors, which was 2- and 3-fold higher than that of nontargeted Ps-Dox and clinically used liposomal Dox formulation (Lipo-Dox), respectively. The median survival times of mice bearing orthotopic SMMC-7721 tumors increased from 82, 88 to 96 days when treated with Tf-Ps-Dox at Dox doses from 8, 12 to 16 mg/kg, which was significantly longer than that of Ps-Dox at 8 mg/kg (58 days) and Lipo-Dox at 4 mg/kg (48 days) or PBS (36 days). Notably, unlike Lipo-Dox, no body weight loss and damage to major organs could be discerned for all Tf-Ps-Dox groups, indicating that Tf-Ps-Dox caused low systemic toxicity. This transferrin-dressed polymersomal doxorubicin provides a potent and low-toxic treatment modality for human hepatocellular carcinoma. STATEMENT OF SIGNIFICANCE: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. Vast work has focused on developing HCC-targeted nanotherapeutics. However, none of the nanotherapeutics has advanced to clinics, partly because the ligands used have not been validated in patients. Transferrin (Tf) is a natural ligand for transferrin receptor (TfR) that is overexpressed on cancerous cells, and it is currently under clinical trials (MBP-426 and CALAA-01) for the treatment of solid tumors. We designed Tf-functionalized polymersomal doxorubicin (Tf-Ps-Dox) for targeted therapy of orthotopic SMMC-7721 tumor in nude mice. Tf-Ps-Dox showed potent anti-HCC efficacy and significantly improved survival time with low toxicity as compared with nontargeted Ps-Dox and clinical liposomal Dox (Lipo-Dox). Hence, Tf-Ps-Dox is very appealing for targeted treatment of HCC.

The functional role of integrins during intra- and extravasation within the metastatic cascade

Formation of distant metastases is by far the most common cause of cancer-related deaths. The process of metastasis formation is complex, and within this complex process the formation of migratory cells, the so called epithelial mesenchymal transition (EMT), which enables cancer cells to break loose from the primary tumor mass and to enter the bloodstream, is of particular importance. To break loose from the primary cancer, cancer cells have to down-regulate the cell-to-cell adhesion molecuIes (CAMs) which keep them attached to neighboring cancer cells. In contrast to this downregulation of CAMS in the primary tumor, cancer cells up-regulate other types of CAMs, that enable them to attach to the endothelium in the organ of the future metastasis. During EMT, the expression of cell-to-cell and cell-to-matrix adhesion molecules and their down- and upregulation is therefore critical for metastasis formation. Tumor cells mimic leukocytes to enable transmigration of the endothelial barrier at the metastatic site. The attachment of leukocytes/cancer cells to the endothelium are mediated by several CAMs different from those at the site of the primary tumor. These CAMs and their ligands are organized in a sequential row, the leukocyte adhesion cascade. In this adhesion process, integrins and their ligands are centrally involved in the molecular interactions governing the transmigration. This review discusses the integrin expression patterns found on primary tumor cells and studies whether their expression correlates with tumor progression, metastatic capacity and prognosis. Simultaneously, further possible, but so far unclearly characterized, alternative adhesion molecules and/or ligands, will be considered and emerging therapeutic possibilities reviewed.

Protein Nanotherapeutics as an Emerging Modality for Cancer Therapy

Protein drugs are a unique and versatile class of biotherapeutics that have not only high biological activity but also superb specificity. This rapidly evolving biotechnology has rendered it possible to produce various proteins in a large scale and reproducible way. Many proteins have demonstrated striking anticancer activities and have emerged as advanced alternatives to cytotoxic chemotherapeutic agents for cancer therapy. The clinical translation of anticancer proteins with intracellular targets is, nevertheless, severely hindered by their fast degradation in vivo, poor cell penetration, and inefficient intracellular transportation. The past few years have witnessed tremendous effort and progress in developing polymeric protein delivery nanosystems, ranging from nanoparticles, nanocapsules, nanogels, micelles, to polymersomes, for the treatment of different tumors such as lung tumors, breast tumors, ovarian cancers, and glioblastoma. These proof-of-concept studies point out that protein nanotherapeutics, with rationally designed nanovehicles, are able to overcome the extracellular barriers, cell membrane barriers, and intracellular barriers, and systemically deliver proteins into targeted cancer cells, resulting in effective cancer protein therapy. Protein nanotherapeutics appear to be a novel modality for safe and efficient cancer treatment.

Cyclic RGD-Peptide-Functionalized Polylipopeptide Micelles for Enhanced Loading and Targeted Delivery of Monomethyl Auristatin E

Monomethyl auristatin E (MMAE) is an extremely potent peptide drug that is currently used in the form of antibody drug conjugates (ADCs) for treating different cancers. ADCs are, however, associated with low drug conjugation, immunogenicity, small scale production, and high costs. Here, cRGD-functionalized polylipopeptide micelles (cRGD-Lipep-Ms) were explored for enhanced loading and targeted delivery of MMAE to HCT-116 colorectal tumor xenografts. Interestingly, cRGD-Lipep-Ms achieved an MMAE loading content of 5.5 wt %, which was 55-fold higher than that of poly(ethylene glycol)- b-poly(d,l-lactide) micelles. MMAE-loaded cRGD-Lipep-Ms (MMAE-cRGD-Lipep-Ms) showed a small hydrodynamic size of 59 nm, minimal drug leakage in 10% FBS, and efficient uptake and superb antiproliferative activity in α_vβ₅-overexpressing HCT-116 tumor cells. Remarkably, MMAE-cRGD-Lipep-Ms displayed over 10-fold better toleration than free MMAE in mice and completely suppressed growth of HCT-116 colorectal tumor xenografts. These polylipopeptide micelles have appeared to be an attractive alternative to ADCs for targeted delivery of potent peptide drugs.

Synthesis and Characterization of 1,2-Dithiolane Modified Self-Assembling Peptides

This report focuses on the synthesis of an N-terminus 1,2-dithiolane modified self-assembling peptide and the characterization of the resulting self-assembled supramolecular structures. The synthetic route takes advantage of solid-phase peptide synthesis with the on-resin coupling of the dithiolane precursor molecule, 3-(acetylthio)-2-(acetylthiomethyl)propanoic acid, and the microwave-assisted thioacetate deprotection of the peptide N-terminus before final cleavage from the resin to yield the 1,2-dithiolane modified peptide. After the high-performance liquid chromatography (HPLC) purification of the 1,2-dithiolane peptide, derived from the nucleating core of the Aβ peptide associated with Alzheimer's disease, the peptide is shown to self-assemble into cross-β amyloid fibers. Protocols to characterize the amyloid fibers by Fourier-transform infrared spectroscopy (FT-IR), circular dichroism spectroscopy (CD) and transmission electron microscopy (TEM) are presented. The methods of N-terminal modification with a 1,2-dithiolane moiety to well-characterized self-assembling peptides can now be explored as model systems to develop post-assembly modification strategies and explore dynamic covalent chemistry on supramolecular peptide nanofiber surfaces.

Reduction-sensitive polymeric nanomedicines: An emerging multifunctional platform for targeted cancer therapy

The development of smart delivery systems that are robust in circulation and quickly release drugs following selective internalization into target cancer cells is a key to precision cancer therapy. Interestingly, reduction-sensitive polymeric nanomedicines showing high plasma stability and triggered cytoplasmic drug release behavior have recently emerged as one of the most exciting platforms for targeted delivery of various anticancer drugs including small chemical drugs, proteins, and nucleic acids. In vivo studies in varying tumor models reveal that these reduction-sensitive multifunctional nanomedicines outperform the currently used clinical formulations and reduction-insensitive counterparts, bringing about not only significantly enhanced tumor selectivity, accumulation and inhibition efficacy but also markedly reduced systemic toxicity and improved therapeutic index. In this review, we will highlight the cutting-edge advancement with a focus on in vivo performances as well as future perspectives on reduction-sensitive polymeric nanomedicines for targeted cancer therapy.

Integrins as therapeutic targets in the organ-specific metastasis of human malignant melanoma

Integrins are a large family of adhesion molecules that mediate cell-cell and cell-extracellular matrix interactions. Among the 24 integrin isoforms, many have been found to be associated with tumor angiogenesis, tumor cell migration and proliferation, and metastasis. Integrins, especially αvβ3, αvβ5 and α5β1, participate in mediating tumor angiogenesis by interacting with the vascular endothelial growth factor and angiopoietin-Tie signaling pathways. Melanoma patients have a poor prognosis when the primary tumor has generated distant metastases, and the melanoma metastatic site is an independent predictor of the survival of these patients. Different integrins on the melanoma cell surface preferentially direct circulating melanoma cells to different organs and promote the development of metastases at specific organ sites. For instance, melanoma cells expressing integrin β3 tend to metastasize to the lungs, whereas those expressing integrin β1 preferentially generate lymph node metastases. Moreover, tumor cell-derived exosomes which contain different integrins may prepare a pre-metastatic niche in specific organs and promote organ-specific metastases. Because of the important role that integrins play in tumor angiogenesis and metastasis, they have become promising targets for the treatment of advanced cancer. In this paper, we review the integrin isoforms responsible for angiogenesis and organ-specific metastasis in malignant melanoma and the inhibitors that have been considered for the future treatment of metastatic disease.

GE11-Directed Functional Polymersomal Doxorubicin as an Advanced Alternative to Clinical Liposomal Formulation for Ovarian Cancer Treatment

Ovarian cancer as a recurrent disease is often refractory to treatment including pegylated liposomal doxorubicin hydrochloride (Lipo-Dox). Here, GE11 peptide-modified reversibly cross-linked polymersomal doxorubicin (GE11-PS-Dox) was investigated as an advanced treatment for SKOV3 human ovarian tumors, which overexpress epidermal growth factor receptor (EGFR). The in vitro experiments using SKOV3 cancer cells demonstrated that GE11-PS-Dox induced obviously higher cellular uptake, Dox delivery to the nuclei, and antitumor activity than the nontargeted PS-Dox and Lipo-Dox controls. In vivo biodistribution experiments displayed 2.5-fold higher tumor accumulation for GE11-PS-Dox as compared to Lipo-Dox. Notably, GE11-PS-Dox could effectively suppress the progression of SKOV3 tumors and cause little adverse effects at 12 mg of Dox equiv/kg, leading to a remarkably increased survival rate of 100% over 78 days. In contrast, continued tumor growth and body weight loss were discerned for Lipo-Dox treated mice at 6 mg of Dox equiv/kg. Moreover, a single dose of GE11-PS-Dox at 60 mg of Dox equiv/kg showed also effective treatment and low toxicity toward SKOV3-tumor bearing mice. GE11-directed reversibly cross-linked polymersomal doxorubicin has emerged as an advanced alternative to Lipo-Dox for treatment of EGFR-overexpressing ovarian cancers.

Lung cancer specific and reduction-responsive chimaeric polymersomes for highly efficient loading of pemetrexed and targeted suppression of lung tumor in vivo

Lung cancer is one of the worldwide leading and fast-growing malignancies. Pemetrexed disodium (PEM, Alimta®), a small hydrophilic drug, is currently used for treating lung cancer patients. However, PEM suffers from issues like fast elimination, low bioavailability, poor tumor cell selectivity and penetration. Here, we report on lung cancer specific CSNIDARAC (CC₉) peptide-functionalized reduction-responsive chimaeric polymersomes (CC₉-RCPs) for efficient encapsulation and targeted delivery of PEM to H460 human lung cancer cells in vitro and in vivo. PEM-loaded CC₉-RCPs (PEM-CC₉-RCPs) was obtained from co-self-assembly of poly(ethylene glycol)-b-poly(trimethylene carbonate-co-dithiolane trimethylene carbonate)-b-polyethylenimine (PEG-P(TMC-DTC)-PEI) and CC₉-functionalized PEG-P(TMC-DTC) in the presence of PEM followed by self-crosslinking. PEM-CC₉-RCPs displayed an optimal CC₉ density of 9.0% in targeting H460 cells, a high PEM loading content of 14.2 wt%, a small hydrodynamic size of ca. 60 nm and glutathione-triggered PEM release. MTT assays showed that PEM-CC₉-RCPs was 2.6- and 10- fold more potent to H460 cells than the non-targeting PEM-RCPs and free PEM controls, respectively. Interestingly, PEM-CC₉-RCPs exhibited 22-fold longer circulation time and 9.1-fold higher accumulation in H460 tumor than clinical formulation Alimta®. Moreover, CC₉-RCPs showed obviously better tumor penetration than RCPs. Remarkably, PEM-CC₉-RCPs at 12.5 mg PEM equiv./kg effectively suppressed growth of H460 xenografts and significantly prolonged mouse survival time as compared to PEM-RCPs and Alimta® controls. These lung cancer specific and reduction-responsive chimaeric polymersomes provide a unique pemetrexed nanoformulation for targeted lung cancer therapy.

STATEMENT OF SIGNIFICANCE

Multitargeted antifolate agent pemetrexed (PEM, Alimta®) is currently used for treating lung cancer patients and has low side-effects. However, PEM suffers from issues like fast elimination, low bioavailability, poor tumor cell selectivity and penetration. Scarce work on targeted delivery of PEM has been reported, partly because most conventional nanocarriers show a low and instable loading for hydrophilic, negatively charged drugs like PEM. Herewith, we report on lung cancer specific CSNIDARAC (CC₉) peptide-functionalized reduction-responsive chimaeric polymersomes (CC₉-RCPs) which showed efficient PEM encapsulation (14.2 wt%, 60 nm) and targeted delivery of PEM to H460 human lung cancer cells, leading to effective suppression of H460 tumor xenografts and significantly prolonged survival rates of mice than Alimta®. To the best of our knowledge, this represents a first report on targeted nanosystems that are capable of efficient loading and targeted delivery of PEM to lung tumors.

Selective Cell Penetrating Peptide-Functionalized Polymersomes Mediate Efficient and Targeted Delivery of Methotrexate Disodium to Human Lung Cancer In Vivo

It is a long challenge to develop nanomedicines that simultaneously possess tumor cell selectivity and penetration functions. Here, it is reported that selective cell penetrating peptide (RLWMRWYSPRTRAYGC)-functionalized polymersomes (SCPP-PS) mediate efficient and targeted delivery of methotrexate disodium (MTX) to human lung cancer in vivo. SCPP-PS with an SCPP density of 18.7% is self-crosslinked, has a small size (63-65 nm), and high MTX loading (up to 19.4 wt%), shows selective uptake and fast penetration into A549 lung cancer cells, and efficiently releases MTX intracellularly. Interestingly, MTX-loaded SCPP-PS (MTX-SCPP-PS) displays much lower IC₅₀ than those of MTX-PS and free MTX. Installing SCPP to polymersomes has no detrimental effect to their long blood circulation time but significantly increases drug accumulation in A549 tumor (5.3% injected dose per gram at 8 h post injection). Remarkably, SCPP-PS exhibits deep penetration in to A549 tumors. MTX-SCPP-PS completely inhibits tumor progression and significantly improves survival rates in mice bearing A549 lung tumor xenografts as compared to MTX-PS and free MTX groups (median survival time: 75 vs 45 and 38 d, respectively), without causing noticeable adverse effects. These results highlight that functionalization of nanomedicines with SCPP is a feasible strategy to achieve efficient and targeted tumor therapy.

Reduction Responsive Nanovesicles Derived from Novel α-Tocopheryl-Lipoic Acid Conjugates for Efficacious Drug Delivery to Sensitive and Drug Resistant Cancer Cells

Two novel α-tocopheryl-lipoic acid conjugates (TL1 and TL2) were synthesized for the anticancer drug, doxorubicin (DOX), delivery. Both conjugates were able to form stable nanovesicles. The critical aggregation concentration (CAC) was determined using 4-(N,N-dimethylamino)cinnamaldehyde (DMACA) as a fluorescence probe. Formation of highly packed nanovesicles was characterized by 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence anisotropy and microviscosity measurements. The morphologies of nanovesicles were visualized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The response of nanovesicles to reducing environment of cells was probed by the addition of dithiothreitol (DTT), which was followed by the increase in the hydrodynamic diameter under dynamic light scattering (DLS) measurements. The encapsulation efficiency of a commonly used anticancer drug, doxorubicin (DOX), in nanovesicles was found to be ∼60% and ∼55% for TL1 and TL2, respectively (TL1-DOX and TL2-DOX). Also, the cumulative drug (DOX) release from DOX-encapsulated nanovesicles in response to biological reducing agent glutathione (GSH) was ∼50% and ∼40% for TL1-DOX and TL2-DOX, respectively, over a period of 10 h. Both TL1-DOX and TL2-DOX delivered the anticancer drug, doxorubicin (DOX), across the DOX-sensitive and DOX-resistant HeLa (HeLa-DOX^R) cells in an efficient manner and significantly more efficaciously than the drug alone treatments, especially in HeLa-DOX^R cells. The nanovesicle mediated DOX treatment also showed significantly higher cell death when compared to DOX alone treatment in HeLa-DOX^R cells. Blood compatibility of the nanovesicles was supported from clotting time, hemolysis, and red blood cell (RBC) aggregation experiments for their potential in vivo applications. Concisely, we present biocompatible and responsive nanovesicles for efficacious drug delivery to drug-sensitive and drug-resistant cancer cells.

Hyaluronic Acid-Shelled Disulfide-Cross-Linked Nanopolymersomes for Ultrahigh-Efficiency Reactive Encapsulation and CD44-Targeted Delivery of Mertansine Toxin

It was and remains a big challenge for cancer nanomedicines to achieve high and stable drug loading with fast drug release in the target cells. Here, we report on novel hyaluronic acid-shelled disulfide-cross-linked biodegradable polymersomes (HA-XPS) self-assembled from hyaluronic acid-b-poly(trimethylene carbonate-co-dithiolane trimethylene carbonate) diblock copolymer for ultrahigh-efficiency reactive encapsulation and CD44-targeted delivery of mertansine (DM1) toxin, a highly potent warhead for clinically used antibody-drug conjugates. Remarkably, HA-XPS showed quantitative encapsulation of DM1 even with a high drug loading content of 16.7 wt %. DM1-loaded HA-XPS (HA-XPS-DM1) presented a small size of ∼80 nm, low drug leakage under physiological conditions, and fast glutathione-triggered drug release. MTT assays revealed that HA-XPS was noncytotoxic while HA-XPS-DM1 was highly potent to MDA-MB-231 cells with an IC₅₀ comparable to that of free DM1. The in vitro and in vivo inhibition experiments indicated that HA-XPS could actively target MDA-MB-231 cells. Notably, HA-XPS-DM1 while causing little adverse effect could effectively inhibit tumor growth and significantly prolong survival time in MDA-MB-231 human breast tumor-bearing mice. HA-XPS-DM1 provides a novel and unique treatment for CD44-positive cancers.

EGFR-targeted multifunctional polymersomal doxorubicin induces selective and potent suppression of orthotopic human liver cancer in vivo

Liver cancer is a globally leading malignancy that has a poor five-year survival rate of less than 20%. The systemic chemotherapeutics are generally ineffective for liver cancers partly due to fast clearance and low tumor uptake. Here, we report that GE11 peptide functionalized polymersomal doxorubicin (GE11-PS-DOX) effectively targets and inhibits epidermal growth factor receptor (EGFR)-positive SMMC7721 orthotopic human liver tumor xenografts in mice. GE11-PS-DOX with a GE11 surface density of 10% displayed a high drug loading of 15.4 wt%, a small size of 78 nm, and glutathione-triggered release of DOX. MTT assays, flow cytometry and confocal microscopy studies revealed that GE11-PS-DOX mediated obviously more efficient DOX delivery into SMMC7721 cells than the non-targeting PS-DOX and clinically used liposomal doxorubicin (Lipo-DOX) controls. The in vivo studies showed that GE11-PS-DOX had a long circulation time and an extraordinary accumulation in the tumors (13.3 %ID/g). Interestingly, GE11-PS-DOX caused much better treatment of SMMC7721 orthotopic liver tumor-bearing mice as compared to PS-DOX and Lipo-DOX. The mice treated with GE11-PS-DOX (12 mg DOX equiv./kg) exhibited a significantly improved survival rate (median survival time: 130 days versus 70 and 38 days for PS-DOX at 12 mg DOX equiv./kg and Lipo-DOX at 6 mg DOX equiv./kg, respectively) and achieved 50% complete regression. Notably, GE11-PS-DOX induced obviously lower systemic toxicity than Lipo-DOX. EGFR-targeted multifunctional polymersomal doxorubicin with improved efficacy and safety has a high potential for treating human liver cancers.

STATEMENT OF SIGNIFICANCE

Liver cancer is one of the top five leading causes of cancer death worldwide. The systemic chemotherapeutics and biotherapeutics generally have a low treatment efficacy for hepatocellular carcinoma partly due to fast clearance and/or low tumor uptake. Nanomedicines based on biodegradable micelle and polymersomes offer a most promising treatment for malignant liver cancers. Their clinical effectiveness remains, however, suboptimal owing to issues like inadequate systemic stability, low tumor accumulation and selectivity, and poor control over drug release. Here we report that GE11 peptide-functionalized, disulfide-crosslinked multifunctional polymersomal doxorubicin (GE11-PS-DOX) can effectively suppress the growth of orthotopic SMMC7721 human liver tumors in nude mice. They showed significantly decreased systemic toxicity and improved mouse survival rate with 3.4-fold longer median survival time as compared to clinically used pegylated liposomal doxorubicin (Lipo-DOX) and achieving 50% complete regression. GE11-PS-DOX, based on PEG-PTMC is biodegradable, nontoxic, and easy to prepare, appears as a safe, robust, versatile and all-function-in-one nanoplatform that has a high potential in targeted chemotherapy of EGFR expressed hepatocellular carcinoma.

Dual-responsive core-crosslinked polyphosphoester-based nanoparticles for pH/redox-triggered anticancer drug delivery

"Intelligent" crosslinked nanoparticles (NPs) provide great advantages in enhancing drug bioavailability and reducing side effects in anticancer therapeutics. In this study, a novel biodegradable polyphosphoester-based functional copolymer prodrug PTX-(PBYP-g-MPA)-b-PEEP was prepared to construct pH/redox dual-responsive core-crosslinked nanoparticles (DOX/CCL NPs), in which paclitaxel (PTX) was conjugated to the polyphosphoester to form an amphiphilic prodrug and doxorubicin (DOX) was encapsulated inside the prodrug NPs. At first, PTX was used as an initiator to polymerize 2-(but-3-yn-1-yloxy)-2-oxo-1,3,2-dioxaphospholane (BYP) and 2-ethoxy-2-oxo-1,3,2-dioxaphospholane (EOP) by one-pot sequential ring-opening polymerization, yielding a biodegradable polymeric prodrug PTX-PBYP-b-PEEP. Subsequently, a radical-mediated thiol-yne "click" reaction was performed between the alkynyl groups on the PBYP segment and the thiol group of 3-mercaptopropionic acid (MPA) to form a functional carboxyl group at the side chain. The potential positively charged DOX·HCl can be physically encapsulated via electrostatic interaction with the carboxyl group and hydrophobic interaction. Afterwards, the DOX/CCL NPs with cleavable disulfide (S-S) linkages can be formed by partial crosslinking through amidation between the pendant carboxyl groups and cystamine. These NPs possess multifunctional characteristics used for in vitro drug release. Notably, a redox-responsive crosslinker, cystamine dihydrochloride, and synergetic non-covalent interactions not only stabilize the nanoparticles, achieve high DOX-loading capacity of drug loading content (DLC, 14.6%) and drug loading efficiency (DLE, 73.1%), but also endow the DOX/CCL NPs with controlled drug release capacity, which is due to the cleavage of S-S bonds in the presence of 10 mM glutathione (GSH) and weakened electrostatic interaction caused by the protonation of carboxyl groups at a lower pH (5.0). Moreover, these pH/redox dual-responsive DOX/CCL NPs can be steadily internalized by HeLa cells, exhibiting high-efficiency cellular proliferation inhibition. This study presents a promising strategy for controlled intracellular drug release in cancer therapy.

1,2-Dithiolane-Derived Dynamic, Covalent Materials: Cooperative Self-Assembly and Reversible Cross-Linking

The use of dithiolane-containing polymers to construct responsive and dynamic networks is an attractive strategy in material design. Here, we provide a detailed mechanistic study on the self-assembly and gelation behavior of a class of ABA triblock copolymers containing a central poly(ethylene oxide) block and terminal polycarbonate blocks with pendant 1,2-dithiolane functionalities. In aqueous solution, these amphiphilic block copolymers self-assemble into bridged flower micelles at high concentrations. The addition of a thiol initiates the reversible ring-opening polymerizations of dithiolanes in the micellar cores to induce the cross-linking and gelation of the micellar network. The properties of the resulting hydrogels depend sensitively on the structures of 1,2-dithiolanes. While the methyl asparagusic acid-derived hydrogels are highly dynamic, adaptable, and self-healing, those derived from lipoic acid are rigid, resilient, and brittle. The thermodynamics and kinetics of ring-opening polymerization of the two dithiolanes were investigated to provide important insights on the dramatically different properties of the hydrogels derived from the two different dithiolanes. The incorporation of both dithiolane monomers into the block copolymers provides a facile way to tailor the properties of these hydrogels.

Micellar nanoformulation of lipophilized bortezomib: high drug loading, improved tolerability and targeted treatment of triple negative breast cancer

Lipophilization of bortezomib with pinanediol enables efficacious drug loading and targeted tumor chemotherapy with reduction-sensitive self-crosslinked micellar systems.