Time-staggered delivery of docetaxel and H1-S6A,F8A peptide for sequential dual-strike chemotherapy through tumor priming and nuclear targeting

Structural information in therapeutic peptides: Emerging applications in biomedicine

Peptides are attracting a growing interest as therapeutic agents. This trend stems from their cost-effectiveness and reduced immunogenicity, compared to antibodies or recombinant proteins, but also from their ability to dock and interfere with large protein-protein interaction surfaces, and their higher specificity and better biocompatibility relative to organic molecules. Many tools have been developed to understand, predict, and engineer peptide function. However, most state-of-the-art approaches treat peptides only as linear entities and disregard their structural arrangement. Yet, structural details are critical for peptide properties such as solubility, stability, or binding affinities. Recent advances in peptide structure prediction have successfully addressed the scarcity of confidently determined peptide structures. This review will explore different therapeutic and biotechnological applications of peptides and their assemblies, emphasizing the importance of integrating structural information to advance these endeavors effectively.

MYC the oncogene from hell: Novel opportunities for cancer therapy

Cancer comprises a heterogeneous disease, characterized by diverse features such as constitutive expression of oncogenes and/or downregulation of tumor suppressor genes. MYC constitutes a master transcriptional regulator, involved in many cellular functions and is aberrantly expressed in more than 70 % of human cancers. The Myc protein belongs to a family of transcription factors whose structural pattern is referred to as basic helix-loop-helix-leucine zipper. Myc binds to its partner, a smaller protein called Max, forming an Myc:Max heterodimeric complex that interacts with specific DNA recognition sequences (E-boxes) and regulates the expression of downstream target genes. Myc protein plays a fundamental role for the life of a cell, as it is involved in many physiological functions such as proliferation, growth and development since it controls the expression of a very large percentage of genes (∼15 %). However, despite the strict control of MYC expression in normal cells, MYC is often deregulated in cancer, exhibiting a key role in stimulating oncogenic process affecting features such as aberrant proliferation, differentiation, angiogenesis, genomic instability and oncogenic transformation. In this review we aim to meticulously describe the fundamental role of MYC in tumorigenesis and highlight its importance as an anticancer drug target. We focus mainly on the different categories of novel small molecules that act as inhibitors of Myc function in diverse ways hence offering great opportunities for an efficient cancer therapy. This knowledge will provide significant information for the development of novel Myc inhibitors and assist to the design of treatments that would effectively act against Myc-dependent cancers.

Peptides as multifunctional players in cancer therapy

Peptides exhibit lower affinity and a shorter half-life in the body than antibodies. Conversely, peptides demonstrate higher efficiency in tissue penetration and cell internalization than antibodies. Regardless of the pros and cons of peptides, they have been used as tumor-homing ligands for delivering carriers (such as nanoparticles, extracellular vesicles, and cells) and cargoes (such as cytotoxic peptides and radioisotopes) to tumors. Additionally, tumor-homing peptides have been conjugated with cargoes such as small-molecule or chemotherapeutic drugs via linkers to synthesize peptide-drug conjugates. In addition, peptides selectively bind to cell surface receptors and proteins, such as immune checkpoints, receptor kinases, and hormone receptors, subsequently blocking their biological activity or serving as hormone analogs. Furthermore, peptides internalized into cells bind to intracellular proteins and interfere with protein-protein interactions. Thus, peptides demonstrate great application potential as multifunctional players in cancer therapy.

Functionalized Hybrid Iron Oxide-Gold Nanoparticles Targeting Membrane Hsp70 Radiosensitize Triple-Negative Breast Cancer Cells by ROS-Mediated Apoptosis

Triple-negative breast cancer (TNBC) a highly aggressive tumor entity with an unfavorable prognosis, is treated by multimodal therapies, including ionizing radiation (IR). Radiation-resistant tumor cells, as well as induced normal tissue toxicity, contribute to the poor clinical outcome of the disease. In this study, we investigated the potential of novel hybrid iron oxide (Fe₃O₄)-gold (Au) nanoparticles (FeAuNPs) functionalized with the heat shock protein 70 (Hsp70) tumor-penetrating peptide (TPP) and coupled via a PEG4 linker (TPP-PEG4-FeAuNPs) to improve tumor targeting and uptake of NPs and to break radioresistance in TNBC cell lines 4T1 and MDA-MB-231. Hsp70 is overexpressed in the cytosol and abundantly presented on the cell membrane (mHsp70) of highly aggressive tumor cells, including TNBCs, but not on corresponding normal cells, thus providing a tumor-specific target. The Fe₃O₄ core of the NPs can serve as a contrast agent enabling magnetic resonance imaging (MRI) of the tumor, and the nanogold shell radiosensitizes tumor cells by the release of secondary electrons (Auger electrons) upon X-ray irradiation. We demonstrated that the accumulation of TPP-PEG4-FeAuNPs into mHsp70-positive TNBC cells was superior to that of non-conjugated FeAuNPs and FeAuNPs functionalized with a non-specific, scrambled peptide (NGL). After a 24 h co-incubation period of 4T1 and MDA-MB-231 cells with TPP-PEG4-FeAuNPs, but not with control hybrid NPs, ionizing irradiation (IR) causes a cell cycle arrest at G2/M and induces DNA double-strand breaks, thus triggering apoptotic cell death. Since the radiosensitizing effect was completely abolished in the presence of the ROS inhibitor N-acetyl-L-cysteine (NAC), we assume that the TPP-PEG4-FeAuNP-induced apoptosis is mediated via an increased production of ROS.

Design and Characterization of a Cell-Penetrating Peptide Derived from the SOX2 Transcription Factor

SOX2 is an oncogenic transcription factor overexpressed in nearly half of the basal-like triple-negative breast cancers associated with very poor outcomes. Targeting and inhibiting SOX2 is clinically relevant as high SOX2 mRNA levels are positively correlated with decreased overall survival and progression-free survival in patients affected with breast cancer. Given its key role as a master regulator of cell proliferation, SOX2 represents an important scaffold for the engineering of dominant-negative synthetic DNA-binding domains (DBDs) that act by blocking or interfering with the oncogenic activity of the endogenous transcription factor in cancer cells. We have synthesized an interference peptide (iPep) encompassing a truncated 24 amino acid long C-terminus of SOX2 containing a potential SOX-specific nuclear localization sequence, and the determinants of the binding of SOX2 to the DNA and to its transcription factor binding partners. We found that the resulting peptide (SOX2-iPep) possessed intrinsic cell penetration and promising nuclear localization into breast cancer cells, and decreased cellular proliferation of SOX2 overexpressing cell lines. The novel SOX2-iPep was found to exhibit a random coil conformation predominantly in solution. Molecular dynamics simulations were used to characterize the interactions of both the SOX2 transcription factor and the SOX2-iPep with FGF4-enhancer DNA in the presence of the POU domain of the partner transcription factor OCT4. Predictions of the free energy of binding revealed that the iPep largely retained the binding affinity for DNA of parental SOX2. This work will enable the future engineering of novel dominant interference peptides to transport different therapeutic cargo molecules such as anti-cancer drugs into cells.

Emerging nanotaxanes for cancer therapy

The clinical application of taxane (including paclitaxel, docetaxel, and cabazitaxel)-based formulations is significantly impeded by their off-target distribution, unsatisfactory release, and acquired resistance/metastasis. Recent decades have witnessed a dramatic progress in the development of high-efficiency, low-toxicity nanotaxanes via the use of novel biomaterials and nanoparticulate drug delivery systems (nano-DDSs). Thus, in this review, the achievements of nanotaxanes-targeted delivery and stimuli-responsive nano-DDSs-in preclinical or clinical trials have been outlined. Then, emerging nanotherapeutics against tumor resistance and metastasis have been overviewed, with a particular emphasis on synergistic therapy strategies (e.g., combination with surgery, chemotherapy, radiotherapy, biotherapy, immunotherapy, gas therapy, phototherapy, and multitherapy). Finally, the latest oral nanotaxanes have been briefly discussed.

A sonosensitiser-based polymeric nanoplatform for chemo-sonodynamic combination therapy of lung cancer

BACKGROUND

Lung cancer is the most common type of tumour worldwide. Its relative lethality is considerably high. However, since the tumour tissues are located deep within the human body, traditional technologies, such as photodynamic therapy, do not have the desired effect. Sonosensitisers can penetrate deeply into tissues, and sonodynamic therapy (SDT) effectively inhibits tumours by generating reactive oxygen species. Ultrasound can also penetrate deeply, with a favourable tumour inhibition effect.

RESULTS

A redox/ultrasound-responsive Rhein-chondroitin sulphate-based nano-preparation encapsulating docetaxel was fabricated. The nanoparticles displayed increased cellular uptake with quick drug release, good stability, and a monodispersed form in the physiological environment. Rhein induced apoptosis and altered mitochondrial membrane potential, which enhanced the expression of apoptosis-related proteins. SDT inhibited the metastasis and angiogenesis of cancer cells and activated anti-tumour capacity by reducing the expression of M2 macrophages.

CONCLUSIONS

The potential of Rhein for SDT was demonstrated. Production of reaction oxygen species was markedly enhanced after ultrasound treatment. The nanoplatform enhanced the synergistic anti-tumour effects of SDT and chemotherapeutic efficacy. The approach was biocompatibility. The findings could inform investigations of chemo-SDT for different cancers.

Polymer nanomedicines

Polymer nanomedicines (macromolecular therapeutics, polymer-drug conjugates, drug-free macromolecular therapeutics) are a group of biologically active compounds that are characterized by their large molecular weight. This review focuses on bioconjugates of water-soluble macromolecules with low molecular weight drugs and selected proteins. After analyzing the design principles, different structures of polymer carriers are discussed followed by the examination of the efficacy of the conjugates in animal models and challenges for their translation into the clinic. Two innovative directions in macromolecular therapeutics that depend on receptor crosslinking are highlighted: a) Combination chemotherapy of backbone degradable polymer-drug conjugates with immune checkpoint blockade by multivalent polymer peptide antagonists; and b) Drug-free macromolecular therapeutics, a new paradigm in drug delivery.

Chitosan Hydrogels for Synergistic Delivery of Chemotherapeutics to Triple Negative Breast Cancer Cells and Spheroids

PURPOSE

This study aimed to develop a hydrogel system for treating aggressive triple negative breast cancer (TNBC) via kinetically-controlled delivery of the synergistic drug pair doxorubicin (DOX) and gemcitabine (GEM). A 2D assay was adopted to evaluate therapeutic efficacy by determining combination index (CI), and a 3D assay using cancer spheroids was implemented to assess the potential for translation in vivo.

METHODS

The release of DOX and GEM from an acetylated-chitosan (ACS, degree of acetylation χAc = 40 ± 5%) was characterized to identify a combined drug loading that affords release kinetics and dose that are therapeutically synergistic. The selected DOX/GEM-ACS formulation was evaluated in vitro with 2-D and 3-D models of TNBC to determine the combination index (CI) and the tumor volume reduction, respectively.

RESULTS

Therapeutically desired release dosages and kinetics of GEM and DOX were achieved. When evaluated with a 2-D model of TNBC, the hydrogel afforded a CI of 0.14, indicating a stronger synergism than concurrent administration of DOX and GEM (CI = 0.23). Finally, the therapeutic hydrogel accomplished a notable volume reduction of the cancer spheroids (up to 30%), whereas the corresponding dosages of free drugs only reduced growth rate.

CONCLUSIONS

The ACS hydrogel delivery system accomplishes drug release kinetics and molar ratio that affords strong therapeutically synergism. These results, in combination with the choice of ACS as affordable and highly abundant source material, provide a strong pre-clinical demonstration of the potential of the proposed system for complementing surgical resection of aggressive solid tumors.

Modified gaphene oxide (GO) particles in peptide hydrogels: a hybrid system enabling scheduled delivery of synergistic combinations of chemotherapeutics

The scheduled delivery of synergistic drug combinations is increasingly recognized as highly effective against advanced solid tumors. Of particular interest are composite systems that release a sequence of drugs with defined kinetics and molar ratios to enhance therapeutic effect, while minimizing the dose to patients. In this work, we developed a homogeneous composite comprising modified graphene oxide (GO) nanoparticles embedded in a Max8 peptide hydrogel, which provides controlled kinetics and molar ratios of release of doxorubicin (DOX) and gemcitabine (GEM). First, modified GO nanoparticles (tGO) were designed to afford high DOX loading and sustained release (18.9% over 72 h and 31.4% over 4 weeks). Molecular dynamics simulations were utilized to model the mechanism of DOX loading as a function of surface modification. In parallel, a Max8 hydrogel was developed to release GEM with faster kinetics and achieve a 10-fold molar ratio to DOX. The selected DOX/tGO nanoparticles were suspended in a GEM/Max8 hydrogel matrix, and the resulting composite was tested against a triple negative breast cancer cell line, MDA-MB-231. Notably, the composite formulation afforded a combination index of 0.093 ± 0.001, indicating a much stronger synergism compared to the DOX-GEM combination co-administered in solution (CI = 0.396 ± 0.034).

Precision medicine by designer interference peptides: applications in oncology and molecular therapeutics

In molecular cancer therapeutics only 10% of known cancer gene products are targetable with current pharmacological agents. Major oncogenic drivers, such as MYC and KRAS proteins are frequently highly overexpressed or mutated in multiple human malignancies. However, despite their key role in oncogenesis, these proteins are hard to target with traditional small molecule drugs due to their large, featureless protein interfaces and lack of deep pockets. In addition, they are inaccessible to large biologicals, which are unable to cross cell membranes. Designer interference peptides (iPeps) represent emerging pharmacological agents created to block selective interactions between protein partners that are difficult to target with conventional small molecule chemicals or with large biologicals. iPeps have demonstrated successful inhibition of multiple oncogenic drivers with some now entering clinical settings. However, the clinical translation of iPeps has been hampered by certain intrinsic limitations including intracellular localization, targeting tissue specificity and pharmacological potency. Herein, we outline recent advances for the selective inhibition of major cancer oncoproteins via iPep approaches and discuss the development of multimodal peptides to overcome limitations of the first generations of iPeps. Since many protein–protein interfaces are cell-type specific, this approach opens the door to novel programmable, precision medicine tools in cancer research and treatment for selective manipulation and reprogramming of the cancer cell oncoproteome.

Overcoming chemotherapy resistance via simultaneous drug-efflux circumvention and mitochondrial targeting

Multidrug resistance (MDR) has been considered as a huge challenge to the effective chemotherapy. Therefore, it is necessary to develop new strategies to effectively overcome MDR. Here, based on the previous research of N-(2-hydroxypropyl)methacrylamide (HPMA) polymer–drug conjugates, we designed an effective system that combined drug-efflux circumvention and mitochondria targeting of anticancer drug doxorubicin (Dox). Briefly, Dox was modified with mitochondrial membrane penetrating peptide (MPP) and then attached to (HPMA) copolymers (P-M-Dox). Our study showed that macromolecular HPMA copolymers successfully bypassed drug efflux pumps and escorted Dox into resistant MCF-7/ADR cells via endocytic pathway. Subsequently, the mitochondria accumulation of drugs was significantly enhanced with 11.6-fold increase by MPP modification. The excellent mitochondria targeting then resulted in significant enhancement of reactive oxygen species (ROS) as well as reduction of adenosine triphosphate (ATP) production, which could further inhibit drug efflux and resistant cancer cell growth. By reversing Dox resistance, P-M-Dox achieved much better suppression in the growth of 3D MCF-7/ADR tumor spheroids compared with free Dox. Hence, our study provides a promising approach to treat drug-resistant cancer through simultaneous drug efflux circumvention and direct mitochondria delivery.

Bioactive cell penetrating peptides and proteins in cancer: a bright future ahead

Peptides and proteins bear an extraordinary therapeutic potential to effectively and selectively target many components of cells currently considered undruggable. However, their intracellular delivery remains a critical challenge. Cell penetrating peptides and protein domains (CPPs) can be employed to translocate therapeutic polypeptides through the cellular membrane. Here, we describe examples of linear peptides and proteins, byciclic macropeptides and nanobodies that target key players in cancer development, with intrinsic and engineered cell penetrating ability. We also describe current solutions to the main challenges to their clinical viability.

Drug-free albumin-triggered sensitization of cancer cells to anticancer drugs

Chemosensitization strategies have been used to sensitize cancer cells to conventional drugs, but their utility is often obstructed by additional off-target toxicity, limited access to intracellular targets and heterogeneous tumor pathogenesis. To address these challenges, we rationally developed a drug-free human serum albumin (HSA)-based therapeutic (KH-1) that functions extracellularly and exhibits pleiotropic effect on multiple intracellular signaling pathways. It is a two-step touch-trigger system that consists of a pretargeting anchor on surface receptor CD20 (anti-CD20 Fab' conjugated with a morpholino oligonucleotide 1) and a CD20 clustering actuator (HSA grafted with multiple copies of complementary morpholino oligonucleotide 2). The extracellular actuation by surface CD20 crosslinking boosts robust activations of numerous intracellular responses, and promotes cancer cell susceptibility to various anticancer drugs, including docetaxel (microtubule stabilizer), gemcitabine (nucleoside analogue) and GDC-0980 (PI3K/mTOR inhibitor). The broad applicability of KH-1 is demonstrated to result from simultaneous inhibition of survival pathways and augmentation of apoptotic pathways. In addition, KH-1 covalently conjugated with anthracycline anticancer agent, epirubicin, integrates the advantages of both chemosensitization function and improved intracellular drug delivery in a single system and takes effect on the same cell. Therefore, in the present study, we have provided mechanistic demonstration that crosslinking of surface receptors can be leveraged to elicit chemosensitization.

Drug-free macromolecular therapeutics exhibit amplified apoptosis in G2/M phase arrested cells

Drug-free macromolecular therapeutics (DFMT) have been recently developed to treat non-Hodgkin lymphoma (NHL). It is a consecutive delivery of two nanoconjugates: (1) bispecific engager that pretargets surface CD20, and (2) multivalent effector polymer that hybridises with CD20-bound engagers. Without the need of low molecular weight drug, the hybridisation of morpholino oligonucleotide containing DFMT at NHL cell surface triggers CD20 crosslinking and subsequent apoptosis. We have previously determined various factors that affect the efficacy of DFMT regarding the synthetic structures. Here, we show that DFMT-mediated apoptosis is also influenced by the state of cells. Compared with other cell cycle states, cells arrested at G2/M phase exhibit enhanced CD20 expression, and have more sustainable CD20 binding by DFMT, resulting in a higher degree of DFMT-mediated CD20 crosslinking. Moreover, the anti-apoptotic Bcl-2 protein was phosphorylated in G2/M phase, thereby increasing the cell susceptibility to DFMT. As a result, DFMT mediated augmented apoptosis in G2/M phase cells. When DFMT was combined with a polymer-docetaxel conjugate that triggered G2/M blockage, a combinatorial apoptotic effect was achieved to induce programmed cell death. Our findings suggest the co-delivery of DFMT and G2/M inhibiting drug combinations may present a therapeutic advantage in NHL treatment.

Improved anticancer efficacy of doxorubicin mediated by human-derived cell-penetrating peptide dNP2

Although cell penetrating peptides (CPPs) have been extensively studied as an approach to deliver anti-cancer drugs into the tumor cells for the last 30 years, no FDA-approved CPP-based drugs are available, implying that the existing CPPs may have less efficiency in human or have side effects such as toxicity. Herein, we established a tumor targeting drug delivery system by attaching a human-derived cell-penetrating peptide dNP2 (CKIKKVKKKGRKKIKKVKKKGRK) to N-(2-hydroxypropyl)-methacrylamide (HPMA) copolymer doxorubicin conjugates. Firstly, in vitro cytotoxicity of free dNP2 peptide and dNP2-modified blank HPMA copolymer were examined. A classic CPP-R8 (CRRRRRRRR) was chosen for comparison and the results showed that 200 μM free R8 reduced cell viability to 68.4% but dNP2 did not induce any toxicity at the same concentration. After conjugation to HPMA copolymer, a similar trend was also observed which indicated the excellent biocompatibility of dNP2. Next, effect of dNP2 modification on cellular uptake, DNA damage, apoptosis and anticancer activity of HPMA copolymer doxorubicin conjugates were evaluated. It was excited that dNP2 modified HPMA copolymer (P-(dNP2)-DOX) not only had a higher uptake by HeLa cell compared with non-modified copolymer (P-DOX) but resulted in an enhanced drug distribution in nuclei. Furthermore, P-(dNP2)-DOX exhibited greater DNA damage ability (10.5 folds higher than P-DOX) in comet assay and induced more apoptosis cells (46.0%). P-(dNP2)-DOX also showed a stronger cell cytotoxicity (3-fold to P-DOX) as well as in 3D tumor spheroid assay (inhibition rate 78%). All these results suggested that the human-derived cell-penetrating peptide dNP2 could facilitate tumor nuclear-accumulation of anti-cancer drugs and improve anticancer efficacy. More importantly, dNP2 has less toxicity compared with classic CPP-R8 thus shows the potential for the clinic cancer therapy.

Enhanced nuclear delivery of anti-cancer drugs using micelles containing releasable membrane fusion peptide and nuclear-targeting retinoic acid

Biodegradable cross-linked N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer micelles can improve the accumulation of drug cargo in tumors by prolonging their circulation time. However, drug delivery can still be ineffective because of intracellular degradation in lysosomes and poor delivery to the nucleus. In this work, we prepared a novel micelle by grafting the hydrophobic HA2 membrane fusion peptide onto hydrophilic HPMA copolymers via a linker that would be cleaved in lysosomes, allowing the HA2 peptide to be released and disrupt lysosome membranes. In addition, we conjugated the drug cargo (H1 peptide) to nucleus-targeting all-trans retinoic acid, and then encapsulated the conjugates into micelles. The drug-loaded micelles efficiently escaped lysosomes and targeted the nucleus in MCF-7 breast cancer cells in culture. They also strongly inhibited tumor growth in mice bearing MCF-7 tumor xenografts, without causing appreciable systemic toxicity. Removing the retinoic acid or preventing the cleavage of HA2 resulted in extremely inefficient lysosomal escape and nuclear delivery, translating into low anti-cancer efficacy in vitro and in vivo. These results suggest that micelle modifications to evade lysosomes and target the nucleus can improve the efficacy of anti-cancer drugs. Our results further suggest that the ability to escape lysosomes improves the nuclear distribution of drug cargos more than the addition of the nuclear-targeting retinoic acid.

Drug-Free Macromolecular Therapeutics Induce Apoptosis via Calcium Influx and Mitochondrial Signaling Pathway

Recently, an innovative paradigm has been proposed in macromolecular therapeutics for treatment of B-cell lymphomas that can specifically kill cancer cells without a drug. The design rationale of this drug-free macromolecular therapeutic (DFMT) system is crosslinking the cell surface receptor to initiate apoptosis. However, how the apoptosis signal is triggered after receptor hyper-crosslinking remains to be elucidated. Here, two pathways, calcium influx dependent pathway and mitochondrial signal pathway, are identified to play major roles in triggering the programmed cell death. With the first step pretargeting and second step multiple binding, receptor hyper-crosslinking is achieved in a highly specific, time-dependent manner and largely mediated by multivalence. As a consequence, extracellular calcium influx is triggered, which subsequently decreases the mitochondrial membrane potential and induces apoptosis. The mitochondrial depolarization also stems from the Bcl-2 inhibition mediated by DFMT, followed by the cytochrome c release that activates caspase signaling. With the participation of the two-pronged mechanism, a programmed apoptosis is induced in response to DFMT treatment. The current findings can offer important implications to optimize the anti-CD20 strategies to treat B-cell non-Hodgkin lymphomas.

Two birds, one stone: dual targeting of the cancer cell surface and subcellular mitochondria by the galectin-3-binding peptide G3-C12

Active tumor-targeting approaches using specific ligands have drawn considerable attention over the years. However, a single ligand often fails to simultaneously target the cancer cell surface and subcellular organelles, which limits the maximum therapeutic efficacy of delivered drugs. We describe a polymeric delivery system modified with the G3-C12 peptide for sequential dual targeting. In this study, galectin-3-targeted G3-C12 peptide was conjugated onto the N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer for the delivery of _D(KLAKLAK)₂ (KLA) peptide. G3-C12-HPMA-KLA exhibited increased receptor-mediated internalization into galectin-3-overexpressing PC-3 cells. Furthermore, G3-C12 peptide also directed HPMA-KLA conjugates to mitochondria. This occurred because the apoptosis signal triggered the accumulation of galectin-3 in mitochondria, and the G3-C12 peptide that specifically bound to galectin-3 was trafficked along with its receptor intracellularly. As a result, G3-C12-HPMA-KLA disrupted the mitochondrial membrane, increased the generation of reactive oxygen species (ROS) and induced cytochrome c release, which ultimately resulted in enhanced cytotoxicity. An in vivo study revealed that the G3-C12 peptide significantly enhanced the tumor accumulation of the KLA conjugate. In addition, G3-C12-HPMA-KLA exhibited the best therapeutic efficacy and greatly improved the animal survival rate. Our work demonstrates that G3-C12 is a promising ligand with dual-targeting functionality.

Strategies to Inhibit Myc and Their Clinical Applicability

Myc is an oncogene deregulated in most-perhaps all-human cancers. Each Myc family member, c-, L-, and N-Myc, has been connected to tumor progression and maintenance. Myc is recognized as a "most wanted" target for cancer therapy, but has for many years been considered undruggable, mainly due to its nuclear localization, lack of a defined ligand binding site, and physiological function essential to the maintenance of normal tissues. The challenge of identifying a pharmacophore capable of overcoming these hurdles is reflected in the current absence of a clinically-viable Myc inhibitor. The first attempts to inhibit Myc used antisense technology some three decades ago, followed by small molecule inhibitors discovered through "classical" compound library screens. Notable breakthroughs proving the feasibility of systemic Myc inhibition were made with the Myc dominant negative mutant Omomyc, showing both the great promise in targeting this infamous oncogene for cancer treatment as well as allaying fears about the deleterious side effects that Myc inhibition might have on normal proliferating tissues. During this time many other strategies have appeared in an attempt to drug the undruggable, including direct and indirect targeting, knockdown, protein/protein and DNA interaction inhibitors, and translation and expression regulation. The inhibitors range from traditional small molecules to natural chemicals, to RNA and antisense, to peptides and miniproteins. Here, we briefly describe the many approaches taken so far, with a particular focus on their potential clinical applicability.

Subcellular co-delivery of two different site-oriented payloads for tumor therapy

Co-delivery of multiple agents via nanocarriers is of great interest in cancer therapy, but subcellular delivery to the corresponding site of action remains challenging. Here we report a smart nanovehicle which enables two different site-oriented payloads to reach their targeted organelles based on stimulus-responsive release and nucleus-targeted modification. First, all trans retinoic acid (RA) conjugated camptothecin (RA-CPT) was loaded in a polyhedral oligomericsilsesquioxane (POSS)-based core; docetaxel (DTX) was grafted on N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers. The POSS core grafted with semitelechelic HPMA copolymers then self-assembled into micelles. Once internalized into the cell, the two drugs were unleashed environment-responsively, and nuclear targeted RA remarkably facilitated the nuclear transport of CPT. Compared with single drug-loaded micelles, the dual drug-loaded platform showed superior synergic cytotoxicity, which was further strengthened by the involvement of RA. The ability to induce DNA damage and apoptosis was also enhanced by nucleus-targeted modification. Finally, dual drug-loaded micelles exhibited much better in vivo tumor inhibition (87.1%) and less systemic toxicity than the combination of single drug-loaded systems or the dual drug-loaded micelles without RA. Therefore, our study provides a novel "one platform, two targets" strategy in combinatory anti-cancer therapy.

Organic nanoparticle systems for spatiotemporal control of multimodal chemotherapy

INTRODUCTION

Chemotherapeutic drugs are used in combination to target multiple mechanisms involved in cancer cell survival and proliferation. Carriers are developed to deliver drug combinations to common target tissues in optimal ratios and desirable sequences. Nanoparticles (NP) have been a popular choice for this purpose due to their ability to increase the circulation half-life and tumor accumulation of a drug. Areas covered: We review organic NP carriers based on polymers, proteins, peptides, and lipids for simultaneous delivery of multiple anticancer drugs, drug/sensitizer combinations, drug/photodynamic therapy or drug/photothermal therapy combinations, and drug/gene therapeutics with examples in the past three years. Sequential delivery of drug combinations, based on either sequential administration or built-in release control, is introduced with an emphasis on the mechanistic understanding of such control. Expert opinion: Recent studies demonstrate how a drug carrier can contribute to co-localizing drug combinations in optimal ratios and dosing sequences to maximize the synergistic effects. We identify several areas for improvement in future research, including the choice of drug combinations, circulation stability of carriers, spatiotemporal control of drug release, and the evaluation and clinical translation of combination delivery.