Novel angiogenesis inhibitors with superoxide anion radical amplification effect: Surmounting the Achilles' heels of angiogenesis inhibitors and photosensitizers

Angiogenesis inhibitors and photosensitizers are pivotal in tumor clinical treatment, yet their utilization is constrained. Herein, eleven novel angiogenesis inhibitors were developed through hybridization strategy to overcome their clinical limitations. These title compounds boast excitation wavelengths within the "therapeutic window", enabling deep tissue penetration. Notably, they could generate superoxide anion radicals via the Type I mechanism, with compound 36 showed the strongest superoxide anion radical generating capacity. Biological evaluation demonstrated remarkable cellular activity of all the title compounds, even under hypoxic conditions. Among them, compound 36 stood out for its superior anti-proliferative activity in both normoxic and hypoxic environments, surpassing individual angiogenesis inhibitors and photosensitizers. Compound 36 induced cell apoptosis via superoxide anion radical generation, devoid of dark toxicity. Molecular docking revealed that the target-recognizing portion of compound 36 was able to insert into the ATP binding pocket of the target protein similar to sorafenib. Collectively, our results suggested that hybridization of angiogenesis inhibitors and photosensitizers was a potential strategy to address the limitations of their clinical use.

The influence of a modified p53 C-terminal peptide by using a tumor-targeting sequence on cellular apoptosis and tumor treatment

The restoration of the function of p53 in tumors is a therapeutic strategy for the highly frequent mutation of the TP53 tumor suppressor gene. P460 is a wild-type peptide derived from the p53 C-terminus and has been proven to be capable of restoring the tumor suppressor function of p53. The poor accumulation of drugs in tumors is a serious hindrance to tumor treatment. For enhancing the activity of P460, the tumor-targeting sequence Arg-Gly-Asp-Arg (RGDR, C-end rule peptide) was introduced into the C-terminus of P460 to generate the new peptide P462. P462 presented better activity than P460 in inhibiting the proliferation of cancer cells and increasing the number of tumor cells undergoing apoptosis. Cell adhesion analysis and tumor imaging results revealed that P462 showed more specific and extensive binding with tumor cells and greater accumulation in tumors than the wild-type peptide. Importantly, treatment with P462 was more efficacious than that with P460 in vivo and was associated with considerably improved tumor-homing activity. This study highlights the importance of the roles of the tumor-homing sequence RGDR in the enhancement in cell attachment and tumor accumulation. The results of this work indicate that P462 could be a novel drug candidate for tumor treatment.

Fabrication of hyaluronic acid-altered gold complex delivery for head and neck squamous cell carcinoma therapy with high antitumor efficacy and low in vivo toxicity

The use of multifunctional nanomedicines in the treatment of tumors is gaining popularity. Here, we constructed a nanodrug delivery system (HA/Au-PDA@CZT) that targets tumors and responds to pH and near-infrared (NIR) dual stimuli. By precisely interacting with an overexpressed CD44 receptor in specific cancer cells, hyaluronic acid (HA) is coated on the Au-PDA NP surface for tumor-targeting abilities. When exposed to NIR radiation, polydopamine (PDA) and gold nanoshells exhibit exceptional photothermal performance that has the potential to both accelerate and kill HLAC 78 head and neck squamous cell carcinoma cells. Antitumor investigations conducted in vivo and in vitro demonstrated that nanomedicine had remarkable synergistic benefits with chemotherapy and photothermal treatment. Only 25.2% of the cells in the HA/Au-PDA@CZT with a NIR irradiation group were viable. Any group's lowest tumor volume was shown in the tumor mice subjected to HA/Au-PDA@CZT with NIR at 0.3 ± 0.1. Consequently, for synergistic chemo-photothermal therapy, our logically designed nanoplatform would be the potential for a head and neck squamous tumor-targeting drug delivery system.

Biomimetic exosomal vesicles loaded with siRNA improves antitumor immune responses by inhibiting the secretion of tumor-derived exosome PD-L1

Tumor-derived exosome PD-L1 exhaustsTcells and permits tumor cells to evade immune surveillance; thus, the inhibition of ExoPD-L1 secretion can significantly enhance the clinical efficacy of PD-L1 antibody. In this study, we combined exosome membrane, apoA1 and phospholipid into biomimetic exosome vesicles (apoA1-bExo) which were then incubated with cholesterol modified siRNA to generate apoA1-bExo containing siRNA (apoA1-bExo/siRNA). Thepreparedvesicleswere uniformandsphericalin size and could be loaded effectively with siRNA to protect from nuclease degradation. Compared with bExo/siRNA, apoA1-bExo/siRNA showed stronger tumor targeting, tissue permeability, intracellular accumulation efficiency and antitumor efficiency. A portion of apoA1-bExo/siRNA transport siRNA occurred through the endosome-Golgi-ER pathway similar to bExo/siRNA, but mostly occurred directly through selective uptake pathways mediated by the SR-B1 receptor. apoA1-bExo/siRNA successfully achieved silencing efficiency at the transcription and protein levels (96.78 % and 94.07 %, respectively) and reduced the secretion of ExoPD-L1 from HepG2 cells to 15.92 % of that in the PBS group, thus enhancing the killing activity of co-cultured T cells on HepG2 cells. In addition, relevant pharmacodynamic indices were positively correlated with delivery efficiency and the modification of apoA1 could significantly enhance the intracellular accumulation of siRNA, thus exhibiting stronger activity than bExo/siRNA. Moreover, in addition to curing mice of their implanted tumors, blocking ExoPD-L1 secretion in combination with αPD-1 promoted the infiltration of durable antitumor hCD8+ T cells and hCD45+ T cells into tumor in a immune system-tumor dual humanized mice.

Photo-induced crosslinked and anti-PD-L1 peptide incorporated liposomes to promote PD-L1 multivalent binding for effective immune checkpoint blockade therapy

Immune checkpoint blockade (ICB) therapy targeting PD-L1 via monoclonal antibody (mAb) has shown extensive clinical benefits in the diverse types of advanced malignancies. However, most patients are completely refractory to ICB therapy owing to the PD-L1 recycling mechanism. Herein, we propose photo-induced crosslinked and anti-PD-L1 peptide incorporated liposomes (immune checkpoint blockade liposomes; ICB-LPs) to promote PD-L1 multivalent binding for inducing lysosomal degradation of PD-L1 in tumor cells. The ICB-LPs are prepared by formulation of DC8,9PC with photo-polymerized diacetylenic moiety, 1,2-dipalmitoylphosphatidylcholine (DPPC) and anti-PD-L1 peptide (D-form NYSKPTDRQYHF)-conjugated DSPE-PEG2k (anti-PD-L1-DSPE-PEG2k) in a molar ratio of 45:45:10, followed by cross-linking of liposomal bilayer upon UV irradiation. The 10 mol% anti-PD-L1-DSPE-PEG2k incorporated ICB-LPs have a nano-sized lipid bilayer structure with an average diameter of 137.7 ± 1.04 nm, showing a high stability in serum condition. Importantly, the ICB-LPs efficiently promote the multivalent binding with PD-L1 on the tumor cell membrane, which are endocytosed with aim to deliver PD-L1 to the lysosomes, wherein the durable PD-L1 degradation is observed for 72 h, in contrast to anti PD-L1 mAbs showing the rapid PD-L1 recycling within 9 h. The in vitro co-culture experiments with CD8+ T cells show that ICB-LPs effectively enhance the T cell-mediated antitumor immune responses against tumor cells by blocking the PD-L1/PD-1 axis. When ICB-LPs are intravenously injected into colon tumor-bearing mice, they efficiently accumulate within the targeted tumor tissues via both passive and active tumor targeting, inducing a potent T cell-mediated antitumor immune response by effective and durable PD-L1 degradation. Collectively, this study demonstrates the superior antitumor efficacy of crosslinked and anti-PD-L1 peptide incorporated liposome formulation that promotes PD-L1 multivalent binding for trafficking of PD-L1 toward the lysosomes instead of the recycling endosomes.

Tumor-targeting hydroxyapatite nanoparticles for remodeling tumor immune microenvironment (TIME) by activating mitoDNA-pyroptosis pathway in cancer

In recent years, immunotherapy has emerged as a promising strategy for treating solid tumors, although its efficacy remains limited to a subset of patients. Transforming non-responsive "cold" tumor types into immuno-responsive "hot" ones is critical to enhance the efficacy of immune-based cancer treatments. Pyroptosis, a programmed cell death mechanism, not only effectively eliminates tumor cells but also triggers a potent inflammatory response to initiate anti-tumor immune activities. This sheds light on the potential of pyroptosis to sensitize tumors to immune therapy. Hence, it is urgent to explore and develop novel treatments (e.g., nanomedicines) which are capable of inducing pyroptosis. In this study, we constructed tumor-targeting nanoparticles (CS-HAP@ATO NPs) by loading atorvastatin (ATO) onto chondroitin sulfate (CS) modified hydroxyapatite (HAP) nanoparticles (CS-HAP). CS was strategically employed to target tumor cells, while HAP exhibited the capacity to release calcium ions (Ca2+) in response to the tumor microenvironment. Moreover, ATO disrupted the mitochondrial function, leading to intracellular energy depletion and consequential changes in mitochondrial membrane permeability, followed by the influx of Ca2+ into the cytoplasm and mitochondria. CS and HAP synergetically augmented mitochondrial calcium overload, inciting the production of substantial amount of reactive oxygen species (ROS) and the subsequent liberation of oxidized mitochondrial DNA (OX-mitoDNA). This intricate activation process promoted the assembly of inflammasomes, most notably the NLRP3 inflammasome, followed by triggering caspase-1 activation. The activated caspase-1 was able to induce gasderminD (GSDMD) protein cleavage and present the GSDM-N domain, which interacted with phospholipids in the cell membrane. Then, the cell membrane permeability was raised, cellular swelling was observed, and abundant cell contents and inflammatory mediators were released. Ultimately, this orchestrated sequence of events served to enhance the anti-tumor immunoresponse within the organism.

CD44-mediated tumor homing of hyaluronic acid nanogels for hypoxia-activated photodynamic therapy against tumor

In this study, unique hypoxia-activated hyaluronic acid nanogels (HANGs) were reported for CD44-targeted delivery of photosensitizers (chlorin e6, Ce6) for diagnostic imaging and photodynamic therapy (PDT) of cancers. Through the use of a hypoxia-responsive cross-linker (AZO-CDI), the HANGs were prepared by chemically cross-linking primary amine groups-functionalized hyaluronic acid (HA). Under normoxic condition, fluorescence of Ce6 conjugated on the HANGs was highly quenched, and level of reactive oxygen species (ROS) generated from the HANGs was rather low after laser irradiation. However, under hypoxic condition, the HANGs underwent rapid disassociation, and fluorescence of Ce6 conjugated on the HANGs was recovered, triggering high-level singlet oxygen generation after laser irradiation. Due to the presence of HA, the HANGs showed much higher cellular uptake by CD44-positive cancer cells (A549 cells) than that by CD44-negative cancer cells (HepG2 cells). In addition, the HANGs could generate higher level of ROS in A549 cells because of improved cancer cell uptake. This excellent tumor-targeting and singlet oxygen-generating ability of the HANGs was favorable to hypoxia-activated PDT of CD44-positive cancers with significant inhibition of tumor growth within the whole treatment period. Taken together, the HANGs are safe and effective tools in treating CD44-positive cancers.

Discovery of intracellular self-assembly protein degraders driven by tumor-specific activatable bioorthogonal reaction

Proteolysis Targeting Chimera (PROTAC) is a type of bifunctional chimeric molecule that can directly degrade the binding proteins through the ubiquitin-proteasome pathway. PROTAC has shown great potential in overcoming drug resistance and targeting undruggable targets. However, there are still many shortcomings that need to be solved urgently, including worse membrane permeability and bioavailability induced by their large molecular weight. Herein, we used intracellular self-assembly strategy to construct tumor-specific PROTACs via small molecular precursors. We developed two types of precursors incorporated with azide and alkyne as biorthogonal groups, respectively. These small precursors with improved membrane permeability could react facilely with each other under the catalysis of copper ions with high concentration in tumor tissues, affording novel PROTACs. These novel intracellular self-assembled PROTACs could effectly induce degradation of VEGFR-2 and EphB4 in U87 cells. Meanwhile, they could also promote apoptosis and block cells in S phase. These tumor-specific intracellular self-assembled PROTACs exhibited high selectivity due to the high concentration of copper content in tumor tissue. Moreover, this new strategy could reduce the molecular weight of PROTACs, as well as improve the membrane permeability. These results will greatly expand the applications of bioorthogonal reaction in discovery of novel PROTACs.

Tumor-Targeting Extracellular Vesicles Loaded with siS100A4 for Suppressing Postoperative Breast Cancer Metastasis

Introduction

S100A4 promotes the establishment of tumor microenvironment for malignant cancer cells, and knockdown of S100A4 can inhibit tumorigenesis. However, there is no efficient way to target S100A4 in metastatic tumor tissues. Here, we investigated the role of siS100A4-loaded iRGD-modified extracellular vesicles (siS100A4-iRGD-EVs) in postoperative breast cancer metastasis.

Methods

siS100A4-iRGD-EVs nanoparticles were engineered and analyzed using TEM and DLS. siRNA protection, cellular uptake, and cytotoxicity of EV nanoparticles were examined in vitro. Postoperative lung metastasis mouse model was created to investigate the tissue distribution and anti-metastasis roles of nanoparticles in vivo.

Results

siS100A4-iRGD-EVs protected siRNA from RNase degradation, enhanced the cellular uptake and compatibility in vitro. Strikingly, iRGD-modified EVs significantly increased tumor organotropism and siRNA accumulation in lung PMNs compared to siS100A4-EVs in vivo. Moreover, siS100A4-iRGD-EVs treatment remarkedly attenuated lung metastases from breast cancer and increased survival rate of mice through suppressing S100A4 expression in lung.

Conclusions

siS100A4-iRGD-EVs nanoparticles show more potent anti-metastasis effect in postoperative breast cancer metastasis mouse model.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-022-00757-5.

Anti-Claudin18.2-IL-21 fusion protein bifunctional molecule has more powerful anti-tumor effect and better safety

Antibody or antibody-like protein drugs related to tumor immunotherapy are now widely used. Here, we describe an antibody-fusion protein drug IMAB362-mIL-21 with mouse IL-21 (mIL-21) fused into the C-terminal domain of IMAB362 (a clinical antibody drug against Claudin18.2), that we expect can achieve tumor targeting and activate local anti-tumor immune response more effectively, while reducing the systemic side effects of individual cytokines. In vitro assays comparing the fusion protein IMAB362-mIL-21 to IMAB362 and mIL-21, IMAB362-mIL-21 was able to recognize its cognate antigen Claudin18.2 and natural receptor mIL-21R with similar binding affinities, mediate equivalent ADCC activity and activate IL-21R-mediated downstream signal pathway. In in vivo assays, IMAB362-mIL-21 produced stronger anti-tumor effects compared with IMAB362 or mIL-21 or their combination at equimolar concentrations. Moreover, according to routine blood indicators, mIL-21-Fc and the combined treatment group had significant decreases (P < 0.01) in red blood cells (RBC), hemoglobin (HGB) and hematocrit (HCT), while the IMAB362-mIL-21 group did not. The above results have shown that IMAB362-mIL-21 can produce better anti-tumor effects without obvious hematological toxicity, which is sufficient to show that this kind of antibody-cytokine protein has better application value than IMAB362 or IL-21 as single drugs or in combination. Therefore, this bifunctional molecule combined tumor-targeting and immune activation effectively and has good application prospects.

Perfluorooctylbromide-loaded fucoidan-chlorin e6 nanoparticles for tumor-targeted photodynamic therapy

Efficient delivery of a photosensitizer (PS) and oxygen to tumor tissue is critical for successful photodynamic therapy (PDT). For this purpose, we developed a fucoidan (Fu)-chlorin e6 (Ce6) nanoparticle (NP) containing perfluorooctylbromide (PFOB). Fu, a biopolymer derived from seaweed, made up the hydrophilic shell of the NP and provided specific targeting to tumor cells by P-selectin binding. Conjugation with the hydrophobic Ce6 enabled self-assembly and Ce6-generated cytotoxic reactive oxygen species to kill tumor cells upon laser irradiation. PF supplied oxygen to the hypoxic tumor tissue and increased the efficacy of the PDT. The developed Fu-Ce6-PF-NPs bound specifically to SCC7 tumor cells and killed them via a photodynamic effect on laser irradiation. High accumulation of the NPs in tumor tissue and improved tumor suppression by PDT were observed in SCC7 tumor-bearing mice. The overall data demonstrated the potential of Fu-Ce6-PF-NP as a tumor-targeting drug carrier for effective PDT.

Novel Self-Assembled Micelles With Increased Tumor Penetration and Anti-Tumor Efficiency Against Breast Cancer

PURPOSE

Recently, docetaxel (DTX) micelles based on retinoic acid derivative surfactants showed lower systemic toxicity and bioequivalence to polysorbate-solubilized docetaxel (Taxotere®) in a phase II clinical study. However, the poor stability of these surfactants in vitro and in vivo led to extremely harsh storage conditions with methanol, and the formed micelles were quickly disintegrated with rapid drug burst release in vivo. To further enhance the stability and accumulation in tumors of DTX micelles, a novel surfactant based on acitretin (ACMeNa) was synthesized and used to prepare DTX micelles to improve anti-tumor efficiency.

METHODS

Novel micelle-forming excipients were synthesized, and the micelles were prepared using the thin film hydration technique. The targeting effect in vitro, distribution in the tumor, and its mechanism were observed. Pharmacokinetics and anti-tumor effect were further investigated in rats and tumor-bearing female mice, respectively.

RESULTS

The DTX-micelles prepared with ACMeNa (ACM-DTX) exhibited a small size (21.9 ± 0.3 nm), 39% load efficiency, and excellent stability in vitro and in vivo. Long circulation time, sustained and steady accumulation, and strong penetration in the tumor were observed in vivo, contributing to a better anti-tumor effect and lower adverse effects.

CONCLUSIONS

The micelles formed by ACMeNa showed a better balance between anti-tumor and adverse effects. It is a promising system for delivering hydrophobic molecules for cancer therapy.

Calcium carbonate vaterite particles for drug delivery: Advances and challenges

The recent successful application of lipid-based nanoparticles as delivery vehicles in COVID-19 vaccines demonstrated the superior potential of nanoparticle-based technology for targeted drug delivery in biomedicine. Among novel, rapidly advancing delivery platforms, the inorganic nano/microparticles gradually reach new heights and attract well-deserved attention among scientists and clinicians. Calcium carbonate in its vaterite form is used as a biocompatible carrier for a progressively increasing number of biomedical applications. Its growing popularity is conferred by beneficial porosity of particles, high mechanical stability, biodegradability under certain physiological conditions, ability to provide a continuous steady release of bioactives, preferential safety profile, and low cost, which make calcium carbonate a suitable entity of highly efficacious formulations for controlled drug delivery and release. The focal point of the current review is the success of the recent vaterite applications in the delivery of various diagnostics and therapeutic drugs. The manuscript highlights the nuances of drug loading in vaterite particles, connecting it with particle morphology, size, and charge of the loaded molecules, payload concentration, mono- or multiple drug loading. The manuscript also depicts recent successful methods of increasing the loading capacity developed for vaterite carriers. In addition, the review describes the various administration routes for vaterite particles with bioactive payloads, which were reported in recent years. Special attention is given to the multi-drug-loaded vaterite particles ("molecular cocktails") and reports on their successful delivery in vitro and in vivo.

Active targeting redox-responsive mannosylated prodrug nanocolloids promote tumor recognition and cell internalization for enhanced colon cancer chemotherapy

Despite the diversified therapeutic approaches for malignant tumors, chemotherapy remains the backbone of current cancer treatment. However, conventional chemotherapeutics was found to be associated with deficient recognition of tumor, low uptake efficiency, insolubility, short circulation, poor biocompatibility and low therapeutic outcomes. Herein, the active targeting redox-responsive mannosylated prodrug nanocolloids (HM NCs) were constructed for enhanced chemotherapy of colon cancer. HM NCs were prepared by the covalent cross-linking of 10-hydroxycamptothecin (HCPT) and mannose (MAN) via a redox-responsive cross-linker containing disulfide bonds, and modified with a moderate amount of polyethylene glycol (PEG). The large amount of mannose contained in HM NCs could actively target overexpressed mannose receptors on the surface of cancer cells and enhance cancer cell internalization through mannose receptor-mediated endocytosis. Owing to the combination of active targeting and the enhanced permeability and retention (EPR) passive targeting, HM NCs could effectively accumulate in tumors and high glutathione (GSH) in tumor microenvironment triggered cleavage of redox-responsive bonds and precise drug release. HM NCs exhibited superior antitumor activity both in vitro and in vivo and appreciably extended the mouse survival rate with good biocompatibility. The innovative HM NCs are expected to be conducive to overcoming the limitations of conventional chemotherapy for colon cancer and providing more choices for future clinical translation. STATEMENT OF SIGNIFICANCE: Despite the enhanced permeability and retention effect, the passive targeting can be interfered with by the complex biologic barriers in the body. In this study, an active targeting system (HM NCs) was constructed by covalent cross-linking of mannose and anticancer drug 10-hydroxycamptothecin via redox-responsive disulfide bonds for enhanced colon cancer chemotherapy. Mannosylation could promote hydrophilia and stability for prolonged blood circulation. Mannose could promote tumor recognition and cell internalization via mannose receptor-mediated endocytosis. High glutathione level could trigger the redox-responsive release of anticancer drugs and further induce cell apoptosis via DNA damage. The HM NCs exhibited superior antitumor activity both in vitro and in vivo and appreciably extended the mouse survival rate with good biocompatibility.

Overcoming the obstacles of current photodynamic therapy in tumors using nanoparticles

Photodynamic therapy (PDT) has been applied in clinical treatment of tumors for a long time. However, insufficient supply of pivotal factors including photosensitizer (PS), light, and oxygen in tumor tissue dramatically reduces the therapeutic efficacy of PDT. Nanoparticles have received an influx of attention as drug carriers, and recent studies have demonstrated their promising potential to overcome the obstacles of PDT in tumor tissue. Physicochemical optimization for passive targeting, ligand modification for active targeting, and stimuli-responsive release achieved efficient delivery of PS to tumor tissue. Various trials using upconversion NPs, two-photon lasers, X-rays, and bioluminescence have provided clues for efficient methods of light delivery to deep tissue. Attempts have been made to overcome unfavorable tumor microenvironments via artificial oxygen generation, Fenton reaction, and combination with other chemical drugs. In this review, we introduce these creative approaches to addressing the hurdles facing PDT in tumors. In particular, the studies that have been validated in animal experiments are preferred in this review over proof-of-concept studies that were only performed in cells.

Surface functionalized biomimetic bioreactors enable the targeted starvation-chemotherapy to glioma

Altering the glucose supply and the metabolic pathways would be an intriguing strategy in starvation therapy toward cancers. Nevertheless, starvation therapy alone could be inadequate to eliminate tumor cells completely. Herein, a multifunctional bioreactor was fabricated for synergistic starvation-chemotherapy through embedding glucose oxidase (GOx) and doxorubicin (DOX) in the tumor targeting ligands (RGD) modified red blood cell membrane camouflaged metal-organic framework (MOF) nanoparticle (denoted as RGD-mGZD). Owing to the remarkable biointerfacing property, the designed RGD-mGZD could not only possess enhanced blood retention time inherited from red blood cells, but also preferentially target the tumor site after the modification with RGD peptide. Once the bioreactor reached the desired region, GOx promptly consumed the intratumoral glucose and oxygen to starve cancer cells for robust starvation therapy. More importantly, the aggravated acidic microenvironment at the tumor region was found to induce the decomposition of the MOF structure, thus triggering the release of DOX for reinforced chemotherapy. This bioreactor would further prompt the development of synergistic patterns toward cancer treatment in a spatiotemporally controlled manner.

Glycosylation of PAMAM dendrimers significantly improves tumor macrophage targeting and specificity in glioblastoma

Glioblastoma is among the most aggressive forms of cancers, with a median survival of just 15-20 months for patients despite maximum clinical intervention. The majority of conventional anti-cancer therapies fail due to associated off-site toxicities which can be addressed by developing target-specific drug delivery systems. Advances in nanotechnology have provided targeted systems to overcome drug delivery barriers associated with brain and other types of cancers. Dendrimers have emerged as promising vehicles for targeted drug and gene delivery. Dendrimer-mediated targeting strategies can be further enhanced through the addition of targeting ligands to enable receptor-specific interactions. Here, we explore the sugar moieties as ligands conjugated to hydroxyl-terminated polyamidoamine dendrimers to leverage altered metabolism in cancer and immune targeting. Using a highly facile click chemistry approach, we modified the surface of dendrimers with glucose, mannose, or galactose moieties in a well-defined manner, to target upregulated sugar transporters in the context of glioblastoma. We show that glucose modification significantly enhanced targeting of tumor-associated macrophages (TAMs) and microglia by increasing brain penetration and cellular internalization, while galactose modification shifts targeting away from TAMs towards galectins on glioblastoma tumor cells. Mannose modification did not alter TAMs and microglia targeting of these dendrimers, but did alter their kinetics of accumulation within the GBM tumor. The whole body biodistribution was largely similar between the systems. These results demonstrate that dendrimers are versatile delivery vehicles that can be modified to tailor their targeting for the treatment of glioblastoma and other cancers.

Precision strategies for cancer treatment by modifying the tumor-related bacteria

Research on the roles of the bacteria in tumor development and progression is a rapidly emerging field. Increasing evidence links bacteria with the modification of the tumor immune microenvironment, which greatly influences the antitumor response. In view of the individual immune effects of various bacteria in various tumors, developing personalized bacteria-modulating therapy may be a key to successful antitumor treatment. This review emphasizes the critical role of the bacteria in immune regulation, including both the tumor bacteria and gut bacteria. Aiming at tumor-related bacteria, we focus on various precise modulation strategies and discuss their impact and potential for tumor suppression. Finally, engineered bacteria with tumor-targeting ability could achieve precise delivery of various payloads into tumors, acting as a precision tool. Therefore, a precise tumor-related bacteria therapy may be a promising approach to suppress the development of tumors, as well as an adjuvant therapy to improve the antitumor efficacy of other approaches. KEY POINTS: • The mini-review updates the knowledge on complex effect of bacteria in TME. • Insight into the interaction and adjustment of bacteria in gut for TME. • Prospects and limitations of bacteria-related personalized therapy in the clinical anticancer therapy.

Glycyrrhetinic Acid and TAT Peptide Modified Dual-functional Liposomes for Treatment of Hepatocellular Cancer

BACKGROUND

Surgery remains the front-line therapeutic strategy to treat early hepatocellular carcinoma (HCC). However, the 5-year recurrence rates of HCC patients are high. 10- Hydroxycamptothecin (10-HCPT) is a known anti-HCC agent but its poor solubility and bioavailability have limited its clinical use.

OBJECTIVE

In this study, we developed a novel nanoliposome encapsulated 10-hydroxycamptothecin modified with glycyrrhetinic acid (GA) and TAT peptide (GA/TAT-HCPT-LP) for the treatment of HCC. Dual modified GA and TAT can enhance tumor targeting and tumor penetration.

METHODS

The GA/TAT-HCPT-LP NPs were synthesized using the thin-film dispersion method. GA/TAT-HCPT-LP were characterized for particle size, zeta potential and morphology. Drug release from the GA/TAT-HCPT-LP liposomes was measured by dialysis. Cell-uptake was assessed by microscopy and flow cytometry. Cell proliferation, migration and apoptosis were measured to evaluate in vitro antitumor activity of GA/TAT-HCPT-LP via CCK-8 assays, Transwell assays, and flow cytometry, respectively. The in vivo distribution of GA/TAT-HCPT-LP was evaluated in HCC animal models. Tumor- bearing mouse models were used to assess the in vivo therapeutic efficacy of GA/TAT-HCPT-LP.

RESULTS

The mean particle size and mean zeta potential of GA/TAT-HCPT-LP were 135.55 ± 2.76 nm and -4.57 ± 0.23 mV, respectively. Transmission electron micrographs (TEM) showed that the GA/TAT-HCPT-LP had a near spherical shape and a double-membrane structure. GA/TAT-HCPT-LP led to slow and continuous drug release, and could bind to HepG2 cells more readily than other groups. Compared to control groups, treatment with GA/TAT-HCPT-LP had a significantly large effect on inhibiting cell proliferation, tumor cell migration and cell apoptosis. In vivo assays showed that GA/TATHCPT- LP selectively accumulated in tumor tissue with obvious antitumor efficacy.

CONCLUSION

In conclusion, the synthesized GA/TAT-HCPT-LP could effectively target tumor cells and enhance cell penetration, highlighting its potential for hepatocellular cancer therapy.

Expression and purification of a recombinant ELRL-MAP30 with dual-targeting anti-tumor bioactivity

MAP30 (Momordica antiviral protein 30kD) is a single-chain Ⅰ-type ribosome inactivating protein with a variety of biological activities, including anti-tumor ability. It was reported that MAP30 would serve as a novel and relatively safe agent for prophylaxis and treatment of liver cancer. To determine whether adding two tumor targeting peptides could improve the antitumor activities of MAP30, we genetically modified MAP30 with an RGD motif and a EGFRi motif, which is a ligand with high affinity for αvβ3 integrins and with high affinity for EGFR. The recombinant protein ELRL-MAP30 (rELRL-MAP30) containing a GST-tag was expressed in E. coli. The rELRL-MAP30 was highly expressed in the soluble fraction after induction with 0.15 mM IPTG for 20 h at 16 °C. The purified rELRL-MAP30 appeared as a band on SDS-PAGE. It was identified by western blotting. Cytotoxicity of recombinant protein to HepG2, MDA-MB-231, HUVEC and MCF-7 cells was detected by MTT analysis. Half maximal inhibitory concentration (IC₅₀) values were 54.64 μg/mL, 70.13 μg/mL, 146 μg/mL, 466.4 μg/mL, respectively. Proliferation inhibition assays indicated that rELRL-MAP30 could inhibit the growth of Human liver cancer cell HepG2 effectively. We found that rELRL-MAP30 significantly induced apoptosis in liver cancer cells, as evidenced by nuclear staining of DAPI. In addition, rELRL-MAP30 induced apoptosis in human liver cancer HepG2 cells by up-regulation of Bax as well as down-regulation of Bcl-2. Migration of cell line were markedly inhibited by rELRL-MAP30 in a dose-dependent manner compared to the recombinant MAP30 (rMAP30). In summary, the fusion protein displaying extremely potent cytotoxicity might be highly effective for tumor therapy.

Synthetic infrared nano-photosensitizers with hierarchical zoom-in target-delivery functionalities for precision photodynamic therapy

Surgical assailment at the vulnerable subcellular organelles (e.g. mitochondria) by photodynamic therapy (PDT) is perceived as the most devastating approach to eradicate the tumors. Herein, we programmed a novel near-infrared (NIR) PDT construct illustrating appreciable hierarchical zoom-in targeting scenario, namely, primary cell-level targeting to carcinoma post systemic dosage and subcellular level targeting to mitochondria. Pertaining to tumor-targeting function, charge reversal chemistry selectively responsive to acidic tumoral microenvironments (pH 6.8) was implemented as the external corona of PDT constructs. This charge transformative exterior entitled minimal biointerfacial reactions in systemic retention but intimate affinities to cytomembranes selectively in tumoral microenvironments, thereby resulting in preferential uptake by tumors. Furthermore, the proposed PDT constructs were equipped with mitochondria targeting triphenylphosphonium (TPP) motif, which appeared to propel intriguing 88% colocalization with mitochondria. Therefore, overwhelming cytotoxic potencies were accomplished by our carefully engineered photodynamic constructs. Another noteworthy is the photodynamic constructs characterized to be excited at tissue-penetrating NIR (980 nm) based on energy transfer between their internal components of anti-Stoke upconversion nanoparticles (UCN, donor) and photodynamic chlorin e6 (Ce6, acceptor). Therefore, practical applications for photodynamic treatment of intractable solid carcinoma were greatly facilitated and complete tumor eradication was achieved by systemic administration of the ultimate multifunctional NIR photodynamic constructs.

Redox-responsive hyaluronic acid-based nanoparticles for targeted photodynamic therapy/chemotherapy against breast cancer

Specific cellular uptake and sufficient drug release in tumor tissues are important for effective cancer therapy. Hyaluronic acid (HA), a skeleton material, could specifically bind to cluster determinant 44 (CD44) receptors highly expressed on the surface of tumor cells to realize active targeting. Cystamine (cys) is sensitive highly reductive environment inside tumor cells and was used as a connecting arm to connect docosahexaenoic acid (DHA) and chlorin e6 (Ce6) to the HA skeleton to obtain redox-sensitive polymer HA-cys-DHA/Ce6 (CHD). Nanoparticles were fabricated and loaded with chemotherapeutic drug docetaxel (DTX) by physical encapsulation. The prepared nanoparticles had significantly increased uptake by MCF-7 cells that overexpressed CD44 receptors, and DTX was effectively released at high reducing condition. Compared with mono-photodynamic therapy (PDT) or mono-chemotherapy, the prepared nanoparticles exhibited superior anti-tumor effect by inhibiting microtubule depolymerization, blocking cell cycle and generating reactive oxygen species (ROS). In vivo anti-tumor experiments proved that DTX/CHD nanoparticles had the best antitumor response versus DTX and CHD nanoparticles under near-infrared (NIR) irradiation. These studies revealed that redox-responsive DTX-loaded CHD nanoparticles held great potential for the treatment of breast cancer.

Advances in receptor modulation strategies for flexible, efficient, and enhanced antitumor efficacy

Tumor-sensitivity, effective transport, and precise delivery to tumor cells of nano drug delivery systems (NDDs) have been great challenges to cancer therapy in recent years. The conventional targeting approach involves actively installing the corresponding ligand on the nanocarriers, which is prone to recognize the antigen blasts overexpressed on the surface of tumor cells. However, there are some probable limitations for the active tumor-targeting systems in vivo as follows: a. the limited ligand amount of modifications; b. possible steric hindrance, which was likely to prevent ligand-receptor interaction during the delivery process. c. the restrained antigen saturation highly expressed on the cell membrane, will definitely decrease the specificity and often lead to "off-target" effects of NDDs; and d. water insolubility of nanocarriers due to excess of ligands modification. Obviously, any regulation of receptors on surface of tumor cells exerted an important influence on the delivery of targeting systems. Herein, receptor upregulation was mostly desired for enhancing targeted therapy from the cellular level. This technique with the amplification of receptors has the potential to enhance tumor sensitivity towards corresponding ligand-modified nanoparticles, and thereby increasing the effective therapeutic concentration as well as improving the efficacy of chemotherapy. The enhancement of positively expressed receptors on tumor cells and receptor-dependent therapeutic agents or NDDs with an assembled "self-promoting" effect contributes to increasing cell sensitivity to NPs, and will provide a basic platform for clinical therapeutic practice. In this review, we highlight the significance of modulating various receptors on different types of cancer cells for drug delivery and therapeutic benefits.

Systemic delivery of CRISPR/Cas9 to hepatic tumors for cancer treatment using altered tropism of lentiviral vector

Therapeutic application of CRISPR/Cas9 nucleases remains a challenge due to the lack of efficient in vivo delivery carriers. Here, we examine the ability of lentiviral vectors pseudotyped with hepatitis C virus (HCV)/E1E2 envelope glycoproteins to systemically deliver CRISPR/Cas9 to hepatic tumors in vivo. We demonstrated that systemic administration of E1E2-pseudotyped lentiviral vectors can selectively deliver Cas9 and sgRNA specific for kinesin spindle protein (KSP) to Huh7 tumors in the orthotopic Huh7 mice due to the specific interactions between E1E2 and their cellular receptors. This specific delivery leads to effective KSP gene disruption, potently inhibiting tumor growth. Furthermore, we demonstrated that E1E2-pseudotyping is more suitable for systemic delivery of CRISPR/Cas9 in cancer therapy than vesicular stomatitis virus-pseudotyping, the most widely used pseudotyping, because of stability in human serum, little transduction to DCs, low innate immune response, and cell-specific targeting ability. This study suggests that E1E2-pseudotyped lentivirus carrying CRISPR/Cas9 can substantially benefit the treatment of Huh7 tumors.

Lactobionic acid-modified thymine-chitosan nanoparticles as potential carriers for methotrexate delivery

In order to achieve efficient delivery of methotrexate (MTX), thymine-chitosan nanoparticles (Thy-Cs NPs) were prepared, and further decorated with lactobionic acid (LA) to obtain tumor-targeting nanoparticles (LA-Thy-Cs NPs). These nanoparticles possessed a regular spherical structure with the average size about 190-250 nm and narrow size distribution, which were kinetically stable in the physiological environment. Due to electrostatic interactions and multiple hydrogen-bonding interactions between MTX and carriers, MTX was loaded into Thy-Cs NPs with high drug loading content (~20%). MTX release from Thy-Cs NPs was significantly accelerated in the mildly acidic environment due to the destruction of two types of non-covalent interactions. In vitro cell experiments demonstrated that LA-Thy-Cs NPs could be efficiently internalized into hepatoma carcinoma cells, leading to higher cytotoxicity. Moreover, MTX-loaded LA-Thy-Cs NPs performed an enhanced growth inhibition in three-dimensional multicellular tumor spheroids. Thus, the LA decorated thymine-chitosan nanocarriers can be a promising candidate for efficient delivery of MTX.

A phthalocyanine-based self-assembled nanophotosensitizer for efficient in vivo photodynamic anticancer therapy

To develop highly efficient photosensitizers for photodynamic therapy, herein a zinc(II) phthalocyanine-folate conjugate (PcN-FA) used to construct an activatable nanophotosensitizer (NanoPcN-FA) through a facile self-assembly. The self-assembled nanophotosensitizer (NanoPcN) without folate-modification was used as a negative control. After self-assembly, the photoactivities of NanoPcN-FA was quenched. The in vitro studies showed that NanoPcN-FA could be taken in by folate-receptor (FR)-positive SKOV3 cells and activated in the cells. It also exhibited slightly higher photocytotoxicity against SKOV3 cells than NanoPcN. Moreover, the competitive assay confirmed that the cellular uptake of NanoPcN-FA was through a FR-mediated process. Finally, the in vivo results indicated that NanoPcN-FA could target tumor tissue of S180 rat ascitic tumor-bearing mice due to the folic acid (FA) ligand, leading to a highly efficient antitumor photodynamic efficacy with the tumor inhibition rate of 95%.

Chondroitin sulfate-hybridized zein nanoparticles for tumor-targeted delivery of docetaxel

Chondroitin sulfate-hybridized zein nanoparticles (zein/CS NPs) were developed for targeted delivery of docetaxel, which exhibited mean diameters of 157.8 ± 3.6 nm and docetaxel encapsulation efficiency of 64.2 ± 1.9 %. Docetaxel was released from the NPs in a sustained manner (∼72 h), following first-order kinetics. The zein/CS NPs showed improved colloidal stability, maintaining the initial size in serum for 12 h. The pre-treatment of CS reduced the uptake efficiency of the NPs by 23 % in PC-3 cells, suggesting the involvement of CD44-mediated uptake mechanism. The NPs showed 2.79-fold lower IC₅₀ values than free docetaxel. Enhanced tumor accumulation of the NPs was confirmed in PC-3 xenograft mice by near-infrared fluorescence imaging (35.3-fold, versus free Cy5.5). The NPs exhibited improved pharmacokinetic properties (9.5-fold longer terminal half-life, versus free docetaxel) and anti-tumor efficacy comparable to Taxotere with negligible systemic toxicity, suggesting zein/CS NPs could be a promising nanoplatform for targeted cancer therapy.

Mono-dispersed nano-hydroxyapatite based MRI probe with tetrahedral DNA nanostructures modification for in vitro tumor cell imaging

Taking advantage of the superior biocompatibility, good stability in a wide pH and temperature range, as well as its strong affinity with DNA of hydroxyapatite (HAp), tetrahedral DNA nanostructures (TDNs) conjugated with AS1411 aptamer (anti-nucleolin overexpressed on tumor cell membranes) were employed as affinity ligands to construct a novel mono-dispersed HAp based probe with Gd³⁺ doping (Apt-TDNs-GdHAp) for MR imaging. The adsorption of TDNs on the nano-HAp surface facilely accomplished the construction of the Apt-TDNs-GdHAp probes. Meanwhile, the use of hydrophilic TDNs not only favored the phase-transfer from the oil phase to the aqueous phase, but also enhanced the mono-dispersion of this probe due to the well-ordered distribution of TDNs on the surface of nano-HAp. Moreover, Apt-TDNs-GdHAp probe with a better mono-dispersion and crystalinity achieved twice higher longitudinal relaxivity (r₁ value) than that of GdHAp synthesized by microwave-assisted method (Microwave-GdHAp), exhibiting much more excellent T₁-weighted imaging performance. With the introduction of TDNs, the stability and the tumor-targeting accessibility were also greatly improved, showing its great potential for further bio-applications.

Discovery of Cell-Surface Vimentin (CSV) as a Sarcoma Target and Development of CSV-Targeted IL12 Immune Therapy

This chapter discusses a novel target of osteosarcoma (OS), cell-surface vimentin (CSV), and a novel generation of interleukin-12 (IL12), CSV-targeted IL12, for treating OS tumor metastasis. Vimentin is a known intracellular structural protein for mesenchymal cells but is also documented in tumor cells. Our recent study definitively revealed that vimentin can be translocated to the surface of very aggressive tumor cells, such as metastatic cells. This CSV property allows investigators to capture circulating tumor cells (CTCs) across any type of tumor, including OS. CTCs are known as the seeds of metastasis; therefore, targeting these cells using CSV is a logical approach for use in a metastatic OS setting. Interestingly, we found that the peptide VNTANST can bind to CSV when fused to the p40 subunit encoding the DNA of IL12. Systemic delivery of this CSV-targeted IL12 immune therapy inhibited OS metastasis and relapse in a mouse tumor model as detailed in this chapter. This CSV-targeted delivery of IL12 also reduced toxicity of IL12. In summary, this chapter details a novel approach for safe IL12 immune therapy via targeting CSV.

Redox dual-stimuli responsive drug delivery systems for improving tumor-targeting ability and reducing adverse side effects

Cancer is a big challenge that has plagued the human beings for ages and one of the most effective treatments is chemotherapy. However, the low tumor-targeting ability limits the wide clinical application of chemotherapy. The microenvironment plays a critical role in many aspects of tumor genesis. It generates the tumor vasculature and it is highly implicated in the progression to metastasis. To maintain a suitable environment for tumor progression, there are special microenvironment in tumor cell, such as low pH, high level of glutathione (GSH) and reactive oxygen species (ROS), and more special enzymes, which is different to normal cell. Microenvironment-targeted therapy strategy could create new opportunities for therapeutic targeting. Compared to other targeting strategies, microenvironment-targeted therapy strategy will control the drug release into tumor cells more accurately. Redox responsive drug delivery systems (DDSs) are developed based on the high level of GSH in tumor cells. However, there are also GSH in normal cell though its level is lower. In order to control the release of drugs more accurately and reduce side effects, other drug release stimuli have been introduced to redox responsive DDSs. Under the synergistic reaction of two stimuli, redox dual-stimuli responsive DDSs will control the release of drugs more accurately and quickly and even increase the accumulation. This review summarizes strategies of redox dual-stimuli responsive DDSs such as pH, light, enzyme, ROS, and magnetic guide to delivery chemotherapeutic agents more accurately, aiming at providing new ideas for further promoting the drug release, enhancing tumor-targeting and improving anticancer effects. To better illustrate the redox dual-stimuli responsive DDS, preparations of carriers are also briefly described in the review.

A novel bi-modal probe based on BaHoF5 and Cu-doped QDs with enhanced CT contrast efficiency and fluorescent brightness for tumor-targeting imaging

In this work, a novel bi-modal imaging probe with enhanced CT contrast efficiency and FL brightness was constructed, in which the combination of a binary CT contrast agent BaHoF₅ and Cu-doped QDs served as a vehicle; hyaluronic acid (HA) was employed as a tumor-targeting ligand. With its CT contrast efficiency about 2.1- and 3.9-fold higher than PEG-BaHoF₅ and Iohexol, the CT contrast efficiency and the fluorescent brightness of the bi-modal probe were both enhanced. Likewise, its fluorescent brightness is almost 6-fold brighter after Cu-doped QDs loading. The most important contribution of this work lies on the proposed strategy. The inherent contradiction of the imaging sensitivity of CT and FL imaging is well balanced and a great CT/FL bi-modal imaging performance is simultaneously obtained even at low concentration (400 μg/mL) of the probe, which was superior to the previous CT/FL bi-modal probes. Moreover, since BaHoF₅ as a binary CT contrast agent was introduced instead of conventional Au and Bi₂S₃, the CT/FL bi-modal probe would be more suitable for different patients under different operation voltages. In addition, the in vitro tumor cell imaging also demonstrated a good photo-stability, FL brightness, and tumor-targeting capability of the probe, indicating its great potential in practical bi-modal imaging for further tumor diagnosis and therapy. Graphical abstract A novel bi-modal imaging probe with enhanced CT contrast efficiency and FL brightness was fabricated, in which its CT contrast efficiency was about 2.1- and 3.9-fold higher than PEG-BaHoF₅ and Iohexol, respectively, and its fluorescent brightness almost 6-fold brighter after Cu-doped QDs loading.

Amino acid transporters: Emerging roles in drug delivery for tumor-targeting therapy

Amino acid transporters, which play a vital role in transporting amino acids for the biosynthesis of mammalian cells, are highly expressed in types of tumors. Increasing studies have shown the feasibility of amino acid transporters as a component of tumor-targeting therapy. In this review, we focus on tumor-related amino acid transporters and their potential use in tumor-targeting therapy. Firstly, the expression characteristics of amino acid transporters in cancer and their relationship with tumor growth are reviewed. Secondly, the recognition requirements are discussed, focusing on the "acid-base" properties, conformational isomerism and structural analogues. Finally, recent developments in amino acid transporter-targeting drug delivery strategies are highlighted, including prodrugs and nanocarriers, with special attention to the latest findings of molecular mechanisms and targeting efficiency of transporter-mediated endocytosis. We aim to offer related clues that might lead to valuable tumor-targeting strategies by the utilization of amino acid transporters.

GLUT1-mediated effective anti-miRNA21 pompon for cancer therapy

Oncogenic microRNAs are essential components in regulating the gene expression of cancer cells. Especially miR21, which is a major player involved of tumor initiation, progression, invasion and metastasis in several cancers. The delivery of anti-miR21 sequences has significant potential for cancer treatment. Nevertheless, since anti-miR21 sequences are extremely unstable and they need to obtain certain concentration to function, it is intensely difficult to build an effective delivery system for them. The purpose of this work is to construct a self-assembled glutathione (GSH)-responsive system with tumor accumulation capacity for effective anti-miR21 delivery and cancer therapy. A novel drug delivery nanosphere carrying millions of anti-miR21 sequences was developed through the rolling circle transcription (RCT) method. GSH-responsive cationic polymer polyethyleneimine (pOEI) was synthesized to protect the nanosphere from degradation by Dicer or other RNase in normal cells and optimize the pompon-like nanoparticle to suitable size. Dehydroascorbic acid (DHA), a targeting molecule, which is a substrate of glucose transporter 1 (GLUT 1) and highly expressed on malignant tumor cells, was connected to pOEI through PEG, and then the polymer was used for contracting a RNA nanospheres into nanopompons. The anti-miR21 nanopompons showed its potential for effective cancer therapy.

Gelatin-chlorin e6 conjugate for in vivo photodynamic therapy

BACKGROUND

Improving the water solubility of hydrophobic photosensitizer and increasing its accumulation in tumor tissue are essential for in vivo photodynamic therapy (PDT). Considering commercialization or clinical application in future, it will be promising to achieve these purposes by developing new agents with simple and non-toxic structure.

RESULTS

We conjugated multiple chlorin e6 (Ce6) molecules to gelatin polymer, synthesizing two types of gelatin-Ce6 conjugates with different amounts of Ce6: gelatin-Ce6-2 and gelatin-Ce6-8. The resulting conjugates remained soluble in aqueous solutions for a longer time than hydrophobic Ce6. The conjugates could generate singlet oxygen and kill tumor cells upon laser irradiation. After intravenous injection into SCC-7 tumor-bearing mice, gelatin-Ce6-2 showed prolonged blood circulation and highly increased accumulation in tumor tissue as observed in real-time imaging in vivo. After laser irradiation, gelatin-Ce6-2 suppressed tumor growth completely and enabled improved PDT compared to free Ce6 and gelatin-Ce6-8.

CONCLUSIONS

This work demonstrates that a simple structure based on photosensitizer and gelatin can highly improve water solubility and stability. Superior tumor tissue accumulation and increased therapeutic efficacy of gelatin-Ce6 during in vivo PDT showed its high potential for clinical application.

A polymeric micelle with an endosomal pH-sensitivity for intracellular delivery and enhanced antitumor efficacy of hydroxycamptothecin

Amphiphilic poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) and poly(ethylene glycol)-poly(benzyl-l-aspartate) (PPA) block copolymers were synthesized as pH-responsive and pH-nonresponsive copolymers, respectively. Polymer micelles were fabricated by the film dispersion method, and hydroxycamptothecin (HCPT) was physically encapsulated into the micelles. The average diameter of the HCPT-loaded PIPA micelles (PIPAH micelles) was approximately 230 nm, which was slightly smaller than that of the HCPT-loaded PPA micelles (PPAH micelles, approximately 260 nm). The drug-loading content and encapsulation efficiency of the PIPAH micelles (3.33% and 68.89%, respectively) were slightly higher than those of the PPAH micelles (2.90% and 59.68%, respectively). The PIPAH micelles exhibited better colloid stability, storage stability, and plasma stability than the PPAH micelles. Drug release from the PIPAH micelles with imino groups was pH dependent, and more than 75% or 65% of the loaded HCPT was released within 24 h in weakly acidic media (pH 5.0 or 6.0, respectively). An in vitro cell assay demonstrated that the pH-sensitive micelles exhibited potent suppression of cancer cell proliferation and little cytotoxicity on normal cells. Additionally, these micelles could be efficiently internalized by the tumor cells through macropinocytosis- and caveolin-mediated endocytotic pathways. HCPT-loaded micelles had longer circulation time than the HCPT solution in a pharmacokinetic study. In vivo antitumor experiments indicate that the PIPAH micelles had better antitumor efficacy than the pH-insensitive PPAH micelles and the HCPT solution. Therefore, the pH-responsive PIPAH micelles have great potential for high-efficiency delivery of HCPT. STATEMENT OF SIGNIFICANCE: In this study, a new type of pH-responsive amphiphilic copolymer, poly(ethylene glycol)-imino-poly(benzyl-l-aspartate) (PIPA) block copolymer, was synthesized. This copolymer had then self-assembled to form nanomicelles for tumor intracellular delivery of hydroxycamptothecin (HCPT) for the first time. In in vitro test, the PIPAH micelles exhibited adequate stability and pH-dependent drug release. To one's excitement, the PIPAH micelles exhibited better antitumor efficacy and biosafety than the pH-insensitive micelles (PPAH) and the HCPT solution in in vitro and in vivo antitumor experiments. Therefore, the pH-responsive micelles in this study have significant potential to be used for high-performance delivery of HCPT and potentially for the targeted delivery of other cancer therapeutic agents. The polymer designed in this study can be used as a carrier of poorly soluble drugs or other active ingredients.

Methioninase Cell-Cycle Trap Cancer Chemotherapy

Cancer cells are methionine (MET) dependent compared to normal cells as they have an elevated requirement for MET in order to proliferate. MET restriction selectively traps cancer cells in the S/G₂ phase of the cell cycle. The cell cycle phase can be visualized by color coding with the fluorescence ubiquitination-based cell cycle indicator (FUCCI). Recombinant methioninase (rMETase) is an enzyme that effectively degrades MET. rMETase induces S/G₂-phase blockage of cancer cells which is identified by the cancer cells' green fluorescence with FUCCI imaging. Cancer cells in G₁/G₀ are the majority of the cells in solid tumors and are resistant to the chemotherapy. Treatment of cancer cells with standard chemotherapy drugs only led to the majority of the cancer cell population being arrested in G₀/G₁ phase, identified by the cancer cells' red fluorescence in the FUCCI system. The G₀/G₁-phase cancer cells are chemo-resistant. Tumor targeting Salmonella typhimurium A1-R (S. typhimurium A1-R) was used to decoy quiescent G₀/G₁ stomach cancer cells growing in nude mice to cycle, with subsequent rMETase treatment to selectively trap the decoyed cancer cells in S/G₂ phase, which made them highly sensitive to chemotherapy. Subsequent cisplatinum (CDDP) or paclitaxel (PTX) chemotherapy was then administered to kill the decoyed and trapped cancer cells, which completely prevented or regressed tumor growth. In a subsequent experiment, a patient-derived orthotopic xenograft (PDOX) model of recurrent CDDP-resistant metastatic osteosarcoma was eradicated by the combination of Salmonella typhimurium A1-R decoy, rMETase S/G₂-phase cell cycle trap, and CDDP cell kill. Salmonella typhimurium A1-R and rMETase pre-treatment thereby overcame CDDP resistance. These results demonstrate the effectiveness of the new chemotherapy paradigm of "decoy, trap, and kill" chemotherapy.

Tumor microenvironment-responsive docetaxel-loaded micelle combats metastatic breast cancer

Efficient tumor-targeting drug delivery systems are urgently needed for treating metastatic breast cancer. In this work, a docetaxel (DTX)-loaded micelle (pDM) as the tumor-microenvironment-responsive delivery platform is developed. The micelle is composed of a pH-sensitive amphiphilic copolymer, poly((1,4-butanediol)-diacrylate-β-N,N-diisopropylethylenediamine)-polyethyleneimine (BD-PEI), and a matrix metalloproteinase (MMP)-responsive polymer, poly((1,4-butanediol)-diacrylate-β-N,N-diisopropylethylenediamine)-peptide-polyethylene glycol (PEG) (BD-peptide-PEG). The PEG block of BD-peptide-PEG will be split by MMPs at the tumor microenvironment, which leads to the change of the surface charge and particle size of the micelle to more positive and smaller one. Owing to this transformation and enhanced permeability and retention (EPR) effect, pDM delivers more DTX into tumor tissues and is internalized more efficiently by tumor cells than the non-MMP-sensitive micelles in the 4T1 tumor-bearing mice model. In addition, DTX is released in acidic endo/lysosomes due to the dissociation of the micelle, triggered by the protonation of the hydrophobic block of BD-PEI. As a result, the DTX-loaded micelle inhibits primary tumor growth and pulmonary metastasis effectively. Thus, this pH/MMP-dual-sensitive drug delivery system, which simultaneously attains three keypoints: prolonged circulation time, directional and efficient uptake into tumor cells, and speedy intracellular drug release, is a promising strategy for metastatic breast cancer therapy.

Emerging transporter-targeted nanoparticulate drug delivery systems

Transporter-targeted nanoparticulate drug delivery systems (nano-DDS) have emerged as promising nanoplatforms for efficient drug delivery. Recently, great progress in transporter-targeted strategies has been made, especially with the rapid developments in nanotherapeutics. In this review, we outline the recent advances in transporter-targeted nano-DDS. First, the emerging transporter-targeted nano-DDS developed to facilitate oral drug delivery are reviewed. These include improvements in the oral absorption of protein and peptide drugs, facilitating the intravenous-to-oral switch in cancer chemotherapy. Secondly, the recent advances in transporter-assisted brain-targeting nano-DDS are discussed, focusing on the specific transporter-based targeting strategies. Recent developments in transporter-mediated tumor-targeting drug delivery are also discussed. Finally, the possible transport mechanisms involved in transporter-mediated endocytosis are highlighted, with special attention to the latest findings of the interactions between membrane transporters and nano-DDS.

Integrin αvβ3 receptor targeting PET/MRI dual-modal imaging probe based on the 64Cu labeled manganese ferrite nanoparticles

With the advent of positron emission tomography/magnetic resonance imaging (PET/MRI) scanner, PET/MRI dual-modal imaging will play more and more important role in the diagnosis of cancers and other diseases. Until now, there is no an approved PET/MRI dual-modal imaging probe. The goal of this work is to design and synthesize potential PET/MRI dual-modal imaging probe based on superparamagnetic manganese ferrite nanoparticles. We have developed superparamagnetic nanoparticles that have uniform size with 5 nm and can be further functionalized through surface coating with dopamine and polyethylene glycol derivatives, which provide functional groups for conjugating tumor-targeting biomolecules and bifunctional chelators. The nanoparticles conjugated with integrin α_vβ₃ over-expressed targeting cyclic arginine-glycine-aspartic acid (RGD)-peptide and labeled with positron radionuclide copper-64 were intravenously injected into glioblastoma xenograft nude mice. In vivo MRI and PET imaging of mice implied that the PET/MRI dual-modal imaging probe can precisely locate the tumor site with α_vβ₃ over expression.

Tumor-targeting Salmonella typhimurium A1-R is a highly effective general therapeutic for undifferentiated soft tissue sarcoma patient-derived orthotopic xenograft nude-mouse models

Undifferentiated soft tissue sarcoma (USTS) is a recalcitrant and heterogeneous subgroup of soft tissue sarcoma with high risk of metastasis and recurrence. Due to heterogeneity of USTS, there is no reliably effective first-line therapy. We have generated tumor-targeting Salmonella typhimurium A1-R (S. typhimurium A1-R), which previously showed strong efficacy on single patient-derived orthotopic xenograft (PDOX) models of Ewing's sarcoma and follicular dendritic cell sarcoma. In the present study, tumor resected from 4 patients with a biopsy-proven USTS (2 undifferentiated pleomorphic sarcoma [UPS], 1 undifferentiated sarcoma not otherwise specified [NOS] and 1 undifferentiated spindle cell sarcoma [USS]) were grown orthotopically in the biceps femoris muscle of mice to establish PDOX models. One USS model and one UPS model were doxorubicin (DOX) resistant. One UPS and the NOS model were partially sensitive to DOX. DOX is first-line therapy for these diseases. S. typhimurium A1-R arrested tumor growth all 4 models. In addition to arresting tumor growth in each case, S. typhimurium A1-R was significantly more efficacious than DOX in each case, thereby surpassing first-line therapy. These results suggest that S. typhimurium A1-R can be a general therapeutic for USTS and possibly sarcoma in general.

Multifunctional Liposomes

Liposomes have come a long way since their conception in the 1960s, when they were envisioned primarily for drug delivery. Besides serving the important function of the delivery of a variety of drugs, liposomes offer a platform for the co-delivery of a range of therapeutic and diagnostic agents with different physicochemical properties. They are also amenable to the addition of various targeting moieties such as proteins, sugars, and antibodies for selective targeting at a desired site, including tumors. Currently, the design of stimuli-sensitive liposomes for drug delivery is a lively area of research. Compared to conventional liposomes, stimuli-sensitive nanoplatforms respond to local conditions that are characteristics of the pathological area of interest, allowing the release of active agents at the targeted site. Acidic pH, abnormal levels of enzymes, temperature, altered redox potential, and external magnetic field are examples of internal and external stimuli exploited in the design of stimuli-sensitive liposomes. The penetration of the liposomes into the cells can be enhanced with the help of a variety of cell penetrating peptides, which can be incorporated into the liposomes with the help of various lipid-polymer conjugates. Liposomes are now being employed in diagnostics as well. Imaging of a tumor can be made easier by the inclusion of fluorescent probes. They can also be used for gamma or MR imaging using chelated reporter metals and incorporating them either into the core of the liposome or in the lipid bilayer facing outwards. In this chapter, we discuss methods that are commonly used for the preparation of liposomes with a vast range of functions to meet a variety of needs in diagnostics and drug delivery.

HPMA copolymer conjugate with pirarubicin: In vitro and ex vivo stability and drug release study

We have developed a tumor environment-responsive polymeric anticancer prodrug containing pirarubicin (THP) conjugated to N-(2-hydroxypropyl) methacrylamide copolymer (PHPMA), [P-THP], through a spacer containing pH-sensitive hydrazone bond, that showed remarkable therapeutic effect against various tumor models and in a human pilot study. Toward clinical development, here we report THP release profile from its HPMA copolymer conjugate, the conjugate stability, protein and cell-binding and solubility of P-THP. Size exclusion chromatography of P-THP (molecular weight 38 kDa) showed similar hydrodynamic volume as bovine serum albumin (BSA) in aqueous solution, with no apparent interactions with BSA, nor aggregation by itself. pH-responsive release of free THP was reconfirmed at pHs 6.5 and lower. The drug release was significantly affected by a type of used buffer. Phosphate buffer seems to facilitate faster hydrazone bond cleavage at pH 7.4 whereas higher stability was achieved in L-arginine solution which yielded only little cleavage and THP release, approx. 15% within 2 weeks at the same pH at 25 °C. Furthermore, ex vivo study using sera of different animal species showed very high stability of P-THP. Incubation with blood showed high stability of P-THP during circulation, without binding to blood cells. These findings revealed that L-arginine solution provides appropriate media for formulation of P-THP infusion solution as tumor-targeted polymeric anticancer drug based on EPR effect.

Extracellular matrix remodeling in vivo for enhancing tumor-targeting efficiency of nanoparticle drug carriers using the pulsed high intensity focused ultrasound

Dense and stiff extracellular matrix (ECM) in heterogeneous tumor tissues can inhibit deep penetration of nanoparticle drug carriers and decreases their therapeutic efficacy. Herein, we suggest the ECM remodeling strategy by the pulsed high intensity focused ultrasound (Pulsed-HIFU) technology for enhanced tumor-targeting of nanoparticles. First, we clearly observed that the tumor-targeting efficacy and tissue penetration of intravenously injected Cy5.5-labled glycol chitosan nanoparticles (Cy5.5-CNPs) were greatly inhibited in tumor tissue containing high collagen and hyaluronan contents in ECM-rich A549 tumor-bearing mice, compared to in ECM-less SCC7. When collagenase or hyaluronidase was treated by intra-tumoral injection, the amount of collagen and hyaluronan decreased in ECM-rich A549 tumor tissues and more Cy5.5-CNPs penetrated inside the tumor tissue, confirmed using non-invasive optical imaging. Finally, in order to break down the stiff ECM structure, ECM-rich A549 tumor tissues were treated with the relatively low power of Pulse-HIFU (20W/cm²), wherein acute tissue damage was not observed. As we expected, the A549 tumor tissues showed the remodeling of ECM structure after non-invasive Pulsed-HIFU exposure, which resulted in the increased blood flow, decreased collagen contents, and enhanced penetration of CNP_S. Importantly, the tumor targeting efficiency in Pulsed-HIFU-treated A549 tumor tissues was 2.5 times higher than that of untreated tumor tissues. These overall results demonstrate that ECM remodeling and disruption of collagen structure by Pulse-HIFU is promising strategy to enhance the deep penetration and enhanced tumor targeting of nanoparticles in ECM-rich tumor tissues.

A multi-functional nanoplatform for efficacy tumor theranostic applications

Nanomaterials with multiple functions have become more and more popular in the domain of cancer research. MoS₂ has a great potential in photothermal therapy, X-ray/CT imaging and drug delivery. In this study, a water soluble MoS₂ nanosystem (MoS₂-PEG) was synthesized and explored in drug delivery, photothermal therapy (PTT) and X-ray imaging. Doxorubicin (DOX) was loaded onto MoS₂-PEG with a high drug loading efficiency (~69%) and obtained a multifunctional drug delivery system (MoS₂-PEG/DOX). As the drug delivery, MoS₂-PEG/DOX could efficiently cross the cell membranes, and escape from the endosome via NIR light irradiation, lead to more apoptosis in MCF-7 cells, and afford higher antitumor efficacy without obvious toxic effects to normal organs owing to its prolonged blood circulation and 11.6-fold higher DTX uptake of tumor than DOX. Besides, MoS₂-PEG/DOX not only served as a drug delivery system, but also as a powerful PTT agent for thermal ablation of tumor and a strong X-ray contrast agent for tumor diagnosis. In the in vitro and in vivo studies, MoS₂-PEG/DOX exhibited excellent tumor-targeting efficacy, outstanding synergistic anti-cancer effect of photothermal and chemotherapy and X-ray imaging property, demonstrating that MoS₂-PEG/DOX had a great potential for simultaneous diagnosis and photothermal-chemotherapy in cancer treatment.

Angiogenic inhibitors delivered by the type III secretion system of tumor-targeting Salmonella typhimurium safely shrink tumors in mice

Despite of a growing number of bacterial species that apparently exhibit intrinsic tumor-targeting properties, no bacterium is able to inhibit tumor growth completely in the immunocompetent hosts, due to its poor dissemination inside the tumors. Oxygen and inflammatory reaction form two barriers and restrain the spread of the bacteria inside the tumors. Here, we engineered a Salmonella typhimurium strain named ST8 which is safe and has limited ability to spread beyond the anaerobic regions of tumors. When injected systemically to tumor-bearing immunocompetent mice, ST8 accumulated in tumors at levels at least 100-fold greater than parental obligate anaerobic strain ST4. ST8/pSEndo harboring therapeutic plasmids encoding Endostatin fused with a secreted protein SopA could target vasculature at the tumor periphery, can stably maintain and safely deliver a therapeutic vector, release angiogenic inhibitors through a type III secretion system (T3SS) to interfere with the pro-angiogenic action of growth factors in tumors. Mice with murine CT26 colon cancer that had been injected with ST8/pSEndo showed efficient tumor suppression by inducing more severe necrosis and inhibiting blooding vessel density within tumors. Our findings provide a therapeutic platform for indirectly acting therapeutic strategies such as anti-angiogenesis and immune therapy.

Dual targeting luminescent gold nanoclusters for tumor imaging and deep tissue therapy

Dual targeting towards both extracellular and intracellular receptors specific to tumor is a significant approach for cancer diagnosis and therapy. In the present study, a novel nano-platform (AuNC-cRGD-Apt) with dual targeting function was initially established by conjugating gold nanocluster (AuNC) with cyclic RGD (cRGD) that is specific to αvβ3integrins over-expressed on the surface of tumor tissues and aptamer AS1411 (Apt) that is of high affinity to nucleolin over-expressed in the cytoplasm and nucleus of tumor cells. Then, AuNC-cRGD-Apt was further functionalized with near infrared (NIR) fluorescence dye (MPA), giving a NIR fluorescent dual-targeting probe AuNC-MPA-cRGD-Apt. AuNC-MPA-cRGD-Apt displays low cytotoxicity and favorable tumor-targeting capability at both in vitro and in vivo level, suggesting its clinical potential for tumor imaging. Additionally, Doxorubicin (DOX), a widely used clinical chemotherapeutic drug that kill cancer cells by intercalating DNA in cellular nucleus, was immobilized onto AuNC-cRGD-Apt forming a pro-drug, AuNC-DOX-cRGD-Apt. The enhanced tumor affinity, deep tumor penetration and improved anti-tumor activity of this pro-drug were demonstrated in different tumor cell lines, tumor spheroid and tumor-bearing mouse models. Results in this study suggest not only the prospect of non-toxic AuNC modified with two targeting ligands for tumor targeted imaging, but also confirm the promising future of dual targeting AuNC as a core for the design of prodrug in the field of cancer therapy.

Salmonella typhimurium A1-R and Cell-Cycle Decoy Therapy of Cancer

Cancer cells in G0/G1 are resistant to cytotoxic chemotherapy agents which kill only cycling cancer cells. Salmonella typhimurium A1-R (S. typhimurium A1-R) decoyed cancer cells in monolayer culture and in tumor spheres to cycle from G0/G1 to S/G2/M, as demonstrated by fluorescence ubiquitination-based cell cycle indicator (FUCCI) imaging. S. typhimurium A1-R targeted FUCCI-expressing subcutaneous tumors, and tumors growing on the liver, growing in nude mice and also decoyed quiescent cancer cells, which were the majority of the cells in the tumors, to cycle from G0/G1 to S/G2/M. The S. typhimurium A1-R-decoyed cancer cells became sensitive to cytotoxic agents.

Isolation and Analysis of Suppressor Mutations in Tumor-Targeted msbB Salmonella

Tumor-targeted Salmonella offers a promising approach to the delivery of therapeutics for the treatment of cancer. The Salmonella strains used, however, must be stably attenuated in order to provide sufficient safety for administration. Approaches to the generation of attenuated Salmonella strains have included deletion of the msbB gene that is responsible for addition of the terminal myristol group to lipid A. In the absence of myristoylation, lipid A is no longer capable of inducing septic shock, resulting in a significant enhancement in safety. However, msbB Salmonella strains also exhibit an unusual set of additional physiological characteristics, including sensitivities to NaCl, EGTA, deoxycholate, polymyxin, and CO2. Suppressor mutations that compensate for these sensitivities include somA, Suwwan, pmrA (C), and zwf. We describe here methods for isolation of strains with compensatory mutations that suppress these types of sensitivities and techniques for determining their underlying genetic changes and analysis of their effects in murine tumor models.

Future of Bacterial Therapy of Cancer

Bacterial therapy of cancer has a centuries-long history and was first-line therapy at the hospital in New York City that would become Memorial Sloan-Kettering Cancer Center, under Dr. William B. Coley. However, after Coley's death in 1936, bacterial therapy of cancer ceased in the clinic until the present century. Clinical trials have been recently carried out for strains of the obligate anaerobe Clostridium novyi with the toxin gene deleted, and on an attenuated strain of Salmonella typhimurium (S. typhimurium), which is a facultative anaerobe that can grow in viable, as well as necrotic, areas of tumors, unlike Clostridium, which can only grow in the hypoxic areas. Our laboratory has developed the novel strain S. typhimurium A1-R that is effective against all tumor types in clinically-relevant mouse models, including patient-derived orthotopic xenograft (PDOX) mouse models. This chapter suggests future clinical applications for S. typhimurium A1-R.

A tumor-specific cleavable nanosystem of PEG-modified C60@Au hybrid aggregates for radio frequency-controlled release, hyperthermia, photodynamic therapy and X-ray imaging

Taking advantages of fullerene (C60) and gold nanoparticles (AuNPs) for potentials in photodynamic therapy (PDT), drug delivery and radio frequency thermal therapy (RTT), a C60@Au hybrid nanocomposite was synthesized by chemical deposition of Au nanoparticles onto C60, and functionalized by PEG5000 via a pH cleavable hydrazone bond, making C60@Au-PEG keep the PEG on the surface of drug delivery system during circulation but dissociate PEG from the system after accumulation in tumor tissue, then doxorubicin (DOX) was loaded onto C60@Au-PEG with a very high drug loading efficiency. The release profiles of DOX from C60@Au-PEG/DOX showed strong dependences on radio frequency (RF). For the drug delivery, C60@Au-PEG/DOX afforded much higher antitumor efficacy owing to 8.6-fold higher DOX uptake of tumor than DOX. Besides, in this work, C60@Au-PEG/DOX not only served as a powerful RTT agent for RF-thermal ablation of tumor and a strong photosensitizer (PS) for PDT, but also as an X-ray contrast agent for tumor diagnosis. In the in vitro and in vivo studies, C60@Au-PEG/DOX showed excellent chemo-RF thermal-photodynamic therapeutic efficacy, RF-controlled drug releasing function, tumor targeting property, tumoral acid PEG dissociating character and X-ray imaging ability, demonstrating that there is a great potential of C60@Au-PEG/DOX for simultaneous diagnosis and therapy in cancer treatment.

STATEMENT OF SIGNIFICANCE

A significant challenge in cancer therapy is to maximize the therapeutic efficacy and minimize the side effects. In the past decade, a lot of nanoparticles have been used as the carriers for efficient drug delivery. However, the design of drug delivery system (DDS) with stimuli-responsive controlled-release property, simultaneous diagnosis and therapy functions is still a challenge. Herein, we developed a new drug delivery system (C60@Au-PEG/DOX), and explored its applications in tumor therapy. The in vitro and in vivo results showed C60@Au-PEG/DOX could significantly improve the therapeutic efficacy and reduce the systemic toxicity through X-ray imaging guided locatable DOX release, photodynamic and photothermal therapies. These results are of interest as they demonstrate a multi-functional DDS for tumor theranostic applications.