Tetrameric far-red fluorescent protein as a scaffold to assemble an octavalent peptide nanoprobe for enhanced tumor targeting and intracellular uptake in vivo

Effective treatment of metastatic sentinel lymph nodes by dual-targeting melittin nanoparticles

Sentinel lymph node (SLN) metastasis is an important promoter of distant metastasis in breast cancer. Therefore, the timely diagnosis and precise treatment are crucial for patient staging and prognosis. However, the simultaneous diagnosis of metastasis and the implementation of imaging-guided SLN therapy is challenging. Here, we report a melittin-loaded and hyaluronic acid (HA)-conjugated high-density lipoprotein (HDL) mimic phospholipid scaffold nanoparticle (MLT-HA-HPPS), which dually-target to both breast cancer and its SLN and efficiently inhibit SLN metastasis in the LN metastasis model. The melittin peptide was successfully loaded onto HA-HPPS via electrostatic interactions, and MLT-HA-HPPS possesses effective cytotoxicity for breast cancer 4T1 cells. Moreover, the effective delivery of MLT-HA-HPPS from the primary tumor into SLN is monitored by NIR fluorescence imaging, which greatly benefits the prognosis and treatment of metastatic SLNs. After paracancerous administration, MLT-HA-HPPS can efficiently inhibit primary tumor growth with an inhibition rate of 81.3% and 76.5% relative to the PBS-treated control group and HA-HPPS group, respectively. More importantly, MLT-HA-HPPS can effectively inhibit the growth of the metastatic SLNs with an approximately 78.0%, 79.1%, and 64.2% decrease in SLNs weight than those in PBS, HA-HPPS, and melittin-treated mice, respectively. Taken together, the MLT-HA-HPPS may provide an encouraging theranostic of SLN drug delivery strategy to inhibit primary tumor progression and prevent SLN metastasis of breast cancer.

Precision Killing of M2 Macrophages with Phage-Displayed Peptide-Photosensitizer Conjugates

Among the immunosuppressive cells recruited to the tumor microenvironment, macrophages are particularly abundant and involved in angiogenesis, metastasis, and resistance to current cancer therapies. A strategy that simultaneously targets tumor cells and macrophages, particularly pro-tumoral M2 macrophages, would have significant clinical impact for various types of solid malignancies. By the use of phage display technology, we have recently developed a synthetic peptide, named NW, which binds to M1 and M2 macrophages with high affinity. Additional affinity selection on M2 macrophages identified only dominant peptides whose binding motifs are similar to that of the NW peptide. To reduce the frequency of selecting such dominating peptides, the peptide library was affinity selected on M2 macrophages blocked with NW peptide. This approach resulted in the selection of peptides that bind to M2, but not M1 macrophages. To explore the therapeutic potential of the selected peptides, the M13 phage-displayed peptides were conjugated to the photosensitizer IR700, which has been used for cancer photoimmunotherapy. The phage displaying a dominant peptide (SPILWLNAPPWA) killed both M1 and M2 macrophages, while those displaying the M2-specific peptides killed M2 macrophages only upon near-infrared light exposure. A significant fraction of the M2 macrophages were also killed with the untargeted M13 phage-IR700 conjugates. Hence, M2 macrophages can also be selectively targeted by the wild type M13 phage, which displayed a significant tropism to these cells. The benefits of this photoimmunotherapy include an automatic self-targeting ability of the wild type M13 phage, and the option of genetic manipulation of the phage genome to include tumor targeting peptides, allowing the killing of both M2 macrophages and cancer cells.

Mesoporous silica nanoparticle-encapsulated Bifidobacterium attenuates brain Aβ burden and improves olfactory dysfunction of APP/PS1 mice by nasal delivery

BACKGROUND

Dysbiosis or imbalance of gut microbiota in Alzheimer's disease (AD) affects the production of short-chain fatty acids (SCFAs), whereas exogenous SCFAs supplementation exacerbates brain Aβ burden in APP/PS1 mice. Bifidobacterium is the main producer of SCFAs in the gut flora, but oral administration of Bifidobacterium is ineffective due to strong acids and bile salts in the gastrointestinal tract. Therefore, regulating the levels of SCFAs in the gut is of great significance for AD treatment.

METHODS

We investigated the feasibility of intranasal delivery of MSNs-Bifidobacterium (MSNs-Bi) to the gut and their effect on behavior and brain pathology in APP/PS1 mice.

RESULTS

Mesoporous silica nanospheres (MSNs) were efficiently immobilized on the surface of Bifidobacterium. After intranasal administration, fluorescence imaging of MSNs-Bi in the abdominal cavity and gastrointestinal tract revealed that intranasally delivered MSNs-Bi could be transported through the brain to the peripheral intestine. Intranasal administration of MSNs-Bi not only inhibited intestinal inflammation and reduced brain Aβ burden but also improved olfactory sensitivity in APP/PS1 mice.

CONCLUSIONS

These findings suggested that restoring the balance of the gut microbiome contributes to ameliorating cognitive impairment in AD, and that intranasal administration of MSNs-Bi may be an effective therapeutic strategy for the prevention of AD and intestinal disease.

Critical parameters for design and development of multivalent nanoconstructs: recent trends

A century ago, the groundbreaking concept of the magic bullet was given by Paul Ehrlich. Since then, this concept has been extensively explored in various forms to date. The concept of multivalency is among such advancements of the magic bullet concept. Biologically, the concept of multivalency plays a critical role in significantly huge numbers of biochemical interactions. This concept is the sole reason behind the higher affinity of biological molecules like viruses to more selectively target the host cell surface receptors. Multivalent nanoconstructs are a promising approach for drug delivery by the active targeting principle. Designing and developing effective and target-specific multivalent drug delivery nanoconstructs, on the other hand, remain a challenge. The underlying reason for this is a lack of understanding of the crucial interactions between ligands and cell surface receptors, as well as the design of nanoconstructs. This review highlights the need for a better theoretical understanding of the multivalent effect of what happens to the receptor-ligand complex after it has been established. Furthermore, the critical parameters for designing and developing robust multivalent systems have been emphasized. We have also discussed current advances in the design and development of multivalent nanoconstructs for drug delivery. We believe that a thorough knowledge of theoretical concepts and experimental methodologies may transform a brilliant idea into clinical translation.

Metastatic status of sentinel lymph nodes in breast cancer determined with photoacoustic microscopy via dual-targeting nanoparticles

Detection of sentinel lymph nodes (SLNs) is critical to guide the treatment of breast cancer. However, distinguishing metastatic SLNs from normal and inflamed lymph nodes (LNs) during surgical resection remains a challenge. Here, we report a CD44 and scavenger receptor class B1 dual-targeting hyaluronic acid nanoparticle (5K-HA-HPPS) loaded with the near-infra-red fluorescent dye DiR-BOA for SLN imaging in breast cancer. The small sized (~40 nm) self-assembled 5K-HA-HPPSs accumulated rapidly in the SLNs after intradermal injection. Compared with normal popliteal LNs (N-LN), there were ~3.2-fold and ~2.4-fold increases in fluorescence intensity in tumour metastatic SLNs (T-MLN) and inflamed LNs (Inf-LN), respectively, 6 h after nanoparticle inoculation. More importantly, photoacoustic microscopy (PAM) of 5K-HA-HPPS showed a significantly distinct distribution in T-MLN compared with N-LN and Inf-LN. Signals were mainly distributed at the centre of T-MLN but at the periphery of N-LN and Inf-LN. The ratio of PA intensity (R) at the centre of the LNs compared with that at the periphery was 5.93 ± 0.75 for T-MLNs of the 5K-HA-HPPS group, which was much higher than that for the Inf-LNs (R = 0.2 ± 0.07) and N-LNs (R = 0.45 ± 0.09). These results suggest that 5K-HA-HPPS injection combined with PAM provides a powerful tool for distinguishing metastatic SLNs from pLNs and inflamed LNs, thus guiding the removal of SLNs during breast cancer surgery.

Fully synthetic macromolecular prodrug chemotherapeutics with EGFR targeting and controlled camptothecin release kinetics

Herein, we developed a fully polymerizable, peptide-targeted, camptothecin polymeric prodrug system. Two prodrug monomers were synthesized via esterification of campothecin (20Cam) and 10-hydroxycamptothecin (10Cam) with mono-2-(methacryloyloxy)ethyl succinate (SMA) resulting in polymerizable forms of the aliphatic ester- and aromatic ester-linked drugs respectively. These monomers were then incorporated into zwitterionic polymers via RAFT copolymerization of the prodrug monomers with a tert-butyl ester protected carboxy betaine monomer. Subsequent deprotection of the tert-butyl residues with TFA yielded carboxy betaine methacrylate (CBM) scaffolds with controlled prodrug incorporation. Reverse phase HPLC was then employed to establish drug release kinetics in human serum at 37 oC for the resultant polymeric prodrugs. Copolymers containing 10Cam residues linked via aromatic esters showed faster hydrolysis rates with 59 % drug released at 7 days, while copolymers with Cam residues linked via aliphatic esters showed only 28 % drug release over the same time period. These differences in drug release kinetics were then shown to correlate with large differences in cytotoxic activity in SKOV3 ovarian cancer cell cultures. At 72 hours, the IC50s of aromatic- and aliphatic- ester linked prodrugs were 56 nM and 4776 nM, respectively. An EGFR-targeting peptide sequence, GE11, was then directly incorporated into the polymeric prodrugs via RAFT copolymerization of the polymeric prodrugs with a peptide macronomer. The GE11-targeted polymeric prodrugs showed enhanced targeting and cytotoxic activity in SKOV3 cell cultures relative to untargeted polymers containing the negative control sequence HW12. Following pulse-chase treatment (15 min, 37 °C), the 72 hour IC50 of GE11 targeted prodrug was determined to be 1597 nM, in contrast to 3399 nM for the non-targeted control.

High-Throughput Approaches to the Development of Molecular Imaging Agents

Molecular imaging allows for the visualization of changes at the cellular level in diseases such as cancer. A successful molecular imaging agent must rely on disease-selective targets and ligands that specifically interact with those targets. Unfortunately, the translation of novel target-specific ligands into the clinic has been frustratingly slow with limitations including the complex design and screening approaches for ligand identification, as well as their subsequent optimization into useful imaging agents. This review focuses on combinatorial library approaches towards addressing these two challenges, with particular focus on phage display and one-bead one-compound (OBOC) libraries. Both of these peptide-based techniques have proven successful in identifying new ligands for cancer-specific targets and some of the success stories will be highlighted. New developments in screening methodology and sequencing technology have pushed the bounds of phage display and OBOC even further, allowing for even faster and more robust discovery of novel ligands. The combination of multiple high-throughput technologies will not only allow for more accurate identification, but also faster affinity maturation, while overall streamlining the process of translating novel ligands into clinical imaging agents.

Tumor-targeting peptides from combinatorial libraries

Cancer is one of the major and leading causes of death worldwide. Two of the greatest challenges in fighting cancer are early detection and effective treatments with no or minimum side effects. Widespread use of targeted therapies and molecular imaging in clinics requires high affinity, tumor-specific agents as effective targeting vehicles to deliver therapeutics and imaging probes to the primary or metastatic tumor sites. Combinatorial libraries such as phage-display and one-bead one-compound (OBOC) peptide libraries are powerful approaches in discovering tumor-targeting peptides. This review gives an overview of different combinatorial library technologies that have been used for the discovery of tumor-targeting peptides. Examples of tumor-targeting peptides identified from each combinatorial library method will be discussed. Published tumor-targeting peptide ligands and their applications will also be summarized by the combinatorial library methods and their corresponding binding receptors.

In Vivo Visualization of Tumor Antigen-containing Microparticles Generated in Fluorescent-protein-elicited Immunity

In vivo optical spatio-temporal imaging of the tumor microenvironment is useful to explain how tumor immunotherapies work. However, the lack of fluorescent antigens with strong immunogenicity makes it difficult to study the dynamics of how tumors are eliminated by any given immune response. Here, we develop an effective fluorescent model antigen based on the tetrameric far-red fluorescent protein KatushkaS158A (tfRFP), which elicits both humoral and cellular immunity. We use this fluorescent antigen to visualize the dynamic behavior of immunocytes as they attack and selectively eliminate tfRFP-expressing tumors in vivo; swarms of immunocytes rush toward tumors with high motility, clusters of immunocytes form quickly, and numerous antigen-antibody complexes in the form of tfRFP(+) microparticles are generated in the tumor areas and ingested by macrophages in the tumor microenvironment. Therefore, tfRFP, as both a model antigen and fluorescent reporter, is a useful tool to visualize specific immune responses in vivo.

Efficient extravasation of tumor-repopulating cells depends on cell deformability

Cancer metastasis is the most deadly stage in cancer progression. Despite significant efforts over the past decades, it remains elusive why only a very small fraction of cancer cells is able to generate micrometastasis and metastatic colonization. Recently we have shown that tumor-repopulating cells (TRCs), a highly tumorigenic subpopulation of mouse melanoma cells, can be selected by being cultured and grown in 3D soft fibrin gels. Here we show that when injected into the yolk of a 2 day-post-fertilization (dpf) embryo of Tg (fli1:EGFP or kdrl:mCherry) zebrafish, TRCs are much more efficient in surviving and growing at various secondary sites to generate micrometastasis and metastatic colonization than control melanoma cells that are grown on rigid plastic. The metastasis of TRCs is dependent on the presence of Sox2, a self-renewal gene, and silencing Sox2 leads to the inhibition of TRC metastasis. High-resolution of 3D confocal images of the TRCs at the secondary sites show that extravasation and formation of micrometastases by TRCs are more efficient than by the control cells. Remarkably, efficient extravasation of TRCs in vivo and transmigration in vitro are determined by TRC deformability, as a result of low Cdc42 and high Sox2. Our findings suggest that tumor cell deformability is a key factor in controlling extravasation dynamics during metastasis.

Generation of new peptide-Fc fusion proteins that mediate antibody-dependent cellular cytotoxicity against different types of cancer cells

Antibody-dependent cellular cytotoxicity (ADCC), a key effector function for the clinical effectiveness of monoclonal antibodies, is triggered by the engagement of the antibody Fc domain with the Fcγ receptors expressed by innate immune cells such as natural killer (NK) cells and macrophages. Here, we fused cancer cell-binding peptides to the Fc domain of human IgG1 to engineer novel peptide-Fc fusion proteins with ADCC activity. The designed fusion proteins were expressed in human embryonic kidney 293T cells, followed by purification and characterization by western blots. One of the engineered variants (WN-Fc), bound with high affinity to a wide range of solid tumor cell lines (e.g., colon, lung, prostate, skin, ovarian, and mammary tumors). Treatment of cancer cells with the engineered peptide-Fc fusions in the presence of effector NK cells potentially enhanced cytotoxicity, degranulation, and interferon-γ production by NK cells when compared to cells treated with the Fc control. The presence of competing peptides inhibited NK cell activation. Furthermore, a bispecific peptide-Fc fusion protein activated NK cells against HER-1- and/or HER-2-expressing cancer cells. Collectively, the engineered peptide-Fc fusions constitute a new promising strategy to recruit and activate NK cells against tumor cells, a primary goal of cancer immunotherapy.

PET of c-Met in Cancer with ⁶⁴Cu-Labeled Hepatocyte Growth Factor

The hepatocyte growth factor (HGF) and its receptor, c-Met, are actively involved in tumor progression and metastasis and are closely associated with a poor prognostic outcome for cancer patients. Thus, the development of PET agents that can assess c-Met expression would be extremely useful for diagnosing cancer and subsequently monitoring response to c-Met-targeted therapies. Here, we report the characterization of recombinant human HGF (rh-HGF) as a PET tracer for detection of c-Met expression in vivo.

METHODS

rh-HGF was expressed in human embryonic kidney 293 cells and purified by nickel-nitrilotriacetic acid affinity chromatography. The concentrated rh-HGF was conjugated to 2-S-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid and labeled with (64)Cu. c-Met binding evaluation by flow cytometry was performed on both U87MG and MDA-MB-231 cell lines, which have a high level and a low level, respectively, of c-Met. PET imaging and biodistribution studies were performed on nude mice bearing U87MG and MDA-MB-231 xenografted tumors.

RESULTS

The rh-HGF expression yield was 150-200 μg of protein per 5 × 10(6) cells after a 48-h transfection, with purity of approximately 85%-90%. Flow cytometry examination confirmed that rh-HGF had a strong and specific capacity to bind to c-Met. After (64)Cu labeling, PET imaging revealed specific and prominent uptake of (64)Cu-NOTA-rh-HGF in c-Met-positive U87MG tumors (percentage injected dose per gram, 6.8 ± 1.8 at 9 h after injection) and significantly lower uptake in c-Met-negative MDA-MB-231 tumors (percentage injected dose per gram, 1.8 ± 0.6 at 9 h after injection). The fact that sonication-denatured rh-HGF had significantly lower uptake in U87MG tumors, along with histology analysis, confirmed the c-Met specificity of (64)Cu-NOTA-rh-HGF.

CONCLUSION

This study provided initial evidence that (64)Cu-NOTA-rh-HGF visualizes c-Met expression in vivo, an application that may prove useful for c-Met-targeted cancer therapy.

Selective DNA delivery to tumor cells using an oligoarginine-LTVSPWY peptide

DNA therapy for cancer requires efficient, selective and safe DNA delivery systems. Compared with other non-viral methods such as lipid or polymer-based DNA delivery vectors, peptide-based DNA delivery systems are biocompatible and biodegradable, which leads to lower immunogenicity and lower toxicity. Moreover, peptide vectors are easier to produce and their compositions easier to control because solid-phase peptide synthesis has been extensively developed. However, peptide-based systems for DNA delivery toward special tumor cells or tissues are still lacking. In this study, we constructed a non-viral 9rR-LTVSPWY peptide-based DNA delivery system and showed that it is able to efficiently and selectively transfect DNA into targeted tumor cells. This work presents a novel strategy for tumor cell-specific DNA delivery and a reference for designing more efficient DNA delivery systems targeted towards various types of cancer.

Multivalent polymers for drug delivery and imaging: the challenges of conjugation

Multivalent polymers offer a powerful opportunity to develop theranostic materials on the size scale of proteins that can provide targeting, imaging, and therapeutic functionality. Achieving this goal requires the presence of multiple targeting molecules, dyes, and/or drugs on the polymer scaffold. This critical review examines the synthetic, analytical, and functional challenges associated with the heterogeneity introduced by conjugation reactions as well as polymer scaffold design. First, approaches to making multivalent polymer conjugations are discussed followed by an analysis of materials that have shown particular promise biologically. Challenges in characterizing the mixed ligand distributions and the impact of these distributions on biological applications are then discussed. Where possible, molecular-level interpretations are provided for the structures that give rise to the functional ligand and molecular weight distributions present in the polymer scaffolds. Lastly, recent strategies employed for overcoming or minimizing the presence of ligand distributions are discussed. This review focuses on multivalent polymer scaffolds where average stoichiometry and/or the distribution of products have been characterized by at least one experimental technique. Key illustrative examples are provided for scaffolds that have been carried forward to in vitro and in vivo testing with significant biological results.

Nasopharyngeal cancer-specific therapy based on fusion peptide-functionalized lipid nanoparticles

Current treatment of advanced-stage nasopharyngeal carcinoma (NPC) is not satisfactory. Targeted therapies offer hope for extending survival. Here, we developed simple, robust, and NPC-specific therapeutic lipid nanoparticles based on a fusion peptide, α-NTP, made up of an amphipathic α-helical peptide (α-peptide) linked to an NPC-specific therapeutic peptide (NTP). We found that α-NTP not only retained the sub-30 nm nanostructure-controlling ability of the α-peptide but also displayed the enhanced NPC-targeting ability of the NTP, in which the α-peptide accelerated the uptake of the NTP by NPC cells, with a 4.8-fold increase. Following uptake, α-NTP-based lipid nanoparticles (α-NTP-LNs) exerted coordinated cytotoxicity by inducing cell death via apoptosis and autophagy. In vivo and ex vivo optical imaging data showed that systemically administered α-NTP-LNs efficiently accumulated in the NPC xenograft tumor and displayed high contrast between tumor and normal tissues, which was further confirmed by flow cytometry that there had been a 13-fold uptake difference between tumor cells and hepatocytes. More importantly, the therapeutic efficacy of α-NTP-LNs was specific to NPC xenograft formed with 5-8F cells but not to fibrosarcoma xenograft formed with HT1080 cells in vivo. The growth of 5-8F tumors was significantly inhibited by α-NTP-LNs, with more than 85% inhibition relative to control groups (e.g., α-NTP and PBS treatment). In a lung metastasis model of NPC, survival was significantly improved by α-NTP-LN treatment. In a word, these excellent properties of α-NTP-LNs worked in sync and synergistically, maximizing the therapeutic efficacy of α-NTP-LNs against NPC and its metastasis.

Detection of cell carcinogenic transformation by a quadruplex DNA binding fluorescent probe

Cancer can be easily treated when found early. A probe capable of detecting cell transformation may increase the success rate of early diagnosis of cancer. In this report we have tested the ability of a fluorescent, quadruplex DNA binding probe, 3,6-bis(1-methyl-4- vinylpyridinium) carbazole diiodide (BMVC), to detect cell transformation in vitro. BMVC was applied to living cells in several different models of cell transformation, and the fluorescence signals of BMVC were measured. The degrees of cell transformation in these models were characterized by alterations in cellular morphological phenotype and subcellular organization. When BMVC probes were applied, the number of BMVC-positive cells increased in accordance with the degree of transformation. BMVC was capable of significantly detecting formation of foci, increased cellular motility, cell proliferation, cell apoptosis, anchorage-independent growth, and increased invasiveness of transformed cells. These results demonstrate the ability of BMVC probes to detect cell transformation and indicate that BMVC is of promise for use as a probe in early cancer detection.

Hybrid melittin cytolytic Peptide-driven ultrasmall lipid nanoparticles block melanoma growth in vivo

The cytolytic peptide melittin is a potential anticancer candidate that may be able to overcome tumor drug resistance due to its lytic properties. However, in vivo applications of melittin are limited due to its main side effect, hemolysis, which is especially pronounced following intravenous administration. Here, we designed a hybrid cytolytic peptide, α-melittin, in which the N-terminus of melittin is linked to the C-terminus of an amphipathic α-helical peptide (α-peptide) via a GSG linker. The strong α-helical configuration allows α-melittin to interact with phospholipids and self-assemble into lipid nanoparticles, with a high efficiency for α-melittin encapsulation (>80%) and a strong ability to control the structure of the nanoparticle (~20 nm). This α-melittin-based lipid nanoparticle (α-melittin-NP) efficiently shields the positive charge of melittin (18.70 ± 0.90 mV) within the phospholipid monolayer, resulting in the generation of a neutral nanoparticle (2.45 ± 0.56 mV) with reduced cytotoxicity and a widened safe dosage range. Confocal imaging data confirmed that α-melittin peptides were efficiently released from the nanoparticles and were cytotoxic to the melanoma cells. Finally, α-melittin-NPs were administered to melanoma-bearing mice via intravenous injection. The growth of the melanoma cells was blocked by the α-melittin-NPs, with an 82.8% inhibition rate relative to the PBS-treated control group. No side effects of treatment were found in this study. Thus, the excellent properties of α-melittin-NP give it potential clinical applications in solid tumor therapeutics through intravenous administration.

Scavenger receptor B1 is a potential biomarker of human nasopharyngeal carcinoma and its growth is inhibited by HDL-mimetic nanoparticles

Nasopharyngeal carcinoma (NPC) is a very regional malignant head and neck cancer that has attracted widespread attention for its unique etiology, epidemiology and therapeutic options. To achieve high cure rates in NPC patients, theranostic approaches are actively being pursued and improved efforts remain desirable in identifying novel biomarkers and establishing effective therapeutic approaches with low long-term toxicities. Here, we discovered that the scavenger receptor class B type I (SR-B1) was overexpressed in all investigated NPC cell lines and 75% of NPC biopsies, demonstrating that SR-B1 is a potential biomarker of NPC. Additional functional analysis showed that SR-B1 has great effect on cell motility while showing no significant impact on cell proliferation. As high-density lipoproteins (HDL) exhibit strong binding affinities to SR-B1 and HDL mimetic peptides are reportedly capable of inhibiting tumor growth, we further examined the SR-B1 targeting ability of a highly biocompatible HDL-mimicking peptide-phospholipid scaffold (HPPS) nanocarrier and investigated its therapeutic effect on NPC. Results show that NPC cells with higher SR-B1 expression have superior ability in taking up the core constituents of HPPS. Moreover, HPPS inhibited the motility and colony formation of 5-8F cells, and significantly suppressed the NPC cell growth in nude mice without inducing tumor cell necrosis or apoptosis. These results indicate that HPPS is not only a NPC-targeting nanocarrier but also an effective anti-NPC drug. Together, the identification of SR-B1 as a potential biomarker and the use of HPPS as an effective anti-NPC agent may shed new light on the diagnosis and therapeutics of NPC.

Selective killing of cancer cells by peptide-targeted delivery of an anti-microbial peptide

Antimicrobial peptides selectively kill bacteria while maintaining low mammalian cell cytotoxicity. However, they become cytotoxic subsequent to internalization. Here we have conjugated the lytic peptide (KLAKLAK)(2) to either a cancer-cell binding peptide (LTVSPWY) selected from peptide libraries or to a gastrin-releasing peptide (GNHWAVGHLM) in order to direct the lytic peptide to cancer cells. Peptide cytotoxicity was tested in breast MCF-7 and MDA-MB-231 cancer cells. The fusion peptides were internalized by cancer cells, disintegrated the cell membrane and induced rapid killing of the cells with IC50 values as low as 4-7 μM. Peptide cytotoxicity was dependent on the targeting receptor. Indeed, addition of free targeting peptide reduced cell killing. Blood lymphocytes and normal human mammary epithelial cells were less sensitive to the fusion peptides. Although most of the cells were killed by necrosis, fusion peptides branched with DNA oligonucleotides induced apoptosis as assayed by annexin V staining and activation of caspase 3. Therefore, the new designed drug peptides might provide a potent and selective anticancer therapy.

An (125)I-labeled octavalent peptide fluorescent nanoprobe for tumor-homing imaging in vivo

Targeting radiopeptides are promising agents for radio-theranostics. However, in vivo evaluation of their targeting specificity is often obscured by their short biologic half-lives and low binding affinities. Here, we report an approach to efficiently examine targeting radiopeptides with a new class of octavalent peptide fluorescent nanoprobe (Octa-FNP) platform, which is composed of candidate targeting peptides and a tetrameric far-red fluorescent protein (tfRFP) scaffold. To shed light on this process, (125)I-Octa-FNP, (125)I-tfRFP and (125)I-peptide were synthesized, and their targeting functionalities were compared. Both fluorescence imaging and radioactive quantification results confirmed that (125)I-Octa-FNP had a significantly higher cellular binding capability than (125)I-tfRFP. In vivo biodistribution studies show that at 6 h post-injection, (125)I-Octa-FNP had 2-fold and 30-fold higher tumor uptake than that of (125)I-tfRFP and (125)I-peptide, respectively. Moreover, γ-imaging at 24 h post-injection revealed a remarkable accumulation of (125)I-Octa-FNP in the tumor while maintaining an extremely low background contrast, which was further confirmed by immunofluorescence analysis. These data suggested that, as an engineered and multivalent platform, Octa-FNP could enhance the tumor targeting of a designed peptide and provide excellent contrast radioimaging, making it a valuable tool for the evaluation of the targeting ability of specifically designed radiopeptides for cancer theranostics.

Influence of side chain length on fluorescence intensity of ROMP-based polymeric nanoparticles and their tumor specificity in in-vivo tumor imaging

In this study, amphiphilic brush-like copolymers conjugated with short alkyl or long polymeric chains of various lengths are synthesized using ring-opening metathesis polymerization (ROMP) of substituted norbornadiene monomers followed by chemical transformations. These amphiphilic copolymers form spherical self-assemblies in aqueous media with diameters of 132-244 nm. The low critical aggregation concentration of these assemblies (2.5 × 10(-3) -1.4 × 10(-5) g/L) indicates that they are quite stable in dilute conditions. An appropriate length of polymer side chain that conjugates the polymer backbone with a hydrophobic ICG (indocyanine green) moiety enhanced the fluorescence intensities of these self-assemblies in aqueous solution as well as in tumor-bearing mice. A longer side chain conjugated with tumor targeting agents could significantly affect the tumor specificity of self-assemblies to a greater extent. The self-assemblies bearing hydrophilic tumor targeting agents, such as a glucosamine molecule and a cyclic RGD (arginine-glycine-asparatic acid) peptide, accumulated in tumor tissues with high selectivity, while those having a hydrophobic targeting agent, such as folate moieties, accumulated in tumor sites with low selectivity. The results demonstrated here unambiguously indicate that the fluorescence intensity and tumor specificity of self-assemblies are strongly affected by the length of side chains that conjugate with dyes and targeting agents.