Application of a proapoptotic peptide to intratumorally spreading cancer therapy

Enhancing tumor-specific recognition of programmable synthetic bacterial consortium for precision therapy of colorectal cancer

Probiotics hold promise as a potential therapy for colorectal cancer (CRC), but encounter obstacles related to tumor specificity, drug penetration, and dosage adjustability. In this study, genetic circuits based on the E. coli Nissle 1917 (EcN) chassis were developed to sense indicators of tumor microenvironment and control the expression of therapeutic payloads. Integration of XOR gate amplify gene switch into EcN biosensors resulted in a 1.8-2.3-fold increase in signal output, as confirmed by mathematical model fitting. Co-culturing programmable EcNs with CRC cells demonstrated a significant reduction in cellular viability ranging from 30% to 50%. This approach was further validated in a mouse subcutaneous tumor model, revealing 47%-52% inhibition of tumor growth upon administration of therapeutic strains. Additionally, in a mouse tumorigenesis model induced by AOM and DSS, the use of synthetic bacterial consortium (SynCon) equipped with multiple sensing modules led to approximately 1.2-fold increased colon length and 2.4-fold decreased polyp count. Gut microbiota analysis suggested that SynCon maintained the abundance of butyrate-producing bacteria Lactobacillaceae NK4A136, whereas reducing the level of gut inflammation-related bacteria Bacteroides. Taken together, engineered EcNs confer the advantage of specific recognition of CRC, while SynCon serves to augment the synergistic effect of this approach.

Engineered Polymeric Nanovector for Intracellular Peptide Delivery in Antitumor Therapy

Objective

This study aimed to deliver a polypeptide from the Bax-BH3 domain (BHP) through the synthesis of self-assembled amphiphile nanovectors (NVs) and to assess their potential for cancer therapeutic applications and biological safety in vitro and in vivo. These findings provide valuable options for cancer intervention and a novel approach for the rational design of therapeutics.

Methods

We studied the antitumor activity of BHP by preparing RGDfK-PHPMA-b-Poly (MMA-alt-(Rhob-MA)) (RPPMMRA) and encapsulating it in BHP-NV. We also performed a series of characterizations and property analyses of RPPMMRA, including its size, stability, and drug-carrying capacity. The biocompatibility of RPPMMRA was evaluated in terms of cytotoxicity and hemolytic effects. The pro-apoptotic capacity of BHP was evaluated in vitro using mitochondrial membrane potential, flow cytometry, and apoptosis visualization techniques. The potential therapeutic effects of BHP on tumors were explored using reverse molecular docking. We also investigated the in vivo proapoptotic effect of BHP-NV in a nude mouse tumor model.

Results

NVs were successfully prepared with hydrated particle sizes ranging from 189.6 nm to 256.6 nm, spherical overall, and were able to remain stable in different media for 72 h with drug loading up to 15.2%. The NVs were be successfully internalized within 6 h with good biocompatibility. Neither BHP nor NV showed significant toxicity when administered alone, however, BHP-NV demonstrated significant side effects in vitro and in vivo. The apoptosis rate increased significantly from 14.13% to 66.34%. Experiments in vivo showed that BHP-NV exhibited significant apoptotic and tumor-suppressive effects.

Conclusion

A targeted fluorescent NV with high drug delivery efficiency and sustained release protected the active center of BHP, constituting BHP-NV for targeted delivery. RPPMMRA demonstrated excellent biocompatibility, stability, and drug loading ability, whereas and BHP-NV demonstrated potent antitumor effects in vivo and in vitro.

Recent Studies and Progress in the Intratumoral Administration of Nano-Sized Drug Delivery Systems

Over the last 30 years, diverse types of nano-sized drug delivery systems (nanoDDSs) have been intensively explored for cancer therapy, exploiting their passive tumor targetability with an enhanced permeability and retention effect. However, their systemic administration has aroused some unavoidable complications, including insufficient tumor-targeting efficiency, side effects due to their undesirable biodistribution, and carrier-associated toxicity. In this review, the recent studies and advancements in intratumoral nanoDDS administration are generally summarized. After identifying the factors to be considered to enhance the therapeutic efficacy of intratumoral nanoDDS administration, the experimental results on the application of intratumoral nanoDDS administration to various types of cancer therapies are discussed. Subsequently, the reports on clinical studies of intratumoral nanoDDS administration are addressed in short. Intratumoral nanoDDS administration is proven with its versatility to enhance the tumor-specific accumulation and retention of therapeutic agents for various therapeutic modalities. Specifically, it can improve the efficacy of therapeutic agents with poor bioavailability by increasing their intratumoral concentration, while minimizing the side effect of highly toxic agents by restricting their delivery to normal tissues. Intratumoral administration of nanoDDS is considered to expand its application area due to its potent ability to improve therapeutic effects and relieve the systemic toxicities of nanoDDSs.

PTRH2 Gene Variants: Recent Review of the Phenotypic Features and Their Bioinformatics Analysis

Peptidyl-tRNA hydrolase 2 (PTRH2) is an evolutionarily highly conserved mitochondrial protein. The biallelic mutations in the PTRH2 gene have been suggested to cause a rare autosomal recessive disorder characterized by an infantile-onset multisystem neurologic endocrine and pancreatic disease (IMNEPD). Patients with IMNEPD present varying clinical manifestations, including global developmental delay associated with microcephaly, growth retardation, progressive ataxia, distal muscle weakness with ankle contractures, demyelinating sensorimotor neuropathy, sensorineural hearing loss, and abnormalities of thyroid, pancreas, and liver. In the current study, we conducted an extensive literature review with an emphasis on the variable clinical spectrum and genotypes in patients. Additionally, we reported on a new case with a previously documented mutation. A bioinformatics analysis of the various PTRH2 gene variants was also carried out from a structural perspective. It appears that the most common clinical characteristics among all patients include motor delay (92%), neuropathy (90%), distal weakness (86.4%), intellectual disability (84%), hearing impairment (80%), ataxia (79%), and deformity of head and face (~70%). The less common characteristics include hand deformity (64%), cerebellar atrophy/hypoplasia (47%), and pancreatic abnormality (35%), while the least common appear to be diabetes mellitus (~30%), liver abnormality (~22%), and hypothyroidism (16%). Three missense mutations were revealed in the PTRH2 gene, the most common one being Q85P, which was shared by four different Arab communities and was presented in our new case. Moreover, four different nonsense mutations in the PTRH2 gene were detected. It may be concluded that disease severity depends on the PTRH2 gene variant, as most of the clinical features are manifested by nonsense mutations, while only the common features are presented by missense mutations. A bioinformatics analysis of the various PTRH2 gene variants also suggested the mutations to be deleterious, as they seem to disrupt the structural confirmation of the enzyme, leading to loss of stability and functionality.

Stapling of short cell-penetrating peptides for enhanced tumor cell-and-tissue dual-penetration

Effective delivery of therapeutics to tumors is generally hampered by the limited penetration of biological barriers imposed by the tumor microenvironment. Despite the broad applications of cell-penetrating peptides (CPPs) for intracellular delivery of therapeutics across membrane bilayers, the discovery of novel CPPs with enhanced tumor tissue permeability remains largely unexplored. Herein, we identified two short stapled CPPs with aromatic cross-links that confer superior dual-penetration in tumor cells and tissues over their linear counterparts. This work may benefit the future applications of constrained CPPs as powerful molecular transporters to access deeper tumor tissues.

Internalizing RGD, a great motif for targeted peptide and protein delivery: a review article

Understanding that cancer is one of the most important health problems, especially in advanced societies, is not difficult. The term of targeted cancer therapy has also been well known as an ideal treatment strategy in the recent years. Peptides with ability to specifically recognize the cancer cells with suitable penetration properties have been used as the targeting motif in this regard. In the present review article, we focus on an individual RGD-derived peptide with ability to recognize the integrin receptor on the cancer cell surface like its ancestor with an additional outstanding feature to penetrate to extravascular space of tumor and ability to penetrate to cancer cells unlike the original peptide. This peptide which has been named "internalizing RGD" or "iRGD" has been the focus of researches as a new targeting motif since it was discovered. To date, many types of molecules have been associated with this peptide for their targeted delivery to cancer cells. In this review article, we have discussed a summary of penetration mechanisms of iRGD and all introduced peptides and proteins attached to this attractive cell-penetrating peptide and have expressed the results of the studies.

Tumor Penetrating Peptide-Functionalized Tenascin-C Antibody for Glioblastoma Targeting

BACKGROUND

Conjugation to clinical-grade tumor penetrating iRGD peptide is a widely used strategy to improve tumor homing, extravasation, and penetration of cancer drugs and tumor imaging agents. The C domain of the extracellular matrix molecule Tenascin-C (TNC-C) is upregulated in solid tumors and represents an attractive target for clinical-grade single-chain antibody- based vehicles for tumor delivery drugs and imaging agents.

OBJECTIVE

To study the effect of C-terminal genetic fusion of the iRGD peptide to recombinant anti- TNC-C single-chain antibody clone G11 on systemic tumor homing and extravasation.

METHODS

Enzyme-linked immunosorbent assay was used to study the interaction of parental and iRGD-fused anti-TNC-C single-chain antibodies with C domain of tenascin-C and αVβ3 integrins. For systemic homing studies, fluorescein-labeled ScFV G11-iRGD and ScFV G11 antibodies were administered in U87-MG glioblastoma xenograft mice, and their biodistribution was studied by confocal imaging of tissue sections stained with markers of blood vessels and Tenascin C immunoreactivity.

RESULTS

In a cell-free system, iRGD fusion to ScFV G11 conferred the antibody has a robust ability to bind αVβ3 integrins. The fluorescein labeling of ScFV G11-iRGD did not affect its target binding activity. In U87-MG mice, iRGD fusion to ScFV G11 antibodies improved their homing to tumor blood vessels, extravasation, and penetration of tumor parenchyma.

CONCLUSION

The genetic fusion of iRGD tumor penetrating peptide to non-internalizing affinity targeting ligands may improve their tumor tropism and parenchymal penetration for more efficient delivery of imaging and therapeutic agents into solid tumor lesions.

A Synthetic CPP33-Conjugated HOXA9 Active Domain Peptide Inhibits Invasion Ability of Non-Small Lung Cancer Cells

Homeobox A9 (HOXA9) expression is associated with the aggressive growth of cancer cells and poor prognosis in lung cancer. Previously, we showed that HOXA9 can serve as a potential therapeutic target for the treatment of metastatic non-small cell lung cancer (NSCLC). In the present study, we have carried out additional studies toward the development of a peptide-based therapeutic agent. Vectors expressing partial DNA fragments of HOXA9 were used to identify a unique domain involved in the inhibition of NSCLC cell invasion. Next, we performed in vitro invasion assays and examined the expression of EMT-related genes in transfected NSCLC cells. The C-terminal fragment (HOXA9-C) of HOXA9 inhibited cell invasion and led to upregulation of CDH1 and downregulation of SNAI2 in A549 and NCI-H1299 cells. Reduced SNAI2 expression was consistent with the decreased binding of transcription factor NF-kB to the SNAI2 promoter region in HOXA9-C overexpressing cells. Based on the above results, we synthesized a cell-permeable peptide, CPP33-HADP (HOXA9 active domain peptide), for lung-specific delivery and tested its therapeutic efficiency. CPP33-HADP effectively reduced the invasion ability of NSCLC cells in both in vitro and in vivo mouse models. Our results suggest that CPP33-HADP has significant potential for therapeutic applications in metastatic NSCLC.

PTRH2: an adhesion regulated molecular switch at the nexus of life, death, and differentiation

Peptidyl-tRNA hydrolase 2 (PTRH2; Bit-1; Bit1) is an underappreciated regulator of adhesion signals and Bcl2 expression. Its key roles in muscle differentiation and integrin-mediated signaling are central to the pathology of a recently identified patient syndrome caused by a cluster of Ptrh2 gene mutations. These loss-of-function mutations were identified in patients presenting with severe deleterious phenotypes of the skeletal muscle, endocrine, and nervous systems resulting in a syndrome called Infantile-onset Multisystem Nervous, Endocrine, and Pancreatic Disease (IMNEPD). In contrast, in cancer PTRH2 is a potential oncogene that promotes malignancy and metastasis. PTRH2 modulates PI3K/AKT and ERK signaling in addition to Bcl2 expression and thereby regulates key cellular processes in response to adhesion including cell survival, growth, and differentiation. In this Review, we discuss the state of the science on this important cell survival, anoikis and differentiation regulator, and opportunities for further investigation and translation. We begin with a brief overview of the structure, regulation, and subcellular localization of PTRH2. We discuss the cluster of gene mutations thus far identified which cause developmental delays and multisystem disease. We then discuss the role of PTRH2 and adhesion in breast, lung, and esophageal cancers focusing on signaling pathways involved in cell survival, cell growth, and cell differentiation.

An iRGD peptide fused superantigen mutant induced tumor-targeting and T lymphocyte infiltrating in cancer immunotherapy

Solid tumors are intrinsically resistant to immunotherapy because of the major challenges including the immunosuppression and poor penetration of drugs and lymphocytes into solid tumors due to the complicated tumor microenvironment (TME). Our previous study has created a novel superantigen mutant ST-4 to efficiently active the T lymphocytes and alleviate immune suppression. In the present study, to accumulate ST-4 into the TME, we constructed a recombinant protein, ST-4-iRGD, by fusing ST-4 to a tumor-homing peptide, iRGD. We hypothesized that ST-4-iRGD could internalize into the TME through iRGD-mediated tumor targeting and tumor tissue penetrating to activate the regional immunoreaction. The results of in vitro studies showed that ST-4-iRGD achieved improved tumor targeting and cytotoxicity in mouse B16F10 melanoma cells. The iRGD-mediated tumor tissue penetration was further confirmed by imaging and immunofluorescence studies in vivo, wherein higher distribution of ST-4-iRGD was observed in the mouse 4T1 breast tumor model. Moreover, ST-4-iRGD exhibited enhanced anti-solid tumor characteristics and induced improved lymphocyte infiltration in the B16F10 and 4T1 models. In conclusion, using iRGD to facilitate better dissemination of the therapeutic agent ST-4 throughout a solid tumor mass is feasible, and ST-4-iRGD may be a potential candidate for efficient cancer immunotherapy in the future.

Fluorescent RGD-based pro-apoptotic peptide conjugates as mitochondria-targeting probes for enhanced anticancer activities

We have designed 2-domain anticancer peptides with RGD-based KLAK bi-functional short motifs (linear and cyclic analogues). RGD tripeptide acts as tumor blood vessel 'homing' motif while KLAK tetrapeptide internalized in mitochondria and causes cell apoptosis. All three peptides (RGDKLAK; HM, cyclic-RGDKLAK; HMC-1, and RGD-cyclic-KLAK; HMC-2) were conjugated with fluorescein isothiocyanate isomer-I (5-FITC; F) for in-vivo and in-vitro optical imaging studies. These fluorescent-peptide (FL-peptide) analogues were analyzed to possess α_vβ₃-integrin targeting affinity, high uptake in in-vitro cell binding assays followed by in-vivo tumor xenograft mice studies. Pharmacological profile reveals that F-HMC-1 analogue exhibited selectively and specifically higher affinity for α_vβ₃-integrin than other analogues in U87MG cells in comparison with HeLa cells. The subcutaneous U87MG tumor xenograft mice models clearly visualized the uptake of F-HMC-1 in tumor tissue in contrast with normal tissues with tumor-to-normal tissue ratio (T/NT = 15.9 ± 1.1) at 2 h post-injection. These results suggested that F-HMC-1 peptide has potential diagnostic applications for targeting α_vβ₃-integrin assessed by optical imaging study in U87MG tumor xenograft mice models.

Coadministration of kla peptide with HPRP-A1 to enhance anticancer activity

The apoptosis-inducing peptide kla (KLAKLAK)2 possesses the ability to disrupt mitochondrial membranes and induce cancer cell apoptosis, but this peptide has a poor eukaryotic cell-penetrating potential. Thus, it requires the assistance of other peptides for effective translocation at micromolar concentrations. In this study, breast and lung cancer cells were treated by kla peptide co-administrated with membrane-active anticancer peptide HPRP-A1. HPRP-A1 assisted kla to enter cancer cells and localized on mitochondrial membranes to result in cytochrome C releasing and mitochondrial depolarization which ultimately induced apoptosis.The apoptosis rate was up to 65%and 45% on MCF-7 and A549 cell lines, respectively, induced by HPRP-A1 coadministration with kla group. The breast cancer model was constructed in mice, and the anticancer peptides were injected to observe the changes in cancer volume, andimmunohistochemical analysis was performed on the tissues and organs after the drug was administered. Both the weight and volume of tumor tissue were remarkable lower in HPRP-A1 with kla group compared with thosepeptidealonggroups. The results showed that the combined drug group effectively inhibited the growth of cancer and did not cause toxic damage to normal tissues, as well as exhibited significantly improvement on peptide anticancer activity in vitro and in vivo.

Synergistic effect of the pro-apoptosis peptide kla-TAT and the cationic anticancer peptide HPRP-A1

In this study, a peptide-peptide co-administration therapy between hybrid peptide kla-TAT and cationic anticancer peptide HPRP-A1 was designed to increase the anticancer activity of the combination peptides through synergistic effect. kla is a pro-apoptotic peptide which could induce rapid cancer cell apoptosis by disruption the mitochondrial membrane when internalized the cells. To enhance more kla peptides pass through cell membrane, a double improvement strategy was designed by chemically conjugation with cell penetration peptide TAT as well as co-administration with cationic membrane active peptide HPRP-A1, and the double anticancer mechanism of the kla-TAT peptide and HPRP-A1 including membrane disruption and apoptosis induction was verified through in vitro experiments. The CompuSyn synergism/antagonism analysis showed that kla-TAT acted synergistically with HPRP-A1 against a non-small cell lung cancer (NSCLC) A549 cell line. The anticancer activities of the two peptides were dramatically increased by co-administration, under the mechanism of cell membrane disruption, caspase-dependent apoptosis induction, as well as cyclin-D1 down-regulation based G1 phase arrest. We believe that the synergic therapeutic strategy would be a meaningful method for the anticancer peptides used in cancer treatment.

Cellular internalization of bystander nanomaterial induced by TAT-nanoparticles and regulated by extracellular cysteine

Entry into cells is necessary for many nanomaterial applications, and a common solution is to functionalize nanoparticles (NPs) with cell-penetrating ligands. Despite intensive studies on these functionalized NPs, little is known about their effect on cellular activities to engulf other cargo from the nearby environment. Here, we use NPs functionalized with TAT (transactivator of transcription) peptide (T-NPs) as an example to investigate their impact on cellular uptake of bystander cargo. We find that T-NP internalization enables cellular uptake of bystander NPs, but not common fluid markers, through a receptor-dependent macropinocytosis pathway. Moreover, the activity of this bystander uptake is stimulated by cysteine presence in the surrounding solution. The cargo selectivity and cysteine regulation are further demonstrated ex vivo and in vivo. These findings reveal another mechanism for NP entry into cells and open up an avenue of studying the interplay among endocytosis, amino acids, and nanomaterial delivery.

iRGD: A Promising Peptide for Cancer Imaging and a Potential Therapeutic Agent for Various Cancers

Poor penetration into the tumor parenchyma and the reduced therapeutic efficacy of anticancer drugs and other medications are the major problems in tumor treatment. A new tumor-homing and penetrating peptide, iRGD (CRGDK/RGPD/EC), can be effectively used to combine and deliver imaging agents or anticancer drugs into tumors. The different “vascular zip codes” expressed in different tissues can serve as targets for docking-based (synaptic) delivery of diagnostic and therapeutic molecules. αv-Integrins are abundantly expressed in the tumor vasculature, where they are recognized by peptides containing the RGD integrin recognition motif. The iRGD peptide follows a multistep tumor-targeting process: First, it is proteolytically cleaved to generate the CRGDK fragment by binding to the surface of cells expressing αv integrins (αvβ3 and αvβ5). Then, the fragment binds to neuropilin-1 and penetrates the tumor parenchyma more deeply. Compared with conventional RGD peptides, the affinity of iRGD for αv integrins is in the mid to low nanomolar range, and the CRGDK fragment has a stronger affinity for neuropilin-1 than that for αv integrins because of the C-terminal exposure of a conditional C-end Rule (CendR) motif (R/KXXR/K), whose receptor proved to be neuropilin-1. Consequently, these advantages facilitate the transfer of CRGDK fragments from integrins to neuropilin-1 and consequently deeper penetration into the tumor. Due to its specific binding and strong affinity, the iRGD peptide can deliver imaging agents and anticancer drugs into tumors effectively and deeply, which is useful in detecting the tumor, blocking tumor growth, and inhibiting tumor metastasis. This review aims to focus on the role of iRGD in the imaging and treatment of various cancers.

Modification of IL-24 by tumor penetrating peptide iRGD enhanced its antitumor efficacy against non-small cell lung cancer

Interleukin-24 (IL-24) is known for its tumor suppressive activity and the selective induction of apoptosis of numerous human cancer cells, while demonstrating little harm to normal cells. However, poor tumor penetration remains a key problem for the efficacy of IL-24 as a treatment. The iRGD (CRGDK/RGPDC) is a novel tumor-specific peptide with unique tumor-penetrating and cell-internalizing properties. To enhance the tumor-penetrating effects of IL-24, the iRGD peptide was fused with the C-terminal domain of IL-24 to generate a novel recombinant protein, IL-24-iRGD. The aim of the present study was to investigate the antitumor effects of IL-24-iRGD in non-small cell lung cancer (NSCLC) cells in vitro and in vivo. It was observed that IL-24-iRGD increased the production of IL-6, TNF-α and INF-γ from human peripheral blood monocyte (PBMC), and suppressed cell growth of A549 in vitro. Then A549 cells were subcutaneously injected into nude mice, and these tumor-bearing mice were immunized with IL-24, IL-24-iRGD or PBS via the tail vein. The IL-24 and IL-24-iRGD-treated groups exhibited tumor growth inhibition rates of 26.2% and 59.1%, respectively, when compared with the PBS-treated group. Protein penetration into tumors was analyzed by immunofluorescence, cell apoptosis was examined by TdT-mediated dUTP nick end labeling, and the expression of cleaved caspase-3 was analyzed by immuno-histochemical staining. The results demonstrated that IL-24-iRGD induced apoptosis and inhibited the growth of A549 cells to a significantly greater extent when compared with IL-24 treatment alone. It may provide an improved strategy for antitumor therapy and the clinical treatment of NSCLC.

Antitumor Ability of KT2 Peptide Derived from Leukocyte Peptide of Crocodile Against Human HCT116 Colon Cancer Xenografts

BACKGROUND/AIM

Many antimicrobial peptides have been shown to have anticancer activity against human cancer cell lines. Cationic KT2 peptide, derived from white blood cell extract of Crocodylus siamensis has antibacterial activity and antitumor activity against human cervical cancer cells, but there are no data on the effect of KT2 peptide on tumor growth in vivo. The anticancer activity of KT2 peptide on human colon cancer xenografts was investigated in nude mice.

MATERIALS AND METHODS

Tumors in nude mice (BALB/c -nu/nu mice) were induced by subcutaneous injection with HCT116 cells. Twelve days after cancer cell xenograft, mice were treated by intratumoral injection with phosphate-buffered saline or KT2 peptide (25 and 50 mg/kg) once every 2 days for a total of four times and mice were sacrificed at 2 days after the last treatment.

RESULTS

KT2 peptide treatment did not lead to significant difference in mouse body weight among groups, but reduced both tumor volume and weight of colon cancer xenografts. Moreover, KT2 peptide increased the expression of apoptotic proteins, such as BCL2-associated X (BAX), cleaved caspase-3, and poly (ADP-ribose) polymerase and reduced that of BCL2 apoptosis regulator in xenograft tumors.

CONCLUSION

This finding suggests that KT2 peptide may inhibit tumor growth via apoptosis induction in this mouse model and supports the antitumor ability of KT2 peptide.

Anti-EGFR-iRGD recombinant protein modified biomimetic nanoparticles loaded with gambogic acid to enhance targeting and antitumor ability in colorectal cancer treatment

Background

Red blood cell membrane-coated nanoparticle (RBCm-NP) platform, which consist of natural RBCm and synthetic polymeric core, can extend circulation time in vivo with an improved biocompatibility and stability of this biomimetic nanocarrier. To achieve better bioavailability of antitumor drugs that were loaded in RBCm-NPs, the functionalization of coated RBCm with specific targeting ability is essential. Bispecific recombinant protein anti-EGFR-iRGD, containing both tumor penetrating peptide (internalizing RGD peptide) and EGFR single-domain antibody (sdAb), seems to be an optimal targeting ligand for RBCm-NPs in the treatment of multiple tumors, especially colorectal cancer with high EGFR expression.

Materials and methods

We modified the anti-EGFR-iRGD recombinant protein on the surface of RBCm-NPs by lipid insertion method to construct iE-RBCm-PLGA NPs and confirmed the presentation of active tumor-targeting ability in colorectal cancer models with high EGFR expression when compared with RBCm-PLGA NPs. In addition, potential anti-tumor drug gambogic acid (GA) was loaded into the NPs to endow the antitumor efficiency of iE-RBCm-GA/PLGA NPs. It was simultaneously evaluated whether GA can reach better biocompatibility benefiting from the improved antitumor efficiency of iE-RBCm-GA/PLGA NPs in colorectal cancer models.

Results

We successfully modified anti-EGFR-iRGD proteins on the surface of biomimetic NPs with integrated and stable "shell-core" structure. iE-RBCm-PLGA NPs showed its improved targeting ability in vitro (multicellular spheroids [MCS]) and in vivo (nude mice bearing tumors). Besides, no matter on short-term cell apoptosis at tumor site (terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling [TUNEL]) and long-term tumor inhibition, iE-RBCm-GA/PLGA NPs achieved better antitumor efficacy than free GA in spite of the similar effects of cytotoxicity and apoptosis to GA in vitro.

Conclusion

We expect that the bispecific biomimetic nanocarrier can extend the clinical application of many other potential antitumor drugs similar to GA and become a novel drug carrier in the colorectal cancer treatment.

Immunomodulatory and enhanced antitumor activity of a modified thymosin α1 in melanoma and lung cancer

Tumor-targeted therapy is an attractive strategy for cancer treatment. Peptide hormone thymosin α1 (Tα1) has been used against several diseases, including cancer, but its activity is pleiotropic. Herein, we designed a fusion protein Tα1-iRGD by introducing the tumor homing peptide iRGD to Tα1. Results show that Tα1-iRGD can promote T-cell activation and CD86 expression, thereby exerting better effect and stronger inhibitory against melanoma and lung cancer, respectively, than Tα1 in vivo. These effects are indicated by the reduced densities of tumor vessels and Tα1-iRGD accumulation in tumors. Moreover, compared with Tα1, Tα1-iRGD can attach more B16F10 and H460 cells and exhibits significantly better immunomodulatory activity in immunosuppression models induced by hydrocortisone. Circular dichroism spectroscopy and structural analysis results revealed that Tα1 and Tα1-iRGD both adopted a helical confirmation in the presence of trifluoroethanol, indicating the structural basis of their functions. These findings highlight the vital function of Tα1-iRGD in tumor-targeted therapy and suggest that Tα1-iRGD is a better antitumor drug than Tα1.

Peritoneal Carcinomatosis Targeting with Tumor Homing Peptides

Over recent decades multiple therapeutic approaches have been explored for improved management of peritoneally disseminated malignancies—a grim condition known as peritoneal carcinomatosis (PC). Intraperitoneal (IP) administration can be used to achieve elevated local concentration and extended half-life of the drugs in the peritoneal cavity to improve their anticancer efficacy. However, IP-administered chemotherapeutics have a short residence time in the IP space, and are not tumor selective. An increasing body of work suggests that functionalization of drugs and nanoparticles with targeting peptides increases their peritoneal retention and provides a robust and specific tumor binding and penetration that translates into improved therapeutic response. Here we review the progress in affinity targeting of intraperitoneal anticancer compounds, imaging agents and nanoparticles with tumor-homing peptides. We review classes of tumor-homing peptides relevant for PC targeting, payloads for peptide-guided precision delivery, applications for targeted compounds, and the effects of nanoformulation of drugs and imaging agents on affinity-based tumor delivery.

Co-administration of iRGD with peptide HPRP-A1 to improve anticancer activity and membrane penetrability

To improve the specificity and penetration of anticancer peptides against tumors, in this study, we examined the effects of co-administration of the membrane-active peptide HPRP-A1 and the tumor homing/penetrating peptide iRGD. iRGD peptide is widely recognized as an efficient cell membrane penetration peptide targeting to αvβ3 integrins and neuropilin-1 (NRP-1) receptors, which show high expression in many tumor cells. The anticancer activity, cancer specificity and penetration activity in vitro and in vivo of the co-administered peptides were examined on 2D monolayer cells, 3D multi-cellular spheroids (MCS) and xenograft nude mice. Co-administration of iRGD and HPRP-A1 exhibited stronger anticancer activity and tumor specificity against A549 non-small cell lung cancer cells with NRP-1 receptor overexpression compared with HPRP-A1 alone. A549 cells showed uptake of the peptide combination and destruction of the integrity of the cell membrane, as well as adherence to the mitochondrial net, resulting in induction of apoptosis by a caspase-dependent pathway. The iRGD peptide dramatically increased the penetration depth of HPRP-A1 on A549 MCS and anticancer efficacy in an A549 xenograft mouse model. Our results suggest that the co-administration strategy of anticancer and penetrating peptides could be a potential therapeutic approach for cancer treatment in clinical practice.

Cell Penetrating Peptides as Molecular Carriers for Anti-Cancer Agents

Cell membranes with their selective permeability play important functions in the tight control of molecular exchanges between the cytosol and the extracellular environment as the intracellular membranes do within the internal compartments. For this reason the plasma membranes often represent a challenging obstacle to the intracellular delivery of many anti-cancer molecules. The active transport of drugs through such barrier often requires specific carriers able to cross the lipid bilayer. Cell penetrating peptides (CPPs) are generally 5–30 amino acids long which, for their ability to cross cell membranes, are widely used to deliver proteins, plasmid DNA, RNA, oligonucleotides, liposomes and anti-cancer drugs inside the cells. In this review, we describe the several types of CPPs, the chemical modifications to improve their cellular uptake, the different mechanisms to cross cell membranes and their biological properties upon conjugation with specific molecules. Special emphasis has been given to those with promising application in cancer therapy.

Downregulation of Bit1 expression promotes growth, anoikis resistance, and transformation of immortalized human bronchial epithelial cells via Erk activation-dependent suppression of E-cadherin

The mitochondrial Bit1 protein exerts tumor-suppressive function in NSCLC through induction of anoikis and inhibition of EMT. Having this dual tumor suppressive effect, its downregulation in the established human lung adenocarcinoma A549 cell line resulted in potentiation of tumorigenicity and metastasis in vivo. However, the exact role of Bit1 in regulating malignant growth and transformation of human lung epithelial cells, which are origin of most forms of human lung cancers, has not been examined. To this end, we have downregulated the endogenous Bit1 expression in the immortalized non-tumorigenic human bronchial epithelial BEAS-2B cells. Knockdown of Bit1 enhanced the growth and anoikis insensitivity of BEAS-2B cells. In line with their acquired anoikis resistance, the Bit1 knockdown BEAS-2B cells exhibited enhanced anchorage-independent growth in vitro but failed to form tumors in vivo. The loss of Bit1-induced transformed phenotypes was in part attributable to the repression of E-cadherin expression since forced exogenous E-cadherin expression attenuated the malignant phenotypes of the Bit1 knockdown cells. Importantly, we show that the loss of Bit1 expression in BEAS-2B cells resulted in increased Erk activation, which functions upstream to promote TLE1-mediated transcriptional repression of E-cadherin. These collective findings indicate that loss of Bit1 expression contributes to the acquisition of malignant phenotype of human lung epithelial cells via Erk activation-induced suppression of E-cadherin expression.

Seek & Destroy, use of targeting peptides for cancer detection and drug delivery

Accounting for 16 million new cases and 9 million deaths annually, cancer leaves a great number of patients helpless. It is a complex disease and still a major challenge for the scientific and medical communities. The efficacy of conventional chemotherapies is often poor and patients suffer from off-target effects. Each neoplasm exhibits molecular signatures - sometimes in a patient specific manner - that may completely differ from the organ of origin, may be expressed in markedly higher amounts and/or in different location compared to the normal tissue. Although adding layers of complexity in the understanding of cancer biology, this cancer-specific signature provides an opportunity to develop targeting agents for early detection, diagnosis, and therapeutics. Chimeric antibodies, recombinant proteins or synthetic polypeptides have emerged as excellent candidates for specific homing to peripheral and central nervous system cancers. Specifically, peptide ligands benefit from their small size, easy and affordable production, high specificity, and remarkable flexibility regarding their sequence and conjugation possibilities. Coupled to imaging agents, chemotherapies and/or nanocarriers they have shown to increase the on-site delivery, thus allowing better tumor mass contouring in imaging and increased efficacy of the chemotherapies associated with reduced adverse effects. Therefore, some of the peptides alone or in combination have been tested in clinical trials to treat patients. Peptides have been well-tolerated and shown absence of toxicity. This review aims to offer a view on tumor targeting peptides that are either derived from natural peptide ligands or identified using phage display screening. We also include examples of peptides targeting the high-grade malignant tumors of the central nervous system as an example of the complex therapeutic management due to the tumor's location. Peptide vaccines are outside of the scope of this review.

Specific hepatic stellate cell-penetrating peptide targeted delivery of a KLA peptide reduces collagen accumulation by inducing apoptosis

Liver fibrosis is an aberrant wound-healing process to chronic hepatic inflammation and is characterized by excessive accumulation of extracellular matrix (ECM) that is produced by activated hepatic stellate cells (HSCs). Thus, activated HSCs play a key role in the pathogenesis of liver fibrosis and are a potential target for the treatment of liver fibrosis. Herein, we report that a specific HSC-penetrating peptide reduced collagen accumulation by inducing the apoptosis of HSC-T6 cells. We first screened HSC-specific transduction peptides and identified a novel HSC-targeted cell-penetrating peptide (HTP) that specifically interacted with HSC-T6 cells. A chimeric peptide termed HTPK25 was consequently generated by coupling HTP with the antimicrobial peptide KLA, which is capable of initiating cell apoptosis in mammalian cells. HTPK25 entered cells in a dose-dependent manner, reduced the cell viability and induced apoptosis via the caspase 3 pathway in HSC-T6 cells. Furthermore, HTPK25 inhibited the α-smooth muscle actin and collagen I expression in HSC-T6 cells. Our results demonstrated that the HTP was able to specifically and efficiently deliver the KLA peptide into HSC-T6 cells to induce apoptosis, indicating that HTP-delivered functional agents may present a promising approach for liver fibrosis therapy.

The microbiome in anti-cancer therapy

The commensal microbiome constitutes an important modulator of host physiology and risk of disease, including cancer development and progression. Lately, the microbiome has been suggested to modulate the efficacy of anti-cancer treatment. Examples include chemotherapy and total body irradiation-induced barrier function disruption, leading to microbial efflux that drives activation of anti-tumorigenic T cells; Microbiome-driven release of reactive oxygen species contributing to the efficacy of platinum salts; and microbiome-induced immune priming promoting the anti-tumor effects of alkylating chemotherapy and immune checkpoint inhibitors. Furthermore, selected commensals are able to colonize solid tumors. This 'tumor microbiome' may further impact local tumor responses to treatment and potentially be harnessed for tumor-specific targeting and therapeutic delivery. In this review, we present recent advances in understanding of the intricate role of microbiome in modulating efficacy of a number of anti-cancer treatments, and discuss how anti-cancer treatment approaches utilizing the tumor microbiome may enhance oncological treatment efficacy.

iRGD as a tumor‑penetrating peptide for cancer therapy (Review)

As a tumor-targeting and ‑penetrating peptide, iRGD binds to αv integrins and neuropilin‑1 receptors, which are expressed at high levels on tumor cells and the surfaces of vasculature. Subsequently, iRGD penetrates deep into the tumor parenchyma with antitumor drugs, imaging agents, immune modulators and biological products. These substances are either chemically linked to the peptide or co‑injected with the peptide. The iRGD peptide can be readily synthesized, exhibits significantly improved penetration, compared with traditional peptides, and can effectively inhibit tumor metastasis. Therefore, the peptide is now used widely for the diagnosis and treatment of cancer. However, whether the peptide is able to promote the entry of drugs into non‑targeted cells remains to be fully elucidated. In this review, an overview of iRGD is presented, focusing on its identification, mechanism of action and previous studies on its roles in various types of cancer. Studies in previous years have demonstrated the potential of the iRGD protein for tumors diagnosis and targeted treatment, which warrants further investigation.

Tumor-penetrating peptide fused to a pro-apoptotic peptide facilitates effective gastric cancer therapy

KLA (sequence, KLAKLAKKLAKLAK) is a peptide which leads to programmed cell death by disrupting the mitochondrial membrane. However, low penetration in tumors greatly limits its application and efficacy. To develop a KLA-based cancer therapy, KLA-iRGD, a recombinant protein was constructed. It consists of the KLA peptide and iRGD (CRGDKGPDC), a tumor-homing peptide with high penetration into tumor tissue and cells. The conjugated KLA exhibits pro-apoptotic activity to prevent the growth of a tumor once it is inside the cell. Once KLA-iRGD is internalized in cultured tumor cells, via the activation of the receptor neuropilin-1, it spreads extensively throughout the mass of the tumor. The recombinant KLA-iRGD protein showed antitumor activity in vivo in mice and in vitro in tumor cell lines. Repeated treatment with KLA-iRGD greatly prevented tumor growth, resulting in a considerable reduction in tumor volume. According to our data, KLA-iRGD may serve as a potential anticancer agent with limited systemic toxicity and high selectivity for the treatment of MKN45 gastric cancer, which may lead to the enhancement of new targeted anticancer agents.

Tumor penetrating peptides for improved drug delivery

In vivo screening of phage libraries in tumor-bearing mice has been used to identify peptides that direct phage homing to a tumor. The power of in vivo phage screening is illustrated by the recent discovery of peptides with unique tumor-penetrating properties. These peptides activate an endocytic transport pathway related to but distinct from macropinocytosis. They do so through a complex process that involves binding to a primary, tumor-specific receptor, followed by a proteolytic cleavage, and binding to a second receptor. The second receptor, neuropilin-1 (or neuropilin-2) activates the transport pathway. This trans-tissue pathway, dubbed the C-end Rule (CendR) pathway, mediates the extravasation transport through extravascular tumor tissue of payloads ranging from small molecule drugs to nanoparticles. The CendR technology provides a solution to a major problem in tumor therapy, poor penetration of drugs into tumors. Targeted delivery with tumor-penetrating peptides has been shown to specifically increase the accumulation of drugs, antibodies and nanotherapeutics in experimental tumors in vivo, and in human tumors ex vivo. Remarkably the payload does not have to be coupled to the peptide; the peptide activates a bulk transport system that sweeps along a drug present in the blood. Treatment studies in mice have shown improved anti-tumor efficacy and less damage to normal tissues with drugs ranging from traditional chemotherapeutics to antibodies, and to nanoparticle drugs.

The Anoikis Effector Bit1 Inhibits EMT through Attenuation of TLE1-Mediated Repression of E-Cadherin in Lung Cancer Cells

The mitochondrial Bcl-2 inhibitor of transcription 1 (Bit1) protein is part of an anoikis-regulating pathway that is selectively dependent on integrins. We previously demonstrated that the caspase-independent apoptotic effector Bit1 exerts tumor suppressive function in lung cancer in part by inhibiting anoikis resistance and anchorage-independent growth in vitro and tumorigenicity in vivo. Herein we show a novel function of Bit1 as an inhibitor cell migration and epithelial–mesenchymal transition (EMT) in the human lung adenocarcinoma A549 cell line. Suppression of endogenous Bit1 expression via siRNA and shRNA strategies promoted mesenchymal phenotypes, including enhanced fibroblastoid morphology and cell migratory potential with concomitant downregulation of the epithelial marker E-cadherin expression. Conversely, ectopic Bit1 expression in A549 cells promoted epithelial transition characterized by cuboidal-like epithelial cell phenotype, reduced cell motility, and upregulated E-cadherin expression. Specific downregulation of E-cadherin in Bit1-transfected cells was sufficient to block Bit1-mediated inhibition of cell motility while forced expression of E-cadherin alone attenuated the enhanced migration of Bit1 knockdown cells, indicating that E-cadherin is a downstream target of Bit1 in regulating cell motility. Furthermore, quantitative real-time PCR and reporter analyses revealed that Bit1 upregulates E-cadherin expression at the transcriptional level through the transcriptional regulator Amino-terminal Enhancer of Split (AES) protein. Importantly, the Bit1/AES pathway induction of E-cadherin expression involves inhibition of the TLE1-mediated repression of E-cadherin, by decreasing TLE1 corepressor occupancy at the E-cadherin promoter as revealed by chromatin immunoprecipitation assays. Consistent with its EMT inhibitory function, exogenous Bit1 expression significantly suppressed the formation of lung metastases of A549 cells in an in vivo experimental metastasis model. Taken together, our studies indicate Bit1 is an inhibitor of EMT and metastasis in lung cancer and hence can serve as a molecular target in curbing lung cancer aggressiveness.

Biodistribution and evaluation of 131 I-labeled neuropilin-binding peptide for targeted tumor imaging

Neuropilin-1 (NRP-1) is overexpressed in several kinds of cancer cell and contributes to tumor aggressiveness. Recently, the arginine/lysine-rich peptide with C-terminal motifs (R/K)XX(R/K) indicated promising penetrating and transporting capability into NRP-1 positive cancer cells. In the present study, we describe a ¹³¹ I-labeled C-end rule motif peptide conjugate, Tyr-tLyp-1, for NRP-1 positive tumor targeting and imaging properties. Briefly, a truncated Lyp-1 peptide was designed to expose its C-end motif and conjugated to tyrosine for radiolabeling after structural modification. The peptide indicated specific binding to A549 cancer cells at 2 μM concentration, and its binding was dependent on NRP-1 expression and could be inhibited by other NRP-1-binding peptides. In vivo imaging of ¹³¹ I-labeled Tyr-tLyp-1peptide showed that a subcutaneous A549 xenograft tumor could be visualized using a SPECT/CT scanner. The tumor uptake of ¹³¹ I-Tyr-tLyp-1 was 4.77 times higher than the uptake in muscles by SPECT/CT software quantification at 6 h post injection. Together, this study indicated that truncated Lyp-1 peptide could specifically localize in NRP-1 positive tumors and successfully mediate the ¹³¹ I radionuclide diagnosis, indicating promising targeted imaging capability for NRP-1 positive tumors. Copyright © 2016 John Wiley & Sons, Ltd.

Synchronized cycles of bacterial lysis for in vivo delivery

The pervasive view of bacteria as strictly pathogenic has given way to an appreciation of the widespread prevalence of beneficial microbes within the human body^1–3. Given this milieu, it is perhaps inevitable that some bacteria would evolve to preferentially grow in environments that harbor disease and thus provide a natural platform for the development of engineered therapies^4–6. Such therapies could benefit from bacteria that are programmed to limit bacterial growth while continually producing and releasing cytotoxic agents in situ^7–10. Here, we engineer a clinically relevant bacterium to lyse synchronously at a threshold population density and to release genetically encoded cargo. Following quorum lysis, a small number of surviving bacteria reseed the growing population, thus leading to pulsatile delivery cycles. We use microfluidic devices to characterize the engineered lysis strain and we demonstrate its potential as a drug delivery platform via co-culture with human cancer cells in vitro. As a proof of principle, we track the bacterial population dynamics in ectopic syngeneic colorectal tumors in mice. The lysis strain exhibits pulsatile population dynamics in vivo, with mean bacterial luminescence that remained two orders of magnitude lower than an unmodified strain. Finally, guided by previous findings that certain bacteria can enhance the efficacy of standard therapies¹¹, we orally administer the lysis strain, alone or in combination with a clinical chemotherapeutic, to a syngeneic transplantation model of hepatic colorectal metastases. We find that the combination of both circuit-engineered bacteria and chemotherapy leads to a notable reduction of tumor activity along with a marked survival benefit over either therapy alone. Our approach establishes a methodology for leveraging the tools of synthetic biology to exploit the natural propensity for certain bacteria to colonize disease sites.

Structure-based optimization of GRP78-binding peptides that enhances efficacy in cancer imaging and therapy

It is more challenging to design peptide drugs than small molecules through molecular docking and in silico analysis. Here, we developed a structure-based approach with various computational and analytical techniques to optimize cancer-targeting peptides for molecular imaging and therapy. We first utilized a peptide-binding protein database to identify GRP78, a specific cancer cell-surface marker, as a target protein for the lead, L-peptide. Subsequently, we used homologous modeling and molecular docking to identify a peptide-binding domain within GRP78 and optimized a series of peptides with a new protein-ligand scoring program, HotLig. Binding of these peptides to GRP78 was confirmed using an oriented immobilization technique for the Biacore system. We further examined the ability of the peptides to target cancer cells through in vitro binding studies with cell lines and clinical cancer specimens, and in vivo tumor imaging and targeted chemotherapeutic studies. MicroSPECT/CT imaging revealed significantly greater uptake of (188)Re-liposomes linked to these peptides as compared with non-targeting (188)Re-liposomes. Conjugation with these peptides also significantly increased the therapeutic efficacy of Lipo-Dox. Notably, peptide-conjugated Lipo-Dox significantly reduced stem-cell subpopulation in xenografts of breast cancer. The structure-based optimization strategy for peptides described here may be useful for developing peptide drugs for cancer imaging and therapy.

Strategies for improving the intratumoral distribution of liposomal drugs in cancer therapy

INTRODUCTION

A major limitation of current liposomal cancer therapies is the inability of liposome therapeutics to penetrate throughout the entire tumor mass. This inhomogeneous distribution of liposome therapeutics within the tumor has been linked to treatment failure and drug resistance. Both liposome particle transport properties and tumor microenvironment characteristics contribute to this challenge in cancer therapy. This limitation is relevant to both intravenously and intratumorally administered liposome therapeutics.

AREAS COVERED

Strategies to improve the intratumoral distribution of liposome therapeutics are described. Combination therapies of intravenous liposome therapeutics with pharmacologic agents modulating abnormal tumor vasculature, interstitial fluid pressure, extracellular matrix components, and tumor associated macrophages are discussed. Combination therapies using external stimuli (hyperthermia, radiofrequency ablation, magnetic field, radiation, and ultrasound) with intravenous liposome therapeutics are discussed. Intratumoral convection-enhanced delivery (CED) of liposomal therapeutics is reviewed.

EXPERT OPINION

Optimization of the combination therapies and drug delivery protocols are necessary. Further research should be conducted in appropriate cancer types with consideration of physiochemical features of liposomes and their timing sequence. More investigation of the role of tumor associated macrophages in intratumoral distribution is warranted. Intratumoral infusion of liposomes using CED is a promising approach to improve their distribution within the tumor mass.

Advancement in integrin facilitated drug delivery

The research of integrin-targeted anticancer agents has recorded important advancements in ingenious design of delivery systems, based either on the prodrug approach, or on nanoparticle carriers, but for now, none of these has reached a clinical stage of development. Past work in this area has been extensively reviewed by us and others. Thus, the purpose and scope of the present review is to survey the advancement reported in the last 3years, with focus on innovative delivery systems that appear to afford openings for future developments. These systems exploit the labelling with conventional and novel integrin ligands for targeting the interface of cancer cells and of endothelial cells involved in cancer angiogenesis, with the proteins of the extracellular matrix, in the circulation, in tissues, and in tumour stroma, as the site of progression and metastatic evolution of the disease. Furthermore, these systems implement the expertise in the development of nanomedicines to the purpose of achieving preferential biodistribution and uptake in cancer tissues, internalisation in cancer cells, and release of the transported drugs at intracellular sites. The assessment of the value of controlling these factors, and their combination, for future developments requires support of biological testing in appropriate mechanistic models, but also imperatively demand confirmation in therapeutically relevant in vivo models for biodistribution, efficacy, and lack of off-target effects. Thus, among many studies, we have tried to point out the results supported by relevant in vivo studies, and we have emphasised in specific sections those addressing the medical needs of drug delivery to brain tumours, as well as the delivery of oligonucleotides modulating gene-dependent pathological mechanism. The latter could constitute the basis of a promising third branch in the therapeutic armamentarium against cancer, in addition to antibody-based agents and to cytotoxic agents.

Improving Drug Penetrability with iRGD Leverages the Therapeutic Response to Sorafenib and Doxorubicin in Hepatocellular Carcinoma

iRGD is a derivative of the integrin-binding peptide RGD, which selectively increases the penetrability of tumor tissue to various coadministered substances in several preclinical models. In this study, we investigated the ability of iRGD to improve the delivery of sorafenib and doxorubicin therapy in hepatocellular carcinoma (HCC) using established mouse models of the disease. A contrast-enhanced MRI method was developed in parallel to assess the in vivo effects of iRGD in this setting. We found that iRGD improved the delivery of marker substances to the tumors of HCC-bearing mice about three-fold without a parallel increase in normal tissues. Control peptides lacking the critical CendR motif had no effect. Similarly, iRGD also selectively increased the signal intensity from tumors in Gd-DTPA-enhanced MRI. In terms of antitumor efficacy, iRGD coadministration significantly augmented the individual inhibitory effects of sorafenib and doxorubicin without increasing systemic toxicity. Overall, our results offered a preclinical proof of concept for the use of iRGD coadministration as a strategy to widen the therapeutic window for HCC chemotherapy, as monitored by Gd-DTPA-enhanced MRI as a noninvasive, clinically applicable method to identify iRGD-reactive tumors.

A tumor-penetrating peptide enhances circulation-independent targeting of peritoneal carcinomatosis

Peritoneal carcinomatosis is a major source of morbidity and mortality in patients with advanced abdominal neoplasms. Intraperitoneal chemotherapy (IPC) is an area of intense interest given its efficacy in ovarian cancer. However, IPC suffers from poor drug penetration into peritoneal tumors. As such, extensive cytoreductive surgery is required prior to IPC. Here, we explore the utility of iRGD, a tumor-penetrating peptide, for improved tumor-specific penetration of intraperitoneal compounds and enhanced IPC in mice. Intraperitoneally administered iRGD significantly enhanced penetration of an attached fluorescein into disseminated peritoneal tumor nodules. The penetration was tumor-specific, circulation-independent, and mediated by the neuropilin-binding RXXK tissue-penetration peptide motif of iRGD. Q-iRGD, which fluoresces upon cleavage, including the one that leads to RXXK activation, specifically labeled peritoneal metastases displaying different growth patterns in mice. Importantly, iRGD enhanced intratumoral entry of intraperitoneally co-injected dextran to approximately 300% and doxorubicin to 250%. Intraperitoneal iRGD/doxorubicin combination therapy inhibited the growth of bulky peritoneal tumors and reduced systemic drug toxicity. iRGD delivered attached fluorescein and co-applied nanoparticles deep into fresh human peritoneal metastasis explants. These results indicate that intraperitoneal iRGD co-administration serves as a simple and effective strategy to facilitate tumor detection and improve the therapeutic index of IPC for peritoneal carcinomatosis.

Tumor-penetrating peptide fused EGFR single-domain antibody enhances cancer drug penetration into 3D multicellular spheroids and facilitates effective gastric cancer therapy

Human tumors, including gastric cancer, frequently express high levels of epidermal growth factor receptors (EGFRs), which are associated with a poor prognosis. Targeted delivery of anticancer drugs to cancerous tissues shows potential in sparing unaffected tissues. However, it has been a major challenge for drug penetration in solid tumor tissues due to the complicated tumor microenvironment. We have constructed a recombinant protein named anti-EGFR-iRGD consisting of an anti-EGFR VHH (the variable domain from the heavy chain of the antibody) fused to iRGD, a tumor-specific binding peptide with high permeability. Anti-EGFR-iRGD, which targets EGFR and αvβ3, spreads extensively throughout both the multicellular spheroids and the tumor mass. The recombinant protein anti-EGFR-iRGD also exhibited antitumor activity in tumor cell lines, multicellular spheroids, and mice. Moreover, anti-EGFR-iRGD could improve anticancer drugs, such as doxorubicin (DOX), bevacizumab, nanoparticle permeability and efficacy in multicellular spheroids. This study draws attention to the importance of iRGD peptide in the therapeutic approach of anti-EGFR-iRGD. As a consequence, anti-EGFR-iRGD could be a drug candidate for cancer treatment and a useful adjunct of other anticancer drugs.

Targeted intracellular delivery of proteins with spatial and temporal control

While a host of methods exist to deliver genetic materials or small molecules to cells, very few are available for protein delivery to the cytosol. We describe a modular, light-activated nanocarrier that transports proteins into cells by receptor-mediated endocytosis and delivers the cargo to the cytosol by light triggered endosomal escape. The platform is based on hollow gold nanoshells (HGN) with polyhistidine tagged proteins attached through an avidity-enhanced, nickel chelation linking layer; here, we used green fluorescent protein (GFP) as a model deliverable cargo. Endosomal uptake of the GFP loaded nanocarrier was mediated by a C-end Rule (CendR) internalizing peptide fused to the GFP. Focused femtosecond pulsed-laser excitation triggered protein release from the nanocarrier and endosome disruption, and the released protein was capable of targeting the nucleoli, a model intracellular organelle. We further demonstrate the generality of the approach by loading and releasing Sox2 and p53. This method for targeting of individual cells, with resolution similar to microinjection, provides spatial and temporal control over protein delivery.

Increased antitumor activity of tumor-specific peptide modified thymopentin

Thymopoietin pentapeptide (thymopentin, TP5), an immunomodulatory peptide, has been successfully used as an immune system enhancer for treating immune deficiency, cancer, and infectious diseases. However, poor penetration into tumors remains a key limitation to the efficacy and application of TP5. iRGD (CRGDK/RGPD/EC) has been introduced to certain anticancer agents, and increased specific tumor penetrability of drugs and cell internalization have been observed. In the present study, we fused this iRGD fragment with the C-terminal of TP5 to yield a new product, TP5-iRGD. Cell attachment assay showed that TP5-iRGD exhibits more extensive attachment to the melanoma cell line B16F10 than wild-type TP5. Tumor cell viability assay showed that iRGD conjugation with the TP5 C-terminus increases the basal antiproliferative activity of the pentapeptide against the melanoma cell line B16F10, the human lung cancer cell line H460, and the human breast cancer cell line MCF-7. Subsequent injections of TP5-iRGD inhibited in vivo melanoma progression more efficiently than the native TP5. Murine spleen lymphocyte proliferation assay also showed that TP5-iRGD and the parent pentapeptide feature nearly identical spleen lymphocyte proliferation activities. We built an integrin αvβ3 and TP5-iRGD computational binding model to investigate the mechanism by which TP5-iRGD promotes increased activity further. Conjugation with iRGD promotes binding to integrin αvβ3, thereby increasing the tumor-homing efficiency of the resultant peptide. These experimental and computational observations of increased TP5-iRGD activity help broaden the usage of TP5 and reflect the great application potential of the peptide as an anticancer agent.

Folate-targeted multifunctional amino acid-chitosan nanoparticles for improved cancer therapy

PURPOSE

Tumor targeting nanomaterials have potential for improving the efficiency of anti-tumoral therapeutics. However, the evaluation of their biological performance remains highly challenging. In this study we describe the synthesis of multifunctional nanoparticles decorated with folic acid-PEG and dual amino acid-modified chitosan (CM-PFA) complexed with DNA and their evaluation in organotypic 2D co-cultures of cancer-normal cells and also on 3D multicellular tumor spheroids models.

METHODS

The physicochemical characterization of CM-PFA multifunctional carriers was performed by FTIR, (1)H NMR and DLS. 2D co-culture models were established by using a 1:2 cancer-to-normal cell ratio. 3D organotypic tumor spheroids were assembled using micromolding technology for high throughput screening. Nanoparticle efficiency was evaluated by flow cytometry and confocal microscopy.

RESULTS

The CM-PFA nanocarriers (126-176 nm) showed hemocompatibility and were internalized by target cells, achieving a 3.7 fold increase in gene expression. In vivo-mimicking 2D co-cultures confirmed a real affinity towards cancer cells and a negligible uptake in normal cells. The targeted nanoparticles penetrated into 3D spheroids to a higher extent than non-targeted nanocarriers. Also, CM-PFA-mediated delivery of p53 tumor suppressor promoted a decrease in tumor-spheroids volume.

CONCLUSION

These findings corroborate the improved efficiency of this delivery system and demonstrate its potential for application in cancer therapy.

Etchable plasmonic nanoparticle probes to image and quantify cellular internalization

There is considerable interest in using nanoparticles as labels or to deliver drugs and other bioactive compounds to cells in vitro and in vivo. Fluorescent imaging, commonly used to study internalization and subcellular localization of nanoparticles, does not allow unequivocal distinction between cell surface-bound and internalized particles, as there is no methodology to turn particles 'off'. We have developed a simple technique to rapidly remove silver nanoparticles outside living cells, leaving only the internalized pool for imaging or quantification. The silver nanoparticle (AgNP) etching is based on the sensitivity of Ag to a hexacyanoferrate-thiosulphate redox-based destain solution. In demonstration of the technique we present a class of multicoloured plasmonic nanoprobes comprising dye-labelled AgNPs that are exceptionally bright and photostable, carry peptides as model targeting ligands, can be etched rapidly and with minimal toxicity in mice, and that show tumour uptake in vivo.

The anoikis effector Bit1 displays tumor suppressive function in lung cancer cells

The mitochondrial Bit1 (Bcl-2 inhibitor of transcription 1) protein is a part of an apoptotic pathway that is uniquely regulated by integrin-mediated attachment. As an anoikis effector, Bit1 is released into the cytoplasm following loss of cell attachment and induces a caspase-independent form of apoptosis. Considering that anoikis resistance is a critical determinant of transformation, we hypothesized that cancer cells may circumvent the Bit1 apoptotic pathway to attain anchorage-independence and tumorigenic potential. Here, we provide the first evidence of the tumor suppressive effect of Bit1 through a mechanism involving anoikis induction in human lung adenocarcinoma derived A549 cells. Restitution of Bit1 in anoikis resistant A549 cells is sufficient to induce detachment induced-apoptosis despite defect in caspase activation and impairs their anchorage-independent growth. Conversely, stable downregulation of Bit1 in these cells significantly enhances their anoikis resistance and anchorage-independent growth. The Bit1 knockdown cells exhibit significantly enhanced tumorigenecity in vivo. It has been previously shown that the nuclear TLE1 corepressor is a putative oncogene in lung cancer, and we show here that TLE1 blocks Bit1 mediated anoikis in part by sequestering the pro-apoptotic partner of Bit1, the Amino-terminal Enhancer of Split (AES) protein, in the nucleus. Taken together, these findings suggest a tumor suppressive role of the caspase-independent anoikis effector Bit1 in lung cancer. Consistent with its role as a tumor suppressor, we have found that Bit1 is downregulated in human non-small cell lung cancer (NSCLC) tissues.

Uncovering a key to the process of metastasis in human cancers: a review of critical regulators of anoikis

PURPOSE

Anoikis ('homelessness' in Greek) is a form of apoptosis following the detachment of cells from the appropriate extracellular matrix (Chiarugi and Giannoni in Biochem Pharmacol 76:1352-1364, 2008). Resistance to anoikis is a critical mediator of metastasis in cancer by enabling cancer cells to survive during invasion and transport in the blood and lymph. Numerous regulators and mechanisms of anoikis in human cancer have been proposed to date. Consequently, the identification of key regulators of anoikis that can be targeted to at least partially restore anoikis sensitivity in cancer cells is important in the development of therapies to treat metastatic cancer.

METHODS

A literature search focusing on the regulators of anoikis in human cancer was performed on the Medline, Embase and Scopus databases.

RESULTS

Mcl-1, Cav-1, Bcl-(xL), cFLIP, 14-3-3ζ and Bit1 appear to regulate anoikis in human cancer by participating in the intrinsic apoptotic pathway, extrinsic apoptotic pathway or caspase-independent pathways. Mcl-1, Cav-1, Bcl-(xL), cFLIP and 14-3-3ζ are suppressors of anoikis, and their upregulation confers anoikis resistance to cancer cells. Bit1 is a promoter of anoikis and is downregulated to confer anoikis resistance in metastatic cancer.

CONCLUSION

Anoikis is a complex process involving the crosstalk between different signalling pathways. The dysregulated expression of key regulators of anoikis that participate in these signalling pathways promotes anoikis resistance in human cancer. These regulators of anoikis might therefore be the targets for developing therapies to overcome anoikis resistance in metastatic cancer.