Antitumor protein therapy; application of the protein transduction domain to the development of a protein drug for cancer treatment

DNA origami drives gene expression in a human cell culture system

Self-assembling DNA nanoparticles have the potential to significantly advance the targeted delivery of molecular cargo owing to their chemical and architectural flexibility. Recently, it has been demonstrated that the genetic code embedded in DNA nanoparticles produced by the method of DNA origami or related techniques can be recognized and copied by RNA polymerase in vitro. Further, sculpted DNA nanoparticles can serve as a substrate for Cas9-mediated gene modification and gene expression in cell culture. In the present study, we further investigate the ability of DNA origami nanoparticles to be expressed in a human cell line with emphasis on the impact of single-stranded DNA (ssDNA) domains and the contributions of the architectural disposition of genetic control elements, namely promoter and enhancer sequences. Our findings suggest that while cells possess the remarkable capability to express genes within highly folded architectures, the presence and relative density and location of ssDNA domains appears to influence overall levels of gene expression. These results suggest that it may be possible to nuance folded DNA nanoparticle architecture to regulate the rate and/or level of gene expression. Considering the highly malleable architecture and chemistry of self-assembling DNA nanoparticles, these findings motivate further exploration of their potential as an economic nanotechnology platform for targeted gene editing, nucleic acid-based vaccines, and related biotherapeutic applications.

Advancement and application of novel cell-penetrating peptide in cancer management

Cell-penetrating peptides (CPPs) are small amino acid sequences with the potential to enter cell membranes. Along with nucleic acids, large proteins, and other chemical compounds, they can deliver several bioactive cargos inside cells. Numerous CPPs have been extracted from natural or synthetic materials since the discovery of the first CPP. In the past few decades, a significant variety of studies have shown the potential of CPPs to cure different diseases. The low toxicity in peptide compared to other drug delivery carriers is a significant benefit of CPP-based therapy, in addition to the high efficacy brought about by swift and effective delivery. A significant tendency for intracellular DNA delivery may also be observed when nanoparticles and the cell penetration peptide are combined. CPPs are frequently used to increase intracellular absorption of nucleic acid, and other therapeutic agents inside the cell. Due to long-term side effects and possible toxicity, its implementation is restricted. The use of cell-permeating peptides is a commonly used technique to increase their intracellular absorption. Additionally, CPPs have lately been sought for application in vivo, following their success in cellular studies. This review will go through the numerous CPPs, the chemical modifications that improve their cellular uptake, the various means for getting them across cell membranes, and the biological activity they acquire after being conjugate with specific chemicals.

Fundamental concepts of protein therapeutics and spacing in oncology: an updated comprehensive review

Current treatment regimens in cancer cases cause significant side effects and cannot effectively eradicate the advanced disease. Hence, much effort has been expended over the past years to understand how cancer grows and responds to therapies. Meanwhile, proteins as a type of biopolymers have been under commercial development for over three decades and have been proven to improve the healthcare system as effective medicines for treating many types of progressive disease, such as cancer. Following approving the first recombinant protein therapeutics by FDA (Humulin), there have been a revolution for drawing attention toward protein-based therapeutics (PTs). Since then, the ability to tailor proteins with ideal pharmacokinetics has provided the pharmaceutical industry with an important noble path to discuss the clinical potential of proteins in oncology research. Unlike traditional chemotherapy molecules, PTs actively target cancerous cells by binding to their surface receptors and the other biomarkers particularly associated with tumorous or healthy tissue. This review analyzes the potential and limitations of protein therapeutics (PTs) in the treatment of cancer as well as highlighting the evolving strategies by addressing all possible factors, including pharmacology profile and targeted therapy approaches. This review provides a comprehensive overview of the current state of PTs in oncology, including their pharmacology profile, targeted therapy approaches, and prospects. The reviewed data show that several current and future challenges remain to make PTs a promising and effective anticancer drug, such as safety, immunogenicity, protein stability/degradation, and protein-adjuvant interactions.

Redox-Responsive Polymeric Nanocomplex for Delivery of Cytotoxic Protein and Chemotherapeutics

Responsive delivery of anticancer proteins into cells is an emerging field in biological therapeutics. Currently, the delivery of proteins is highly compromised by multiple successive physiological barriers that reduce the therapeutic efficacy. Hence, there is a need to design a robust and sustainable nanocarrier to provide suitable protection of proteins and overcome the physiological barriers for better cellular accumulation. In this work, polyethylenimine (PEI) cross-linked by oxaliplatin(IV) prodrug (oxliPt(IV)) was used to fabricate a redox-responsive nanocomplex (PEI-oxliPt(IV)@RNBC/GOD) for the delivery of a reactive oxygen species-cleavable, reversibly caged RNase A protein (i.e., RNase A nitrophenylboronic conjugate, RNBC) and glucose oxidase (GOD) in order to realize efficient cancer treatment. The generation of hydrogen peroxide by GOD can uncage and restore the enzymatic activity of RNBC. On account of the responsiveness of the nanocomplex to highly reducing cellular environment, it would dissociate and release the protein and active oxaliplatin drug, causing cell death by both catalyzing RNA degradation and inhibiting DNA synthesis. As assessed by the RNA degradation assay, the activity of the encapsulated RNBC was recovered by the catalytic production of hydrogen peroxide from GOD and glucose substrate overexpressed in cancer cells. Monitoring of the changes in nanoparticle size confirmed that the nanocomplex could dissociate in the reducing environment, with the release of active oxaliplatin drug and protein. Confocal laser scanning microscopy (CLSM) and flow cytometry analysis revealed highly efficient accumulation of the nanocomplex as compared to free native proteins. In vitro cytotoxicity experiments using 4T1 cancer cells showed ∼80% cell killing efficacy, with highly efficient apoptosis induction. Assisted by the cationic polymeric carrier, it was evident from CLSM images that intracellular delivery of the therapeutic protein significantly depleted the RNA level. Thus, this work provides a promising platform for the delivery of therapeutic proteins and chemotherapeutic drugs for efficient cancer treatment.

Actin stabilizer TAGLN2 potentiates adoptive T cell therapy by boosting the inside-out costimulation via lymphocyte function-associated antigen-1

Correct temporal and spatial control of actin dynamics is essential for the cytotoxic T cell effector function against tumor cells. However, little is known whether actin engineering in tumor-targeted T cells can enhance their antitumor responses, thereby potentiating the adoptive T cell therapy. Here, we report that TAGLN2, a 22-KDa actin-stabilizing protein which is physically associated with lymphocyte function-associated antigen-1 (LFA-1), potentiates the OTI TCR CD8⁺ T cells to kill the intercellular adhesion molecule-1 (ICAM-1)-positive/OVA-presenting E0771 cells, but not ICAM-1-negative OVA-B16F10 cells, suggesting an 'inside-out' activation of LFA-1, which causes more efficient immunological synapse formation between T cells and tumor cells. Notably, recombinant TAGLN2 fused with the protein transduction domain (TG2P) overcame the disadvantages of viral gene delivery, leading to a significant reduction in tumor growth in mice. TG2P also potentiated the CD19-targeted, chimeric antigen receptor (CAR)-modified T cells to kill Raji B-lymphoma cells. Our findings indicate that activating the TAGLN2-actin-LFA-1 axis is an effective strategy to potentiate the adoptive T-cell immunotherapy.

Carbon nanospheres mediated nuclear delivery of SMAR1 protein (DNA binding domain) controls breast tumor in mice model

Aim: To investigate anticancer activity of the DNA binding domain of SMAR1 (His 5) in vitro and in vivo. Materials & methods: His 5 was conjugated to hydrothermally synthesized carbon nanospheres (CNs). Anticancer activity of CNs-His 5 was evaluated in vitro and in vivo. Results: CNs- His 5 significantly reduced cyclin D1 levels in MDA-MB-231 cells. Tumor bearing Balb/c mice injected with CNs-His 5 showed approximately 62% tumor regression and significantly reduced 18FDG uptake. Caspases assay and IHC staining confirmed tumor growth inhibition, which could be attributed to apoptotic, antiproliferative and antiangiogenic activities of His 5. Conclusion: DNA binding domain of the SMAR1 protein (His 5) has potent anticancer activity and its CNs mediated delivery could control breast tumor in mice model.

Cell-Specific Promoters Enable Lipid-Based Nanoparticles to Deliver Genes to Specific Cells of the Retina In Vivo

Non-viral vectors, such as lipid-based nanoparticles (liposome-protamine-DNA complex [LPD]), could be used to deliver a functional gene to the retina to correct visual function and treat blindness. However, one of the limitations of LPD is the lack of cell specificity, as the retina is composed of seven types of cells. If the same gene is expressed in multiple cell types or is absent from one desired cell type, LPD-mediated gene delivery to every cell may have off-target effects. To circumvent this problem, we have tested LPD-mediated gene delivery using various generalized, modified, and retinal cell-specific promoters. We achieved retinal pigment epithelium cell specificity with vitelliform macular dystrophy (VMD2), rod cell specificity with mouse rhodopsin, cone cell specificity with red/green opsin, and ganglion cell specificity with thymocyte antigen promoters. Here we show for the first time that cell-specific promoters enable lipid-based nanoparticles to deliver genes to specific cells of the retina in vivo. This work will inspire investigators in the field of lipid nanotechnology to couple cell-specific promoters to drive expression in a cell- and tissue-specific manner.

Enhanced Peptide delivery into cells by using the synergistic effects of a cell-penetrating Peptide and a chemical drug to alter cell permeability

Cell-penetrating peptides (CPPs) are short, often hydrophilic peptides that can deliver many kinds of molecules into cells and that are likely to serve as a useful tool of future biotherapeutics. However, CPPs application is limited because of insufficient transduction efficiency and unpredictable cellular localization. Here, we investigated the enhancement of 1,2-benzisothiazolin-3-one (BIT) on the uptake of a synthetic fluorescent TAT and a TAT-conjugated green fluorescent protein (GFP) or pro-apoptotic peptide KLA and evaluated its toxicity in various cell lines. Our results showed that BIT pretreatment can enhance the penetration efficiency of TAT and its fusion peptide. In addition, the fluorescence of the peptide conjugate at effective doses was well-distributed in the intracellular of different cell lines without membrane perforation or detectable cytotoxicity. The internalization of the peptides was serum-dependent and temperature-independent. These findings imply that BIT may serve as a newly found delivery enhancer that is suitable for improving the penetration of CPPs.

siRNA suppression of hTERT using activatable cell-penetrating peptides in hepatoma cells

Activatable cell-penetrating peptides (aCPPs) allow non-viral, low cytotoxic and selective delivery of compounds into target cells for cancer therapy. In tumour cells, up-regulation of human telomerase reverse transcriptase (hTERT) frequently occurs and is being considered as a target in cancer diagnosis and treatment. siRNA sequence that target hTERT mRNA can silence the gene and reduce hTERT protein expression to reduce cell proliferation and inhibit cell growth. In our study, we tested a matrix metalloproteinase-2 (MPP2) aCPP in delivering hTERT siRNA into hepatocellular carcinoma cells (SMMC-7721) to silence the hTERT gene. Cultured SMMC-7721 cells were transfected with a complex of aCPPs and hTERT-specific siRNA-encoding or control plasmids. Compared with cells treated with the complex of control plasmid–CPPs, cells treated with the hTERT-specific siRNA-encoding plasmid–CPP complex had a prolonged G₁-phase, but a shorter G₂/S-phase, indicating a G₁-arrest. Treatment with the hTERT-specific siRNA resulted in a significant decrease (by 26%; P<0.05) in hTERT mRNA levels. The aCPPs tested in this study provides a non-viral delivery of siRNA into cancer cells to silence target genes in cancer therapy.

In the present study, we delivered human telomerase reverse transcriptase (hTERT) siRNA into SMMC-7721 hepatoma cells using a matrix metalloproteinase-2 (MMP2)-activatable cell-penetrating peptide (aCPP). The siRNA subsequently induced down-regulation of the hTERT gene and G₁-arrest, implicating the utility of this delivery system in cancer therapy.

DNA-interactive properties of crotamine, a cell-penetrating polypeptide and a potential drug carrier

Crotamine, a 42-residue polypeptide derived from the venom of the South American rattlesnake Crotalus durissus terrificus, has been shown to be a cell-penetrating protein that targets chromosomes, carries plasmid DNA into cells, and shows specificity for actively proliferating cells. Given this potential role as a nucleic acid-delivery vector, we have studied in detail the binding of crotamine to single- and double-stranded DNAs of different lengths and base compositions over a range of ionic conditions. Agarose gel electrophoresis and ultraviolet spectrophotometry analysis indicate that complexes of crotamine with long-chain DNAs readily aggregate and precipitate at low ionic strength. This aggregation, which may be important for cellular uptake of DNA, becomes less likely with shorter chain length. 25-mer oligonucleotides do not show any evidence of such aggregation, permitting the determination of affinities and size via fluorescence quenching experiments. The polypeptide binds non-cooperatively to DNA, covering about 5 nucleotide residues when it binds to single (ss) or (ds) double stranded molecules. The affinities of the protein for ss- vs. ds-DNA are comparable, and inversely proportional to salt levels. Analysis of the dependence of affinity on [NaCl] indicates that there are a maximum of ∼3 ionic interactions between the protein and DNA, with some of the binding affinity attributable to non-ionic interactions. Inspection of the three-dimensional structure of the protein suggests that residues 31 to 35, Arg-Trp-Arg-Trp-Lys, could serve as a potential DNA-binding site. A hexapeptide containing this sequence displayed a lower DNA binding affinity and salt dependence as compared to the full-length protein, likely indicative of a more suitable 3D structure and the presence of accessory binding sites in the native crotamine. Taken together, the data presented here describing crotamine-DNA interactions may lend support to the design of more effective nucleic acid drug delivery vehicles which take advantage of crotamine as a carrier with specificity for actively proliferating cells.

Applications of cell-penetrating peptides for tumor targeting and future cancer therapies

Cell-penetrating peptides provide a highly promising strategy for intracellular drug delivery. One relevant clinical application of cell-penetrating peptides is cancer therapeutics. Peptide based delivery could increase the uptake of drugs in tumor cells and thereby increase the efficacy of the treatment, either of conventional small molecular drugs or oligonucleotide based therapeutics. This review is focused on the cancer applications of cell penetrating peptides as delivery systems; different aspects of drug loading, cargoes and delivery are discussed together with methods for targeted delivery, activatable cell-penetrating peptides and transducible agents coupled to cell-penetrating peptides.

MDM2 protein-mediated ubiquitination of numb protein: identification of a second physiological substrate of MDM2 that employs a dual-site docking mechanism

The E3 ubiquitin ligase, MDM2, uses a dual-site mechanism to ubiquitinate and degrade the tumor suppressor protein p53, involving interactions with the N-terminal hydrophobic pocket and the acidic domain of MDM2. The results presented here demonstrate that MDM2 also uses this same dual-site mechanism to bind to the cell fate determinant NUMB with both the N-terminal hydrophobic pocket and the acidic domain of MDM2 also involved in forming the interaction with NUMB. Furthermore, the acidic domain interactions are crucial for MDM2-mediated ubiquitination of NUMB. Contrary to p53, where two separate domains form the interface with MDM2, only one region within the phosphotyrosine binding domain of NUMB (amino acids 113-148) mediates binding to both these regions of MDM2. By binding to both domains on MDM2, NUMB disrupts the MDM2-p53 complex and MDM2-catalyzed ubiquitination of p53. Therefore, we have identified the mechanism NUMB uses to regulate the steady-state levels of the p53 in cells. By targeting the acidic domain of MDM2 using acid domain-binding ligands we can overcome MDM2-mediated ubiquitination and degradation of NUMB impacting on the stabilization of p53 in cells. Furthermore, delivery of MDM2 acid domain-binding ligands to cancer cells promotes p53-dependent growth arrest and the induction of apoptosis. This highlights the dual-site mechanism of MDM2 on another physiological substrate and identifies the acid domain as well as N terminus as a potential target for small molecules that inhibit MDM2.

Cell-penetrating peptides, PepFects, show no evidence of toxicity and immunogenicity in vitro and in vivo

Cell-penetrating peptide based vehicles have been developed for the delivery of different payloads into the cells in culture and in animals. However, several biological features, among which is the tendency to trigger innate immune response, limit the development of highly efficient peptide-based drug delivery vectors. This study aims to evaluate the influence of transportan 10 (TP10) and its chemically modified derivatives, PepFects (PFs), on the innate immune response of the host system. PFs have shown high efficiency in nucleic acid delivery in vitro and in vivo; hence, the estimation of their possible toxic side effects would be of particular interest. In this study, we analyzed cytotoxic and immunogenic response of PF3, PF4, and PF6 peptides in monocytic leukemia and peripheral blood mononuclear cell lines. In comparison with amphipathic PFs, TP10, TAT, stearyl-(RxR)(4) peptides, and the most widely used transfection reagents Lipofectamine 2000 and Lipofectamine RNAiMAX were also analyzed in this study. IL-1β, IL-18, and TNF-α cytokine release was detected using highly sensitive enzyme-linked immunosorbent assay (ELISA). Cell viability was detected by measuring the activity of cellular enzymes that reduce water-soluble tetrazolium salts to formazan dyes and apoptosis was evaluated by measuring the levels of caspase-1 and caspase-3/7 over untreated cells. All peptides were found to be nontoxic and nonimmunogenic in vitro at the concentrations of 10 μM and 5 μM, respectively, and at a dose of 5 mg/kg in vivo, suggesting that these CPPs exhibit a promising potential in the delivery of therapeutic molecules into the cell without risks of toxicity and inflammatory reactions.

Chemotherapeutic effects of bioassay-guided extracts of the American cockroach, Periplaneta americana

The organic extract of Periplaneta americana L. (Dictyoptera; Blattidae) has been traditionally used in southwestern China as an alternative medicine against disorders such as hepatitis, trauma, gastric ulcers, burns, and heart disease. The present study describes bioassay-guided purification and chemotherapeutic evaluation of the 60% ethanolic fraction of P americana organic extracts (PAE60). The most effective cytotoxic fraction was determined by way of repeated in vitro screenings against 12 distinct cultured human carcinoma cell lines: Eca 109, BGC823, HO8910, LS174T, CNE, HeLa, K562, PC-3, A549, BEL 7404, HL-60, and KB, followed by in vivo antitumor assays of the lead fraction (PAE60). The complexity of enriched active fraction was qualitatively evaluated using thin layer chromatography. Reconstituted PAE60 was effective at inhibiting HL-60, KB, CNE, and BGC823 cell growth with IC(50) values <20 µg mL-(1). PAE60 reduced tumor growth in S180-bearing immunocompetent mice by 72.62% after 10 days following oral doses of 500 mg kg d-(1) compared with 78.75% inhibition following 40 mg kg d-(1) of cyclophosphamide (CTX). Thymus and spleen indices of S180-bearing mice treated with PAE60 were significantly greater (P < .05) than CTX treatment groups, suggesting potential immunomodulation of antitumor host defenses by PAE60. Antiviral activity was also investigated and PAE60 inhibited herpes simplex type-2 replication (IC(50) = 4.11 ± 0.64 µg mL-(1)) with a selectivity index (CC(50) to IC(50) ratio) of 64.84 in Vero cells but was less effective on type-1 virus (IC(50) of 25.6 ± 3.16 µg mL-(1)). These results support future clinical trials on P. americana as an alternative or complementary medicinal agent.

A designed cell-permeable aptamer-based corepressor peptide is highly specific for the androgen receptor and inhibits prostate cancer cell growth in a vector-free mode

The repression of the androgen receptor (AR) activity is a major objective to inhibit prostate cancer growth. One underlying mechanism for efficient hormone therapy is based on corepressors that inactivate the AR. In line with this, castration-resistant prostate cancer is associated with malfunction or reduced corepressor action. To overcome this, the overexpression of endogenous corepressors, however, affects many other transcription factors. Therefore, an AR-specific corepressor could be of advantage. Using a yeast peptide aptamer two-hybrid screen with the full-length human AR, we identified a short amino acid-stretch that binds specifically to the human AR in yeast and in mammalian cells and not to the closely related progesterone or glucocorticoid receptors. Furthermore, fused to a silencing domain, this aptamer-based corepressor (AB-CoR) exhibits corepressor activity by inhibiting both the AR-mediated transactivation and expression of the AR target gene PSA. Furthermore, stable expression of the AB-CoR inhibits growth of human LNCaP prostate cancer cells. Moreover, we generated a cell-permeable AB-CoR by fusing a protein transduction domain to establish a vector-free transport system. Treatment of LNCaP cells with the bacterially expressed and affinity-purified cell-permeable AB-CoR peptide resulted in a significant inhibition of both AR-mediated transactivation and prostate cancer cell proliferation. Thus, generation of a novel AR-specific aptamer-based corepressor may present a vector-free inhibition of AR-dependent prostate cancer growth as a novel approach.

Fusion protein based on Grb2-SH2 domain for cancer therapy

Epidermal growth factor receptor (EGFR) is one of the very attractive targets for cancer therapy. In this study, we generated fusion proteins containing one or two Src-homology 2 (SH2) domains of growth factor receptor bound protein 2 (Grb2), which bind to phosphorylated EGFR, added with HIV-1 transactivating transcription for cell membrane penetration (termed TSF and TSSF, respectively). We examined if they can interfere Grb2-mediated signaling pathway and suppress tumor growth as expected from the lack of SH3 domain, which is necessary to intermediate EGFR-Grb2 cell signaling, in the fusion proteins. The transduction efficiency of TSSF was similar to that of TSF, but the binding activity of TSSF to EGFR was higher than that of TSF. Treatment of EGFR-overexpressing cells showed that TSSF decreased p42-ERK phosphorylation, while TSF did not. Both the proteins delayed cell growth but did not induce cell death in culture. TSSF also significantly suppressed tumor growth in vivo under consecutive administration. In conclusion, TSSF showed an ability to inhibit EGFR-Grb2 signaling and could have a potential to treat EGFR-activated cancer.

Anticancer genes: inducers of tumour-specific cell death signalling

Recent studies have revealed a new class of genes encoding proteins with specific anticancer activity. Upon ectopic expression, these factors cause cell death specifically in tumour cells by apoptosis, autophagy or mitotic catastrophe, yet normal cells are spared. Some of these genes or their encoded proteins are in clinical development and show promising results, and their signalling pathways are currently under intense investigation. Defining these genes as anticancer genes, we review what is known about their functions, the specific cell death signals they induce and the status of cancer therapy approaches that emulate their function. Systematic screening for such anticancer genes might lead to the identification of a repertoire of signalling pathways directed against cellular alterations that are specific for tumour cells.

Tat-Mediated Peptide Intervention in Analgesia and Anesthesia

Membrane-permeable peptide carriers are attractive drug delivery tools. Among such carriers, the protein transduction domain (PTD) of the human immunodeficiency virus-type 1 Tat protein is most frequently used and has been successfully shown to deliver a large variety of cargoes. The Tat PTD can facilitate the uptake of large, biologically active molecules into mammalian cells, and recent studies have shown that it can mediate the delivery of different cargoes into tissues throughout a living organism. Given that the Tat PTD-mediated delivery is size-independent, this technology could make previously non-applicable large molecules usable to modulate biological function in vivo and treat human diseases. It is likely that the peptide carrier-mediated intracellular delivery process encompasses multiple mechanisms, but endocytic pathways are the predominant internalization routes. Tat PTD has been successfully used in preclinical models for the study of cancer, ischemia, inflammation, analgesia, and anesthesia. Our recent studies have shown that intraperitoneally injected fusion Tat peptide Tat-PSD-95 PDZ2 can be delivered into the spinal cord to dose-dependently disrupt protein-protein interactions between PSD-95 and NMDA receptors. This peptide significantly inhibits chronic inflammatory pain and reduces the threshold for halothane anesthesia. The ability of the Tat PTD to target any cell is advantageous in some respects. However, the drug delivery system will be more attractive if we can modify the Tat PTD to deliver cargo only into desired organs to avoid possible side effects.

TAT-based drug delivery system--new directions in protein delivery for new hopes?

There has been great progress in the use of TAT-based drug delivery systems for the delivery of different macromolecules into cells in vitro and in vivo, thus circumventing the bioavailability barrier that is a problem for so many drugs. There are many advantages to using this system, such as the ability to deliver these cargoes into all types of cells in culture and into all organs in vivo. This system can even deliver cargoes into the brain across the blood-brain barrier. In addition, the ability to target specific intracellular sub-localizations such as the nuclei, the mitochondria and lysosomes further expands the possibilities of this drug delivery system to the development of sub-cellular organelle-targeted therapy. The therapeutic applications seem almost unlimited, and the use of the TAT-based delivery system has extended from proteins to a large variety of cargoes such as oligonucleotides, imaging agents, low molecular mass drugs, nanoparticles, micelles and liposomes. In this review the most recent advances in the use of the TAT-based drug delivery system will be described, mainly discussing TAT-mediated protein delivery and the use of the TAT system for enzyme replacement therapy.

Expression and purification of ZEBRA fusion proteins and applications for the delivery of macromolecules into mammalian cells

The recent development of peptide carriers for efficient and specific delivery of biologically active molecules into mammalian cells represents a major advance in the study of both normal and uncontrolled cell growth. In the past few years, this technology has been successfully applied to the delivery of therapeutic molecules in animal models, and now some of these carriers are available in the clinic for the treatment of some human diseases. This unit describes the production, in a bacterial expression system, of reporter proteins (EGFP and beta-galactosidase) fused to a transduction domain of the Epstein-Barr virus ZEBRA protein, as well as purification of the fusion proteins. The purified fusion proteins can be added to any of a large spectrum of mammalian cells and the internalization process measured by flow cytometry and fluorescence microscopy on live cells. Fluorescence microscopy on fixed cells is used to study their intracellular distribution.

Membrane transducing activity of recombinant Hoxc8 protein and its possible application as a gene delivery vector

In order to examine whether the Hoxc8 protein can deliver nucleic acid into mammalian cells, we designed several Hoxc8-derived recombinant proteins to be synthesized as glutathione S-transferase (GST) fused forms in E. coli (GST-Hoxc8(1-242), containing a full length of Hoxc8; GST-Hoxc8(152-242), possessing a deletion of the acidic N-terminus of Hoxc8; GST-Hoxc8(149-208), which contained the homeodomain only). After labeling these proteins with Oregon 488, we examined their membrane transduction ability under the fluorescence microscope and verified that all three proteins showed similar transduction efficiency. The ability of the proteins to form in vitro protein-DNA complexes was analyzed on agarose gel; both GST-Hoxc8(1-242) and GST-Hoxc8(149-208) formed complexes. In contrast, the GST-Hoxc8(152-242) protein did not form a complex. The GST-Hoxc8(149-208) protein formed a complex with DNA at a mass ratio of 1ú1 (DNAúprotein), and GST-Hoxc8(1-242) formed a complex at a mass ratio of 1ú5. When the DNA (pDsRed1-C1) and protein complexes were added to culture media containing mammalian cells, the cells uptook the complexes, which was indicated by red fluorescence expression under the fluorescent microscope. These results indicate that recombinant Hoxc8 derivatives that harbor a homeodomain are able to traverse the mammalian cellular membrane. DNA that is bound to the recombinant derivatives can be carried across the membrane as well. This process could be applied in the development of a useful delivery vector for gene therapy in the future.

Cell-permeable hypoxia-inducible factor-1 (HIF-1) antagonists function as tumor radiosensitizers

Hypoxia is a common phenomenon in human solid tumors and has been considered as an important, independent negative prognostic factor for response to treatment and survival of tumor patients. Hypoxia-inducible factor-1 (HIF-1) is the central transcription factor which is activated by hypoxia and modulates the expression of many genes involved in cell metabolism, proliferation, apoptosis, angiogenesis. Recently, it has been reported that HIF-1 contributes to tumor radioresistance by upregulating survivin expression under hypoxic conditions. Moreover, in hypoxic tumor cells, HIF-1 dependent signal transduction pathway is activated and could be further enhanced by radiation, thereby providing survival signals to adjacent vascular endothelial cells by upregulation of VEGF and bFGF and resulting in tumor radioresistance through vascular radioprotection. Recent research revealed that the stability of HIF-1alpha, one of the two subunits of HIF-1, determines the whole HIF-1 activity and the C-terminal transactivation domain of HIF-1alpha could reduce HIF-1 activity when overexpressed in tumor cells by disruption of the assembly of HIF-1 transcription complex. Therefore, we postulate that fusion with protein transduction domains would overcome the inability of C-terminal transactivation domain of HIF-1alpha to cross cellular membrane. Thus the recombinant fusion proteins could serve as cell-permeable HIF-1 antagonists, function as both inhibitors of tumor angiogenesis and tumor radiosensitizers, and would be widely used in clinical settings to improve tumor response to radiotherapy.

A truncated Ah receptor blocks the hypoxia and estrogen receptor signaling pathways: a viable approach for breast cancer treatment

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor which requires heterodimerization with the Ah receptor nuclear translocator (Arnt) for function. Arnt is also a dimerization partner of the hypoxia inducible factor 1alpha (HIF-1alpha) for the hypoxia signaling. Additionally, Arnt is found to be a potent coactivator of the estrogen receptor (ER) signaling. Thus we examined whether the presence of an increased amount of AhR may suppress both the HIF-1alpha and ER signaling pathways by sequestering Arnt. We tested our hypothesis using a human AhR construct C Delta553 which is capable of heterodimerizing with Arnt in the absence of a ligand. Transient transfection studies using a corresponding luciferase reporter plasmid in MCF-7 cells showed that C Delta553 effectively suppressed the AhR, HIF-1alpha, and ER signaling pathways. Reverse transcription/real-time QPCR data showed that C Delta553 blocked the up-regulation of the target genes controlled by AhR (CYP1A1), HIF-1alpha (VEGF, aldolase C, and LDH-A), and ER (GREB1, pS2, and c-myc) in MCF-7 cells. Since both HIF-1alpha and ER are highly active in the ER-positive breast cancer, C Delta553 has the potential to be developed as a protein drug to treat breast cancer by blocking these two signaling pathways.