Gene therapy targeting to tumor endothelium

Doxorubicin and anti-VEGF siRNA co-delivery via nano-graphene oxide for enhanced cancer therapy in vitro and in vivo

BACKGROUND

Graphene oxide (GO) has attracted intensive interest in biological and medical fields in recent years due to its unique physical, chemical, and biological properties. In our previous work, we proved that GO could deliver small interfering RNA (siRNA) into cells and downregulate the expression of the desired gene.

METHODS

This study investigated the potential of a modified GO nanocarrier for co-delivery of siRNA and doxorubicin (DOX) for enhanced cancer therapy. Fourier transform infrared spectroscopy, laser particle size analyzer, UV-visible spectroscopy, gel electrophoresis retardation, and in vitro release assay were studied.

RESULTS

The results of real-time polymerase chain reaction revealed that the expression of vascular endothelial growth factor (VEGF) mRNA was decreased 46.84%±3.72% (mean ± SD). Enzyme-linked immunosorbent assay indicated that the expression of VEGF protein was down-regulated to 52.86%±1.10% (mean ± SD) in vitro. In vivo tumor growth assay GO-poly-l-lysine hydrobromide/folic acid (GPF)/DOX/siRNA exhibited gene silencing and tumor inhibition (66.95%±2.35%, mean ± SD) compared with naked siRNA (1.62%±1.47%, mean ± SD) and DOX (33.63%±5.85%, mean ± SD). GPF/DOX/siRNA exhibited no testable cytotoxicity.

CONCLUSION

The results indicated that co-delivery of siRNA and DOX by GPF could be a promising application in tumor clinical therapy.

Functionalized graphene oxide for anti-VEGF siRNA delivery: preparation, characterization and evaluation in vitro and in vivo

GO–PLL–SDGR/VEGF-siRNA inhibits tumor growth as a tumor targeting delivery system.

Implementation of Nanoparticles in Cancer Therapy

Cancer is a wide group of diseases and generally characterized by uncontrolled proliferation of cells whose metabolic activities are disrupted. Conventionally, chemotherapy, radiotherapy, and surgery are used in the treatment of cancer. However, in theory, even a single cancer cell may trigger recurrence. Therefore, these treatments cannot provide high survival rate for deadly types. Identification of alternative methods in treatment of cancers is inevitable because of adverse effects of conventional methods. In the last few decades, nanotechnology developed by scientists working in different disciplines—physics, chemistry, and biology—offers great opportunities. It is providing elimination of both circulating tumor cells and solid cancer cells by targeting cancer cells. In this chapter, inadequate parts of conventional treatment methods, nanoparticle types used in new treatment methods of cancer, and targeting methods of nanoparticles are summarized; furthermore, recommendations of future are provided.

Impact of RGD Peptide Tethering to IL24/mda-7 (Melanoma Differentiation Associated Gene-7) on Apoptosis Induction in Hepatocellular Carcinoma Cells

BACKGROUND

Melanoma differentiation-associated gene-7 (MDA-7)/interleukin-24 (IL-24), a unique tumor suppressor gene, has killing activity in a broad spectrum of cancer cells. Herein, plasmids producing mda-7 proteins fused to different RGD peptides (full RGD4C and shortened RGD, tRGD) were evaluated for apoptosis induction with a hepatocellular carcinoma cell line, Hep-G2. The study aim was to improve the apoptosis potency of mda-7 by tethering to RGD peptides.

MATERIALS AND METHODS

Three plasmids including mda-7, mda-7-RGD and mda-7-tRGD genes beside a control vector were transfected into Hep-G2 cells. After 72 hours incubation, cell viability was evaluated by MTT assay. In addition, the rate of apoptosis was analyzed by flow cytometry using PI/annexin staining. To detect early events in apoptosis, 18 hours after transfection, expression of the BAX gene was quantified by real time PCR. Modeling of proteins was also performed to extrapolate possible consequences of RGD modification on their structures and subsequent attachment to receptors.

RESULTS AND CONCLUSIONS

In MTT assays, while all mda-7 forms showed measurable inhibition of proliferation, unmodified mda-7 protein exhibited most significant effect compared to control plasmid (P<0.001). Again, flow cytometry analysis showed a significant apoptosis induction by simple mda-7 gene but not for those RGD-fused mda-7 proteins. These findings were also supported by expression analysis of BAX gene (P<0.001). Protein modelling analysis revealed that tethering RGD at the end of IL-24/Mda7 disrupt attachment to cognate receptor, IL-20R1/ IL-20R2. In conclusion, fusion of RGD4C and shortened RGD peptides to carboxyl terminal of mda7, not only reduce apoptosis property in vitro but also disrupt receptor attachment as demonstrated by protein modelling.

Olesoxime protects embryonic cortical neurons from camptothecin intoxication by a mechanism distinct from BDNF

BACKGROUND AND PURPOSE

Olesoxime is a small cholesterol-oxime promoting rat embryonic motor neurons survival in the absence of trophic factors. Because olesoxime can substitute for neurotrophic factors in many situations, and to gain further understanding of its mechanism of action, we wondered if it could prevent neuronal death induced by camptothecin (CPT) and compared its effects with those of brain-derived neurotrophic factor (BDNF).

EXPERIMENTAL APPROACH

E17 rat embryonic cortical neurons were treated with olesoxime, BDNF or vehicle and intoxicated with CPT. Caspase-dependent and caspase-independent death pathways along with pro-survival pathways activation were explored.

KEY RESULTS

As previously reported for BDNF, olesoxime dose-dependently delayed CPT-induced cell death. Both compounds acted downstream of p53 activation preventing cytochrome c release and caspases activation. When caspase activation was blocked, both olesoxime and BDNF provided additional neuroprotective effect, potentially through the prevention of apoptosis-inducing factor release from mitochondria. While BDNF activates both the PI3K/Akt and the ERK pathway, olesoxime induced only a late activation of the ERK pathways, which did not seem to play a major role in its neuroprotection against CPT. Rather, our results favour preserved mitochondrial membrane integrity by olesoxime.

CONCLUSIONS AND IMPLICATIONS

Albeit different, olesoxime and BDNF mechanisms for neuroprotection converge to preserve mitochondrial function. These findings emphasize the importance of targeting the mitochondria in the process of neurodegeneration. Importantly olesoxime, by mimicking neurotrophin pro-survival activities without impacting PI3K/Akt and ERK signalling, may have greater therapeutic potential in many diseases where neurotrophins were considered as a therapeutic solution.

Intratumoral interleukin-2/agonist CD40 antibody drives CD4+ -independent resolution of treated-tumors and CD4+ -dependent systemic and memory responses

Targeting interleukin-2 (IL-2) and/or agonist anti-CD40 antibody (Ab) into tumors represents an effective vaccination strategy that avoids systemic toxicity and resolves treated-site tumors. Here, we examined IL-2 and/or anti-CD40 Ab-driven local versus systemic T cell function and the installation of T cell memory. Single tumor studies showed that IL-2 induced a potent CD4+ and CD8+ T cell response that was limited to the draining lymph node and treated-site tumor, and lymph node tumor-specific CD8+ T cells did not upregulate CD44. A two-tumor model showed that while IL-2-treated-site tumors resolved, distal tumors continued to grow, implying limited systemic immunity. In contrast, anti-CD40 Ab treatment with or without IL-2 expanded the systemic T cell response to non-draining lymph nodes, and distal tumors resolved. Tumor-specific T cells in lymph nodes of anti-CD40 Ab ± IL-2-treated mice upregulated CD44, demonstrating activation and transition to effector/memory migratory cells. While CD40-activated CD4+ T cells were not required for eradicating treated-site tumors, they, plus CD8+ T cells, were crucial for removing distal tumors. Rechallenge/depletion experiments showed that the effector/memory phase required the presence of previously CD40/IL-2-activated CD4+ and CD8+ T cells to prevent recurrence. These novel findings show that different T cell effector mechanisms can operate for the eradication of local treated-site tumors versus untreated distal tumors and that signaling through CD40 generates a whole of body, effector/memory CD4+ and CD8+ T cell response that is amplified and prolonged via IL-2. Thus, successful immunotherapy needs to generate collaborating CD4+ and CD8+ T cells for a complete long-term protective cure.

Therapeutics Based on microRNA: A New Approach for Liver Cancer

Hepatocellular carcinoma (HCC) is a serious public health hazard. Polygenes involvement, accumulation of genetic and epigenetic changes and immune response of viral vector during gene therapy have resulted in the high mortality rate without marked change. To provide a safeguard for gene therapy and the feasibility for a clinical application, efforts have been focused predominantly upon constructing liver-targeted vector recently. MicroRNAs (miRNAs), a class of short endogenous RNAs, regulate the gene expression at the post-transcriptional level through imperfect base pairing with the 3′-untranslated region of target mRNAs. miRNAs, especially the liver-specific miRNA: miR-122, have multiple functions in liver development and abnormal expression of miRNAs could lead to liver diseases. Altered miRNA expressions have been observed in HCCs, viral hepatitis and hepatic fibrosis. The different expression profiles of miRNAs in HCC suggest that miRNAs may serve as either novel potential targets acting directly as oncogenes or therapeutic molecules working as tumor suppressor genes. Moreover, the abundance in general and liver specificity in particular, all together make them attractive to be considered as elements for hepatic specific targeting viral vector. This review describes recent progress in miRNA investigation on liver associated for better understanding the relationship between miRNA and liver cancer in order to raise prospects for therapy.

Physiological and tissue-specific vectors for treatment of inherited diseases

After more than 1500 gene therapy clinical trials in the past two decades, the overall conclusion is that for gene therapy (GT) to be successful, the vector systems must still be improved in terms of delivery, expression and safety. The recent development of more efficient and stable vector systems has created great expectations for the future of GT. Impressive results were obtained in three primary immunodeficiencies and other inherited diseases such as congenital blindness, adrenoleukodystrophy or junctional epidermolysis bullosa. However, the development of leukemia in five children included in the GT clinical trials for X-linked severe combined immunodeficiency and the silencing of the therapeutic gene in the chronic granulomatous disease clearly showed the importance of improving safety and efficiency. In this review, we focus on the main strategies available to achieve physiological or tissue-specific expression of therapeutic transgenes and discuss the importance of controlling transgene expression to improve safety. We propose that tissue-specific and/or physiological viral vectors offer the best balance between efficiency and safety and will be the tools of choice for future clinical trials in GT of inherited diseases.

Active adenoviral vascular penetration by targeted formation of heterocellular endothelial-epithelial syncytia

The endothelium imposes a structural barrier to the extravasation of systemically delivered oncolytic adenovirus (Ad). Here, we introduced a transendothelial route of delivery in order to increase tumor accumulation of virus particles (vp) beyond that resulting from convection-dependent extravasation alone. This was achieved by engineering an Ad encoding a syncytium-forming protein, gibbon ape leukemia virus (GALV) fusogenic membrane glycoprotein (FMG). The expression of GALV was regulated by a hybrid viral enhancer-human promoter construct comprising the human cytomegalovirus (CMV) immediate-early enhancer and the minimal human endothelial receptor tyrosine kinase promoter (“eTie1”). Endothelial cell-selectivity of the resulting Ad-eTie1-GALV vector was demonstrated by measuring GALV mRNA transcript levels. Furthermore, Ad-eTie1-GALV selectively induced fusion between infected endothelial cells and uninfected epithelial cells in vitro and in vivo, allowing transendothelial virus penetration. Heterofusion of infected endothelium to human embryonic kidney 293 (HEK 293) cells, in mixed in vitro cultures or in murine xenograft models, permitted fusion-dependent transactivation of the replication-deficient Ad-eTie1-GALV, due to enabled access to viral E1 proteins derived from the HEK 293 cytoplasm. These data provide evidence to support our proposed use of GALV to promote Ad penetration through tumor-associated vasculature, an approach that may substantially improve the efficiency of systemic delivery of oncolytic viruses to disseminated tumors.

Polyplex formation between four-arm poly(ethylene oxide)-b-poly(2-(diethylamino)ethyl methacrylate) and plasmid DNA in gene delivery

Amphiphilic polyelectrolytes comprising cationic and uncharged hydrophilic segments condensed negatively charged DNA to form a core-shell structure stabilized by a layer of hydrophilic corona chains. At physiological pH, four-arm star-shaped poly(ethylene oxide)-b-poly(2-(diethylamino)ethyl methacrylate) (four-arm PEO-b-PDEAEMA) block copolymer possessed positively charged amine groups that interacted with negatively charged plasmid DNA to form polymer/DNA complexes. The mechanism and physicochemical properties of the complex formation were investigated at varying molar ratio of amine groups on polymer chains and phosphate group on plasmid DNA segments (N/P ratio). The capability of the star block copolymer to condense DNA was demonstrated through gel electrophoresis and ethidium bromide exclusion assay. In the absence of salt, the hydrodynamic radius of polyplexes was about 94 nm at low polymer/DNA ratio, and it decreased to about 34 nm at large N/P ratios, forming a compact spherical structure with a weighted average molecular weight of 4.39 +/- 0.22 x 10(6) g/mol. Approximately 15 polymeric chains were required to condense a plasmid DNA. The addition of monovalent salt to the polyplexes significantly altered the size of the complexes, which would have an impact on cell transfection. Because of the electrostatic interaction induced by the diffusion of small ions, the polyplex increased in size to about 53 nm with a less compact structure. In vitro cytotoxicty of polymer and polymer/pDNA complexes were evaluated, and the polyplexes exhibited low toxicity at low N/P ratios. At N/P ratio of 4.5, the four-arm PEO-b-PDEAEMA showed the highest level of transfection in Neuro-2A cells. These observations showed that the star-shaped multi-arm polymers offers interesting properties in self-association and condensation ability for plasmid DNA and can serve as a nonviral DNA delivery system.

Development of a targeted siRNA delivery system using FOL-PEG-PEI conjugate

Receptor mediated delivery of siRNA enables silencing of target genes in specific tissues. Folate receptor (FR) is an attractive target for tumor-selective gene delivery. The focus of this study was to deliver the dihydrofolate reductase (DHFR) siRNA expressing plasmid and to silence the DHFR gene in FR positive KB cells, by complexing the plasmid with a folate-polyethylene glycol-polyethylenimine (FOL-PEG-PEI) conjugate, as a gene carrier. A DHFR siRNA sequence was cloned into a pSUPER-RNAi vector and complexed with the FOL-PEG-PEI conjugate. The complex was characterized by particle size analyzer, gel retardation and DNase protection assay. The FOL-PEG-PEI/pSUPER-siDHFR complex was transfected to FR overexpressing (KB) and FR negative (A549) cells. The transfection effiencies and gene inhibition were analyzed by fluorescence microscopy and RT-PCR. The pSUPER-siDHFR/PEI-PEG-FOL complex delivered the siRNA vector and inhibited DHFR gene in KB cells, while A549 cells were unaffected. Lipofectamine mediated transfection of pSUPER-siDHFR, delivered the vector and inhibited the DHFR gene in both KB and A549 cells. FR mediated delivery of siDHFR complexed with PEI-PEG-FOL conjugate inhibits the DHFR expression in FR positive cells alone. This strategy can be extended to deliver a wide range of drugs and post-transcriptional gene silencing therapeutics.

Enhancement of reporter gene detection sensitivity by insertion of specific mini-peptide-coding sequences

Two important aspects of gene therapy are to increase the level of gene expression and track the gene delivery site and expression, and a sensitive reporter gene may be one of the options for preclinical studies and possibly for human clinical trials. We report the novel concept of increasing the activity of the gene products. With the insertion of the mini-peptide-coding sequence CWDDWLC into the plasmid DNA of a SEAP reporter gene, we observed vast increases in the enzyme activity in vitro in all murine and human cell lines used. In addition, in vivo injection of this CWDDWLC-SEAP-encoding gene resulted in the same increases in reporter gene activity, but these increases did not correspond to alterations in the level of the gene products in the serum. Minor sequence changes in this mini-peptide negate the activity increase of the reporter gene. We report the novel concept of increasing the activity of gene products as another method to improve the reporting sensitivity of reporter genes. This improved reporter gene could complement any improved vector for maximizing the reporter sensitivity. Moreover, this strategy has the potential to be used to discover peptides that improve the activity of therapeutic genes.

The tissue plasminogen activator gene promoter: a novel tool for radiogenic gene therapy of the prostate?

BACKGROUND

Radiation therapy is a treatment modality routinely used in cancer management so it is not unexpected that radiation-inducible promoters have emerged as an attractive tool for controlled gene therapy. The human tissue plasminogen activator gene promoter (t-PA) has been proposed as a candidate for radiogenic gene therapy, but has not been exploited to date. The purpose of this study was to evaluate the potential of this promoter to drive the expression of a reporter gene, the green fluorescent protein (GFP), in response to radiation exposure.

METHODS

To investigate whether the promoter could be used for prostate cancer gene therapy, we initially transfected normal and malignant prostate cells. We then transfected HMEC-1 endothelial cells and ex vivo rat tail artery and monitored GFP levels using Western blotting following the delivery of single doses of ionizing radiation (2, 4, 6 Gy) to test whether the promoter could be used for vascular targeted gene therapy.

RESULTS

The t-PA promoter induced GFP expression up to 6-fold in all cell types tested in response to radiation doses within the clinical range.

CONCLUSIONS

These results suggest that the t-PA promoter may be incorporated into gene therapy strategies driving therapeutic transgenes in conjunction with radiation therapy.

MicroRNAs and the regulation of vector tropism

Despite being small (approximately 22 nt) microRNAs (miRNAs) profoundly influence tissue-specific gene expression by interacting with complementary target sequences in cellular messenger RNAs, impairing their translation or marking them for early destruction. Recent work has shown that tissue-specific miRNAs offer a versatile target that can be exploited to control the tropisms of gene expression vectors and of replication-competent viruses. The principle of incorporating miRNA targets into vector genomes to control their tropisms was first demonstrated for nonreplicating lentiviral and adenoviral vectors, with subsequent extension of these studies to replication-competent (oncolytic) picornaviruses, rhabdoviruses, and adenoviruses. In contrast to previous targeting approaches, miRNA targeting looks set to be applicable across the entire spectrum of viruses and gene expression vectors. Here we provide a critique of the literature relevant to this new and rapidly developing field of endeavor. We also examine the possibility of engineering viruses for expression of tropism-regulating miRNAs.

Tumor-microenvironment interactions: dangerous liaisons

The interaction between microenvironmental components and tumor cells is bidirectional. Tumor cells and their products are capable of regulating and altering gene expression in nontumor cells residing in or infiltrating into the microenvironment and exert selective pressures on such cells, thereby shaping their phenotype. Conversely, microenvironmental components regulate gene expression in tumor cells thereby directing the tumor into one or several possible molecular evolution pathways, some of which may lead to metastasis. This review summarizes six instances in which the tumor liaises with different components of its microenvironment. These liaisons result, in most cases, in enhanced tumor progression. In these cases (responses of tumor and nontumor cells to microenvironmental stress, the interaction of the tumor with fibroblasts, endothelial cells and macrophages, the formation of the metastatic niche, and the interaction of the tumor with immunoglobulins) the tumor, directly or indirectly, alters the phenotype of its interaction partners thereby enlisting them to promote its progression. Does the tumor need all these pathways to form metastasis? Is there a hierarchy of interactions with respect to impact on tumor progression? These questions remain open. They may be answered by approaches employed in the analysis of hypercomplex systems.

Novel challenges in exploring peptide ligands and corresponding tissue-specific endothelial receptors

The structural and molecular diversity of vascular endothelium may depend on the functional state and tissue localisation of its cells. Tumour vasculature expresses a number of molecular markers that distinguish it from normal vasculature. In cancer, the determinant of specific tumour vasculature heterogeneity is, in part, dictated by dysregulated expression of tumour-derived angiogenic factors. The identification of molecular 'addresses' on the surface of tumour vasculature has significantly contributed to the selection of targets, which have been used for delivering therapeutic and imaging agents in cancer. Cytotoxic drug, pro-apoptotic peptides, protease inhibitors, and gene therapy vectors have been successfully linked to peptides and delivered to tumour sites with an improved experimental therapy. Different diagnostic and therapeutic compounds can be efficiently targeted to specific receptors on vascular endothelial cells; the development of ligand-directed vector tools may promote systemic targeted gene delivery. Here, we review the very recent advances in the identification of peptide ligands and their corresponding tissue-specific endothelial receptors through the phage display technology with emphasis on ligand-directed delivery of therapeutic agents and targeted gene therapy.