5'-,3'-inverted thymidine-modified antisense oligodeoxynucleotide targeting midkine. Its design and application for cancer therapy

Nasopharynx Battlefield: Cellular Immune Responses Mediated by Midkine in Nasopharyngeal Carcinoma and COVID-19

Clinical evidence suggests that the severe respiratory illness coronavirus disease 2019 (COVID-19) is often associated with a cytokine storm that results in dysregulated immune responses. Prolonged COVID-19 positivity is thought to disproportionately affect cancer patients. With COVID-19 disrupting the delivery of cancer care, it is crucial to gain momentum and awareness of the mechanistic intersection between these two diseases. This review discusses the role of the cytokine midkine (MK) as an immunomodulator in patients with COVID-19 and nasopharyngeal carcinoma (NPC), both of which affect the nasal cavity. We conducted a review and analysis of immunocellular similarities and differences based on clinical studies, research articles, and published transcriptomic datasets. We specifically focused on ligand-receptor pairs that could be used to infer intercellular communication, as well as the current medications used for each disease, including NPC patients who have contracted COVID-19. Based on our findings, we recommend close monitoring of the MK axis to maintain the desirable effects of therapeutic regimens in fighting both NPC and COVID-19 infections.

Midkine (MDK) growth factor: a key player in cancer progression and a promising therapeutic target

Midkine is a heparin-binding growth factor, originally reported as the product of a retinoic acid-responsive gene during embryogenesis, but currently viewed as a multifaceted factor contributing to both normal tissue homeostasis and disease development. Midkine is abnormally expressed at high levels in various human malignancies and acts as a mediator for the acquisition of critical hallmarks of cancer, including cell growth, survival, metastasis, migration, and angiogenesis. Several studies have investigated the role of midkine as a cancer biomarker for the detection, prognosis, and management of cancer, as well as for monitoring the response to cancer treatment. Moreover, several efforts are also being made to elucidate its underlying mechanisms in therapeutic resistance and immunomodulation within the tumor microenvironment. We hereby summarize the current knowledge on midkine expression and function in cancer development and progression, and highlight its promising potential as a cancer biomarker and as a future therapeutic target in personalized cancer medicine.

In situ condensation of an anti-cancer drug into fibrin gel enabling effective inhibition of tumor cell growth

We show herein the highly effective inhibition of tumor cell growth using a gel consisting of a fibrin polymer formed with the in situ condensation of a camptothecin (CPT) derivative as an anti-cancer drug, which is efficiently conveyed with a carrier aptamer from a solution to the gel in a phenomenon, called selective oligonucleotide entrapment in fibrin polymers (SOEF).

DNA origami-based aptasensors

Traditional analytical techniques face many limitations such as time-consuming process, complicated sample preparation, high consumption of reagents and need for expensive equipment. So, it is important that simple, rapid and sensitive detection methods are introduced. Nucleic acids-based assays, particularly aptamers, have a great impact on modern life sciences for biological analysis and target detection. Aptamer-based biosensors with unique recognition properties including high specificity and affinity, rapid response and simple fabrication have attracted much attention. It is believed that two- and three-dimensional structures, sometimes referred to as DNA origami, using DNA aptamers can show more selective binding affinity and better stability over other nucleic acids forms. In this review, we will focus on recent advances in the development and uses of electrochemical and optical DNA origami-based aptasensors to supply readers with a comprehensive understanding of their improvements. Also, the challenges and awards of these approaches are discussed.

Specific Inhibition of Soluble γc Receptor Attenuates Collagen-Induced Arthritis by Modulating the Inflammatory T Cell Responses

IL-17 produced by Th17 cells has been implicated in the pathogenesis of rheumatoid arthritis (RA). It is important to prevent the differentiation of Th17 cells in RA. Homodimeric soluble γc (sγc) impairs IL-2 signaling and enhances Th17 differentiation. Thus, we aimed to block the functions of sγc by inhibiting the formation of homodimeric sγc. The homodimeric form of sγc was strikingly disturbed by sγc-binding DNA aptamer. Moreover, the aptamer effectively inhibited Th17 cell differentiation and restored IL-2 and IL-15 signaling impaired by sγc with evidences of increased survival of T cells. sγc was highly expressed in SF of RA patients and increased in established CIA mice. The therapeutic effect of PEG-aptamer was tested in CIA model and its treatment alleviated arthritis pathogenesis with impaired differentiation of pathogenic Th17, NKT1, and NKT17 cells in inflamed joint. Homodimeric sγc has pathogenic roles to exacerbate RA progression with differentiation of local Th17, NKT1, and NKT17 cells. Therefore, sγc is suggested as target of a therapeutic strategy for RA.

MicroRNAs Associated with Epithelial-Mesenchymal Transition Can Be Targeted to Inhibit Peritoneal Dissemination of Human Scirrhous Gastric Cancers

OBJECTIVES

Scirrhous gastric cancers grow rapidly, and frequently invade the peritoneum. Such peritoneal dissemination properties markedly reduce patient survival. Thus, an effective means for inhibiting peritoneal dissemination is urgently required.

METHODS

We previously established a cell line, HSC-58, from a scirrhous gastric cancer patient, and further successfully isolated a metastatic line, 58As9, in nude mice upon orthotopic inoculation. Using the lines, we examined the mechanism underlying peritoneal dissemination from the viewpoint of microRNA (miRNA) expression.

RESULTS

miRNA array and qRT-PCR analysis showed that the expressions of epithelial-mesenchymal transition (EMT)-associated miRNAs such as miR-200c and miR-141 were significantly low in 58As9. Using 58As9 with stably overexpressing miR-200c, miR-141, or both, together with a luciferase reporter assay, we found that miR-200c targeted zinc finger E-box-binding homeobox 1 (ZEB1) and miR-141 targeted ZEB2. The overexpressed lines reversed the EMT status from mesenchymal to epithelial in 58As9, and significantly reduced the invasion activity and peritoneal dissemination for a significant prolongation of survival in the orthotopic tumor models in nude mice.

CONCLUSIONS

EMT-associated miRNAs such as miR-200c and miR-141 and their target genes ZEB1/ZEB2 have good potential for antiperitoneal dissemination therapy in patients with scirrhous gastric cancers.

Aptamer-functionalized neural recording electrodes for the direct measurement of cocaine in vivo

Cocaine is a highly addictive psychostimulant that acts through competitive inhibition of the dopamine transporter. In order to fully understand the region specific neuropathology of cocaine abuse and addiction, it is unequivocally necessary to develop cocaine sensing technology capable of directly measuring real-time cocaine transient events local to different brain regions throughout the pharmacokinetic time course of exposure. We have developed an electrochemical aptamer-based in vivo cocaine sensor on a silicon based neural recording probe platform capable of directly measuring cocaine from discrete brain locations using square wave voltammetry (SWV). The sensitivity of the sensor for cocaine follows a modified exponential Langmuir model relationship and complete aptamer-target binding occurs in < 2 sec and unbinding in < 4 sec. The resulting temporal resolution is a 75X increase from traditional microdialysis sampling methods. When implanted in the rat dorsal striatum, the cocaine sensor exhibits stable SWV signal drift (modeled using a logarithmic exponential equation) and is capable of measuring real-time in vivo response to repeated local cocaine infusion as well as systemic IV cocaine injection. The in vivo sensor is capable of obtaining reproducible measurements over a period approaching 3 hours, after which signal amplitude significantly decreases likely due to tissue encapsulation. Finally, aptamer functionalized neural recording probes successfully detect spontaneous and evoked neural activity in the brain. This dual functionality makes the cocaine sensor a powerful tool capable of monitoring both biochemical and electrophysiological signals with high spatial and temporal resolution.

Pharmacokinetics of a Cholesterol-conjugated Aptamer Against the Hepatitis C Virus (HCV) NS5B Protein

Hepatitis C virus (HCV) is the major cause of progressive liver disease such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Previously, we reported that a 29 nucleotide-long 2'-F pyrimidine modified RNA aptamer against the HCV nonstructural protein 5B efficiently inhibited HCV replication and suppressed HCV infectious virus particle formation in a cell culture system. In this study, we modified this aptamer through conjugation of cholesterol for in vivo availability. This cholesterol-conjugated aptamer (chol-aptamer) efficiently entered the cell and inhibited HCV RNA replication, without any alteration in gene expression profiling including innate immune response-related genes. Moreover, systemic administration of the chol-aptamer was well tolerated without any abnormalities in mice. To evaluate the pharmacokinetics of the chol-aptamer in vivo, dose proportionality, bioavailability, and pharmacokinetic parameters were evaluated by noncompartmental analyses in normal BALB/c mice. Population analysis was performed using nonlinear mixed effects modeling. Moreover, the pharmacokinetics of two different routes (intravenous, IV, versus intraperitoneal, IP) were compared. Cholesterol conjugation showed dose proportionality, extended the time that the aptamer was in the plasma, and enhanced aptamer exposure to the body. Noticeably, the IV route was more suitable than the IP route due to the chol-aptamer remaining in the plasma for a longer period of time.

Quick chip assay using locked nucleic acid modified epithelial cell adhesion molecule and nucleolin aptamers for the capture of circulating tumor cells

The role of circulating tumor cells (CTCs) in disease diagnosis, prognosis, monitoring of the therapeutic efficacy, and clinical decision making is immense and has attracted tremendous focus in the last decade. We designed and fabricated simple, flat channel microfluidic devices polydimethylsiloxane (PDMS based) functionalized with locked nucleic acid (LNA) modified aptamers (targeting epithelial cell adhesion molecule (EpCAM) and nucleolin expression) for quick and efficient capture of CTCs and cancer cells. With optimized flow rates (10 μl/min), it was revealed that the aptamer modified devices offered reusability for up to six times while retaining optimal capture efficiency (>90%) and specificity. High capture sensitivity (92%) and specificity (100%) was observed in whole blood samples spiked with Caco-2 cells (10-100 cells/ml). Analysis of blood samples obtained from 25 head and neck cancer patients on the EpCAM LNA aptamer functionalized chip revealed that an average count of 5 ± 3 CTCs/ml of blood were captured from 22/25 samples (88%). EpCAM intracellular domain (EpICD) immunohistochemistry on 9 oral squamous cell carcinomas showed the EpICD positivity in the tumor cells, confirming the EpCAM expression in CTCs from head and neck cancers. These microfluidic devices also maintained viability for in vitro culture and characterization. Use of LNA modified aptamers provided added benefits in terms of cost effectiveness due to increased reusability and sustainability of the devices. Our results present a robust, quick, and efficient CTC capture platform with the use of simple PDMS based devices that are easy to fabricate at low cost and have an immense potential in cancer diagnosis, prognosis, and therapeutic planning.

Atelocollagen-mediated intravenous siRNA delivery specific to tumor tissues orthotopically xenografted in prostates of nude mice and its anticancer effects

Successful short interfering RNA (siRNA)-based therapy for cancers depends on functional siRNA delivery specific to tumors. In our previous report, we have shown systemic siRNA delivery specific to human prostate cancer cell line PC-3 subcutaneous tumors in nude mice by atelocollagen, a collagen derivative, for formulating a complex with siRNA. We used an siRNA for human Bcl-xL as a model target. In the present study, we examined the antitumor effect on PC-3 orthotopic tumors in nude mice, as these tumors resemble the human clinical situation. The systemic intravenous administration of the complex (siRNA, 50 μg/shot) significantly reduced Bcl-xL expression and induced apoptosis in the tumors, and suppressed their growth. Liver metastasis was also inhibited in the orthotopic model. We successfully showed tumor-specific accumulation of the siRNA by Cy3-labeled siRNA and the direct quantification of the siRNA via reverse-phase high-performance liquid chromatography. The tumor-specific delivery was achieved by the enhanced permeability and retention effect, which is characteristic of macromolecular drugs. The high expression of vascular endothelial growth factor-A in the tumors provided adequate conditions to promote the permeability in the tumors, and to finally form the enhanced permeability and retention effect. In conclusion, our siRNA delivery is specific to the PC-3 orthotopic tumors in nude mice, and is practically feasible to treat tumors.

Involvement of midkine in neuroblastoma tumourigenesis

Midkine is highly expressed in various cancers, including neuroblastoma, one of the most malignant paediatric solid tumours known. Also, it has been shown to be useful as a tumour marker, a prognosis factor and a target of molecular therapy. Several molecular tools (e.g. siRNA, antibodies and RNA aptamer) have been used to establish a midkine-targeted therapy. The involvement of midkine in tumourigenesis has been demonstrated in vivo in a mouse neuroblastoma model, where targeting it with an RNA aptamer was shown to be an effective treatment for xenografted tumours. Chemoresistance is one of the notable phenotypes regulated by midkine in various cancer cell types. In pancreatic tumours and glioma cells, midkine is expressed in chemoresistant cells and is involved in the survival of these cells in the presence of anticancer drugs. In contrast to these tumours, midkine was found to be expressed in every neuroblastoma cell line tested and the knockdown of midkine alone was sufficient to suppress their growth. These results indicate that neuroblastoma cells are highly dependent on midkine and that a midkine-targeted therapy could exert a significant effect in these cells. However, to achieve a midkine-targeted therapy for high-risk neuroblastoma patients, the further refinement of the RNA aptamer or antibody as tools and the elucidation of midkine signalling are immediate issues that need to be resolved. Regarding the latter, although it has been shown that Notch2 functions as a receptor in neuroblastoma cells, it is likely that other receptors (e.g. anaplastic lymphoma kinase) are also involved in midkine signalling.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

Electroporation-mediated siRNA delivery into tumors

Electroporation-mediated gene transfer (electro-transfection) is a powerful tool to introduce nucleic acid compounds such as plasmid DNAs, antisense oligonucleotides, and short interfering RNAs (siRNAs) into the cells. Electro-transfection is a physical gene transfer method that utilizes an electrostatic field generated with an electroporator apparatus. Here, we demonstrate a practical protocol for electro-transfection (electro-delivery) of siRNA into cells in vivo and further demonstrate the application of the method to cancer therapy. We successfully developed an original electrode (the plate and fork-type electrode) and used it for in vivo electro-delivery of siRNA. Vascular endothelial growth factor (VEGF), an angiogenic factor, was chosen as a model target gene. Electro-delivery of an siRNA targeting VEGF into the xenografted tumors in nude mice significantly suppressed the growth of tumors. By repeating the therapy with a chemically modified siRNA after an interval of 20 days, satisfactory anticancer effects were achieved.

Inhibition of the growth factor MDK/midkine by a novel small molecule compound to treat non-small cell lung cancer

Midkine (MDK) is a heparin-binding growth factor that is highly expressed in many malignant tumors, including lung cancers. MDK activates the PI3K pathway and induces anti-apoptotic activity, in turn enhancing the survival of tumors. Therefore, the inhibition of MDK is considered a potential strategy for cancer therapy. In the present study, we demonstrate a novel small molecule compound (iMDK) that targets MDK. iMDK inhibited the cell growth of MDK-positive H441 lung adenocarcinoma cells that harbor an oncogenic KRAS mutation and H520 squamous cell lung cancer cells, both of which are types of untreatable lung cancer. However, iMDK did not reduce the cell viability of MDK-negative A549 lung adenocarcinoma cells or normal human lung fibroblast (NHLF) cells indicating its specificity. iMDK suppressed the endogenous expression of MDK but not that of other growth factors such as PTN or VEGF. iMDK suppressed the growth of H441 cells by inhibiting the PI3K pathway and inducing apoptosis. Systemic administration of iMDK significantly inhibited tumor growth in a xenograft mouse model in vivo. Inhibition of MDK with iMDK provides a potential therapeutic approach for the treatment of lung cancers that are driven by MDK.

Midkine promotes neuroblastoma through Notch2 signaling

Midkine is a heparin-binding growth factor highly expressed in various cancers, including neuroblastoma, the most common extracranial pediatric solid tumor. Prognosis of patients with neuroblastoma in which MYCN is amplified remains particularly poor. In this study, we used a MYCN transgenic model for neuroblastoma in which midkine is highly expressed in precancerous lesions of sympathetic ganglia. Genetic ablation of midkine in this model delayed tumor formation and reduced tumor incidence. Furthermore, an RNA aptamer that specifically bound midkine suppressed the growth of neuroblastoma cells in vitro and in vivo in tumor xenografts. In precancerous lesions, midkine-deficient MYCN transgenic mice exhibited defects in activation of Notch2, a candidate midkine receptor, and expression of the Notch target gene HES1. Similarly, RNA aptamer-treated tumor xenografts also showed attenuation of Notch2-HES1 signaling. Our findings establish a critical role for the midkine-Notch2 signaling axis in neuroblastoma tumorigenesis, which implicates new strategies to treat neuroblastoma.

In vitro selection of proteins via emulsion compartments

In vitro compartmentalization (IVC) is a method to generate numerous, small, aqueous compartments (up to 10(10) compartments per ml) by mixing water, surfactants, and oil. The water phase is surrounded by surfactants and an oil phase, and to a first approximation each water-in-oil compartment is like an artificial cell. By introducing single genes into compartments that are competent for transcription and translation, these cell-like compartments can synthesize RNA protein variants in libraries. Screening or selecting for function has in turn led to schemes for the directed evolution of biomolecules. However, IVC selections can cover larger library sizes, and provide greater control over selection conditions and stringencies. The key issue in designing and executing IVC selections is how to couple genotype and phenotype, and in this review we have organized and presented a variety of mechanisms by which proteins and RNA can attach to or amplify their own templates following emulsification and selection.

Palmitic acid-conjugated 21-nucleotide siRNA enhances gene-silencing activity

Short interfering RNA (siRNA) technology is a powerful tool for suppressing gene expression in mammalian cells. In this study, we focused on the development of siRNAs conjugated with palmitic acid at the 5'-end of the sense strand (C16-siRNAs) using our novel synthesis strategy in order to improve the potency of siRNA. The C16-siRNAs exhibited enhanced nuclease stability. In addition, they showed potent gene-silencing efficacy against exogenous Renilla luciferase in HeLa cells compared with a nonmodified siRNA in the presence of Lipofectamine 2000. The C16-siRNAs also had a more potent inhibitory effect on Renilla luciferase activity than the other siRNA conjugated with lipids at the 5'-end and the 3'-end by palmitoyl conjugation. For further improvement, the gene silencing potency of the C16-siRNAs against the endogenous vascular endothelial growth factor (VEGF) gene in HeLa cells was investigated. In this investigation, the siRNAs were prepared not only with the normal RNA sequence but also coupled with an inverted thymidine (idT) at the 3'-ends of both the sense and antisense strands (siRNA-idT), including palmitic acid conjugations at the 5'-end of the sense strand, to improve stability. The C16-siRNA including idT modifications exhibited a significantly greater inhibitory effect on the VEGF gene in the presence of Lipofectamine 2000. It is noteworthy that C16-siRNA-idT demonstrated long-term gene-silencing efficacy of up to 5 days. Interestingly, the C16-siRNAs, including that with idT modifications, exhibited strong RNAi potency in the absence of any transfection reagents, although only at high concentrations. Both the C16-siRNAs and C16-siRNA-idT induced a high level of membrane permeability in HeLa cells. Our developed C16-siRNAs, particularly C16-siRNA-idT, are thus among the promising candidates for a new generation of modified siRNAs that can solve the many problems associated with siRNA technology.

The metastasis-associated microRNA miR-516a-3p is a novel therapeutic target for inhibiting peritoneal dissemination of human scirrhous gastric cancer

Although aberrant microRNA (miRNA) is expressed in different types of human cancer tissues, its pathophysiologic role and the relevance of tumorigenesis and metastasis are still largely unknown. Here, we defined miRNAs involved in cancer metastasis (metastamirs) using an established mouse model for peritoneal dissemination of human scirrhous gastric carcinoma cells. Highly metastatic derivatives (44As3 cells) were derived from the parental cells originally isolated from patients (HSC-44PE cells). Using microarray analysis to identify differentially expressed miRNAs in 44As3 and HSC-44PE cells, we focused on miR-516a-3p as a candidate antimetastatic miRNA (antimetastamir) whose functions in cancer had not been studied. We confirmed attenuated expression of miR-516a-3p in 44As3 cells compared with HSC-44PE cells by Northern blot analysis and quantitative reverse transcriptase PCR. Stable ectopic overexpression in 44As3-miR-516a-3p cells permitted identification of sulfatase 1 as a direct target of the miRNA, through use of the isobaric tagging reagent iTRAQ and the QSTAR Elite Hybrid LC-MS/MS system. Sulfatase 1 is known to remove 6-O-sulfates from heparan sulfate proteoglycans on the cell surface, causing release of membrane-bound Wnt ligands from cells. Consistent with this function, Western blot analyses revealed high levels of Wnt3a, Wnt5a, and nuclear β-catenin accumulation in 44As3 cells but relatively reduced levels in 44As3-miR-516a-3p cells. Notably, orthotopic inoculation of nude mice with 44As3-miR-516a-3p cells yielded significantly longer survival periods compared with mice inoculated with control 44As3 cells. Through atelocollagen-mediated delivery of an miR-516a-3p expression vector into orthotopic 44As3 tumors, we documented its feasibility as a treatment agent. Our findings define the miRNA miR-516-3p as an antimetastamir with potential therapeutic applications in blocking metastatic dissemination of gastric cancers.

Molecular engineering and validation of an oncolytic herpes simplex virus type 1 transcriptionally targeted to midkine-positive tumors

BACKGROUND

Expression profile analyses of midkine (MDK), a multifunctional protein important in development but repressed postnataly, indicate that it is highly expressed in approximately 80% of adult carcinomas and many childhood cancers including malignant peripheral nerve sheath tumors (MPNST). In the present study, we sought to leverage its selective expression to develop a novel oncolytic herpes simplex virus (oHSV) capable of targeting developmentally primitive cancers that express MDK.

METHODS

We sought to increase the oncolytic efficacy of the virus by fusing the human MDK promoter to the HSV type 1 neurovirulence gene, gamma(1)34.5, whose protein product increases viral replication.

RESULTS

Tissue-specific MDK promoter activity in human tumor cells and transgene biological activity was confirmed in human MPNST tumor cells. In vitro replication and cytotoxicity in human fibroblasts and MPNST cells by plaque and MTT assays showed that oHSV-MDK-34.5 increased replication and cytotoxicity compared to oHSV-MDK-Luc. By contrast, no significant difference in cytotoxicity was detected between these viruses in normal human fibroblasts. oHSV-MDK-34.5 impaired in vivo tumor growth and increased median survival of MPNST tumor-bearing nude mice.

CONCLUSIONS

The transcriptional targeting of HSV lytic infection to MDK-expressing tumor cells is feasible. oHSV-MDK-34.5 shows enhanced anti-tumor effects both in vitro and in vivo. Further studies are warranted and may lead to its use in clinical trials.

Systemic delivery of siRNA specific to tumor mediated by atelocollagen: combined therapy using siRNA targeting Bcl-xL and cisplatin against prostate cancer

The largest obstacle to the effective use of short interfering RNA (siRNA) in an animal body is the ability to deliver it to the target tissue. Here we showed a systemic delivery method of siRNA specific to pregrown solid tumors via atelocollagen. Atelocollagen facilitated the selective uptake of siRNA into the tumors when an siRNA/atelocollagen complex was administered intravenously to mice. We chose a Bcl-xL protein as a model target to prove the therapeutic efficacy of the atelocollagen-mediated method. Bcl-xL acts as an anti-apoptotic factor, which is overexpressed in many cancers, including prostate cancer. One of the four designed siRNAs to human Bcl-xL potently inhibited the expression of Bcl-xL by the PC-3 human prostate cancer cell line in vitro, leading to cell apoptosis. Intravenous injections for3 consecutive days (siRNA, 100 microg/injection per day as a complex with atelocollagen) effectively downregulated Bcl-xL expression in the PC-3 xenograft. We administered four series of 3 consecutive days of intravenous injections each, for a total of 12 injections, which significantly inhibited tumor growth when the treatment was combined with cisplatin (2 mg/kg). Local injection of Bcl-xL siRNA also potently inhibited tumor growth. All of the tumors treated with Bcl-xL siRNA/atelocollagen complex via both intravenous and intratumoral injection showed terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive apoptosis. There were no severe side effects such as interferon-alpha induction and liver or renal damage in mice. Our results indicate that systemic delivery of siRNA via atelocollagen, which specifically targets tumors, is safe and feasible for cancer therapy.

Local and systemic delivery of siRNAs for oligonucleotide therapy

RNA interference (RNAi) is a relatively new found phenomenon of posttranscriptional gene silencing to regulate the expression of multiple genes involved in a wide range of biological processes. The gene-silencing technology via RNAi has also been developed into a commonly anti-gene method. Furthermore, in vivo data indicate that small interfering RNAs (siRNAs) may be used to treat human diseases. However, the most challenging issue to a successful in vivo application is the development of a delivery system that can transport siRNA molecules into the tissues and/or the cells of interest. Also, the evaluation of siRNA potency in vivo is central for the selection of therapeutic siRNAs. In this chapter, the effects of atelocollagen-delivered siRNAs in live animals were monitored using bioluminescence imaging.

Plasma midkine level is a prognostic factor for human neuroblastoma

Neuroblastoma is the third-most-common solid tumor of childhood. To date, no reliable blood marker for neuroblastoma has been established. The growth factor midkine is highly expressed in human carcinomas and its knockdown leads to tumor growth suppression in animal models. The present study evaluated the plasma midkine level in human neuroblastoma patients. Plasma samples were obtained from patients found through mass screening, as well as from sporadic neuroblastoma patients. The total number of cases examined was 756. Among them, prognostic information was available for 175 sporadic cases and 287 mass-screening cases. Midkine levels were significantly higher in neuroblastoma patients, including both mass-screening cases and sporadic cases, than in non-tumor controls (P < 0.0001). The midkine level was significantly correlated with the statuses of MYCN amplification, TRKA expression, ploidy, stage and age (P < 0.0001, < 0.0001, = 0.004, < 0.0001 and < 0.0001, respectively), which are known prognostic factors for neuroblastoma. There was a striking correlation between high plasma midkine level and poor prognosis (P < 0.0001). Within sporadic cases, the midkine level was also strikingly higher than in non-tumor controls (P < 0.0001), and correlated with the statuses of MYCN amplification and stage (P = 0.0005 and = 0.003, respectively). There was a significant correlation between high plasma midkine level and poor prognosis (P = 0.04). Taken together, the present data indicate that plasma midkine level is a prognostic factor for human neuroblastoma.

In vivo silencing of a molecular target by short interfering RNA electroporation: tumor vascularization correlates to delivery efficiency

Screening for a molecular target for cancer therapy requires multiple steps, of which an important one is evaluation of the knockdown effect of the target molecule on pregrown xenograft tumors. However, methods currently used for local administration of knockdown reagents, such as short interfering RNA (siRNA), are not satisfactory as to simplicity and efficiency. We established an electroporation method involving a constant voltage and "plate and fork" type electrodes and used it for in vivo delivery of siRNA. The delivery efficiency correlated to the electric current. The electric current correlated to the microvascular density and vascular endothelial growth factor (VEGF) expression and exhibited a threshold that guaranteed efficient delivery. Consequently, we showed that the vascularization and VEGF expression in tumors determined the efficiency of delivery of siRNA by electroporation. VEGF was chosen as a model target. VEGF siRNA electroporation suppressed the growth of tumors exhibiting high VEGF expression to less than 10% of the control level, but it had no effect on low VEGF-expressing tumors. Notably, a long interval (20 days) of electroporation was enough to obtain a satisfactory effect. Systemically injected siRNA could also be delivered into tumors by this method. Our data will provide the technical basis for in vivo electroporation, and this simple and efficient siRNA delivery method is applicable to in vivo comprehensive screening for a molecular target.

Midkine and LDL-receptor-related protein 1 contribute to the anchorage-independent cell growth of cancer cells

The growth factor midkine (MK) is highly associated with cancer progression. Knockdown of MK expression strikingly suppresses tumor growth in nude mice. Thus, MK is a candidate target for cancer treatment. LDL-receptor-related protein 1 (LRP1) is a receptor for MK. We found that among the four ligand-binding domains of LRP1, the N-terminal half of the second domain (designated as MK-TRAP) had the strongest affinity to MK. MK-TRAP bound to MK, but not to HB-GAM/pleiotrophin, basic fibroblast growth factor or platelet-derived growth factor (PDGF)-BB. Exogenous MK-TRAP inhibited the binding between MK and LRP1. G401 cells that transiently or stably overexpress MK-TRAP showed decreased cell growth in monolayer culture and reduced colony formation in soft agar, which could be rescued by exogenous MK administration. MK-TRAP collected from conditioned medium also inhibited anchorage-independent growth of G401 cells and CMT-93 cells. Anti-MK antibody also inhibited the anchorage-independent growth. CMT-93 cells stably expressing MK-TRAP formed smaller tumors in a xenograft nude mouse model than control cells. Moreover, GST-RAP, a potent inhibitor of LRP1, inhibited the anchorage-independent growth of control G401 cells but not that of MK-TRAP stable transformants. Collectively, these data demonstrate a crucial role of MK-LRP1 signaling in anchorage-independent cell growth.

Brothers in arms: DNA enzymes, short interfering RNA, and the emerging wave of small-molecule nucleic acid-based gene-silencing strategies

The past decade has seen the rapid evolution of small-molecule gene-silencing strategies, driven largely by enhanced understanding of gene function in the pathogenesis of disease. Over this time, many genes have been targeted by specifically engineered agents from different classes of nucleic acid-based drugs in experimental models of disease to probe, dissect, and characterize further the complex processes that underpin molecular signaling. Arising from this, a number of molecules have been examined in the setting of clinical trials, and several have recently made the successful transition from the bench to the clinic, heralding an exciting era of gene-specific treatments. This is particularly important because clear inadequacies in present therapies account for significant morbidity, mortality, and cost. The broad umbrella of gene-silencing therapeutics encompasses a range of agents that include DNA enzymes, short interfering RNA, antisense oligonucleotides, decoys, ribozymes, and aptamers. This review tracks current movements in these technologies, focusing mainly on DNA enzymes and short interfering RNA, because these are poised to play an integral role in antigene therapies in the future.

Short RNA guides cleavage by eukaryotic RNase III

In eukaryotes, short RNAs guide a variety of enzymatic activities that range from RNA editing to translation repression. It is hypothesized that pre-existing proteins evolved to bind and use guide RNA during evolution. However, the capacity of modern proteins to adopt new RNA guides has never been demonstrated. Here we show that Rnt1p, the yeast orthologue of the bacterial dsRNA-specific RNase III, can bind short RNA transcripts and use them as guides for sequence-specific cleavage. Target cleavage occurred at a constant distance from the Rnt1p binding site, leaving the guide RNA intact for subsequent cleavage. Our results indicate that RNase III may trigger sequence-specific RNA degradation independent of the RNAi machinery, and they open the road for a new generation of precise RNA silencing tools that do not trigger a dsRNA-mediated immune response.

Atelocollagen-mediated systemic DDS for nucleic acid medicines

The goal of our research is to provide a practical platform for drug delivery in oligonucleotide therapy. We report here the efficacy of an atelocollagen-mediated oligonucleotide delivery system applied to systemic siRNA and antisense oligonucleotide treatments in animal disease models. Atelocollagen and oligonucleotides formed a complex of nanosized particles, which was highly stable against nucleases. The complex allowed oligonucleotides to be delivered efficiently into several organs and tissues via intravenous administration. In a tumor metastasis model, the complex successfully delivered siRNA to metastasized tumors in bone tissue and inhibited their growth. We also demonstrated that a single intravenous treatment of the antisense oligodeoxynucleotide complex suppressed ear dermatitis in a contact hypersensitivity model. These results indicate the strong potential of the atelocollagen-mediated drug delivery system for practical therapeutic technology.

Combinational antitumor effect of siRNA against midkine and paclitaxel on growth of human prostate cancer xenografts

BACKGROUND

Midkine (MK) is a heparin-binding growth factor that promotes the growth, migration, and survival of various cells. Its overexpression has been observed in many human malignancies, making it an attractive therapeutic target.

METHODS

We established a human midkine blockade system involving RNA interference.

RESULTS

The synthetic small interfering RNA (siRNA) targeting human midkine almost completely inhibited the secretion of midkine by a human prostate cancer cell line, PC-3, and consequently suppressed the proliferation and anchorage-independent growth of the transfected cells. The midkine siRNA, together with atelocollagen, significantly suppressed the growth of PC-3 tumors, which had been subcutaneously xenografted. These inhibitory effects of midkine siRNA were augmented by combinational treatment with a chemotherapeutic, paclitaxel (PTX), both in vitro and in vivo. The dose of PTX (12 mg/kg) used for the combinational treatment did not cause leukopenia or liver damage, which are often reported as serious adverse effects of PTX. The effect of the combination on tumor growth was comparable with that of PTX alone at higher doses that have exhibited severe adverse effects. Midkine siRNA suppressed mainly cell proliferation and slightly angiogenesis, whereas PTX enhanced apoptosis and slightly suppressed angiogenesis. The combination treatment was particularly effective for suppression of angiogenesis; consequently, it had striking effects on all aspects (proliferation, apoptosis, and angiogenesis).

CONCLUSIONS

We established a novel and safe cancer therapy strategy involving midkine siRNA combined with PTX, with less adverse effects.

Midkine, a heparin-binding growth factor, produced by the host enhances metastasis of Lewis lung carcinoma cells

Midkine is a heparin-binding growth factor and is expressed by a number of tumor cells, contributing to their growth both in vitro and in vivo. Spontaneous lung metastasis of Lewis lung carcinoma cells, which did not significantly express MK, was significantly less extensive in mice deficient in the midkine gene than in wild-type mice, when the tumor was subcutaneously grown above the thigh. Midkine strongly enhanced migration of Lewis lung carcinoma cells in vitro. Therefore, midkine is also a host factor enhancing tumor metastasis. Anti-midkine therapy for malignancy may act on midkine produced by both the tumor and host.

Regulation of MDK expression in human cancer cells modulates sensitivities to various anticancer drugs: MDK overexpression confers to a multi-drug resistance

MDK is a heparin-binding growth factor associated with cancer development. Here, we sought to examine the association of MDK expression with resistance and sensitivity to different chemotherapeutic agents. We established stable HeLa cell transfectants (HeLa-MDK) and tested for decreased sensitivity to chemotherapeutic agents (5-FU, doxorubicin, and cisplatin). In addition, we used siRNA to block MDK expression in SNU-638 human gastric cancer cells and examined the chemosensitizing effect. HeLa-MDK cells treated with 5-FU, doxorubicin, and cisplatin showed a fold increase in the average IC(50) and an increased cell survival. siRNA-based knockdown of MDK expression in SNU-638 cells decreased the average IC(50) by 18-44% in cells treated with three drugs. Further investigations on the molecular mechanism should be clarified, but these results indicate that MDK up- and down-regulation appears to be capable of changing the chemosensitivities of cancer cells and MDK may have possible importance as a candidate therapeutic molecule.

Midkine antisense oligodeoxyribonucleotide inhibits renal damage induced by ischemic reperfusion

BACKGROUND

Midkine, a heparin-binding growth factor, is involved in the migration of inflammatory cells. The inflammatory cell migration to the tubulointerstitium of the kidney after ischemia/reperfusion (I/R) injury is attenuated in midkine gene-deficient mice, resulting in better preservation of the tubulointerstitium compared with wild-type mice. In the present investigation, we planned to evaluate the usefulness of antisense midkine for the therapy of ischemic renal failure.

METHODS

Midkine antisense phosphorothioate oligodeoxyribonucleotide (ODN) at a dose of 1 mg/kg in saline was intravenously administered to mice 1 day before or after I/R. The kidneys were removed for examination 1, 2, 3, and 7 days after I/R.

RESULTS

It was rapidly incorporated into proximal tubular epithelial cells, and inhibited midkine synthesis, leading to reduced migration of inflammatory cells to the injured epithelial layer. Consequently, the midkine antisense ODN-treated animals exhibited less severe renal damage than untreated or midkine sense ODN-treated animals 2 days after I/R as assessed by morphologic criteria and blood urea nitrogen (BUN) and serum creatinine levels. Midkine expression, BUN, and serum creatinine levels were not significantly different between injection of midkine antisense ODN before and after ischemic injury.

CONCLUSION

These results indicate that intravenous injection of midkine antisense ODN is a candidate for a novel therapeutic strategy against acute tubulointerstitial injury induced by I/R injury.

Postischemic gene transfer of midkine, a neurotrophic factor, protects against focal brain ischemia

Gene therapy may be a promising approach for treatment of brain ischemia. In this study, we examined the effect of postischemic gene transfer of midkine, a heparin-binding neurotrophic factor, using a focal brain ischemia model with the photothrombotic occlusion method. At 90 min after induction of brain ischemia in spontaneously hypertensive rats, a replication-deficient recombinant adenovirus encoding mouse midkine (AdMK, n=7) or a control vector encoding beta-galactosidase (Adbetagal, n=7) was injected into the lateral ventricle ipsilateral to ischemia. At 2 days after ischemia, we determined infarct volume by 2,3,5-triphenyltetrazolium chloride staining. There were no significant differences in cerebral blood flow 1 h after ischemia between AdMK and Adbetagal groups. Infarct volume of AdMK group was 51+/-27 mm3, which was significantly smaller than that of Adbetagal group (86+/-27 mm3, P<0.05). TUNEL-positive and cleaved caspase-3-positive cells in the periischemic area of AdMK-treated rats were significantly fewer than those in Adbetagal-treated rats, suggesting that the reduction of infarct volume by midkine was partly mediated by its antiapoptotic action. Thus, gene transfer of midkine to the ischemic brain may be effective in the treatment of brain ischemia.

Morpholino antisense oligomer targeting human midkine: its application for cancer therapy

Overexpression of a heparin-binding growth factor, midkine (MK), has been observed in many malignancies, making it an attractive therapeutic target. We used morpholino antisense oligomers to downregulate human MK expression in human prostate (PC-3) and colon carcinoma (SW620) cells, and determined the practical advantages of this anticancer therapeutic. Morpholino antisense oligomers directed against MK caused a dramatic and sequence-specific decrease of the target protein level, resulting in the inhibition of growth and anchorage-independent growth of the transfected cells. Furthermore, MK morpholino antisense oligomers exhibited a significant anticancer effect in the PC-3- and SW620-xenograft models. In comparison with phosphorothioate-modified oligodeoxynucleotide, morpholino oligomers showed 2 major advantages, stability and non-toxicity. MALDI-TOF mass spectrometric analysis showed that morpholino antisense oligomers were completely stable in the presence of serum nuclease(s). Serological examinations demonstrated no toxicity of MK morpholino antisense oligomers. Our study indicates that inhibition of MK expression by morpholino antisense oligomer is a promising novel and safe therapeutic strategy for cancers.

Potential of atelocollagen-mediated systemic antisense therapeutics for inflammatory disease

To study the possibility of using atelocollagen as an oligonucleotide (ODN) delivery carrier in vivo, the activity of formulated antisense ODN targeted against the intercellular adhesion molecule-1 (ICAM-1) mRNA was investigated in an allergic dermatitis model in mice. The allergic dermatitis was elicited in one ear of animals sensitized by treatment with 2,4-dinitrofluorobenzene. Antisense ODN was given to the animals as a single intravenous injection of formulation containing atelocollagen. Antisense activity was determined by measurement of ear thickness, histopathology, and immunohistochemistry 24 hr after the initiation of the dermatitis. Antisense activity was found to increase according to the concentration of atelocollagen in the formulation. The effect mediated by the ODN formulated with 0.05% atelocollagen was more than 50 times greater than that provided by ODN infusion, although the levels of ODN formulated with atelocollagen dropped below that of the 24-hr infusion group within 30 min. The formulated ODN could suppress inflammatory progression by treatment at 8 hr after the ear challenge when inflammation had already commenced at the challenged site. Moreover, antisense activity was noted even when the formulated ODN was injected 3 days before the initiation of inflammation. These data demonstrate that atelocollagen can enhance antisense activity remarkably and that the sustainable antisense activity mediated by the formulation of ODN with atelocollagen could completely change the strategy of antisense therapeutics.

Identification of genes with differential expression in acquired drug-resistant gastric cancer cells using high-density oligonucleotide microarrays

PURPOSE

A major obstacle in chemotherapy is treatment failure due to anticancer drug resistance. The emergence of acquired resistance results from host factors and genetic or epigenetic changes in the cancer cells. The purpose of this study was to identify differentially expressed genes associated with acquisition of resistance in human gastric cancer cells.

EXPERIMENTAL DESIGN

We performed global gene expression analysis in the acquired drug-resistant gastric cancer cell lines to the commonly used drugs 5-fluorouracil, doxorubicin, and cisplatin using Affymetrix HG-U133A microarray. The gene expression patterns of 10 chemoresistant gastric cancer cell lines were compared with those of four parent cell lines using fold-change and Wilcoxon's test for data analysis.

RESULTS

We identified over 250 genes differentially expressed in 5-fluorouracil-, cisplatin-, or doxorubicin-resistant gastric cancer cell lines. Our expression analysis also identified eight multidrug resistance candidate genes that were associated with resistance to two or more of the tested chemotherapeutic agents. Among these, midkine (MDK), a heparin-binding growth factor, was overexpressed in all drug-resistant cell lines, strongly suggesting that MDK might contribute to multidrug resistance in gastric cancer cells.

CONCLUSIONS

Our investigation provides comprehensive gene information associated with acquired resistance to anticancer drugs in gastric cancer cells and a basis for additional functional studies.

A small interfering RNA targeting vascular endothelial growth factor as cancer therapeutics

Vascular endothelial growth factor (VEGF) plays a critical role during normal embryonic angiogenesis and also in the pathological angiogenesis that occurs in a number of diseases, including cancer. We developed a novel VEGF blockade system using RNA interference. The small interfering RNA (siRNA) targeting human VEGF almost completely inhibited the secretion of VEGF in a human prostate cancer cell line, PC-3, whereas the control scramble siRNA showed no effects. The VEGF siRNA with atelocollagen dramatically suppressed tumor angiogenesis and tumor growth in a PC-3 s.c. xenograft model. Atelocollagen provided a beneficial delivering means by which stabilization and efficient transfection of the siRNA injected into the tumors were achieved.

Midkine and pleiotrophin in neural development and cancer

The midkine (MK) family consists of only two members, namely heparin-binding growth factors MK and pleiotrophin (PTN). During embryogenesis, MK is highly expressed in the mid-gestational period, whereas PTN expression reaches the maximum level around birth. Both proteins are localized in the radial glial processes of the embryonic brain, along which neural stem cells migrate and differentiate. Zebrafish and Xenopus MK can induce neural tissues. In addition, deposits of MK and/or PTN are found in neurodegenerative diseases, such as Alzheimer's disease and multiple system atrophy. Both molecules are induced in reactive astrocytes by ischemic insults. In this context, it is interesting that LDL receptor-related protein is a receptor for MK and PTN, and this receptor has been implicated in the pathogenesis of Alzheimer's disease. MK and PTN share receptors, and show similar biological activities that include fibrinolytic, anti-apoptotic, mitogenic, transforming, angiogenic, and chemotactic ones. These activities explain how these molecules are involved in carcinogenesis. MK is detected in human carcinoma specimens from pre-cancerous stages to advanced stages. Strong expression of PTN is also detected in several carcinomas, although, in general, MK is expressed more intensely and in a wide range of carcinomas than PTN. The blood MK level is frequently elevated in advanced human carcinomas, decreases after surgical removal of the tumors, and is correlated with prognostic factors. Thus, it is a good market for evaluating the progress of carcinomas. Furthermore, antisense oligonucleotides for MK and ribozymes for PTN show anti-tumor activity. Therefore, MK and PTN are candidate molecular targets for therapy for human carcinomas.

Correlation of elevated level of blood midkine with poor prognostic factors of human neuroblastomas

The heparin-binding growth factor midkine (MK) is the product of a retinoic acid-responsive gene, and is implicated in neuronal survival and differentiation, and carcinogenesis. We previously reported that MK mRNA expression is elevated in neuroblastoma specimens at all stages, whereas pleiotrophin, the other member of the MK family, is expressed at high levels in favourable neuroblastomas. As MK is a secretory protein, it can be detected in the blood. Here, we show a significant correlation of the plasma MK level with prognostic factors of neuroblastomas. The plasma MK level was determined in 220 patients with neuroblastomas, and compared with that in children without malignant tumors (n=17, <500 pg ml(-1)). The plasma MK level became significantly elevated with advancing stages (stage 1: 445 pg ml(-1) (median), n=73; stage 2: 589, n=39; stage 3: 864, n=40; stage 4: 1445, n=56; and stage 4S: 2439, n=12). More importantly, a higher MK level was strongly correlated with poor prognostic factors: over 1 year of age (P=0.0299), MYCN amplification (P<0.0001), low TrkA expression (P=0.0005), nonmass screening, sporadic neuroblastomas (P<0.0001), and diploidy/tetraploidy (P=0.0007). Thus, these results demonstrate that the plasma MK level is a good marker for evaluating the progression of neuroblastomas. Moreover, considering the ability of antisense MK oligodeoxyribonucleotide to suppress tumour growth of colorectal carcinoma cells in nude mice, as recently reported, the present study suggests that MK is a possible candidate molecular target for therapy for neuroblastomas.