ANTI-TUMOR EFFECT OF INTRAVENOUS TNFα GENE DELIVERY NAKED PLASMID DNA USING A HYDRODYNAMICS-BASED PROCEDURE

High levels of foreign gene expression in mouse hepatocytes can be achieved by the rapid injection of a large volume of naked plasmid (pDNA) into animals via the tail vein, the so-called hydrodynamics-based procedure. In this study, we evaluated the efficacy of hydrodynamics-based tumor necrosis factor alpha (TNFα) transfer for tumor treatment, in which the naked pDNA encoding TNFα was administered into the tail vein following an intravenous injection of B16 melanoma cells. The mice treated with TNFα-expressing pDNA displayed a profound reduction in lung metastasis. These results suggest that the hydrodynamics-based transfer of naked pDNA is a convenient and efficient method of TNFα gene therapy against metastatic tumors.     

Anti-tumor effect of intravenous TNFalpha gene delivery naked plasmid DNA using a hydrodynamics-based procedure

High levels of foreign gene expression in mouse hepatocytes can be achieved by the rapid injection of a large volume of naked plasmid (pDNA) into animals via the tail vein, the so-called hydrodynamics-based procedure. In this study, we evaluated the efficacy of hydrodynamics-based tumor necrosis factor alpha (TNFalpha) transfer for tumor treatment, in which the naked pDNA encoding TNFalpha was administered into the tail vein following an intravenous injection of B16 melanoma cells. The mice treated with TNFalpha-expressing pDNA displayed a profound reduction in lung metastasis. These results suggest that the hydrodynamics-based transfer of naked pDNA is a convenient and efficient method of TNFalpha gene therapy against metastatic tumors.     

Hydrodynamics-based procedure involves transient hyperpermeability in the hepatic cellular membrane: implication of a nonspecific process in efficient intracellular gene delivery

BACKGROUND: The mechanisms underlying the efficient gene transfer by a large-volume and high-speed intravenous injection of naked plasmid DNA (pDNA), a so-called hydrodynamics-based procedure, remain unclear and require further investigation. In this report, we have investigated possible mechanisms for the intracellular transport of naked pDNA by this procedure. METHODS: Propidium iodide (PI), a fluorescent indicator for cell membrane integrity, and luciferase- or green fluorescent protein (GFP)-expressing pDNA were injected into mice by the hydrodynamics-based procedure. RESULTS: PI was efficiently taken up by hepatocytes which appeared to be viable following the hydrodynamics-based procedure. Pre-expressed GFP in the cytosol was rapidly eliminated from the hepatocytes by a large-volume injection of saline. The profiles of plasma ALT and AST showed a steady decline with the highest values observed immediately after the hydrodynamics-based procedure. These results suggest that the hydrodynamics-based procedure produces a transient increase in the permeability of the cell membrane. The cellular uptake process appeared nonspecific, since simultaneous injection of an excess of empty vector did not affect the transgene expression. Sequential injections of a large volume of pDNA-free saline followed by naked pDNA in a normal volume revealed that the increase in membrane permeability was transient, with a return to normal conditions within 30 min. Transgene expression was observed in hepatocyte cultures isolated 10 min after pDNA delivery and in the liver as early as 10 min after luciferase-expressing RNA delivery, indicating that pDNA delivered immediately by the hydrodynamics-based procedure has the potential to produce successful transgene expression. CONCLUSIONS: These findings suggest that the mechanism for the hydrodynamics-based gene transfer would involve in part the direct cytosolic delivery of pDNA through the cell membrane due to transiently increased permeability.     

Stimulatory effect of polyethylene glycol (PEG) on gene expression in mouse liver following hydrodynamics-based transfection

BACKGROUND: Rapid intravenous injection of a large volume of plasmid DNA (pDNA), i.e. a transfection procedure based on hydrodynamics, is known to be an efficient and liver-specific method of in vivo gene delivery. However, the gene expression is transient. METHODS: We investigated the effect of addition of polyethylene glycol (PEG) to a solution of naked pDNA (luciferase) on the expression of the gene in mouse liver following transfection by the hydrodynamics-based technique. In addition, the mechanism leading to the enhancement of the gene expression was studied. RESULTS: The addition of 1% (w/v) PEG2000 to the pDNA solution enhanced the resulting gene expression in the liver. Increasing the PEG2000 concentration to more than 1 and up to 10% (w/v) rather diminished the gene expression level. By contrast, increasing the molecular weight of PEG to over 2000 up to 10 000 did not affect the level of gene expression. Histopathological and serum-chemistry examinations indicated that hydrostatic or osmotic pressure increased tissue and hepatocellular damage in a PEG-concentration-dependent manner, and resulted in a decrease in gene expression. Quantitative evaluation showed that the enhanced gene expression resulted from stabilization of the pDNA introduced into the hepatocytes and an enhancement of the transport of intact pDNA to the nucleus. CONCLUSIONS: For most gene therapy applications and gene function studies, sustained expression of the introduced gene(s) is necessary. This simple method to achieve enhanced gene expression in liver may have a great potential for a wide variety of laboratory studies in molecular and cellular biology as well as possibly for future clinical applications in humans.     

Role of organ-associated NK cells in decreased formation of experimental metastases in lung and liver

Mice treated with anti-asialo GM1 (asGM1) serum exhibited increased formation of experimental metastases in lung and liver after i.v. challenge with B16 melanoma or Lewis lung carcinoma. This increased metastasis formation coincided with decreased splenic NK activity and increased survival of i.v. injected radiolabeled tumor cells. In contrast, the injection of mice with the pyran copolymer maleic anhydride divinyl ether (MVE-2) augmented NK activity in the spleen and significantly depressed the formation of experimental metastases in the lungs and liver. However, a single or double administration of anti-asGM1 antiserum to MVE-2-pretreated mice failed to inhibit the immunoprophylaxis associated with MVE-2 administration, although it did decrease splenic NK activity and also increased the survival of i.v.-injected radiolabeled tumor cells. To address the mechanism for this dichotomy, we examined NK activity not only in the spleen but also in the blood, lungs, and livers of MVE-2-treated mice. Levels of NK activity in the lungs and liver were several-fold higher than those observed in spleen and blood. However, MVE-2-augmented NK activity in lung and liver was more resistant to depletion by the standard regimen of anti-asGM1 treatment than was NK activity in blood and spleen, and required two high-dose administrations of a higher titered antiserum for depletion of the augmented response. This high-dose regimen removed all detectable NK activity from the lung and liver, and concomitantly eliminated the metastasis-inhibiting effect of MVE-2. These data are consistent with a role for organ-associated NK cells in inhibiting metastasis formation during the extravasation and/or early postextravasation phases of the metastatic process. The results also suggest that biologic effects of NK activity in spleen and blood can be dissociated from those mediated by NK activity in other organs by use of different treatment regimens with anti-asGM1 serum. Finally, because NK activity in target organs can be augmented to an even greater extent than in the blood and spleen by at least some biologic response modifiers (BRMs), organ-associated NK activity should be considered as a possible mechanism for the therapeutic effects of BRM treatment.     

Mechanism of naked DNA clearance after intravenous injection

BACKGROUND: Injection of naked DNA has been viewed as a safer alternative to current gene delivery systems; however, the rate of clearance from the circulation has been a constant barrier in developing these methods. Naked DNA after intravenous (i.v.) injection will be taken up by the liver and depredated by serum nucleases. MATERIALS AND METHODS: Our study examines the mechanisms involved in clearance of naked DNA by each compartment, the blood and the liver, in an in vivo mouse model. Confocal microscopy and transmission electron microscopy were employed to identify the type of cells taking up DNA and the barrier to DNA access to hepatocytes, respectively. RESULTS: Our data showed the liver could take up over 50% of 5 microg perfused pDNA, with a maximum 25 microg of pDNA during a single pass, and a slower clearance rate compared to that of liver uptake. It was demonstrated that naked DNA is primarily taken up by the liver endothelial cells and this endothelial barrier to transfection could be overcome by manually massaging the liver, which enlarges the fenestrae. CONCLUSIONS: This study clarifies the mechanism by which naked DNA is eliminated from the circulation after i.v. injection, focusing on the role of both the liver and blood compartments in vivo (i.e. mouse). With this knowledge, we can more clearly understand the mechanism of naked DNA clearance and develop more efficient strategies for DNA transfer in vivo.     

Rat liver-targeted naked plasmid DNA transfer by tail vein injection

High levels of foreign gene expression in mouse hepatocytes can be achieved by "hydrodynamics-based transfection," the rapid injection of a large volume of a naked deoxyribonucleic acid (DNA) solution into the tail vein. Rats are more tolerant of the frequent phlebotomies required for monitoring blood parameters than mice and, thus, are more suitable for some biomedical research. Recently, we demonstrated that hydrodynamics-based transfection can also be used to deliver naked plasmid DNA into the normal rat, which is more than 10 times larger than the mouse. We performed the tail vein injection using a syringe with a winged needle equipped with an external tube. Injection of a lac Z expression plasmid, pCAGGS-lac Z by this technique resulted in the exclusive detection of beta-galactosidase in the liver. We also injected a rat erythropoietin (Epo) expression plasmid, pCAGGS-Epo (800 microg). Maximal Epo gene expression was achieved when a 25-mL injection volume (approx 100 mL/kg body wt) was transferred within 15 s.     

Essential role of bystander cytotoxic CD122+CD8+ T cells for the antitumor immunity induced in the liver of mice by alpha-galactosylceramide

We recently reported that NK cells and CD8(+) T cells contribute to the antimetastatic effect in the liver induced by alpha-galactosylceramide (alpha-GalCer). In the present study, we further investigated how CD8(+) T cells contribute to the antimetastatic effect induced by alpha-GalCer. The injection of anti-CD8 Ab into mice 3 days before alpha-GalCer injection (2 days before intrasplenic injection of B16 tumors) did not inhibit IFN-gamma production nor did it reduce the NK activity of liver mononuclear cells after alpha-GalCer stimulation. However, it did cause a reduction in the proliferation of liver mononuclear cells and mouse survival time. Furthermore, although the depletion of NK and NKT cells (by anti-NK1.1 Ab) 2 days after alpha-GalCer injection no longer decreased the survival rate of B16 tumor-injected mice, the depletion of CD8(+) T cells did. CD122(+)CD8(+) T cells in the liver increased after alpha-GalCer injection, and antitumor cytotoxicity of CD8(+) T cells in the liver gradually increased until day 6. These CD8(+) T cells exhibited an antitumor cytotoxicity toward not only B16 cells, but also EL-4 cells, and their cytotoxicity significantly decreased by the depletion of CD122(+)CD8(+) T cells. The critical, but bystander role of CD122(+)CD8(+) T cells was further confirmed by adoptive transfer experiments into CD8(+) T cell-depleted mice. Furthermore, it took 14 days after the first intrasplenic B16/alpha-GalCer injection for the mice to generate CD8(+) T cells that can reject s.c. rechallenged B16 cells. These findings suggest that alpha-GalCer activates bystander antitumor CD122(+)CD8(+) T cells following NK cells and further induces an adaptive antitumor immunity due to tumor-specific memory CD8(+) CTLs.     

Inhibition of colon cancer growth and metastasis by NK4 gene repetitive delivery in mice

NK4, originally prepared as a competitive antagonist for hepatocyte growth factor (HGF), is a bifunctional molecule that acts as an HGF-antagonist and angiogenesis inhibitor. When the expression plasmid for NK4 gene was administered into mice by hydrodynamics-based delivery, the repetitive increase in the plasma NK4 protein level was achieved by repetitive administration of NK4 gene. Mice were subcutaneously implanted with colon cancer cells and weekly given with the NK4 plasmid. The repetitive delivery and expression of NK4 gene inhibited angiogenesis and invasiveness of colon cancer cells in subcutaneous tumor tissue and this was associated with suppression of primary tumor growth. By fifty days after tumor implantation, cancer cells naturally metastasized to the liver, whereas NK4 gene expression potently inhibited liver metastasis. Inhibition of the HGF-Met receptor pathway and tumor angiogenesis by NK4 gene expression has potential therapeutic value toward inhibition of invasion, growth, and metastasis of colon cancer.     

Activating immunity in the liver. II. IFN-beta attenuates NK cell-dependent liver injury triggered by liver NKT cell activation

Dendritic cell (DC)-dependent activation of liver NKT cells triggered by a single i.v. injection of a low dose (10-100 ng/mouse) of alpha-galactosyl ceramide (alphaGalCer) into mice induces liver injury. This response is particularly evident in HBs-tg B6 mice that express a transgene-encoded hepatitis B surface Ag in the liver. Liver injury following alphaGalCer injection is suppressed in mice depleted of NK cells, indicating that NK cells play a role in NK T cell-initiated liver injury. In vitro, liver NKT cells provide a CD80/86-dependent signal to alphaGalCer-pulsed liver DC to release IL-12 p70 that stimulates the IFN-gamma response of NKT and NK cells. Adoptive transfer of NKT cell-activated liver DC into the liver of nontreated, normal (immunocompetent), or immunodeficient (RAG(-/-) or HBs-tg/RAG(-/-)) hosts via the portal vein elicited IFN-gamma responses of liver NK cells in situ. IFN-beta down-regulates the pathogenic IL-12/IFN-gamma cytokine cascade triggered by NKT cell/DC/NK cell interactions in the liver. Pretreating liver DC in vitro with IFN-beta suppressed their IL-12 (but not IL-10) release in response to CD40 ligation or specific (alphaGalCer-dependent) interaction with liver NKT cells and down-regulated the IFN-gamma response of the specifically activated liver NKT cells. In vivo, IFN-beta attenuated the NKT cell-triggered induction of liver immunopathology. This study identifies interacting subsets of the hepatic innate immune system (and cytokines that up- and down-regulate these interactions) activated early in immune-mediated liver pathology.     

Intradermal delivery of IL-12 naked DNA induces systemic NK cell activation and Th1 response in vivo that is independent of endogenous IL-12 production.

In this study four murine IL-12 naked DNA expression plasmids (pIL-12), containing both the p35 and p40 subunits, were shown to induce systemic biological effects in vivo after intradermal injection. Three of the four IL-12 expression vectors augmented NK activity and induced expression of the IFN-gamma and IFN-gamma-inducible Mig genes. Both IL-12 p70 heterodimer and IFN-gamma proteins were documented in the serum within 24 h after intradermal injection of the pIL-12o- plasmid, which also induced the highest level of NK activity in the spleen and liver among the IL-12 constructs. Interestingly, both p40 mRNA expression at the injection site and serum protein levels followed a biphasic pattern of expression, with peaks on days 1 and 5. Subsequent studies revealed that the ability of intradermally injected pIL-12o- to augment NK lytic activity was prevented by administration of a neutralizing anti-IL-12 mAb. Finally, injection of the pIL-12o- into BALB/c IL-12 p40-/- mice also resulted in a biphasic pattern of IL-12 p70 appearance in the serum, and induced IFN-gamma protein and activated NK lytic activity in liver and spleen. These results demonstrate that injection of delivered naked DNA encoding the IL-12 gene mediates the biphasic systemic production of IL-12-inducible genes and augments the cytotoxic function of NK cells in lymphoid and parenchymal organs as a direct result of transgene expression. The results also suggest that these naked DNA plasmids may be useful adjuvants for vaccines against infectious and neoplastic diseases.     

Systemic administration of LPD prepared with CpG oligonucleotides inhibits the growth of established pulmonary metastases by stimulating innate and acquired antitumor immune responses

Intravenous (i.v.) administration of a lipopolyplex consisting of a ternary complex of DOTAP:cholesterol cationic liposomes, protamine sulfate, and noncoding plasmid DNA (LPD-pDNA) is capable of stimulating a potent Th-1 cytokine response and inhibiting the growth of established tumors in mice. Both activities are mainly elicited by unmethylated CpG motifs in the plasmid DNA (pDNA) component, which are bacterial in origin. Since oligodeoxynucleotides (ODN) that possess a consensus immunostimulatory CpG motif of RRCpGYY (R is purine and Y is pyrimidine) can mimic the immunostimulatory actions of bacterial DNA, we hypothesized that i.v. administration of LPD prepared with GpG-ODN would mimic the ability of LPD-pDNA to stimulate Th-1 cytokines and antitumor activity and provide an improved vector for probing the immune mechanisms underlying the observed antitumor effects. These hypotheses were tested for the treatment of established 24JK experimental pulmonary metastases that are syngeneic in C57BL/6 mice. Mice treated with LPD containing 25 microg of the prototypical phosphodiester (PO) CpG-ODN 1668 (tccatGACGTTcctgatgct, motif capitalized) demonstrated a dramatic reduction in lung tumor burden (>80% inhibition, P<0.01) compared to dextrose-treated controls. The antitumor effect was dependent on the CpG dinulceotide and correlated with the ability to stimulate serum Th-1 cytokines (TNF-alpha, IL-12, and IFN-gamma). Both activities required assembly of CpG-ODN in a cationic liposome/DNA complex (lipoplex) or the LPD lipopolyplex. LPD delivery of both PO-1668 and phosphorothioated (PS)-1668 stimulated a greater cytokine response compared to delivery of free ODN. Furthermore, within the LPD complex, both PO- and PS-1668 had similar ability to stimulate Th-1 cytokines with respect to potency and duration of response, thus eliminating the need for the PS modification. In tumor cell lysis assays, LPD-CpG DNA stimulated development of an acquired, tumor-specific CD8+ cytotoxic T-lymphocyte (CTL) activity that was dependent on CpG DNA. LPD was also capable of stimulating NK activity; however, this was not dependent on CpG DNA. Only formulations that concomitantly stimulated NK activity and CpG-specific, Th-1 cytokine were capable of stimulating the development of tumor-specific CTL activity and significant inhibition of tumor growth. Thus, we propose a model where CpG DNA in complex with cationic liposome-based lipoplexes or lipopolyplexes stimulates antitumor NK activity and CpG-stimulated Th-1 cytokine production. The combination of these two activities of the innate immune system subsequently direct the development of an acquired, tumor-specific CTL response that in total are effective for inhibiting the growth of established tumors in mice.     

CpG-free plasmids confer reduced inflammation and sustained pulmonary gene expression

Pulmonary delivery of plasmid DNA (pDNA)/cationic liposome complexes is associated with an acute unmethylated CG dinucleotide (CpG)-mediated inflammatory response and brief duration of transgene expression. We demonstrate that retention of even a single CpG in pDNA is sufficient to elicit an inflammatory response, whereas CpG-free pDNA vectors do not. Using a CpG-free pDNA expression vector, we achieved sustained (>or=56 d) in vivo transgene expression in the absence of lung inflammation.     

Mechanisms of the antimetastatic effect in the liver and of the hepatocyte injury induced by alpha-galactosylceramide in mice

The role of mouse liver NK1.1 Ag(+) T (NKT) cells in the antitumor effect of alpha-galactosylceramide (alpha-GalCer) has been unclear. We now show that, whereas alpha-GalCer increased the serum IFN-gamma concentration and alanine aminotransferase activity in NK cell-depleted C57BL/6 (B6) mice and B6-beige/beige mice similarly to its effects in control B6 mice, its enhancement of the antitumor cytotoxicity of liver mononuclear cells (MNCs) was abrogated. Depletion of both NK and NKT cells in B6 mice reduced all these effects of alpha-GALCER: Injection of Abs to IFN-gamma also inhibited the alpha-GalCer-induced increase in antitumor cytotoxicity of MNCS: alpha-GalCer induced the expression of Fas ligand on NKT cells in the liver of B6 mice. Whereas alpha-GalCer did not increase serum alanine aminotransferase activity in B6-lpr/lpr mice and B6-gld/gld mice, it increased the antitumor cytotoxicity of liver MNCS: The alpha-GalCer-induced increase in survival rate apparent in B6 mice injected intrasplenically with B16 tumor cells was abrogated in beige/beige mice, NK cell-depleted B6 mice, and B6 mice treated with Abs to IFN-gamma. Depletion of CD8(+) T cells did not affect the alpha-GalCer-induced antitumor cytotoxicity of liver MNCs but reduced the effect of alpha-GalCer on the survival of B6 mice. Thus, IFN-gamma produced by alpha-GalCer-activated NKT cells increases both the innate antitumor cytotoxicity of NK cells and the adaptive antitumor response of CD8(+) T cells, with consequent inhibition of tumor metastasis to the liver. Moreover, NKT cells mediate alpha-GalCer-induced hepatocyte injury through Fas-Fas ligand signaling.     

Endogenous natural killer cells do not play a role in antitumor effects induced by interleukin-2 in a syngeneic rat colon tumor model

Previous experiments in a syngeneic rat liver tumor model using the colon adenocarcinoma CC531 demonstrated that injection of interleukin-2 (IL-2) induced significant antitumor responses. Furthermore, it was found that this treatment strategy was accompanied by an increase in the number of natural killer (NK) cells in and around the tumor. In the present study, the role of endogenous NK cells in IL-2-mediated antitumor responses was further elucidated by depleting tumor-bearing rats of NK cells, using the anti-CD161A mouse IgG1 antibody 3.2.3. Rats were depleted either after or prior to tumor induction and subsequently treated with IL-2. The results demonstrated that depletion of NK cells in tumor-bearing rats did not influence IL-2-induced antitumor effects. In addition, injection of IL-2 in NK-cell-depleted rats induced repopulation of NK cells in the peripheral blood from 3 days on and further after the last injection with IL-2. Therefore, the possibility cannot be excluded that de novo recruited NK cells play a role in attaining IL-2 mediated antitumor effects, but NK cells, which were present before or during the start of IL-2 therapy, were not relevant. Received: 25 March 1999 / Accepted: 22 July 1999     

Combined radiation therapy and dendritic cell vaccine for treating solid tumors with liver micro-metastasis

BACKGROUND: Tumor metastasis and relapse are major obstacles in combating human malignant diseases. Neither radiotherapy alone nor injection of dendritic cells (DCs) can successfully overcome this problem. Radiation induces tumor cell apoptosis and necrosis, resulting in the release of tumor antigen and danger signals, which are favorable for DC capturing antigens and maturation. Hence, the strategy of combined irradiation and DC vaccine may be a novel approach for treating human malignancies and early metastasis. METHODS: To develop an effective combined therapeutic approach, we established a novel concomitant local tumor and liver metastases model through subcutaneous (s.c.) and intravenous (i.v.) injection. We selected the optimal time for DC injection after irradiation and investigated the antitumor effect of combining irradiation with DC intratumoral injection and the related mechanism. RESULTS: Combined treatment with radiotherapy and DC vaccine could induce a potent antitumor immune response, resulting in a significant decrease in the rate of local tumor relapse and the numbers of liver metastases. The related mechanisms for this strong antitumor immunity of this combined therapy might be associated with the production of apoptotic and necrotic tumor antigens and heat shock proteins after irradiation, phagocytosis, migration and maturation of DCs, and induction of more efficient tumor-specific cytotoxic T lymphocyte activity through a cross-presentation pathway. CONCLUSIONS: Co-administration of local irradiation and intratumoral DC injection may be a promising strategy for treating radiosensitive tumors and eliminating metastasis in the clinic.     

Mechanism of plasmid delivery by hydrodynamic tail vein injection. II. Morphological studies

BACKGROUND: The efficient delivery of plasmid DNA (pDNA) to hepatocytes by a hydrodynamic tail vein (HTV) procedure has greatly popularized the use of naked nucleic acids. The hydrodynamic process renders onto the tissue increased physical forces in terms of increased pressures and shear forces that could lead to transient or permanent membrane damage. It can also trigger a series of cellular events to seal or reorganize the stretched membrane. Our goal was to study the uptake mechanism by following the morphological changes in the liver and correlate these with the fate of the injected plasmid DNA. METHODS: We utilized both light microscopic (LM) and electron microscopic (EM) techniques to determine the effect of the HTV procedure on hepatocytes and non-parenchymal cells at various times after injection. The LM studies used paraffin-embedded livers with hematoxylin and eosin (H&E) staining. The immune-EM studies used antibodies labeled with sub-nanometer gold particles followed by silver enhancement to identify the location of injected pDNA at the subcellular level. The level of overall damage to liver cells was estimated based on alanine aminotransferase (ALT) release and clearance. RESULTS: Both the LM and EM results showed the appearance of large vesicles in hepatocytes as early as 5 min post-injection. The number of vesicles decreased by 20-60 min. Plasmid DNA molecules often appeared to be associated with or inside such vesicles. DNA could also be detected in the space of Disse, in the cytoplasm and in nuclei. Non-parenchymal cells also contained DNA, but HTV-induced vesicles could not be observed in them. CONCLUSIONS: Our studies suggest an alternative or additional pathway for naked DNA into hepatocytes besides direct entry via membrane pores. It may be difficult to prove which of these pathways lead to gene expression, but the membrane pore hypothesis alone appears insufficient to explain why expression happens preferentially in hepatocytes. Further study is needed to delineate the importance of each of these putative pathways and their interrelationship in enabling oligonucleotide (siRNA) activity and pDNA expression.     

In vivo Site-Specific Transfection of Naked Plasmid DNA and siRNAs in Mice by Using a Tissue Suction Device

We have developed an in vivo transfection method for naked plasmid DNA (pDNA) and siRNA in mice by using a tissue suction device. The target tissue was suctioned by a device made of polydimethylsiloxane (PDMS) following the intravenous injection of naked pDNA or siRNA. Transfection of pDNA encoding luciferase was achieved by the suction of the kidney, liver, spleen, and heart, but not the duodenum, skeletal muscle, or stomach. Luciferase expression was specifically observed at the suctioned region of the tissue, and the highest luciferase expression was detected at the surface of the tissue (0.12±0.03 ng/mg protein in mice liver). Luciferase expression levels in the whole liver increased linearly with an increase in the number of times the liver was suctioned. Transfection of siRNA targeting glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene significantly suppressed the expression of GAPDH mRNA in the liver. Histological analysis shows that severe damage was not observed in the suctioned livers. Since the suction device can be mounted onto the head of the endoscope, this method is a minimally invasive. These results indicate that the in vivo transfection method developed in this study will be a viable approach for biological research and therapies using nucleic acids.     

Antimetastatic effect of recombinant human macrophage-colony-stimulating factor against lung and liver metastatic B16 melanoma

 We studied the effect of recombinant human macrophage-colony-stimulating factor (rhM-CSF) on the formation of lung and liver metastases following the i.v. injection of the B16 melanoma subline (B16 LiLu) into mice. When rhM-CSF was administered before the B16 inoculation, the number of tumor metastases decreased in the lung and liver. However, the administration of rhM-CSF after B16 inoculation did not produce an antimetastatic effect in the lung, but did in the liver. B16 cells labeled with 5-[¹²⁵I]-iodo-2′-deoxyuridine (¹²⁵I-dUrd) were injected and the arrest of tumor cell emboli was examined in the capillary beds of the lung and liver of mice treated with either vehicle or rhM-CSF. In both groups, there were the same numbers of B16 cells in both the lung and the liver 3 minutes after the B16 injection, and almost all tumor cells died within 24 h. However, the number of cells surviving in the lung was decreased in mice injected with rhM-CSF (37%). There was no difference in the number of cells in the livers of mice treated either with vehicle or rhM-CSF in the first 24 h after tumor cell injection. The administration of rhM-CSF increased NK 1.1⁺ cells in the mouse spleen and facilitated NK activity in vivo. At the same time, the administration of an anti-NK 1.1 antibody blocked the antimetastatic effect of rhM-CSF in the lung but not in the liver. The antibody was effective only when it was injected before the B16 inoculation. These results suggest that the antimetastatic effect of rhM-CSF in the lung was mediated by NK 1.1⁺ cells within 24 h of B16 injection. In contrast, the antimetastatic effect of rhM-CSF in the liver was mediated not only by NK 1.1⁺ cells but also by other antimetastatic systems such as macrophages. Received: 8 April 1996 / Accepted: 26 November 1996