Anti-asialo GM1 Research Articles

Reduction of liver metastasis of intraocular melanoma by interferon-beta gene transfer.

This study determined whether adenovirus-mediated transfer of the murine interferon-beta (AdCMVIFN-beta) gene protects against liver metastases arising from intraocular melanomas in mice. A replication-deficient adenovirus vector (AdCMVIFN-beta) was used for the in vivo transfer of the murine IFN-beta gene into intraocular melanoma-bearing mice. AdCMVIFN-beta was injected either intravenously or directly into the intraocular melanomas. The effect of gene transfer on liver metastases was ascertained by histopathologic analysis of the livers and by measuring serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), which are two enzymes associated with liver metastases in patients with uveal melanoma. Mice treated with two intratumoral injections of AdCMVIFN-beta had a 68% reduction in metastatic liver lesions (P = 0.016) and a 51% reduction in liver enzyme levels compared with control mice (P = 0.02). However, the antimetastatic effect of AdCMVIFN-beta was not directly attributable to the adenovirus vector or virus-mediated cytolysis of tumor cells. Intravenous treatment with AdCMVIFN-beta resulted in an 86% reduction in the number of metastatic foci in the liver (P = 0.014) and a 61% reduction of serum AST levels compared with mice treated with AdCMVLacZ (P = 0.015). AdCMVIFN-beta treatment produced a sharp increase in the NK cell activity that was demonstrable in vivo and in vivo. In vivo depletion of NK cells by anti-asialo GM1 antibody abrogated the antimetastatic effects of AdCMVIFN-beta. The results support the feasibility of activation of NK cell function through gene transfer as one possible therapeutic strategy for reducing hepatic metastases of uveal melanomas.

CD1d-mediated stimulation of natural killer T cells selectively activates hepatic natural killer cells to eliminate experimentally disseminated hepatoma cells in murine liver.

Since hepatocellular carcinomas (HCCs) develop from transformed hepatocytes, sometimes in a multicentrical manner, immunological deletion of such small intrahepatic regions should be an important strategy to prevent HCC development. The liver contains abundant innate cell lineages including natural killer (NK) cells and natural killer T (NKT) cells, the latter of which become activated in a CD1d-restricted manner by alpha-galactosylceramide (alpha-GalCer). In our study, we investigated the anti-tumor effect elicited by alpha-GalCer administration against transplanted hepatoma cells in the liver, in comparison with that in extrahepatic sites. alpha-GalCer administration completely suppressed the growth of BNL 1MEA.7R.1 (BNL) hepatoma cells disseminated in the liver of syngeneic BALB/c mouse but had no anti-tumor effect on subcutaneously implanted BNL cells. Hepatic NKT cells became rapidly activated after alpha-GalCer administration compared to splenic NKT cells and then disappeared. Hepatic NK cells substantially increased their population as well as up-regulated their cytotoxic activity against BNL cells, but NK cells in other tissues, including the spleen, blood and lymph node, did not. Anti-asialo GM1 antibody treatment, which depleted NK cells in vivo, resulted in hepatic tumor formation in alpha-GalCer-treated mice, indicating the critical involvement of NK cells in the alpha-GalCer-induced anti-tumor effect in the liver. In conclusion, our study demonstrates clear differences in NK cell activation and anti-tumor effect through stimulation of NKT cells by alpha-GalCer between the liver and extrahepatic tissues. Sequential activation of these innate cell lineages may be an attractive strategy for controlling micro-disseminated hepatoma cells in the liver.

Induction of systemic immunity by expression of interleukin-23 in murine colon carcinoma cells.

Interleukin-23 (IL-23), a novel cytokine composed of a newly identified p19 molecule and the p40 subunit of IL-12, can stimulate the proliferation in vitro of memory T cells. We examined whether Colon 26 murine colon carcinoma cells that were retrovirally transduced with the p19-linked p40 gene (Colon 26/IL-23) could produce antitumor effects in inoculated mice. The growth of Colon 26/IL-23 tumors developed in immunocompetent mice was significantly retarded and the tumors disappeared thereafter. Spleen cells from the mice that received Colon 26/IL-23 cells produced significant amounts of interferon-gamma, when they were cultured with irradiated Colon 26 but not irrelevant cells. Depletion of CD8(+) T cells suppressed the production of interferon-gamma. The mice that had rejected Colon 26/IL-23 tumors were resistant to subsequent challenge of parent but not irrelevant tumor cells. Colon 26/IL-23 tumors were not rejected in nude mice but the growth was retarded compared to parent tumors. Treatment of nude mice with anti-asialo GM(1) antibody did not influence the growth of Colon 26/IL-23 tumors. These data suggest that expression of IL-23 in tumors produces T cell-dependent antitumor effects and induces systemic immunity.

Athymic nu/nu (nude) mice are resistant to CD45RBhigh T-cell-mediated chronic colitis: Role of NK and B-cells

h~troduction: Recent studiesd'rom our laborato U suggest that transter of CD4+CD45RB h~g~ T<dls horn normal donors into nude mice t)ils to induce chronic colitis in these immunodehcient mice The obfective of this study was to assess the role of natural killer (NK) and B-cells <:ells in preventing or suppressing the development of colitis in this transfer model. Methods BALg/t tL4G-1 ' or nude mice were injected (i.p.) with 5 x 10 ~ CD4+CD45RB h'~ T-cells trom wild type (wt) BALWc donors NK cells were depleted in reconstituted nude mice weekly injections of anti-asialo GM-1 antibody. At 8 weeks following reconstitution, all mice were sacrificed, ttmir colons removed, weighed, measured, scored and graded in a blinded hshion lor histological evidence d colitis Chimeric nude mice were produced whoIe body lethaI irradiation (1000 rads) tbllowed reconstitution with 5 x 10 ~ whole bone marrow cells from either nude, J heavy chain deficient (J~) or RAG1 ~ donors Deletion of either B<el/s or NK cells was conhrmed flow cytometry. Results: In agreement with our prevrous stu&es, we found that made mice are resistant to CD45RB~~:-indueed colitis compared to RAG-1 recipients as as~ssed by colon length (10.3 _+ 0.55 vs. 8.15 _+ 0.26 cm), weighi (0.44 + 0.02 vs 0.66 _+ 0.04 g) and gross mBammation score (0 -+ 0 vs. 3 .25:2 0.38) tot nude vs. RAGd 4 , respectively. Histological scores of each colon revealed no evidence of mtlammation in reconstituted nude mice when compared to RAG-V mice (27 • 0.67 vs. 14.9 • 0.68, respectively). The lack of colitis was not due to defects in repopulatiou of the gut w~th CD4* T<efis as reconstituted nude mice contained similar nmubers ot CD4' cells (approximately 2.6 x 10Vcm 3) as did reconstituted RAG-1 v mice. Interestingly, chimeric nude mice lacking all lympho~tes (RAG-Ie -* nude) reconstituted with CD45RB ~*~ T-cells developed severe colitis whereas nude mice depleted of either NK or B-cells and titan injected with CD45RB ~'~' T-cells did not develop chronic gut intlammation. Conclusions: Ath~mric nude' mice do not develnp colitis in response to CD45RB ~'~ T-cell transier despite having nomral engraftment of T-calls in the gut. Depletion of NK or B-cells in reconstituted nude mice did induce disease suggesting that other leukocTtes (e.g. IELs) may be important regulatory cells in this T-cell transfer model (Supported the Broad Medical Research Program)

Expression of the interleukin-21 gene in murine colon carcinoma cells generates systemic immunity in the inoculated hosts.

Interleukin-21 (IL-21) is a novel cytokine that can induce proliferation of activated T cells and maturation of natural killer (NK) cells. We therefore examined whether expression of the IL-21 gene in tumor cells could generate antitumor responses. Murine colon carcinoma Colon 26 cells that were transduced with the mouse IL-21 gene (Colon 26/IL-21) were rejected in syngeneic mice and the mice subsequently acquired protective immunity. The growth of Colon 26/IL-21 tumors developed in nude mice was retarded compared with that of parent tumors, and this growth suppression was not observed in nude mice that were treated with anti-asialo GM(1) antibody. Spleen cells from the mice that had rejected Colon 26/IL-21 cells showed cytotoxic activity to Colon 26 but not to irrelevant tumor cells, and produced larger amounts of interferon-gamma upon stimulation with irradiated Colon 26 cells. Spleen cells from Colon 26/IL-21-tumor- but not parent-tumor-bearing mice had lytic activity to YAC-1 cells. These data suggest that expression of IL-21 in tumors induces T- and NK-cell-dependent antitumor effects.

Cellular mechanisms of interleukin-12–mediated neuroblastoma regression

Background/Purpose: Interleukin-12 (IL-12) is a proinflammatory cytokine with potent antitumor effects. Previous studies from the authors laboratory showed regression of established neuroblastoma in mice vaccinated with IL-12 transduced dendritic cells (DC). Although regression was associated with intense T cell infiltration, the precise role of T cells is unknown. The purpose of this work is to study the cellular mechanisms in IL-12–mediated tumor regression. Methods: Three groups of mice (n = 12) received subcutaneous inoculation with 1 × 106 murine neuroblastoma cells (TBJ). Anti-CD4 (T helper), anti-CD8 (T cytotoxic), or antiasialo-GM1 (natural killer) antibodies were injected intravenously at 3-day intervals to deplete various immune effector cell populations. Mice in each depletion group and the control (nondepleted) group were injected intratumorally on day 7 with 1 × 106 DC IL-12–transduced DC. Tumors were harvested for morphometry and immunohistochemistry at 21 days. Results: CD4 depletion had no effect on tumor growth in either control or IL-12–vaccinated animals. In contrast, CD8-depleted animals treated with IL-12–transduced DC underwent initial regression followed by progressive tumor growth (P <.01). These tumors were smaller in size at the same time-point. However, NK cell depletion (antiasialo GM1) completely abrogated the antitumor effects of IL-12–transduced DC, leading to progressive tumor growth from the outset. There was no difference between the control and treated animals in this group. Conclusions: Contrary to our hypothesis that IL-12 DC primarily function to stimulate a T cell–mediated response, these data suggest that NK cells are essential for the initial antitumor response of animals treated with IL-12–transduced DC. CD8+ T cells appear to be necessary effector cells for complete rejection of tumor and possibly memory. NK cells are responsible for the early immune response. Furthermore, CD4+ (T helper) cells did not play any role in IL-12–induced regression. These results imply that for DC to generate an effective antitumor response against neuroblastoma both acquired and innate effector cells are required. J Pediatr Surg 38:199-204. Copyright 2003, Elsevier Science (USA). All rights reserved.

Natural killer cells participate in bacterial clearance during septic peritonitis through interactions with macrophages.

Natural killer (NK) cells have a well-established role in host defense against viral infections and malignancies. However, their function in bacterial infection and sepsis is poorly defined. We hypothesized that NK cells, as a major producer of interferon-gamma during sepsis, would be important in host defense against bacterial infections. Cecal ligation and puncture (CLP) was performed on Swiss Webster mice depleted of NK cells by pretreatment with anti-asialo GM1 and control mice given immunoglobulin G (IgG) antibody. NK cell-depleted mice had significantly higher anaerobic bacterial counts in the liver and peritoneal lavage fluid, as well as higher aerobic counts in the liver and blood 4 h after CLP. Macrophage phagocytosis, nitric oxide production, and interleukin (IL)-6 levels at 4 h were also decreased in mice depleted of NK cells compared with controls. Greater neutrophil influx into the peritoneum, indicated by higher myeloperoxidase levels, was also seen in NK cell-depleted mice. At 8 and 18 h after CLP, bacterial counts were similar between groups, and overall survival rates were not significantly different. Peritoneal IL-12 levels significantly increased by 18 h in normal mice, but not in NK cell-depleted animals. Our data suggest that NK cells participate in the early local and systemic eradication of bacteria and regulation of IL-12 during polymicrobial sepsis. These effects are likely due to their interactions with macrophages.

Prolongation of allogeneic skin graft survival by injection of anti-Ly49A monoclonal antibody YE1/48

Ly49A receptors expressed on NK, NKT, and T cells play inhibitory roles in regulating the immune responses in vivo and in vitro. Whether or not injection of anti-Ly49A monoclonal antibody (mAb) YE1/48 can block allograft rejection has not been evaluated. Balb/c mouse recipients received intraperitoneal injections of YE1/48 mAb (0.5 mg) or control mAb or phosphate-buffered saline on days −1 and 10. On day 0, fully MHC-mismatched allogeneic C57BL/6 (B6) skin grafts were implanted. The skin graft survival and anti-donor humoral responses were observed. Whereas allogeneic B6 skin grafts survived 14 days in isotopy control antibody-treated or nontreated Balb/c mice, injection of YE1/48 mAb significantly prolonged B6 skin graft survival to 19 days ( P < 0.0005). Injection of YE1/48 mAb into presensitized Balb/c recipients did not significantly delay B6 skin graft rejection. On the other hand, after depleting recipient NK, NKT, and some cytotoxic T cells by injection of anti-asialo GM1, YE1/48 failed to prolong B6 skin graft survival in Balb/c recipients. The present studies indicate that injection of YE1/48 mAb significantly delays allogeneic skin graft rejection in nonsensitized recipients but not in sensitized recipients. The presence of NK, NKT cells, and some cytotoxic T cells may be essential for YE1/48-mediated immunosuppression in vivo.

The Role of NK Cells in the Elicitation Phase of Oxazolone Inducing Contact Hypersensitivity

We studied the role of infiltrating cells and cytokines synthesis in oxazolone (OXA)-induced contact hypersensitivity (CHS) of C57BL/6 mouse ear model. The cell mediate lesion was induced by the OXA challenge after abdominal skin sensitization, and those of infiltrating cells were examined at various time points (0-168 hr). The CHS lesions were indicated as an ear swelling at 24 to 48 hr after the challenge that was caused mainly by infiltration of mononuclear cells expressing CD90+, CD4+ and CD8+. However, NK cells by means of asialo GM1+ cells, were detected in the lesions as early as 2 hr after challenge. The infiltration of NK cells peaked at 8 hr and replaced in the predominant accumulation of polymorphonuclear (PMN) cells and some of CD90+ cells. Cytokine expression of the infiltrating cells by RT-PCR, revealed a high level of IL-2 expression at 8, 12, and 24 hr and then reduced expression in the following times, while, IFN-γ was constantly detected from 2 hr to 168 hr. Deletion of the NK cell activity by administration of the anti-asialo GM1 antibody resulted in significantly suppressed cell infiltration and ear swelling. IL-2 mRNA expression was undetected in the infiltrating cells of deletion mouse, whereas IFN-γ was detected at 12, 24, and 48 hr. The presence of NK cells as the first infiltrating cells in the lesion and IL-2 and INF-γ synthesis from the infiltrating cells may play an important role in the elicitation phase of CHS.

Interleukin-18 inhibits lodging and subsequent growth of human multiple myeloma cells in the bone marrow

An intravenous injection of ARH-77 cells (human multiple myeloma cell line) into mice with severe combined immunodeficiency disease (SCID mice) results in lodging of tumor cells in the bone marrow of thoracic and lumbar vertebrae, and in their subsequent growth, the cells destroying bone and invading the spinal cord and surrounding tissues, and the mice show hind leg paralysis. Using this model, we investigated the effects of interleukin (IL)-18 on the lodging and subsequent growth of multiple myeloma cells in the bone marrow. Mouse recombinant IL-18 (mIL-18) at 1 microg/mouse was daily injected according to protocols A and B. In protocol A, mIL-18 was injected from day 6 after tumor cell injection to examine the effect of mIL-18 on tumor growth, and in protocol B, it was injected from day 3 prior to tumor cell injection to day 3 after it to examine the effect of mIL-18 on lodging of tumor cells. The spread of a tumor was monitored as to the appearance of hind leg paralysis and the tumor area in a median longitudinal section of the vertebrae with the surrounding tissues. With protocol A, mIL-18 significantly and markedly decreased the cumulative rate of hind leg paralysis and the tumor area. This antitumor effect of mIL-18 was ascribed to its action on the activation of NK cells because mIL-18 exerted no significant effect when anti-asialo GM1 antiserum (a-ASGM1) was simultaneously injected to deplete the NK cell activity. With protocol B, mIL-18 also significantly and markedly decreased the cumulative rate of hind leg paralysis and the tumor area. However, most of this effect was not due to the action of mIL-18 on NK cells because mIL-18 showed a marked and significant effect with the administration of a-ASGM1. The present results indicate that mIL-18 inhibited the lodging and subsequent growth of multiple myeloma cells in the bone marrow, and suggest that IL-18 is worth investigating further as to its usefulness as a therapy for multiple myeloma.

NOD/SCID/γcnull mouse: an excellent recipient mouse model for engraftment of human cells

AbstractTo establish a more appropriate animal recipient for xenotransplantation, NOD/SCID/γcnull mice double homozygous for the severe combined immunodeficiency (SCID) mutation and interleukin-2Rγ (IL-2Rγ) allelic mutation (γcnull) were generated by 8 backcross matings of C57BL/6J-γcnull mice and NOD/Shi-scidmice. When human CD34+ cells from umbilical cord blood were transplanted into this strain, the engraftment rate in the peripheral circulation, spleen, and bone marrow were significantly higher than that in NOD/Shi-scid mice treated with anti-asialo GM1 antibody or in the β2-microglobulin–deficient NOD/LtSz-scid (NOD/SCID/β2mnull) mice, which were as completely defective in NK cell activity as NOD/SCID/γcnull mice. The same high engraftment rate of human mature cells was observed in ascites when peripheral blood mononuclear cells were intraperitoneally transferred. In addition to the high engraftment rate, multilineage cell differentiation was also observed. Further, even 1 × 102 CD34+ cells could grow and differentiate in this strain. These results suggest that NOD/SCID/γcnull mice were superior animal recipients for xenotransplantation and were especially valuable for human stem cell assay. To elucidate the mechanisms involved in the superior engraftment rate in NOD/SCID/γcnull mice, cytokine production of spleen cells stimulated with Listeria monocytogenesantigens was compared among these 3 strains of mice. The interferon-γ production from dendritic cells from the NOD/SCID/γcnull mouse spleen was significantly suppressed in comparison with findings in 2 other strains of mice. It is suggested that multiple immunological dysfunctions, including cytokine production capability, in addition to functional incompetence of T, B, and NK cells, may lead to the high engraftment levels of xenograft in NOD/SCID/γcnull mice.

Living T9 glioma cells expressing membrane macrophage colony-stimulating factor produce immediate tumor destruction by polymorphonuclear leukocytes and macrophages via a “paraptosis”-induced pathway that promotes systemic immunity against intracranial T9 gliomas

Cloned T9-C2 glioma cells transfected with membrane macrophage colony-stimulating factor (mM-CSF) never formed subcutaneous tumors when implanted into Fischer rats, whereas control T9 cells did. The T9-C2 cells were completely killed within 1 day through a mechanism that resembled paraptosis. Vacuolization of the T9-C2 cell's mitochondria and endoplasmic reticulum started within 4 hours after implantation. By 24 hours, the dead tumor cells were swollen and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL)-positive. Bcl2-transduced T9-C2 cells failed to form tumors in rats. Both T9 and T9-C2 cells produced cytokine-induced neutrophil chemoattractant that recruited the granulocytes into the tumor injection sites, where they interacted with the tumor cells. Freshly isolated macrophages killed the T9-C2 cells in vitro by a mechanism independent of phagocytosis. Nude athymic rats treated with antiasialo GM1 antibody formed T9-C2 tumors, whereas rats treated with a natural killer cell (NK)-specific antibody failed to form tumors. When treated with antipolymorphonuclear leukocyte (anti-PMN) and antimacrophage antibodies, 80% of nude rats formed tumors, whereas only 40% of the rats developed a tumor when a single antibody was used. This suggests that both PMNs and macrophages are involved in the killing of T9-C2 tumor cells. Immunocompetent rats that rejected the living T9-C2 cells were immune to the intracranial rechallenge with T9 cells. No vaccinating effect occurred if the T9-C2 cells were freeze-thawed, x-irradiated, or treated with mitomycin-C prior to injection. Optimal tumor immunization using mM-CSF-transduced T9 cells requires viable tumor cells. In this study optimal tumor immunization occurred when a strong inflammatory response at the injection of the tumor cells was induced.

Natural killer cells contribute to the lethality of a murine model of Escherichia coli infection

Background. Cooperative interactions between natural killer (NK) cells and macrophages occur normally during the course of the early immune response to bacterial, protozoal, and viral pathogens, with each cellular compartment providing the other with critical stimulatory factors. We conducted the present study to determine whether NK cells contribute to the dysregulated immune response that accompanies septic shock. Methods. An analysis of the lethality of Escherichia coli CP9 was conducted in mice that had been depleted of NK cells via the injection of an anti-asialo GM1 antibody and in CD ϵ transgenic mice that are deficient in both NK cells and T cells. The 2 groups of mice were analyzed for serum levels of interferon-γ, tumor necrosis factor-α, and interleukin-1β as well as activation of NFκB and STAT1, 2 proinflammatory transcription factors. Results. NK cell-depleted and NK cell-deficient mice exhibited 80% survival in the face of an intraperitoneal bacterial challenge, whereas control mice all died within 12 hours. Serum levels of proinflammatory cytokines were markedly reduced in NK-depleted mice. NF κB and STAT1 activation were also reduced. NK-depleted mice exhibited less inflammation within multiple organs on histologic analysis. Conclusions. These results show that NK cells may contribute to the lethality of bacterial infections via effects on cytokine production. (Surgery 2002;132:205-12.)

Augmentation of local antitumor immunity in liver by interleukin-2 gene transfer via portal vein.

Metastasis to the liver remains an important problem in the treatment of patients with gastrointestinal cancer. We examined the mechanism and effect on liver metastasis of in vivo interleukin-2 (IL-2) gene transfer to the liver. RCN-9 cells derived from F344 rat colon adenocarcinoma were injected into syngeneic rats via the ileocecal vein to induce liver tumors. A total of 2.5x10(9) pfu of adenovirus vector harboring the human IL-2 gene (AdCMVhIL-2), or 2.5x10(9) pfu of control vector encoding beta-galactosidase was administered before RCN-9 cell challenge. On day 14, mean tumor weight was 4.0+/-2.4 g in the control group, whereas IL-2-transduced livers had no tumors. Survival of AdCMVhIL-2-treated rats was significantly longer than that of control rats (P<.01). Flow cytometry demonstrated that the proportion of natural killer (NK) cells had increased among sinusoidal cells collected from IL-2-transduced livers. These cells were highly cytotoxic to RCN-9 cells in vitro in the presence of a physiological high concentration of recombinant IL-2. Preventative effects of IL-2 transduction of the liver against liver metastasis were lost after depletion of NK cells by treatment with anti-asialo GM1 antibodies. Our results indicate that IL-2 gene transfer to the liver prevents liver metastasis by continuously providing physiological high concentrations of IL-2 in the liver, thereby activating sinusoidal NK cells.

Significant antitumor effects obtained by autologous tumor cell vaccine engineered to secrete interleukin (IL)-12 and IL-18 by means of the EBV/lipoplex.

The EBV/lipoplex is a nonviral gene delivery system composed of a cationic lipid and Epstein-Barr virus (EBV)-based plasmid vector that carries the EBV oriP and EBV nuclear antigen 1 (EBNA1) gene. Because the EBNA1 supports retention, nuclear localization, and transcriptional upregulation of the oriP-bearing plasmid, cells transfected with the EBV/lipoplex express the transgene at a very high level. We hypothesized that tumor cells genetically manipulated with the EBV/lipoplex may be used as a tumor vaccine without drug selection, strongly contributing to immunotherapy of patients with malignancies. The cytokines interleukin (IL)-12 and IL-18 exert a variety of immune-regulatory functions including interferon (IFN)-gamma production and cytotoxic T lymphocyte (CTL) and natural killer (NK) activation. Here, we investigated the possible therapeutic effects of an autologous tumor cell vaccine in the B16 melanoma model. The vaccine was engineered to secrete IL-12 and IL-18 by means of the EBV/lipoplex. B16 cells were subcutaneously implanted into syngenic mice followed by repetitive immunization with irradiated B16 cells that had been transfected 3 days earlier by TFL2-3, a novel cationic lipid, with EBV-plasmid vectors encoding IL-12 and/or IL-18 genes (B16/mIL-12, B16/mIL-18, and B16/mIL-12+mIL-18). The mice vaccinated with B16/mIL-12 underwent strong tumor suppression accompanied by a high IFN-gamma production. Both CTL and NK activities were significantly elevated in these mice. When the tumor cell vaccine was prepared by means of conventional (non-EBV) plasmid vectors combined with the same cationic lipid, the therapeutic outcome was not as good, suggesting the superiority of the EBV-based plasmid in engineering these types of tumor vaccines. Vaccination with B16/mIL-18 was not effective in suppressing tumors, whereas B16/mIL-12+mIL-18 showed comparable antitumor therapeutic validity as B16/mIL-12 did. When IFN-gamma mutant (IFN-gamma(-/-) mice were treated, B16/mIL-12 vaccine did not show any therapeutic activity, suggesting the necessity of IFN-gamma in the anti-melanoma immune responses. In contrast, the antitumor effect was not affected by NK depletion in mice that received repetitive injections with anti-asialo GM1 antibody. Furthermore, vaccination with B16/mIL-12 significantly suppressed pulmonary metastases in mice that had been intravenously injected with parental B16. Our results suggest that the EBV/lipoplex is quite useful in generating an autologous tumor cell vaccine and that IL-12 is an important component of the vaccine.

Suppression of splenic macrophage Candida albicans phagocytosis following in vivo depletion of natural killer cells in immunocompetent BALB/c mice and T-cell-deficient nude mice.

The resistance of mice to systemic infections caused by Candida albicans is associated with activated splenic macrophages. In addition, there is a correlation between natural killer (NK) cell activation and the resistance to systemic candidiasis. The present study was designed to clarify the role of NK cells in the control of splenic macrophage C. albicans phagocytosis by either depleting NK cells (anti-asialo GM(1) treatment) or maintaining them in an activated state (tilorone treatment) in both immunocompetent BALB/c mice and T-cell-deficient nude mice. The results of the in vitro phagocytosis assays were analyzed by flow cytometry and demonstrate the pivotal role of NK cells in controlling the capacity of splenic macrophages to phagocytose C. albicans. In summary, these data provide evidence that the NK cells are the main inducers of phagocytic activity of splenic macrophages and that they mediate the protection against C. albicans systemic infection.

Suppression of splenic macrophage Candida albicans phagocytosis following in vivo depletion of natural killer cells in immunocompetent BALB/c mice and T-cell-deficient nude mice

The resistance of mice to systemic infections caused by Candida albicans is associated with activated splenic macrophages. In addition, there is a correlation between natural killer (NK) cell activation and the resistance to systemic candidiasis. The present study was designed to clarify the role of NK cells in the control of splenic macrophage C. albicans phagocytosis by either depleting NK cells (anti-asialo GM 1 treatment) or maintaining them in an activated state (tilorone treatment) in both immunocompetent BALB/c mice and T-cell-deficient nude mice. The results of the in vitro phagocytosis assays were analyzed by flow cytometry and demonstrate the pivotal role of NK cells in controlling the capacity of splenic macrophages to phagocytose C. albicans. In summary, these data provide evidence that the NK cells are the main inducers of phagocytic activity of splenic macrophages and that they mediate the protection against C. albicans systemic infection.

Analysis of experimental liver metastasis from tumors inoculated in the mouse stomach cavity.

This study was conducted to develop a patient-like hematogenous metastatic model of gastric-cancer in order to gain an understanding of the tumor biology and to search for new methods of treatment. We established a natural and easily reproducible liver metastasis model by orthotopic gastric inoculation in Balb/c mice, using the syngeneic tumor, colon 26. This model allowed us to evaluate the effect of partial gastric resection with excision of tumor nodules on the formation of experimental liver metastases from the stomach cavity. Mice given partial gastrectomy showed less metastatic ability than control mice. In these experimental groups, liver metastasis was observed in the only group of mice that died of local tumor regrowth due to incomplete resection of the primary tumor. It is suggested that a period of at least 10 days is required for the formation of liver metastases after tumor inoculation into the stomach cavity. There was no significant increase in the number of liver metastases following splenectomy, or after the administration of anti-asialo GM1 antibody or silica. This experimental model of liver metastases will provide a useful means of understanding tumor biology and the regulation of liver metastases by host immunocompetent cells, and for assessing new therapeutic agents.

Prevention of growth and metastasis of murine melanoma through enhanced natural-killer cytotoxicity by fatty acid-conjugate of protopanaxatriol.

Ginsenosides, the glycosides of Panax ginseng, are metabolized (deglycosylated) by intestinal bacteria after oral administration. 20(S)-Protopanaxatriol (M4) is the main bacterial metabolite of protopanaxatriol-type ginsenosides and mediates their antitumor effects. To clarify the mechanism of the M4-mediated antitumor effect, the antitumor activity and metabolism of M4 was examined, using the C57BL/6 mice implanted with B16-BL6 melanoma. The chronic oral administration of M4 inhibited the growth of B16-BL6 melanoma at the implanted site. Analyses using TLC, HPLC, MS and NMR suggest that orally administered M4 was absorbed from the small intestine into the mesenteric lymphatics followed by the rapid esterification of M4 with fatty acids and its accumulation in the tissues including the liver and lung. The administration of M4 prior to the intravenous injection of B16-BL6 cells abrogated the enhanced lung metastasis in the mice pretreated with 2-chloroadenosine more effectively than in those pretreated with anti-asialo GM1. The esterified M4 (EM4) did not directly affect tumor growth in vitro, whereas it stimulated splenic NK cells to become cytotoxic to tumor cells. These results indicate that the antitumor activity of M4 is based on the NK cell-mediated tumor lysis enhanced by EM4.

Correlation of Suppressed Natural Killer Cell Activity with Altered Host Resistance Models in B6C3F1 Mice

A number of methods have been developed to assess the impact of a xenobiotic on the various components of the immune system. For risk analysis, it is necessary to determine what degree of chemically induced immune perturbation translates into altered host resistance. Natural killer (NK) cells play a pivotal role in the innate immune system with the ability to lyse cells infected with intracellular pathogens and certain tumors without previous exposure to the antigen. Spontaneous NK activity in B6C3F1 mice could be incrementally and consistently decreased by 20 to ≥80% by the intravenous administration of a range of dilutions of anti-asialo GM1 (AAGM1) antibody. The decrease in spontaneous NK activity following a single iv administration of AAGM1 antibody persisted for up to approximately 3 weeks when the initial suppression (e.g., 24 h after AAGM1 antibody injection) was almost 100%. Treatment with AAGM1, however, did not appear to perturb the function of other immune cells, based on results of the plaque assay, the mixed lymphocyte response, the cytotoxic T lymphocyte assay, the reticuloendothelial system clearance of sRBC assay, and the Streptococcus pneumoniae host resistance assay. Following a ≥80% decrease in spontaneous NK activity in mice, challenge with ≥1 × 103 B16F10 melanoma cells resulted in an increase in tumor burden based on the number of lung nodules. However, following challenge with 1 × 105 melanoma cells, a significant increase in tumor burden in mice was not observed until spontaneous NK activity had been decreased by ≥50–60%. Altered host resistance is a function not only of the magnitude of the decrease in NK activity but also of the magnitude of the challenge to the host.