In vivo generation of lymphokine activated killer cell activity by ABPP and interleukin-2 and their antitumor effects against immunogenic and nonimmunogenic tumors in murine tumor models

Summary The capacity of the interferon inducer ABPP and recombinant interleukin-2 (IL-2) to generate lymphokine activated killer (LAK) cell activity in vivo was examined and compared to the cytolysis of fresh tumor cells by in vitro generated LAK cells. Various tumors differing in histology and immunogenicity were used in in vitro and in vivo experiments. The i.p. administration of ABPP or IL-2 generated much higher levels of LAK cell activity in the peritoneal exudate than in the spleen. Administration of 2 injections of ABPP was as effective as a 3-day course of moderate doses of IL-2. Generation of LAK cell activity by IL-2 was dose dependent. ABPP had significant antitumor activity in vivo in both the i.p. tumor model and the pulmonary metastasis model when administered early (24–48 h after tumor inoculation), but was ineffective against established (day 3) tumor or advanced grossly visible i.p. (day 8) tumor. Treatment of established tumor with IL-2 and LAK cells was not more effective when ABPP was given concurrently. In contrast when ABPP preceded IL-2 and LAK treatment an additional antitumor effect was seen. Immunogenic tumors were more sensitive to treatment with ABPP than nonimmunogenic tumors. Only a marginal difference in lysability in vitro existed. The antitumor effects of ABPP in vivo may therefore be mediated by mechanisms other than cytolysis by activated killer cells alone. These data taken together suggest that ABPP and IL-2 induce discernable levels of LAK cell activity, but do not synergize when combined     

Effects of the interferon-inducer ABPP on colon cancer in rats; importance of tumor load and tumor site

Summary ABPP (2-amino-5-bromo-6-phenyl-4-pyrimidinone) is a pyrimidinone with known interferon-inducing, natural killer (NK) cell activity enhancing, antiviral and antitumor properties in several animal species. Its effect on CC531, a dimethylhydrazine-induced, transplantable, weakly immunogenic adenocarcinoma of the colon in WAG rats, was studied. ABPP was found to have no direct cytotoxic effect on CC531 cells in vitro. When small cubes of tumor of equal weight were implanted under the renal capsule, administration of 250 mg/kg of ABPP i. p. on day 0 and +1 led repeatedly to significant (p<0.02 up to p<0.001) inhibition of tumor growth, when measured on day +7. Lower doses or a single dose of ABPP did not achieve this effect. Late administration (on day +6 and +7) of 250 mg/kg of ABPP in this model was found to have no effect on tumor growth when measured on day +13. When 5×10⁵ tumor cells were injected in the portal vein, administration of 250 mg/kg of ABPP i.p. on day 0 and +1 reduced significantly (p=0.002) the number of liver metastases, when counted on day +30. Survival in this group was significantly prolonged (p<0.01). However when ABPP was given on day +6 and +7, significantly more (p<0.02) metastases in the liver were counted on day +30. The results show a significant antitumor effect of ABPP against tumor CC531 in the subrenal capsule assay (SRCA) model as well as in the liver metastasis model when administered at the time of tumor inoculation. Late administration of ABPP did not inhibit tumor growth in the SRCA and significantly enhanced the development of liver metastases. The role of timing, tumor site, and the mechanisms by which this dual outcome of immunotherapy with ABPP is mediated are discussed. The results of these experiments may have important implications for the design of clinical studies with ABPP.This study was supported in part by a grant from The Upjohn Company, Kalamazoo, Michigan, USA     

Generation of tumor-specific cytotoxic T lymphocytesin vivo by combined treatment with inactivated tumor cells and recombinant interleukin-2

In order to search for a new therapy that would maximize the effect of interleukin-2 (IL-2) in evoking antitumor immunity in vivo, the therapeutic effect of a combination of mitomycin-C(MMC)-treated tumor cells and recombinant IL-2 was examined for its induction of antitumor activity against established melanoma metastasis. In C57BL/6 mice intravenously (i. v.) injected with B16 melanoma cells on day 0, the combined treatment with an intraperitoneal (i. p.) injection of MMC-treated melanoma cells on day 6 and 2500 U rIL-2 (twice daily) on days 7 and 8 markedly reduced the number of pulmonary metastases. This antitumor activity was more effective than that in untreated controls and mice that were injected with MMC-treated melanoma cells alone or rIL-2 alone. When the i. p. injection of MMC-treated tumor cells was replaced by other syngeneic tumor cells, antitumor activity against metastatic melanoma was not induced. The antitumor activity induced by this treatment increased in parallel with an increase in the dose of rIL-2 injected. In contrast, an i. p. injection of soluble tumor-specific antigens alone could induce only a marginal level of antitumor activity, and this activity was not augmented by subsequent i. p. injections of rIL-2. In vivo treatment with anti-CD8 monoclonal antibody (mAb), but not with anti-CD4 mAb or anti-asialo-GM1 antibody, abrogated the antitumor activity induced by this combined therapy. This suggests that the antitumor effect was dependent on CD8⁺ T cells. Lung-infiltrating lymphocytes from mice that had been i. v. injected with melanoma cells 11 days before and were treated with this combined therapy, showed melanoma-specific cytolytic activity. This combined therapy also showed significant antitumor activity against subcutaneously inoculated melanoma cells. These results demonstrate that the combined therapy of an i. p. injection of MMC-treated tumor cells and subsequent and consecutive i. p. administration of rIL-2 increases antitumor activity against established metastatic melanoma by generating tumor-specific CD8⁺ CTL in vivo.     

Interleukin 21 therapy increases the density of tumor infiltrating CD8<Superscript>+ </Superscript>T cells and inhibits the growth of syngeneic tumors

Interleukin (IL)-21 is a recently discovered cytokine in early clinical development, which has shown anti-tumor activity in various animal models. In the present study, we examine the anti-tumor activity of IL-21 protein therapy in two syngeneic tumor models and its effect on the density of tumor infiltrating T cells. We treated mice bearing established subcutaneous B16 melanomas or RenCa renal cell carcinomas with intraperitoneal (i.p.) or subcutaneous (s.c.) IL-21 protein therapy and subsequently scored the densities of tumor infiltrating CD4⁺ and CD8⁺ T cells by immunohistochemistry. Whereas both routes of IL-21 administration significantly inhibited growth of small, established RenCa and B16 tumors, only s.c. therapy significantly inhibited the growth of large, established tumors. We found a greater bioavailability and significant drainage of IL-21 to regional lymph nodes following s.c. administration, which could account for the apparent increase in anti-tumor activity. Specific depletion of CD8⁺ T cells with monoclonal antibodies completely abrogated the anti-tumor activity, whereas NK1.1⁺ cell depletion did not affect tumor growth. In accordance, both routes of IL-21 administration significantly increased the density of tumor infiltrating CD8⁺ T cells in both B16 and RenCa tumors; and in the RenCa model s.c. administration of IL-21 led to a significantly higher density of tumor infiltrating CD8⁺ T cells compared to i.p. administration. The densities of CD4⁺ T cells were unchanged following IL-21 treatments. Taken together, these data demonstrate that IL-21 protein has anti-tumor activity in established syngeneic tumors, and we show that IL-21 therapy markedly increases the density of tumor infiltrating CD8⁺ T cells.     

Antitumor effect of the streptococcal preparation OK-432 in a murine model of ovarian cancer

Summary The antitumor effects of the streptococcal preparation OK-432 were analyzed in a murine ovarian teratocarcinoma (MOT) model. Administration of OK-432 i.p. prevented tumor outgrowth in 75% of mice challenged with 10³ MOT cells i.p. 24 h previously. Treatment was less successful in mice challenged with 10⁴ or 10⁵ cells, preventing tumor growth in 25% of the former and only 5% of the latter group. Tumor-challenged mice cured by injections of OK-432 were not rendered resistant to a subsequent challenge with 10³ MOT cells 75 days after initial treatment. Only the i.p. route of administration was effective as i.v. OK-432 did not prolong survival of tumor-challenged mice. An antitumor response was detected as early as 24 h after i.p. treatment. This correlated temporally with an influx of neutrophils into the peritoneal cavity. Peritoneal cells obtained between 6 and 24 h after treatment were capable of lysing MOT targets in vitro. A single cell cytotoxicity assay demonstrated that peritoneal neutrophils, elicited by i.p. injection of OK-432, could bind to and lyse MOT targets. These data indicate that OK-432 is effective against small tumor cell inocula in this murine model of ovarian cancer and, furthermore, that the neutrophilic response into the peritoneal cavity plays a role in tumor rejection.     

Targeting AURKA in treatment of peritoneal tumor dissemination in gastrointestinal cancer

Intraperitoneal (i.p.) tumor dissemination and the consequent malignant ascites remain unpredictable and incurable in patients with gastrointestinal (GI) cancer, and practical advances in diagnosis and treatment are urgently needed in the clinical settings. Here, we explored tumor biological and immunological mechanisms underlying the i.p. tumor progression for establishing more effective treatments.We established mouse tumor ascites models that murine and human colorectal cancer cells were both i.p. and subcutaneously (s.c.) implanted in mice, and analyzed peritoneal exudate cells (PECs) obtained from the mice. We then evaluated anti-tumor efficacy of agents targeting the identified molecular mechanisms using the ascites models. Furthermore, we validated the clinical relevancy of the findings using peritoneal lavage fluids obtained from gastric cancer patients.I.p. tumor cells were giant with large nuclei, and highly express AURKA, but less phosphorylated TP53, as compared to s.c. tumor cells, suggesting polyploidy-like cells. The i.p. tumors impaired phagocytic activity and the consequent T-cell stimulatory activity of CD11b⁺Gr1⁺PD1⁺ myeloid cells by GDF15 that is regulated by AURKA, leading to treatment resistance. Blocking AURKA with MLN8237 or siRNAs, however, abrogated the adverse events, and induced potent anti-tumor immunity in the ascites models. This treatment synergized with anti-PD1 therapy. The CD11b⁺PD1⁺ TAMs are also markedly expanded in the PECs of gastric cancer patients.These suggest AURKA is a determinant of treatment resistance of the i.p. tumors. Targeting the AURKA-GDF15 axis could be a promising strategy for improving clinical outcome in the treatment of GI cancer.     

Intravenous Administration of Achyranthes Bidentata Polypeptides Supports Recovery from Experimental Ischemic Stroke in Vivo

Background

Achyranthes bidentata Blume (A. bidentata) is a commonly prescribed Chinese medicinal herb. A. bidentata polypeptides (ABPP) is an active composite constituent, separated from the aqueous extract of A. bidentata. Our previous studies have found that ABPP have the neuroprotective function in vitro and in rat middle cerebral artery occlusion (MCAO) model in attenuating the brain infract area induced by focal ischemia-reperfusion. However, the ultimate goal of the stroke treatment is the restoration of behavioral function. Identifying behavioral deficits and therapeutic treatments in animal models of ischemic stroke is essential for potential translational applications.

Methodology and Principal Findings

The effect of ABPP on motor, sensory, and cognitive function in an ischemic stroke model with MCAO was investigated up to day 30. The function recovery monitored by the neurological deficit score, grip test, body asymmetry, beam-balancing task, and the Morris Water Maze. In this study, systemic administration of ABPP by i.v after MCAO decreased the neurological deficit score, ameliorated the forepaw muscle strength, and diminished the motor and sensory asymmetry on 7^th and 30^th day after MCAO. MCAO has been observed to cause prolonged disturbance of spatial learning and memory in rats using the MWM, and ABPP treatment could improve the spatial learning and memory function, which is impaired by MCAO in rats, on 30^th day after MCAO. Then, the viable cells in CA1 region of hippocampus were counted by Nissl staining, and the neuronal cell death were significantly suppressed in the ABPP treated group.

Conclusion

ABPP could improve the recovery of sensory, motor and coordination, and cognitive function in MCAO-induced ischemic rats. And this recovery had a good correlation to the less of neuronal injury in brain.     

An extract of seeds fromAeginetia indica L., a parasitic plant,induces potent antigen-specific antitumor immunity in Meth A-bearing BALB/c mice

Summary The antitumor activity of an extract of seeds fromAeginetia indica L., a parasitic plant, was investigated. BALB/c mice, inoculated i.p. 1 × 10⁵ syngeneic Meth A tumor cells, were administered 2.5 mg/kgA. indica extract i.p. every 2 days from day 0. The untreated mice died of an ascitic form of tumor growth within 21 days, whereas all the treated mice completely recovered from tumor challenge without any side-effects. The extract did not exert direct cytotoxic activity against Meth A in vitro. Mice that survived after the first challenge as a result ofA. indica treatment overcame the rechallenge with homologous Meth A without additional administration of the extract. On the other hand, those mice could not survive after rechallenge with Meth 1 tumor cells, which were also established in BALB/c mice but were different in antigenicity from Meth A, suggesting the development of antigen-specific concomitant immunity in theA. indica-cured mice. In the induction phase of antitumor resistance in this system, CD4⁺ T cells appeared to be the main contributors, since in vivo administration of anti-CD4 mAb completely abolished such resistance. In contrast, anti-CD8 mAb administration did not influence the effect ofA. indica. The importance of CD4⁺ T cells in antitumor immunity was again clarified by Winn assay; that is, spleen and lymph node cells depleted of CD4⁺ T cells in vitro prior to assay abolished antitumor activity on co-grafted Meth A tumor cells in vivo.     

Inhibition and eradication of human glioma with tumor-targeting Salmonella typhimurium in an orthotopic nude-mouse model

Malignant glioma tumors are the most common primary central nervous system tumors. Despite the multidisciplinary approach to treatment, prognosis remains poor. In this study, we demonstrated that the Salmonella typhimurium A1-R tumor-targeting strain can inhibit and eradicate human glioma in an orthotopic nude-mouse model. S. typhimurium A1-R was administered by injection through a craniotomy open-window or intravenously in nude mice. To establish the model, 2 x 105 U87-RFP human glioma cells were injected stereotactically into the mouse brain through the craniotomy open window. Two weeks after glioma-cell implantation, mice were treated with S. typhimurium A1-R [2 x 10⁷ CFU/200 μl intravenous injection (i.v.) or 1 x 10⁶ CFU/1 μl intracranial injection (i.c.)] once a week for 3 weeks. Brain tumors were observed by fluorescence imaging through the craniotomy open window over time. S. typhimurium A1-R, administered i.c., inhibited brain tumor growth 7.6-fold compared with untreated mice (p = 0.009) and improved survival 73% (p = 0.001). Two of ten mice appeared to have their tumors eradicated. Intravenous administration of S. typhimurium A1-R was not effective. The craniotomy open window enabled observation of tumor growth in the brain in real time in both treated and untreated mice. The results of the present study demonstrate that bacterial therapy of brain cancer is a novel, effective and safe treatment strategy in a highly treatment-resistance cancer.     

Therapeutic effect of intratumoral administration of DCs with conditional expression of combination of different cytokines

In this study, we tested the effect of intratumoral administration of dendritic cells (DCs) with inducible expression of different cytokines, using the novel Rheoswitch Therapeutic System on the experimental models of renal cell cancer (RENCA) and MethA sarcoma. Intratumoral injection of DCs, engineered to express IL-12, IL-21, or IFN-α, showed potent therapeutic effect against established tumor. This effect was associated with the induction of potent tumor antigen-specific CD8⁺ T-cell responses, as well as the infiltration of tumors with CD4⁺ and CD8⁺ T cells but not with the cytotoxic activity of DCs. Combination of i.t. administration of DCs, producing different cytokines, did not enhance the antitumor effect of therapy with single cytokine. These results indicate that RTS can be a potent tool for conditional topical cytokine delivery, in combination with DC administration. However, combination of different cytokines may not necessarily improve the outcome of treatment.     

Effect of systemic administration of mouse recombinant interferon-gamma on the lung tumor metastases in mice

The purpose of this study was to examine the effective anti-metastatic activity by multiple i.v. administrations of mouse recombinant interferon-gamma (IFN-gamma) against pulmonary metastases of 3LL or B16-BL6 melanoma cells after surgical excision of primary tumors. Multiple treatments with IFN-gamma reduced effectively the incidence of pulmonary tumor metastases. Repeated 4 consecutive treatment modalities with IFN-gamma showed remarkable reduction of lung tumor colonies, and also rendered alveolar macrophages (AM) cytotoxic against B16-BL6 cells. In contrast, 14 consecutive administrations of IFN-gamma at any doses (10(2) and 10(3) U/mouse) could not activate macrophages to become cytotoxic, but were effective in regressing metastases. Thus, antimetastatic activity of IFN-gamma may be due to the stimulation of host immune defense systems such as induction of tumoricidal macrophages, presumably the direct antiproliferative action to tumor cells, or both actions under the appropriate administration conditions. We found that the systemic administration of IFN-gamma under appropriate multiple treatment modalities results in the reduction of the lung metastases and can activate AM to become tumor cytotoxic at relatively low doses (10(2) U). High-dose IFN-gamma in the multiple administration schedule was also effective for the reduction of lung tumor colonies, but strongly suppressed the nonspecific immune function and could not activate tumoricidal properties of AM.     

Intra-arterial administration of tumor-targeting Salmonella typhimurium A1-R regresses a cisplatin-resistant relapsed osteosarcoma in a patient-derived orthotopic xenograft (PDOX) mouse model

Previously, a patient-derived orthotopic xenograft (PDOX) model was established with a lung metastasis from an osteosarcoma patient which developed after adjuvant cisplatinum (CDDP) treatment. In this model, we previously demonstrated the efficacy of trabectedin (TRAB) and temozolomide (TEM) compared with CDDP. In the present report, osteosarcoma tissue was implanted orthotopically in the distal femur of mice which were randomized into the following groups when tumor volume reached approximately 100 mm³; On day 14 after initiation of treatment, all but CDDP significantly inhibited tumor volume growth compared with untreated controls. Control (G1): 793.7 ± 215.0 mm³; CDDP (G2): 588.1 ± 176.9 mm³; Salmonella typhimurium A1-R (S. typhimurium A1-R) intravenous (i.v.) (G3): 269.7 ± 72.7 mm³; S. typhimurium A1-R intra-arterial (i.a.) (G4): 70.2 ± 18.9 mm³ (CDDP: p = 0.056; S. typhimurium A1-R i.v.: p = 0.0001; S. typhimurium A1-R i.a.: p = 0.00003, all vs. untreated controls). i.a. administration of S. typhimurium A1-R was significantly more effective than either CDDP (p = 0.00007), or i.v. administration of S. typhimurium A1-R (p = 0.00007) and significantly regressed the tumor volume compared with day 0 (p = 0.001). The new model of i.a. administration of S. typhimurium A1-R has great promise for the treatment of recalcitrant osteosarcoma.     

Migration of iron-labeled KHYG-1 natural killer cells to subcutaneous tumors in nude mice, as detected by magnetic resonance imaging

Background aimsA novel cell line of cytotoxic natural killer (NK) cells, KHYG-1, was examined in vivo for immunotherapy against prostate cancer. The feasibility of using magnetic resonance imaging (MRI) tracking to monitor the fate of injected NK cells following intravenous (i.v.), intraperitoneal (i.p.) and subcutaneous (s.c.) administration was assessed.MethodsPC-3M human prostate cancer cells were injected s.c. into the flank of nude mice (day 0). KHYG-1 NK cells were labeled with an iron oxide contrast agent and injected s.c., i.v. or i.p. on day 8. Mice were imaged by MRI on days 7, 9 and 12. Tumor sections were examined with fluorescence microscopy and immunohistologic staining for NK cells.ResultsNK cells were detected in the tumors by histology after all three administration routes. NK cells and fluorescence from the iron label were co-localized. Signal loss was seen in the areas around the tumors and between the tumor lobes in the s.c. group.ConclusionsWe are the first to label this cell line of NK cells with an iron oxide contrast agent. Accumulation of NK cells was visualized by MRI after s.c. injection but not after i.v. and i.p. injection.     

Tumor specific phage particles promote tumor regression in a mouse melanoma model

Within cancer research, phage display libraries have been widely used for the identification of tumor targeting peptides and antibodies. Additionally, phages are known to be highly immunogenic; therefore we evaluated the immunotherapeutic potential of tumor specific phages to treat established solid tumors in a mouse model of melanoma. We developed two tumor specific phages, one derived from a peptide phage display library and one Fab expressing phage with known specificity, for the treatment of mice bearing palpable B16-F10 or B16/A2K^b tumors. Therapy in B16-F10 tumor bearing mice with tumor specific phages was superior to treatment with non-tumor specific phages and lead to delayed tumor growth and increased survival. In B16/A2K^b tumor bearing mice, therapy with tumor specific phages resulted in complete tumor regression and long-term survival in 50% of the mice. Histological analysis of tumors undergoing treatment with tumor specific phages revealed that phage administration induced a massive infiltration of polymorphonuclear neutrophils. Furthermore, phages induced secretion of IL-12 (p70) and IFN-γ as measured in mouse splenocyte culture supernatants. These results demonstrate a novel, immunotherapeutic cancer treatment showing that tumor specific phages can promote regression of established tumors by recruitment of inflammatory cells and induction of Th1 cytokines.     

The use of immunologically competent cells from pig mesenteric lymph nodes to treat pulmonary tumors in mice

Summary Pulmonary tumors were produced in A strain mice by intravenous injection of 1×10⁶ A strain mammary carcinoma cells. The mice were killed on day 14, their lungs fixed in Bouin's fluid, and the number of tumors counted.The mesenteric lymph node chains of pigs were immunized by implantation of tissue into the mesentery. In all animals the middle segment of node chain was excised. The remaining segments of node proximal and distal to the resected segment were, in separate pigs, nonimmunized or immunized against mouse tumor, immunized against mouse tumor or mouse skin, or immunized against human tumor or mouse tumor. All segments of node chain were removed 7 days after immunization for preparation of cell suspensions.When tumor cells were combined in a ratio of 1 : 10 or 1 : 60 with mouse tumor-immune pig cells, there was a significant reduction in tumor formation compared to that in mice receiving tumor cells alone.Injection of mouse tumor-immune pig cells on day 7, to treat tumors inoculated on day 0, was ineffective. However, when the mice received, in addition, 200 rad thoracic irradiation on day 3, immune pig cells reduced the number of tumors compared to that in animals receiving irradiation alone, or irradiation and nonimmune pig cells.In further experiments, in order to increase the number of pig cells reaching the lungs, a splenectomy was performed on day 6, prior to intravenous injection of immune cells on day 7. A comparison was made of the antitumor effect of pig cells immunized against mouse tumor, mouse skin, or human tumor. Cells immunized against either mouse tissue were equally effective in reducing the number of tumors compared to the number in animals receiving tumor cells alone. However, cells immune to human tumor were ineffective.     

Augmentation of the therapeutic efficacy of adoptive tumor immunotherapy by in vivo administration of slowly released recombinant interleukin 2

Summary Immunization of C57BL/6 mice with MMC-treated syngeneic lymphoma cells, MBL-2, caused the generation of antitumor effector cells in vivo and the immunized mice permanently rejected viable MBL-2 lymphoma cells. Both plastic nonadherent T cells and plastic adherent MØ obtained from MBL-2 immunized mouse peritoneal exudate cells revealed strong cytotoxic activity against MBL-2 lymphoma cells, whereas immune spleen cells were not highly active against MBL-2 lymphoma cells in vitro. However, systemic adoptive transfer of immune spleen cells into the MBL-2-bearing mice by i.v. infusion in conjunction with i.p. cyclophosphamide (100 mg/kg) treatment cured the mice of tumor. This therapeutic efficacy of immune spleen cells was reflected by the number of transferred effector cells and over 5×10⁷ immune spleen cells were required to cure the mice completely. The cells mediating in vivo rejection of MBL-2 lymphoma cells were Thy 1.2⁺ T cells. This ACIT was specific against MBL-2 lymphoma cells and had no effect on the growth of other syngeneic tumors, B16 melanoma or BMC6A fibrosarcoma. In vivo administration of recombinant interleukin 2 (r-IL 2) combined with ACIT greatly modulated the cure rate of tumor-bearing mice. In addition, we found that slowly released r-IL 2 administratered from an ALZET miniosmotic pump was more effective in augmenting the therapeutic efficacy of immune spleen cells in ACIT than a single injection of the same total dose of r-IL 2.     

Inhibition and eradication of human glioma with tumor-targeting Salmonella typhimurium in an orthotopic nude-mouse model

Malignant glioma tumors are the most common primary central nervous system tumors. Despite the multidisciplinary approach to treatment, prognosis remains poor. In this study, we demonstrated that the Salmonella typhimurium A1-R tumor-targeting strain can inhibit and eradicate human glioma in an orthotopic nude-mouse model. S. typhimurium A1-R was administered by injection through a craniotomy open-window or intravenously in nude mice. To establish the model, 2 × 10⁵ U87-RFP human glioma cells were injected stereotactically into the mouse brain through the craniotomy open window. Two weeks after glioma-cell implantation, mice were treated with S. typhimurium A1-R [2 × 10⁷ CFU/200 µl intravenous injection (i.v.) or 1 × 10⁶ CFU/1 µl intracranial injection (i.c.)] once a week for 3 weeks. Brain tumors were observed by fluorescence imaging through the craniotomy open window over time. S. typhimurium A1-R, administered i.c., inhibited brain tumor growth 7.6-fold compared with untreated mice (p = 0.009) and improved survival 73% (p = 0.001). Two of ten mice appeared to have their tumors eradicated. Intravenous administration of S. typhimurium A1-R was not effective. The craniotomy open window enabled observation of tumor growth in the brain in real time in both treated and untreated mice. The results of the present study demonstrate that bacterial therapy of brain cancer is a novel, effective and safe treatment strategy in a highly treatment-resistance cancer.Key words: Salmonella typhimurium A1-R, fluorescent proteins, brain cancer, mouse model, in vivo imaging     

Enhanced tumor susceptibility of immunocompetent mice infected with lymphocytic choriomeningitis virus

Summary Mice infected i.v. with high doses of lymphocytic choriomeningitis virus (LCMV; 10⁵–10⁶ plaqueforming units) 8–10 days prior to challenge with the methylcholanthrene-induced fibrosarcoma tumor cell line MC57G or the melanoma cell line B16 tumor cells showed an enhanced tumor susceptibility with respect to both growth kinetics of the tumor and the minimal dose necessary for tumor take. After transient initial growth, MC57G tumor cells were all rejected by uninfected C57BL/6 mice by day 14. Mice preinfected i.v. with LCMV 3 weeks before or at the time of tumor challenge, but not those infected 2 months before or 7 days after, showed increasing tumor growth, the tumor take being 100% for 10⁶, 50% for 10⁵ and 37% for 10⁴ MC57G tumor cells injected into the footpad compared with resistance to 10⁶ cells in normal mice. B16 melanoma cells also grew more rapidly in LCMV-preinfected mice and by day 40 tumors were established with about 100 times fewer cells, i.e. about 10³ compared with 3×10⁴–3×10⁵ for uninfected mice. Analysis of the growth of tumor cells in normal and in LCMV-carrier mice revealed that the latter mice were not more susceptible to LCMV-infected than to uninfected MC57G. Since LCMV-carrier mice fail to mount LCMV-specific T cell responses, these results suggest that anti-LCMV-specific T cells may be responsible for acquired immunodeficiency hampering immune surveillance against the tumors studied.Supported by grants from the Swiss National Science Foundation 3.259–0.87 and the Kanton of Zürich     

Improved therapeutic effects of interleukin 2 after the accumulation of lymphokine-activated killer cells in tumor tissue of mice previously treated with cyclophosphamide

Summary We investigated the combined effects of human recombinant interleukin 2 (IL-2) and cyclophosphamide (CY) on s.c. transplanted 3LL lung carcinoma in C57BL/6 mice. A total of 95% of the tumors were competely cured when CY (150 mg/kg, i.v.) was given on day 5 (5 days after tumor implantation) and IL-2 (5×10⁴ Jurkat Units/day, i.p.) was then combined with it between day 6 and day 15. CY alone brought about the complete regression of tumors, although 60% of the mice died of local recurrence and pulmonary metastasis; IL-2 alone had no therapeutic effect. Satisfactory effects from the combination of CY and IL-2 were also obtained by 5 days administration of IL-2 between days 11 and 15, initiated 6 days after CY treatment, but not by that given before CY (days 1–5) or 1 day after CY (days 6–10). No therapeutic effects from IL-2 were observed when it was combined with other types of chemotherapy that showed not therapeutic effects by themselves. Nor were we able to observe any transplantation resistance to the rechallenge of 3LL tumor in cured mice. We particularly examined the lymphokine-activated killer (LAK) cells as we suspected that these were responsible for the development of active effector cells in the treated mice. LAK cell activity in fresh spleen cells was detected in mice treated with IL-2 alone but not in untreated mice nor in those treated with CY alone or CY plus IL-2. The number of LAK precursor cells in the spleen had increased on day 8 and on day 13 in untreated mice with 3LL, as compared with the incidence in normal mice, while the number of cells had decreased by day 18. On the other hand LAK precursor cells were suppressed on day 8 and tended to recover thereafter in CY-treated mice. Adoptively transferred LAK cells were found to accumulate in CY-treated tumors 2.5 times more densely than in untreated tumors. The preferential accumulation of LAK cells that had been activated systemically by the appropriately timed administration of IL-2 in tumor tissue was followed by the improved effects obtained by combined treatment with CY and IL-2.Supported in part by Grants-in-Aid for Cancer Research from the Japanese Ministry of Education, Science and Culture and from the Japanese Ministry of Health and Welfare     

Xenogeneic Human p53 DNA Vaccination by Electroporation Breaks Immune Tolerance to Control Murine Tumors Expressing Mouse p53

The pivotal role of p53 as a tumor suppressor protein is illustrated by the fact that this protein is found mutated in more than 50% of human cancers. In most cases, mutations in p53 greatly increase the otherwise short half-life of this protein in normal tissue and cause it to accumulate in the cytoplasm of tumors. The overexpression of mutated p53 in tumor cells makes p53 a potentially desirable target for the development of cancer immunotherapy. However, p53 protein represents an endogenous tumor-associated antigen (TAA). Immunization against a self-antigen is challenging because an antigen-specific immune response likely generates only low affinity antigen-specific CD8⁺ T-cells. This represents a bottleneck of tumor immunotherapy when targeting endogenous TAAs expressed by tumors. The objective of the current study is to develop a safe cancer immunotherapy using a naked DNA vaccine. The vaccine employs a xenogeneic p53 gene to break immune tolerance resulting in a potent therapeutic antitumor effect against tumors expressing mutated p53. Our study assessed the therapeutic antitumor effect after immunization with DNA encoding human p53 (hp53) or mouse p53 (mp53). Mice immunized with xenogeneic full length hp53 DNA plasmid intramuscularly followed by electroporation were protected against challenge with murine colon cancer MC38 while those immunized with mp53 DNA were not. In a therapeutic model, established MC38 tumors were also well controlled by treatment with hp53 DNA therapy in tumor bearing mice compared to mp53 DNA. Mice vaccinated with hp53 DNA plasmid also exhibited an increase in mp53-specific CD8⁺ T-cell precursors compared to vaccination with mp53 DNA. Antibody depletion experiments also demonstrated that CD8⁺ T-cells play crucial roles in the antitumor effects. This study showed intramuscular vaccination with xenogeneic p53 DNA vaccine followed by electroporation is capable of inducing potent antitumor effects against tumors expressing mutated p53 through CD8⁺ T cells.