Targeting Stat3 induces senescence in tumor cells and elicits prophylactic and therapeutic immune responses against breast cancer growth mediated by NK cells and CD4+ T cells

Aberrant Stat3 activation and signaling contribute to malignant transformation by promoting cell cycle progression, inhibiting apoptosis, and mediating tumor immune evasion. Stat3 inhibition in tumor cells induces the expression of chemokines and proinflammatory cytokines, so we proposed to apply Stat3-inhibited breast cancer cells as a source of immunogens to induce an antitumor immune response. Studies were performed in two murine breast cancer models in which Stat3 is activated: progestin-dependent C4HD cells and 4T1 cells. We immunized BALB/c mice with irradiated cancer cells previously transfected with a dominant-negative Stat3 vector (Stat3Y705F) in either a prophylactic or a therapeutic manner. Prophylactic administration of breast cancer cells transfected with Stat3Y705F (Stat3Y705F-breast cancer cells) inhibited primary tumor growth compared with administration of empty vector-transfected cells in both models. In the 4T1 model, 50% of the challenged mice were tumor free, and the incidence of metastasis decreased by 90%. In vivo assays of C4HD tumors showed that the antitumor immune response involves the participation of CD4(+) T cells and cytotoxic NK cells. Therapeutic immunization with Stat3Y705F-breast cancer cells inhibited tumor growth, promoted tumor cell differentiation, and decreased metastasis. Furthermore, inhibition of Stat3 activation in breast cancer cells induced cellular senescence, contributing to their immunogenic phenotype. In this work, we provide preclinical proof of concept that ablating Stat3 signaling in breast cancer cells results in an effective immunotherapy against breast cancer growth and metastasis. Moreover, our findings showing that Stat3 inactivation results in induction of a cellular senescence program disclose a potential mechanism for immunotherapy research.     

Expression of mouse mammary tumor virus superantigen accelerates tumorigenicity of myeloma cells

To investigate whether superantigen (SAG) from endogenous mouse mammary tumor virus functions as an immunogenic or a tumorigenic factor in tumor development, the BALB/c myeloma cell line FO was transfected with the SAG gene from the 3' Mtv-50 long terminal repeat (LTR) open reading frame (ORF), the product of which was specific for Vbeta6. All five transfectants expressing Mtv-50 LTR ORF mRNA showed stimulatory activity for Vbeta6 T-cell hybridomas in vitro; this activity was inhibited by the addition of anti-Mtv-7 monoclonal antibody (MAb) or anti-major histocompatibility complex class II I-A(d) and I-E(d) MAb. All transfectants with the SAG gene grew more rapidly than did mock transfectants in BALB/c mice after subcutaneous inoculation, whereas all clones, including mock transfectants, grew equally well in athymic nude mice. A significant fraction of Vbeta6 T cells selectively expressed activation markers, including CD44(high), CD62L(low), and CD69(high), and produced large amounts of interleukin 5 (IL-5) and IL-6 in BALB/c mice inoculated with transfectants. These results suggested that the expression of viral SAG enhances the tumorigenicity of a myeloma cell line through the stimulation of SAG-reactive T cells.     

H-40, an antigen controlled by an Igh-linked gene and recognized by cytotoxic T lymphocytes. II. Recognition of H-40 as a tumor antigen in leukemic animals

C.B-20 (Ighb) but not (C.B-20 X BALB/c)F1 mice reject BCL1, a sIg+ tumor that spontaneously arose in an Igh congenic BALB/c (Igha) mouse. C.B-20 immune T cells from mice immunized with either BCL1 or BALB/c splenocytes adoptively transfer tumor protection to sublethally irradiated C.B-20 but not BALB/c or (BALB/c X C.B-20)F1 mice. These data suggest that BALB/c and BCL1 share an antigen, which if present in the host prevents the immune cells from eradicating the tumor. The antigen is controlled by H-40, a gene that maps to the C end of the Igh complex, telomeric to Tsu and in the region of Pre-1. The ability of H-40 to act as a tumor antigen for other BALB/c tumors inoculated into C.B-20 hosts was investigated. H-40 did not elicit rejection of P1798 (T lymphoma), Meth A (fibrosarcoma), or MOPC-315 (alpha, lambda myeloma) tumor cells. C.B-20 mice that previously rejected BCL1, however, showed partial resistance to a low challenge dose of the MOPC-104E (mu, lambda myeloma) tumor. These data suggest that H-40 has a differential degree of expression on BALB/c tumor cells. The ability of the adoptively transferred cells to confer protection against BCL1 is abrogated by pretreatment of the cells with anti-Lyt-1 or anti-Lyt-2 antibodies. However, an admixture of anti-Lyt-1- and anti-Lyt-2-treated cells provided protection. These data, together with the results detected by cytotoxic T lymphocyte (CTL) activity in vitro, indicate that H-40 can serve as a target antigen for tumor rejection by CTL in allogeneic hosts. The implications of the results for allogeneic bone marrow transplantation into leukemic individuals who benefit from a graft vs leukemia effect are discussed.     

Tumor-specific idiotype vaccines. III. Induction of T helper cells by anti-idiotype and tumor cells

In a previous report, we have demonstrated the induction of tumor-specific immunity by monoclonal anti-idiotype antibodies generated against a monoclonal anti-tumor antibody, 11C1, that also cross-reacts with mouse mammary tumor virus envelope glycoprotein gp52. Also, we showed that whereas one anti-idiotype antibody, 2F10, could induce protective immunity, another anti-idiotype antibody, 3A4, induced nonprotective immunity. Here we demonstrated the existence of T helper cells which recognize anti-idiotypes that exert differential controls on tumor growth. The qualitative nature of idiotype recognizing T cells generated in response to 2F10, 3A4, irradiated tumor, and progressively growing tumor was compared. The reactivity pattern of idiotype recognizing T cells obtained from 2F10 and irradiated tumor immunized mice were similar in nature in the sense that Lyt-2- T cells obtained from these immunized mice responded to both 2F10 and 3A4 as antigen, although T cells from tumor immunized mice responded better to 3A4 antigen. On the other hand, the idiotype-recognizing T cells obtained from 3A4-immunized mice showed a similar reactivity pattern to T cells isolated from mice during the early phase of tumor growth (within day 4 to 5 after the inoculation of 10(4) live tumor cells). Lyt-2- T cells isolated from mice immunized with 3A4 or during the early phase of tumor growth responded only to 3A4 antigen. The inability of Lyt-2- T cells, isolated from 4- to 5-day-old tumor in mice, to cooperate with 2F10-TNP is not due to the absence of 2F10 idiotype recognizing T cells as 2F10 id recognizing T cells are present when examined at the precursor level. These data on the idiotype specificity of T helper cells show a correlation with the presence of anti-tumor immunity. This information will help in the design and application of idiotype vaccine in tumor immunotherapy.     

Factors influencing antibody-mediated cytotoxicity during the immunotherapy of Rauscher-virus-induced myeloid leukemic cells

Summary The present study was undertaken to determine the factors that influence antibody-mediated cytotoxicity during immunotherapy of virally transformed tumor cells. As model a Rauscher-virus-induced myeloid leukemic cell line of BALB/c origin (RMB-1) was used, which forms disseminated tumors, when inoculated intravenously in BALB/c mice. As previously reported, prolonged survival was obtained when tumor-bearing mice were treated in vivo with a single high dose of a tumor-specific IgG2a monoclonal antibody. This study shows that antibody-dependent cellular cytotoxicity is an important mechanism involved in tumor cell destruction. Since in vitro studies showed that peritoneal macrophages were capable of killing RMB-1 cells in the presence of tumor-specific monoclonal antibody and since in the tumors of mice treated with monoclonal antibody a high influx of macrophages was observed histologically, it is likely that macrophages play an important effector role in elimination of tumor cells. Successful therapy in C5-complement-deficient tumor-bearing mice suggests that complement-dependent cytotoxicity does not play a major role. In nude (T-cell-deficient) mice the therapeutic effect of tumor-specific IgG2a antibody was significantly less than in immunocompetent mice. Although infiltration analysis of tumors of treated and untreated mice showed equally low numbers of helper-T and suppressor/cytotoxic T-cells, the mortality studies of T-cell-deficient and immunocompetent mice indicate that T-cells play a substantial, auxillary role during antibody-mediated, tumor destruction in our model.     

Induction of CTL responses by simultaneous administration of liposomal peptide vaccine with anti-CD40 and anti-CTLA-4 mAb

Activation of APC via CD40-CD40 ligand pathway induces up-regulation of costimulatory molecules such as B7 and production of IL-12. Interaction between B7 on APC and CD28 on naive T cells is necessary for priming the T cells. On the other hand, interaction between B7 on APC and CTLA-4 on activated T cells transduces a negative regulatory signal to the activated T cells. In the present study, we attempted to generate tumor-specific CTL by s.c. administration of antigenic peptides encapsulated in multilamellar liposomes (liposomal peptide vaccine) with anti-CD40 mAb and/or anti-CTLA-4 mAb. Liposomal OVA257-264 and anti-CD40 mAb or anti-CTLA-4 mAb were administrated to C57BL/6 mice and the splenocytes were cocultured with OVA257-264 for 4 days. The splenic CD8+ T cells showed a significant cytotoxicity against EL4 cells transfected with cDNA of OVA. In addition, administration of both anti-CD40 and anti-CTLA-4 mAb enhanced the CTL responses. Considerable CTL responses were induced in MHC class II deficient mice by the same procedure. This finding indicated that CTL responses could be generated even in the absence of Th cells. When BALB/c mice were immunized with pRL1a peptide that are tumor-associated Ag of RLmale symbol1 leukemia cells using the same procedure, significant CTL responses were induced and prolonged survival of the BALB/c mice was observed following RLmale symbol1 inoculation. These results demonstrate that anti-CD40 mAb and anti-CTLA-4 mAb function as immunomodulators and may be applicable to specific cancer immunotherapy with antitumor peptide vaccine.     

Suppression of in vivo tumor growth by the transfection of the interleukin-5 gene into colon tumor cells

To investigate the influence of tumor producing interleukin-5 (IL-5) on growth kinetics of tumors, we transduced the murine IL-5 gene into murine colon C26 tumor cells. Two IL-5-secreting clones, low-level IL-5 producer C26-8B and high-level IL-5 producer C26-6F, were established. Both tumors, C26-6F and C26-8B, grew more slowly than the mock C26 tumor, although the in vitro growth rate of these IL-5 transfectants was much the same as that of the mock C26 cells. There was a significantly decreased number of colonies in the lung of mice given C26-6F or C26-8B tumors i.v. than in mice given mock C26 tumors i.v. Moreover, in mice given C26-6F cells i.v., a smaller number of tumor colonies in the lung was observed, as compared to the case with C26-6B cells. While the growth rate of C26-8B tumors in mice treated with anti-IL-5 mAb was more rapid than that seen in control mAb-treated mice, growth of C26-6F tumors in anti-IL-5-mAb-treated mice was slightly more rapid compared to findings in control mAb-treated mice. The isotypematched mAb did not alter the in vitro growth of mock-C26 cells or of the IL-5-gene-modified C26 cells. Growth of IL-5-secreting C26 tumors transplanted in nude mice was also inhibited. These results suggest that tumor-producing IL-5 inhibits growth of colon tumors mediated through T-cell-independent protective mechanisms of the host.     

Suppression of in vivo tumor growth by the transfection of the interleukin-5 gene into colon tumor cells

To investigate the influence of tumor producing interleukin-5 (IL-5) on growth kinetics of tumors, we transduced the murine IL-5 gene into murine colon C26 tumor cells. Two IL-5-secreting clones, low-level IL-5 producer C26-8B and high-level IL-5 producer C26-6F, were established. Both tumors, C26-6F and C26-8B, grew more slowly than the mock C26 tumor, although the in vitro growth rate of these IL-5 transfectants was much the same as that of the mock C26 cells. There was a significantly decreased number of colonies in the lung of mice given C26-6F or C26-8B tumors i.v. than in mice given mock C26 tumors i.v. Moreover, in mice given C26-6F cells i.v., a smaller number of tumor colonies in the lung was observed, as compared to the case with C26-6B cells. While the growth rate of C26-8B tumors in mice treated with anti-IL-5 mAb was more rapid than that seen in control mAb-treated mice, growth of C26-6F tumors in anti-IL-5-mAb-treated mice was slightly more rapid compared to findings in control mAb-treated mice. The isotypematched mAb did not alter the in vitro growth of mock-C26 cells or of the IL-5-gene-modified C26 cells. Growth of IL-5-secreting C26 tumors transplanted in nude mice was also inhibited. These results suggest that tumor-producing IL-5 inhibits growth of colon tumors mediated through T-cell-independent protective mechanisms of the host.     

三株荧光素酶标记的小鼠乳腺癌细胞在小鼠体内生长及转移的比较

目的采用活体成像技术比较三株荧光素酶标记的小鼠乳腺癌细胞在小鼠体内生长及转移情况,为研究肿瘤转移提供理想的动物模型以及活体分析方法。方法以荧光素酶（luciferase,Luc）作为报告基因导入小鼠乳腺癌细胞4T1、66c14和4TO7中,经G418筛选获得稳定表达荧光素酶的细胞克隆并扩大培养。标记细胞稀释成1×107cells/mL,取0.1 mL进行乳腺原位及尾静脉接种BALB/c小鼠,制作小鼠乳腺原位和尾静脉移植瘤模型,比较三株细胞在小鼠体内生长及转移情况。结果获得稳定表达荧光素酶基因的细胞克隆,将Luc标记的4T1、66c14、4TO7细胞对BALB/c小鼠乳腺原位接种后7 d,均有肿瘤生长,接种后28 d,4T1细胞乳腺原位移植瘤最大,66c14细胞瘤体次之,4TO7细胞瘤体最小;接种后35 d,三株细胞乳腺原位移植瘤大小较一致,但4T1和66c14原位移植瘤均发生转移,其中4T1细胞较66c14细胞转移严重,而4TO7细胞未见转移;接种后42 d,三株细胞乳腺原位移植瘤大小无明显差别,而4T1和66c14细胞随天数的增加,移植瘤转移程度逐渐严重,4T1较66c14细胞转移更严重,呈广泛性转移,4TO7细胞仍未见转移。将Luc标记的4T1、66c14、4TO7细胞对BALB/c小鼠尾静脉接种后7 d,小动物活体成像发现小鼠肺部均能检测到荧光,其中4T1细胞接种的小鼠肺部荧光信号最强,且小鼠陆续死亡;4TO7细胞接种小鼠肺部荧光信号次之;66c14细胞接种小鼠肺部荧光信号最弱。尾静脉接种后14 d,4TO7和66c14细胞随着观察天数的增加,转移程度逐渐严重,4TO7细胞接种小鼠肺部荧光信号较66c14细胞强且小鼠陆续死亡。结论乳腺原位自发转移模型较尾静脉转移模型更真实反应了肿瘤细胞在体的转移特性,且能完整地呈现肿瘤转移的全过程,可作为研究肿瘤转移的最理想模型。     

Spontaneous rejection of intradermally transplanted non-engineered tumor cells by neutrophils and macrophages from syngeneic strains of mice

It is not surprising that tumors arising spontaneously are rarely rejected by T cells, because in general they lack molecules to elicit a primary T-cell response. In fact, cytokine-engineered tumors can induce granulocyte infiltration leading to tumor rejection. In the present study, we i.d. injected seven kinds of non-engineered tumor cells into syngeneic strains of mice. Three of them (i.e. B16, KLN205, and 3LL cells) continued to grow, whereas four of them (i.e. Meth A, I-10, CL-S1, and FM3A cells) were spontaneously rejected after transient growth or without growth. In contrast to the i.d. injection of B16 cells into C57BL/6 mice, which induces infiltration of TAMs into the tumors, the i.d. injection of Meth A cells into BALB/c mice induced the invasion of cytotoxic inflammatory cells, but not of TAMs, into or around the tumors leading to an IFN-γ-dependent rejection. On day 5, the cytotoxic activity against the tumor cells reached a peak; and the effector cells were found to be neutrophils and macrophages. The i.d. Meth A or I-10 cell-immunized, but not non-immunized, mice rejected i.p.- or i.m.-transplanted Meth A or I-10 cells without growth, respectively. The main effector cells were CTLs; and there was no cross-sensitization between these two kinds of tumor cells, suggesting specific rejection of tumor cells by CTLs from i.d. immunized mice. These results indicate that infiltration of cytotoxic myeloid cells (i.e. neutrophils and macrophages, but not TAMs) into or around tumors is essential for their IFN-γ-dependent spontaneous rejection.     

Augmentation of antitumor effect on syngeneic murine solid tumors by an interleukin 2 slow delivery system,the IL-2 mini-pellet

We evaluated the antitumor effect of an interleukin 2 (IL-2) slow delivery system, the IL-2 mini-pellet, in two murine solid tumor models, and also investigated the enhancement of its therapeutic effect by serial administration. The IL-2 mini-pellet contains 1 × 106 units of IL-2 and releases it slowlyin vivo. In our experiment, the IL-2 mini-pellet was administered subcutaneously near the tumor site in combination with the intravenous injection of lymphokine-activated killer (LAK) cells. When this regimen was given on days 8 and 11 after the subcutaneous inoculation of Meth A fibrosarcoma into BALB/c mice, tumor growth was significantly inhibited (p < 0.05) compared to tumor growth in untreated controls. Moreover, the IL-2 mini-pellet alone was also effective in inhibiting tumor growth. In another experiment, MH134 hepatoma was inoculated into C3H/He mice. Both administration of the IL-2 minipellet alone and in combination with LAK cells resulted in complete tumor regression in four of five mice. In a third experiment, serial administration of the IL-2 mini-pellet at 3- or 5-day intervals prolonged the suppression of Meth A fibrosarcoma growth in BALB/c mice. These results suggested that the IL-2 mini-pellet could be applied to cancer immunotherapy and that its antitumor effect could be prolonged by serial administration.     

Antiangiogenic Tumor Therapy by DNA Vaccine Inducing Aquaporin-1-Specific CTL Based on Ubiquitin-Proteasome System in Mice

Aquaporin-1 (AQP-1) is a water channel protein highly expressed in the vascular endothelial cells of proliferating tissues including malignant cancers. Given that in APC ubiquitinated peptides are effectively introduced into proteasomes from which CD8 epitopes are excised, we fused ubiquitin with AQP-1 (pUB-AQP-1) to produce a DNA vaccine. In C57BL/6J mice immunized with pUB-AQP-1, the growth of B16F10 melanoma was profoundly inhibited. The antitumor effect of the pUB-AQP-1 DNA vaccine was largely mediated by CD8 T cells, which secrete IFN-γ, perforin, and granzyme-B in the presence of APCs transfected with pUB-AQP-1. AQP-1-specific CD8 T cells possessed cytotoxic activity both in vivo and in vitro. After tumor challenge, the microvessel density decreased and the ratio of total blood vessel area to tumor area was significantly reduced as compared with control mice, resulting in a dramatic suppression of tumor growth. The immunization effect was completely abrogated in immunoproteasome-deficient mice. Strikingly this pUB-AQP-1 DNA vaccine was also effective against Colon 26 colon tumors (BALB/c) and MBT/2 bladder tumors (C3H/HeN). Thus, this ubiquitin-conjugated DNA immunization-targeting tumor vasculature is a valid and promising antitumor therapy. This vaccine works across the barriers of tumor species and MHC class I differences in host mice.     

Tumor immunotherapy by converting tumor cells to MHC class II-positive,Ii protein-negative phenotype

A potent antitumor CD4⁺ T-helper cell immune response is created by inducing tumor cells in vivo to a MHC class II⁺/Ii^– phenotype. MHC class II and Ii molecules were induced in tumor cells in situ following tumor injection of a plasmid containing the gene for the MHC class II transactivator (CIITA). Ii protein was suppressed by the antisense effect of an Ii-reverse gene construct (Ii-RGC) in the same or another co-injected plasmid. The MHC class II⁺/Ii^– phenotype of the tumor cells was confirmed by FACS analysis of cells transfected in vitro and by immunostaining of tumor nodules transfected by injections in vivo. Subcutaneous Renca tumors in BALB/c mice were treated by intratumoral injection with CIITA and Ii-RGC, in combination with a subtherapeutic dose of IL-2, to up-regulate the activation of T cells. Significant tumor shrinkage and decrease in rates of progression of established Renca tumors were seen in the groups injected with Ii-RGC, compared with groups in which only IL-2 plus empty plasmid controls were injected. Our method provides an effective immunotherapy warranting further development for human cancers.Abbreviations CIITA MHC class II transactivator - DMRIE 1,2-dimeristyloxypropyl-3-dimethyl-hydroxy ethyl ammonium bromide/cholesterol - FCS fetal calf serum - RGC reverse gene constructThis research was funded in part by NCI grants R43 CA85100 and R43CA 89856.     

Suppression of atopic dermatitis and tumor metastasis in mice by small amounts of radon

We examined the effect of radon in two experimental disease models in mice by administering radon dissolved in water at 68-203 Bq/liter. Administration of radon in drinking water to NC/Nga mice significantly delayed the progression of atopic dermatitis-like skin lesions induced by picrylchloride when administered prior to the induction of disease signs. The number of pulmonary metastatic foci in C57BL/6 mice inoculated with B16 melanoma cells was also reduced significantly by administration of radon in drinking water when the number of tumor cells was small and the radon treatment was started prior to tumor inoculation. The ratio of Ifng to Il4 produced by splenocytes from BALB/c mice immunized with DNP-Ascaris was significantly increased by administration of radon in drinking water. From these results, a modulation of immunity by radon was suggested.     

The allogeneic effect on tumor growth. I. Inhibition of a murine plasmacytoma, MOPC 315, by the graft-vs-host reaction.

The allogeneic effect has been employed as a potent immunopotentiator in preventing the growth of a murine plasmacytoma and prolonging host survival. Parental BALB/c spleen cells were passively transferred to (BALB/c x A/H)F1 hybrid mice, who were then given a highly lethal dose of MOPC 315 plasmacytoma, a tumor of BALB/c origin. The resultant graft-vs-host reaction protected the recipient mice against growth of the tumor and significantly prolonged survival. This phenomenon was dependent upon the dose of BALB/c lymphoid cells employed, the route of administration, and the time interval between lymphoid cell transfer and tumor inoculation. A wide range of lymphoid cell doses and time intervals were effective, and repeated doses of allogeneic cells provided better protection than a single dose.     

Antibody-dependent cellular cytotoxicity and natural killer cytotoxicity of peritoneal cells from nude mice to herpes simplex virus-infected cells

Nude BALB/c mice (athymic) were more susceptible to fatal herpes simplex virus (HSV) than normal BALB/c mice (P = 0.002). The peritoneal cells of nude mice mediated levels of antibody-dependent cellular cytotoxicity (ADCC) of equal or greater magnitude than cells from normal BALB/c, heterozygote nu/+, or C57BL/6 mice. Unstimulated natural killer cytotoxicity of peritoneal cells from nude mice was higher (P less than 0.05) than that mediated by cells from C57BL/6 mice. Nude mice failed to make anti-HSV ADCC antibody 6 to 14 days post HSV inoculation, at times when nu/+, BALB/c, and C57BL/6 mice produced antibody. Passive reconstitution of nude mice with high titer intraperitoneal anti-HSV immune globulin provided circulating anti-HSV ADCC antibody and significant protection against lethal HSV infection.     

Soluble OX40L favors tumor rejection in CT26 colon carcinoma model

OX40 receptor-expressing regulatory T cells (Tregs) populate tumors and suppress a variety of immune cells, posing a major obstacle for cancer immunotherapy. Different ways to functionally inactivate Tregs by triggering OX40 receptor have been suggested, including anti-OX40 antibodies and Fc:OX40L fusion proteins. To investigate whether the soluble extracellular domain of OX40L (OX40Lexo) is sufficient to enhance antitumor immune response, we generated an OX40Lexo-expressing CT26 colon carcinoma cell line and studied its tumorigenicity in immunocompetent BALB/c and T cell deficient nu/nu mice.We found that soluble OX40L expressed in CT26 colon carcinoma favors the induction of an antitumor response which is not limited just to cells co-expressing EGFP as an antigenic determinant, but also eliminates CT26 cells expressing another fluorescent protein, KillerRed. Tumor rejection required the presence of T lymphocytes, as indicated by the unhampered tumor growth in nu/nu mice. Subsequent re-challenge of tumor-free BALB/c mice with CT26 EGFP cells resulted in no tumor growth, which is indicative of the formation of immunological memory. Adoptive transfer of splenocytes from mice that successfully rejected CT26 OX40Lexo EGFP tumors to naïve mice conferred 100% resistance to subsequent challenge with the CT26 EGFP tumor.     

Mirtazapine inhibits tumor growth via immune response and serotonergic system

To study the tumor inhibition effect of mirtazapine, a drug for patients with depression, CT26/luc colon carcinoma-bearing animal model was used. BALB/c mice were randomly divided into six groups: two groups without tumors, i.e. wild-type (no drug) and drug (mirtazapine), and four groups with tumors, i.e. never (no drug), always (pre-drug, i.e. drug treatment before tumor inoculation and throughout the experiment), concurrent (simultaneously tumor inoculation and drug treatment throughout the experiment), and after (post-drug, i.e. drug treatment after tumor inoculation and throughout the experiment). The "psychiatric" conditions of mice were observed from the immobility time with tail suspension and spontaneous motor activity post tumor inoculation. Significant increase of serum interleukin-12 (sIL-12) and the inhibition of tumor growth were found in mirtazapine-treated mice (always, concurrent, and after) as compared with that of never. In addition, interferon-γ level and immunocompetent infiltrating CD4+/CD8+ T cells in the tumors of mirtazapine-treated, tumor-bearing mice were significantly higher as compared with that of never. Tumor necrosis factor-α (TNF-α) expressions, on the contrary, are decreased in the mirtazapine-treated, tumor-bearing mice as compared with that of never. Ex vivo autoradiography with [(123)I]ADAM, a radiopharmaceutical for serotonin transporter, also confirms the similar results. Notably, better survival rates and intervals were also found in mirtazapine-treated mice. These findings, however, were not observed in the immunodeficient mice. Our results suggest that tumor growth inhibition by mirtazapine in CT26/luc colon carcinoma-bearing mice may be due to the alteration of the tumor microenvironment, which involves the activation of the immune response and the recovery of serotonin level.     

Construction of a DNA vaccine encoding Flk-1 extracellular domain and C3d fusion gene and investigation of its suppressing effect on tumor growth

Although the critical role of complement component C3d as a molecular adjuvant in preventing virus infection is well established, its role in cancer prophylaxis and treatment is unclear. In this study, we constructed a recombinant plasmid encoding Flk-1 and C3d3 fusion proteins and investigated its transient expression in vitro in transfected eukaryotic cells and its antibody response in immunized mice. Subsequently, we investigated the vaccine’s ability to elicit an immune response leading to suppression of angiogenesis and tumor growth in mice bearing bladder transitional cell carcinoma. Using Western blotting, immunocytochemistry, and flow cytometry, we detected the expression of Flk-1 and C3d3 fusion proteins in COS-7 cells transfected with these recombinant plasmids. Further binding experiment using CR2 (C3d receptor) positive Raji cells that were incubated with transfected COS-7 supernatant indicated that C3d was successfully fused to Flk-1. Although both vaccines elicited peak antibody levels at 5 weeks, Flk-1-specific antibody titer in pSG.SS.Flk-1_ECD.C3d3.YL-immunized mice was significantly higher when compared to pSG.SS.Flk-1_ECD.YL-immunized mice. The results of experiments with bladder tumor-bearing mice showed that the vaccine inhibited tumor growth significantly. These results suggest that C3d plays a critical role in tumor immunotherapy by promoting antibody response in Flk-1-based DNA vaccines. This approach may provide a new strategy for the rational design of anti-angiogenic therapies for the treatment of solid tumors and provide a basis for the further exploitation and application of the anti-angiogenesis DNA vaccines.     

Immunotherapy of murine leukemias by monoclonal antibody. I. Effect of passively administered antibody on growth of transplanted tumor cells

The objective of the present study was to establish a model system for the evaluation of passive immunotherapy of murine leukemias. Monoclonal antibodies directed at T lymphocyte differentiation antigens (Thy 1 and Lyt 2) were tested for their effect on tumors that were grown in hosts congenic for the target antigen. Tumor challenges were selected that were at least 500 times the dose that was lethal in 50% of untreated controls. The A strain leukemia, ASL.1, was transplanted subcutaneously into a/Thy 1.1 congenic hosts. Intraperitoneal administration of anti-Thy 1.2 monoclonal antibodies of the IgG3 and IgM classes reduced tumor growth. Up to 90% of the mice receiving antibody of the IgG3 subclass failed to develop tumors, whereas IgM antibodies prolonged survival time, but the mice eventually died of tumors. Antibody was most effective if administered within 24 hr of tumor inoculation; delay of antibody injection for 48 hr prolonged host survival but did not eradicate cells at the injection site or prevent metastases. The C57BL/6-derived tumors, ERLD and EL4, were evaluated for susceptibility to treatment with antibody directed at the Lyt 2.2 alloantigen using the protocol that was effective in treating aSL.1. Monoclonal antibody of the IgG2a subclass was effective in the case of C57BL/6/Lyt 2.1 congenic mice bearing ERLD, but caused a decrease in survival time of mice bearing the transplanted EL4 tumor. Thus, antibody of the appropriate immunoglobulin subclass can be effective in controlling tumor growth if administered in the optimal treatment regimen, but inherent features of the tumor cell ultimately determine whether abrogation or enhancement of growth will occur.