Local costimulation reinvigorates tumor-specific cytolytic T lymphocytes for experimental therapy in mice with large tumor burdens

Epithelial CD80 promotes immune surveillance of colonic preneoplastic lesions and its expression is increased by oxidative stress through STAT3 in colon cancer cells

BACKGROUND

One of the most potent costimulatory molecules involved in the recognition and killing of tumor cells is CD80. However, its role and the molecular mechanisms regulating its expression in sporadic colorectal carcinogenesis remain elusive. Here, we provide evidence for CD80 overexpression in human colon epithelial cells derived from preneoplastic mucosa.

METHODS

Expression of CD80 on colonic epithelial cells isolated from normal human colonic mucosa, preneoplastic and neoplastic specimens was assessed by flow cytometry. WT and CD80KO mice received azoxymethane to induce colon preneoplastic lesions and sacrificed to perform histology, flow cytometry analysis and immunohistochemistry of colonic mucosa. Some WT mice were treated with a monoclonal anti-CD80 antibody following AOM administration. Primary colon epithelial cells and CT26 cell line were used to quantify the expression of CD80 in response to pro-oxidant stimuli. Specific pharmacological inhibitors and siRNA silencing were used to inhibit MAPK pathways and STAT3.

RESULTS

CD80 expression was significantly increased in colon epithelial cells of human preneoplastic lesions. In the AOM model, CD80 impairment by administration of neutralizing antibodies or use of CD80 knockout mice enhanced dysplasia development. In vitro, CD80 upregulation was induced by oxidative stress in colon cancer cells and primary colon epithelial cells. In addition, reactive oxygen species could induce CD80 expression via the JNK and p38 MAPK pathways, that activated STAT3 transcription factor in colon cancer epithelial cells.

CONCLUSION

This study provide evidence for a major role of CD80 in orchestrating immune surveillance of colon preneoplastic lesions and might help to develop novel approaches that exploit anti-tumor immunity to prevent and control colon cancer.

Knockdown of LncRNA MALAT1 contributes to cell apoptosis via regulating NF-κB/CD80 axis in neonatal respiratory distress syndrome

Neonatal respiratory distress syndrome (NRDS) is a leading cause of morbidity in premature newborns and is a common reason for admission to the neonatal intensive care unit (NICU). Recent studies found that the pathogenesis of NRDS is not simply lung immaturity. Apoptosis is an essential process for the development and maturation of the lungs. In this study, we report a critical role of lncRNA MALAT1 in regulating CD80 transcription in the NRDS-associated apoptosis via binding with NF-κB. We first showed MALAT1 and CD80 were highly expressed in the peripheral blood mononuclear cells of NRDS with infection exposure. Then we found MALAT1 expressions were significantly increased by the treatment of LPS. We confirmed knockdown of MALAT1 promoted cell viability by CCK-8 assays, cell apoptosis by flow cytometric assays and cytoskeleton destruction by immunocytochemistry. We confirmed CD80 expression level was associated with cell apoptosis by affecting PARP and caspase-3. Then we demonstrated knockdown of MALAT1 promoted CD80 transcription in A549 cells. Furthermore, we confirmed that MALAT1 downregulated transcriptional expression of CD80 by interfering with NF-κB activation and disrupting its binding efficiency with the CD80 promoter in the cell nucleus. In conclusion, we first identified lncRNA MALAT1 as an important prognosis maker for NRDS patients. Most significantly, this study then demonstrated a novel regulatory function of knocked-down MALAT1 on the transcriptional level of CD80 by enhancing the binding of NF-κB to CD80 promoter. Since the interaction between MALAT1 and CD80 plays an essential role in the cell apoptosis of NRDS, our findings demonstrate the possibility of using MALAT1 as therapeutic target for treatment of NRDS, and extend existing knowledge about the molecular mechanism that underlies NRDS pathogensis.

Overcoming tumor immune evasion with an unique arbovirus

Combining dendritic cell vaccination with the adjuvant effect of a strain of dengue virus may be a way to overcome known tumor immune evasion mechanisms. Dengue is unique among viruses as primary infections carry lower mortality than the common cold, but secondary infections carry significant risk of hypovolemic shock. While current immuno-therapies rely on a single axis of attack, this approach combines physiological (hyperthermic reduction of tumor perfusion), immunological (activation of effector cells of the adaptive and innate immune system), and apoptosis-inducing pathways (sTRAIL) to destroy tumor cells. The premise of using multiple mechanisms of action in synergy with a decline in the ability of the tumor cells to employ resistance methods suggests the potential of this combination approach in cancer immunotherapy.

Limited density of an antigen presented by RMA-S cells requires B7-1/CD28 signaling to enhance T-cell immunity at the effector phase

The association of B7-1/CD28 between antigen presenting cells (APCs) and T-cells provides a second signal to proliferate and activate T-cell immunity at the induction phase. Many reports indicate that tumor cells transfected with B7-1 induced augmented antitumor immunity at the induction phase by mimicking APC function; however, the function of B7-1 on antitumor immunity at the effector phase is unknown. Here, we report direct evidence of enhanced T-cell antitumor immunity at the effector phase by the B7-1 molecule. Our experiments in vivo and in vitro indicated that reactivity of antigen-specific monoclonal and polyclonal T-cell effectors against a Lass5 epitope presented by RMA-S cells is increased when the cells expressed B7-1. Use of either anti-B7-1 or anti-CD28 antibodies to block the B7-1/CD28 association reduced reactivity of the T effectors against B7-1 positive RMA-S cells. Transfection of Lass5 cDNA into or pulse of Lass5 peptide onto B7-1 positive RMA-S cells overcomes the requirement of the B7-1/CD28 signal for T effector response. To our knowledge, the data offers, for the first time, strong evidence that supports the requirement of B7-1/CD28 secondary signal at the effector phase of antitumor T-cell immunity being dependent on the density of an antigenic peptide.

Low dose decitabine treatment induces CD80 expression in cancer cells and stimulates tumor specific cytotoxic T lymphocyte responses

Lack of immunogenicity of cancer cells has been considered a major reason for their failure in induction of a tumor specific T cell response. In this paper, we present evidence that decitabine (DAC), a DNA methylation inhibitor that is currently used for the treatment of myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) and other malignant neoplasms, is capable of eliciting an anti-tumor cytotoxic T lymphocyte (CTL) response in mouse EL4 tumor model. C57BL/6 mice with established EL4 tumors were treated with DAC (1.0 mg/kg body weight) once daily for 5 days. We found that DAC treatment resulted in infiltration of IFN-γ producing T lymphocytes into tumors and caused tumor rejection. Depletion of CD8⁺, but not CD4⁺ T cells resumed tumor growth. DAC-induced CTL response appeared to be elicited by the induction of CD80 expression on tumor cells. Epigenetic evidence suggests that DAC induces CD80 expression in EL4 cells via demethylation of CpG dinucleotide sites in the promoter of CD80 gene. In addition, we also showed that a transient, low-dose DAC treatment can induce CD80 gene expression in a variety of human cancer cells. This study provides the first evidence that epigenetic modulation can induce the expression of a major T cell co-stimulatory molecule on cancer cells, which can overcome immune tolerance, and induce an efficient anti-tumor CTL response. The results have important implications in designing DAC-based cancer immunotherapy.

IL-10 contributes to the suppressive function of tumour-associated myeloid cells and enhances myeloid cell accumulation in tumours

Studies have revealed that tumour-associated myeloid cells (TAMC) are one of the major sources of IL-10 in tumour-bearing mice. However, the significance of TAMC-derived IL-10 in tumour immunity is poorly understood. Here, we show that IL-10 blockade or IL-10 deficiency reduces the capacity of TAMC in suppressing the proliferation of P1A-specific CD8 T cells. In the spleen, IL-10-deficient and wild-type (WT) mice bearing large tumour burdens have similar TAMC populations. The tumours from IL-10-deficient mice, however, have reduced numbers of TAMC compared with tumours from their WT counterparts. IL-10⁻/⁻ RAG-2⁻/⁻ mice also had reduced numbers of TAMC compared with tumours from IL-10⁺/⁺ RAG-2⁻/⁻ mice; therefore, the reduction in TAMC in IL-10-deficient tumours was not because of adaptive immune response in tumours. Adoptively transferred tumour antigen-specific CD8 T cells expanded more efficiently within tumours in IL-10⁻/⁻ RAG-2⁻/⁻ mice than in tumours from IL-10⁺/⁺ RAG-2⁻/⁻ mice. Cytotoxic T lymphocyte adoptive transfer therapy prevented tumour evasion in IL-10⁻/⁻ RAG-2⁻/⁻ mice more efficiently than in IL-10⁺/⁺ RAG-2⁻/⁻ mice. Thus, IL-10 enhances the accumulation of myeloid cells in tumours, and TAMC-derived IL-10 suppresses the activation and expansion of tumour antigen-specific T cells.

Tumor expression of CD200 inhibits IL-10 production by tumor-associated myeloid cells and prevents tumor immune evasion of CTL therapy

CD200 is a cell-surface glycoprotein that functions through interaction with the CD200 receptor on myeloid lineage cells to regulate myeloid cell functions. Expression of CD200 has been implicated in multiple types of human cancer; however, the impact of tumor expression of CD200 on tumor immunity remains poorly understood. To evaluate this issue, we generated CD200-positive mouse plasmacytoma J558 and mastocytoma P815 cells. We found that established CD200-positive tumors were often completely rejected by adoptively transferred CTL without tumor recurrence; in contrast, CD200-negative tumors were initially rejected by adoptively transferred CTL but the majority of tumors recurred. Tumor expression of CD200 significantly inhibited suppressive activity and IL-10 production by tumor-associated myeloid cells (TAMC), and as a result, more CTL accumulated in the tumor and exhibited a greater capacity to produce IFN-gamma in CD200-positive tumors than in CD200-negative tumors. Neutralization of IL-10 significantly inhibited the suppressor activity of TAMC, and IL-10-deficiency allowed TAMC to kill cancer cells and their antigenic variants, which prevented tumor recurrence during CTL therapy. Thus, tumor expression of CD200 prevents tumor recurrence via inhibiting IL-10 production by TAMC.

Tumor cells engineered to codisplay on their surface 4-1BBL and LIGHT costimulatory proteins as a novel vaccine approach for cancer immunotherapy

Primary tumor cells genetically modified to express on their surface a collection of immunological ligands may have utility as therapeutic autologous cancer vaccines. However, genetic modification of primary tumor cells is not only cost, labor, and time intensive, but also has safety repercussions. As an alternative, we developed the ProtEx^™ technology that involves generation of immunological ligands with core streptavidin (SA) and their display on biotinylated cells in a rapid and efficient manner. We herein demonstrate that TC-1 tumor cells can be rapidly and efficiently engineered to codisplay on their surface two costimulatory proteins, SA-4-1BBL and SA-LIGHT, simultaneously. Vaccination with irradiated TC-1 cells codisplaying both chimeric proteins showed 100% efficacy in a prophylactic and > 55% efficacy in a therapeutic tumor setting. In contrast, vaccination with TC-1 cells engineered with either protein alone showed significantly reduced efficacy in the prophylactic setting. Vaccine efficacy was associated with the generation of primary and memory T cell and antibody responses against the tumor without detectable signs of autoimmunity. Engineering tumor cells in a rapid and effective manner to simultaneously display on their surface a collection of immunostimulatory proteins with additive/synergistic functions presents a novel alternative approach to gene therapy with considerable potential for cancer immunotherapy.

Targeting activation-induced cytidine deaminase overcomes tumor evasion of immunotherapy by CTLs

Activation-induced cytidine deaminase (AID) is an enzyme essential for the generation of Ab diversity in B cells and is considered to be a general gene mutator. In addition, AID expression was also implicated in the pathogenesis of human B cell malignancies and associated with poor prognosis. In this study, we report that small interfering RNA silencing of AID in plasmacytoma dramatically increased its susceptibility to immunotherapy by CTLs. AID silencing did not decrease the mutation frequencies of tumor Ag gene P1A. Gene-array analysis showed dramatically altered expression of a number of genes in AID-silenced plasmacytoma cells, and upregulation of CD200 was shown to be in favor of tumor eradication by CTLs. Taken together, we demonstrate a novel function of AID in tumor evasion of CTL therapy and that targeting AID should be beneficial in the immunotherapy of AID-positive tumors.

Rapid tolerization of virus-activated tumor-specific CD8+ T cells in prostate tumors of TRAMP mice

To study T cell responses to tumors in an autochthonous model, we expressed a CD8 T cell epitope SIYRYYGL (SIY) in the prostate of transgenic adenocarcinoma (TRAMP) mice (referred to as TRP-SIY), which spontaneously develop prostate cancer. Naïve SIY-specific CD8 T cells adoptively transferred into TRP-SIY mice became tolerized in the prostate draining lymph nodes. Vaccination of TRP-SIY mice intranasally with influenza virus that expresses the SIY epitope resulted in generation of SIY-specific effector T cells in the lung-draining lymph nodes. These effector T cells expressed TNFalpha and IFNgamma, eliminated SIY peptide-loaded target cells in vivo, and infiltrated prostate tumors, where they rapidly lost the ability to produce effector cytokines. A population of these T cells persisted in prostate tumors but not in lymphoid organs and could be induced to re-express effector functions following cytokine treatment in vitro. These findings suggest that T cells of a given clone can be activated and tolerized simultaneously in different microenvironments of the same host and that effector T cells are rapidly tolerized in the tumors. Our model provides a system to study T cell-tumor interactions in detail and to test the efficacy of cancer immunotherapeutic strategies.

Modulation of NKT cell development by B7-CD28 interaction: an expanding horizon for costimulation

It has been demonstrated that the development of NKT cells requires CD1d. The contribution of costimulatory molecules in this process has not been studied. Here we show that in mice with targeted mutations of B7-1/2 and CD28, the TCRbeta(+)alpha-Galcer/CD1d(+) (iValpha14 NKT) subset is significantly reduced in the thymus, spleen and liver. This is mainly due to decreased cell proliferation; although increased cell death in the thymi of CD28-deficient mice was also observed. Moreover, in the B7-1/2- and CD28-deficient mice, we found a decreased percentage of the CD4(-)NK1.1(+) subset and a correspondingly increased portion of the CD4(+)NK1.1(-) subset. In addition, the mice with a targeted mutation of either B7 or CD28 had a reduced susceptibility to Con A induced hepatitis, which is known to be mediated by NKT cells. Our results demonstrate that the development, maturation and function of NKT cell are modulated by the costimulatory pathway and thus expand the horizon of costimulation into NKT, which is widely viewed as a bridge between innate and adaptive immunity. As such, costimulation may modulate all major branches of cell-mediated immunity, including T cells, NK cells and NKT cells.

Robust anti-tumor immunity and memory in Rag-1-deficient mice following adoptive transfer of cytokine-primed splenocytes and tumor CD80 expression

Successful immunotherapy of solid tumors has proven difficult to achieve. The aim of the current study was to further investigate the effects of peripheral CD80-mediated co-stimulation on the efficacy of polyclonal anti-tumor effector CTL in an adoptive transfer model. Splenocytes obtained from wild-type mice immunized with CD80-transduced EL4 tumor cells were expanded in vitro in the presence of either IL-12 or IL-15 and irradiated CD80-transduced EL4 tumor cells. Polyclonal CD8 T cells were the major subset in the effector population. Primed effector cells were adoptively transferred into immuno-deficient Rag-1-deficient mice which were then challenged with syngeneic vector-control or CD80-transduced EL4 tumor cells. Expression of CD80 enhanced the elimination of EL4 tumors and mouse survival. Both IL-12 and IL-15 cultured cells had enhanced cytotoxicity. Importantly, anti-tumor memory was maintained without tumor evasion following re-challenge with either CD80-transduced and vector-control EL4 cells. We also show, using antibody-mediated depletion, that endogenous NK cells present in Rag-1-deficient mice exert anti-EL4 tumor activity that is enhanced by CD80 expression. Collectively these data show that peripheral co-stimulation by tumor expression of CD80 results in enhanced anti-tumor efficacy of NK and polyclonal effector T cells, and suggest that TCR repertoire diversity helps protect against tumor escape and provides memory with resultant robust immunity to subsequent tumor challenge irrespective of CD80 status.

Different lineages of P1A-expressing cancer cells use divergent modes of immune evasion for T-cell adoptive therapy

Tumor evasion of T-cell immunity remains a significant obstacle to adoptive T-cell therapy. It is unknown whether the mode of immune evasion is dictated by the cancer cells or by the tumor antigens. Taking advantage of the fact that multiple lineages of tumor cells share the tumor antigen P1A, we adoptively transferred transgenic T cells specific for P1A (P1CTL) into mice with established P1A-expressing tumors, including mastocytoma P815, plasmocytoma J558, and fibrosarcoma Meth A. Although P1CTL conferred partial protection, tumors recurred in almost all mice. Analysis of the status of the tumor antigen revealed that all J558 tumors underwent antigenic drift whereas all P815 tumors experienced antigenic loss. Interestingly, although Meth A cells are capable of both antigenic loss and antigenic drift, the majority of recurrent Meth A tumors retained P1A antigen. The ability of Meth A to induce apoptosis of P1CTL in vivo alleviated the need for antigenic drift and antigenic loss. Our data showed that, in spite of their shared tumor antigen, different lineages of cancer cells use different mechanisms to evade T-cell therapy.

An Agonist Antibody Specific for CD40 Induces Dendritic Cell Maturation and Promotes Autologous Anti-tumour T-cell Responses in an In vitro Mixed Autologous Tumour Cell/Lymph Node Cell Model

CD40-mediated interactions play an important role in the response to a variety of diseases, including cancer. Engagement of CD40 on antigen-presenting cells, namely dendritic cells (DC), by CD40L leads to maturation and up-regulation of co-stimulatory molecules B7.1 and B7.2 (CD80 and CD86). These molecules are requisite to subsequent antigen-specific activation of T cells. T-cell activation is a critical aspect of specific anti-tumour immune responses that have become the focus of a variety of cancer immunotherapy approaches. Clinical trials involving immunologic interventions have shown clinical responses confirming that the immune system can be harnessed for the treatment of cancer. However, the clinical response rate has been low, signifying the need for new immunotherapeutic strategies. To this end, an agonist antibody specific for CD40, CP-870,893, has been developed. A fully autologous mixed tumour cell/lymph node cell model was utilized to demonstrate that CP-870,893 promotes the responsiveness of lymph node-derived T cells to autologous tumour. Specifically, T cells from the tumour-draining lymph nodes are not responsive to autologous tumour cells; however, in the presence of CP-870,893, this unresponsiveness is reversed, as indicated by lymph node cell proliferation and cytokine secretion. Monocyte-derived DC treated with CP-870,893 consistently display a mature phenotype: up-regulation of CD80, CD83, CD86 and HLA-DR expression, increased Mip1alpha and IL-12 secretion, and the loss of exogenous antigen-presenting capability subsequent to treatment with the antibody. These data indicate that CP-870,893 binds to and activates DC, ultimately driving a specific anti-tumour T-cell response.

Immune competence of cancer-reactive T cells generated de novo in adult tumor-bearing mice

The impact of timing of antigen introduction into fetus and neonates leads to the suggestion that pre-existing antigens are tolerogenic to immunocompetent cells generated thereafter. This hypothesis predicts that in patients with cancer who are undergoing bone marrow transplantation, newly produced T cells with specificity for pre-existing tumor cells will be inactivated by the tumor antigens in the host. Because the effect of tumor cells on developing cancer-reactive T cells has not been investigated, we set out to systematically analyze the impact of tumor cells in the periphery on the development of tumor-reactive T cells in the thymus and their immunocompetence in the periphery. Our data demonstrate that in the host in which a tumor is established in the periphery, the cancer-reactive T cells develop normally, remain fully immunocompetent, become activated in the periphery, and cause regression of large established tumors. The immunocompetence of T cells generated in an antigen-bearing host is also confirmed in a skin graft transplantation model.

Arming Tumor-Reactive T Cells with Costimulator B7-1 Enhances Therapeutic Efficacy of the T Cells

T cells ectopically expressing costimulators are pathogenic and contribute to autoimmunity against self-antigens. Given that tumor antigens are often self-antigen or mutated self-antigens, we hypothesize that neoexpressing a costimulator on tumor-reactive T cells may likewise enhance their reactivity to tumor. To test this hypothesis, we have expressed B7-1 on OT-1 CD8+ T-cell receptor transgenic T cells via protein transfer (or protein "painting"). Naïve OT-1 T cells, after being painted with B7-1, can self-costimulate themselves, elicit enhanced proliferative and CTL responses to E.G7-ovalbumin tumor cells (expressing a cognate antigen), and become resistant to CD4+CD25+ regulatory T-cell-mediated suppression. Importantly, these T cells, when coimplanted with E.G7-ovalbumin tumor cells into a syngeneic host, are three to nine times more potent than are control T cells (mock painted with human IgG) in inhibiting tumor growth. Further, on transfer into mice bearing established E.G7-ovalbumin tumors, B7-1-painted ex vivo-amplified OT-1 T cells induced complete tumor regression in 65% of treated mice, whereas the control T cells did so in only 28% of treated mice. Finally, on transfer into mice bearing less immunogenic 4T1 breast tumors, B7-1-painted tumor-reactive CD8+ T cells improved the survival of treated mice to a greater extent than did the control T cells. Hence, this study establishes that arming tumor-reactive T cells with a costimulator can enhance their antitumor efficacy.

Autologous immune strategies to reduce the risk of leukemic relapse: Consideration for IL-15

The graft-versus-leukemia effect following allogeneic stem cell transplantation (SCT) reduces the incidence of leukemic relapse and establishes that effector cells can eliminate or at least contain resistant leukemic stem cells. Natural killer cells also appear to play a role in directly lowering the rate of relapse following allogeneic SCT in patients with acute myeloid leukemia. To date, however, effective prevention of leukemic relapse by autologous immune effector cells has not been demonstrated. This article examines some of the challenges that limit autologous antileukemia immunity as well as some possible immunotherapeutic approaches that may help control leukemic relapse following autologous SCT.

Ex vivo expansion of dendritic-cell-activated antigen-specific CD4+ T cells with anti-CD3/CD28, interleukin-7, and interleukin-15: Potential for adoptive T cell immunotherapy

There is an increasing realization that the failure of adoptive therapy with cytotoxic T lymphocytes in the autologous setting, at least in part, results from the lack of help from antigen-specific CD4+ T cells. To incorporate these cells into this treatment strategy, it is not known whether currently used ex vivo culture conditions are adequate for expanding and charting these T cells with the desired qualities for optimal in vivo activity. In this study, we show that stimulation with agonistic antibodies to CD3 plus CD28 (anti-CD3/CD28), a commonly used method for CD4+ T cell expansion, is unable to expand dendritic-cell-activated hepatitis B virus (HBV)-specific CD4+ T cells to clinical relevant numbers. Whereas, in combination with interleukin(IL)-7 and IL-15, it leads to a 4000-fold expansion of HBV-specific CD4+ T cells in 2 weeks. This outcome is correlated with the anti-apoptosis effect of IL-7 and IL-15. Importantly, antigen specificity is preserved during expansion. Although a late addition of IL-2 to the anti-CD3/CD28-expanding cultures also results in robust expansion, this expansion condition renders HBV-specific CD4+ T cells more sensitive to cytokine withdrawal-, activation-, and transforming growth factor-beta-induced cell death compared to those expanded in IL-7 and IL-15. Moreover, NKG2D rather than 4-1BB, whose ligands are constitutively expressed on tumor cells, is significantly up-regulated on IL-7/IL-15-expanded HBV-specific CD4+ T cells, and its engagement promotes expansion and interferon-gamma production by these cells and thus may serve to provide co-stimulation to T cells once they reach tumor tissues. Collectively, these results may have important therapeutic implications for adoptive T cell therapy.

CD28-mediated costimulation impacts on the differentiation of DC vaccination-induced T cell responses

Costimulatory signals such as the ones elicited by CD28/B7 receptor ligation are essential for efficient T cell activation but their role in anti-tumour immune responses remains controversial. In the present study we compared the efficacy of DC vaccination-induced melanoma specific T cell responses to control the development of subcutaneous tumours and pulmonary metastases in CD28-deficient mice. Lack of CD28-mediated costimulatory signals accelerated tumour development in both model systems and also the load of pulmonary metastases was strongly increased by the end of the observation period. To scrutinize whether lack of CD28 signalling influences priming, homing or effector function of Trp-2(180-188)/K(b)-reactive T cells we investigated the characteristics of circulating and tumour infiltrating T cells. No difference in the frequency of Trp-2(180-188)/K(b)-reactive CD8+ T cells could be demonstrated among the cellular infiltrate of subcutaneous tumours after DC vaccination between both genotypes. However, the number of IFN-gamma-producing Trp-2-reactive cells was substantially lower in CD28-deficient mice and also their cytotoxicity was reduced. This suggests that CD28-mediated costimulatory signals are essential for differentiation of functional tumour-specific CD8+ T-effector cells despite having no impact on the homing of primed CD8+ T cells.

Targeted elimination of prostate cancer by genetically directed human T lymphocytes

The genetic transfer of antigen receptors is a powerful approach to rapidly generate tumor-specific T lymphocytes. Unlike the physiologic T-cell receptor, chimeric antigen receptors (CARs) encompass immunoglobulin variable regions or receptor ligands as their antigen recognition moiety, thus permitting T cells to recognize tumor antigens in the absence of human leukocyte antigen expression. CARs encompassing the CD3zeta chain as their activating domain induce T-cell proliferation in vitro, but limited survival. The requirements for genetically targeted T cells to function in vivo are less well understood. We have, therefore, established animal models to assess the therapeutic efficacy of human peripheral blood T lymphocytes targeted to prostate-specific membrane antigen (PSMA), an antigen expressed in prostate cancer cells and the neovasculature of various solid tumors. In vivo specificity and antitumor activity were assessed in mice bearing established prostate adenocarcinomas, using serum prostate-secreted antigen, magnetic resonance, computed tomography, and bioluminescence imaging to investigate the response to therapy. In three tumor models, orthotopic, s.c., and pulmonary, we show that PSMA-targeted T cells effectively eliminate prostate cancer. Tumor eradication was directly proportional to the in vivo effector-to-tumor cell ratio. Serial imaging further reveals that the T cells must survive for at least 1 week to induce durable remissions. The eradication of xenogeneic tumors in a murine environment shows that the adoptively transferred T cells do not absolutely require in vivo costimulation to function. These results thus provide a strong rationale for undertaking phase I clinical studies to assess PSMA-targeted T cells in patients with metastatic prostate cancer.

Molecular and immunophenotypical characterization of progressive and regressive leukemia cell lines

The P815 and P198 cell lines are clonally related mouse mastocytoma cell lines. They differ in their biologic behavior in that P815 is a progressive tumor cell line, whereas P198 is a regressive one. These cell lines have been extensively used as models for the study of tumor-host relationships and tumor immunology. Although some of their biological properties have been well documented, the molecular mechanisms underlying tumor progression or regression have not been completely elucidated. In this study, we characterized the growth behavior and immunophenotype of these two cell lines, and analyzed their gene profiles using a complementary deoxynucleic acid (cDNA) microarray composed of 514 immunologically relevant genes. Our data showed that the two cell lines exhibited quite dissimilar and contrasting growth characteristics when inoculated into syngeneic mice. P815 tumors grew unremittingly, while P198 tumors gradually regressed. From a molecular viewpoint, P815 cells showed a higher expression of genes promoting tumor growth, such as IGF-1, IL-8R, FGFR1, VEGF-A, and VEGF-B. On the other hand, P198 tumor cells expressed CD11b and CD80, which favor the recruitment of lymphocytes and antigen-presenting cells (APCs), as well as the elicitation of antitumor immunity. P198 tumor cells also depicted a higher expression of genes inhibiting tumor growth, such as TNF-alpha, SOCS-1, CIS1, 4-1BB, and GDF-10. In conclusion, our results contribute further information in the understanding of the molecular mechanisms associated with the regression and progression of P815 and P198 tumor cells.

Radiation-induced cell death and dendritic cells: potential for cancer immunotherapy?

Dendritic cells are key orchestrators of the immune system. There is considerable interest in their use for treating cancer. Whether they initiate an effective cytotoxic response against antigen-bearing cells, or produce tolerance, depends on the context in which those antigens are presented. Ionising radiation, and the cell death it causes, has several properties that may facilitate such an effective response. A range of in-vitro and in-vivo data supports this, although potential problems exist that may require concurrent strategies.

Effect of bone marrow-derived monocytes transfected with RNA of mouse colon carcinoma on specific antitumor immunity

AIM: To investigate the effect of bone marrow-derived monocytes transfected with RNA of CT-26 (a cell line of mouse colon carcinoma) on antitumor immunity.

METHODS: Mouse bone marrow-derived monocytes were incubated with mouse granulocyte macrophage colony stimulating factor (mGM-CSF) in vitro, and the purity of monocytes was detected by flow cytometry. Total RNA of CT-26 was obtained by TRIzol’s process, and monocytes were transfected by TransMessenger in vitro. The activity of cytotoxic T lymphocytes (CTL) in vivo was estimated by the modified lactate dehydrogenase (LDH) release assay. Changes of tumor size in mice and animal’s survival time were observed in different groups.

RESULTS: Monocytes from mouse bone marrow were successfully incubated, and the positive rate of CD11b was over 95%. Vaccination of the monocytes transfected with total RNA induced a high level of specific CTL activity in vivo, and made mice resistant to the subsequent challenge of parental tumor cells. In vivo effects induced by monocytes transfected with total RNA were stronger than those induced by monocytes pulsed with tumor cell lysates.

CONCLUSION: Antigen presenting cells transfected with total RNA of CT-26 can present endogenous tumor antigens, activate CTL, and effectively induce specific antitumor immunity.

B7-CD28 Interaction Promotes Proliferation and Survival but Suppresses Differentiation of CD4−CD8− T Cells in the Thymus

Costimulatory molecules play critical roles in the induction and effector function of T cells. More recent studies reveal that costimulatory molecules enhance clonal deletion of autoreactive T cells as well as generation and homeostasis of the CD25(+)CD4(+) regulatory T cells. However, it is unclear whether the costimulatory molecules play any role in the proliferation and differentiation of T cells before they acquire MHC-restricted TCR. In this study, we report that targeted mutations of B7-1 and B7-2 substantially reduce the proliferation and survival of CD4(-)CD8(-) (double-negative (DN)) T cells in the thymus. Perhaps as a result of reduced proliferation, the accumulation of RAG-2 protein in the DN thymocytes is increased in B7-deficient mice, which may explain the increased expression of TCR gene and accelerated transition of CD25(+)CD44(-) (DN3) to CD25(-)CD44(-) (DN4) stage. Qualitatively similar, but quantitatively less striking effects were observed in mice with a targeted mutation of CD28, but not CTLA4. Taken together, our results demonstrate that the development of DN in the thymus is subject to modulation by the B7-CD28 costimulatory pathway.

Antigenic drift as a mechanism for tumor evasion of destruction by cytolytic T lymphocytes

It is established that mutations in viral antigenic epitopes, or antigenic drifts, allow viruses to escape recognition by both Ab's and T lymphocytes. It is unclear, however, whether tumor cells can escape immune recognition via antigenic drift. Here we show that adoptive therapy with both monoclonal and polyclonal transgenic CTLs, specific for a natural tumor antigen, P1A, selects for multiple mutations in the P1A antigenic epitope. These mutations severely diminish T cell recognition of the tumor antigen by a variety of mechanisms, including modulation of MHC:peptide interaction and TCR binding to MHC:peptide complex. These results provide the first evidence for tumor evasion of T cell recognition by antigenic drift, and thus have important implications for the strategy of tumor immunotherapy.

Current and future strategies for the treatment of malignant brain tumors

Glioblastoma (GB) is the most common subtype of primary brain tumor in adults. These tumors are highly invasive, very aggressive, and often infiltrate critical neurological areas within the brain. The mean survival time after diagnosis of GB has remained unchanged during the last few decades, in spite of advances in surgical techniques, radiotherapy, and also chemotherapy; patients' survival ranges from 9 to 12 months after initial diagnosis. In the same time frame, with our increasing understanding and knowledge of the physiopathology of several cancers, meaningful advances have been made in the treatment and control of several cancers, such as breast, prostate, and hematopoietic malignancies. Although a number of the genetic lesions present in GB have been elucidated and our understanding of the progressions of this cancer has increased dramatically over the last few years, it has not yet been possible to harness this information towards developing effective cures. In this review, we will focus on the classical ways in which GB is currently being treated, and will introduce a novel therapeutic modality, i.e., gene therapy, which we believe will be used in combination with classical treatment strategies to prolong the life-span of patients and to ultimately be able to control and/or cure these brain tumors. We will discuss the use of several vector systems that are needed to introduce the therapeutic genes within either the tumor mass, if these are not resectable, or the tumor bed, after successful tumor resection. We also discuss different therapeutic modalities that could be exploited using gene therapy, i.e., conditional cytotoxic approach, direct cytotoxicity, immunotherapy, inhibition of angiogenesis, and the use of pro-apoptotic genes. The advantages and disadvantages of each of the current vector systems available to transfer genes into the CNS are also discussed. With the advances in molecular techniques, both towards the elucidation of the physiopathology of GB and the development of novel, more efficient and less toxic vectors to deliver putative therapeutic genes into the CNS, it should be possible to develop new rationale and effective therapeutic approaches to treat this devastating cancer.

B7-CTLA4 interaction promotes cognate destruction of tumor cells by cytotoxic T lymphocytes in vivo

Costimulatory molecules B7-1 and B7-2 (hereby collectively called B7) interact with CD28 and CTLA4 on T cells and promote antitumor immunity. The function of B7-CTLA4 interaction in antitumor CTL response remains controversial. Here we used CD28(-/-) and CD28(+/-) or CD28(+/+) transgenic mice that express the T-cell receptor specific for an unmutated tumor antigen, P1A, and for tumor cells expressing a CTLA4-specific B7 mutant to evaluate the function of CD28-B7 and CTLA4-B7 interactions in induction and effector phases of antitumor immunity. We report that B7-CD28 and B7-CTLA4 interactions promote tumor rejection. However, this is achieved by distinct mechanisms. B7-CD28 interaction enhances T-cell clonal expansion, though a role for this interaction in the effector phase cannot be ruled out. In contrast, B7-CTLA4 interaction enhances the CTL-mediated destruction of tumors, but not T-cell clonal expansion.

B7H costimulates clonal expansion of, and cognate destruction of tumor cells by, CD8(+) T lymphocytes in vivo

B7H/B7RP (hereby called B7H) is a new member of the B7 family of costimulatory molecules and interacts with inducible costimulatory molecule (ICOS). Its function for CD8 T cells has not been reported. We report here that expression of B7H on the tumor cells reduced tumorigenicity and induced immunity to subsequent challenge with parental tumor cells. The immune protection correlates with an enhanced cytotoxic T lymphocyte (CTL) response against P1A, the major tumor antigen expressed in the J558 tumor. To understand the mechanism of immune protection, we adoptively transferred transgenic T cells specific for tumor antigen P1A into mice that bore P1A-expressing tumors. We found that while the transgenic T cells divided faster in mice bearing the B7H(+) tumors, optimal B7H-induced clonal expansion of P1CTL required costimulation by B7-1 and B7-2 on the endogenous host antigen-presenting cells (APCs). Interestingly, when B7H(+) and B7H(-) tumors were coinjected, P1CTL selectively eliminated the B7H(+) tumor cells. Moreover, B7H expressed on the tumor cells made them highly susceptible to destruction by CTL in vivo, even if the CTL was administrated into mice with large tumor burdens. Tumors that recurred in the P1CTL-treated mice lost transfected B7H and/or H-2L(d), the class I molecule that presents the P1A peptide. Taken together, our results reveal that B7H costimulates clonal expansion of, and cognate destruction by CD8(+) T lymphocytes in vivo.