Use of Gene Therapy in a Subcutaneous Murine Model of Lung Cancer

OBJECTIVE: To assess the effectiveness of in vivo gene therapy to treat subcutaneous tumors generated from murine lung cancer cells. MATERIAL AND METHODS: C57BL/6 mice received subcutaneus injections of 5×105 cells from the murine Lewis lung cancer cell line. By 10 days, subcutaneous tumors of approximately 5 mm diameter were formed. At that point, treatment was provided by intratumor injection of a replication-defective recombinant adenovirus carrying the gene for thymidine kinase (AdCMV-Tk) or interleukin (IL) 12 (AdCMV-IL12), or by injection of syngeneic dendritic cells previously transduced with adenovirus containing the IL-12 gene (DC-IL12). Control groups were treated with saline or adenovirus containing the gene for β-galactosidase (AdCMV-LacZ), which functions as a reporter gene and does not have a therapeutic effect. The number of animals in each group ranged from 14 to 25 in experiments using adenovirus and from 10 to 12 in experiments using dendritic cells. Tumor size was followed for 3 weeks in the case of treatment with adenovirus and 4 weeks for treatment with dendritic cells. RESULTS: A significant reduction in subcutaneous tumor growth was observed in the groups treated with AdCMVTk, AdCMV-IL12, and DC-IL12 compared with control groups treated with saline or AdCMV-LacZ. The difference was statistically significant from day 7 of treatment in the AdCMV-Tk group, from day 9 in the AdCMV-IL12 group, and from day 10 in the DC-IL12 group, and in all cases it was maintained until the end of the follow-up period. CONCLUSIONS: Gene therapy with AdCMV-Tk, AdCMVIL12, or DC-IL12 is effective in our model of subcutaneous tumors arising from cells of the Lewis lung cancer cell line. The treatment leads to a significant reduction in tumor growth compared with control groups

Effective tumor immunotherapy: start the engine, release the brakes, step on the gas pedal,...and get ready to face autoimmunity

Cellular immune responses can destroy cancer cells, achieving the cure of experimental malignancies. An expanding wealth of knowledge on the molecular basis of how to prime and amplify a T cell response has fueled a number of strategies successful at treating established tumors (rather than merely preventing tumor grafting). The most efficacious approaches operate at different stages, including: 1) priming the immune response using tumor antigen-expressing dendritic cells or tumor cells transfected with genes that render them immunogenic, 2) sustaining and amplifying immunity using agonistic monoclonal antibodies against costimulatory molecules or immune-potentiating cytokines, and 3) eliminating mechanisms that self-regulate the strength of the immune response, such as inhibitory receptors or regulatory T cells. A rational combination of such approaches holds great hope for cumulative and synergistic effects, but there is also evidence that they can open the flood-gates for unwanted inflammatory reactions. The next decade can be envisioned as the time when the first reproducibly efficacious combination regimes for cancer immunotherapy will become available and widely used in the clinic, as clinicians learn the best strategies and try to harness their potentially damaging effects

Clinical implications of antigen transfer mechanisms from malignant to dendritic cells: Exploiting cross-priming

Expansion and activation of cytolytic T lymphocytes bearing high-affinity T-cell receptors specific for tumor antigens is a major goal of active cancer immunotherapy. Physiologically, T cells receive promitotic and activating signals from endogenous professional antigen-presenting cells (APC) rather than directly from malignant cells. This phenomenon fits with the broader concept of cross-presentation that earlier was demonstrated for minor histocompatibility and viral antigens. Many mechanisms have been found to be capable of transferring antigenic material from malignant cells to APC so that it can be processed and subsequently presented by MHC class I molecules expressed on APC. Dendritic cells (DC) are believed to be the most relevant APC mediating cross-presentation because they can take up antigens from apoptotic, necrotic, and even intact tumor cells. There exist specific molecular mechanisms that ensure this transfer of antigenic material: 1) opsonization of apoptotic bodies; 2) receptors for released heat shock proteins carrying peptides processed intracellularly; 3) Fc receptors that uptake immunocomplexes and immunoglobulins; and 4) pinocytosis. DC have the peculiar capability of reentering the exogenously captured material into the MHC class I pathway. Exploitation of these pieces of knowledge is achieved by providing DC with complex mixtures of tumor antigens ex vivo and by agents and procedures that promote infiltration of malignant tissue by DC. The final outcome of DC cross-presentation could be T-cell activation (cross-priming) but also, and importantly, T-cell tolerance contingent upon the activation/maturation status of DC. Artificial enhancement of tumor antigen cross-presentation and control of the immune-promoting status of the antigen-presenting DC will have important therapeutic implications in the near future

Potentiation of therapeutic immune responses against malignancies with monoclonal antibodies

Immunotherapeutic monoclonal antibodies (mAbs) can be defined as those that exert their functions by tampering with immune system cell molecules, causing an enhancement of antitumor immune responses. Some of these antibodies are agonistic ligands for surface receptors involved in the activation of lymphocytes and/or antigen-presenting cells, whereas others are antagonists of mechanisms that normally limit the intensity of immune reactions. Several mAbs of this category have been described to display in vivo antitumor activity in mouse models. Only anti–CTLA-4 (CD152) mAb has entered clinical trials, but the preclinical effects described for anti- CD40, anti-CD137 (4-1BB), anti-CD102 (intercellular adhesion molecule-2), and regulatory T cell-depleting mAbs should lead to their prompt clinical development. Their use in combination with immunizations against tumor antigens has been reported to be endowed with synergistic properties. This new group of antitumor agents holds promise for at least additive effects with conventional therapies of cancer and deserves intensive translational research

Improving efficacy of interleukin-12-transfected dendritic cells injected into murine colon cancer with anti-CD137 monoclonal antibodies and alloantigens

Intralesional administration of cultured dendritic cells (DCs) engineered to produce IL-12 by in vitro infection with recombinant adenovirus frequently displays eradicating efficacy against established subcutaneous tumors derived from the CT26 murine colon carcinoma cell line. The elicited response is mainly mediated by cytolytic T lymphocytes. In order to search for strategies that would enhance the efficacy of the therapeutic procedure against less immunogenic tumors, we moved onto malignancies derived from the inoculation of MC38 colon cancer cells that are less prone to undergo complete regression upon a single intratumoral injection of IL-12-secreting DCs. In this model, we found that repeated injections of such DCs, as opposed to a single injection, achieved better efficacy against both the injected and a distantly implanted tumor; that the use of semiallogeneic DCs that are mismatched in one MHC haplotype with the tumor host showed slightly better efficacy; and that the combination of this treatment with systemic injections of immunostimulatory anti-CD137 (4-1BB) monoclonal antibody achieved potent combined effects that correlated with the antitumor immune response measured in IFN-gamma ELISPOT assays. The elicited systemic immune response eradicates concomitant untreated lesions in most cases. Curative efficacy was also found against some tumors established for 2 weeks when these strategies were used in combination. These are preclinical pieces of evidence to be considered in order to enhance the therapeutic benefit of a strategy that is currently being tested in clinical trials. Supplementary Material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html

Anti-ICAM-2 monoclonal antibody synergizes with intratumor gene transfer of interleukin-12 inhibiting activation-induced T-cell death

PURPOSE: Systemic treatment with an anti-ICAM-2 monoclonal antibody (mAb; EOL4G8) eradicates certain established mouse tumors through a mechanism dependent on the potentiation of a CTL-mediated response. However, well-established tumors derived from the MC38 colon carcinoma cell line were largely refractory to this treatment as well as to intratumor injection of a recombinant adenovirus encoding interleukin-12 (IL-12; AdCMVIL-12). We sought to design combined therapy strategies with AdCMVIL-12 plus anti-ICAM-2 mAbs and to identify their mechanism of action. EXPERIMENTAL DESIGN: Analysis of antitumor and toxic effects were performed with C57BL/6 mice bearing established MC38 tumors. Anti-ovalbumin T-cell receptor transgenic mice and tumors transfected with this antigen were used for in vitro and in vivo studies on activation-induced cell death (AICD) of CD8(+) T cells. RESULTS: Combined treatment with various systemic doses of EOL4G8 mAb plus intratumor injection of AdCMVIL-12 induced complete regression of MC38 tumors treated 7 days after implantation. Unfortunately, most of such mice succumbed to a systemic inflammatory syndrome that could be prevented if IFN-gamma activity were neutralized once tumors had been rejected. Importantly, dose reduction of EOL4G8 mAb opened a therapeutic window (complete cure of 9 of 18 cases without toxicity). We also show that ICAM-2 ligation by EOL4G8 mAb on activated CTLs prevents AICD, thus extending IFN-gamma production. CONCLUSIONS: Combination of intratumor gene transfer of IL-12and systemic anti-ICAM-2 mAb display synergistic therapeutic and toxic effects. CTL life extension resulting from AICD inhibition by anti-ICAM-2 mAbs is the plausible mechanism of action

Enhancement of CD4 and CD8 immunity by anti-CD137 (4-1BB) monoclonal antibodies during hepatitis C vaccination with recombinant adenovirus

The induction of protective or therapeutic cellular immunity against hepatitis C virus (HCV) is a difficult goal. In a previous work we showed that immunization with a recombinant adenovirus encoding HCV-NS3 (RAdNS3) could partially protect mice from challenge with a vaccinia virus encoding HCV antigens. We sought to investigate whether systemic administration of an immunostimulatory monoclonal antibody directed against the lymphocyte surface molecule CD137 could enhance the immunity elicited by RAdNS3. It was found that treatment with anti-CD137 mAb after the administration of a suboptimal dose of RAdNS3 enhanced cytotoxic and T helper cell responses against HCV NS3. Importantly, the ability of RAdNS3 to induce protective immunity against challenge with a recombinant vaccinia virus expressing HCV proteins was markedly augmented. Thus, combination of immunostimulatory anti-CD137 mAb with recombinant adenoviruses expressing HCV proteins might be useful in strategies of immunization against HCV

Pancreatic cancer escape variants that evade immunogene therapy through loss of sensitivity to IFNgamma-induced apoptosis

Combined injections into experimental tumor nodules of adenovirus encoding IL-12 and certain chemokines are capable to induce immune-mediated complete regressions. In this study, we found that the combination of two adenoviruses, one encoding IL-12 and other MIP3alpha (AdCMVIL-12+AdCMVMIP3alpha) was very successful in treating CT-26-derived colon carcinomas. However, in experimental tumors generated from the pancreatic carcinoma cell line Panc02 such combined treatment induces 50% of macroscopic complete regressions, although local relapses within 1 week are almost constant. We derived cell lines from such relapsing tumors and found that experimental malignancies derived from their inoculum were not amenable to treatment in any case with AdCMVIL-12+AdCMVMIP-3alpha. Importantly, relapsing cell lines were insensitive to in vitro induction of apoptosis by IFNgamma, in clear contrast with the original Panc02 cells. Comparative analyses by cDNA arrays of relapsing cell lines versus wild-type Panc02 were performed revealing an important number of genes (383) whose expression levels were modified more than two-fold. These changes grouped in certain gene ontology categories should harbor the mechanistic explanations of the acquired selective resistance to IFNgamma

The immunotherapy potential of agonistic anti-CD137 (4-1BB) monoclonal antibodies for malignancies and chronic viral diseases

Pharmacological intervention on the immune system to achieve more intense lymphocyte responses has potential application in tumour immunology and in the treatment of chronic viral diseases. Immunostimulating monoclonal antibodies are defined as a new family of drugs that augment cellular immune responses. They interact as artificial ligands with functional proteins of the immune system, either activating or inhibiting their functions. There are humanized monoclonal antibodies directed to the inhibitory receptor CD152 (CTLA-4) that are being tested in clinical trials with evidence of antitumoural activity. As a drawback, anti-CTLA-4 monoclonal antibodies induce severe autoimmunity reactions in a fraction of the patients. Anti-CD137 monoclonal antibodies have the ability to induce potent immune responses mainly mediated by cytotoxic lymphocytes with the result of frequent complete tumour eradications in mice. Comparative studies in experimental models indicate that the antitumour activity of anti-CD137 monoclonal antibodies is superior to that of anti-CD152. CD137 (4-1BB) is a leukocyte differentiation antigen selectively expressed on the surface of activated T and NK lymphocytes, as well as on dendritic cells. Monoclonal antibodies acting as artificial stimulatory ligands of this receptor (anti-CD137 agonist antibodies) enhance cellular antitumoural and antiviral immunity in a variety of mouse models. Paradoxically, anti-CD137 monoclonal antibodies are therapeutic or preventive in the course of model autoimmune diseases in mice. In light of these experimental results, a number of research groups have humanized antibodies against human CD137 and early clinical trials are about to start

Low surface expression of B7-1 (CD80) is an immunoescape mechanism of colon carcinoma

Artificially enforced expression of CD80 (B7-1) and CD86 (B7-2) on tumor cells renders them more immunogenic by triggering the CD28 receptor on T cells. The enigma is that such B7s interact with much higher affinity with CTLA-4 (CD152), an inhibitory receptor expressed by activated T cells. We show that unmutated CD80 is spontaneously expressed at low levels by mouse colon carcinoma cell lines and other transplantable tumor cell lines of various tissue origins. Silencing of CD80 by interfering RNA led to loss of tumorigenicity of CT26 colon carcinoma in immunocompetent mice, but not in immunodeficient Rag-/- mice. CT26 tumor cells bind CTLA-4Ig, but much more faintly with a similar CD28Ig chimeric protein, thus providing an explanation for the dominant inhibitory effects on tumor immunity displayed by CD80 at that expression level. Interestingly, CD80-negative tumor cell lines such as MC38 colon carcinoma and B16 melanoma express CD80 at dim levels during in vivo growth in syngeneic mice. Therefore, low CD80 surface expression seems to give an advantage to cancer cells against the immune system. Our findings are similar with the inhibitory role described for the dim CD80 expression on immature dendritic cells, providing an explanation for the low levels of CD80 expression described in various human malignancies