Anti-tumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant Friend erythroleukemia cells. VIII. Role of the immune system in the inhibition of visceral metastases

Anthrax toxins regulate pain signaling and can deliver molecular cargoes into ANTXR2+ DRG sensory neurons

Bacterial products can act on neurons to alter signaling and function. In the present study, we found that dorsal root ganglion (DRG) sensory neurons are enriched for ANTXR2, the high-affinity receptor for anthrax toxins. Anthrax toxins are composed of protective antigen (PA), which binds to ANTXR2, and the protein cargoes edema factor (EF) and lethal factor (LF). Intrathecal administration of edema toxin (ET (PA + EF)) targeted DRG neurons and induced analgesia in mice. ET inhibited mechanical and thermal sensation, and pain caused by formalin, carrageenan or nerve injury. Analgesia depended on ANTXR2 expressed by Na_v1.8⁺ or Advillin⁺ neurons. ET modulated protein kinase A signaling in mouse sensory and human induced pluripotent stem cell-derived sensory neurons, and attenuated spinal cord neurotransmission. We further engineered anthrax toxins to introduce exogenous protein cargoes, including botulinum toxin, into DRG neurons to silence pain. Our study highlights interactions between a bacterial toxin and nociceptors, which may lead to the development of new pain therapeutics.

The added value of type I interferons to cytotoxic treatments of cancer

Type I interferons (IFNs) exert anti-proliferative, antiviral and immunomodulatory activities. They are also involved in cell differentiation and anti-tumor defense processes. A growing body of literature indicates that the success of conventional chemotherapeutics, epigenetic drugs, targeted anticancer agents and radiotherapy (RT) relies, at least in part, on the induction of type I IFN signaling in malignant cells, tumor-infiltrating antigen presenting cells or other immune cells within lymphoid organs or blood. The mechanisms underlying type I IFN induction and the clinical consequences of these observations are only beginning to be elucidated. In the present manuscript, we reviewed the recent advances in the field and provided our personal view on the role of type I IFNs induced in the context of cytotoxic anticancer treatments and on its possible exploitation as a complement in cancer therapy.

IFN-λ cancer immunotherapy: new kid on the block

Interferon-lambda (IFN-λ) is a new IFN type, related to IFN-α, that is commonly used in the clinic. However, significant side effects accompanying IFN-α treatment limit enthusiasm for IFN-α. In this review, we discuss the current landscape of IFN-α use in oncology and describe the biologic characteristics of IFN-λ. IFN-λ offers unique advantages, including a more tumor cell selective targeting, lower off-target binding and an ability to generate both innate and adaptive immune responses. IFN-λ has also demonstrated therapeutic benefit in murine cancer models. IFN-λ may be used in clinic as a single agent or in combination with other immunotherapy agents, such as immune checkpoint inhibitors. Further clinical trials will be needed to fully elucidate the potential of this novel agent in oncology.

Consensus nomenclature for CD8+ T cell phenotypes in cancer

Whereas preclinical investigations and clinical studies have established that CD8⁺ T cells can profoundly affect cancer progression, the underlying mechanisms are still elusive. Challenging the prevalent view that the beneficial effect of CD8⁺ T cells in cancer is solely attributable to their cytotoxic activity, several reports have indicated that the ability of CD8⁺ T cells to promote tumor regression is dependent on their cytokine secretion profile and their ability to self-renew. Evidence has also shown that the tumor microenvironment can disarm CD8⁺ T cell immunity, leading to the emergence of dysfunctional CD8⁺ T cells. The existence of different types of CD8⁺ T cells in cancer calls for a more precise definition of the CD8⁺ T cell immune phenotypes in cancer and the abandonment of the generic terms "pro-tumor" and "antitumor." Based on recent studies investigating the functions of CD8⁺ T cells in cancer, we here propose some guidelines to precisely define the functional states of CD8⁺ T cells in cancer.

Antileukemia and antitumor effects of the graft-versus-host disease: a new immunovirological approach

In leukemic mice, the native host's explicit and well-defined immune reactions to the leukemia virus (a strong exogenous antigen) and to leukemia cells (pretending in their native hosts to be protected "self" elements) are extinguished and replaced in GvHD (graft-versus-host disease) by those of the immunocompetent donor cells. In many cases, the GvHD-inducer donors display genetically encoded resistance to the leukemia virus. In human patients only antileukemia and anti-tumor cell immune reactions are mobilized; thus, patients are deprived of immune reactions to a strong exogenous antigen (the elusive human leukemia-sarcoma retroviruses). The innate and adaptive immune systems of mice have to sustain the immunosuppressive effects of leukemia-inducing retroviruses. Human patients due to the lack of leukemiainducing retroviral pathogens (if they exist, they have not as yet been discovered), escape such immunological downgrading. After studying leukemogenic retroviruses in murine and feline (and other mammalian) hosts, it is very difficult to dismiss retroviral etiology for human leukemias and sarcomas. Since no characterized and thus recognized leukemogenic-sarcomagenic retroviral agents are being isolated from the vast majority of human leukemias-sarcomas, the treatment for these conditions in mice and in human patients vastly differ. It is immunological and biological modalities (alpha interferons; vaccines; adoptive lymphocyte therapy) that dominate the treatment of murine leukemias, whereas combination chemotherapy remains the main remission-inducing agent in human leukemias-lymphomas and sarcomas (as humanized monoclonal antibodies and immunotoxins move in). Yet, in this apparently different backgrounds in Mus and Homo, GvHD, as a treatment modality, appears to work well in both hosts, by replacing the hosts' anti-leukemia and anti-tumor immune faculties with those of the donor. The clinical application of GvHD in the treatment of human leukemias-lymphomas and malignant solid tumors remains a force worthy of pursuit, refinement and strengthening. Graft engineering and modifications of the inner immunological environment of the recipient host by the activation or administration of tumor memory T cells, selected Treg cells and natural killer (NKT) cell classes and cytokines, and the improved pharmacotherapy of GvHD without reducing its antitumor efficacy, will raise the value of GvHD to the higher ranks of the effective antitumor immunotherapeutical measures. Clinical interventions of HCT/HSCT (hematopoietic cell/stem cell transplants) are now applicable to an extended spectrum of malignant diseases in human patients, being available to elderly patients, who receive non-myeloablative conditioning, are re-enforced by post-transplant donor lymphocyte (NK cell and immune T cell) infusions and post-transplant vaccinations, and the donor cells may derive from engineered grafts, or from cord blood with reduced GvHD, but increased GvL/GvT-inducing capabilities (graft-versus leukemia/tumor). Post-transplant T cell transfusions are possible only if selected leukemia antigen-specific T cell clones are available. In verbatim quotation: "Ultimately, advances in separation of GvT from GvHD will further enhance the potential of allogeneic HCT as a curative treatment for hematological malignancies" (Rezvani, A.R. and Storb, R.F., Journal of Autoimmunity 30:172-179, 2008 (see in the text)). It may be added: for cure, a combination of the GvL/T effects with new targeted therapeutic modalities, as elaborated on in this article, will be necessary.

Dysregulation of the immune system caused by silica and asbestos

Silica and asbestos cause pneumoconioses known as silicosis and asbestosis, respectively, that are each characterized by progressive pulmonary fibrosis. While local effects of inhaled silica particles alter the function of alveolar macrophages and sequential cellular and molecular biological events, general systemic immunological effects may also evolve. One well-known health outcome associated with silica exposure/silicosis is an increase in the incidence of autoimmune disorders. In addition, while exposure to silica--in the crystalline form--has also been seen to be associated with the development of lung cancers, it remains unclear as to whether or not silicosis is a necessary condition for the elevation of silica-associated lung cancer risks. Since asbestos is a mineral silicate, it would be expected to also possess generalized immunotoxicological effects similar to those associated with silica particles. However, asbestos-exposed patients are far better known than silicotic patients for development of malignant diseases such as lung cancer and mesothelioma, and less so for the development of autoimmune disorders. With both asbestos and crystalline silica, one important dysregulatory outcome that needs to be considered is an alteration in tumor immunity that allows for silica- or asbestos- (or asbestos-associated agent)-induced tumors to survive and thrive in situ. In this review, the immunotoxicological effects of both silica and asbestos are presented and contrasted in terms of their abilities to induce immune system dysregulation that then are manifest by the onset of autoimmunity or by alterations in host-tumor immunity.

Gene expression profiling reveals similarities between the in vitro and in vivo responses of immune effector cells to IFN-alpha

PURPOSE

The precise molecular targets of IFN-alpha therapy in the context of malignant melanoma are unknown but seem to involve signal transducers and activators of transcription 1 signal transduction within host immune effector cells. We hypothesized that the in vitro transcriptional response of patient peripheral blood mononuclear cells (PBMC) to IFN-alpha would be similar to the in vivo response to treatment with high-dose IFN-alpha.

EXPERIMENTAL DESIGN

The gene expression profiles of PBMCs and immune cell subsets treated in vitro with IFN-alpha were evaluated, as were PBMCs obtained from melanoma patients receiving adjuvant IFN-alpha.

RESULTS

Twenty-seven genes were up-regulated in PBMCs from normal donors after treatment with IFN-alpha in vitro for 18 hours (>2-fold, P < 0.001). A subset of these genes (in addition to others) was significantly expressed in IFN-alpha-treated T cells, natural killer cells, and monocytes. Analysis of gene expression within PBMCs from melanoma patients (n = 13) receiving high-dose IFN-alpha-2b (20 MU/m(2) i.v.) revealed significant up-regulation (>2-fold) of 21 genes (P < 0.001). Also, the gene expression profile of in vitro IFN-alpha-stimulated patient PBMCs was similar to that of PBMCs obtained from the same patient after IFN-alpha therapy.

CONCLUSIONS

This report is the first to describe the transcriptional response of T cells, natural killer cells, and monocytes to IFN-alpha and characterize the transcriptional profiles of PBMCs from melanoma patients undergoing IFN-alpha immunotherapy. In addition, it was determined that microarray analysis of patient PBMCs after in vitro stimulation with IFN-alpha may be a useful predictor of the in vivo response of immune cells to IFN-alpha immunotherapy.

STAT1-dependent and STAT1-independent gene expression in murine immune cells following stimulation with interferon-alpha

PURPOSE

The precise molecular targets of interferon-alpha (IFN-alpha) therapy of melanoma are unknown but likely involve signal transducer and activator of transcription 1 (STAT1) signal transduction within host immune effector cells. We hypothesized that microarray analysis could be utilized to identify candidate molecular targets important for mediating the anti-tumor effect of exogenously administered IFN-alpha.

EXPERIMENTAL METHODS

To identify the STAT1-dependent genes regulated by IFN-alpha, the gene expression profile of splenocytes from wild type (WT) and STAT1(-/-) mice was characterized.

RESULTS

This analysis identified 30 genes that required STAT1 signal transduction for optimal expression in response to IFN-alpha (p < 0.001). These genes include granzyme b (Gzmb), interferon regulatory factor 7 (Irf7), Fas death domain-associated protein (Daxx), and lymphocyte antigen 6 complex, locus C (Ly6c). The expression of 20 genes was found to be suppressed in the presence of STAT1 including chemokine ligand 2 (Ccl2), Ccl5, and Ccl7. Nineteen genes were significantly upregulated in murine splenocytes following treatment with IFN-alpha regardless of the presence of STAT1 including CD86, lymphocyte antigen 6 complex, locus A (Ly6a), and Tap binding protein (Tapbp). The expression of representative IFN-responsive genes was confirmed at the transcriptional level by Real Time PCR.

CONCLUSION

This report is the first to demonstrate that STAT1-mediated signal transduction plays a major role in the transcriptional response of murine immune cells to IFNalpha.

The antitumor effects of interferon: A personal history

Early experiments showed that administration of mouse interferon preparations inhibited the development of viral-induced or spontaneous viral associated leukemias in mice. Interferon alpha/beta was also shown to inhibit the growth of transplantable tumors of different origins in all strains of mice tested. The finding that interferon alpha/beta inhibited the growth of sublines of tumors selected for resistance to interferon alpha/beta indicated the role of interferon induced host mechanisms in the antitumor effects observed. The different host antitumor mechanisms and especially the interaction of interferon alpha/beta with the immune system have been briefly discussed. Injection of mice with a neutralizing antibody to interferon alpha/beta demonstrated the essential role of endogenous interferon alpha/beta in the defense of the mouse against the development of syngeneic, allogeneic and xenogeneic tumors.

Endogenous type I interferons as a defense against tumors

We have reviewed the experimental results which indicate that endogenous type I interferon (IFN) present either constitutively or possibly induced by the tumor plays an important role in limiting the development of transplantable tumors in mice. Thus, treatment with potent polyclonal neutralizing antibodies to IFN alpha/beta markedly enhanced the subcutaneous growth, invasiveness and metastases of xenogeneic tumor cells (uninfected or infected with RNA or DNA viruses) in athymic nude mice; enhanced the intraperitoneal transplantability of six different syngeneic murine tumors in three strains of immunocompetent mice; and completely abrogated the resistance of allogeneic C57Bl/6 (H-2(b)) or C3H (H-2(k)) mice to the multiplication of Friend erythroleukemia cells (H-2(d)) in the liver and spleen resulting in the death of most mice. The mechanisms by which mice respond to the injection of relatively few tumor cells appear to be multiple, to depend on the site of tumor growth, to occur early and prior to an immunologic response. Endogenous type I IFN appears to constitute an essential component of these defense mechanisms enabling the host to restrict tumor growth.

Interferon-alpha in tumor immunity and immunotherapy

Interferon-alpha (IFN-alpha) is a pleiotropic cytokine belonging to type I IFN, currently used in cancer patients. Early studies in mouse tumor models have shown the importance of host immune mechanisms in the generation of a long-lasting antitumor response to type I IFN. Recent studies have underscored new immunomodulatory effects of IFN-alpha, including activities on T and dendritic cells, which may explain IFN-induced tumor immunity. Reports on new immune correlates in cancer patients responding to IFN-alpha represent additional evidence on the importance of the interactions of IFN-alpha with the immune system for the generation of durable antitumor response. This knowledge, together with results from studies on genetically modified tumor cells expressing IFN-alpha, suggest novel strategies for using these cytokines in cancer immunotherapy and in particular the use of IFN-alpha as an immune adjuvant for the development of cancer vaccines.

Oromucosal interferon therapy: marked antiviral and antitumor activity

Oromucosal administration of murine interferon-alpha/beta (IFN-alpha/beta) or individual recombinant species of murine IFN-alpha, IFN-beta, or IFN-gamma or recombinant human IFN-alpha1-8, which is active in the mouse, exerted a marked antiviral activity in mice challenged systemically with a lethal dose of encephalomyocarditis virus (EMCV), vesicular stomatitis virus (VSV), or varicella zoster virus (VZV). The effects observed were dose dependent and similar in magnitude to those observed following parenteral administration of the same dose of IFN. No antiviral activity was observed after oromucosal administration of murine IFN-alpha/beta in animals in which the IFN receptor had been inactivated by homologous recombination. In contrast to parenteral treatment, oromucosal IFN therapy was found to be ineffective when IFNs were administered before virus infection. Oromucosal administration of IFN-alpha also exerted a marked antitumor activity in mice injected i.v. with highly malignant Friend erythroleukemia cells or other transplantable tumors, such as L1210 leukemia, which has no known viral etiology, the EL4 tumor, or the highly metastatic B16 melanoma. These results show that high doses of IFN can be administered by the oromucosal route apparently without ill effect, raising the possibility that the oromucosal route will prove to be an effective means of administering high doses of IFN that are clinically effective but poorly tolerated.

Importance of cyclophosphamide-induced bystander effect on T cells for a successful tumor eradication in response to adoptive immunotherapy in mice

Cyclophosphamide (CTX) increases the antitumor effectiveness of adoptive immunotherapy in mice, and combined immunotherapy regimens are now used in some clinical trials. However, the mechanisms underlying the synergistic antitumor responses are still unclear. The purpose of this study was (a) to evaluate the antitumor response to CTX and adoptive immunotherapy in mice bearing four different syngeneic tumors (two responsive in vivo to CTX and two resistant); and (b) to define the mechanism(s) of the CTX-immunotherapy synergism. Tumor-bearing DBA/2 mice were treated with a single injection of CTX followed by an intravenous infusion of tumor-immune spleen cells. In all the four tumor models, a single CTX injection resulted in an impressive antitumor response to the subsequent injection of spleen cells from mice immunized with homologous tumor cells independently of the in vivo response to CTX alone. Detailed analysis of the antitumor mechanisms in mice transplanted with metastatic Friend leukemia cells revealed that (a) the effectiveness of this combined therapy was dependent neither on the CTX-induced reduction of tumor burden nor on CTX-induced inhibition of some putative tumor-induced suppressor cells; (b) the CTX/immune cells' regimen strongly protected the mice from subsequent injection of FLC, provided the animals were also preinoculated with inactivated homologous tumor together with the immune spleen cells; (c) CD4(+) T immune lymphocytes were the major cell type responsible for the antitumor activity; (d) the combined therapy was ineffective in mice treated with antiasialo-GM1 or anti-IFN-alpha/beta antibodies; (e) spleen and/ or bone marrow cells from CTX-treated mice produced soluble factors that assisted in proliferation of the spleen cells. Altogether, these results indicate that CTX acts via bystander effects, possibly through production of T cell growth factors occurring during the rebound events after drug administration, which may sustain the proliferation, survival, and activity of the transferred immune T lymphocytes. Thus, our findings indicate the need for reappraisal of the mechanisms underlying the synergistic effects of CTX and adoptive immunotherapy, and may provide new insights into the definition of new and more effective strategies with chemotherapy and adoptive immunotherapy for cancer patients.

Cytokines in animal models of cancer

Cytokines are a complex family of mediators that play a wide role in development, immunity, inflammation and tissue repair. Their use in therapy is still in its infancy and animal models have a key role to play in optimizing doses and schedules. Whilst xenogeneic and syngeneic transplantable systems have traditionally been used to look at the effects of cytokines in tumour models, oncogene transgenic mice prone to develop cancer, may now have a role to play. Moreover, gene therapy has allowed the investigation of ectopically expressed high and continuous levels of cytokines. We will attempt to review the literature on the effect of cytokines and their combinations in these models of cancer.

Cure of mice with established metastatic friend leukemia cell tumors by a combined therapy with tumor cells expressing both interferon-alpha 1 and herpes simplex thymidine kinase followed by ganciclovir

Transduction of the murine interferon-alpha (IFN-alpha) gene into various malignant mouse tumor cells has resulted in the loss of tumorigenicity and an acquired capacity to induce long-lasting antitumor immunity following their injection into immunocompetent syngeneic mice. In the present study, we investigated the effectiveness of IFN-alpha-producing tumor cells in the therapy of mice with established mouse tumors. In DBA/2 mice bearing subcutaneous (s.c.) Friend erythroleukemia cell (FLC) tumors, we found that to achieve some antitumor response (i) it was necessary to inject high numbers of IFN-alpha-producing FLC, which occasionally lead to the formation of slowly growing tumors; and, that (ii) repeated injections of irradiated IFN-alpha-FLC did not result in any antitumor effect. The therapeutic potential of IFN-alpha-producing FLC rendered sensitive to ganciclovir (GCV), by transfer of the herpes simplex virus thymidine kinase (tk) gene, was investigated. Complete tumor rejection and cure was observed in > or = 70% of the animals after injection of high numbers (10(7)) of IFN-alpha-producing tk-expressing tumor cells followed 4 days later by repeated GCV treatments, whereas only a slight increase in survival time was obtained after administration of control tk-expressing tumor cells (not producing IFN) and GCV. Tumor rejection was associated with a dramatic destruction of tumor tissue and with the subsequent development of a potent and long-lasting antitumor immunity. No therapeutic effect was observed in immunosuppressed nude mice. These data indicate that this approach may represent an effective and safe therapeutic strategy for antitumor cytokine gene therapy.

The essential role of endogenous IFN alpha/beta in the anti-metastatic action of sensitized T lymphocytes in mice injected with Friend erythroleukemia cells

Adoptive transfer of splenic T lymphocytes from DBA/2 mice immunized against Friend erythroleukemia cells (FLC) inhibited the development of visceral metastases and increased the survival time of DBA/2 mice challenged i.v. with parental FLC 24 hr to 2 months later. Immune spleen cells were ineffective in mice pre-treated with potent neutralizing antibody to mouse IFN alpha/beta (but not to IFN gamma), demonstrating the essential participation of endogenous IFN alpha/beta in the inhibitory action of immune T lymphocytes against FLC metastases. These findings suggest that the reported inability of immune T lymphocytes to exert an anti-FLC effect in immunodeficient DBA/2 mutant beige (bg/bg) mice (unless these mice had also been treated with IFN alpha/beta), may have been due to lower levels of endogenous IFN alpha/beta in DBA/2 bg/bg mice than in normal DBA/2+/bg mice. Experimental results in support of this hypothesis are presented.

Interferon-alpha inhibits erythropoietin-induced proliferation, but not differentiation, and restricts erythroleukemia development

The immature erythroid cell line J2E responds to erythropoietin (Epo) by proliferating and terminally differentiating into hemoglobin-synthesizing red blood cells. These cells produce a rapid, fatal erythroleukemia in mice characterized by hepatosplenomegaly and severe anemia. The aim of this study was to investigate the effects of murine interferons-alpha (MuIFN-alpha) on J2E cells in vitro and in vivo. Here we show that in culture MuIFN-alpha inhibited the Epo-induced proliferation of J2E cells but did not interfere with differentiation. When mice with J2E erythroleukemias were treated with MuIFNs in vivo, an extension of their life span was observed. Moreover, numerous necrotic lesions of infiltrating leukemic cells were detected in the spleens of these mice. Finally, ex vivo treatment of leukemic bone marrow cells with Epo and MuIFNs delayed mortality even further. It was concluded that MuIFNs (1) suppressed the proliferation of J2E cells in vitro but did not affect Epo-induced differentiation, and (2) inhibited the progress of erythroleukemias, especially in combination with Epo.

Interferon-alpha/beta can impede development of carcinogen-induced squamous-cell tumors in the esophagus of C57B1 mice

The effect of treatment with murine interferon-alpha/beta preparations on diethylnitrosamine-induced squamous-cell tumors in the esophagus of C57B1 mice was investigated. Diethylnitrosamine was administered in the drinking water for 18 weeks. Interferon was given intraperitoneally during the same 18 weeks or from the end of the period of carcinogen exposure until termination of the experiment. In mice given interferon and diethylnitrosamine synchronously, a significantly lower tumor index (number of tumors/cm of esophageal mucosa) was observed as compared to all control groups. Treatment with interferon after the administration of the carcinogen was terminated had no effect on the appearance of tumors. These data suggest that interferon therapy can exert certain effects on carcinogenesis.

Role of interferons and other cytokines in the regulation of the immune response

Cytokines represent the major factors involved in the communication between T cells, macrophages and other immune cells in the course of an immune response to antigens and infectious agents. A number of studies on mouse and human T helper (Th) clones have recently provided extensive evidence for the existence of different activities exhibited by Th cells (called Th1 and Th2), which was apparently inferred from the profile of cytokine secretion. The Th1-type immune response is generally associated with IgG2a production and the development of cellular immunity, the Th2-type response with IgE production, eosinophils and mast cell production. This review focuses on the role of different cytokines produced by macrophages (especially interferons (IFNs), TNF-alpha, IL-10 and IL-12) or T cells (IFNs, IL-2, IL-4, IL-10, IL-13 and TGF-beta) in macrophage-T cell interactions and the cytokine relevance in the differentiation of Th cells towards the Th1 or Th2 type of immune response. Th1-derived cytokines (IFN-gamma, IL-2, TNF-alpha) favor macrophage activation, whereas the Th2 cytokines (IL-4, IL-10, IL-13) exhibit suppressive activities on macrophage functions. A key role in the differentiation towards the Th1-type response is now attributed to IL-12, a recently described cytokine produced mainly by macrophages. Its production can be upregulated by IFN-gamma and is inhibited by IL-10 and IL-4. All this emphasizes the importance of macrophage-cytokine interactions in determining the type of immune response. This article also aims to review recent data concerning the roles of IFNs alpha/beta (type I) and IFN-gamma (type II) in the regulation of the immune response. While there is much information on the regulatory effects of IFN-gamma (also called "immune IFN") on the immune response, little is so far known of the role of type I IFNs. These cytokines, originally described as simple antiviral substances, are now taken to be important regulators of the immune response. Recent data indicate that these molecules (especially IFNs-alpha) specifically promote the differentiation towards the Th1-type response. The stimulatory effects of IFN-alpha on the generation of the Th1-type response may be involved in its therapeutic effects in some human diseases, including early AIDS, hypereosinophilia and certain tumors.(ABSTRACT TRUNCATED AT 400 WORDS)

IFN-alpha 1 gene transfection completely abolishes the tumorigenicity of murine B16 melanoma cells in allogeneic DBA/2 mice and decreases their tumorigenicity in syngeneic C57BL/6 mice

The murine B16 melanoma (H-2b) was transfected with a retroviral vector containing the mouse IFN-alpha 1 gene. IFN-alpha 1-transfected cells produced IFN-alpha in vitro and exhibited an altered phenotype characterized by a decreased rate of multiplication, enhanced expression of H-2 antigens, an antiviral state to VSV, and decreased pigmentation. Control and IFN-alpha 1-transfected cells were tested for their ability to grow in syngeneic (H-2b) C57Bl/6 and allogeneic (H-2d) DBA/2 mice. IFN-alpha 1-producing B16 clones were less tumorigenic after s.c., i.p., and i.v. routes of injection than IFN-non-producer B16 clones in syngeneic C57Bl/6 mice. IFN-alpha 1-producing B16 cells were, however, totally rejected by allogeneic DBA/2 mice regardless of the routes and inocula tested, while control B16 cells grew in and killed DBA/2 mice. The total rejection of IFN-alpha 1-transfected B16 cells in allogeneic mice appeared to be dependent on T cells as these cells grew in DBA/2 nude mice. Incubation of IFN-alpha-producing clones with anti-mouse IFN-alpha/beta prior to injection into C57Bl/6 mice did not enhance their tumorigenicity. Likewise, injection of C57Bl/6 and DBA/2 mice with antibody to IFN-alpha/beta did not enhance the tumorigenicity of IFN-alpha 1-transfected cells. C57Bl/6 mice immunized with irradiated IFN-alpha 1 cells were only slightly protected against a subsequent challenge with parental B16 cells. In contrast, DBA/2 mice immunized with irradiated IFN-alpha 1 cells exhibited tumor-specific, long-lasting immunity to subsequent challenge with parental B16 cells.

Induction in interferon-alpha/beta-treated hepatocytes of the inhibitor of the multiplication of IFN-alpha/beta-resistant Friend leukemia cells

We reported previously that interferon-alpha/beta (IFN-alpha/beta)-treated hepatocytes in culture released a soluble factor(s) that suppressed the multiplication of an INF-alpha/beta-resistant clone of Friend leukemia cells (FLCs). To characterize the factor(s) further, we first examined the possibility that products of nonparenchymal cells (NPCs) included in small number in the hepatocyte cultures were involved in the inhibitory activity. We prepared cultures of purified adherent NPCs, mostly Kupffer cells, and sinusoidal endothelial cells, and culture supernatants of NPCs pretreated with IFN-alpha/beta were tested for the inhibitory activity for FLC multiplication. IFN did not induce any inhibitory activity in NPC cultures, whereas LPS-stimulated NPCs cultivated in parallel released several inhibitory factors including tumor necrosis factor-alpha (TNF-alpha). To explore the possibility that IFN augmented the release of hepatocyte cytosolic proteins, including arginase, we compared the inhibitory activity in culture supernatant of IFN-treated hepatocytes with that found in hepatocyte extract by anion-exchange chromatography. The IFN-induced inhibitory activity was eluted at relatively high salt concentration as a single peak, while the inhibitory activity in hepatocyte extract was co-eluted with arginase at low salt concentration. These results suggested that IFN induced production by hepatocytes of an inhibitor of FLC multiplication.

Enhanced in vivo sensitivity to interferon with in vitro resistant B16 tumor cells in mice

Mouse B16 melanoma cells rapidly develop resistance to the antiproliferative effects of interferon alpha (IFN alpha) and interferon beta (IFN beta) when they are exposed to the interferons in vitro. This resistance was characterized to be non-genetic and dose-dependent, and does not alter other IFN-induced effects such as antiviral effects and elevation of 2',5'-oligoadenylate synthetase activity in IFN-treated cells. The study of these IFN-resistant cells has been extended to an in vivo tumor model. Resistance, if it occurred in vivo, did not adversely affect the survival of IFN-treated mice. Further, IFN-treated mice inoculated with B16 cells that were resistant in vitro (B16 alpha res cells) survived significantly longer than IFN-treated mice inoculated with B16 cells that were sensitive in vitro. The IFN-treated B16 alpha res-inoculated mice had a significantly higher cure rate as well. The prolonged survival of the mice bearing B16 alpha res cell tumors did not seem to be caused by the slower growth rate of the B16 alpha res cells, since experiments performed with a tenfold higher B16 alpha res cell inoculum and a tenfold lower B16 cell inoculum did not show any change in the survival pattern. It is clear that in vitro resistant B16 alpha res cells are more sensitive to antitumor effects induced by IFN in vivo than in vitro sensitive B16 cells.

Interaction of IFN alpha/beta with host cells essential to the early inhibition of Friend erythroleukemia visceral metastases in mice

We have previously shown that an intact immune system was essential to the increase in survival time of IFN-alpha/beta-treated mice injected i.v. with an IFN-alpha/beta-resistant line of Friend erythroleukemia cells (FLC) highly metastatic to the liver and spleen. Here, we have investigated the early interactions of IFN alpha/beta with host cells prior to the development of the immune response. IFN alpha/beta treatment resulted in 50- to 100-fold inhibition of FLC multiplication in the liver and spleen of normal DBA/2 mice shortly after tumor inoculation, as evaluated by colony formation in agarose. IFN treatment was far less effective in inhibiting the multiplication of FLC in the livers of NK-cell-deficient DBA/2 beige mice, or in immunocompetent DBA/2 mice treated with antibody to asialo GMI, or silica, or in mice subjected to sub-lethal irradiation. Injection of antibody to CD4 or CD8 did not affect the early inhibitory action of IFN alpha/beta on FLC multiplication but did decrease survival time. Light- and electron-microscope examination of the livers of IFN-treated, FLC-injected mice confirmed the early inhibition of FLC multiplication in the liver and spleen. Our results indicate that IFN alpha/beta inhibits the development of FLC visceral metastases by acting first on host cells, such as NK cells and macrophages, and then continues to act in consort with the developing immune response.

Successful immunotherapy of the highly metastatic murine ESb lymphoma with sensitized CD8+ T cells and IFN-alpha/beta

Daily IFN-alpha/beta therapy was totally ineffective in inhibiting the development of visceral metastases in DBA/2 mice injected i.v. with the ESb lymphoma regardless of the number of tumor cells injected. The finding that IFN-alpha/beta therapy increased the survival time of ESb-immunized mice rechallenged with ESb cells suggested that cooperation between the immune system and IFN-alpha/beta was important. Adoptive transfer of Esb-immune spleen cells (but not normal cells) together with IFN-alpha/beta treatment did inhibit the development of ESb metastases in immunocompetent DBA/2 mice. Either treatment alone was ineffective. The anti-metastatic effect was specific for the ESb lymphoma as spleen cells from ESb-immunized mice together with IFN-alpha/beta treatment did not inhibit the development of metastases in mice challenged with IFN-alpha/beta-resistant 3C18 FLC. Depletion of CD8+ T cells (but not CD4+ T cells or B lymphocytes) prior to transfer eliminated the protective effect of ESb-immune splenocytes in IFN-alpha/beta-treated mice. As few as 1 x 10(6) ESb-immune spleen cells highly enriched for CD8+ cells increased the survival time of IFN-alpha/beta-treated ESb-challenged DBA/2 mice. The combined therapy of ESb-specific immune cells and IFN-alpha/beta resulted in long-term immunity to this tumor.

Sensitized T lymphocytes render DBA/2 beige mice responsive to IFN alpha/beta therapy of Friend erythroleukemia visceral metastases

Interferon alpha/beta (IFN alpha/beta) is highly effective in inhibiting the development of Friend erythroleukemia cell (FLC) visceral metastases in DBA/2 mice injected intravenously (i.v.) with FLC, but does not protect FLC-injected DBA/2 beige (bg/bg) mice. Use of IFN alpha/beta-resistance FLC indicated that IFN was acting through host mechanisms in DBA/2 mice and thus pointed to a defect in some host mechanism in bg/bg mice essential for IFN's anti-metastatic action. We undertook experiments to restore in bg/bg mice the marked anti-FLC metastatic effect of IFN alpha/beta observed in DBA/2 and +/bg mice. Adoptive transfer of spleen cells from normal syngeneic mice to IFN-treated bg/bg mice was ineffective, but the transfer of splenic T lymphocytes from FLC-immunized DBA/2 or +/bg mice markedly increased the survival time of FLC-injected bg/bg mice provided that these mice were also treated with IFN alpha/beta. Neither treatment alone resulted in an increase in survival time. As few as 1 x 10(7) immune spleen cells were effective in IFN-treated FLC-injected bg/bg mice. The T-cell immune response to FLC of bg/bg mice was diminished compared with that of +/bg mice. Likewise, only combination therapy of immune spleen cells and IFN alpha/beta resulted in an increased survival time of ESb-lymphoma-injected bg/bg mice. Our results indicate the essential participation both of T-cell-mediated immune mechanisms and of IFN alpha/beta in the inhibition of FLC visceral metastases.

Effects of interferons and other cytokines on tumors in animals: a review

The term cytokine describes a group of protein cell regulators involved in the control of cell growth and differentiation in embryogenesis, immunity and inflammation. They are of low molecular weight, are produced locally, and act in an autocrine or paracrine manner. In the past decade their use as cancer therapy has become a reality. Thirty years ago mice were treated with the antiviral protein interferon (IFN) which not only produced a reduction in the incidence of virus-induced tumors but also slowed the development of transplantable tumors. This was one of the first indications that cytokines can be negative regulators of cell growth. Here we outline current knowledge of the actions of IFNs and other cytokines in animal models, and draw parallels with clinical trials to illustrate the invaluable nature of this preclinical and mechanistic work.

Synergistic anti-tumor effects of combined IL-1/IFN-alpha/beta therapy in mice injected with metastatic Friend erythroleukemia cells

Peritumoral injection of relatively low doses of either mouse interferon (IFN)-alpha/beta (10,000-20,000 units/injection) or of recombinant human interleukin-1 (IL-1) beta (125-250 ng/injection) in mice transplanted s.c. with Friend erythroleukemia cells (FLC) resulted in some inhibition of primary tumor growth, inhibition of liver and splenic metastases and increased survival time. A synergistic anti-tumor effect was observed in mice injected with both IL-1 and IFN-alpha/beta. Highly purified mouse IFN-beta also exerted a synergistic anti-tumor effect when combined with IL-1-beta in mice injected with FLC. The anti-tumor action of IL-1/IFN was markedly reduced in mice treated with antibodies to CD4 antigens. Antibodies to asialo-GM1 also diminished the anti-tumor effect by the combined cytokine treatment. The combined IL-1/IFN therapy was effective in NK-deficient bg/bg mice, although the extent of the anti-tumor response in these mice was less than that observed in bg/+mice.

Host humoral and cellular immune mechanisms in the continued suppression of Friend erythroleukemia metastases after interferon alpha/beta treatment in mice

DBA/2 mice were injected intravenously with 2 x 10(6) 3C18 Friend erythroleukemia cells (FLC), a cell line resistant to interferon alpha/beta (IFN-alpha/beta). Although daily administration of mouse IFN-alpha/beta markedly increased the mean survival time, most IFN-treated mice continued to harbor FLC in different organs. To investigate the mechanisms responsible for this persistent suppression of FLC growth in IFN-treated mice, we undertook a series of adoptive transfer experiments with sera and spleen cells. Sera from FLC-injected, IFN-treated mice were very effective in conferring protection on DBA/2 mice even when injected systemically (intravenously) 18-24 h before intravenous challenge with FLC. These sera also exhibited antitumor activity when injected subcutaneously or intraperitoneally together with FLC. The protective factor in serum was shown to be an immunoglobulin. FLC-injected, IFN-treated mice developed antibodies to FLC demonstrable by radioimmunoassay and complement-dependent cytotoxicity. Sera from these mice recognized a specific 65-kD FLC membrane antigen(s) not detectable on membrane extracts from RBL-5 or ESb tumor cells, or on normal spleen cells. FLC-injected, IFN-treated mice also developed a specific cellular response demonstrable by transfer of protection with spleen cells injected intravenously or subcutaneously. Analysis of the responsible spleen cell populations indicated that the effector cells were neither T nor B cells. These results demonstrating the importance of host humoral and cellular immune mechanisms in the persistent suppression of FLC in IFN-treated mice may be relevant to the use of IFN-alpha/beta in patients in whom tumors may regress and tumor cells may then remain latent for extended periods of time.

Human immunodeficiency virus (HIV)-infected tumor xenografts as an in vivo model for antiviral therapy: role of alpha/beta interferon in restriction of tumor growth in nude mice injected with HIV-infected U937 tumor cells

The host factors involved in the restriction of tumor growth were studied in nude mice transplanted with a cloned line of chronically human immunodeficiency virus (HIV)-infected U937 cells. HIV-infected and uninfected U937 cells exhibited the same growth patterns in culture. However, HIV-infected cells were not tumorigenic when injected subcutaneously in nude mice, whereas large solid tumors were observed in mice injected with uninfected U937 cells. Injection of nude mice with antibody to alpha/beta interferon (IFN-alpha/beta) enabled HIV-infected U937 cells to grow progressively in approximately 90 to 100% of mice. HIV-infected U937 cells formed solid tumors in the majority (60 to 90%) of either immunosuppressed (splenectomized, irradiated, and anti-asialo-GM1-treated) or genetically immunodeficient (bg/nu/xid) nude mice. In mice treated with antibodies to IFN-alpha/beta with established HIV-positive tumors, a direct correlation was found between p24 antigenemia and tumor size. Treatment of established HIV-positive U937 cell tumors with human IFN-alpha or mouse IFN-alpha/beta resulted in a clear-cut inhibition of both tumor growth and p24 HIV antigenemia. In contrast, treatment with tumor necrosis factor alpha markedly inhibited tumor growth but did not significantly decrease serum p24 levels. 3'-Azido-3'-deoxythymidine treatment did not affect either tumor growth or the levels of serum p24 antigen. These data indicate that endogenous IFN-alpha/beta is a crucial factor in the restriction of both tumor growth and p24 antigenemia in mice injected with HIV-infected tumor cells. Moreover, the results suggest that the development of HIV-1 p24 antigenemia in athymic immunosuppressed mice may represent an interesting in vivo model for anti-HIV therapy.