Transforming growth factor-beta1 suppresses interleukin-15-mediated interferon-gamma production in human T lymphocytes

Migration and homeostasis of regulatory T cells in rheumatoid arthritis

Regulatory T (T_reg) cells are garnering increased attention in research related to autoimmune diseases, including rheumatoid arthritis (RA). They play an essential role in the maintenance of immune homeostasis by restricting effector T cell activity. Reduced functions and frequencies of T_reg cells contribute to the pathogenesis of RA, a common autoimmune disease which leads to systemic inflammation and erosive joint destruction. T_reg cells from patients with RA are characterized by impaired functions and by an altered phenotype. They show increased plasticity towards Th17 cells and a reduced suppressive capacity. Besides the suppressive function of T_reg cells, their effectiveness is determined by their ability to migrate into inflamed tissues. In the past years, new mechanisms involved in T_reg cell migration have been identified. One example of such a mechanism is the phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Efficient migration of T_reg cells requires the presence of VASP. IL-6, a cytokine which is abundantly present in the peripheral blood and in the synovial tissue of RA patients, induces posttranslational modifications of VASP. Recently, it has been shown in mice with collagen-induced arthritis (CIA) that this IL-6 mediated posttranslational modification leads to reduced T_reg cell trafficking. Another protein which facilitates T_reg cell migration is G-protein-signaling modulator 2 (GPSM2). It modulates G-protein coupled receptor functioning, thereby altering the cellular activity initiated by cell surface receptors in response to extracellular signals. The almost complete lack of GPSM2 in T_reg cells from RA patients contributes to their reduced ability to migrate towards inflammatory sites. In this review article, we highlight the newly identified mechanisms of T_reg cell migration and review the current knowledge about impaired T_reg cell homeostasis in RA.

Secretion of immunoregulatory cytokines by mesenchymal stem cells

According to the minimal criteria of the International Society of Cellular Therapy, mesenchymal stem cells (MSCs) are a population of undifferentiated cells defined by their ability to adhere to plastic surfaces when cultured under standard conditions, express a certain panel of phenotypic markers and can differentiate into osteogenic, chondrogenic and adipogenic lineages when cultured in specific inducing media. In parallel with their major role as undifferentiated cell reserves, MSCs have immunomodulatory functions which are exerted by direct cell-to-cell contacts, secretion of cytokines and/or by a combination of both mechanisms. There are no convincing data about a principal difference in the profile of cytokines secreted by MSCs isolated from different tissue sources, although some papers report some quantitative but not qualitative differences in cytokine secretion. The present review focuses on the basic cytokines secreted by MSCs as described in the literature by which the MSCs exert immunodulatory effects. It should be pointed out that MSCs themselves are objects of cytokine regulation. Hypothetical mechanisms by which the MSCs exert their immunoregulatory effects are also discussed in this review. These mechanisms may either influence the target immune cells directly or indirectly by affecting the activities of predominantly dendritic cells. Chemokines are also discussed as participants in this process by recruiting cells of the immune systems and thus making them targets of immunosuppression. This review aims to present and discuss the published data and the personal experience of the authors regarding cytokines secreted by MSCs and their effects on the cells of the immune system.

Lower TGFß serum levels and higher frequency of IFNγ-producing T cells during early immune reconstitution in surviving children after allogeneic stem cell transplantation

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (SCT) is increasingly used as a salvage therapy for patients with high-risk malignancies as well as life-threatening non-malignant diseases. However, only limited data about the association between outcome and functional parameters of recovering lymphocytes are available so far.

PROCEDURES

In this prospective study of 19 pediatric SCT recipients, we serially evaluated immune parameters quantitatively and qualitatively before and throughout allogeneic SCT. These data were analyzed with respect to survival.

RESULTS

Age, gender, GvHD, and type of graft were not different between surviving and non-surviving patients. Notably, in our cohort there was no case of transplant-related or infectious mortality. However, with the exception of two patients with advanced MDS, all patients not in complete remission (CR) relapsed in addition to three patients in higher CR (n = 7). All seven patients relapsing after allogeneic SCT later succumbed to their disease recurrence. Uni- and multivariate analysis showed that relapsing patients had higher TGFß serum levels as well as lower percentages of IFNγ-producing T cells before and early after transplantation. Furthermore, relapsing patients had a further decline in their thymic function between day 60 and 120 whereas non-relapsing patients already showed increasing TREC values during this time interval.

CONCLUSIONS

Collectively, patients who later relapse show a different pattern of immune reconstitution before and at early time points post-transplantation.

Extracts from Citrus unshiu promote immune-mediated inhibition of tumor growth in a murine renal cell carcinoma model

AIM OF THIS STUDY

Citrus unshiu (Satsuma mandarin, SM) is a citrus fruit the peel of which has been used as a traditional Chinese medicine to treat common cold, relieve exhaustion, and cancer. In this study, we examined how effectively the content and peel extracts of SM can suppress cancer growth. The mechanism underlying cancer-suppressing properties of SM was investigated in tumor-bearing mice with renal carcinoma cell, Renca.

MATERIALS AND METHODS

Effectiveness of SM in tumor suppression was evaluated by measuring size of tumor mass in tumor-bearing mice treated with various doses of SM content and peel extracts. Proliferation of tumor cells and splenocytes was determined by MTT assay and [³H]TdR uptake, respectively. Relevant immunological mechanisms were chased by assaying cytokines including TGF-β, IL-6, IFN-γ, and TNF-α by ELISA.

RESULTS

The content and peel extracts of SM inhibited the growth of tumor cells in tumor-bearing mice. Especially, average tumor volume of two groups treated with 3 and 30 mg peel extracts per mouse weight (kg) were significantly decreased to 52.32% (p<0.05) and 68.72% (p<0.01), respectively. To identify tumor regression mechanism, anti-tumor cytokines measured in Con A-activated splenocytes from tumor-bearing mice. IFN-γ was increased in both of the peel extract-treated groups, while TNF-α, which had been decreased by tumor growth, was rescued to the normal level in SM content and peel extracts-treated groups. However, SM content and peel extracts did not inhibit proliferation and tumor-proliferative cytokines including TGF-β and IL-6 production of tumor cells.

CONCLUSION

These results indicate that SM content and peel extracts have anti-tumor properties in the tumor-bearing murine model. The mechanism underlying the anti-tumor effects of SM extracts is strongly suggested to be via boosting cytokines such as IFN-γ and TNF-α, enhancing immune-mediated anti-tumor properties.

Role of TGF-β and the tumor microenvironment during mammary tumorigenesis

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that functions to inhibit mammary tumorigenesis by directly inducing mammary epithelial cells (MECs) to undergo cell cycle arrest or apoptosis, and to secrete a variety of cytokines, growth factors, and extracellular matrix proteins that maintain cell and tissue homeostasis. Genetic and epigenetic events that transpire during mammary tumorigenesis typically inactivate the tumor suppressing activities of TGF-beta and ultimately confer this cytokine with tumor promoting activities, including the ability to stimulate breast cancer invasion, metastasis, angiogenesis, and evasion from the immune system. This dramatic conversion in TGF-beta function is known as the "TGF-beta paradox" and reflects a variety of dynamic alterations that occur not only within the developing mammary carcinoma, but also within the cellular and structural composition of its accompanying tumor microenvironment. Recent studies have begun to elucidate the critical importance of mammary tumor microenvironments in manifesting the TGF-beta paradox and influencing the response of developing mammary carcinomas to TGF-beta. Here we highlight recent findings demonstrating the essential function of tumor microenvironments in regulating the oncogenic activities of TGF-beta and its stimulation of metastatic progression during mammary tumorigenesis.

Transforming growth factor beta (TGF-beta) and inflammation in cancer

The transforming growth factor beta (TGF-beta) has been studied with regard to the regulation of cell behavior for over three decades. A large body of research has been devoted to the regulation of epithelial cell and derivative carcinoma cell populations in vitro and in vivo. TGF-beta has been shown to inhibit epithelial cell cycle progression and promote apoptosis that together significantly contribute to the tumor suppressive role for TGF-beta during carcinoma initiation and progression. TGF-beta is also able to promote an epithelial to mesenchymal transition that has been associated with increased tumor cell motility, invasion and metastasis. However, it has now been shown that loss of carcinoma cell responsiveness to TGF-beta stimulation can also promote metastasis. Interestingly, enhanced metastasis in the absence of a carcinoma cell response to TGF-beta stimulation has been shown to involve increased chemokine production resulting in recruitment of pro-metastatic myeloid derived suppressor cell (MDSC) populations to the tumor microenvironment at the leading invasive edge. When present, MDSCs enhance angiogenesis, promote immune tolerance and provide matrix degrading enzymes that promote tumor progression and metastasis. Further, the recruitment of MDSC populations in this context likely enhances the classic role for TGF-beta in immune suppression since the MDSCs are an abundant source of TGF-beta production. Importantly, it is now clear that carcinoma-immune cell cross-talk initiated by TGF-beta signaling within the carcinoma cell is a significant determinant worth consideration when designing therapeutic strategies to manage tumor progression and metastasis.

TGF-beta and regulatory T cell in immunity and autoimmunity

INTRODUCTION

The immune response is controlled by several inhibitory mechanisms. These mechanisms include regulatory T cells, which exist in multiple classes. Notable among these are Foxp3-expressing regulatory T cells (Treg), NKT cells, and Tr1 cells. Common to these mechanisms are inhibitory cytokines such as interleukin-10 and transforming growth factor-beta (TGF-beta). TGF-beta and Foxp3-expressing Treg cells are critical in maintaining self-tolerance and immune homeostasis.

DISCUSSIONS

The immune suppressive functions of TGF-beta and Treg cells are widely acknowledged and extensively studied. Nonetheless, recent studies revealed the positive roles for TGF-beta and Treg cells in shaping the immune system and the inflammatory responses. In this paper, we will discuss the role of these mechanisms in the control of immunity and autoimmunity and the mechanisms that underlie how these molecules control these responses.

Combined immunogene therapy of IL-6 and IL-15 enhances anti-tumor activity through augmented NK cytotoxicity

Many tumors evade host immunity by lowering expression of major histocompatibility complex (MHC) molecules. Theoretically, low MHC expression should activate natural killer (NK) cells and in some cases suppress tumor growth; nevertheless, some tumors also produce high concentrations of immunosuppressive cytokines, such as transforming growth factor (TGF)-beta, to inhibit the activity of NK cells. Using a canine transmissible venereal tumor (CTVT) model, we have previously demonstrated that IL-6 is a strong antagonist for TGF-beta. Herein, we found that IL-6 alone was unable to significantly promote TGF-beta-inhibited NK activities. Conversely, IL-15 alone strongly promoted NK activities; however, NK activities were inhibited to baseline levels following the addition of TGF-beta. Therefore, a new strategy using combined immunogene therapy of both IL-6 and IL-15 mediated by electroporation was used in this study. This combined IL-6 and IL-15 treatment effectively relieved the inhibitory effect of TGF-beta and activated NK cell cytotoxicity of lymphokine-activated killer (LAK) cells. Similarly, in isolated DX5+ NK cells, only IL-6 and IL-15 in combination significantly overcame the inhibitory effect of TGF-beta and promoted NK cytotoxicity. The group of BALB/c mice injected with plasmids with IL-6 and IL-15 genes (pIL-6/pIL-15) had the highest percentages of DX5+ NK cells as compared with either the pIL-6 or pIL-15 groups. Further, in SCID mice inoculated with CTVT, electroporation-mediated delivery of pIL-6/pIL-15 was significantly more efficient in suppressing both tumor establishment and tumor growth as compared with pIL-6 or pIL-15 inoculation alone. In addition, the anti-asialo GM-1 antibody abolished NK activities in SCID mice and resulted in outgrowth of the tumors. Together, these results suggest that the TGF-beta-associated inhibition of NK cytotoxicity cannot be adequately restored by simply antagonizing TGF-beta with IL-6: the co-existence of NK activating factors such as IL-15 is also important in restoring TGF-beta-inhibited cytotoxicity. This study highlights the therapeutic potential of the pIL-6/pIL-15 combination by inhibiting TGF-beta activity and enhancing NK cytotoxicity.

Transforming growth factor-beta and the immune response: implications for anticancer therapy

Immune homeostasis is a delicate balance between the immune defense against foreign pathogens and suppression of the immune system to maintain self-tolerance and prevent autoimmune disease. Maintenance of this balance involves several crucial networks of cytokines and various cell types. Among these regulators, transforming growth factor-beta (TGF-beta) is a potent cytokine with diverse effects on hematopoietic cells. Its pivotal function within the immune system is to maintain tolerance via the regulation of lymphocyte proliferation, differentiation, and survival. In addition, TGF-beta controls the initiation and resolution of inflammatory responses through the regulation of chemotaxis and activation of leukocytes in the periphery, including lymphocytes, natural killer cells, dendritic cells, macrophages, mast cells, and granulocytes. Through its pleiotropic effects on these immune cells, TGF-beta prevents the development of autoimmune diseases without compromising immune responses to pathogens. However, overactivation of this pathway can lead to several immunopathologies under physiologic conditions including cancer progression, making it an attractive target for antitumor therapies. This review discusses the biological functions of TGF-beta and its effects on the immune system and addresses how immunosuppression by this cytokine can promote tumorigenesis, providing the rationale for evaluating the immune-enhancing and antitumor effects of inhibiting TGF-beta in cancer patients.

'Yin-Yang' functions of transforming growth factor-beta and T regulatory cells in immune regulation

Transforming growth factor-beta (TGF-beta) and forkhead box p3-expressing T-regulatory (Treg) cells are critical in maintaining self-tolerance and immune homeostasis. The immune suppressive functions of TGF-beta and Treg cells are widely acknowledged and extensively studied. Nonetheless, recent studies revealed the positive roles of TGF-beta and Treg cells in shaping the immune system and the inflammatory responses. This review discusses our and other's efforts in understanding the negative (Yin) as well as the positive (Yang) roles for TGF-beta and Treg cells in immune regulation.

Endogenous Transforming Growth Factor-? Inhibits Toll-Like Receptor Mediated Activation of Human Uterine Natural Killer Cells

PROBLEM

Toll-like receptors (TLRs) recognition is an important means for the innate immune system to rapidly respond to pathogen invasion. Our aim was to determine whether uterine natural killer (uNK) cell cytokine production induced by stimulation through TLRs could be regulated by endogenous transforming growth factor (TGF)-beta in human endometrium.

METHOD OF STUDY

Single cells were isolated from human endometrium, and interferon (IFN)-gamma production by endometrium cells and uNK cells was determined after stimulation by TLR agonists. The role of TGF-beta in regulating this response was tested by blocking TGF-beta function using antibodies or a specific inhibitor, SB431542.

RESULTS

TGF-beta blockade increased TLR agonist induced IFN-gamma by uNK cells. The regulation of uNK cell cytokine production was observed when uNK cells were incubated with agonists for TLR2 (PGN) or TLR3 (polyI:C). Blockade of TGF-beta or TGF-beta receptor signaling had no effect on constitutive cytokine production in the absence of TLR agonists.

CONCLUSION

The results indicate that endogenous TGF-beta alters cytokine responses of uNK cells in human endometrium in response to TLR agonists. These data suggest that uNK cell responses to microbial pathogens in the endometrium are regulated by the amount of biologically active TGF-beta present within the human endometrium.

Differential effects of Th1, monocyte/macrophage and Th2 cytokine mixtures on early gene expression for immune-related molecules by central nervous system mixed glial cell cultures

Cytokines secreted within the central nervous system (CNS) are important in the development of multiple sclerosis (MS) lesions. The balance between Th1, monocyte/macrophage (M/M) and Th2 cytokines in the CNS may be pivotal in determining the outcome of lesion development. We examined the effects of mixtures of cytokines on gene expression by CNS glial cells, as mixtures of cytokines are present in MS lesions, which in turn contain mixtures of glial cells. In this initial analysis by gene array, we examined changes at 6 hours to identify early changes in gene expression that represent primary responses to the cytokines. Rat glial cells were incubated with mixtures of Th1, M/M and Th2 cytokines for 6 hours and examined for changes in early gene expression employing microarray gene chip technology. A minimum of 814 genes were differentially regulated by one or more of the cytokine mixtures in comparison to controls, including changes in expression in a large number of genes for immune system-related proteins. Expression of the proteins for these genes likely influences development and inhibition of MS lesions as well as protective and regenerative processes. Analysing gene expression for the effects of various combinations of exogenous cytokines on glial cells in the absence of the confounding effects of inflammatory cells themselves should increase our understanding of cytokine-induced pathways in the CNS.

Assessing the safety of cytotoxic T lymphocytes transduced with a dominant negative transforming growth factor-beta receptor

Transforming growth factor (TGF)-beta, a pleiotropic cytokine that regulates cell growth, is secreted by many human tumors and markedly inhibits tumor-specific cellular immunity. It has previously been shown by our group that transduction of cytotoxic T lymphocytes (CTLs) with a retroviral vector expressing the dominant-negative TGFbeta type II receptor (DNR) overcomes this tumor evasion in a model of Epstein-Barr virus (EBV)-positive Hodgkin disease. TGFbeta is an important physiologic regulator of T-cell growth and survival, however, abrogation of this regulatory signal in genetically modified cells is potentially problematic. To ensure that unresponsiveness to TGFbeta did not lead to the unregulated growth of genetically modified CTLs, the characteristics of DNR-transduced CTLs in vivo were studied. Donor C57BL6 mice were vaccinated with human papillomavirus-E7 plasmid DNA to induce production of E7-specific CTLs. The E7-specific CTLs were genetically modified to express enhanced green fluorescent protein (GFP) or DNR and administered to syngeneic mice. All mice received monthly boosts with E7 DNA for 9 months, and during this time, transduced CTLs were detected in the peripheral blood of most of the mice using a quantitative real-time polymerase chain reaction. By 12 months, 3 months after cessation of vaccination, no DNR-transduced CTLs or GFP-transduced CTLs were detected in the peripheral blood. There were 4 cases of lymphoma (2 DNR-transduced mice and 2 control mice): all tumors were CD3-/CD8- and were also negative for the DNR transgene. Hence, mature antigen-specific cytotoxic T cells can be genetically modified to resist the antiproliferative effects of TGFbeta without undergoing spontaneous lymphoproliferation in vivo. They may be of value for treating human cancers, which use TGFbeta as a powerful immune evasion mechanism.

Transforming growth factor-beta regulation of immune responses

Transforming growth factor-beta (TGF-beta) is a potent regulatory cytokine with diverse effects on hemopoietic cells. The pivotal function of TGF-beta in the immune system is to maintain tolerance via the regulation of lymphocyte proliferation, differentiation, and survival. In addition, TGF-beta controls the initiation and resolution of inflammatory responses through the regulation of chemotaxis, activation, and survival of lymphocytes, natural killer cells, dendritic cells, macrophages, mast cells, and granulocytes. The regulatory activity of TGF-beta is modulated by the cell differentiation state and by the presence of inflammatory cytokines and costimulatory molecules. Collectively, TGF-beta inhibits the development of immunopathology to self or nonharmful antigens without compromising immune responses to pathogens. This review highlights the findings that have advanced our understanding of TGF-beta in the immune system and in disease.

Profibrotic cytokines and lymphocyte proliferation in stable renal allograft recipients treated with or without cyclosporine A

Profibrotic cytokines such as transforming growth factor-beta 1 (TGF-beta1) and endothelin-1 (ET-1) are involved in the pathogenesis of chronic allograft nephropathy. We assessed the effect of maintenance immunosuppression with or without cyclosporine A on TGF-beta1 and ET-1 expression as well as lymphocyte proliferation in renal allograft recipients. Patients were divided into groups according to their maintenance immunosuppression: A, azathioprine + methylprednisolone; B, cyclosporine A + azathioprine + methylprednisolone. TGF-beta1 and ET-1 plasma concentrations were not different between both groups. TGF-beta1 concentrations in cell culture supernatants and lymphocyte proliferation were higher in group B as compared to group A. No correlation was found between TGF-beta1 plasma concentrations and lymphocyte proliferation. Multiple linear regression analysis revealed that patient characteristics influence TGF-beta1 and ET-1 expression. In conclusion, plasma levels of profibrotic cytokines do not reflect the existing profibrotic potential of immunosuppressive drugs. Demographic factors and the employed co-medication confound the results.

Human NK cell IFN-gamma production is regulated by endogenous TGF-beta

NK cells are an important component of innate immunity, and they can promote CTL and Th1 cell development and macrophage activation via cytokines. TGF-beta is believed to be an important immunoregulatory molecule, and for this reason several TGF-beta inhibitors are currently in clinical development. However, the modulation of specific innate immune responses by endogenous human TGF-beta remains unclear. In this study, we demonstrate that blocking the action of endogenous TGF-beta resulted in an increase in both the percentage of responding NK cells and the amount of IFN-gamma produced by human NK cells when stimulated by monokines and TLR agonists. Blocking endogenous TGF-beta resulted in significant NK cell IFN-gamma production under suboptimal stimulation conditions. Our findings also suggest that TGF-beta associated with other blood cells may be involved in limiting NK cell activation. Thus, inhibiting endogenous TGF-beta provides a means to shift NK cell activation and promote cellular immunity.

TGF-beta directly targets cytotoxic T cell functions during tumor evasion of immune surveillance

Tumors escape from immune surveillance by producing the immunosuppressive cytokine TGF-beta. However, the mechanism by which TGF-beta inhibits T cell-mediated tumor clearance in vivo is unknown. We demonstrate that TGF-beta acts on cytotoxic T lymphocytes (CTLs) to specifically inhibit the expression of five cytolytic gene products-namely, perforin, granzyme A, granzyme B, Fas ligand, and interferon gamma-which are collectively responsible for CTL-mediated tumor cytotoxicity. Repression of granzyme B and interferon-gamma involves binding of TGF-beta-activated Smad and ATF1 transcription factors to their promoter regions, indicating direct and selective regulation by the TGF-beta/Smad pathway. Neutralization of systemic TGF-beta in mice enables tumor clearance with restoration of cytotoxic gene expression in antigen-specific CTLs in vivo. We suggest that TGF-beta suppresses CTL function in vivo through an anticytotoxic program of transcriptional repression.

Regulation of interleukin-2 induced soluble Fas ligand release from human peripheral blood mononuclear cells

Adjuvant interleukin (IL)-2 immunotherapy has been used in the treatment of different malignant dieseases. However, clinical results have been rather disappointing. Therefore, further investigations on IL-2-induced mediators of cytotoxicity seem to be necessary in order to possibly create cytokine cocktails which could enhance the IL-2-induced cytotoxicity. We therefore investigated the regulation of IL-2-induced release of soluble Fas Ligand (sFasL), since this factor is known to possess anti-tumor activities. In CD3-stimulated peripheral blood mononuclear cells IL-2 induced sFasL in a dose-dependent fashion. Maximum sFasL concentrations were obtained after stimulation of MNC for 120 hrs. Inhibition of endogenous IL-12 production significantly reduced IL-2-mediated sFasL release by about 25%. In contrast, addition of IL-12 enhanced the IL-2-induced sFasL about 1,5-fold. IL-10 and IL-4 reduced the IL-2-stimulated sFasL by about 30%. Interestingly, these suppressive effects could be antagonized by the addition of IL-12. Not only exogenous IL-10 but also endogenously produced IL-10 decreased the sFasL release to that extent which had been stimulated by IL-12. Since IL-12 and IL-10 only marginally influenced the IL-2-mediated cell proliferation as well as the IL-2-induced cell death, the IL-12- and IL-10-controlled sFasL release seems to be based on an enhanced production per cell. However, the increase in cell numbers as well as the decrease of viability during cell culture might additionally contribute to the IL-2-induced increase of sFasL release. This secondary effect might explain why IL-2-mediated sFasL production is only partially controlled by regulatory cytokines such as IL-4, IL-10 or IL-12. In conclusion, addition of IL-12 might increase the efficacy of IL-2 immunotherapy by inhibition of the IL-10-mediated negative feed-back loop on IL-2-mediated sFasL release.

Human myeloma cells stimulate the receptor activator of nuclear factor-kappa B ligand (RANKL) in T lymphocytes: a potential role in multiple myeloma bone disease

The biologic mechanisms involved in the pathogenesis of multiple myeloma (MM) bone disease are not completely understood. Recent evidence suggests that T cells may regulate bone resorption through the cross-talk between the critical osteoclastogenetic factor, receptor activator of nuclear factor-kappaB ligand (RANKL), and interferon gamma (IFN-gamma) that strongly suppresses osteoclastogenesis. Using a coculture transwell system we found that human myeloma cell lines (HMCLs) increased the expression and secretion of RANKL in activated T lymphocytes and similarly purified MM cells stimulated RANKL production in autologous T lymphocytes. In addition, either anti-interleukin 6 (anti-IL-6) or anti-IL-7 antibody inhibited HMCL-induced RANKL overexpression. Consistently, we demonstrated that HMCLs and fresh MM cells express IL-7 mRNA and secrete IL-7 in the presence of IL-6 and that bone marrow (BM) IL-7 levels were significantly higher in patients with MM. Moreover, we found that the release of IFN-gamma by T lymphocytes was reduced in presence of both HMCLs and purified MM cells. Furthermore, in a stromal cell-free system, osteoclastogenesis was stimulated by conditioned medium of T cells cocultured with HMCLs and inhibited by recombinant human osteoprotegerin (OPG; 100 ng/mL to 1 microg/mL). Finally, RANKL mRNA was up-regulated in BM T lymphocytes of MM patients with severe osteolytic lesions, suggesting that T cells could be involved at least in part in MM-induced osteolysis through the RANKL overexpression.

Adapting a transforming growth factor beta-related tumor protection strategy to enhance antitumor immunity

Transforming growth factor beta (TGF-beta), a pleiotropic cytokine that regulates cell growth and differentiation, is secreted by many human tumors and markedly inhibits tumor-specific cellular immunity. Tumors can avoid the differentiating and apoptotic effects of TGF-beta by expressing a nonfunctional TGF-beta receptor. We have determined whether this immune evasion strategy can be manipulated to shield tumor-specific cytotoxic T lymphocytes (CTLs) from the inhibitory effects of tumor-derived TGF-beta. As our model we used Epstein-Barr virus (EBV)-specific CTLs that are infused as treatment for EBV-positive Hodgkin disease but that are vulnerable to the TGF-beta produced by this tumor. CTLs were transduced with a retrovirus vector expressing the dominant-negative TGF-beta type II receptor HATGF-betaRII-Deltacyt. HATGF-betaRII-Deltacyt- but not green fluorescence protein (eGFP)-transduced CTLs was resistant to the antiproliferative and anticytotoxic effects of exogenous TGF-beta. Additionally, receptor-transduced cells continued to secrete cytokines in response to antigenic stimulation. TGF-beta receptor ligation results in phosphorylation of Smad2, and this pathway was disrupted in HATGF-betaRII-Deltacyt-transduced CTLs, confirming blockade of the signal transduction pathway. Long-term expression of TGF-betaRII-Deltacyt did not affect CTL function, phenotype, or growth characteristics. Tumor-specific CTLs expressing HATGF-betaRII-Deltacyt should have a selective functional and survival advantage over unmodified CTLs in the presence of TGF-beta-secreting tumors and may be of value in treatment of these diseases.

Co-operation of IL-1 and IL-2 on T-cell activation in mononuclear cell cultures

In search of an optimized anti-cancer immunotherapy, the combination of IL-2 and IL-1 has been tried. In an in-vitro LAK model, this cytokine cocktail seemed to be quite promising. In our in-vitro model of IL-2 induced T-cell activation we have therefore investigated the co-operation of these two potent immunostimulators. Mononuclear cells were stimulated with CD3 activating antibody in the presence of different cytokines and blocking or neutralizing antibodies. Cytokine concentrations were detected in the supernatants with ELISA. Intracellular IFN-gamma and IL-4 in the different T-cell subsets was measured by flow cytometry. IL-1 and IL-1 receptor antagonist (IL-1Ra) were up-regulated by IL-2, this was achieved independently of IL-12 or CD40/CD40L interaction. As a negative feedback mechanism, IL-1beta induced its natural antagonist, IL-1Ra. Both endogenous and exogenous IL-10 suppressed IL-1beta and induced IL-1Ra, thus markedly decreased the amount of functional IL-1. The combination of IL-2 and IL-1beta lead to a mildly increased Interferon-gamma (IFN-gamma) secretion (+20%, p < 0.05), however, this appeared to be the result of an increased IFN-gamma production per secreting cell, rather than of an increased recruitment of non-secreting cells. Similarly, IL-6 was also induced in an additive fashion (+30%, p < 0.05). For both cytokines, this effect could be significantly augmented by neutralizing IL-1Ra. Concentrations of IL-2 induced IL-10 and soluble Fas ligand (sFasL) were not affected by IL-1beta. We were thus able to demonstrate that IL-1 relays its activity through different pathways than IL-2. Furthermore, we could show that the potentially synergistic action of IL-2 and IL-1 was hindered by the simultaneous induction of signficant amounts of IL-1Ra. From the latter findings we conclude that the combination of IL-2 and IL-1 for cytokine-induced anti-tumor activity may not, but a combination of IL-2 and anti-IL-1Ra might prove beneficial.

Suppression of IL-2-induced T cell proliferation and phosphorylation of STAT3 and STAT5 by tumor-derived TGF beta is reversed by IL-15

IL-2 responses are susceptible to suppression by TGFbeta, a cytokine widely implicated in suppression of inflammatory responses and secreted by many different tumor cell types. There have been conflicting reports regarding inhibition of IL-2-induced STAT3 and STAT5 phosphorylation by TGFbeta and subsequent suppression of immune responses. Using TGFbeta-producing multiple myeloma tumor cells we demonstrate that tumor-derived TGFbeta can block IL-2-induced proliferation and STAT3 and STAT5 phosphorylation in T cells. High affinity IL-2R expression was required for the suppression of IL-2 responses as a novel CD25(-) T cell line proliferated and phosphorylated STAT3 when cultured with tumor cells or rTGFbeta1. Activating T cells with IL-15, which does not use the high affinity IL-2R, completely restored the ability of T cells to phosphorylate STAT3 and STAT5 when cultured with tumor cells. IL-15-treated T cells proliferated normally when cocultured with tumor cells or rTGFbeta1, whereas IL-2 responses were consistently inhibited. Preincubation with IL-15 also restored the ability of T cells to respond to IL-2 by phosphorylating STAT3 and STAT5, and proliferating normally in the presence of tumor cells. IL-2 pretreatment did not restore T cell function. IL-15 also restored T cell responses by T cells from multiple myeloma patients, and against freshly isolated bone marrow tumor samples. Thus, activation of T cells by IL-15 renders T cells resistant to suppression by TGFbeta1-producing tumor cells and rTGFbeta1. This finding may be exploited in the design of new immunotherapy approaches that will rely on T cells avoiding tumor-induced suppression.