Human ex vivo carcinoma cells produce transforming growth factor beta and thereby can inhibit lymphocyte functions in vitro

TGF-β1 and TGF-β2 abundance in liver diseases of mice and men

TGF-β1 is a major player in chronic liver diseases promoting fibrogenesis and tumorigenesis through various mechanisms. The expression and function of TGF-β2 have not been investigated thoroughly in liver disease to date. In this paper, we provide evidence that TGF-β2 expression correlates with fibrogenesis and liver cancer development.

Using quantitative realtime PCR and ELISA, we show that TGF-β2 mRNA expression and secretion increased in murine HSCs and hepatocytes over time in culture and were found in the human-derived HSC cell line LX-2. TGF-β2 stimulation of the LX-2 cells led to upregulation of the TGF-β receptors 1, 2, and 3, whereas TGF-β1 treatment did not alter or decrease their expression. In liver regeneration and fibrosis upon CCl₄ challenge, the transient increase of TGF-β2 expression was accompanied by TGF-β1 and collagen expression. In bile duct ligation-induced fibrosis, TGF-β2 upregulation correlated with fibrotic markers and was more prominent than TGF-β1 expression. Accordingly, MDR2-KO mice showed significant TGF-β2 upregulation within 3 to 15 months but minor TGF-β1 expression changes. In 5 of 8 hepatocellular carcinoma (HCC)/hepatoblastoma cell lines, relatively high TGF-β2 expression and secretion were observed, with some cell lines even secreting more TGF-β2 than TGF-β1. TGF-β2 was also upregulated in tumors of TGFα/cMyc and DEN-treated mice. The analysis of publically available microarray data of 13 human HCC collectives revealed considerable upregulation of TGF-β2 as compared to normal liver.

Our study demonstrates upregulation of TGF-β2 in liver disease and suggests TGF-β2 as a promising therapeutic target for tackling fibrosis and HCC.

Targeting immune checkpoints: New opportunity for mesothelioma treatment?

Malignant pleural mesothelioma is an aggressive cancer linked to asbestos exposure in most patients. Due to the long latency between exposure and presentation, incidence is expected to further increase in the next decade, despite the ban on asbestos import which occurred at the end of last century in industrialized countries. Platinum-based palliative chemotherapy is the only treatment with proven benefit on outcome, resulting in selected patients in a median overall survival of about 1 year. Therefore, there is room for therapeutic improvement using a new strategy to prolong survival. Dealing with cancer cell induced immunosuppression is a promising approach. Reactivating immune responses that are silenced by immune checkpoints recently gained a lot of interest. Checkpoint blockade has already shown promising preclinical and clinical results in several cancer types and is currently also being investigated in mesothelioma. Here, we discuss the expression patterns and mechanisms of action of CTLA-4 and PD-1 as the two most studied and of TIM-3 and LAG-3 as two interesting upcoming immune checkpoints. Furthermore, we review the clinical results of molecules blocking these immune checkpoints and point out their future opportunities with a special focus on mesothelioma.

Increase of regulatory T cells in metastatic stage and CTLA-4 over expression in lymphocytes of patients with non-small cell lung cancer (NSCLC)

We hypothesized that the increased percentages of Regulatory T (Treg) cells, as well as over expression of Cytotoxic T Lymphocyte Antigen-4 (CTLA-4) by lymphocyte subsets might be associated with lung cancer. Accordingly, peripheral blood of 23 new cases with non-small cell lung cancer (NSCLC) and 16 healthy volunteers were investigated, by follow cytometry, for the prevalence of CD4+CD25+FoxP3+ Treg cells as well as surface (sur-) and intracellular (In-) expression of CTLA-4 by the main lymphocyte subsets (CD4+, CD8+ and CD19+). Results indicated that NSCLC patients had an increased percentage of Treg cells than controls (7.9±4.1 versus 3.8±1.8, P=0.001). The proportion of Treg cells was observed to be increased by stage increase in patients (stage II=5.2±2.4, stage III=7.9±4.4, stage IV=12.0±2.2), and also significantly higher in metastatic than non-metastatic stages (12.0±2.2 versus 6.8±3.9, P=0.023). Increase of SurCTLA-4- as well as InCTLA-4-expressing lymphocytes in patients were observed in nearly all investigated subsets, but significant differences between patients and controls were observed about InCTLA-4+CD4+ lymphocytes (8.6±7.1 and 3.8±5.3 respectively, P=0.006) as well as SurCTLA-4+CD8+ lymphocytes (0.3±0.2 and 0.2±0.1 respectively, P=0.047). In conclusion, the results suggest that immunotherapy regimen targeting CTLA-4 and Treg cells might be beneficial in lung cancer patients.

Suppression of lymphocyte proliferation and regulation of dendritic cell phenotype by soluble mediators from rat lacrimal epithelial cells

Lacrimal epithelial cells appear to constitutively secrete autoantigens to their underling stroma. The present experiments address the hypothesis that they also secrete soluble factors that regulate immune responses. Epithelial cells, spleen cells and lymphocytes were obtained from rabbits or rats and cultured in various configurations. Monocytes from rat bone marrow were matured to dendritic cells (DC) ex vivo. Proliferation was measured by [3H]-thymidine incorporation; surface MHC Class II and CD86 using flow cytometry; and mRNA relative abundances using real time RT-PCR. Microporous culture inserts containing rat lacrimal cells inhibited proliferation of rabbit lymphocytes co-cultured with autologous lacrimal cells and of rat lymphocytes co-cultured with TNF-alpha-stimulated DC. They inhibited CD86 and MHC Class II surface expression by maturating DC and reversed surface expression of CD86 but not MHC Class II by partially matured DC. Subsequent exposure of partially matured DC to mediators from rat lacrimal cells reversed the ability to stimulate lymphocyte proliferation. TGF-beta(1) and IL-10 mRNAs increased somewhat when rat lacrimal cells were isolated but decreased markedly in rabbit lacrimal cells. Antibodies to TGF-beta prevented soluble factors from rat lacrimal cells from inhibiting proliferation of rabbit lymphocytes co-cultured with rabbit lacrimal cells, but recombinant TGF-beta alone did not mimic the soluble factors. IL-10 immunopositivity was detected in epithelial cells of interlobular ducts and occasional interstitial cells in rabbit lacrimal gland. Rat lacrimal epithelial cells secrete TGF-beta and other factors that synergize to suppress lymphocyte proliferation and regulate DC maturation. Interlobular duct epithelial cells in rabbit lacrimal glands may express similar functions.

Role of endocrine and growth factors on the ovarian surface epithelium

Epithelial ovarian cancer is a highly fatal disease for which prevention strategies have been limited; in part because of our poor understanding of the underlying biology of its precursor, the ovarian surface epithelium (OSE). The OSE is a single layer of flat-to-cuboidal mesothelial cells that covers the surface of the ovary. Despite its inconspicuous appearance in vivo, it is believed that OSE cells actively participate in the cyclical ovulatory rupture and repair process. The continuous rupture of the OSE at ovulation and the subsequent proliferation to repair the wound renders the cells susceptible to genetic damage and malignant transformation. As the ovary is a rich source of multiple hormones, and normal OSE and ovarian carcinomas secrete and have receptors for hormones, growth factors and cytokines, these factors are strong candidates to regulate normal OSE physiology and the transformation and progression of ovarian cancers. In particular, alterations of hormone/growth factor production and receptor expression are common in ovarian tumors. This review summarizes the current knowledge in the field of endocrinology and its relationship to the biology and pathology of the OSE.

Role of tumor-derived transforming growth factor-beta1 (TGF-beta1) in site-dependent tumorigenicity of murine ascitic lymphosarcoma

An ascitic lymphosarcoma (LS-A) of Swiss mice that regressed spontaneously on subcutaneous (s.c.) transplantation was investigated for the mechanism of its progressive growth and host mortality on intraperitoneal (i.p.) transplantation. In vitro studies indicated significant inhibition of LS-A proliferation seeded at higher cell density (>10(4)/ml). Culture supernatants of LS-A caused bi-modal growth effects, the early supernatants (24 h) caused stimulation and the late (72 h) supernatants inhibited LS-A proliferation. The 72-h supernatants also suppressed T and B cell response to mitogens in a dose-dependent manner. Pan anti-transforming growth factor-beta antibody abrogated the inhibitory effects of supernatants. The supernatants contained both latent as well as bio-active form of transforming growth factor-beta1 (TGF-beta1) as determined by ELISA. Mice bearing i.p. ascites tumor had elevated serum TGF-beta1, hemoglobulinemia, splenic lymphopenia, impaired response of the T cells to mitogen and reduced expression of transferrin receptor (CD71) on the bone marrow cells. However, mice which rejected s.c. transplants, did not show significant changes in these parameters. Our studies indicated profound influence of site of tumor growth on tumor progression and host immune system mediated by tumor-derived TGF-beta1. It is possible that human tumors which secrete TGF-beta1 may exhibit similar patho-physiological effects in the host depending on the anatomical site of the tumor.

Adenosine inhibits activation-induced T cell expression of CD2 and CD28 co-stimulatory molecules: role of interleukin-2 and cyclic AMP signaling pathways

Adenosine is an immunosuppressive molecule that is associated with the microenvironment of solid tumors. Mouse T cells activated with anti-CD3 antibody in the presence of adenosine with or without coformycin (to prevent adenosine breakdown by adenosine deaminase) exhibited decreased tyrosine phosphorylation of some intracellular proteins and were inhibited in their ability to proliferate and synthesize interleukin (IL)-2. In addition, adenosine interfered with activation-induced expression of the co-stimulatory molecules CD2 and CD28. Activation-induced CD2 and CD28 expression was also diminished when T cells were activated in the presence of anti-IL-2 and anti-CD25 antibodies to neutralize IL-2 bioactivity. Collectively, these data suggest that CD2 and CD28 up-regulation following T cell activation is IL-2-dependent; and that adenosine inhibits activation-induced T cell expression of CD2 and CD28 by interfering with IL-2-dependent signaling. The inhibitory effect of adenosine on activation-induced CD2 and CD28 expression could not be attributed to cyclic AMP (cAMP) accumulation resulting from the stimulation of adenylyl cyclase-coupled adenosine receptors, even though cAMP at concentrations much higher than those generated following adenosine stimulation was inhibitory for both CD2 and CD28 expression. We conclude that adenosine interferes with IL-2-dependent T cell expression of co-stimulatory molecules via a mechanism that does not involve the accumulation of intracellular cAMP.

Role of transforming growth factor beta in ovarian surface epithelium biology and ovarian cancer

Ovarian cancers arise out of the ovarian surface epithelium (OSE), which is the single layer of epithelial cells covering the ovary. These cells go through repeated cycles of proliferation with the growth and rupture of ovarian follicles. One growth factor involved in the regulation of OSE is transforming growth factor beta (TGFbeta). The different isoforms of TGFbeta (TGFbeta1, TGFbeta2 and TGFbeta3) and its receptor are all present in both OSE and the underlying ovarian surface stroma. The levels of the TGFbeta isoforms and receptors are regulated independently of each other in these different ovarian tissues. Observations suggest the existence of multiple autocrine/paracrine TGFbeta signalling loops. TGFbeta acts to inhibit proliferation of normal OSE and early stage ovarian carcinomas. Conversely, in later stage ovarian cancer the inhibitory actions of TGFbeta on epithelial proliferation have been overcome, while TGFbeta is able to promote malignant neoplastic behaviours. The regulation of TGFbeta signalling by ovarian steroid hormones may be one mechanism by which the OSE responds to cyclic changes in the underlying follicles.

Efficacious immunomodulatory activity of the chemokine stromal cell–derived factor 1 (SDF-1): local secretion of SDF-1 at the tumor site serves as T-cell chemoattractant and mediates T-cell–dependent antitumor responses

The chemokine stromal cell–derived factor 1 (SDF-1) is essential for perinatal viability, B lymphopoiesis, and bone marrow myelopoiesis, and is a potent monocyte and T-lymphocyte chemoattractant. Interactions of SDF-1 with its receptor CXCR4 have been implicated in CD34+ cell migration and homing. Here it is shown that human SDF-1β (hSDF-1β) alone secreted by hSDF-1β–transduced tumor cells promotes efficacious antitumor responses. The murine C1498 leukemia and B16F1 melanoma models have been studied. For expression of hSDF-1β by tumor cells (SDF-tumor cells), packaging cell lines secreting retroviruses encoding hSDF-1β have been used. The results demonstrate that 50% (B16F1) and 90% (C1498) of naive mice injected with SDF-tumor cells reject their tumors. Prophylactic vaccination of naive mice with irradiated SDF-tumor cells leads to systemic immunity, and therapeutic vaccination leads to cure of established tumors. Mice that previously rejected live SDF-tumor cells are immune to the rejected tumor but susceptible to another tumor and have in vitro tumor-specific cytotoxic T lymphocyte (CTL) activity. SDF-tumor cells are not rejected by immunodeficientscid mice. Immunohistochemistry shows significant infiltration of SDF-1 tumors by T cells, and in vivo T-cell depletion studies indicate that CD4+ T cells are required for SDF-mediated tumor rejection. In conclusion, the present data suggest that SDF-1/CXCR4 interactions have the potential to regulate efficacious antitumor immune responses; exploitation of these interactions may lead to novel therapeutic interventions.

Peripheral blood mononuclear cell proliferation to heat shock protein-70 derived from autologous lung carcinoma

In animals, tumor-derived heat shock proteins (HSP) induce immune-mediated protection against autologous cancer. We investigated whether HSP-70 derived from human lung carcinoma are also complexed to tumor-specific antigens. Peripheral blood mononuclear cells collected 10 days after surgery from patients with lung cancer were stimulated with HSP-70 purified from autologous and heterologous tumors. The stimulation index (SI) obtained when stimulating cells with autologous tumor-derived HSP-70 averaged 3.07 +/- 0.75 in patients with lung cancer and 1.57 +/- 0.33 in control subjects (p < 0.001 by analysis of variance). No significant stimulation was observed with HSP-70 derived either from the majority of heterologous tumors or from autologous tumor-free lung tissue. SI decreased from 3.59 +/- 0.65 to 1.65 +/- 0.38 in six patients tested again 3 months after surgery (p = 0.02 by Wilcoxon test for paired data). HSP-70 derived from lung carcinoma are shown to be associated with T cell antigens. The T cell reactivity appears transient and restricted to antigens complexed to HSP-70 derived from autologous tumors only. This suggests that the antigenicity of human lung tumors is unique, which may be crucial for the design of new vaccines.

Adenosine acts through an A3 receptor to prevent the induction of murine anti-CD3-activated killer T cells

Adenosine, a purine nucleoside found at high levels in solid tumors, is able to suppress the recognition/adhesion and effector phases of killer lymphocyte-mediated tumor cell destruction. Here, we demonstrate that adenosine, at concentrations that are typically present in the extracellular fluid of solid tumors, exerts a profound inhibitory effect on the induction of mouse cytotoxic T cells, without substantially affecting T-cell viability. T-cell proliferation in response to mitogenic anti-CD3 antibody was impaired in the presence of 10 microM adenosine (plus coformycin to inhibit endogenous adenosine deaminase). Antigen-specific T-cell proliferation was similarly inhibited by adenosine. Anti-CD3-activated killer T (AK-T) cells induced in the presence of adenosine exhibited reduced major histocompatibility complex-unrestricted cytotoxicity against P815 mastocytoma cells in JAM and (51)Cr-release assays. Diminished tumoricidal activity correlated with reduced expression of mRNAs coding for granzyme B, perforin, Fas ligand and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), as well as with diminished Nalpha-CBZ-L-lysine thiobenzylester (BLT) esterase activity. Interleukin-2 and interferon-gamma synthesis by AK-T cells was also inhibited by adenosine. AK-T cells express mRNA coding for A(2A), A(2B) and A(3) receptors, but little or no mRNA coding for A(1) receptors. The inhibitory effect of adenosine on AK-T cell proliferation was blocked by an A(3) receptor antagonist (MRS1191) but not by an A(2) receptor antagonist (3,7-dimethyl-1-propargylxanthine [DMPX]). The A(3) receptor agonists (N(6)-2-(4-aminophenyl)ethyladenosine [APNEA] and N(6)-benzyl-5'-N-ethylcarboxamidoadenosine [N(6)-benzyl-NECA]) also inhibited AK-T cell proliferation. Adenosine, therefore, acts through an A(3) receptor to prevent AK-T cell induction. Tumor-associated adenosine may act through the same mechanism to impair the development of tumor-reactive T cells in cancer patients.

Glioma cell invasion: regulation of metalloproteinase activity by TGF-beta

Matrix metalloproteinases (MMPs) are a family of extracellular endopeptidases that selectively degrade components of the extracellular matrix. MMPs are implicated in tumor cell invasion because they mediate the breakdown of the basal membrane. In addition, they seem to be important for the creation and maintenance of a microenvironment that facilitates tumor cell survival. Among the essential characteristics of human malignant gliomas are infiltrative growth, angiogenesis and suppression of antitumor immune surveillance. Transforming growth factor-beta (TGF-beta) is intimately involved in the regulation of these processes. We have previously demonstrated that TGF-beta promotes the migration of LN- 18 and LN-229 glioma cells via a process that may involve the upregulation of alphaVbeta3 integrin expression. Furthermore, we have defined a novel pathway for hepatocyte growth factor (HGF)-induced glioma cell migration and invasion which requires the induction of TGF-beta2 expression. Here, we demonstrate that TGF-beta2 induces MMP-2 expression and suppresses tissue inhibitor of metalloproteinases (TIMP)-2 expression and that concentration-dependently promotes the invasion of U87MG and LN-229 glioma cells in a matrigel invasion assay. Similarly, ectopic expression of the anti-apoptotic BCL-x, protein leads to enhanced matrigel invasion by LN-18 and LN-229 glioma cells. We outline the possible interrelations of TGF-beta, proteins of the BCL-2 family, integrins and metalloprotease activity. By virtue of its promotion of glioma invasion and its growth regulatory and immunomodulatory properties. TGF-beta continues to be one of the most promising targets for the experimental therapy of human malignant glioma.

Glioma cell invasion: regulation of metalloproteinase activity by TGF-beta

Matrix metalloproteinases (MMPs) are a family of extracellular endopeptidases that selectively degrade components of the extracellular matrix. MMPs are implicated in tumor cell invasion because they mediate the breakdown of the basal membrane. In addition, they seem to be important for the creation and maintenance of a microenvironment that facilitates tumor cell survival. Among the essential characteristics of human malignant gliomas are infiltrative growth, angiogenesis and suppression of antitumor immune surveillance. Transforming growth factor-beta (TGF-beta) is intimately involved in the regulation of these processes. We have previously demonstrated that TGF-beta promotes the migration of LN- 18 and LN-229 glioma cells via a process that may involve the upregulation of alphaVbeta3 integrin expression. Furthermore, we have defined a novel pathway for hepatocyte growth factor (HGF)-induced glioma cell migration and invasion which requires the induction of TGF-beta2 expression. Here, we demonstrate that TGF-beta2 induces MMP-2 expression and suppresses tissue inhibitor of metalloproteinases (TIMP)-2 expression and that concentration-dependently promotes the invasion of U87MG and LN-229 glioma cells in a matrigel invasion assay. Similarly, ectopic expression of the anti-apoptotic BCL-x, protein leads to enhanced matrigel invasion by LN-18 and LN-229 glioma cells. We outline the possible interrelations of TGF-beta, proteins of the BCL-2 family, integrins and metalloprotease activity. By virtue of its promotion of glioma invasion and its growth regulatory and immunomodulatory properties. TGF-beta continues to be one of the most promising targets for the experimental therapy of human malignant glioma.

Abnormalities of the transforming growth factor-beta pathway in ocular melanoma

The majority of ocular melanomas occur in the uveal tract. Chemotherapy is generally ineffective and large tumours requiring enucleation have a greater than 50% mortality at 5 years. Monosomy for chromosome 3 is common in uveal melanoma and it is known that there is loss of responsiveness to transforming growth factor beta (TGFbeta) in melanoma cell lines. Since the gene for TGFbeta receptor II (TGFbetaR2) is located on chromosome 3p22, this study investigates the possibility that the TGFbeta pathway, and TGFbetaR2 in particular, might be involved in the pathogenesis of this rare eye tumour. To this end, the expression of molecules in the pathway has been examined by immunocytochemistry (TGFbeta, TGFbetaR2, SMAD2, SMAD3, SMAD4, and p27), backed up by a cell culture assay of TGFbeta-mediated growth suppression, RT-PCR for SMAD4, and loss of heterozygosity (LOH) on 3p22. There was LOH at 3p22 in 6/19 tumours and loss of TGFbetaR2 expression in 10/27 tumours. Immunohistochemistry for SMADs 2, 3, and 4 showed potential loss of signal transduction in 14/27 tumours. The results indicate abnormality of the TGFbeta pathway in 61% of tumours for which unequivocal results were obtained and suggest that abrogation of control of melanocyte growth by the TGFbeta pathway may be important in the formation of uveal melanoma.

Immune selection in neoplasia: towards a microevolutionary model of cancer development

The dual properties of genetic instability and clonal expansion allow the development of a tumour to occur in a microevolutionary fashion. A broad range of pressures are exerted upon a tumour during neoplastic development. Such pressures are responsible for the selection of adaptations which provide a growth or survival advantage to the tumour. The nature of such selective pressures is implied in the phenotype of tumours that have undergone selection. We have reviewed a range of immunologically relevant adaptations that are frequently exhibited by common tumours. Many of these have the potential to function as mechanisms of immune response evasion by the tumour. Thus, such adaptations provide evidence for both the existence of immune surveillance, and the concept of immune selection in neoplastic development. This line of reasoning is supported by experimental evidence from murine models of immune involvement in neoplastic development. The process of immune selection has serious implications for the development of clinical immunotherapeutic strategies and our understanding of current in vivo models of tumour immunotherapy.

Bladder cancer immunogenicity: expression of CD80 and CD86 is insufficient to allow primary CD4+ T cell activation in vitro

Transitional cell carcinomas (TCC) of the urinary bladder are known to express proteins which can yield potentially immunogenic peptide epitopes for expression in the context of cell surface class I or class II MHC antigens. However, additional costimulatory ligands must also be expressed before such a cell might directly induce full activation and proliferation of resting, antigen-specific T lymphocytes. Intravesical therapy might be used to manipulate T cell costimulation in order to promote specific rejection of TCC cells. This in vitro study examined the potential of such a strategy by transfection of the prototypical TCC line J82 with the important costimulatory molecules CD80 (B7-1) and CD86 (B7-2). Untransfected J82 cells expressed class I and II MHC antigens, a range of cell adhesion molecules, though did not induce T cell proliferation in a robust, allogeneic co-culture system. Transfected J82 cells expressed CD80 or CD86 at levels comparable to an antigen-presenting B cell line. Furthermore, functional surface expression of CD80 and CD86 was demonstrated in a mitogen-dependent assay of costimulation. However, neither CD80+ nor CD86+ transfectant J82 cells could induce significant proliferation of antigen-specific CD4+ T cells. Further analysis showed that bystander J82 cells could inhibit independent T cell activation in an effect dependent on direct cell contact. This inhibitory effect was associated with increased cell death in the responding lymphocyte population and is concordant with surface expression of CD95L by the J82 cell line.

CD3 hyporesponsiveness and in vitro apoptosis are features of T cells from both malignant and nonmalignant secondary lymphoid organs

There is a dogma in tumor immunology that tumor-infiltrating lymphocytes (TIL) are defective based on their lack of antitumoral efficacy in vivo and on impaired response to in vitro functional tests. However, TIL have been compared usually with peripheral blood T lymphocytes, raising doubts on the conclusions drawn. Therefore, we compared TIL from B cell non-Hodgkin's lymphomas (NHL) with T cells from nonmalignant secondary lymphoid organs. NHL-TIL were unresponsive to activation by immobilized anti-CD3 mAb, although bypassing T cell receptor (TCR)/CD3 signaling led to proliferation. The poor proliferative responses of NHL-TIL could not be explained by quantitative defects in TCRzeta expression. NHL-TIL underwent marked spontaneous apoptosis in vitro with loss of approximately 50% of cells after 24 h of culture. This was associated with downregulation of the antiapoptotic Bcl-xL and Bcl-2 proteins, whereas viable NHL-TIL maintained their expression. IL-2, anti-CD3/IL-2, and manipulation of the Fas/Fas-ligand death pathway had no effect on NHL-TIL survival. Apoptosis was not due to increased cell cycling, as NHL-TIL were quiescent, nonproliferating cells. T cells from inflammatory, nonmalignant tissues gave similar functional results to NHL-TIL, suggesting the existence of factors common to the microenvironment of these diverse pathologies. Thus, the quiescent, anergic phenotype of NHL-TIL cannot be attributed solely to tumor factors, but rather is a feature of T cells from chronic inflammatory lesions.