Partial purification of an immunosuppressive protein from a human tumor cell line and analysis of its relationship to transforming growth factor beta

TGFbeta protein processing and activity through TCR triggering of primary CD8+ T regulatory cells

In general, TGFbeta is synthesized as a procytokine that requires proteolytic activation, release of the mature cytokine from its noncovalently associated latent-associated peptide, and binding to TGFbetaRII to mediate suppressive activity. We tracked this process in mice containing primed CD8 regulatory T cells (Tregs) by immunoblotting in primary whole cell lysates for pro-TGFbeta, latent-associated peptide and mature TGFbeta. Generation of CD8 Tregs promoted processing of the 50 kDa pro-TGFbeta protein into a 12.5 kDa mature TGFbeta species in vivo. Despite the inability to detect mature TGFbeta in the sera of mice with primed CD8 Tregs and in the synthetic culture medium of stimulated CD8 Tregs, we demonstrated engagement of TGFbetaRII through immunoblotting for Smad2 phosphorylation. This process relied on continual TCR triggering, which also induced Smad3 phosphorylation. To understand the movement of mature TGFbeta, we showed that in contrast to IFN-gamma, mature TGFbeta does not remain a soluble cytokine but is likely to be rapidly adsorbed by neighboring cells. These data show the exquisite local control directed toward TGFbeta by the immune system and underscore the fine specificity involved in its detection.

Retention of transforming growth factor beta1 using functionalized dextran-based hydrogels

Functionalized dextrans (FD) are anionic water-soluble polymers bearing carboxylate, benzylamide and sulfate groups, which exhibit binding capacity to transforming growth factor-beta1 (TGF-beta1). In this paper, we have investigated the ability of dextran-based hydrogels containing FD, to bind and release recombinant human TGF-beta1. Hydrogels were prepared by chemical crosslink native dextran and FD with sodium trimetaphosphate in 1m NaOH at 50 degrees C. A wide range of hydrogels were prepared as particles ranging of 1-1.6mm of diameter and characterized with various amounts of FD and with different crosslinker feeding ratios (CFR). Dried particles were soaked with recombinant human transforming growth factor-beta1 (rhTGF-beta1) to determine their capacity to deliver the growth factor. Results indicated that the in vitro kinetics releases of rhTGF-beta1 were related to FD and CFR. Retention capacity of rhTGF-beta1 increases with an increase of negative charges of the matrices brought by both phosphate linkages and FD as demonstrated by an additional release of growth factor in high ionic strength solution. Highly crosslinked hydrogels that contained the highest amount of FD (18% (w/w)) retained up to 88% of rhTGF-beta1. Bioactivity of released growth factor was confirmed in a cell assay. These functionalized hydrogels may have important uses for the stabilization and the protection of rhTGF-beta1 as entrapment systems and could be applied to other proteins of clinical interest.

Characterization of the A673 cell line (Ewing tumor) by molecular cytogenetic techniques

The A673 cell line was established from a patient with a primary rhabdomyosarcoma (RMS), which is referred to in the literature either as a Ewing tumor (ET) or as RMS. Although the two tumoral types are associated with specific and well-characterized translocations, no cytogenetic report on this cell line has been published. We characterized the A673 cell line using a combination of spectral karyotyping (SKY), fluorescence in situ hybridization (FISH), and reverse transcriptase polymerase chain reaction (RT-PCR), which revealed the presence of a complex karyotype and a translocation involving chromosomes 11 and 22 and the fusion of EWS and FLI1 genes, both events being specific to ET. Neither cytogenetics nor molecular alterations specific to RMS were found.

Evaluation of pooled platelet concentrates using prestorage versus poststorage WBC reduction: impact of filtration timing

BACKGROUND

Concern for the undesirable consequences of transfusing passenger WBCs is leading to the general use of WBC-reduced platelet concentrates (PCs). However, the impact of prestorage versus poststorage WBC reduction on the quality of platelet products has not been clearly defined.

STUDY DESIGN AND METHODS

Pooled PCs were WBC reduced before or after 5-day storage, by use of a WBC filter (PXL-8, Pall Corp.). Samples from pools were taken on days 1 and 5, before and after filtration, and on Day 9 of storage and assessed for cell counts, biochemical values, expression of platelet glycoproteins, thrombin generation, and content of IL-6, IL-8, TNFalpha, transforming growth factor beta1 (TGFbeta1), and anaphylatoxins C3a and C4a.

RESULTS

Filtration of fresh and 5-day-stored pooled PCs via a PXL-8 filter was similarly efficient, rendering pools with low WBC counts (<1 x 10(6) cells) and high platelet recovery (>95%). No major changes were found in the metabolic behavior or the expression of platelet GPIb, GPIIb/IIIa, CD62, and CD63 in PCs filtered before or after storage. Filtration, either before or after storage, increased by less than 5 percent the proportion of CD62+ platelets. Moreover, no changes were found in the concentration of prothrombin fragments 1 and 2 and thrombin-antithrombin complexes in the pooled PCs derived from the time of filtration. Finally, prestorage WBC reduction abrogated the accumulation of IL-6 and IL-8, but it did not prevent that of anaphylatoxins C3a and C4a nor of TGFbeta1. However, filtration through a PXL-8 filter significantly reduced (40-90%) the amount of IL-8, C3a, and C4a in the filtrate.

CONCLUSIONS

The timing of PXL-8 filtration of PCs has little impact on the efficiency of WBC reduction and on platelet recovery, and it does not seem to affect the quality of platelets or the generation of thrombin in the PCs. As regards the goal of reducing the amount of bioactive products in PCs, it remains uncertain as to whether prestorage WBC reduction fully eliminates the need for poststorage filtration. Prestorage filtration leads to low levels of IL-6 and IL-8 in PCs, but it does not impair the poststorage content of TGFbeta1 or anaphyla-toxins. By contrast, poststorage PXL-8 filtration removes significant amounts of C3a and C4a, and thus it might provide clinical benefits beyond those of prestorage WBC reduction.

A Pathogenic Role of Th2 Cells and Their Cytokine Products on the Pulmonary Metastasis of Murine B16 Melanoma

The role of Th2 cells and the cytokines produced by these cells on experimental pulmonary metastasis of B16 melanoma was investigated in a murine model implanted with high metastatic (B16F10) or low metastatic (B16F1) melanoma cells. An average of 250 colonies of metastasis in the lungs was counted in mice (BF10 mice) at 14 days after the inoculation of 2 × 105 B16F10 cells/mouse, while &lt;20 colonies were detected in mice (BF1 mice) inoculated with the same number of B16F1 cells. CD4+CD11b+TCR-αβ+ T cells (BF10-Th2 cells) were produced in the spleens of BF10 mice, while these cells were not detected in BF1 mice. The BF10-Th2 cells produced IL-4 and IL-10 into culture fluids when stimulated in vitro with anti-CD3 mAb. However, IL-2 and IFN-γ were not produced. The level of a pulmonary metastasis in BF1 mice increased to the level observed in BF10 mice, when BF10-Th2 cells were adoptively transferred to BF1 mice. Also, an increase in the number of pulmonary melanoma was demonstrated in BF1 mice treated with 10 μg/kg murine rIL-4. The level of pulmonary metastasis in BF10 mice or in BF1 mice inoculated with BF10-Th2 cells decreased to the level observed in BF1 mice when mice were treated with an anti-IL-4 mAb at a dose of 250 μg/kg on days 1, 3, and 5 after tumor inoculation. These results suggest that the severity of pulmonary metastasis in mice receiving B16 melanoma cells is strongly influenced by the IL-4 released from tumor-associated Th2 cells.

Involvement of a transforming-growth-factor-beta-like molecule in tumor-cell-derived inhibition of nitric-oxide synthesis in cerebral endothelial cells

Nitric oxide (NO) has been shown to exert cytotoxic effects on tumor cells. We have reported that EC219 cells, a rat-brain-microvessel-derived endothelial cell line, produced NO through cytokine-inducible NO synthase (iNOS), the induction of which was significantly decreased by (a) soluble factor(s) secreted by DHD/PROb, an invasive sub-clone of a rat colon-carcinoma cell line. In this study, the DHD/PROb cell-derived NO-inhibitory factor was characterized. Northern-blot analysis demonstrated that the induction of iNOS mRNA in cytokine-activated EC219 cells was decreased by PROb-cell-conditioned medium. When DHD/PROb cell supernatant was fractionated by affinity chromatography using Con A-Sepharose or heparin-Sepharose, the NO-inhibitory activity was found only in Con A-unbound or heparin-unbound fractions, respectively, indicating that the PROb-derived inhibitory factor was likely to be a non-glycosylated and non-heparin-binding molecule. Pre-incubation of DHD/PROb-cell supernatant with anti-TGF-beta neutralizing antibody completely blocked the DHD/PROb-derived inhibition of NO production by EC219 cells. Addition of exogenous TGF-beta 1 dose-dependently inhibited NO release by EC219 cells. The presence of active TGF-beta in the DHD/PROb cell supernatant was demonstrated using a growth-inhibition assay. Moreover, heat treatment of medium conditioned by the less invasive DHD/REGb cells, which constitutively secreted very low levels of active TGF-beta, increased both TGF-beta activity and the ability to inhibit NO production in EC219 cells. Thus, DHD/PROb colon-carcinoma cells inhibited NO production in EC219 cells by secreting a factor identical or very similar to TGF-beta.

Autocrine and paracrine functions of cytokines in malignant lymphomas

Cytokines play important roles in the pathogenesis of lymphomas via an autocrine or a paracrine mechanism, or both. The characteristic clinical and histopathological features of malignant lymphomas may be due in part to elevated serum or tissue levels of cytokines. Determination of the effects of cytokines on the growth or differentiation of lymphoma cells is often complicated by the fact that more than one cytokine is responsible, and by the failure of anti-cytokine antibodies or antisense oligonucleotides to block the proliferation in vitro of lymphoma cells. However, it appears that IL-6 and/or IL-9 may play a prominent role in the tumor cell proliferation of Hodgkin's disease (HD), anaplastic large-cell lymphoma, or immunoblastic lymphoma. IL-6 may also be responsible for the plasmacytoid differentiation of lymphoma cells in polymorphic immunocytoma. The histopathological changes as a result of paracrine effects are most noticeable in HD. The malignant (H-RS) cells of HD have been shown to express IL-1, IL-5, IL-6, IL-9, TNF-alpha, M-CSF, TGF-beta, and CD80, and, less frequently, IL-4 and G-CSF. These cytokines may be responsible for the increased cellular reaction and fibrosis observed in tissues involved by HD and for the immunosuppression found in patients with HD. In contrast to H-RS cells, most non-HD lymphoma cells do not produce cytokines in excess amounts and reveal only a minimal cellular reaction. Exceptions include T-cell-rich B-cell lymphoma, angiocentric T-cell lymphoma, and angio-immunoblastic lymphadenopathy (AILD-like T-cell lymphoma. IL-4 is responsible for the T-cell reaction in T-cell-rich B-cell lymphoma, whereas IL-6 accounts for the plasma cell reaction in AILD-type T-cell lymphoma. The authors extensively review the role of cytokines in lymphomas because this may lead to major advances in the understanding of the molecular processes involved in the histopathogenesis of lymphomas.

Immunotherapy with low-dose interleukin-2 and anti-transforming growth factor-beta antibody in a murine tumor model

The purpose of the present study was to evaluate the therapeutic efficacy of low-dose interleukin-2 (IL-2) alone or together with antibody against transforming growth factor-beta (TGF-beta) in a Herpes simplex virus Type 2-transformed (H238) fibrosarcoma model. BALB/c mice were inoculated subcutaneously (s.c.) with 5 x 10(5) H238 tumor cells in one or both hind thighs and treated with IL-2, anti-TGF-beta, or a combination of both agents. Nontreated tumor-bearing and normal animals served as controls. In the appropriate treatment groups, each mouse was given a total of 10(5) international units (i.u.) of IL-2 s.c. at one tumor implantation site and/or 1 microgram of anti-TGF-beta intraperitoneally (i.p.) over a period of 5 days beginning on the day of tumor cell implantation. No toxicity was noted during treatment. The slowest tumor growth was observed in mice with single tumors when treated with IL-2 or anti-TGF-beta alone, whereas combination treatment resulted in growth similar to that of untreated controls. However, in animals with two tumors, the tumor injected with IL-2 grew more rapidly than the untreated one. Spleen cell responsiveness to mitogenic stimulation was generally depressed in tumor-bearing mice compared to normal controls, but some differences were noted with treatment. In contrast, tumor presence induced striking splenomegaly and enhanced the chemiluminescent oxidative burst of phagocytic cells in the spleen. In the groups with a single tumor, plasma TGF-beta levels were similar to those of nontumor-bearing controls, however the concentrations were decreased in the animals with two tumors. These results show that IL-2 or anti-TGF-beta can slow progression of H238 tumors under certain conditions. However, combination of the two modalities proved to be of no benefit.

Cytokines in malignant lymphomas: review and prospective evaluation

Cytokines play important roles in the pathogenesis of lymphomas. Cytokines either can be produced or exert effects on neoplastic or reactive cells. The secretion of cytokines can provide growth advantages for tumor cells in either an autocrine or a paracrine fashion. An elevated serum or tissue level of cytokines can contribute to the clinical and histopathologic alterations associated with malignant lymphomas. The effects of cytokines on the histopathologic changes are most noticeable in Hodgkin's disease (HD). The malignant (Hodgkin's-Reed-Sternberg) cells in HD have been shown to secrete interleukin-1 (IL-1), IL-5, IL-6, IL-9, tumor necrosis factor-alpha, macrophage colony-stimulating factor, transforming growth factor-beta, and, less frequently, IL-4 and granulocyte colony-stimulating factor. These cytokines may be responsible for the increased cellular reaction and fibrosis observed in tissues involved by HD and for the immunosuppression in patients with HD. In contrast to Hodgkin's-Reed-Sternberg cells, most non-HD lymphoma cells do not produce cytokines in excess amounts. Exceptions include T-cell-rich B-cell lymphoma (IL-4), angioimmunoblastic lymphadenopathy-like T-cell lymphoma with plasmacytosis and hypergammaglobulinemia (IL-6), anaplastic large-cell lymphoma (IL-9), polymorphic immunocytoma (IL-6), and immunoblastic lymphoma (IBL) (IL-6). Some cytokines are involved in the unique cellular reactions in each of these types of lymphoma. For example, IL-4 is responsible for the T-cell reaction in T-cell-rich B-cell lymphoma, while IL-6 is accountable for the plasma cell reaction in angioimmunoblastic lymphadenopathy-type T-cell lymphoma. Others may be directly involved in the tumor cell growth or differentiation. For instance, IL-9 may be important for the autocrine proliferation of anaplastic large cell lymphoma, whereas IL-6 is essential for plasmacytoid differentiation in polymorphic immunocytoma. Further studies of the roles of cytokines in lymphomas may lead to major advances in the understanding of the molecular processes involved in the histopathogenesis of malignant lymphomas. Elucidation of the autocrine or paracrine function of cytokines also may lead to new approaches to a rational intervention in these disease processes.

Modulation of transforming growth factor-beta 1 effects by cytokines

The purpose of the present study was to determine the effects of human recombinant transforming growth factor-beta 1 (TGF-beta 1) on the proliferation of normal cell and cancer cell lines and to evaluate the mechanism of TGF-beta-induced immunosuppression. Murine H238 fibrosarcoma and human UC-11 glioblastoma cells showed no proliferative change in the presence of TGF-beta, whereas the growth of human LS174T colon adenocarcinoma cells was significantly enhanced at the lower concentrations of TGF-beta. In contrast, Mono/Mac-6, a human monocyte cell line, human peripheral blood mononuclear (PBMN) cells, and BALB/c mouse spleen cells were significantly suppressed by 2.5 to 250 ng/ml of TGF-beta. In order to investigate the mode of action, TGF-beta and other cytokines were added 0, 1, and 2 days after initiation of the culture. Mono/Mac-6 cells showed that 2 days are needed for TGF-beta-induced suppression. Simultaneous addition of TGF-beta and tumor necrosis-alpha (TNF-alpha; 600 units/ml) to Mono/Mac-6 cells resulted in nearly complete suppression by day 3. IL-2, and to a lesser extent IL-4, was able to counteract the suppressive effects of TGF-beta on mitogen-stimulated spleen cells. However, our results indicate that IL-2 is not as effective in restoring responsiveness once T cell activation is well underway. IL-1 and interferon-gamma had no effects on TGF-beta-mediated immunosuppression. Since TGF-beta depressed normal cell growth and since IL-2 could effectively counteract the suppression, we assayed for IL-2 production. When normal spleen cells were treated with 2.5 ng of TGF-beta/ml, a 3.4-fold decrease in IL-2 production was observed. This is a potential mechanism for TGF-beta-mediated immunosuppression.

Abundant expression of transforming growth factor-beta 1 and -beta 2 by Hodgkin's Reed-Sternberg cells and by reactive T lymphocytes in Hodgkin's disease

The depressed cellular immunity observed in patients with Hodgkin's disease (HD) has been attributed to production of transforming growth factor (TGF)-beta or TGF-beta-like substances by Hodgkin's Reed-Sternberg (H-RS) cells. The TGF-beta produced by L-428 cells (an H-RS cell line) is a 130-kd molecular weight glycoprotein that apparently differs from the TGF-beta (molecular weight, 25 kd) produced by most lymphoid and hematopoietic cells. Among several distinct types of TGF-beta that have been purified, only TGF-beta 1 and TGF-beta 2 have thus far been identified in hematopoietic cells. By using monoclonal antibodies (1D11 and 3C7) and oligonucleotide probes specific for TGF-beta 1 and TGF-beta 2, were confirmed that a cultured H-RS cell line, KM-H2, can produce both TGF-beta types, whereas another line, HDLM-1, produces only TGF-beta 1. Despite the abundance of mRNA in both of these cells, only small amounts of TGF-beta activity were detected, probably because of rapid degradation of TGF-beta 1 mRNA by specific nuclease. No degraded TGF-beta 2 RNA products were observed in KM-H2 cells. The TGF-beta produced by both types of H-RS cells had a molecular weight of approximately 25 kd. In tissues expression of TGF-beta was observed in a small portion (30%) of H-RS cells in 16 of 20 cases examined. A large number of small to medium-sized lymphoid cells (T lymphocytes) in tissues involved by HD also were positive for TGF-beta. These results indicate that there is functional heterogeneity among H-RS cells, and that H-RS cells are not the only source of TGF-beta in tissues involved by HD. Hodgkin's Reed-Sternberg cells are known to secrete several other cytokines, including interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha. These cytokines could be responsible for the increased number of T lymphocytes in tissues involved by HD. Furthermore, T lymphocytes can respond to IL-1 and IL-6 secreted by H-RS cells by increasing their production of TGF-beta. Abundant expression of TGF-beta by T lymphocytes was not observed in lymphoid tissues other than those involved by HD.

Structural study on a phosphorylated mannotetraose obtained from the phosphomannan of Candida albicans NIH B-792 strain by acetolysis

A mixture of phosphorylated manno-oligosaccharides was isolated from the acid-stable domain of phosphomannan of Candida albicans NIH B-792 strain (serotype B) by acetolysis and was fractionated on a column of Bio-Gel P-2 equilibrated with 50 mM pyridine-CH3COOH buffer, pH 5.0. A monophosphorylated mannotetraose was isolated as the major constituent. Structural analyses of this phosphate-containing tetraose and its reduction product with NaBH4 by 1H, 13C, and two-dimensional homonuclear Hartmann-Hahn NMR spectroscopies, subsequently, gave results consistent with the structure described below (where Manp represents the mannopyranose unit): [formula: see text] It was unexpected that the major phosphorylated branch in the acid-stable domain of the parent phosphomannan of this C. albicans strain is a relatively short mannotetraosyl residue containing solely alpha-1,2-linked mannopyranose units, and a phosphate group as a 6-O-ester on the intermediary unit adjacent to the nonreducing terminal group. These findings indicate that the size of the major phosphorylated branch of this phosphomannan is the same as that of Saccharomyces cerevisiae.

Suppression of immune responses by herpes virus type 2-transformed murine tumor cells

Work done in our laboratories, using a murine model, indicates that suppression of host immune responses might be due to secretion of soluble factors by tumor cells. The H238 cells (BALB/c embryonic fibroblasts transformed by UV-inactivated herpes simplex virus Type 2) exhibit progressive tumor growth with subsequent decrease in lymphoproliferation. To further study the suppressive effects of a tumor, H238 conditioned medium (CM) was tested for its ability to block murine and human mitogenic and allogeneic lymphocyte responses. PHA, Con A and LPS were used as mitogens. Lymphoproliferation, in the presence of increasing amounts of H238 CM, resulted in a greater degree of suppression of [3H]thymidine ([3H]Tdr) uptake, in both human and mouse systems. The kinetics of proliferation in the presence of concentrated H238 CM (cCM) showed that depression was evident regardless of the time of cCM addition, thereby affecting it at any stage of the cell cycle. Treatment of H238 cCM using acid (pH 2.3), base (pH 9.6), trypsin (100 micrograms/ml), heat (56 degrees C, 100 degrees C) and freeze-thawing, restored PHA-stimulated lymphoproliferation. Dialysis of H238 cCM showed that the molecular weight of the suppressor lies between 15 and 25 kDa. Northern blot analysis demonstrated the presence of a TGF-beta transcript in H238 cells. Neutralization of the H238 cCM with monoclonal antibody to TGF-beta resulted in complete abrogation of suppressive activity in spleen cell lymphoblastogenesis. These results suggest that TGF-beta appears to be the main inhibitor of immune responses found in this HSV-2-induced murine tumor cell line. Such tumor-induced modulations may contribute to the outcome of immunotherapy in the tumor-bearing host.