Arsenic trioxide down-regulates antiapoptotic genes and induces cell death in mycosis fungoides tumors in a mouse model.

BACKGROUND: Mycosis fungoides (MF) is the most frequent cutaneous T-cell lymphoma (CTCL). Arsenic trioxide (As(2)O(3)) has recently been shown to be effective against leukemias, so we studied whether As(2)O(3) induces apoptosis of CTCL cells in vitro. We further investigated if As(2)O(3) is effective in a MF mouse model. MATERIAL AND METHODS: Annexin V/7-amino-actinomycin-D stainings were carried out to investigate if As(2)O(3) induced apoptosis of CTCL cell lines. To study the underlying mechanisms, the effects of As(2)O(3) on various transcription factors and apoptosis regulating proteins were analyzed by western blots, electrophoretic mobility shift assays and transcription factor enzyme-linked immunosorbent assays. The ability of As(2)O(3) to induce tumor regression was investigated in a MF mouse model. RESULTS: As(2)O(3)-induced apoptosis was paralleled by a reduction of the DNA-binding activities of transcription factors of the NFkB and signal transducer and activator of transcription gene families and reduced expression of the antiapoptotic proteins bcl-1, bcl-xL and mcl-1. Local injections of 200 muM As(2)O(3) into tumors caused complete remissions in five of six mice and one partial remission. CONCLUSIONS: As(2)O(3) induced apoptosis of CTCL cells by the down-regulation of transcription factors that stimulate the expression of antiapoptotic genes. Local injection of As(2)O(3) into MF tumor-bearing mice resulted in tumor regression.

The molecular pathogenesis of mycosis fungoides and Sézary syndrome.

Mycosis fungoides (MF) and the Sézary syndrome (Sz) are the two most frequent forms of cutaneous T cell lymphomas (CTCL). Generally the Sz is regarded as a leukemic variant of MF. They are caused by malignant CD4+ T cells, which infiltrate the skin and both diseases proceed in different stages. It has been found in colon carcinoma that cancerogenesis is a sequence of activation of different oncogenes and inactivation of tumor suppressor genes. This finding has initiated efforts to identify the genes that are responsible for the progression of MF and Sz. The development of new screening methods has strongly accelerated this search and many oncogenes and tumor suppressor genes have been identified that may play a role in the progression of both diseases. Changes in the expression of some of these genes are already found at early stages, whereas others become active or inactivated only in later stages. These results will help to search for more specific drugs and lead to a more exact staging that will help to develop effective and personalized treatments of these diseases.

Interleukin-7 and interleukin-15 regulate the expression of the bcl-2 and c-myb genes in cutaneous T-cell lymphoma cells.

Interleukin-7 (IL-7) and IL-15 have been recently identified as growth factors for cutaneous T-cell lymphoma (CTCL) cells, and they protect these cells from cell death. Using the CTCL cell line SeAx as a test system now shows that IL-7 and IL-15 are indeed necessary to maintain high levels of bcl-2. The up-regulation of bcl-2 was paralleled by increased DNA-binding activities of the transcription factors STAT2, STAT5, STAT6, and c-Myb to bcl-2 gene promoter-enhancer elements. Because STAT5 and c-Myb positively regulate bcl-2, IL-7 and IL-15 may mediate some of their effects on cell death survival gene expression through these 2 factors. Constitutive activities of the 3 STAT factors and c-Myb were found in the IL-7- and IL-15-independent CTCL cell lines HUT78 and MyLa 2059. The c-Myb protein was also present in CTCL cells of the skin lesions of all investigated patients. These results indicate that IL-7 and IL-15 may increase bcl-2 expression in CTCL cells by the activation of c-myb and STAT factors.

Constitutive and interleukin-7- and interleukin-15-stimulated DNA binding of STAT and novel factors in cutaneous T cell lymphoma cells.

On testing cutaneous T cell lymphoma cell lines and skin lesions, we found that the transcription factors STAT2, STAT3, STAT5, and STAT6 (STAT, signal transducer and activator of transcription) were present in the nuclei of these cells and that the binding to their specific DNA binding sites was stimulated by interleukin-7 and interleukin-15. DNA binding studies also revealed the presence of three additional DNA factors in cutaneous T cell lymphoma cells that bound to the same sequences and could also be stimulated by interleukin-7 and interleukin-15. One of these novel factors was also present in the adult T cell leukemia cell line Jurkat and malignant T cells from the blood of Sézary syndrome patients, but not in normal peripheral blood lymphocytes. It may therefore be a marker of T cell leukemia. It seems to interfere with the binding of STAT1 to the sis inducible element, suggesting that the DNA binding activity of STAT1 in cutaneous T cell lymphoma cells is disturbed.

[Current pathogenetic aspects of Sézary syndrome and mycosis fungoides]. / Aktuelle Aspekte zur Pathogenese von Sézary-Syndrom und Mycosis fungoides.

Cutaneous T-cell lymphomas are a heterogeneous group of lymphoproliferative skin disorders whose pathogenesis is poorly understood. Cytokines and chemokines are important factors which can modify the cutaneous microenvironment allowing the accumulation of lymphocytes. Most of these neoplasms seem to be T helper-2 cells. While interferon gamma is the natural inhibitor of clonal T-cell proliferations, interferon resistance has been recently found in these cells. This interferon resistance may be an Achilles heel that can be targeted by molecular therapeutic interventions.

Interferon resistance of cutaneous T-cell lymphoma-derived clonal T-helper 2 cells allows selective viral replication.

Cutaneous T-cell lymphomas (CTCL) comprise a heterogeneous group of lymphoproliferative disorders that are characterized by an accumulation of T-lymphocytes in the skin and occasionally in blood known as Sézary syndrome (SS). In most cases the dominant clone displays T-helper 2 cytokines. Because IFN-gamma is a natural inhibitor of T-helper 2 cells and IFN-alpha is frequently used in CTCL, the impact of IFNs on SS-derived purified clonal T-helper 2 cells was studied using anti-Vbeta antibodies. Moreover, IFNs are known to mediate virus resistance in normal cells. The isolated clonal CD4(+) cells, but not the nonclonal CD4(+) cells, appeared resistant to IFN-gamma and IFN-alpha stimulation in terms of human leukocyte antigen up-regulation and MxA induction caused in part by alterations in Stat-1 molecule mRNA and IFNgammaR1 mRNA transcription. The IFN resistance of the patient-derived clonal cells was then targeted by vesicular stomatitis virus infection after IFN-alpha priming, resulting in selective viral replication in clonal cells. In contrast, nonclonal cells of the same patient showed IFN-dependent MxA expression, which is a major mediator protein of viral protection. The IFN resistance of the dominant T-helper 2 cells might be important for lymphomagenesis. Interferon signaling deficiencies can be targeted for purging patients' cells in vitro. Furthermore, this approach may allow specific molecular interventions, resulting in the efficient treatment of CTCL and other IFN-resistant neoplasms such as lung cancer.

Pathogenesis of cutaneous lymphomas.

Cutaneous lymphomas are a heterogeneous group of lymphoproliferative disorders derived from T cells, B cells and, in rare cases, natural killer cells. The precise mechanisms of the lymphomagenesis are still obscure. However, there are various factors involved. These factors include environmental, especially infectious factors, translocations, mutations and genetic instability. The special microenvironment in the skin is responsible for the peculiar behavior of these neoplasms by providing various key factors, such as adhesion molecules and cytokines. Newly identified molecular disturbances in cutaneous lymphomas might be targeted by specific molecular or immunologic interventions in the future.

CD4 + /CD7- T cell frequency and polymerase chain reaction-based clonality assay correlate with stage in cutaneous T cell lymphomas.

In cutaneous T cell lymphomas, tumor cells can be found in skin and in other compartments. A precise definition of extracutaneous spread including blood involvement is necessary for staging and treatment design. We investigated peripheral blood in 51 patients with various types of cutaneous T cell lymphomas by the analysis of blood smears for Sézary cells, the CD4 + /CD7- T helper cell frequency in the peripheral blood by fluorescence activated cell sorter analysis and by polymerase chain reaction for the T cell receptor gamma-chain followed by denaturing gradient gel electrophoresis. Eleven polymerase chain reaction products were sequenced. Thirty-five per cent of patients with stage Ia-IIb cutaneous T cell lymphomas presented a peripheral blood T cell clone. In patients with stage III-IVb cutaneous T cell lymphomas 75% were positive for clonality in the peripheral blood by polymerase chain reaction. Interestingly, three of 13 Sézary patients showed a TCR-gamma joining region pseudogene (JgammaP1/JgammaP2) usage. CD4 + /CD7- cell counts were significantly higher in patients with advanced cutaneous T cell lymphomas than in patients with early cutaneous T cell lymphomas. There was a correlation between increased percentage of circulating CD4 + /CD7- cells and detection of clonality by polymerase chain reaction (p = 0.001). There was no significant correlation between the polymerase chain reaction data and the percentage of Sézary cells on blood smears. A significant correlation between CD4 + /CD7- cells and Sézary cells was found, however. Stepwise logistic regression analysis showed that the CD4 + /CD7- cell count and clonal T cell detection in peripheral blood are independently correlated with stage. The combination of both parameters gives more information than each one separately. In conclusion, our data indicate that fluorescence activated cell sorter analysis of peripheral blood and polymerase chain reaction-based clonality assays can improve the accuracy of staging investigations in cutaneous T cell lymphomas patients.

Constitutive and interleukin-7/interleukin-15 stimulated DNA binding of Myc, Jun, and novel Myc-like proteins in cutaneous T-cell lymphoma cells.

Members of the Myc and Jun/Fos gene families have been found to be expressed in late stages of cutaneous T-cell lymphoma (CTCL) and may be responsible for the transition from low-grade to high-grade tumors. The composition of these complexes is an important parameter, as the different homo- and heterodimeric jun and myc complexes can have gene transcription activating or suppressing activities. We determined the composition of the jun and myc DNA-binding complexes in three CTCL cell lines and malignant cells of seven Sézary patients by electrophoretic mobility shift assays (EMSAs) and "supershift" assays in which specific antibodies against the different members of the tested gene families were included in the binding reactions. Complexes containing JunD were found in three cell lines and two patients. The three cell lines and one patient contained also c-Myc/Max heterodimers. Because c-Myc/Max heterodimers are strong gene transcription activators and are necessary for cell-cycle progression, they may play a role in the progression of CTCL. JunD may also promote cell-cycle progression and influence the expression of cell death survival genes. Interleukin-7 (IL-7) and IL-15, which have been identified as growth factors for CTCL cells, stimulated the DNA binding of JunD and two novel c-Myc recognition site (E-box) binding proteins, but not the DNA binding of c-Myc/Max heterodimers.

Interleukin-15 is an autocrine/paracrine viability factor for cutaneous T-cell lymphoma cells.

In this study we investigated the role of interleukin-15 (IL-15) in the immunobiology of cutaneous T-cell lymphoma (CTCL) cells. Using cell culture techniques, reverse transcriptase-polymerase chain reaction (RT-PCR), and immunhistochemistry we found that IL-15, like IL-7, is a growth factor for the Sézary cell line SeAx and that both cytokines prolonged the survival of malignant T cells directly isolated from Sézary syndrome (SS) patients. Both IL-15 and IL-7 were more potent than IL-2. IL-4 and IL-9, whose receptors share the same gamma chain with the receptors of IL-2, IL-7, and IL-15, did not sustain the growth of CTCL cells, indicating that signaling through the common gamma chain (gammac) is not sufficient for continuous growth. IL-13 and tumor necrosis factor-alpha (TNF-alpha) had no effect. IL-7 and IL-15 also supported the growth of SeAx cells in the presence of the apoptosis inducing agents dexamethasone and retinoic acid. The analysis of patient Sézary cells and three CTCL cell lines by RT-PCR showed that all these cells expressed IL-15 mRNA, but only a few (25%) produced IL-7 mRNA. Immunohistological analyses of skin biopsy samples of SS and Mycosis fungoides patients showed immunoreactivity for IL-15 in basal cell layer keratinocytes and in the infiltrating lymphocytes. We conclude that IL-15 is a growth or viability factor for CTCL-derived cell lines or shortly cultivated Sézary cells. The findings that IL-15 mRNA can be detected in Sézary syndrome peripheral blood mononuclear cells and that the IL-15 protein is detected in skin sections from CTCL patients suggest that IL-15 plays an important role in the biology of CTCL.

A realistic approach to the sensitivity of PCR-DGGE and its application as a sensitive tool for the detection of clonality in cutaneous T-cell proliferations.

The practical value of the detection of clonality within the T-cell receptor gamma locus by polymerase chain reaction for the diagnosis of cutaneous T-cell lymphomas is well known. However, studies dealing with this subject so far, with special emphasis on the sensitivity of the technique in comparison to, for example, Southern blotting have used mixtures of DNA in various concentrations instead of using mixtures of the cells involved, which would reflect the in vivo situation in a more realistic scope. The purpose of this study was therefore to determine the sensitivity and the limitations of the PCR assay by dilution experiments, using mixtures of cells. Furthermore we studied its applicability to cutaneous T-cell proliferative disorders. Two clonal T-cell lines (MyLa and Jurkat) served as positive control. Dilutions of MyLa cells, cultured normal human keratinocytes and peripheral blood mononuclear cells from lymphoma negative volunteers were used to assess the sensitivity of the PCR-DGGE assay. Skin samples from 4 patients with cutaneous T-cell lymphoma, 1 lesional lymph node, 2 blood samples from a patient with Sézary syndrome and 4 lymphoma-negative tissue samples were analysed. Two samples were uncertain for diagnosis of lymphoma. The PCR-DGGE assay consisted of a 2-round nested PCR with consensus primers within the TCR-gamma locus followed by electrophoretic separation of the product along a denaturing urea/formamide gradient gel. PCR-DGGE sensitivity was, to our knowledge, for the first time investigated for mixtures of lymphocytes (clonal and polyclonal) and keratinocytes. Clonal T-cells were detected in a concentration between 1-0.1% in keratinocytes, whereas the sensitivity was generally lower upon dilution in peripheral blood mononuclear cells or in a mixture of keratinocytes and peripheral blood mononuclear cells. Nevertheless, T-cell clonality was detected in 2 blood samples of a patient with Sézary syndrome, which were negative by Southern blot analysis. The crucial point of this work was the new approach to establish the sensitivity of the PCR-DGGE, in a way which more closely mimics the condition of clinical specimens. Instead of mixing and amplifying DNA extracted from clonal T-cell lines and polyclonal bone marrow cells, we amplified DNA from clonal and polyclonal cells which had been mixed in various ratios before DNA extraction. Polymerase chain reaction in conjunction with denaturing gradient gel electrophoresis is a sensitive and versatile molecular tool for the assessment of clonality of suspect cutaneous lesions. The determination of sensitivity using DNA extracted from premixed cells more closely corresponds to the actual test situation when testing skin samples.

The effects of cyclosporin A on V(D)J recombination activity.

V(D)J recombination is up-regulated by the protein kinase A (PKA) pathway and down-regulated by the protein kinase C (PKC) and Ca2+ pathways. When activators of the PKA and PKC pathways or the PKA and Ca2+ pathways are given at the same time, a strong reduction of the PKA effect is observed. The V(D)J recombination suppressing effect of elevated intracellular Ca2+ levels, but not that of the PKC pathway, can be abrogated by the addition of the calcineurin inhibitor cyclosporin A (CsA), indicating that the effect of Ca2+ is mediated by calcineurin. This effect is observed in a pre B cell line as well as in the V(D)J recombination competent fibroblast cell line L4, indicating that the mechanisms of the cross talk between different signalling pathways are basically the same in both cell types. In the absence of Ca2+ mobilizer CsA increases the V(D)J recombination rate in pre B cells but not in L4 cells.

Lack of expression of the recombination activating genes RAG-1 and RAG-2 in cutaneous T-cell lymphoma: pathogenic implications.

Analyses of the karyotype and genome of cutaneous T-cell lymphoma (CTCL) cells have shown that they contain chromosome breaks and translocations. The sequence analyses of such DNA breakpoints found in various kinds of leukaemias have suggested that some of the observed translocations have been caused by illegitimate V(D)J (v = Variability; D = diversity; J = joining) recombination. To study whether illegitimate V(D)J recombination is responsible for the continuously increasing number of DNA breaks in CTCL, we used reverse transcriptase polymerase chain reaction (RT-PCR) to analyse three CTCL cell lines and biopsies from 14 CTCL patients for the expression of the RAG-1 and RAG-2 genes which are essential for V(D)J recombination. We found no RAG gene expression in any of the 17 samples analysed, indicating that illegitimate V(D)J recombination may not be the reason for the increased number of chromosomal aberrations and translocations in CTCL cells.

The influence of IL-7 V(D)J recombination.

The influence of interleukin-7 (IL-7) on V(D)J recombination was investigated directly in the V(D)J recombination competent pre-B-cell line 38B9. The addition of IL-7 to the medium reduced the V(D)J recombination rate by 52-64%. This reduction was insensitive to the addition of cyclosporin A, indicating that the repression by IL-7 is not mediated by phosphatase 2B. The repression mechanism of IL-7 did not synergize with those of the protein kinase C activator 12-O-Tetradecanoylphorbol-13-acetate (TPA) and the intracellular Ca2+ mobilizer thapsigargin. The actin of IL-7 blocked by the addition of the protein kinase A stimulator caffeine and the synthetic glucocorticoid dexamethasone. IL-7 did not change the m-RNA levels of the V(D)J recombination activating genes RAG-1 and RAG-2, therefore IL-7 must exert its influence on V(D)J recombination either by post-transcriptional regulation of the RAG genes or by the regulation of other genes that are involved in V(D)J recombination. Although IL-7 may be necessary for the induction of and maintenance of V(D)J recombination during some stages of lymphocyte precursor development, it reduces the V(D)J recombination activity in pre-B cells.

The transcription factor Oct2A enhances V(D)J recombination in fibroblasts.

The influence of the transcription factor Oct2A on V(D)J recombination was investigated. It was found that co-transfection of Oct2A together with an artificial recombination substrate increased the rate of V(D)J recombination by a factor of 3.4 in the fibroblast cell line L4 which had been stably transfected with genomic DNA containing the rag-1 and rag-2 genes and their flanking regulatory sequences. This effect, however, was not observed in the pre-B-cell line 38B9. The effect of Oct2A depends on the presence of its transactivation domains indicating that Oct2A increase the transcription of genes that increase the rate of V(D)J recombination. This effect can be reversed by additional co-transfection of the glucocorticoid receptor. In contrast to L4 cells Oct2A and the glucocorticoid receptor had no effect in 38B9 cells. From these results one may conclude that the effect of Oct2A is masked in 38B9 cells by endogenous Oct2A and other redundant pre-B-cell-specific transcription factors and that it can only be seen in cells lacking these factors.

Glucocorticoids regulate the expression of the stressprotein alpha B-crystallin.

alpha B-crystallin is a major component of the eye lens but is also found in many extralenticular tissues. In established fibroblasts it is synthesized in response to stress such as hyperthermia. Here we report that the treatment of NIH3T3 fibroblasts with the synthetic glucocorticoid hormone dexamethasone resulted in the accumulation of substantial amounts of alpha B-crystallin, alpha B-crystallin mRNA accumulated slowly and over a period of many days in response to prolonged hormone treatment. alpha B-crystallin promoter-reporter constructs were hormone responsive. A putative glucocorticoid response element (GRE) within the analysed promoter region could bind the glucocorticoid receptor as revealed from in vitro footprint analysis but is not involved in the hormone-mediated gene activation. Deletions of 5' flanking regions to position -465 relative to the transcription start allowed for full hormone responsiveness. A deletion from -465 to -389 abolish hormone-mediated gene induction. No sequence element closely resembling a classical GRE is present within that hormone-responsive region.

The effects of transfected mutant and wild type RAG genes in different cell types.

The ability to perform V(D)J recombination can be transferred to non-lymphoid cells by stable or transient transfection of the RAG genes. This fact was used to test the effect of wild type and mutant RAG-genes on the V(D)J recombination activity in recombination competent and incompetent cells. Cotransfection of wild type RAG genes induced V(D)J recombination in NIH 3T3 fibroblasts, but had no effect in the pre B cell line 38B9 and even reduced the recombination activity of the fibroblast cell line L4 which has been stably transfected with both RAG genes, indicating that these cell lines lack co-factors which are necessary for higher recombination activity. A mutant RAG-1 gene which lacks a part of the topoisomerase I-like region and a mutant RAG-2 gene which lacks its 89 C-terminal amino acids did not activate V(D)J recombination in NIH 3T3 cells. They did not decrease the recombination activity in L4 cells, but increased the V(D)J recombination activity in 38B9 cells, probably by protecting endogenous wild type RAG mRNAs and proteins against RNAses and proteinases. Treatment respectively co-transfection of NIH 3T3 cells with the V(D)J recombination stimulating agent caffeine and the lymphoid specific transcription factor Oct2A did not lead to induction of V(D)J recombination in the absence of RAG genes.

Down-regulation of the protein kinase A pathway by activators of protein kinase C and intracellular Ca2+ in fibroblast cells.

Many genes are regulated by the intracellular calcium, protein kinase C (PKC) and protein kinase A (PKA) pathways and it has been shown that these pathways synergize in some cell types, whereas they antagonize in others. Here we show that the calcium and PKC pathways suppress the effects mediated by the PKA pathway in a fibroblast cell line. The suppressing effect of elevated intracellular Ca2+ levels, but not of the PKC pathway, can be abrogated by the addition of cyclosporin A (CsA), indicating that the effect of Ca2+ is mediated by phosphatase-2B (PP-2B/calcineurin). Suppression by the PKC pathway is not mediated by the proto-oncogenes c-fos, c-jun and junB, as the co-transfection of these genes does not block the effects of the PKA stimulator 8-Br-cAMP. In addition, cotransfection with the catalytic subunit of PKA shows that the inhibitory effect of PKC occurs upstream of PKA activation.

V(D)J recombination is regulated similarly in RAG-transfected fibroblasts and pre-B cells.

Here we compare the regulation of V(D)J recombination in the fibroblast cell line L4 and the pre-B cell line 38B9. The former has been rendered recombination-competent by stable transfection of a genomic fragment comprising the recombination activating genes, RAG-1 and RAG-2, along with some of their flanking sequences. We show that V(D)J recombination is similarly regulated in these two cell lines. Activating signals are transmitted through the protein kinase A (PKA) pathway, and inhibitory signals through the protein kinase C (PKC) and the calcium signalling pathways. In both cell lines, recombinational activity reflects steady state levels of mRNA transcribed from the RAG-1 and RAG-2 genes. This suggests that transcription of the RAG genes is a major determinant regulating V(D)J recombination. A comparison of RAG-1 and RAG-2 mRNA levels within each cell line reveals almost identical response patterns indicating that RAG-1 and RAG-2 transcription is coordinately regulated. Together, these results imply that the RAG-containing fragment in L4 fibroblasts carries most, if not all, control regions regulating the transcription of the RAG-1 and RAG-2 genes.