A characteristic feature of neoplastic transformation is a perpetual activation of oncogenic proteins. Here, we studied signal transducers and activators of transcription (STAT) in patients with mycosis fungoides (MF)/cutaneous T-cell lymphoma (CTCL). Malignant lymphocytes in dermal infiltrates of CTCL tumors showed frequent and intense nuclear staining with anti-PY-STAT3 antibody, indicating a constitutive activation of STAT3 in vivo in tumor stages. In contrast, only sporadic and faint staining was observed in indolent lesions of patch and plaque stages of MF. Moreover, neoplastic lymphocytes in the epidermal Pautrier abscesses associated with early stages of MF did not express activated STAT3. To address the role of STAT3 in survival/apoptosis, CTCL tumor cells from an advanced skin tumor were transfected with either wild-type STAT3 (STAT3wt) or dominant-negative STAT3 (STAT3D). Forced inducible expression of STAT3D triggered a significant increase in tumor cells undergoing apoptosis, whereas forced expression of STAT3wt or empty vector had no effect. In conclusion, a profound in vivo activation of STAT3 is observed in MF tumors but not in the early stages of MF. Moreover, STAT3 protects tumor cells from apoptosis in vitro. Taken together, these findings suggest that STAT3 is a malignancy factor in CTCL.

No abstract

Via cytoplasmic signal transduction pathways, cytokines induce a variety of biological responses and modulate the outcome of inflammatory diseases and malignancies. Crohn's disease is a chronic inflammatory bowel disease of unknown etiology. Perturbation of the intestinal cytokine homeostasis is believed to play a pivotal role, but the pathogenesis of Crohn's disease is not fully understood. Here, we study intestinal T cells from Crohn's disease and healthy volunteers. We show that STAT3 and STAT4 are constitutively activated in Crohn's patients but not in healthy volunteers. The activation is specific, because other STAT proteins are not constitutively activated. Furthermore, the STAT3 regulated protein, SOCS3, is also constitutively expressed in Crohn's patients but not in healthy volunteers. Taken together, these data provide evidence of abnormal STAT/SOCS signaling in Crohn's disease. This aberrant activation, so far noted only in malignant cells, establish a new critical approach for better understanding the immunopathogenesis of Crohn's disease.

Substances that penetrate the skin surface can act as allergens and induce a T cell-mediated inflammatory skin disease called contact hypersensitivity (CHS). IL-17 is a key cytokine in CHS and was originally thought to be produced solely by CD4+ T cells. However, it is now known that several cell types including γδ T cells can produce IL-17. Here, we determine the role of γδ T cells, especially the dendritic epidermal T cells (DETC), in CHS. By use of a well-established model for CHS where dinitroflourobenzen (DNFB) is used as allergen, we found that γδ T cells are important players in CHS. Thus, an increased number of IL-17 producing DETC appear in the skin following exposure to DNFB in WT mice, and DNFB-induced ear-swelling is reduced by approximately 50% in TCRδ−/− mice compared to WT mice. In accordance, DNFB-induced ear-swelling was reduced by approximately 50% in IL-17−/− mice. We show that DNFB triggers DETC activation and IL-1β production in the skin, and that keratinocytes produce IL-1β when stimulated with DNFB. We find that DETC activated in vitro by incubation with anti-CD3 and IL-1β produce IL-17. Importantly, we demonstrate that the IL-1 receptor antagonist anakinra significantly reduces CHS responses as measured by decreased ear-swelling, inhibition of local DETC activation and a reduction in the number of IL-17+ γδ T cells and DETC in the draining lymph nodes. Taken together, we show that DETC become activated and produce IL-17 in an IL-1β-dependent manner during CHS suggesting a key role for DETC in CHS.

Atopic dermatitis (AD) is a widespread, chronic skin disease associated with aberrant allergic inflammation. Current treatments involve either broad or targeted immunosuppression strategies. However, enhancing the immune system to control disease remains untested. We demonstrate that patients with AD harbor a blood natural killer (NK) cell deficiency that both has diagnostic value and improves with therapy. Multidimensional protein and RNA profiling revealed subset-level changes associated with enhanced NK cell death. Murine NK cell deficiency was associated with enhanced type 2 inflammation in the skin, suggesting that NK cells play a critical immunoregulatory role in this context. On the basis of these findings, we used an NK cell–boosting interleukin-15 (IL-15) superagonist and observed marked improvement in AD-like disease in mice. These findings reveal a previously unrecognized application of IL-15 superagonism, currently in development for cancer immunotherapy, as an immunotherapeutic strategy for AD.

Psoriasis is a chronic inflammatory skin disease characterized by abnormal epidermal proliferation. Several studies have shown that skin-infiltrating activated T cells and cytokines play a pivotal role during the initiation and maintenance of the disease. Interferon (IFN)-alpha plays an important role in host defense against infections, but recent data have also implicated IFN-alpha in psoriasis. Thus, IFN-alpha induces or aggravates psoriasis in some patients, and mice lacking a transcriptional attenuator of IFN-alpha/beta signaling spontaneously develop a psoriasis-like inflammatory skin disease characterized by CD8(+)-infiltrating T cells. In this study, we therefore investigate IFN-alpha signaling in T cells isolated from involved skin of psoriatic patients. We show that psoriatic T cells have increased and prolonged responses to IFN-alpha, on the level of signal transducers and activators of transcription (STAT) activation, compared with infiltrating T cells from skin of non-psoriatic donors. Functionally, the increased IFN-alpha signaling leads to an increased binding of STAT4 to the IFN-gamma promotor, IFN-gamma production, and inhibition of T cell growth. In contrast, to STAT responses to other cytokines were not changed in psoriasis. In conclusion, we provide evidence that psoriatic T cells have an increased sensitivity to IFN-alpha. Thus, our data suggest that increased IFN-alpha signaling is involved in the pathogenesis of psoriasis.

The chronic skin inflammation psoriasis is crucially dependent on the IL-23/IL-17 cytokine axis. Although IL-23 is expressed by psoriatic keratinocytes and immune cells, only the immune cell-derived IL-23 is believed to be disease relevant. Here we use a genetic mouse model to show that keratinocyte-produced IL-23 is sufficient to cause a chronic skin inflammation with an IL-17 profile. Furthermore, we reveal a cell-autonomous nuclear function for the actin polymerizing molecule N-WASP, which controls IL-23 expression in keratinocytes by regulating the degradation of the histone methyltransferases G9a and GLP, and H3K9 dimethylation of the IL-23 promoter. This mechanism mediates the induction of IL-23 by TNF, a known inducer of IL-23 in psoriasis. Finally, in keratinocytes of psoriatic lesions a decrease in H3K9 dimethylation correlates with increased IL-23 expression, suggesting relevance for disease. Taken together, our data describe a molecular pathway where epigenetic regulation of keratinocytes can contribute to chronic skin inflammation.

In summary, we demonstrate a unique and supplementary immune modulatory effect of calcipotriol/betamethasone combination on TNF-α and IL-23/Th17 immune axis, supporting the superior clinical efficacy of the combination product compared to the respective mono-treatments in psoriasis patients.