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IntroductionCutaneous T-cell lymphomas (CTCL) are the most frequent primary lymphomas of the skin, with mycosis fungoides (MF) being the most prevalent clinical form. 1 In early disease stages, which can last several years, MF presents as flat erythematous skin patches resembling inflammatory diseases such as allergic contact dermatitis, eczema, or psoriasis. In later stages, MF lesions gradually form plaques and overt tumors and may disseminate to lymph nodes and internal organs. The early skin lesions contain numerous inflammatory cells, including a large quantity of T cells with a normal phenotype as well as a small population of T cells with abnormal morphology and a malignant phenotype. T cells with a malignant phenotype are characterized by epidermotropism and are preferentially present in the upper parts of the skin, whereas T cells with a normal phenotype primarily are detected in the lower portions of the dermis. The epidermal T cells are sometimes found in patterns of Pautrier microabscesses, which are collections of T cells adherent to dendritic processes of Langerhans cells. During disease development, the epidermotropism is gradually lost concomitant with an increase in malignant, and a decrease in nonmalignant, infiltrating T cells. The etiology of CTCL remains poorly understood, and occupational exposures, infectious agents, and genetic mutations have been proposed as etiological factors, but no evidence of causation has been provided. [2][3][4][5][6] However, already in early disease stages, the transcription factor nuclear factor-kappa B (NF-B) has been shown to be constitutively active in the malignant T cells of patients with CTCL where it promotes proliferation and cell survival. [7][8][9] The malignant T cells also show aberrant hyperactivation of the Janus kinase 3 (Jak3)/signal transducer and activator of transcription 3 (Stat3) pathway, which protects them from apoptosis and is a marker of resistance to therapy. [10][11][12][13] It has been hypothesized that the aberrant activation of NF-B and the Jak3/Stat3 pathway are key events in the development of CTCL. [7][8][9][10] Early diagnosis of CTCL has important consequences concerning therapeutic options and determination of prognosis. 14 Currently, it is primarily based on clinical observations and histologic examinations of cutaneous biopsies as well as additional laboratory tests such as analysis of T-cell receptor (TCR) clonality by polymerase chain reaction (PCR). Unfortunately, early diagnosis of CTCL has proven difficult because of the great clinical, pathologic, and histologic resemblance to benign inflammatory skin diseases and because inflammatory skin disorders can be associated with clonal TCR rearrangements. [15][16][17][18] In humans, the Src family kinases (SFKs) of nonreceptor protein tyrosine kinases classically consists of 8 members: c-Src, Fyn, Lck, c-Yes, Fgr, Hck, Lyn, and B-lymphoid kinase (Blk). 19 Blk is exclusively expressed in B cells and thymocytes but not in mature T cells. [20][21][22] Besides a role of Blk in B...

Mutated BRAF and NRAS are suspected to contribute to melanomagenesis by activation of extracellular signal-regulated kinase (ERK). To test this notion, we analyzed the presence of phosphorylated ERK1/2 in 170 melanomas with established NRAS/BRAF mutational status and well-documented clinical follow-up by immunohistochemistry. Several notable observations were obtained: (i) phospho-ERK staining was very heterogeneous within the tumor; (ii) in most cases, ERK was phosphorylated in only a minority of tumor cells; (iii) the percentage of phospho-ERK-positive cells was not correlated with the mutational status of NRAS and/or BRAF; (iv) the Raf kinase inhibitor protein (RKIP) was expressed homogeneously in virtually all melanoma samples not reflecting the inhomogeneity of phospho-ERK; and, finally, (v) neither the portion of phospho-ERK-positive tumor cells nor the RKIP staining intensity showed any correlation to the clinical course of the patients. Furthermore, the ability of BRAF mutant melanoma cells to downregulate mitogen-activated protein kinase activation was shown in melanoma cell lines cultured at high densities or under nonadherent conditions. Our findings suggest that mitogen-activated protein kinase (MAPK) activity is subject to regulation even in BRAF/NRAS mutant melanoma cells and that high MAPK pathway signaling may be important only in distinct subsets of tumor cells.

Merkel cell carcinoma (MCC) is a highly metastatic skin tumor. To assess the relevance of the Ras/Raf/MEK/MAP kinase pathway, we analyzed for activating B-Raf mutations and we elucidated the presence of the Raf Kinase Inhibitor Protein (RKIP) and extracellular signal-regulated kinase (ERK) as well as the phosphorylation status of ERK. All MCC samples were negative for the B-Raf(V600E) mutation. Remarkably, RKIP, which was shown to interfere with the activation of MEK by Raf, was highly expressed in primary as well as in metastatic MCC. Immunohistochemical analysis of the phosphorylation status of ERK revealed in 42 out of 44 samples a complete lack of activated ERK in the tumor cells although ERK is expressed; in the two positive cases phosphorylated ERK was restricted to a minor fraction of the tumor cells. Western blot analysis of three MCC-derived cell lines revealed in one case the pattern present in situ (i.e. high RKIP expression and complete absence of phosphorylated ERK). In summary, our data demonstrate the inactivity of the classical MAP kinase signal transduction pathway in MCC, which seems to be because of lack of activation as well as active deactivation. These findings should be accounted for in future therapeutic approaches for this tumor.

CD147 is highly expressed on many tumor cells; its role for tumor invasiveness and metastasis has been deduced from its capacity to induce MMPs, i.e., MMP-1, -2, -3, and -9. However, in the murine B16 melanoma model, MMP-2/-9 expression occurs independent of CD147. To scrutinize the impact of CD147 on metastasis formation and angiogenesis in this model, CD147 was stably knocked down in B16 cells. This silencing of CD147 expression resulted in a reduced capability of the tumor cells to metastasize to the draining lymph nodes. Notably, the CD147 knock down caused a decreased VEGF expression in vivo accompanied by reduced blood vessel formation. Thus, in the B16 melanoma model, CD147 promotes metastasis formation by induction of angiogenesis in an MMP independent manner.

Inter-α-trypsin inhibitors are protease inhibitors that are thought to be important regulators in various acute-phase processes. They are composed of one light chain (bikunin) and different heavy chains (ITIHs). The only function known so far of ITIHs is the covalent linkage to hyaluronan (HA). As there is virtually no knowledge on the distribution and function of ITIH proteins in skin tissue, we performed a systematic characterization of ITIH expression in healthy and diseased skin. Using GeneChip(®) Human Exon 1.0 ST expression profiling, we found that ITIH5 represents the major ITIH family member expressed in human skin. Moreover, the use of quantitative reverse transcription PCR and a customized ITIH5-specific antibody indicated that ITIH5 is predominantly produced by dermal fibroblasts. Immunohistochemical analysis revealed a clearly detectable ITIH5 protein expression in normal skin. Interestingly, ITIH5 expression was significantly up-regulated in inflammatory skin diseases. Furthermore, 3D skin models employing murine Itih5(-/-) epidermal keratinocytes and dermal fibroblasts as well as skin specimens of Itih5(-/-) mice revealed a significantly altered epidermal structure compared to wild-type controls. Hence, we can strengthen the presumption that ITIH5 may constitute a novel regulatory molecule of the human skin that could play an important role in inflammation via its interaction with HA.

ConclusionsSeverely altered expression of the T-cell receptor/CD3 complex, T-cell receptor-associated transcription factors and signal transduction molecules is a common characteristic of systemic and cutaneous CD30 + lymphoproliferations, although the clinical behavior of these entities is very different. Since peripheral T-cell lymphomas, not otherwise specified retain the full expression program required for functioning T-cell receptor signaling, the differential expression of a subset of these markers might be of diagnostic utility in distinguishing peripheral T-cell lymphomas, not otherwise specified from the entire group of CD30 + lymphoproliferations.Key words: systemic and cutaneous CD30 + lymphoproliferations, anaplastic large cell lymphoma, lymphomatoid papulosis, ALCL, LyP, TCR.Citation: Geissinger E, Sadler P, Roth S, Grieb T, Puppe B, Müller N, Reimer P, Vetter-Kauczok CS, Wenzel J, Bonzheim I, Rüdiger T, Müller-Hermelink HK, and Rosenwald A. Disturbed expression of the T-cell receptor/CD3 complex and associated signaling molecules in CD30+ T-cell lymphoproliferations. Haematologica 20010;95(10):1697-1704. doi:10.3324/haematol.2009 This is an open-access paper. Disturbed expression of the T-cell receptor/CD3 complex and associated signaling molecules in CD30 + T-cell lymphoproliferations © F e r r a t a S t o r t i F o u n d a t i o nIntroduction CD30 + T-cell lymphoproliferations comprise a spectrum of clinically heterogeneous entities, including systemic anaplastic large cell lymphomas (ALCL) as well as primary cutaneous CD30 + T-cell lymphoproliferative disorders. Morphologically, these entities are characterized by the proliferation of highly atypical, anaplastic CD30 + T cells. Despite the frequent detection of clonally rearranged Tcell receptor (TCR) genes, the expression of T-cell-specific antigens in the tumor cells is not consistently detectable. 1 Systemic ALCL comprise approximately 15% of all peripheral T-cell lymphomas (PTCL) in Europe 2 and are divided into anaplastic lymphoma kinase (ALK) positive and negative subgroups (ALK + and ALK -systemic ALCL), whereas primary cutaneous CD30 + T-cell lymphoproliferative disorders represent a spectrum of skin lesions with diverging and in part overlapping clinical and morphological features. CD30 + T-cell lymphoproliferative disorders include primary cutaneous ALCL, lymphomatoid papulosis and so-called borderline lesions, [3][4][5] but even with the knowledge of the clinical presentation and a detailed morphological and immunohistochemical picture it is sometimes difficult, if not impossible, to classify a particular cutaneous lesion correctly.While the transforming properties of ALK over-expression have been clearly demonstrated ,6,7 the transformation mechanisms in ALK -systemic ALCL and primary cutaneous CD30 + T-cell lymphoproliferative disorders are poorly understood. CD30 itself, a cytokine receptor belonging to the tumor necrosis factor receptor superfamily, has been a research focus over the past years, but whether CD30 signaling lea...

Here, we have studied vascular endothelial growth factor receptor-3 (VEGFR-3) expression in mycosis fungoides (MF), the most common type of cutaneous T-cell lymphoma (CTCL). Immunohistochemistry revealed that in two-thirds of 34 patients, VEGFR-3 was expressed in situ by both tumor and stromal cells irrespective of the disease stage. The natural VEGFR-3 ligand, VEGF-C, partially protected malignant T-cell lines from growth inhibition by the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA). Whereas the malignant T cells did not produce VEGF-C in vitro, its expression was induced during tumor formation in vivo in a xenograft mouse model of MF. In conclusion, malignant and stromal cells express high levels of VEGFR-3 in all stages of MF. Moreover, malignant T cells trigger enhanced VEGF-C expression in fibroblasts, suggesting that cross-talk between tumor and stromal cells plays a role in lymphangiogenesis and possibly disease progression.