Prognostic factors for primary cutaneous anaplastic large-cell lymphoma: a multicentre retrospective study from Japan.

BACKGROUND: The clinical implications of DUSP22 rearrangement and the association between DUSP22 rearrangement and lymphoid enhancer-binding factor 1 (LEF1) expression pattern in CD30+ cutaneous T-cell lymphomas (CTCLs) are unknown. OBJECTIVES: This study assessed the incidence of DUSP22 rearrangement and its clinical and immunohistochemical implications in primary cutaneous anaplastic large-cell lymphoma (pcALCL), lymphomatoid papulosis (LyP) and CD30+ mycosis fungoides with large-cell transformation (MF-LCT), focusing especially on the association with the prognosis and LEF1 expression pattern. Prognostic factors of pcALCL were also examined. METHODS: We conducted a multicentre retrospective study including patients with pcALCL, LyP and MF-LCT diagnosed between 1 January 2000 and 31 December 2018 in Japan. Baseline data at diagnosis, treatment course, overall survival (OS) and disease-specific survival (DSS) were collected. Immunohistochemical analysis and fluorescence in situ hybridization to detect DUSP22 and TP63 rearrangement were performed using skin samples at diagnosis. We investigated the association between staining pattern and these gene rearrangements. We also assessed the prognostic implications of clinical status, immunohistochemical results and the presence of gene rearrangements. RESULTS: DUSP22 rearrangement was detected in 50% (11 of 22) of cases of pcALCL, but not in any cases with LyP (0 of 14) or MF-LCT (0 of 11). TP63 rearrangement was not detected in any case. Clinically, patients with pcALCL with DUSP22 rearrangement did not tend to develop ulcers (P = 0.081). There was no significant association between DUSP22 rearrangement status and immunohistochemical results, including LEF1 expression pattern. T3 stage and the presence of lower limb lesions were significantly associated with shorter OS (P = 0.012 and 0.021, respectively, by log-rank test). Similarly, they were significantly correlated with shorter DSS (P = 0.016 and 0.0001, respectively). CONCLUSIONS: DUSP22 rearrangement is relatively specific to pcALCL among CD30+ CTCLs in Japan. Although the LEF1 expression pattern was not related to DUSP22 rearrangement in pcALCL, there was no rearrangement if LEF1 was not expressed. We confirmed that T3 stage and the lower limb involvement were significantly associated with decreased OS and DSS. The presence or absence of lower limb lesions should be included in T-stage subcategorization in the future.

Increased expression of squamous cell carcinoma antigen 1 and 2 in mycosis fungoides and Sézary syndrome

Background: Squamous cell carcinoma antigen (SCCA) was originally isolated as tumour-specific antigens in uterine cervix carcinoma. These comprise two similar proteins, SCCA1 and SCCA2, and both are induced by type 2 cytokines such as interleukin (IL)-4 and IL-13. The involvement of these antigens in atopic dermatitis has been reported, however, the role in mycosis fungoides (MF) and Sézary syndrome (SS), which are also linked with type 2 cytokines, remains to be seen. Objectives: This study investigated a possible association between SCCA1/2 and MF/SS. Materials & Methods: We compared serum levels of SCCA1/2 between MF/SS patients and healthy controls. We also examined the correlation between serum SCCA1/2 levels in MF/SS patients and clinical disease markers. The expression of SCCA1/2 in skin samples was examined by immunohistochemistry. Results: The serum levels of SCCA1/2 in MF/SS patients were significantly higher than those in normal controls and correlated with clinical disease markers. Immunohistochemical staining showed upregulated expression of SCCA1/2 in MF/SS lesional skin. Conclusion: Enhanced SCCA1/2 expression may contribute to the progression of MF/SS. Measurement of serum SCCA1/2 levels may become a useful tool to evaluate the progression or therapeutic effects of MF/SS.

Roles of OX40 and OX40 Ligand in Mycosis Fungoides and Sézary Syndrome.

Mycosis fungoides (MF) and Sézary syndrome (SS), the most common types of cutaneous T-cell lymphoma (CTCL), are characterized by proliferation of mature CD4+ T-helper cells. Patients with advanced-stage MF and SS have poor prognosis, with 5-year survival rates of 52%. Although a variety of systemic therapies are currently available, there are no curative options for such patients except for stem cell transplantation, and thus the treatment of advanced MF and SS still remains challenging. Therefore, elucidation of the pathophysiology of MF/SS and development of medical treatments are desired. In this study, we focused on a molecule called OX40. We examined OX40 and OX40L expression and function using clinical samples of MF and SS and CTCL cell lines. OX40 and OX40L were co-expressed on tumor cells of MF and SS. OX40 and OX40L expression was increased and correlated with disease severity markers in MF/SS patients. Anti-OX40 antibody and anti-OX40L antibody suppressed the proliferation of CTCL cell lines both in vitro and in vivo. These results suggest that OX40-OX40L interactions could contribute to the proliferation of MF/SS tumor cells and that the disruption of OX40-OX40L interactions could become a new therapeutic strategy for the treatment of MF/SS.

CD147-Cyclophilin a Interactions Promote Proliferation and Survival of Cutaneous T-Cell Lymphoma.

CD147, a transmembrane glycoprotein that belongs to the immunoglobulin superfamily, and cyclophilin A (CypA), one of the binding partners of CD147, are overexpressed in tumor cells and associated with the progression of several malignancies, including both solid and hematological malignancies. However, CD147 and CypA involvement in cutaneous T-cell lymphoma (CTCL) has not been reported. In this study, we examined CD147 and CypA expression and function using clinical samples of mycosis fungoides (MF) and Sézary syndrome (SS) and CTCL cell lines. CD147 and CypA were overexpressed by tumor cells of MF/SS, and CypA was also expressed by epidermal keratinocytes in MF/SS lesional skin. Serum CypA levels were increased and correlated with disease severity markers in MF/SS patients. Anti-CD147 antibody and/or anti-CypA antibody suppressed the proliferation of CTCL cell lines, both in vitro and in vivo, via downregulation of phosphorylated extracellular-regulated kinase 1/2 and Akt. These results suggest that CD147-CypA interactions can contribute to the proliferation of MF/SS tumor cells in both a autocrine and paracrine manner, and that the disruption of CD147-CypA interactions could be a new therapeutic strategy for the treatment of MF/SS.

Mycosis fungoides and Sézary syndrome tumor cells express epidermal fatty acid-binding protein, whose expression decreases with loss of epidermotropism.

Fatty acid binding protein (FABP) is a family of transport proteins for fatty acid (FA). Epidermal FABP (E-FABP) is highly expressed by resident memory T cells (TRM ) in the skin. It supports the uptake of exogenous FA for long-term survival of skin TRM . Mycosis fungoides (MF) is regarded as malignancy of skin TRM . In this study, we investigated E-FABP expression in psoriasis vulgaris (PV), atopic dermatitis (AD), MF, and Sézary syndrome (SS). E-FABP mRNA levels in PV were much higher than those in healthy controls. E-FABP mRNA levels in AD and MF/SS lesional skin were also significantly higher than those of normal skin. By immunohistochemical staining, E-FABP was positive in MF/SS lesional skin. Interestingly, E-FABP was stained positive in epidermotropic lymphoid cells in patch, plaque, and erythrodermic lesions of MF/SS, suggesting that a part of tumor cells expressed E-FABP. In tumorous lesions, however, most dermal tumor cells were negative for E-FABP. Immunohistochemical staining using patch/plaque lesions and tumorous lesions from the same patients also revealed that E-FABP expression decreased in tumorous lesions. Our study has suggested that MF/SS tumor cells express E-FABP, whose expression decreases with loss of epidermotropism.

Mycosis Fungoides and Sézary Syndrome: Updates and Review of Current Therapy.

OPINION STATEMENT: While most patients with early-stage mycosis fungoides (MF) follow an indolent course, patients with advanced-stage MF/Sézary syndrome (SS) have a poor prognosis with a median survival of less than 5 years. Although there are a number of treatments currently available, achieving and maintaining a durable response remain challenging, especially in advanced-stage MF/SS. The choice of frontline therapy is dependent on the stage of disease. For early-stage MF, the treatment concept is to control skin lesions mainly by skin-directed therapies, such as topical therapies, phototherapies, and radiotherapies. For advanced-stage MF/SS, systemic treatments by biological or targeted therapies including bexarotene and interferon either alone or in combination are tried first, with more immunosuppressive chemotherapies being reserved for refractory or rapidly progressive disease. Recent improvements in biological or targeted therapies include brentuximab vedotin and mogamulizumab. When biopsy samples have 10% or more CD30-positive malignant cells, brentuximab vedotin, an anti-CD30 antibody conjugated to monomethyl auristin E, can be a desirable treatment option. For cases with blood involvement, mogamulizumab, an antibody binding to C-C chemokine receptor 4, is effective with high response rates. In the refractory setting, alemtuzumab, histone deacetylase inhibitors, pralatrexate, gemcitabine, and doxorubicin are considered as the treatment option. Because only allogeneic hematopoietic stem cell transplantation can offer a chance of cure with durable complete remission, advanced-stage patients with a markedly short life expectancy should be evaluated for eligibility. Given that there are few randomized controlled studies in the literature, it is necessary to investigate which therapy is preferable for each patient with MF/SS by comparative prospective trials.

Increased Expression of Delta-like Ligand 4 in Mycosis Fungoides.

In many malignancies, dysregulation of the Notch pathways, composed of 4 Notch receptors (Notch1-4) and 5 Notch ligands (Jagged1-2, Delta-like ligand-1, 3-4), is associated with their development. In mycosis fungoides, interaction between Notch1 and Jagged1 is known to activate the Notch pathways and promote the proliferation of tumour cells. However, the involvement of other Notch ligands has not been reported. This study investigated the roles of Delta-like ligand 4 in mycosis fungoides. Delta-like ligand 4 mRNA levels in lesional skin of patients with mycosis fungoides were significantly elevated compared with those of normal controls, and correlated with disease-specific mortality. Immunohistochemical staining demonstrated prominent expression of Delta-like ligand 4 on vascular endothelial cells and tumour cells in mycosis fungoides lesional skin. In addition, Delta-like ligand 4 augmented the proliferation of cutaneous T-cell lym-phoma cell lines. These results suggest that enhanced Delta-like ligand 4 expression may contribute directly to the progression of mycosis fungoides through proliferating tumour cells.

Primary cutaneous γδ T-cell lymphoma with unusual immunophenotype: A case report and review of published work.

Primary cutaneous γδ T-cell lymphoma (CGD-TCL) is a rare form of primary cutaneous lymphoma. The histopathological features of CGD-TCL are still unclear because of its rarity. Here, we report a case of a 77-year-old Japanese man who presented with a 9-month history of erythematous plaques on his left forearm. Skin biopsy specimens revealed the infiltration of atypical medium/large-sized lymphocytes from the epidermis to the deep dermis. Atypical lymphocytes were positive for CD3, CD5, CD8 and Vδ1, and negative for CD4, CD7, CD56, EBER-ISH, intracellular antigen-1, granzyme B and perforin. CD30 was partially expressed. We also reviewed 246 cases of CGD-TCL from the published work. CD4- CD8- double-negative cases were 113 of 196 cases (57.6%), followed by CD4- CD8+ cases (52/196, 26.5%). CD5 was expressed in 25.8% of the cases (34/132). At least one cytotoxic molecule marker was expressed in 150 of 160 cases (93.8%). Some cases showed an indolent clinical course, especially in mycosis fungoides-like CGD-TCL cases. CD5 positivity and lack of cytotoxic molecule expression could be associated with a better prognosis. In addition, CD30 expression was found in approximately half of CGD-TCL cases (51/112 cases), suggesting that brentuximab vedotin could be a good treatment option for such patients. Further studies with more cases with detailed clinical and pathological information are necessary to elucidate the etiology and prognostic markers of this entity.

Increased IL-26 Expression Promotes T Helper Type 17- and T Helper Type 2-Associated Cytokine Production by Keratinocytes in Atopic Dermatitis.

Whereas atopic dermatitis (AD) is considered as a T helper 2 (Th2)-centered disease, IL-17-producing Th (Th17) cells are also activated in AD lesional skin. However, the relationship between Th17 responses and Th2 responses in AD is still to be elucidated. Although Th17 cells are increased in AD skin, the expression and function of IL-26, which is also produced by Th17 cells, in AD are still unknown. In this report, we demonstrated that IL-26 mRNA expression levels were elevated in AD lesional skin compared with healthy controls and that IL-26-producing cells were increased in AD lesional skin by immunohistochemistry. Furthermore, IL-26 promoted IL-8, IL-1ß, chemokine (C-C motif) ligand 20, IL-33, and ß-defensin 2 production in keratinocytes through phosphorylation of signal transducer and activator of transcription 1 and signal transducer and activator of transcription 3. Selective JAK inhibitors for JAK1, JAK2, and tyrosine kinase 2 blocked IL-26-induced cytokine production in keratinocytes. We also showed that injection of IL-26 exacerbated an oxazolone-induced AD mouse model and upregulated Th2 and Th17 cytokine expression in vivo. Because previous studies indicate that the above molecules induced by IL-26 can promote Th17 and/or Th2 immune responses, IL-26 may play an important role for bridging between Th17 and Th2 responses, resulting in the development of AD.

YKL-40 Promotes Proliferation of Cutaneous T-Cell Lymphoma Tumor Cells through Extracellular Signal-Regulated Kinase Pathways.

YKL-40, one of the chitinase-like proteins, is associated with the pathogenesis of a wide variety of human diseases through modulation of inflammation and tissue remodeling by its diverse roles in cell proliferation, differentiation, and survival. Emerging evidence shows that aberrantly expressed YKL-40 promotes the development of malignancies by inducing proliferation of tumor cells, cytokine production, and angiogenesis by acting on various stromal cells, immune cells, and tumor cells. In this study, we investigated the expression and function of YKL-40 in cutaneous T-cell lymphoma (CTCL). We first revealed that serum YKL-40 levels were increased in patients with CTCL and correlated with disease severity markers. We also found that YKL-40 was expressed by epidermal keratinocytes and tumor cells in lesional skin of CTCL by immunohistochemistry. Although YKL-40 did not affect cytokine production from CTCL cell lines, YKL-40 promoted the proliferation of Hut78 cells and HH cells in vitro, which was dependent on extracellular signal-regulated kinase 1/2 pathways. Moreover, exogenous YKL-40 administration enhanced tumor growth of HH cells in vivo. Our study has suggested that YKL-40 produced from epidermal keratinocytes and CTCL cells promoted the proliferation of CTCL cells through extracellular signal-regulated kinase 1/2 pathways in autocrine and paracrine manners, leading to development of CTCL.

Thrombospondin-1 promotes tumor progression in cutaneous T-cell lymphoma via CD47.

CD47 is highly expressed on various hematopoietic malignancies, and enables cancer cells to avoid immunosurveillance. Its ligand, thromobospondin-1 (TSP-1) is a multifunctional protein, and CD47/TSP-1 interactions promote tumor progression in various malignancies. In this study, we investigated roles of TSP-1 and CD47 in cutaneous T-cell lymphoma (CTCL). Flow cytometric analysis and immunohistochemistry showed that CTCL tumor cells and CTCL cell lines (Hut78, HH, and MyLa cells) overexpressed CD47 compared with normal CD4+ T cells. Overexpression of CD47 was partially induced by high c-Myc expression in CTCL tumor cells. TSP-1 mRNA expression levels in CTCL lesional skin were higher than those in normal skin and correlated with increased risk of disease-related death. Moreover, TSP-1 was expressed on CTCL tumor cells by immunohistochemistry. Serum soluble TSP-1 levels in patients with Sézary syndrome were significantly elevated. TSP-1 promotes proliferation and survival of CTCL tumor cells, which is inhibited by anti-CD47 neutralizing antibody or CD47 knockdown. Stimulation with TSP-1 also induces cell migration and in vivo growth. These effects were mediated by phosphorylation of ERK1/2 and AKT and expression of survivin. Collectively, our findings prompt a novel therapeutic approach to CTCL based on discovery that CD47/TSP-1 interactions play important roles in progression of CTCL.

Possible therapeutic applicability of galectin-9 in cutaneous T-cell lymphoma.

BACKGROUND: Galectin-9, a member of the galectin family, can promote tumor growth through inducing apoptosis in anti-tumor immune cells via T cell immunoglobulin and mucin domain 3 (TIM-3). On the other hand, galectin-9 also induces tumor cell apoptosis in many malignancies and thought to have potential as an anti-cancer agent. OBJECTIVE: To examine the expression and therapeutic applicability of galectin-9 in cutaneous T-cell lymphoma (CTCL). METHODS: Galectin-9 expression in lesional skin and sera was measured using CTCL samples. The effect of galectin-9 on CTCL cell lines was investigated in vitro. We also examined effect of galectin-9 on tumor growth of CTCL cells in immune-deficient mice. Moreover, we examined the efficacy of galectin-9, anti-TIM-3 blocking antibody, or their combination on tumor growth of EL-4 cells in wild-type mice. RESULTS: Galectin-9 was expressed on tumor cells in lesional skin of CTCL and the expression levels were associated with decreased CD8+ T-cell infiltration. Serum galectin-9 levels were correlated with disease severity markers. High-dose galectin-9 induced cell death of CTCL cell lines through activation of caspase-3 and caspase-9, independently of TIM-3. High-dose galectin-9 suppressed the growth of CTCL cells and EL-4 cells in vivo. Furthermore, additional anti-TIM-3 blocking antibody administration to galectin-9 achieved greater inhibition of tumor growth compared to single administration. CONCLUSION: Galectin-9 expression on tumor cells may be associated with CTCL progression through attenuating anti-tumor immunity. On the other hand, exogenous high-dose galectin-9 administration can be a therapeutic strategy for CTCL and anti-TIM-3 blocking antibody can augment the efficacy of galectin-9.

Two distinct variants of mycosis fungoides (MF): Folliculotropic MF and erythrodermic MF.

Mycosis fungoides (MF) is the most frequent type of cutaneous T-cell lymphoma. Folliculotropic MF (fMF) and erythrodermic MF (eMF) are two distinct variants of MF. Both variants have been considered aggressive and most cases are less responsive to standard skin-directed therapies than classical MF. We, however, experienced many cases with fMF or eMF who showed indolent clinical courses. In this article, we reviewed 10 cases with fMF and 13 cases with eMF who came to our department between 2005 and 2017. In patients with fMF, monotherapy with topical corticosteroid was effective in two cases (20%) and ultraviolet phototherapy with oral retinoid controlled disease activity in two cases (20%). Five patients with eMF (38%) responded well to ultraviolet phototherapy. In conclusion, patients with early fMF and a subgroup of eMF patients have an indolent disease course, as was proposed among the specialists. Skin-directed therapies are preferable rather than aggressive treatment in those cases.

Expression of CCR3 and CCR4 Suggests a Poor Prognosis in Mycosis Fungoides and Sézary Syndrome.

Tumor cells in cutaneous T-cell lymphoma express limited numbers of chemokine receptors. We investigated the expression patterns of CXCR3, CCR3, CCR4 and CCR10 in mycosis fungoides, Sézary syndrome, lym-phomatoid papulosis and anaplastic large cell lymphoma in 121 skin biopsy samples. CXCR3 was expressed in 86% of mycosis fungoides cases but in no anaplastic large cell lymphoma cases. CCR3 was expressed in 73% of cases of CD30+ lymphoproliferative disorders such as lymphomatoid papulosis and anaplastic large cell lymphoma. Mycosis fungoides/Sézary syndrome patients with high CCR3 or CCR4 expression had a poorer survival prognosis than mycosis fungoides/Sézary syndrome patients whose tumor cells did not express these receptors. CCR10 was expressed in 50% of mycosis fungoides/Sézary syndrome cases and in 13% of cases with CD30+ lym-phoproliferative disorders. These results suggest that differential patterns of CXCR3, CCR3, CCR4 and CCR10 expression are useful for the diagnosis of cutaneous T-cell lymphoma. Moreover, expression of CCR3 or CCR4 suggests a poor prognosis in mycosis fungoides/Sézary syndrome.

Sézary syndrome without erythroderma: A case report and review of published work.

Sézary syndrome (SS) is defined by erythroderma and circulating atypical T cells, with or without lymphadenopathy. Recently, Thompson et al. identified a distinct population of SS patients with an atypical presentation: a high blood tumor burden of Sézary cells fulfilling criteria for SS but without fulfilling the criteria for erythroderma at the diagnosis. Here, we report a case of a 49-year-old Japanese man with SS who did not present with erythroderma initially, but exhibited erythematous itchy papules symmetrically located on the legs and arms. We also reviewed reported cases of SS without initial erythroderma. The skin manifestations at diagnosis varied from patches to tumors often seen in mycosis fungoides, and other rarer findings such as excoriation, palmoplantar keratoderma and alopecia. Pruritus was reported in most patients (86%), unlike early mycosis fungoides, and could be the main clue to the diagnosis of SS. Notably, three patients were reported to have presented with papular lesions, similar to our case. Little is known about why skin lesions in SS without erythroderma vary and why these cases did not exhibit erythroderma initially. Attenuated stimulation by colonized Staphylococcus aureus, impairment in recruitment of malignant T cells and suppression of inflammatory response induced by malignant T cells with regulatory phenotype may be associated with skin manifestations. Further studies are necessary to elucidate the etiology of this entity.

Decreased progranulin expression in Mycosis fungoides: a possible association with the high frequency of skin infections.

Progranulin (PGRN) is a multi-functional protein known to be involved in diverse biological processes, including tumourigenesis, anti-inflammation, and anti-infection. PGRN expression in sera or tissues is elevated in a variety of malignancies and is associated with poor prognosis. However, it remains to be determined whether PGRN is involved in Mycosis fungoides (MF). To investigate the roles of PGRN in MF. Serum PGRN levels were measured in patients with MF and normal controls by enzyme-linked immunosorbent assay. PGRN expression in MF and normal skin was examined by quantitative reverse transcription polymerase chain reaction and immunohistochemistry. Moreover, we analysed correlations between the expression levels of PGRN and antimicrobial peptides in lesional skin. PGRN levels were significantly lower in sera of MF patients than those of normal controls. PGRN mRNA levels in lesional skin of MF were also significantly decreased. Immunohistochemical staining revealed that PGRN was expressed in epidermal keratinocytes of normal controls, however, PGRN expression in epidermal keratinocytes was also weaker in MF skin. Furthermore, significant inverse correlations were identified between PGRN and antimicrobial peptide mRNA expression. These results suggest that low PGRN expression may contribute to the frequent occurrence of skin infections in patients with MF.

Increased HMGB1 levels in lesional skin and sera in patients with cutaneous T-cell lymphoma.

BACKGROUND: High mobility group box-1 (HMGB1) is a ubiquitously expressed non-histone nuclear protein which acts as a danger signal when released from cells. HMGB1, which is associated with inflammation, angiogenesis, and T helper (Th)2 polarization, contributes to the development of various inflammatory diseases and malignancies. However, it remains to be determined whether HMGB1 is involved in cutaneous T-cell lymphoma (CTCL). OBJECTIVES: To investigate the role of HMGB1 in CTCL. MATERIALS & METHODS: Serum HMGB1 levels were measured in patients with CTCL and healthy controls using an enzyme-linked immunosorbent assay. HMGB1 messenger RNA (mRNA) expression in CTCL and normal skin was examined by quantitative reverse transcription polymerase chain reaction and immunohistochemistry. Moreover, we analysed correlations between the levels of HMGB1 and other cytokines and chemokines, laboratory data, disease activity, and prognosis. RESULTS: HMGB1 levels were significantly higher in sera of CTCL patients than those of normal controls and correlated with serum levels of soluble interleukin-2 receptor, lactate dehydrogenase, thymus and activation-regulated chemokine, and the number of eosinophils in peripheral blood. Serum HMGB1 levels also reflected disease activity and prognosis for each patient with CTCL. HMGB1 mRNA levels in CTCL lesional skin were significantly elevated and correlated with IL-4, IL-10, IL-19, and angiogenin mRNA levels. Immunohistochemical staining revealed that HMGB1 was expressed not only in the nucleus but also in the cytoplasm of various cells in CTCL lesional skin. CONCLUSION: These results suggest that enhanced HMGB1 expression may contribute to the progression of CTCL through Th2 polarization and promotion of angiogenesis.

Aberrant CD137 ligand expression induced by GATA6 overexpression promotes tumor progression in cutaneous T-cell lymphoma.

CD137 and its ligand, CD137L, are expressed on activated T cells and antigen-presenting cells, respectively. Recent studies have shown that CD137L and CD137 are aberrantly expressed by tumor cells, especially in some hematopoietic malignancies, and interactions between these molecules on tumor cells promote tumor growth. In this study, we investigated the roles of CD137L and CD137 in cutaneous T-cell lymphoma (CTCL), represented by mycosis fungoides and Sézary syndrome. Flow cytometric analysis showed that primary Sézary cells and CTCL cell lines (Hut78, MyLa, HH, SeAx, and MJ) aberrantly expressed CD137L. CD137L expression by tumor cells in CTCL was also confirmed by immunohistochemistry. Anti-CD137L-neutralizing antibody inhibited proliferation, survival, CXCR4-mediated migration, and in vivo growth in CTCL cell lines through inhibition of phosphorylation of AKT, extracellular signal-regulated kinase 1/2, p38 MAPK, and JNK. Moreover, suppression of CD137L signaling decreased antiapoptotic proteins Bcl-2 and phosphorylated Bad. We also explored the transcription factor regulating CD137L expression. Because GATA6 has been proposed as an oncogene in many types of tumors with aberrant CD137L expression, we examined GATA6 expression and the involvement of GATA6 in CD137L expression in CTCL. DNA hypomethylation and histone acetylation induced GATA6 overexpression in CTCL cells. Furthermore, chromatin immunoprecipitation, luciferase reporter assay, and knockdown by short hairpin RNA showed that GATA6 directly upregulated CD137L expression. Inhibition of GATA6 resulted in decreased survival and in vivo growth in CTCL cells. Collectively, our findings prompt a novel therapeutic approach to CTCL based on the discovery that the GATA6/CD137L axis plays an important role in the tumorigenesis of CTCL.

Decreased IL-10-producing regulatory B cells in patients with advanced mycosis fungoides.

BACKGROUND: Historically, B cells have been considered as positive regulators of humoral immune responses. Specific B-cell subsets, however, negatively regulate immune responses and are termed "regulatory B cells" (Bregs). Recently, Bregs have been linked to not only inflammatory and autoimmune diseases, but also malignancies via suppressing anti-tumour immunity. OBJECTIVES: To investigate the involvement of Bregs in advanced mycosis fungoides (MF). MATERIALS & METHODS: The frequency of CD19+CD24hiCD27+ memory B cells and CD19+CD24hiCD38hi transitional B cells (which enrich IL-10-producing Bregs) was examined in peripheral blood from patients with advanced MF (n = 11) and healthy controls (n = 9) by flow cytometry. The frequency of IL-10-producing Bregs was also measured by flow cytometry. The correlation between frequency or number of B-cell subsets and disease severity markers was also analysed. RESULTS: The frequency of CD19+CD24hiCD27+ B cells, CD19+CD24hiCD38hi B cells, and IL-10-producing B cells was decreased in peripheral blood of advanced MF patients. The frequency and number of these B-cell subsets inversely correlated with serum soluble IL-2 receptor and serum lactate dehydrogenase levels. CONCLUSIONS: The development of IL-10-producing Bregs is impaired in patients with advanced MF and a decrease in IL-10-producing Bregs may play an important role in the progression of advanced MF.