Pediatric mycosis fungoides in Singapore: a series of 46 children.

Few studies have evaluated Asian children with mycosis fungoides (MF). We report a series of patients from a tertiary dermatologic institution in Singapore. A retrospective review was performed of patients younger than 16 years old diagnosed with MF between 2000 and 2008 at the National Skin Centre, Singapore. Forty-six patients were identified. At initial presentation, a provisional diagnosis of MF was made in 19 patients (41.3%), pityriasis lichenoides chronica (PLC) in 11 (23.9%) and postinflammatory hypopigmentation due to eczema or other causes in 11 (23.9%). After skin biopsy, the hypopigmented variant of MF was diagnosed in 42 patients (91.3%). There was one case each of PLC-like MF, pigmented purpuric dermatosis-like MF, classic MF, and solitary MF. Pityriasis lichenoides coexisted in three cases (6.5%). All except one patient presented with the early patch-plaque stage of disease (stage IA/B). The disease did not progress in any of our patients after a mean follow-up of 71.0 ± 52.5 months. Twenty-seven patients (58.7%) had complete disease clearance after a mean duration of 27.1 ± 28.1 months; 15 (49.7%) of 32 patients who received narrowband ultraviolet B treatment had complete clearance within an average of 8.9 ± 5.3 months, but 7 patients relapsed within 14.9 ± 14.8 months. One patient with solitary MF failed multiple treatment modalities before eventually achieving disease clearance with photodynamic therapy. Hypopigmented MF is the most common MF variant in Asian children. The diagnostic difficulty is in differentiating this from PLC, which may coexist with MF. Long-term prognosis is generally favorable.

Angiopoietin-like 4 interacts with integrins beta1 and beta5 to modulate keratinocyte migration.

Adipose tissue secretes adipocytokines for energy homeostasis, but recent evidence indicates that some adipocytokines also have a profound local impact on wound healing. Upon skin injury, keratinocytes use various signaling molecules to promote reepithelialization for efficient wound closure. In this study, we identify a novel function of adipocytokine angiopoietin-like 4 (ANGPTL4) in keratinocytes during wound healing through the control of both integrin-mediated signaling and internalization. Using two different in vivo models based on topical immuno-neutralization of ANGPTL4 as well as ablation of the ANGPTL4 gene, we show that ANGPTL4-deficient mice exhibit delayed wound reepithelialization with impaired keratinocyte migration. Human keratinocytes in which endogenous ANGPTL4 expression was suppressed by either siRNA or a neutralizing antibody show impaired migration associated with diminished integrin-mediated signaling. Importantly, we identify integrins ß1 and ß5, but not ß3, as novel binding partners of ANGPTL4. ANGPTL4-bound integrin ß1 activated the FAK-Src-PAK1 signaling pathway, which is important for cell migration. The findings presented herein reveal an unpredicted role of ANGPTL4 during wound healing and demonstrate how ANGPTL4 stimulates intracellular signaling mechanisms to coordinate cellular behavior. Our findings provide insight into a novel cell migration control mechanism and underscore the physiological importance of the modulation of integrin activity in cancer metastasis.

Angiopoietin-like 4 interacts with matrix proteins to modulate wound healing.

A dynamic cell-matrix interaction is crucial for a rapid cellular response to changes in the environment. Appropriate cell behavior in response to the changing wound environment is required for efficient wound closure. However, the way in which wound keratinocytes modify the wound environment to coordinate with such cellular responses remains less studied. We demonstrated that angiopoietin-like 4 (ANGPTL4) produced by wound keratinocytes coordinates cell-matrix communication. ANGPTL4 interacts with vitronectin and fibronectin in the wound bed, delaying their proteolytic degradation by metalloproteinases. This interaction does not interfere with integrin-matrix protein recognition and directly affects cell-matrix communication by altering the availability of intact matrix proteins. These interactions stimulate integrin- focal adhesion kinase, 14-3-3, and PKC-mediated signaling pathways essential for effective wound healing. The deficiency of ANGPTL4 in mice delays wound re-epithelialization. Further analysis revealed that cell migration was impaired in the ANGPTL4-deficient keratinocytes. Altogether, the findings provide molecular insight into a novel control of wound healing via ANGPTL4-dependent regulation of cell-matrix communication. Given the known role of ANGPTL4 in glucose and lipid homeostasis, it is a prime therapeutic candidate for the treatment of diabetic wounds. It also underscores the importance of cell-matrix communication during angiogenesis and cancer metastasis.

Regulation of cell proliferation and migration by TAK1 via transcriptional control of von Hippel-Lindau tumor suppressor.

Skin maintenance and healing after wounding requires complex epithelial-mesenchymal interactions purportedly mediated by growth factors and cytokines. We show here that, for wound healing, transforming growth factor-beta-activated kinase 1 (TAK1) in keratinocytes activates von Hippel-Lindau tumor suppressor expression, which in turn represses the expression of platelet-derived growth factor-B (PDGF-B), integrin beta1, and integrin beta5 via inhibition of the Sp1-mediated signaling pathway in the keratinocytes. The reduced production of PDGF-B leads to a paracrine-decreased expression of hepatocyte growth factor in the underlying fibroblasts. This TAK1 regulation of the double paracrine PDGF/hepatocyte growth factor signaling can regulate keratinocyte cell proliferation and is required for proper wound healing. Strikingly, TAK1 deficiency enhances cell migration. TAK1-deficient keratinocytes displayed lamellipodia formation with distinct microspike protrusion, associated with an elevated expression of integrins beta1 and beta5 and sustained activation of cdc42, Rac1, and RhoA. Our findings provide evidence for a novel homeostatic control of keratinocyte proliferation and migration mediated via TAK1 regulation of von Hippel-Lindau tumor suppressor. Dysfunctional regulation of TAK1 may contribute to the pathology of non-healing chronic inflammatory wounds and psoriasis.

Retrospective 5-year review of 131 patients with mycosis fungoides and Sézary syndrome seen at the National Skin Centre, Singapore.

A total of 131 new cases of mycosis fungoides and Sézary syndrome were diagnosed clinically and histopathologically at our centre over a 5-year period. There were 87 males and 44 females with a mean age of 36.3 years (range 3-87 years) and no racial predilection. Of the 62 patients (47.3%) with classical mycosis fungoides, the majority were male (male : female = 4.2:1). There was one patient with Sézary syndrome. Patients aged older than 50 years were more likely to present with a longer duration of symptoms and advanced disease. In contrast to classical mycosis fungoides, the 47 patients diagnosed with hypopigmented mycosis fungoides had early stage disease, were younger, and no gender predilection was noted. The mean duration of follow up was 19.7 months (range 0.2-54.8 months). Complete remission was achieved in 24.7% and 53.8% of patients followed up at 1 and 3 years, respectively, using skin-directed and systemic treatment modalities appropriate for the stage of disease. There were five patients with progressive disease and three patients with advanced disease who died from disease-related complications. The most significant prognostic factors for 1-year and 3-year outcomes were the patient's duration of symptoms and stage of disease at presentation.