Hailey-Hailey disease (HHD, MIM 16960) is inherited in an autosomal dominant manner and characterized by persistent blisters and erosions of the skin. Impaired intercellular adhesion and epidermal blistering also occur in individuals with pemphigus (which is due to autoantibodies directed against desmosomal proteins) and in patients with Darier disease (DD, MIM 124200), which is caused by mutations in a gene encoding a sarco/endoplasmic reticulum (ER)-Golgi calcium pump. We report here the identification of mutations in ATP2C1, encoding the human homologue of an ATP-powered pump that sequesters calcium into the Golgi in yeast, in 21 HHD kindreds. Regulation of cytoplasmic calcium is impaired in cultured keratinocytes from HHD patients, and the normal epidermal calcium gradient is attenuated in vivo in HHD patients. Our findings not only provide an understanding of the molecular basis of HHD, but also underscore the importance of calcium control to the functioning of stratified squamous epithelia.

Inflammatory stimuli result in the production of cutaneous eicosanoids, which are known to contribute to the process of tumor promotion. Cyclooxygenase (COX), the rate-limiting enzyme for the production of prostaglandins (PG) from arachidonic acid, exists in at least two isoforms, COX-1 and COX-2. COX-1 is constitutively expressed in most tissues and plays various physiological roles, whereas increased COX-2 expression is known to occur in several types of epithelial neoplasms. Enhanced PG synthesis is a potential contributing factor in UVBinduced nonmelanoma skin cancers (NMSC). Increased COX-2 staining occurs in murine skin neoplasms after chronic exposure to carcinogenic doses of UVB. In this study, immunohistochemical and Western blot analyses were employed to assess longitudinally COX-2 expression in a standard mouse UVB complete carcinogenesis protocol and in human basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). During UVB irradiation of mice, COX-2 expression consistently increased in the hyperplastic skin, the benign papillomas and the SCC. COX-2 expression was also increased in human actinic keratoses, SCC and BCC as well as in murine SCC and BCC. The pattern of COX-2 expression was quite variable, occurring in a patchy distribution in some lesions with staining confined mainly to suprabasal cell layers. In general, COX-2 expression progressively became more extensive in benign papillomas and well-differentiated murine SCC. The staining was predominantly cy- ¶Posted on the website on 3 May 2002. tea polyphenols; IRB, institutional review board; MED, minimum erythema dose; MOM, mouse-on-mouse; NMSC, nonmelanoma skin cancers; NSAID, nonsteroidal anti-inflammatory drugs; OCT, optimum cutting temperature compound; PG, prostaglandin; PKC, protein kinase C; SCC, squamous cell carcinoma; TPA, 12-Otetradecanoyl 13-phorbol acetate.toplasmic and perinuclear in some focal areas in tissue stroma around both murine and human tumors. Western blot analysis confirmed negative COX-2 expression in normal skin, whereas acute UVB exposure resulted in increased enzyme expression, which continued to increase in developing papillomas and SCC. Because of the evidence indicating a pathogenic role for eicosanoids in murine and human skin neoplasms, we performed studies to assess the anti-inflammatory and anticarcinogenic effects of green tea extracts, which are potent antioxidants. Acute exposure of the human skin to UVB (minimum erythema dose ؋ 4) caused a transient enhancement of the COX-2 expression, which reverted to baseline within hours; however, in murine skin the expression persisted for several days. Pretreatment with the topically applied green tea extract (1 mg/cm 2 ) largely abrogated the acute COX-2 response to UVB in mice or humans. In summary, enhanced COX-2 expression serves as a marker of epidermal UVB exposure for murine and human NMSC. These results suggest that COX-2 inhibitors could have potent anticarcinogenic effects in UVBinduced skin cancer.

Inflammatory stimuli result in the production of cutaneous eicosanoids, which are known to contribute to the process of tumor promotion. Cyclooxygenase (COX), the rate‐limiting enzyme for the production of prostaglandins (PG) from arachidonic acid, exists in at least two isoforms, COX‐1 and COX‐2. COX‐1 is constitutively expressed in most tissues and plays various physiological roles, whereas increased COX‐2 expression is known to occur in several types of epithelial neoplasms. Enhanced PG synthesis is a potential contributing factor in UVB‐induced nonmelanoma skin cancers (NMSC). Increased COX‐2 staining occurs in murine skin neoplasms after chronic exposure to carcinogenic doses of UVB. In this study, immunohistochemical and Western blot analyses were employed to assess longitudinally COX‐2 expression in a standard mouse UVB complete carcinogenesis protocol and in human basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). During UVB irradiation of mice, COX‐2 expression consistently increased in the hyperplastic skin, the benign papillomas and the SCC. COX‐2 expression was also increased in human actinic keratoses, SCC and BCC as well as in murine SCC and BCC. The pattern of COX‐2 expression was quite variable, occurring in a patchy distribution in some lesions with staining confined mainly to suprabasal cell layers. In general, COX‐2 expression progressively became more extensive in benign papillomas and well‐differentiated murine SCC. The staining was predominantly cytoplasmic and perinuclear in some focal areas in tissue stroma around both murine and human tumors. Western blot analysis confirmed negative COX‐2 expression in normal skin, whereas acute UVB exposure resulted in increased enzyme expression, which continued to increase in developing papillomas and SCC. Because of the evidence indicating a pathogenic role for eicosanoids in murine and human skin neoplasms, we performed studies to assess the anti‐inflammatory and anticarcinogenic effects of green tea extracts, which are potent antioxidants. Acute exposure of the human skin to UVB (minimum erythema dose × 4) caused a transient enhancement of the COX‐2 expression, which reverted to baseline within hours; however, in murine skin the expression persisted for several days. Pretreatment with the topically applied green tea extract (1 mg/cm2) largely abrogated the acute COX‐2 response to UVB in mice or humans. In summary, enhanced COX‐2 expression serves as a marker of epidermal UVB exposure for murine and human NMSC. These results suggest that COX‐2 inhibitors could have potent anticarcinogenic effects in UVB‐induced skin cancer.

The identification of mutations in Hedgehog (HH) pathway genes in some basal cell carcinomas (BCC) and the detection of HH pathway dysregulation in almost all BCC confirms the importance of this developmental regulatory pathway in human BCC tumorigenesis. Moreover, the occurrence of UVB signature mutations in key HH pathway genes in BCC provides the first genetic evidence that UV radiation (UVR) may be the principal mutagen involved in BCC tumorigenesis. We review herein current advances in the understanding of the role of the HH pathway in BCC tumorigenesis including transgenic and knock-out animal models of HH pathway dysregulation. Furthermore, we summarize abnormalities in other tumor suppressors and oncogenes including ras and p53 and evidence for interactions between these regulatory genes and the HH pathway.

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