DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-SIN1 association mediates ultraviolet B (UVB)-induced Akt Ser-473 phosphorylation and skin cell survival.

BACKGROUND: The exposure of skin keratinocytes to Ultraviolet (UV) irradiation leads to Akt phosphorylation at Ser-473, which is important for the carcinogenic effects of excessive sun exposure. The present study investigated the underlying mechanism of Akt Ser-473 phosphorylation by UVB radiation. RESULTS: We found that DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and mammalian target of rapamycin (mTOR) complex 2 (mTORC2) were both required for UVB-induced Akt Ser-473 phosphorylation in keratinocytes. Inhibition of DNA-PKcs activity via its inhibitor NU7026, a dominant-negative kinase-dead mutation, RNA interference (RNAi) or gene depletion led to the attenuation of UVB-induced Akt Ser-473 phosphorylation. Meanwhile, siRNA silencing or gene depletion of SIN1, a key component of mTORC2, abolished Akt Ser-473 phosphorylation by UVB. Significantly, we discovered that DNA-PKcs was associated with SIN1 in cytosol upon UVB radiation, and this complexation appeared required for Akt Ser-473 phosphorylation. Meanwhile, this DNA-PKcs-SIN1 complexation by UVB was dependent on epidermal growth factor receptor (EGFR) activation, and was disrupted by an EGFR inhibitor (AG1478) or by EGFR depletion. UVB-induced complexation between DNA-PKcs and mTORC2 components was also abolished by NU7026 and DNA-PKcs mutation. Finally, we found that both DNA-PKcs and SIN1 were associated with apoptosis resistance of UVB radiation, and inhibition of them by NU7026 or genetic depletion significantly enhanced UVB-induced cell death and apoptosis. CONCLUSION: Taken together, these results strongly suggest that DNA-PKcs-mTORC2 association is required for UVB-induced Akt Ser-473 phosphorylation and cell survival, and might be important for tumor cell transformation.

[Epithelioid hemangioma: a clinicopathologic analysis of 7 cases].

OBJECTIVE: To study the clinicopathologic features, diagnosis and differential diagnosis of epithelioid hemangioma. METHODS: The morphologic features of 7 cases of epithelioid hemangioma of skin, bone and venous vessels were studied. RESULTS: There were altogether 4 male and 3 female patients (median age = 34 years; age range from 14 to 54 years). The 3 skin cases presented as single or multiple erythematous to bluish nodules or papules, with or without itchiness. The 2 bone cases appeared as osteolytic expansile lesions on radiologic examination. The remaining 2 cases involved medium-sized venous structures and presented as small isolated nodules in soft tissue. Histologically, the lesions were characterized by the presence of exuberant endothelial proliferations with various degree of inflammatory reaction. The neoplastic endothelial cells were plump, eosinophilic and polygonal, forming vascular channels. Occasional solid sheet-like arrangement was demonstrated. Intracytoplasmic vacuoles were commonly identified, indicating formation of primary lumen. The surrounding stroma contained various number of eosinophils and lymphoplasmacytic cells. Immunohistochemical study showed that the tumor cells were positive for endothelial markers (CD31 and CD34) and negative for epithelial marker (cytokeratin). Follow-up information was available in 6 cases. The duration of follow-up ranged from 5 to 36 months (median = 14 months). There was no evidence of recurrence or distant metastasis. CONCLUSIONS: Epithelioid hemangioma is a rare benign curable lesion which can be multifocal, involving skin, soft tissue and bone. It needs to be distinguished from Kimura's disease and epithelioid hemangioendothelioma.

Perifosine sensitizes UVB-induced apoptosis in skin cells: new implication of skin cancer prevention?

We demonstrate here that a relative low dose of perifosine significantly enhanced UVB-induced apoptosis in skin cells (keratinocytes and fibroblasts), associated with a significant increase of reactive oxygen species (ROS) and ceramide production as well as multiple perturbations of diverse cell signaling pathways, shifting to a significant pro-apoptosis outcomes. Perifosine inhibited UVB-induced pro-survival Akt/mammalian target of rapamycin (mTOR) and ERK activation, while facilitating pro-apoptotic AMP-activated protein kinas (AMPK), c-Jun-NH(2)-kinase (JNK), and p53 activation; these signaling changes together promoted a striking increase in skin cell apoptosis and a significantly reduced amount of DNA damages. Our results suggest that perifosine may represent a novel skin cancer prevention strategy.

Increasing ceramides sensitizes genistein-induced melanoma cell apoptosis and growth inhibition.

The aim of the current study is to investigate the effect of ceramides on genistein-induced anti-melanoma effects in vitro. We found that exogenously added cell-permeable short-chain ceramides (C6) dramatically enhanced genistein-induced growth inhibition and apoptosis in cultured melanoma cells. Genistein treatment only induced a moderate intracellular ceramides accumulation in B16 melanoma cells. Two different agents including 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), a ceramide glucosylation inhibitor, and the sphingosine kinase-1 (SphK1) inhibitor II (SKI-II), a sphingosine (ceramides precursor) phosphorylation inhibitor, both facilitated genistein-induced ceramides accumulation and melanoma cell apoptosis. Co-administration of ceramide (C6) and genistein induced a significant Akt inhibition and c-jun-NH(2)-kinase (JNK) activation, caspase-3 cleavage and cytochrome c release. Caspase-3 inhibitor z-DVED-fmk, JNK inhibitor SP 600125, or to restore Akt activation by introducing a constitutively active form of Akt (CA-Akt) diminished ceramide (C6) and genistein co-administration-induced in vitro anti-melanoma effect. Our study suggests that increasing cellular level of ceramides may sensitize genistein-induced anti-melanoma effects.