Supranuclear Melanin Caps Reduce Ultraviolet Induced DNA Photoproducts in Human Epidermis

Melanin can form supranuclear caps in human epidermis, suggesting that intracellular melanin reduces ultraviolet transmission to underlying cell nuclei and inhibits the formation of ultraviolet induced DNA photoproducts. The purpose of this study was to determine the photoprotective effect of epidermal melanin. We irradiated normal human skin explants with ultraviolet B and determined the formation of cyclobutane pyrimidine dimers and (6–4)photoproducts in individual epidermal cells by indirect immunofluorescence and by laser cytometry using monoclonal antibodies specific for cyclobutane dimers or for (6–4)photoproducts. We found that epidermal cells with supranuclear melanin caps had significantly less DNA photoproducts (both types) than epidermal cells without supranuclear melanin caps. Moreover, the protection factor against both types of photolesions correlated with melanin concentration in epidermal cells. These results indicate that melanin reduces ultraviolet induced DNA photoproducts in human epidermis in a concentration dependent manner

An emerging strategy for cancer treatment targeting aberrant glycogen synthase kinase 3β

金沢大学がん研究所分子標的がん医療研究開発センターImprovement in the outcome of cancer patients who are refractory to currently available treatments relies on the development of target-directed therapies. One group of molecular targets with potential clinical relevance is a set of protein tyrosine kinases encoded mostly by proto-oncogenes and that are frequently deregulated in cancer. Glycogen synthase kinase 3β (GSK3β), a serine/threonine protein kinase, has emerged as a therapeutic target for common chronic diseases including type 2 diabetes mellitus, neurodegenerative disorders, inflammation and osteoporosis. This is based on its currently known functions and primary pathologic causalities. GSK3β has well characterized roles in the regulation of gene transcription and in oncogenic signaling. We have shown that deregulated GSK3β promotes gastrointestinal, pancreatic and liver cancers and glioblastomas. Furthermore, we have demonstrated that inhibition of GSK3β attenuates cancer cells survival and proliferation, induces cell senescence and apoptosis and sensitizes tumor cells to chemotherapeutic agents and ionizing radiation. This has led us to propose GSK3β as a potential therapeutic target in cancer. The anti-tumor effects of GSK3β inhibition are mediated by changes in the expression and phosphorylation of molecules critical to the regulation of cell cycling, proliferation and apoptosis and underlie the pathological role for GSK3β in cancer. Investigation of the mechanisms responsible for deregulation of GSK3β and the consequent downstream pathologic effects in cancer cells has shed light on the molecular pathways leading to tumorigenesis. This will allow exploration of novel therapeutic strategies for cancer that target aberrant GSK3β. © 2009 Bentham Science Publishers Ltd