Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0598934 (tumor growth)
 58,965 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Melanotic melanomas have a poor response to photodynamic therapy (PDT). The reason for this is that melanin absorbs light over the entire wavelength region used for PDT (400-750 nm). Photobleaching of melanin is an approach to overcome this obstacle. In the present work, reflectance spectroscopy was applied to study depigmentation of human and murine skin with different melanin contents, and effects induced by PDT with topical application of methyl 5-aminolevulinate (MAL) on B16F10 melanotic melanomas transplanted to nude mice. Depigmentation and inhibition of tumor growth after violet light (420 nm) exposure, red light (634 nm) exposure, and combinations of both were studied. Reflectance spectroscopy was suitable for evaluation of the pigmentation of both human and murine skin. Skin depigmentation leads to increase in reflectance. PDT with violet light bleached some of the melanin in the skin above the B16F10 melanomas, and possibly also in the upper part of the melanomas. This resulted in a larger growth inhibition of tumors first given PDT with violet light and then with red light compared to treatments using the reverse order of illumination, namely, red light before violet light. It is concluded that violet light PDT can bleach melanin in melanotic tumors and therefore increase their sensitivity to red light PDT. This finding indicates a new PDT modality that can be further developed for treatment of superficial melanotic melanomas and possibly other diseases where pigmentation is a problem.
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PMID:A new method for photodynamic therapy of melanotic melanoma -- effects of depigmentation with violet light photodynamic therapy. 1819 32

Skin depigmentation represents a well-established treatment for extensive vitiligo and may likewise be suited to prevent tumor recurrences and as a prophylactic treatment of familial melanoma, as common bleaching agents are cytotoxic to melanocytes. Effective melanoma prevention requires a bleaching agent-induced loss of exposed melanocytes supported by an immune response to distant pigment cells. Studies on human explant cultures treated with depigmenting agents such as 4-tertiary butyl phenol (4-TBP) or monobenzyl ether of hydroquinone (MBEH) showed a significant increase in the migration of Langerhans cells toward the dermis only upon treatment with MBEH, thus suggesting selective elicitation of an immune response. To assess the depigmenting potential of bleaching agents in vivo, 4-TBP and MBEH were topically applied to C57BL/6 wild type as well as k14-SCF transgenic, epidermally pigmented mice. MBEH-induced significant skin depigmentation in both strains was not observed upon treatment with 4-TBP. Cytokine expression patterns in skin treated with MBEH support activation of a Th1-mediated immune response corresponding to an influx of T cells and macrophages. Importantly, despite insensitivity of tumor cells to MBEH-induced cytotoxicity, significantly retarded tumor growth was observed in B16 challenged k14-SCF mice pretreated with MBEH, likely due to an abundance of cytotoxic T cells accompanied by an increased expression of Th1 and Th17 cytokines. These data support the use of MBEH as a prophylactic treatment for melanoma.
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PMID:Topical application of bleaching phenols; in-vivo studies and mechanism of action relevant to melanoma treatment. 2131 16