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Cancer Cell death Cell cycle Cytoskeleton Exo/endocytosis Differentiation Division Organelles Signalling Stem cells Trafficking
Cell Biology International (2009) 33, 1065–1072 (Printed in Great Britain)
Melanomas display increased cytoprotection to hypericin-mediated cytotoxicity through the induction of autophagy
Lester M. Davids*, Britta Kleemann, Susan Cooper and Susan H. Kidson
Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, 7925 Cape Town, South Africa


Photodynamic therapy (PDT) as a regime for melanoma is of limited success due to factors such as the efficacy of the photosensitizer used, penetration depth and the presence of pigment. We characterised a pigmented and an unpigmented melanoma cell line with respect to their phenotypes. Cell viability was assessed after exposure to hypericin, a UVA-activated photosensitizer. Exposure to 3μM activated hypericin induced a cytoprotective (autophagic) response from both cell lines. However, the pigmented cells accumulated a large amount of glycogen in their cytoplasm. We hypothesise that the treatment induces an initial cytoprotective response through autophagy, but with increased stress results in a different mode of cell death in pigmented melanoma cells from unpigmented cells. These results indicate that hypericin-PDT could be an adjuvant therapy for melanoma.

Key words: Hypericin, Photodynamic therapy, Melanoma, Autophagy, Apoptosis.

*Corresponding author. Tel.: +27 21 406 6787; fax: +27 21 448 7226.

Received 5 December 2008/22 May 2009; accepted 27 June 2009


ISSN Print: 1065-6995
ISSN Electronic: 1095-8355
Published by Portland Press Limited on behalf of the International Federation for Cell Biology (IFCB)