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Photodynamic therapy‐induced killing is enhanced in depigmented metastatic melanoma cells
Author(s) -
Sharma Krishna V.,
Bowers Natalie,
Davids Lester M.
Publication year - 2011
Publication title -
cell biology international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.932
H-Index - 77
eISSN - 1095-8355
pISSN - 1065-6995
DOI - 10.1042/cbi20110103
Subject(s) - photodynamic therapy , melanoma , melanin , intracellular , cancer research , programmed cell death , melanocyte , hypericin , cell culture , reactive oxygen species , tyrosinase , viability assay , cell , medicine , chemistry , pharmacology , biology , apoptosis , enzyme , biochemistry , organic chemistry , genetics
The resistance of pigmented human melanomas over their unpigmented counterparts to a number of therapies has suggested that the presence of intracellular melanin plays a role in rendering these cells less susceptible to cell death, probably through the ability of this pigment to act as an intracellular antioxidant, thus neutralizing chemotherapeutic‐induced ROS (reactive oxygen species). PDT (photodynamic therapy) was recently suggested as an attractive, adjunctive therapy owing to its cellular specificity and limited side effects. In the present study, we propose that first depigmenting melanomas with a reversible TYR (tyrosinase) inhibitor such as PTU (phenylthiourea) increases their susceptibility to HYP‐PDT (hypericin‐mediated PDT). Pigmented [UCT Mel‐1 (University of Cape Town melanoma cell line 1)] and unpigmented (A375) melanomas were first characterized with respect to their TYR activities and melanin quantities and then treated with a TYR inhibitor for 48 h. Cell viability assays after treatment with 3 μM HYP‐PDT showed a significant increase in cell death in depigmented melanomas compared with untreated melanomas that returned to the level of untreated melanoma cells on removing the TYR inhibitor. The present study supports the hypothesis that combining the inhibition of melanogenesis with PDT should be explored as a valid therapeutic target for the management of advanced melanoma.