Melanoma is the main cause of death in
skin cancers. Despite combating with early detection, resection and post-operative
therapy,
melanoma treatment remains unsuccessful and investigations into other forms of adjuvant
therapy such as
photodynamic therapy (
PDT) are prudent. This study proposes that depigmentation i.e. the removal of the
free radical scavenging pigment,
melanin, in melanotic
melanoma cells increases their susceptibility to
PDT-induced cell death. Two human
melanoma cell lines: one pigmented (Mel-1) and one amelanotic (A(375)) cell lines were used.
Kojic acid (KA), a
tyrosinase-specific inhibitor, was optimised to 6 μg/ml and shown to quantifiably inhibit
melanin synthesis after a 3-day exposure.
PDT on these cells resulted in a 3.82 fold increase of intracellular ROS production which correlated to 11% increase in cell death susceptibility compared to untreated controls. Moreover, cells allowed to regain their pigment failed to return to normal even after 72 h thus proving the effectiveness of
PDT. Using a DPPH* assay, the results confirmed the scavenging properties of
melanin (IC(50) 18.30 μg/ml) proving that this pigment may be one of the reasons for
melanoma chemoresistance. Overall this study shows that pigment plays an important role in the efficacy of adjunctive
PDT treatment and its removal enhances cell death susceptibility in
melanomas.