Methylene blue photodynamic therapy in malignant melanoma decreases expression of proliferating cell nuclear antigen and heparanases

BACKGROUND: Malignant melanoma (MM) is a very aggressive tumour. Although surgical excision of MM in the early stages has a very good prognosis, it often fails to completely inhibit tumour progression. Methylene blue photodynamic therapy (MB-PDT) is a technique that induces tissue damage by reactive oxygen species (ROS). AIM: To investigate the efficacy of and potential use of MB-PDT in restraining the aggressiveness of MM by analysing levels of proliferating cell nuclear antigen (PCNA) and heparanase (HPSE, a molecular marker of cell invasion) in a mouse model. METHODS: Expression of PCNA and two HPSE isoforms were analysed using immunohistochemistry (IHC) after MB-PDT in mice. Tumour volume and weight were also measured. RESULTS: Two treatments with MB-PDT promoted a decrease of 99% decrease in tumour volume and 75% in tumour weight compared with untreated mice (P < 0.05). Using IHC, a decrease in expression of 75% for PCNA and 95% for both HPSE isoforms (P < 0.05) was found. CONCLUSION: MB-PDT is a cheap and efficient method of decreasing MM volume and thus disease progression. This reduction is mediated by downregulation of PCNA and heparanases.