Alteration of Surface Glycoproteins After Photodynamic Therapy.

BACKGROUND: Cell membranes have been identified as an important intracellular cancer treatment target, since the glycoconjugates present on the cell surface are involved in numerous cell functions. Photodynamic therapy (PDT) is a therapeutic modality employed in the treatment of tumors that uses visible light to activate a photosensitizer.

OBJECTIVE: This study analyzed the expression of surface carbohydrates after PDT with two different photosensitizers, 5-aminolevulinic acid (ALA) and Photosan-3.

METHODS: Mice were injected subcutaneously with 2 × 105 B16 cells. After 7-10 days, the presence of a tumor with a diameter of 3.6 mm was observed. Photosan-3® and 5-aminolevulinic acid-ALA were used in the PDT treatment. Control animals (not submitted to either laser treatment or photosensitizer injection) and treated animals were euthanized 15 days post-treatment. The tumors were irradiated with a red diode laser, λ = 655 nm, energy density of 10 J.cm-2 , and power density of 45 mW.cm-2 . After 2 weeks of treatment with PDT, the mice were euthanized, the tumors were collected, and the cell surfaces were labeled with lectins concanavalin A (ConA) and wheat germ agglutinin (WGA).

RESULTS: Fluorescence microscopy analysis of the cell surfaces with lectins ConA and WGA showed the presence of α-mannose and α-glucose.

CONCLUSIONS: The combined effects of either Photosan-3 or ALA and red laser light on melanoma suggest an inhibitory glycosylation action from PDT on the surface of B16-F10 cells.