Silkworm-pheophorbide a mediated photodynamic therapy against B16F10 pigmented melanoma

Abstract

In order to apply photodynamic therapy (PDT) to pigmented melanoma, the efficacy of PDT mediated by pheophorbide a from silkworm excreta (SPb a) and commercial Photofrin ® against B16F10 melanoma was comparatively studied from the in vivo assay using C57BL/6J mice. From in vitro PDT assay, the proliferation of B16F10 cells treated with SPb a (more than 0.5 μg/ml) and light illumination (1.2 J/cm 2) were significantly inhibited with the necrotic response. This indicated that the photocytotoxicity of SPb a (665 nm) was not influenced by melanin from melanoma. From the assessment of the in vivo photosensitizing activity, the tumor growth was further delayed in groups treated with SPb a/PDT compared to that treated with Photofrin ®/PDT. The survival rate of tumor bearing mice treated with SPb a/PDT was closely associated with its photosensitizing effect. In addition, the photosensitizing effect of SPb a/PDT showed a dose dependent tendency in light illumination. These results demonstrated that B16F10 melanoma cells were significantly photosensitized by SPb a/PDT, regardless of the influence of melanin from melanoma, and SPb a/PDT at very low drug dose (1 mg/kg) and light dose (1.2 J/cm 2) showed the photosensitizing efficacy surpassing Photofrin ® against B16F10 melanoma in mice system.