Silkworm-pheophorbide a mediated photodynamic therapy against B16F10 pigmented melanoma

In order to apply photodynamic therapy (PDT) to pigmented melanoma, the efficacy of PDT mediated by pheophorbide a from silkworm excreta (SPba) 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 SPba (more than 0.5 μg/ml) and light illumination (1.2 J/cm2) were significantly inhibited with the necrotic response. This indicated that the photocytotoxicity of SPba (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 SPba/PDT compared to that treated with Photofrin®/PDT. The survival rate of tumor bearing mice treated with SPba/PDT was closely associated with its photosensitizing effect. In addition, the photosensitizing effect of SPba/PDT showed a dose dependent tendency in light illumination. These results demonstrated that B16F10 melanoma cells were significantly photosensitized by SPba/PDT, regardless of the influence of melanin from melanoma, and SPba/PDT at very low drug dose (1 mg/kg) and light dose (1.2 J/cm2) showed the photosensitizing efficacy surpassing Photofrin® against B16F10 melanoma in mice system.