P11.55 Thymoquinone enhances the sensitivity of B16-F10 melanoma cell line to Gamma Knife radiosurgery

Abstract

Abstract BACKGROUND Melanoma patients with brain metastasis have poor prognosis. Gamma Knife radiosurgery (GKR) is an effective treatment to control brain metastasis from melanoma. Thymoquinone (TQ) has gained attention as a potential therapeutic option due to its anti-tumor effects on various cancers. The aim of the study was to invetsigate the effect of GKR in B16-F10 melanoma cells in vitro and in established intracerebral melanoma model in mice in vivo, and the sensitizing efficacy of TQ towards GKR. MATERIAL AND METHODS Effects of GKR and combination treatment of GKR and TQ were studied on B16-F10 melanoma cells via analyzing cytotoxicty by adenosine triphosphate (ATP) assay; apoptosis induction by acridine orange staining and genotoxicity by comet assay. Expression of STAT3, p-STAT3 (Tyr705) and apoptotic pathway proteins was investigated by western blot analysis. Enzyme Linked Immunosorbent Assay (ELISA) was performed to assess the expression of inflammatory cytokines. Also survival was evaluated in mice with brain tumor after GKR and its combination treatment with TQ. RESULTS The effects of GKR on cytotoxicity, apoptosis and genotxicity were significantly enhanced by TQ on B16-F10 melanoma cells. GKR induced apoptosis through inhibition of p-STAT3 expression, which subsequently regulated pro- and anti-apoptotic proteins such as caspase-3, Bax, Bcl-2, survivin. Combination TQ with GKR irradiation enhanced the apoptotic effect of GKR irradiation. Furthermore, GKR decreased the levels of tumor-related inflammatory cytokines on B16-F10 melanoma cells. This effect was more pronounced when TQ was added to GKR irradiation. GKR with 15 Gy improved the survival of mice with intracerebral melanoma compared to untreated mice. Although, the additive effect of TQ in combination with GKR irradiation on B16-F10 melanoma cells in vitro, TQ did not add any significant survival benefit to GKR treatment in mice with intracerebral melanoma. CONCLUSION Our findings indicate that TQ would be a potential therapeutic and sensitizing agent in addition to GKR to enhance the anti-tumor effect of irradiation. Further studies are required to support our findings.