Thymoquinone enhances the effect of Gamma Knife in B16-F10 melanoma through inhibition of p-STAT3. - GreenMedInfo Summary

BACKGROUND: Patients with brain metastasis from melanoma have dismal prognosis with poor survival time. Gamma Knife (GK) is an effective treatment to control brain metastasis from melanoma. Thymoquinone (TQ) has emerged as a potential therapeutic option due to its anti-proliferative effects on various cancers. The purpose of the study was to assess the effect of Gamma Knife (GK) in B16-F10 melanoma cells in vitro and intracerebral melanoma in vivo, and its synergistic effect in combination with TQ.

METHODS: Effects of GK and combination treatment of GK and TQ were studied on B16-F10 melanoma cells with evaluating cytotoxicty by adenosine triphosphate (ATP) assay; apoptosis by acridine orange staining and genotoxicity by comet assay. Western blot analysis was performed to investigate the expressions of STAT3, p-STAT3 (Tyr705), JAK2, p-JAK2, caspase-3, Bax, Bcl-2, survivin andβ-actin. Expression of inflammatory cytokines was assessed by Enzyme Linked Immunosorbent Assay (ELISA). Also GK and its combination treatment with TQ were assessed in an established intracerebral melanoma tumor in mice.

RESULTS: The effects of GK on cytotoxicity, genotxicity and apoptosis were enhanced by TQ on B16-F10 melanoma cells. GK induced apoptosis through inhibition of p-STAT3 expression, which in turn regulated pro- and anti-apoptotic proteins such as caspase-3, Bax, Bcl-2, survivin. Adding TQ to GK irradiation further enhanced this apoptotic effect of GK irradiation. GK was shown to reduce the levels of tumor-related inflammatory cytokines on B16-F10 melanoma cells. This effect was more pronounced when TQ was added to GK irradiation. GK with 15 Gy increased the survival of mice with intracerebral melanoma compared to untreated mice. However, despite the additive effect of TQ in addition to GK irradiation on B16-F10 melanoma cells in vitro, TQ did not add any significant survival benefit to GK treatment in mice with intracerebral melanoma.

CONCLUSION: Our findings suggest that TQ would be a potential therapeutic agent in addition to GK to enhance the anti-tumor effect of irradiation. Further studies are required to support our findings.