ESTRO 2024 - Abstract Book

S5372

Radiobiology - Tumour biology

ESTRO 2024

In vitro experiments: To evaluate the radiosensitizing effect of melittin, the H460 non-small cell lung cancer cell line was used. These cells were exposed to various radiation doses (0, 2, 4, 6, and 8 Gy) and two concentrations of melittin (1.0 and 2.0 μg/ml). Cell viability was measured after 24 hours and clonogenicity analysis was performed 10 days after treatment. Apoptosis was also analyzed using flow cytometry after H460 cells were treated with 8 Gy radiation and 2.0 μg/ml melittin. The levels of relevant proteins involved in double-strand break repair and cell death were assessed using Western blot analysis. In vivo Experiments: In the animal model, H460 cells were implanted into male BALB/C nude mice, and tumors were allowed to grow to a specific size. The mice were divided into four groups: a control group receiving PBS, a group receiving melittin alone, a group receiving radiation alone, and a combination group receiving both melittin and radiation. Melittin was administered intraperitoneally to the melittin alone and combination groups for three consecutive days, while the irradiation alone and combination groups received a total of 15 Gy of radiation over three days. Tumor growth was monitored, and tumor tissues were collected for immunohistochemical staining. In the in vitro experiments, melittin demonstrated minimal cytotoxicity against H460 cells at concentrations up to 2.0 μg/ml for 24 hours. However, prolonged incubation for 48 hours resulted in reduced cell viability at concentrations above 0.5 μg/ml. The combination of melittin and radiation showed a radiosensitizing effect, as cell viability decreased more significantly than with radiation alone. Co-treatment with melittin and radiation also induced higher levels of cell death in H460 cells compared to irradiation or melittin treatment alone. The combination of melittin and radiation resulted in decreased phosphorylation of DNA PKcs and ATM, proteins involved in DNA damage repair, and increased expression of γ-H2AX, a marker of DNA double strand breaks. These findings indicated that melittin enhances the impact of radiation on DNA damage and repair. Additionally, the combination treatment downregulated BCL-2 expression (an anti-apoptotic protein) and upregulated BAX and cleaved caspase-3 (pro-apoptotic markers), further confirming the induction of cell death through apoptosis. In the in vivo experiments, the combination of melittin and radiation significantly inhibited tumor growth in the mouse lung cancer model, whereas radiation or melittin alone did not show the same effect. Immunohistochemical examination of resected tumors in the combination treatment group revealed increased expression of pro-apoptotic proteins (BAX and cleaved caspase-3) and decreased expression of the anti-apoptotic protein BCL-2. Results:

Conclusion:

In conclusion, this study demonstrated that melittin, a component of bee venom, acts as a radiosensitizer in the context of non-small cell lung cancer. Melittin enhances the efficacy of radiation therapy by promoting radiation induced cell death and inhibiting DNA damage repair. These findings were consistent across both in vitro and in vivo experiments. The results suggest that melittin could serve as a promising adjuvant therapy to enhance the effectiveness of radiotherapy for NSCLC through the apoptotic pathway. This research sheds light on a potentially valuable approach to improve the outcomes for NSCLC patients, who face limited treatment options and poor survival rates.