SU‐F‐T‐59: The Effect of Radiotherapy Dose On Immunoadjuvants

Abstract

Purpose:Combining radiotherapy with immunotherapy is a promising approach to enhance treatment outcomes for cancer patients. This in‐vitro study investigated which radiotherapy doses could adversely affect the function of anti‐CD40 mAb, which is one of the key immunoadjuvants under investigations for priming such combination therapy.Methods:Human monocyte derived THP‐1 cells were treated with 100ng/mL of PMA in chamber slides to differentiate into macrophage. The THP‐1 differentiated macrophages were treated with 2uL/ml of the anti‐CD40 mAb and incubated at 37°C and 5% CO2 for 24 hours. Anti‐CD40 mAb treated cells were then irradiated at different doses of x‐rays: (0, 2, 4, 6, 8, and 12) Gy using the Small Animal Radiotherapy Research Platform (SARRP). After radiation, the cells were left at 4°C for 2 hours followed by immunofluorescence assay. A Nikon inverted live‐cell imaging system with fluorescence microscope was used to image the cells mounted on a slide fixed with Dapi. For comparison, an ELISA assay was performed with the antibody added to 3mL of PBS in multiple 10mm dishes. The 10mm dishes were irradiated at different x‐ray dose: (0, 2, 4, 6, 8. 10, 12, and 15) Gy using the SARRP.Results:The anti‐CD40 mAb activating the macrophages starts to lose their viability due to radiation dose between 8Gy to 12Gy as indicated by the immunofluorescence assay. The ELISA assay, also indicated that such high doses could lead to loss of the mAb's viability.Conclusion:This work suggests that high doses like those employed during Stereotactic Ablative Radiotherapy may affect the viability of immunoadjuvants such as anti‐CD 40. This study avails in‐vivo experiments combining radiotherapy with anti‐cd40 to get synergistic outcomes, including in the treatment of metastatic disease.