Combination of Olaparib and radiotherapy potentially enhance antitumor immunity and tumor control in a subcutaneous OSCC mouse model

This study aimed to assess the antitumor efficacy and immunomodulatory effects of combining Olaparib with radiotherapy in a murine model of oral squamous cell carcinoma (OSCC). Male C57BL/6 mice bearing subcutaneous MOC2 tumors received vehicle, Olaparib, radiotherapy, or combination treatment. Tumor growth and immune changes were assessed by flow cytometry, RT-qPCR, and immunohistochemistry. Olaparib alone had limited effects on tumor growth, whereas radiotherapy delayed tumor progression. The combination treatment produced greater tumor suppression than either treatment alone. Total CD3 + , CD4 + , and CD8 + tumor-infiltrating T-cell numbers were not significantly altered. However, the combination treatment was associated with an increased frequency of IL-17-expressing CD4 + T cells in tumors and increased splenic expression of IL-17 and RORγt. Tumor IL-21 expression was also increased, whereas the number of CD206-positive cells was reduced following combination treatment. Olaparib combined with radiotherapy was associated with enhanced tumor control in the OSCC model. This improved antitumor effect was associated with changes in IL-17, RORγt, IL-21, and CD206. These findings suggest treatment-related immune modulation, although the functional roles of IL-17-expressing T cells and macrophage phenotype require further investigation.