Abstract A026: Administration of preoperative ketorolac prevents osteosarcoma recurrence by promoting T cell memory and inhibiting immunosuppression
Authors: Pankove Rebecca , Ganesan Ramya , Bhasin Swati S , Michaud Marina , Bhasin Manoj , Sukhatme Vikas P 
Published: December 2023

Abstract
Introduction: Surgery induces an inflammatory response that is important for wound healing, but can also promote the survival of cancer cells and future tumor recurrence. Surgical injury activates the cyclooxygenase pathway and the production of downstream mediators such as prostaglandin E2 (PGE2) which has tumor-promoting and immunosuppressive activity. PGE2 stimulates regulatory T cells (Tregs), inhibits antigen presentation, and suppresses natural killer cells. Using a murine model of metastatic osteosarcoma, we investigated if preoperative blockade of this inflammatory cascade with ketorolac, a nonsteroidal anti-inflammatory drug, can boost anticancer T cell immunity. We also assessed if ketorolac had a synergistic effect when administered with a Programmed cell death protein-1 (PD-1) inhibitor.
Methods: C3H/HeJ mice were inoculated with LM8 metastatic osteosarcoma cells. Tumors were resected at 50-150 mm3 and 2 hours before surgery, mice received an intraperitoneal injection containing either PBS, ketorolac, or ketorolac and antibodies to PD-1. All mice who survived beyond 100 days were considered long-term survivors and rechallenged with LM8 cells to evaluate immunological memory. Peripheral blood and spleen were collected and processed to perform flow cytometric analysis and single-cell sequencing of immune cell populations.
Results: Following resection of primary tumors, 24 out of 25 control mice succumbed to lung metastasis by day 36 after resection while 4 out of 25 mice administered preoperative ketorolac exhibited long-term survival (defined as &gt;90 days after tumor resection). All long-term survivors who received preoperative ketorolac were resistant to a rechallenge with LM8 cells. There was no difference in survival between mice who did and did not receive PD-1 inhibition. Flow cytometry analysis showed that the ketorolac-treated mice had increased T cell activity with a higher percent of effector and effector memory CD4+ and CD8+ T cells. In addition, a lower percent of myeloid derived suppressor cells (MDSCs) and Tregs were found in the spleens of mice treated with preoperative ketorolac. Single cell sequencing revealed that ketorolac-treated mice exhibited an expansion in B cells, specifically follicular B cells that expressed genes related to antigen presentation and cell proliferation.
Conclusions: Administration of preoperative ketorolac in mice with osteosarcoma resulted in long-term survival after tumor resection and prevention of tumor recurrence after secondary challenge. Further, treatment with ketorolac reduced two cell populations of immunosuppressive significance, while enhancing immune cell memory. Thus, targeting surgery-induced inflammation with preoperative ketorolac should be further explored as a strategy to bolster a tumor-specific, T cell mediated immune response.
Citation Format: Rebecca Pankove, Ramya Ganesan, Swati S Bhasin, Marina Michaud, Manoj Bhasin, Vikas P Sukhatme. Administration of preoperative ketorolac prevents osteosarcoma recurrence by promoting T cell memory and inhibiting immunosuppression [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A026.