Targeting CD70 using CAR NK cells to enhance NK cells cytolytic effect against osteosarcoma

Abstract Background: Cure rates for osteosarcoma (OS) have not improved in >30 years and no new effectivetherapies have been identified for metastatic disease. Natural killer (NK) cells have become an attractive tool for cancer immunotherapy. Efficay is improved by direct tumor targeting introducing a specific chimeric antigen receptor (CAR). Emerging knowledge suggests CD70 to be a viable candidate as expression is higher in lung metastases and it has been correlated with tumor escape from immune surveillance. Objective: To assess whether using CD70 CAR-NK cells we can enhance trafficking, homing and proliferation of NK cells and therefore therapeutic efficacy against OS. Methods: We analyzed the cBioportal database to verify CD70 expression in OS. Surface expression of CD70 on human OS cell lines and normal osteoblasts was determined by flow cytometry. CD70 CAR constructs were sequenced, verified and transduced into NK cells. CD70 CAR NK and control NK cells cytolytic activity against OS cells was evaluated by IncuCyte. In vitrocytokine release was measured upon CD70 CAR NK/NK cells exposure to OS cells (IsoPlexis). Results: Database analysis confirmed OS CD70 gene amplification. Flow cytometry showed variable expression of CD70 on OS cells and no expression on human osteoblasts. There was an increase in CD70 CAR NK percent lysis against OS cells at the highest effector:target ratios compared to control NK cells. We found a predominant release in the chemoattractive/stimulatory cytokines upon OS cells exposure to CD70 CAR NK cells. Conclusion: CD70 has immunotherapy potential against OS. CD70 CAR NK cells have increased cytolytic activity against OS cells in vitro. Cytolytic activity may be influenced by the release of specific cytokines.