Abstract 878: Anti-MICA/B antibody promote anti-tumor activity of cytokine expanded tumor infiltrated natural killer (TINK) cells from canine sort tissue sarcomas

Abstract Background: Presence of tumor infiltrating NK (TINK) cells linked to prognosis in many solid tumors, but their function is often constrained by the adverse tumor microenvironment. Although promising antileukemia activity has been shown, the exploitation of adoptive NK cell therapy for solid tumor is still limited and unsatisfactory. Tumor MIC (MHC I chain related molecule) modulates TME and contributes NK cell dysfunction, here we study the role of anti-MICA/B antibody in TINK’s function against sarcoma tumors. Because NK cells are prevalent in human Undifferentiated Pleomorphic Sarcomas (UPS), we sought the analogous canine soft tissue sarcomas (STS) as a readily available source to culture and perform intensive study on TINKs. Methods: Canine TINK cells were expanded form canine sarcoma tumor specimens with IL-2. Human NK cells were expanded from PBMC of healthy donor with K652 feeder cells. In vitro cytotoxic assay against sarcoma was monitored by Incucyte system. Canine or human sarcoma xenograft mouse models were used to evaluate therapy effect of adoptive transferred NK cells, with or without anti-MIC Ab combinatory therapy. Results: The percentage of CD5-NKp46+ and CD5dimCD8+NKp46+ NK cell within tumor infiltrating CD45 cells in canine STS is significantly higher compared with osteosarcoma and other types of tumors. Even with small STS tumor fragments for TIL expansion, more than 90% of the fragments were expanded sufficiently for analyses. Expanded lymphocytes were mostly NK cells (TINKs) which was confirmed with flow cytometry (NKp46+ CD5(dim) TCRαβ− TCRγδ− CD4− B220−CD1d−) and RNA sequencing. TINKs effectively kill autologous tumor cells and the NK-sensitive canine tumor cell line CTAC and result in a significantly increased expression of Granzyme B and Th1 cytokines (IFN-γ, TNF-α and GM-CSF) upon co-culturing with tumor cells. Although adoptively transferred TINK cells showed a significant inhibition in xenograft CTAC tumor growth, combinatory therapy with huB10G5 further significantly inhibited tumor growth. The anti-MIC antibody huB10G5 showed specific binding to canine sarcoma tumor cell lines, fresh processed tumor cells and tumor tissues. Similar to canine STS, NK infiltration in human UPS is significantly higher than in other types of sarcoma tumors. IHC demonstrated that MIC is broadly expressed in human UPS. Similarly, huB10G5 significantly enhanced the in vivo therapeutic effect of PBMC-expanded human NK cells against human sarcoma xenografts. Conclusions: Our results demonstrated that functional TINKs can be efficiently expanded from canine sarcoma tumor tissue and demonstrated therapeutic potential in vivo allowing us to better model human disease. Anti-MIC treatment enhanced the efficacy of NK therapy in both canine and human sarcoma xenografts mouse models. Citation Format: Weiqing Jing, Himaly Shinglot, Juliana Ng, Milan Medd, Ali Zhang, abhilasha srivastava, Shay Bracha, Laura Selmic, Chelsea Tripp, Farres Obeidin, Jennifer Wu, Seth Pollack. Anti-MICA/B antibody promote anti-tumor activity of cytokine expanded tumor infiltrated natural killer (TINK) cells from canine sort tissue sarcomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 878.