Abstract 1344: Improvement of the anti-tumor activity of NK cells and the efficacy of anti-CD20 monoclonal antibodies in the therapy of B cell-derived malignancies

Abstract Resistance of tumor cells to immunotherapy with monoclonal antibodies (mAbs) often relies on the reduced level of the antigen targeted by the particular mAb. We have therefore screened for the compounds able to upregulate selected antigens on the surface of lymphoma/leukemia cells, to minimize the possibility of resistance acquired by the tumor cells. We have found that members of a specific class of antibiotics, known as cation carriers, namely salinomycin (SAL), monensin (MON), narasin, and nigericin exhibit great CD20 antigen-upregulating abilities. A variety of Burkitt’s lymphoma and diffuse large B-cell lymphoma (DLBCL) cell lines as well as patients-derived primary malignant cells, such as DLBCL and chronic lymphocytic leukemia (CLL) cells exhibited upregulation of surface CD20 upon the treatment with SAL and MON at concentrations as low as 250nM and 50 nM, respectively. As a consequence, these compounds appeared to be beneficial for the therapy of lymphoma/leukemia with anti-CD20 mAbs, both in vitro and in animal models. Moreover, the proteomics analysis revealed that besides CD20, cation carriers upregulated a number of different proteins on the surface of tumor cells, including proteins implicated in the interaction with immune cells. These included ICAM1, HLA-A/B/C, CD155, CD80, CD86 and ULBP2/5/6. Particularly important appears to be the upregulation of antigens interacting with the activating receptors on NK cells, helping them to overcome the inhibitory signals and stimulate the lysis of tumor cells. Thus, the results of proteomics analysis explained why SAL- or MON-pretreated tumor cells were efficiently eliminated by NK cells, even in the absence of therapeutic mAb. In light of our discoveries, it seems reasonable to consider the cation carriers as promising drug candidates for the improvement of NK cell anti-tumor activity and potential treatment of B-cell non-Hodgkin lymphoma patients, in combination with anti-CD20 mAbs. Funding: National Science Centre (NCN, Poland), grants 2019/35/B/NZ5/01445 and 2020/39/B/NZ6/03513. Citation Format: Abdessamad Zerrouqi, Aleksandra Zdanowicz, Anna Torun, Andrzej Ciechanowicz, Bhaskar Pradhan, Grzegorz Rymkiewicz, Dimitar Efremov, Beata Pyrzynska. Improvement of the anti-tumor activity of NK cells and the efficacy of anti-CD20 monoclonal antibodies in the therapy of B cell-derived malignancies abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 1344.