P1368: nkg2a deletion in human natural killer cells enhances anti-tumor responses and promotes tumor infiltration

Topic: 24. Gene therapy, cellular immunotherapy and vaccination - Biology & Translational Research Background: Checkpoint blockage has revolutionized cancer treatment. NKG2A is an inhibitory receptor expressed by cytotoxic lymphocytes, including NK cells. In contrast to other checkpoint inhibitory antibodies, anti-NKG2A antibodies have shown only limited success. Nevertheless, recent studies highlight the importance of targeting the NKG2A pathway in cancer treatment. NK cells have seen increased attention as safe and competent effector cells for adoptive cell therapy, making it important to effectively target the NKG2A pathway. Therefore, we hypothesized that genetic deletion of KLRC1, the gene encoding NKG2A, in human NK cells is an effective and safe way to improve anti-tumor responses. Aims: We aimed to enhance anti-tumor responses of NK cells via genetic deletion of the checkpoint NKG2A in primary human NK cells. Methods: Here, we designed a Cas9-based strategy to efficiently delete KLRC1 from primary human NK cells. We then used cell lines, primary human cancer cells and tumor xenograft models to determine the effects of NKG2A genetic deletion versus NK cells alone and antibody-based blockade. Results: NKG2A-deficient NK cells showed normal proliferation, only minor transcriptional changes related to enhanced NK cell activation and maintained their phenotype and licensing status. Genetic deletion of NKG2A fully bypassed HLA-E inhibition and further enhanced NK cell activity against various tumor cell lines, thereby outperforming anti-NKG2A antibodies. In combination with antibody-coating of tumor cells to induce antibody-dependent cellular cytotoxicity, genetic deletion of NKG2A independently promoted cytotoxicity against multiple cell lines. NKG2A-deficient NK cells outperformed NKG2A antibody blockage in an assay with primary AML and ALL samples from 11 donors. Lastly, we compared untreated human NK cells, NK cells combined with anti-NKG2A antibodies and NKG2A-deficient NK cells in breast cancer and multiple myeloma xenograft models. Here, found that NKG2A-deficient NK cells best controlled tumor growth, probably explained by the observed higher cytokine production levels and better infiltration of the tumors by NK cells. Summary/Conclusion: Thus, Cas9-mediated targeting of NKG2A is an effective way to enhance the anti-tumor capacity of human NK cells via direct cytotoxicity and antibody-dependent cellular cytotoxicity. Moreover, NKG2A deletion promotes tumor infiltration via mechanisms yet to be uncovered. This technique is easily amenable to adoptive cell therapy in the clinical setting, where NKG2A deletion will promote anti-tumor responses and help NK cells to better infiltrate and persist in an inhibitory tumor microenvironment. Keywords: NK cell, Adoptive immunotherapy, Cellular therapy