PT - JOURNAL ARTICLE AU - Aneta Ledererova AU - Lenka Dostalova AU - Veronika Kozlova AU - Helena Peschelova AU - Adriana Ladungova AU - Martin Culen AU - Tomas Loja AU - Jan Verner AU - Sarka Pospisilova AU - Michal Smida AU - Veronika Mancikova TI - Hypermethylation of CD19 promoter enables antigen-negative escape to CART-19 in vivo and in vitro AID - 10.1136/jitc-2021-002352 DP - 2021 Aug 01 TA - Journal for ImmunoTherapy of Cancer PG - e002352 VI - 9 IP - 8 4099 - http://jitc.bmj.com/content/9/8/e002352.short 4100 - http://jitc.bmj.com/content/9/8/e002352.full SO - J Immunother Cancer2021 Aug 01; 9 AB - Background Anti-CD19 chimeric antigen receptor T cells (CART-19) frequently induce remissions in hemato-oncological patients with recurred and/or refractory B-cell tumors. However, malignant cells sometimes escape the immunotherapeutic targeting by CD19 gene mutations, alternative splicing or lineage switch, commonly causing lack of CD19 expression on the surface of neoplastic cells. We assumed that, in addition to the known mechanisms, other means could act on CD19 to drive antigen-negative relapse.Methods Herein, we studied the mechanism of antigen loss in an in vivo CD19-negative recurrence model of chronic lymphocytic leukemia (CLL) to CART-19, established using NOD-scid IL2Rgnull mice and HG3 cell line. We validated our findings in vitro in immortalized B-cell lines and primary CLL cells.Results In our in vivo CLL recurrence model, up to 70% of CART-19-treated mice eventually recurred with CD19-negative disease weeks after initial positive response. We found that the lack of CD19 expression was caused by promoter DNA hypermethylation. Importantly, the expression loss was partially reversible by treatment with a demethylating agent. Moreover, this escape mechanism was common for 3 B-cell immortalized lines as well as primary CLL cells, as assessed by in vitro coculture experiments.Conclusions Epigenetically driven antigen escape could represent a novel, yet at least partially reversible, means of CD19 loss to CART-19 in B-cell tumors.Data sharing not applicable as no datasets generated and/or analysed for this study. Data are available upon reasonable request. All data relevant to the study are included in the article or uploaded as supplementary information. Publication-related data are available upon request from the corresponding authors.