Point mutation in <i>CD19</i> facilitates immune escape of B cell lymphoma from CAR-T cell therapy
Zhen Zhang, Xinfeng Chen, Yonggui Tian, Feng Li, Xuan Zhao, Jinyan Liu, Chang Yao, Yi Zhang
Abstract
Background Tumor relapse due to mutation in CD19 can hinder the efficacy of chimeric antigen receptor (CAR)-T cell therapy. Herein, we focused on lymphoma patients whose B cells exhibited a point mutation in CD19 of B cells after CAR-T cell infusion. Methods The CAR-T and CD19 + B cells from peripheral blood or bone marrow were assessed using flow cytometry. Genome sequencing was conducted to identify the molecular characteristics of CAR-T and CD19 + B cells from pre-relapse and postrelapse samples. CD19 in CARs comprising single chain fragments variable (scFV) antibody with FMC63 or 21D4 was constructed. The cytotoxic efficacy of CAR-T cells was also evaluated via in vitro and in vivo experiments. Results A patient with high-grade B cell lymphoma exhibited complete response, but the lymphoma relapsed in her left breast at 6 months after CD19 CAR (FMC63)-T cell infusion. A mutation was found in exon 3 of CD19 (p.163. R-L) in malignant B cells of the patient. In two lymphoma patients who exhibited resistance to CAR-T cell therapy, a mutation was detected in exon 3 of CD19 (p.174. L-V). Functional analysis revealed that FMC63 CAR-T cells exhibited antitumor ability against wild-type CD19 + cells but were unable to eradicate these two types of mutated CD19 + cells. Interestingly, 21D4 CAR-T cells were potentially capable of eradicating these mutated CD19 + cells and exhibiting high antitumor capacity against CD19 + cells with loss of exon 1, 2, or 3. Conclusions These findings suggest that point mutation can facilitate immune escape from CAR-T cell therapy and that alternative CAR-T cells can effectively eradicate the mutated B cells, providing an individualized therapeutic approach for lymphoma patients showing relapse.