Austin D. Newsam

Genomic features associated with CAR-19 progression.

Phenotypic characterization of RHOA LoF lymphoma cell lines.

CD19 loss is RHOA-dependent and regulated at the mRNA level.

Pathway analysis and LME features of syngeneic shRhoa tumors.

Characteristics of tumor and CAR-T cells in scRNA-seq data of CAR-T treated mice.

IFNγ-induced cytokine secretion and viability of parental and RHOA LoF lymphoma systems.

Supplementary Table 1 from RHOA Deletion Downregulates CD19 and Promotes Dysfunctional Immune Microenvironments in CAR T–Resistant Large B-cell Lymphomas

Patient characteristics in the combined data sets.

RNA-seq of RIVA sgRHOA engineered cells.

CD19-directed chimeric antigen receptor (CAR-19) T cells are breakthrough therapies for large B-cell lymphomas (LBCL), but fewer than half of patients achieve durable responses. We previously showed that RHOA deletions are enriched in progressing cases, but the role of RHOA deficiency is poorly defined despite its frequent occurrence in newly diagnosed disease. In this study, we show that RHOA loss downregulates CD19, promoting cell-intrinsic resistance to CAR-19 in vitro and in vivo. CD19 decline, however, provides an incomplete explanation of resistance and does not explain high frequency of the deletion in newly diagnosed cases. We therefore performed single-cell assessments of immunocompetent RHOA-deficient lymphoma microenvironments (LME), revealing remarkable concordance with features in CAR-19–resistant patients. Despite increased microenvironmental production of interferon gamma, RHOA-deficient tumor cells themselves show an impaired response to the cytokine, including failed induction of class I MHC molecules. Overall, we describe for the first time how a single-gene alteration recurrent in CAR-19–resistant lymphoma contributes to treatment failures. Significance: RHOA loss of function, which predicts CAR T-cell treatment failure and is present in one in six newly diagnosed LBCL cases, impairs MHC class I display, reprograms LMEs, and downregulates CD19 to promote antigen escape. Del 3p21.31 is therefore a single-gene alteration in LBCL selected for immunotherapy resistance. See related commentary by Perkey and Kline, p. 852