The field of chimeric antigen receptor (CAR) modified T cell therapy has rapidly expanded in the past few decades. As of today, there are six CAR T cell products that have been approved by the FDA: KYMRIAH (tisagenlecleucel, CD19 CAR T cells), YESCARTA (axicabtagene ciloleucel, CD19 CAR T cells), TECARTUS (brexucabtagene autoleucel, CD19 CAR T cells), BREYANZI (lisocabtagene maraleucel, CD19 CAR T cells), ABECMA (idecabtagene vicleucel, BCMA CAR T cells) and CARVYKTI (ciltacabtagene autoleucel, BCMA CAR T cells). With this clinical success, CAR T cell therapy has become one of the most promising treatment options to combat cancers. Current research efforts focus on further potentiating its efficacy in non-responding patients and solid tumor settings. To achieve this, recent evidence suggested that, apart from developing next-generation CAR T cells with additional genetic modifications, ex vivo culture conditions could significantly impact CAR T cell functionality – an often overlooked aspect during clinical translation. In this review, we focus on the ex vivo manufacturing process for CAR T cells and discuss how it impacts CAR T cell function.

Chronic lymphocytic leukemia (CLL) patients progressively develop an immunosuppressive state. CLL patients have more plasma IL-10, an anti-inflammatory cytokine, than healthy controls. In vitro human CLL cells produce IL-10 in response to BCR cross-linking. We used the transgenic Eμ-T cell leukemia oncogene-1 () mouse CLL model to study the role of IL-10 in CLL associated immunosuppression. Eμ-TCL mice spontaneously develop CLL because of a B cell-specific expression of the oncogene, Eμ- mouse CLL cells constitutively produce IL-10, which is further enhanced by BCR cross-linking, CLL-derived IL-10 did not directly affect survival of murine or human CLL cells in vitro. We tested the hypothesis that the CLL-derived IL-10 has a critical role in CLL disease in part by suppressing the host immune response to the CLL cells. In IL-10R mice, wherein the host immune cells are unresponsive to IL-10-mediated suppressive effects, there was a significant reduction in CLL cell growth compared with wild type mice. IL-10 reduced the generation of effector CD4 and CD8 T cells. We also found that activation of BCR signaling regulated the production of IL-10 by both murine and human CLL cells. We identified the transcription factor, Sp1, as a novel regulator of IL-10 production by CLL cells and that it is regulated by BCR signaling via the Syk/MAPK pathway. Our results suggest that incorporation of IL-10 blocking agents may enhance current therapeutic regimens for CLL by potentiating host antitumor immune response.