Feeding T cell enhancement of CAR-T cell therapy for minimal B cell malignancy: evidences from in vitro and in vivo models

Although chimeric antigen receptor T (CAR-T) cell therapy has shown remarkable efficacy in treating hematological malignancies, poor persistence presents a major limitation. However, repeated administration of CAR-T cell therapy results in suboptimal efficacy. There is an urgent need to explore novel strategies that provide essential supporting signals to enhance the persistence and antitumor activity of CAR-T cells. We generated feeding T cells (FTCs) that express CD19 or CD20, as well as anti-CD19 and anti-CD20 CAR-T cells. Here, we established in vitro and in vivo models to investigate FTC-enhanced CAR-T cell therapy for B cell malignancy in the minimal residual tumor state. Within these models, we assessed T-cell phenotypes and tumor re-challenge in vitro by flow cytometry, and conducted in vivo cellular kinetics analysis by flow cytometry and quantitative PCR. To elucidate the underlying mechanisms, RNA sequencing was performed to characterize the transcriptional and metabolic changes in CAR-T cells modulated by FTCs versus Raji cells, with normal B cells as a reference control. Our results demonstrate that FTCs promote the activated state of CAR-T cells and enhance their antitumor activity in vitro. Notably, FTCs had beneficial effects on memory CAR-T cell expansion while suppressing CAR-T cell exhaustion and Treg expansion, resulting in durable antitumor activity. Mechanistically, RNA-seq revealed that FTCs promote a memory-associated transcriptional program in CAR-T cells, whereas Raji cells drive glycolytic metabolic reprogramming, with the normal B cells group displaying an intermediate profile. In a mouse model with minimal tumor burden B-cell malignancy, co-infusion of FTCs with low-dose CAR-T cells effectively eradicated both initially minimal and subsequently expanding Raji cells, leading to prolonged survival. Cellular kinetic analysis revealed that high‑dose CAR‑T cells alone exhibited limited expansion and only transiently suppressed tumor growth. In contrast, FTCs markedly enhanced the expansion and antitumor capacity of low‑dose CAR‑T cells, achieving sustained tumor eradication. These results demonstrate that FTCs enhance the activity and persistence of CAR-T cells, contributing to the eradication of minimal residual B-cell malignancy. The FTCs platform may offer a versatile approach that allows for lower CAR-T cell doses.