Strategies that enhance the function of chimeric antigen receptor-modified T (CAR-T) cells for solid tumors are critical. Inhibitory immuno-checkpoints blockade could potentially enhance CAR-T cell function. TIM-3 is an important negative regulator of T cell activity, but whether TIM-3 blockade could affect CAR-T cell function remains unclear. In our study, we successfully constructed TIM-3-silenced CAR-T cells by dual-promoter lentivirus vectors that simultaneously express the TIM-3 targeting short hairpin RNA (shRNA) and a third-generation CAR recognizing HER2. We demonstrated that down-regulation of TIM-3 did not affect the phenotype of CAR-T cells. CAR-T cells with TIM-3 blockade exhibited higher lytic cytotoxicity to target cells in vitro. Additionally, TIM-3-silenced CAR-T cells displayed robust anti-tumor activity in a murine xenograft model, which is comparable to standard CAR-T cells. Our study demonstrates the effect of down-regulation of immune checkpoint TIM-3 on the anti-tumor function of CAR T cells, providing new ideas for improving the potency of CAR-T cell therapies in solid tumors.

Intestinal cancers are developed from intestinal epithelial stem cells (ISCs) in intestinal crypts through a multi-step process involved in genetic mutations of oncogenes and tumor suppressor genes. ISCs play a key role in maintaining the homeostasis of gut epithelium. In 2009, Sato et al established a three-dimensional culture system, which mimicked the niche microenvironment by employing the niche factors, and successfully grew crypt ISCs into organoids or Mini-guts in vitro. Since then, the intestinal organoid technology has been used to delineate cellular signaling in ISC biology. However, the cultured organoids consist of heterogeneous cell populations, and it was technically challenging to introduce genomic changes into three-dimensional organoids. Thus, there was a technical necessity to develop a two-dimensional ISC culture system for effective genomic manipulations. In this study, we established a conditionally immortalized mouse intestinal crypt (ciMIC) cell line by using a piggyBac transposon-based SV40 T antigen expression system. We showed that the ciMICs maintained long-term proliferative activity under two-dimensional niche factor-containing culture condition, retained the biological characteristics of intestinal epithelial stem cells, and could form intestinal organoids in three-dimensional culture. While in vivo cell implantation tests indicated that the ciMICs were non-tumorigenic, the ciMICs overexpressing oncogenic β-catenin and/or KRAS exhibited high proliferative activity and developed intestinal adenoma-like pathological features in vivo. Collectively, these findings strongly suggested that the engineered ciMICs should be used as a valuable tool cell line to dissect the genetic and/or epigenetic underpinnings of intestinal tumorigenesis.