Acetylcysteine synergizes PD-1 blockers against colorectal cancer progression by promoting TCF1+PD1+CD8+ T cell differentiation.

Background: Programmed cell death protein 1 (PD-1) blockade is essential in treating progressive colorectal cancer (CRC). However, some patients with CRC do not respond well to immunotherapy, possibly due to the exhaustion of CD8⁺ T cells in the tumor microenvironment. N-Acetylcysteine (NAC) can reduce CD8⁺ T cell exhaustion in vitro and induce their differentiation into long-lasting phenotypes, thus enhancing the anti-tumor effect of adoptive T cell transfer. However, whether NAC can be combined with PD-1 blockade in CRC treatment and how NAC regulates CD8⁺ T cell differentiation remain unclear. Hence, in this study, we aimed to investigate whether NAC has a synergistic effect with PD-1 blockers against CRC progression.

Methods: We constructed a mouse CRC model to study the effect of NAC on tumors. The effect of NAC on CD8 + T cell differentiation and its potential mechanism were explored using cell flow assay and other studies in vitro and ex vivo.

Results: We demonstrated that NAC synergized PD-1 antibodies to inhibit CRC progression in a mouse CRC model mediated by CD8⁺ T cells. We further found that NAC can induce TCF1⁺PD1⁺CD8⁺ T cell differentiation and reduce the formation of exhausted T cells in vitro and in vivo. Moreover, NAC enhanced the expression of Glut4 in CD8⁺ T cells, promoting the differentiation of TCF1⁺PD1⁺CD8⁺ T cells.

Conclusions: Our study provides a novel idea for immunotherapy for clinically progressive CRC and suggests that Glut4 may be a new immunometabolic molecular target for regulating CD8⁺ T cell differentiation.