VCP downstream metabolite glycerol-3-phosphate (G3P) inhibits CD8⁺T cells function in the HCC microenvironment

CD8⁺T cells within the tumor microenvironment (TME) are often functionally impaired, which limits their ability to mount effective anti-tumor responses. However, the molecular mechanisms behind this dysfunction remain incompletely understood. Here, we identified valosin-containing protein (VCP) as a key regulator of CD8⁺T cells suppression in hepatocellular carcinoma (HCC). Our findings reveal that VCP suppresses the activation, expansion, and cytotoxic capacity of CD8⁺T cells both in vitro and in vivo, significantly contributing to the immunosuppressive nature of the TME. Mechanistically, VCP stabilizes the expression of glycerol-3-phosphate dehydrogenase 1-like protein (GPD1L), leading to the accumulation of glycerol-3-phosphate (G3P), a downstream metabolite of GPD1L. The accumulated G3P diffuses into the TME and directly interacts with SRC-family tyrosine kinase LCK, a critical component of the T-cell receptor (TCR) signaling pathway in CD8⁺T cells. This interaction heightens the phosphorylation of Tyr505, a key inhibitory residue, ultimately reducing LCK activity and impairing downstream TCR signaling. Consequently, CD8⁺T cells lose their functional capacity, diminishing their ability to fight against HCC. Importantly, we demonstrated that targeting VCP in combination with anti-PD1 therapy significantly suppresses HCC tumor growth and restores the anti-tumor function of CD8⁺T cells, suggesting synergistic therapeutic potential. These findings highlight a previously unrecognized mechanism involving VCP and G3P in suppressing T-cell-mediated immunity in the TME, positioning VCP as a promising upstream target for enhancing immunotherapy in HCC.