All-trans retinoic acid and lansoprazole potentiated NKG2D-CAR T for breast cancer treatment.

In solid cancer, the tumor microenvironment (TME) poses significant challenges to chimeric antigen receptor (CAR) T cell therapy due to its dense physical barrier, abnormal metabolism, and immunosuppressive factors. This study addresses these limitations using a synergistic approach involving all-trans retinoic acid (ATRA) and lansoprazole (LPZ) to target fibrosis and acidity, respectively. In vitro, ATRA reversed activated cancer-associated fibroblasts to a quiescent state, reducing α-SMA production, while LPZ increased tumor-site pH (Δ pH = 0.54) by inhibiting V-ATPase expression. In a triple-negative breast cancer (TNBC) model, a temperature-sensitive hydrogel delivering ATRA and LPZ was administered prior to drug-loaded NKG2D-CAR T (N-CAR T) cell injection, achieving a tumor inhibition rate of 72.08%. Notably, co-culture with ATRA and LPZ enhanced N-CAR T activity, cytokine secretion, and promoted differentiation into more lethal CD8+ subtypes (p < 0.0001), amplifying the immune response. These findings establish a targeted, potent, and low-toxicity preconditioning strategy to enhance CAR T cell efficacy in solid tumors, supporting further validation in more complex models and human-relevant systems.