EGFR and neoplasm: Together with its ability to protect Tet-HER1-CAR-T cells from tumor-acidity-induced dysfunction by neutralizing tumor acidity, Doxy@CaCO3-PEG injection synergized with Tet-HER1-CAR-T cells to effectively suppress the growth of HER1-overexpressing subcutaneous triple-negative breast cancer (TNBC) tumors, lung tumors and orthotopic lung tumors in mice.