T cell and glioblastoma cell line U87 cocultured were collected and resuspend in PBS for FACS. Constitutive GD2CAR T cells and EchoBack GD2CAR T cells were sorted for mCherry signal (maker of CAR-T cells) using SONY SH800. Sorted Cells were imediately frozen in cyropresrvation buffer (7.5% DMSO+92.5% FBS) until further use. Cells were thawed and washed in DPBS and finaly resuspended in DPBS for library construction. Library was constructed by Molecular Genomics Core at USC Norris Comprehensive Cancer Center foloowing manufacturer's instructions (Chromium platform 10X Genomics and the Chromium Single Cell 3' HT v3.1 kit). cDNA libraries were separately prepared for EchoBack CAR-T cells and standard CAR-T cells.