Measurement of CAR copy number
Peripheral blood samples were obtained prior to 4SCAR-T cell infusion and at the indicated time points post infusion (Day 7, 14, 21, and 28). Genomic DNA was extracted from peripheral blood using a genomic DNA purification kit (Promega). The copy number of 4SCAR-T cells was determined by real-time quantitative PCR (RT-qPCR), as previously described [