Genomic DNA of day 0 samples and xenograft tumor were extracted from each sample with the Qiagen Blood & Cell Culture Midi Kit. sgRNA cassettes were PCR-amplified from genomic DNA of each sample. The amplicons resulting from the second PCR were extracted with beads (Beckman Coulter, USA), quantiﬁed, mixed, and sequenced using a NextSeq 500 instrument (Illumina, USA).