library_construction_protocol: On day 14, tumors were resected and snap-frozen. Genomic DNA (gDNA) was extracted from the excised tumors for guide RNA sequencing using the NucleoSpin Blood XL kit following manufacturer instructions. sgRNA sequences were amplified from the gDNA using custom PCR primers. The amplified gRNA library was prepared for sequencing to quantify the relative abundance of each guide RNA in the harvested tumor samples. The libraries were constructed to accommodate the short read length necessary to capture the guide sequence.