Notably, HT72, HT77, and HT87 acquired a deletion of RB1 in one allele during the PDX serial passaging (Figure 3A–C; Table S2A–C), which was not seen in the respective P0 sample, whereas HT96 maintained the RB1 deletion found in the original tumor (Figure 3D; Table S2D). This evidence concerns the gene RB1 and neoplasm.