ASNS and teratoma: To study whether additional copy number variations (CNVs) were acquired during trisomic teratoma metastasis, we performed WGS of primary teratomas and metastatic lesions derived from Ts6, Ts8, Ts11, Ts15, Ts6 + 8, and Ts8 + 15 ESCs, which revealed that most metastases presented CNV patterns similar to those of primary teratomas (Fig. 2a), while only two metastatic samples derived from Ts6 and Ts8 displayed additional single-chromosome gains (Supplementary Fig. 4 and Supplementary Fig. 5).