The results showed that cryopreserved PDC carried a heterozygous “A” insertion mutation at exon 9 of the RB1 gene, resulting in a frameshift mutation inducing premature stop codon, whereas this mutation was not observed in the osteoblast cell line (hFOB1.19) or osteosarcoma cell line (U2OS) (Fig. 3E). The gene discussed is RB1; the disease is osteosarcoma.