In a targeted genomic sequence analysis of parental tumors and PDX tissues, additional genomic alterations in cancer-associated genes were observed in PDXs for four of six cases; an EDM mutation in POLE was observed in the parental tumor tissues of one case (UXE-004), and a frameshift deletion (K654fs*47) in BRCA1 was found in the parental tumor tissue of another case (UXE-010). Here, POLE is linked to cancer.