Expression of LINE-1 p40 protein in pediatric malignant germ cell tumors and its association with clinicopathological parameters: A report from the Children’s Oncology Group

The long interspersed nucleotide element-1 (LINE-1) p40 protein was expressed in all 162 cases of childhood malignant germ cell tumor (MGCT) cells with weak, moderate, and strong immunoactivity in 43.8%, 37.7%, and 18.5%, respectively. Normal testicular tissue adjacent to tumors showed negative or weaker p40 expression than tumor cells. Multivariate analyses showed that strong expression of p40 was associated with poor differentiation, extragonadal site, and the histotype of yolk sac tumor. This study suggests that the active LINE-1 retrotransposon is a common event in pediatric MGCTs and abundant expression of p40 might play a role during the malignant transformation.