Otherwise, under the circumstance of downregulation of piRNA and low DNA methylation of the LINE-1 TEs, it has been observed that the repression of PIWIL1, PIWIL2, PIWIL4, and Tudor domain-containing protein 1 (TDRD1) was associated with hypermethylation of the promoter CpG island in testicular tumors 118. Here, TDRD1 is linked to neoplasm of testis.