Therefore, we deleted Usp15 gene by crossing Usp15null mice with mPTC line (homozygotes of Usp15 deletion would be referred as mPTC/Usp15-/-, heterozygotes as mPTC/Usp15+/- in the following text) to determine the biological significance of Usp15 in endogenous tumor formation (Fig. 3g). This evidence concerns the gene USP15 and neoplasm.