Among 33 different human cancer types based on molecular similarity (Fig. 1A), five different cancer types, lung adenocarcinoma (LUAD), lung squamous cell carcinoma (LUSC), ovarian serous cystadenocarcinoma (OV), skin cutaneous melanoma (SKCM), and testicular germ cell tumors (TGCT), showed significantly downregulated expression of USP15 (Fig. 1B, tumor (T) vs. normal (N)), whereas no significant change in expression of USP15 was observed in 28 other cancer types (Fig. 1A, black letters). This evidence concerns the gene USP15 and ovarian serous cystadenocarcinoma.