USP8 and ACTH-producing pituitary gland adenoma: Apart from HIFs, USP8 is involved in epidermal growth factor receptor (EGFR) turnover, thus rescuing EGFR from lysosomal degradation [73], and mutations in the USP8 gene have been found in corticotroph adenomas, which could cause Cushing’s disease via activation of EGFR signaling [74].