USP9X and cancer: DUBs are critical key players in diverse processes such as (i) spermatogenesis (e.g. USP2, USP8, USP9y, USP14, USP26, Uchl-1, Uchl-3 and CYLD) [52], (ii) cancer biology (e.g. USP7, USP10 and USP11) [44,56,57], and (iii) stemness and differentiation (e.g. USP7, USP9x, USP22, USP44 and Psmd14) [58].