DDX31 and breast cancer: Several of the TOP2B interacting proteins have known nucleolar localization including the: (1) DEAD/DEAH box helicase domain-containing protein DDX18, which is mutated in human AML [71] and implicated as a driver of endocrine resistance in breast cancer cells [72]; (2) DDX31 which helps regulate ribosomal RNA (rRNA) gene transcription in the nucleolus of renal cell carcinomas [73]; and (3) human proteins involved in rRNA processing in the nucleolus (SDAD1 [74] and RRP15 [75]).