WRN and breast cancer: There are five RecQ helicases in human cells: RecQ-like helicase 1 (RECQL1), Werner syndrome RecQ-like helicase (WRN), Bloom syndrome RecQ-like helicase (BLM), RecQ-like helicase 4 (RECQL4) and RecQ-like helicase 5 (RECQL5) (9,10,12) Mutations in WRN, BLM and RECQL4 proteins can lead to genomic instability and predisposition to cancers, including colorectal, prostate and breast cancers (13–16).