Members of the Ca2+‐activated K+ channel (KCa) family, that is BK (also known as KCa1.1, Maxi‐K or Slo1) and SK4 (also known as KCa3.1 or IK), have been implicated in the progression of malignant diseases including but not limited to gliomas (D'Alessandro et al., 2013; Liu et al., 2002; Turner et al., 2014), clear cell renal cell carcinoma (Rabjerg et al., 2015) and breast cancer (Haren et al., 2010; Oeggerli et al., 2012; Thurber et al., 2017). The gene discussed is IK; the disease is breast cancer.