Expression of various potassium channels that have been implicated in cancer. Red boxes indicate that overexpression is reported (in most cases) and that the channel enhances tumorigenic processes, for example by driving proliferation, cell migration, or metastasis (Bielanska et al., 2009; Williams et al., 2013; Pardo and Stühmer, 2014). Green boxes indicate that the channel expression is inversely correlated with tumor malignancy and clinical aggressiveness, such as KCNA5 in glioma (Preussat et al., 2003) and lymphoma (Bielanska et al., 2009), and KCNQ1 in colorectal cancer (Than et al., 2013). The blue box indicates the presence of recurring somatic mutations in the KCNJ5 gene detected in adrenal adenomas (Choi et al., 2011). GI, gastrointestinal.