Kv3.1, Kv3.3, and Kv3.4 belong to the Kv3 subfamily, which is a class of Kv channels characterized by positively shifted voltage dependencies and very fast deactivation rates [30], and these Kv channels were examined as tumor hypoxia-related Kv channels in A549, MDA-MB-23, and HT-29 cells, which are highly aggressive lung, breast, and colon cancer cell lines, and all three cell lines expressed Kv3.1, Kv3.3, and Kv3.4. The gene discussed is KCNC4; the disease is malignant colon neoplasm.