Targeting ion channels in leukemias: a new challenge for treatment.

Leukemias, as other cancers, bear several genetic alterations of tumor-related genes, such as point mutations, translocations, epigenetic modifications, often accompanied by gene amplification or inactivation. The identification of tumor-related genes provides considerable insight into the biology of leukemias and opens the way to more specific pharmacological treatments. These genes comprise several ion channels and pumps, as the transport mechanisms associated with volume control, proliferation and apoptosis are often altered in cancers. In leukemic cells, such changes are observed as early as the stem cell stage. Ion channels can regulate other malignant features, such as lack of differentiation, increased migratory and invasive phenotype and chemoresistance. The role of certain voltage-gated K(+) channels, such as K(v)11.1 (also known as hERG1) can be largely attributed to modulation of cell adhesion to the extracellular matrix (ECM). K(v)11.1 exerts pleiotropic regulatory effects by forming multiprotein membrane complexes with integrin receptors in both acute myeloid leukemias (AML) and acute lymphoblastic leukemias (ALL). By recruiting growth factor and chemokine receptors, these complexes form signaling hubs that control neoplastic progression. Work in mice shows that blocking K(v)11.1 has a protective effect in acute leukemias. Ion channels are most promising targets for anti-leukemic therapy, because of their accessibility from the extracellular side and the thorough understanding of their pharmacology. In ALL cells, K(v)11.1 inhibitors abrogate the protective effect of bone marrow stromal cells and enhance the cytotoxicity of some common antileukemic drugs. Hence, ion channel modulators could overcome chemoresistance in acute leukemias, a major hindrance to therapeutic success.