ATOX1 gene silencing increases susceptibility to anticancer therapy based on copper ionophores or chelating drugs

• ATOX1 (antioxidant protein 1) is a copper chaperone that plays a role in Cu homeostasis.
• ATOX1 silencing increases copper toxicity in Caco-2 colon cancer cell line.
• 5-Chloro-8-hydroxyquinoline induces a Cu-dependent toxicity potentiated by ATOX1 silencing.
• Cu chelation by TPEN produces a form of cell toxicity that was reversed by Cu2 + addition.
• ATOX1 silencing increases Caco-2 cell sensitivity to TPEN toxicity.

Copper is a catalytic cofactor required for the normal function of many enzymes involved in fundamental biological processes but highly cytotoxic when in excess. Therefore its homeostasis and distribution is strictly regulated by a network of transporters and intracellular chaperones. ATOX1 (antioxidant protein 1) is a copper chaperone that plays a role in copper homeostasis by binding and transporting cytosolic copper to ATPase proteins in the trans-Golgi network. In the present study the Caco-2 cell line, a colon carcinoma cell line, was used as an in vitro model to evaluate if ATOX1 deficiency could affect sensitivity to experimentally induced copper dyshomeostasis. Silencing of ATOX1 increased toxicity of a short treatment with a high concentration of Cu2 +. Copper ionophores, such as 5-chloro-8-hydroxyquinoline, induced a copper-dependent cell toxicity which was significantly potentiated after ATOX1 silencing. The copper chelator TPEN (N,N,N′,N′-tetrakis (2-pyridylmethyl) ethylenediamine) produced a form of cell toxicity that was reversed by the addition of Cu2 +. ATOX1 silencing increased Caco-2 cell sensitivity to TPEN toxicity. Our results suggest the possibility of a therapy with copper-chelating or ionophore drugs in subtypes of tumors showing specific alterations in ATOX1 expression.

The copper chaperone ATOX1 (antioxidant protein 1) plays a role in copper homeostasis by binding and transporting cytosolic copper to trans-Golgi network ATPase proteins. Copper dyshomeostasis, induced by ATOX1 silencing, enhances toxicity of copper overload or treatments with ClHQ (5-chloro-8-hydroxyquinoline)/Cu2 + complexes or with the copper chelator TPEN (N,N,N′,N′-tetrakis (2-pyridylmethyl) ethylenediamine).Figure optionsDownload as PowerPoint slide