Cisplatin (CisPt) is one of the most common anticancer drugs used against many severe forms of cancers.
However, treatment with this drug causes many side effects and often, it results in the development of cell resistance. A
majority of side effects as well as cell resistance are thought to develop due to CisPt interactions with proteins prior to
reaching the nucleus and the DNA target. The copper (Cu) transport proteins Ctr1 and ATP7A/B have been implicated in
cellular resistance of CisPt, possibly exporting the drug out of the cell. Recent in vitro work demonstrated that CisPt also
interacts with the cytoplasmic Cu-chaperone Atox1, binding in or near the Cu-binding site, without expulsion of bound
Cu. Whereas Ctr1 and ATP7B interactions with CisPt have been shown in vivo or ex vivo, there is no such information for
Atox1-CisPt interactions. To address this, we developed a method to probe if CisPt interacts with Atox1 in human melanoma
cells. Atox1-specific antibodies were linked to magnetic beads and used to immune-precipitate Atox1 from melanoma
cells that had been pre-exposed to CisPt. Analysis of extracted Atox1 with inductively coupled plasma mass spectrometry
demonstrated the presence of Pt in the protein fraction. Thus, CisPt-exposed human melanoma cells contain
Atox1 molecules that bind some derivative of CisPt. This study gives the first indication for the intracellular presence of
Atox1-CisPt complexes ex vivo.