The ionophore thiomaltol induces rapid lysosomal accumulation of copper and apoptosis in melanoma

Ottis Scrivner, Long Dao, M. Karen Newell-Rogers, Babbak Shahandeh, Frank L. Meyskens, Susan Kurumi Kozawa, Feng Liu-Smith, Germán Plascencia-Villa, Miguel José-Yacamán, Shang Jia, Christopher J. Chang, Patrick J. Farmer

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


In this report, we investigate the toxicity of the ionophore thiomaltol (Htma) and Cu salts to melanoma. Divalent metal complexes of thiomaltol display toxicity against A375 melanoma cell culture resulting in a distinct apoptotic response at submicromolar concentrations, with toxicity of Cu(tma)2 > Zn(tma)2 >> Ni(tma)2. In metal-chelated media, Htma treatment shows little toxicity, but the combination with supplemental CuCl2, termed Cu/Htma treatment, results in toxicity that increases with suprastoichiometric concentrations of CuCl2 and correlates with the accumulation of intracellular copper. Electron microscopy and confocal laser scanning microscopy of Cu/Htma treated cells shows a rapid accumulation of copper within lysosomes over the course of hours, concurrent with the onset of apoptosis. A buildup of ubiquitinated proteins due to proteasome inhibition is seen on the same timescale and correlates with increases of copper without additional Htma.

Original languageEnglish (US)
Article numbermfab074
Issue number1
StatePublished - Jan 1 2022


  • apoptosis
  • copper ionophore
  • melanoma
  • proteasome inhibition
  • thiomaltol

ASJC Scopus subject areas

  • General Medicine


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