Modulation of Transcription Profile Induced by Antiproliferative Thiosemicarbazone Metal Complexes in U937 Cancer Cells

Synthesis and Preliminary Studies for In Vitro Biological Activity of Two New Water-Soluble Bis(thio)carbohydrazones and Their Copper(II) and Zinc(II) Complexes

Research in the field of metallodrugs is continually increasing. However, it is often limited by the poor solubility in water of the metal complexes. To try to overcome this problem, the two new ligands bis-(sodium 3-methoxy-5-sulfonate-salicylaldehyde)thiocarbohydrazone (bis-TCH, Na2H4L1) and bis-(sodium 3-methoxy-5-sulfonate-salicylaldehyde)carbohydrazone (bis-CH, Na2H4L2) were synthesized and characterized, both achieving high solubility in water. The speciation of the ligands and their coordinating behaviour towards the biologically relevant Cu(II) and Zn(II) ions were studied spectroscopically and potentiometrically, determining the pKas of the ligands and the formation constants of the complex species. The monometallic and bimetallic Cu(II) and Zn(II) complexes were isolated, and the single-crystal X-ray structure of [Cu2(NaHL1)(H2O)7].3.5H2O was discussed. Finally, preliminary studies of the in vitro cytotoxic properties of the new compounds were started on normal (Hs27) and cancer (U937) cell lines. bis-TCH was able to induce a growth inhibition effect between 40% and 45% in both cell lines; bis-CH did not produce a reduction in cell viability in Hs27 cells but revealed mild antiproliferative activity after 72 h of treatment in U937 cancer cells (GI50 = 46.5 ± 4.94 μg/mL). Coordination of the Cu(II) ions increased the toxicity of the compounds, while, in contrast, Zn(II) complexes were not cytotoxic.

Recent progress in thiocarbazone metal complexes for cancer therapy via mitochondrial signalling pathway

Mitochondria are the energy factories of cells and are important targets for the development of novel tumour treatment strategies owing to their involvement in processes such as apoptosis, oxidative stress, and metabolic programming. Thiosemicarbazone metal complexes target mitochondria and reduce mitochondrial membrane potential. The breakdown of mitochondrial membrane potential is a key event in the early stage of apoptosis, which releases cytochrome C and other pro-apoptotic factors, activates the intracellular apoptotic enzyme cascade, and eventually causes irreversible apoptosis of tumour cells. Thiosemicarbazone metal complexes targeting the mitochondria have recently emerged as potential antitumour agents; therefore, this review describes the structural diversity of thiosemicarbazone metal [Fe(III), Cu(II), Ni(II), Zn(II), Ga(III), Pb(II), Au(III), and Ir(III)] complexes and explores their anti-tumour mechanisms that target mitochondrial pathways.