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- Decavanadate and metformin-decavanadate effects in human melanoma cellsPublication . de Sousa-Coelho, Ana Luísa; Aureliano, Manuel; Fraqueza, Gil; Serrão, Gisela; Gonçalves, João; Sánchez-Lombardo, Irma; Link, Wolfgang; Ferreira, BibianaDecavanadate is a polyoxometalate (POMs) that has shown extensive biological activities, including antidiabetic and anticancer activity. Importantly, vanadium-based compounds as well as antidiabetic biguanide drugs, such as metformin, have shown to exert therapeutic effects in melanoma. A combination of these agents, the metformin-decavanadate complex, was also recognized for its antidiabetic effects and recently described as a better treatment than the monotherapy with metformin enabling lower dosage in rodent models of diabetes. Herein, we compare the effects of decavanadate and metformin-decavanadate on Ca2+-ATPase activity in sarcoplasmic reticulum vesicles from rabbit skeletal muscles and on cell signaling events and viability in human melanoma cells. We show that unlike the decavanadate-mediated non-competitive mechanism, metformin-decavanadate inhibits Ca2+-ATPase by a mixed-type competitive-non-competitive inhibition with an IC50 value about 6 times higher (87 mu M) than the previously described for decavanadate (15 mu M). We also found that both decavanadate and metformin-decavanadate exert antiproliferative effects on melanoma cells at 10 times lower concentrations than monomeric vanadate. Western blot analysis revealed that both, decavanadate and metformin-decavanadate increased phosphorylation of extracellular signal-regulated kinase (ERK) and serine/ threonine protein kinase AKT signaling proteins upon 24 h drug exposure, suggesting that the anti-proliferative activities of these compounds act independent of growth-factor signaling pathways.
- Repurposing therapeutic drugs complexed to Vanadium in CancerPublication . De Sousa-Coelho, Ana Luísa; Fraqueza, Gil; Aureliano, M.Repurposing drugs by uncovering new indications for approved drugs accelerates the process of establishing new treatments and reduces the high costs of drug discovery and development. Metal complexes with clinically approved drugs allow further opportunities in cancer therapy—many vanadium compounds have previously shown antitumor effects, which makes vanadium a suitable metal to complex with therapeutic drugs, potentially improving their efficacy in cancer treatment. In this review, covering the last 25 years of research in the field, we identified non-oncology-approved drugs suitable as ligands to obtain different vanadium complexes. Metformin-decavanadate, vanadium-bisphosphonates, vanadyl(IV) complexes with non-steroidal anti-inflammatory drugs, and cetirizine and imidazole-based oxidovanadium(IV) complexes, each has a parent drug known to have different medicinal properties and therapeutic indications, and all showed potential as novel anticancer treatments. Nevertheless, the precise mechanisms of action for these vanadium compounds against cancer are still not fully understood.