Two Keggin-type Germanotungstates: Synthesis, characterization, and antitumor mechanism of mitochondrial apoptosis

Abstract

Germanotungstates have been studied variously and widely in antitumor activity aganist various cancer cells; however, their mode of action remains unclear. In this study, we integrated transition metals and organic ligands into the Keggin polyoxometalates via covalence and metal coordination and crystallized two Keggin-type germanotungstates compounds 1 [Mn(2,2ʹ-bpy)3]2[GeW12O40]·0·5H2O and 2 [Fe(2,2ʹ-bpy)2Cl2]2(Hbpy)2[GeW12O40]. Compounds 1 and 2 exhibited high anti-proliferative activities against gastric cancer AGS and MGC803, colon cancer SW480, and liver cancer HepG2 cells, with IC50 values below 50 μmol/L. Further investigation of the molecular mechanism in AGS cells revealed that compounds 1 and 2 repressed the STAT3 pathway and its downstream Bcl-2 family proteins. Downregulation of anti-apoptotic Bcl-2 family proteins leads to the dissipation of mitochondrial membrane potential, eventually triggering caspase-dependent apoptosis. These results demonstrate that compounds 1 and 2 exert antitumor activity via mitochondria-mediated apoptosis. Overall, our findings provide evidence for the development of antitumor germanotungstate-type drugs.