Heteronuclear Ru(II)-Re(I) complexes as potential photodynamic anticancer agents with anti-metastatic and anti-angiogenic activities

Herein, three heterometallic Ru(II)-Re(I) complexes, [Ru(NN)2(tpphz)Re(CO)3Cl](PF6)2 (N-N = 2,2′-bipyridine (bpy, in RuRe1), 1,10-phenanthroline (phen, in RuRe2), 4,7-diphenyl-1,10-phenanthroline (DIP, in RuRe3), tpphz = tetrapyrido[3,2-a:2′,3′-c:3″,2″-h:2″‘,3″‘-j]phenazine), using tpphz as a bridging ligand to connect Ru(II) polypyridyl moiety and Re(I) tricarbonyl moiety were designed and synthesized. Cytotoxicity tests revealed that RuRe1–3 exhibited high phototoxicities against several cancer cell lines tested, with IC50 values ranging from 0.8 to 6.8 μM. Notably, RuRe2 exhibited the most significant increase in cytotoxicity against human prostate cancer (PC3) cells under light (450 nm) irradiation, with phototoxicity index (PI) value increasing by >112.3-fold. Further mechanistic studies of RuRe2 revealed that RuRe2-mediated PDT could induce tumor cell apoptosis through the mitochondrial pathway. Moreover, RuRe2-mediated PDT could inhibit PC3 cell scratch healing and reduce the expression levels of matrix metalloproteinases 2 (MMP-2), matrix metalloproteinases 9 (MMP-9) and vascular endothelial growth factor receptor VEGFR2. Finally, angiogenic activity assays performed in human umbilical vein endothelial cells (HUVECs) showed that RuRe2 exerted an anti-angiogenesis effect. Our study demonstrated that RuRe1–3 were promising PDT antitumor agents with potential anti-metastatic and anti-angiogenic activities.