Exploring the Antitumor Efficacy of N-Heterocyclic Nitrilotriacetate Oxidovanadium(IV) Salts on Prostate and Breast Cancer Cells

The crystal structures of two newly synthesized nitrilotriacetate oxidovanadium(IV) salts, namely [QH][VO(nta)(H₂O)](H₂O)₂ (I) and [(acr)H][VO(nta)(H₂O)](H₂O)₂ (II), were determined. Additionally, the cytotoxic effects of four N-heterocyclic nitrilotriacetate oxidovanadium(IV) salts—1,10-phenanthrolinium, [(phen)H][VO(nta)(H₂O)](H₂O)_0.5 (III), 2,2′-bipyridinium [(bpy)H][VO(nta)(H₂O)](H₂O) (IV), and two newly synthesized compounds (I) and (II)—were evaluated against prostate cancer (PC3) and breast cancer (MCF-7) cells. All the compounds exhibited strong cytotoxic effects on cancer cells and normal cells (HaCaT human keratinocytes). The structure–activity relationship analysis revealed that the number and arrangement of conjugated aromatic rings in the counterion had an impact on the antitumor effect. The compound (III), the 1,10-phenanthrolinium analogue, exhibited the greatest activity, whereas the acridinium salt (II), with a different arrangement of three conjugated aromatic rings, showed the lowest toxicity. The increased concentrations of the compounds resulted in alterations to the cell cycle distribution with different effects in MCF-7 and PC3 cells. In MCF-7 cells, compounds I and II were observed to block the G₂/M phase, while compounds III and IV were found to arrest the cell cycle in the G₀/G₁ phase. In PC3 cells, all compounds increased the rates of cells in the G₀/G₁ phase.