Elucidation of mode of anticancerous activity of metal guanidinobenzimidazoles: A computational and experimental screening

DNA-binding agents often exhibits dual behavior of simultaneous binding with protein associated with cancerous cell development pathways. This simultaneous protein binding if contributed to malfunctioning of pro-apoptotic proteins will reduce anticancerous potential of drugs. The elucidation of binding target for anticancerous agent can give an insight into the cancer cell apoptotic pathway. Therefore, anticancerous Zn(II) and Ni(II) complexes of 2-guanidinobenzimidazole (2GBz) were subjected to DNA-binding mode assay along with protein-binding interference assay. The stoichiometry Zn-2GBz and Ni-2GBz were determined through density functional theory (DFT) and UV–Vis spectroscopy, followed by structural verification by X-ray crystallography. The 2GBz and Ni-2GBz were found to bind with grooves of DNA while groove binding of Zn-2GBz induced unwinding of DNA through interactive pi-stacking. Binding constant revealed the M-2GBz to be a strong binder of DNA molecule with the effect of enhanced cell killing potential of M-2GBz against MCF-7 cell lines. Protein-binding assay revealed that despite of significant interaction of M-2GBz with chick serum albumin, DNA binding was not altered by simultaneous protein binding. The most potent Zn-2GBz was found to be sphingosine 1 kinase 2 (SPhK2) which can be a cause of enhanced cancer cell apoptosis with lesser normal cell apoptosis than standard fluorouracil in MCF-7 cell lines. Co-administered Zn-2GBz increased cancer cell sensitivity towards fluorouracil as potent anticancerous agent.