DNA damage, cell cycle perturbation and cell death by naphthalene diimide derivative in gastric cancer cells.

Stomach cancer causes the third-highest cancer-related deaths worldwide. Limited availability of anticancer measures with higher efficiency and low unwanted toxicities necessitates the development of better cancer chemotherapeutics. Naphthalene diimide (NDI) derivatives have gained significant attention owing to their excellent anticancer potential. We evaluated the anticancer properties of NDI derivatives, 1a and 2a in cancer cell lines and found that 1a showed higher efficacy as compared to 2a exhibiting a remarkable difference in activity upon single atom substitution of C with N. Particularly, NDI 1a showed potent inhibitory activity against gastric cancer cell line AGS with IC50 of 2.0 µM. NDI 1a induced remarkable morphological changes and reduced clonogenicity as well as the migratory ability of AGS cells. The reduction in AGS cell migration was mediated through inhibition of Tyr397 p-FAK dephosphorylation at focal adhesion points leading to enhanced attachment of cells at contact points. NDI 1a caused extensive DNA double-strand-breaks (DSBs) leading to activation of p53 and its transcriptional target p21. Reduced nuclear BRCA1 but enhanced nuclear p53BP1 foci formation upon 1a treatment suggests that DNA DSB repair is mediated through error-prone NHEJ which led to the accumulation of extensive DNA damage. Combinatorial effects mediated by interactions of 1a with double-stranded DNA through minor groove binding as well as induction of intracellular ROS exacerbated the loss of genomic integrity induced by 1a. NDI 1a mediated DNA damage-induced S phase arrest; however, cells experiencing extensive and irreparable DNA damage underwent mitochondrial apoptosis through downregulation of anti-apoptotic protein p21. Furthermore, proliferation inhibitory activity of 1a is also attributed to inhibition of ß-catenin/c-Myc axis in AGS cells with constitutively active ß-catenin pathway. In vivo toxicity analysis of 1a revealed minimal systemic toxicity suggesting that compound 1a is a safe and potential candidate for the development of gastric cancer chemotherapeutics.