Tribenzyltin carboxylates complexes, namely tri(4-fluorobenzyl)tin[(N,N-diisopropylcarbamothioyl)sulfanyl]acetate (C1) and tribenzyltin isonicotinate (C9), have been reported to exhibit significant anticancer activity via the death receptor and mitochondrial apoptotic pathway. However, understanding their upstream mechanism remains crucial. This study utilized both in silico and in vitro approaches to elucidate their mechanism of action. Molecular docking analysis indicated that C1 and C9 interacted with the minor groove of DNA. Fluorescence displacement assays confirmed their interaction with DNA through the minor groove. In enzyme inhibition assays, C1 showed significant inhibition of thioredoxin reductase (TrxR) activity, while C9 exhibited a dose-dependent effect, consistent with their docking affinities (- 4.1 and - 4.3 kcal/mol, respectively). Both compounds strongly inhibited human DNA topoisomerase I (TopI), supported by docking energies of - 7.0 and - 6.6 kcal/mol, respectively. The nearly complete inhibition of TopI across all treatment groups highlights it as a key molecular target. Additionally, C1 and C9 bound to thymidylate synthase (TS) with docking energies of - 7.2 and - 7.7 kcal/mol, respectively, leading to a marked reduction in TS levels. Molecular dynamics simulations of the TopI, TS, and TrxR complexes revealed that both C1 and C9 maintained stable binding within their respective active sites throughout the 100 ns trajectories. In summary, C1 and C9 primarily target the DNA minor groove and inhibit key enzymes such as TopI, TrxR, and TS, shedding light on their intricate mechanisms of action. These findings underscore the potential of C1 and C9 as promising multitarget metal-based anticancer agents.
Early development of liver cancer is usually asymptomatic. The overall survival rate of patients is relatively low due to late diagnosis, despite hepatocellular carcinoma being a common diagnosis. The high mortality rate of liver cancer was due to its overactivated cellular mitochondrial activities, namely thioredoxin reductase enzymatic activities and its downstream activation of nuclear factor kappa B (NF-κB) signaling pathways for cancer cell migration. Our previous study on this candidate compound on A2780 ovarian cancer cells and MCF-7 breast cancer cells, through modulation of cell-cycle checkpoints and respective targeted apoptosis pathways. The current study used HepG2 hepatocellular carcinoma cell lines as a representative in vitro liver cancer cell model. The half maximal inhibitory concentration (IC50) value was obtained via incubation of PTZ compound for 24 h yield of 37.03 μM, whereby it was three-fold more potent than the standard control tested, cisplatin (109.23 μM). The subsequent application of IC50 dosage of PTZ onto HepG2 cells illustrated a growth-static effect via activation of S-phase cell-cycle checkpoints, immediately followed by regulation of apoptosis. Increased cellular concentration of reactive oxygen species eventually generated oxidative damages on mitochondria, hence resulting in the release of cytochrome c protein and suppression of TrxR enzymatic activity, in conjunction with the suppression on invasion of cancer cells via Matrigel invasion chamber. In conclusion, PTZ was hypothesized to act effectively on mitochondria of HepG2 cells; hence it should proceed into detailed drug targeting mechanism research.