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.
The asymptomatic properties and high treatment resistance of ovarian cancer result in poor treatment outcomes and high mortality rates. Although the fundamental chemotherapy provides promising anticancer activities, it is associated with severe side effects. The derivative of phenothiazine, namely, 10H-3,6-diazaphenothiazine (PTZ), was synthesized and reported with ideal anticancer effects in a previous paper. In this study, detailed anticancer properties of PTZ was examined on A2780 ovarian cancer cells by investigating the cytotoxicity profiles, mechanism of apoptosis, and cell invasion. Research outcomes revealed PTZ-induced dose-dependent inhibition on A2780 cancer cells (IC50 =0.62 µM), with significant less cytotoxicity toward HEK293 normal kidney cells and H9C2 normal heart cells. Generation of reactive oxygen species (ROS) and polarization of mitochondrial membrane potential (ΔΨm) suggests PTZ-induced cell death through oxidative damage. The RT2 Profiler PCR Array on apoptosis pathway demonstrated PTZ-induced apoptosis via intrinsic (mitochondria-dependent) and extrinsic (cell death receptor-dependent) pathway. Inhibition of NF-κB and subsequent inhibition of (BIRC6-XIAP) complex activities reduced the invasion rate of A2780 cancer cells penetrating through the Matrigel™ Invasion Chamber. Lastly, the cell cycle analysis hypothesizes that the compound is cytostatic and significantly arrests cell proliferation at G2/M phase. Hence, the exploration of the underlying anticancer mechanism of PTZ suggested its usage as promising chemotherapeutic agent.