Melatonin‐induced increase in sensitivity of human hepatocellular carcinoma cells to sorafenib is associated with reactive oxygen species production and mitophagy

Abstract

Effects of sorafenib in hepatocellular carcinoma (HCC) are frequently transient due to tumor-acquired resistance, a phenotype that could be targeted by other molecules to reduce this adaptive response. Because melatonin is known to exert antitumor effects in HCC cells, this study investigated whether and how melatonin reduces resistance to sorafenib. Susceptibility to sorafenib (10 nM to 50 μM) in the presence of melatonin (1 and 2 mM) was assessed in HCC cell lines HepG2, HuH7 and Hep3B. Cell viability was reduced by sorafenib from 1 μM in HepG2 or HuH7 cells, and 2.5 μM in Hep3B cells. Co-administration of melatonin and sorafenib exhibited a synergistic cytotoxic effect on HepG2 and HuH7 cells, while Hep3B cells displayed susceptibility to doses of sorafenib that had no effect when administrated alone. Co-administration of 2.5 μM sorafenib and 1 mM melatonin induced apoptosis in Hep3B cells, increasing PARP hydrolysis and BAX expression. We also observed an early colocalization of mitochondria with lysosomes, correlating with the expression of mitophagy markers PINK1 and Parkin and a reduction of mitofusin-2 and mtDNA compared with sorafenib administration alone. Moreover, increased reactive oxygen species production and mitochondrial membrane depolarization were elicited by drug combination, suggesting their contribution to mitophagy induction. Interestingly, Parkin silencing by siRNA to impair mitophagy significantly reduced cell killing, PARP cleavage and BAX expression. These results demonstrate that the pro-oxidant capacity of melatonin and its impact on mitochondria stability and turnover via mitophagy increase sensitivity to the cytotoxic effect of sorafenib.

Melatonin promotes sorafenib‐induced apoptosis through synergistic activation of JNK/c‐jun pathway in human hepatocellular carcinoma

“…The present study confirms that the activated JNK/c‐jun pathway is responsible for the activation of caspase‐3. It is also demonstrated that the combination of melatonin and sorafenib induces increased apoptosis and reduced viability through ROS overproduction and mitochondrial membrane depolarization . Furthermore, ROS/JNK/c‐Jun signaling pathway was reported to be involved in regulating the apoptosis of HCC cells .…”

Melatonin in macrophage biology: Current understanding and future perspectives

“…Likewise, the mitophagy level is decreased in M1 macrophages in vivo . Indeed, melatonin has been reported to elevate the mitophagy level in other systems . However, the exact mechanisms whereby melatonin targets mitophagy remain to be identified.…”

Melatonin: A Mitochondrial Targeting Molecule Involving Mitochondrial Protection and Dynamics

“…This speculation is supported by the observations summarized herein that melatonin indeed targets the process of mitophagy. Melatonin mainly enhances mitophagy and improves mitochondrial biogenesis [203,204,205]. The exact mechanisms by which melatonin targets mitophagy are not currently available.…”