Targeting nasopharyngeal carcinoma by artesunate through inhibiting Akt/mTOR and inducing oxidative stress

Abstract

Drug repurposing has become an alternative therapeutic strategy for cancer treatment given the known pharmacokinetics and toxicity. The inhibitory effects of artesunate have been reported in various cancers. In this work, we investigated the effects of artesunate in nasopharyngeal carcinoma (NPC). We demonstrate that artesunate significantly inhibits proliferation via arresting NPC cells at G2/M phase. It also induces apoptosis through caspase-dependent and mitochondria-independent pathways in multiple NPC cell lines. The combination of artesunate and cisplatin is synergistic in targeting NPC cells in in vitro cellular culture system and in vivo xenograft tumor models. Artesunate inhibits phosphorylation of essential molecules involved in Akt/mTOR pathway in NPC cells, such as Akt, mTOR, and 4EBP1, and its inhibitory effects are partially abolished by overexpression of constitutively active Akt. In addition, artesunate also induces mitochondrial dysfunction and oxidative stress via inhibiting mitochondrial respiration, increasing levels of mitochondrial superoxide and cellular reactive oxygen species (ROS), leading to decreased ATP levels. Two ROS scavengers partially abolish the inhibitory effects of artesunate in NPC cells. These data suggest that both inhibition of Akt/mTOR pathway and induction of ROS are required for the action of artesunate in NPC cells. Our work demonstrates that artesunate is a potential candidate for NPC treatment. Our work also highlights the critical roles of Akt/mTOR pathway and mitochondrial function in NPC cells.

Artesunate-induced mitophagy alters cellular redox status

“…Lysosomes contain high levels of redox-active iron and iron-catalyzed lysosomal ROS production leads to mitochondrial outer membrane permeabilization and apoptosis in response to specific stimuli [23] . It is consistent with many studies [24] , [25] , [26] that ART treatment leads to mitochondrial ROS accumulation, disruption of mitochondrial membrane potential and induction of the intrinsic mitochondrial apoptosis. However, it remains unknown whether these damaged mitochondria could be degraded through mitophagy.…”

Markers of oxidative‐nitrosative stress induced by artesunate are followed by clastogenic and aneugenic effects and apoptosis in human lymphocytes

“…ARS has been found to induce ROS production and accumulation in different cancer cell lines, including the generation of O 2 − (Greenshields et al, ; Li et al, ; Roh et al, ; Wu, Zhang, Li, Yang, & Zhao, ; Yang et al, ). In contrast, ARS‐induced ROS production in control normal cells appears to be dependent on the cell type, once elevated ROS content was verified in certain kinds of cells whereas reduction or no alteration was observed in other cell types (Beccafico et al, ; Cheng et al, ).…”

“…In contrast, the mechanisms involved in programmed cell death triggered by ARS in normal control cells is considerably less known (Cheng et al, ). ARS was found to induce apoptotic cell death in several tumor cell lines in a caspase‐independent manner (Greenshields et al, ; Papanikolaou et al, ; Wang et al, ) and in a caspase‐dependent manner, via intrinsic (mitochondrial pathway) and extrinsic pathways (Kim, Lee, Kim, Sethi, & Ahn, ; Li et al, ; Pang et al, ; Qin et al, ; Zhang, Luo, Li, & Tan, ). In this study, an ARS‐induced increase of caspases 8 and 9 and cytochrome c expression may suggest that both the mitochondrial and death receptor apoptotic pathways are likely to be activated in non‐tumor cell death following ARS exposure.…”

“…ARS induced cell death of different cell types in vitro, including the Chinese hamster ovary cell line, human vascular endothelial cells and human lymphocytes (Cheng et al, ; Li et al, ; Mota et al, ). In addition, a number of cancer cell lines were observed to respond to ARS by decreasing cell viability and increasing cell death (Greenshields, Shepherd, & Hoskin, ; Li et al, ; Pang, Qin, Wu, Wang, & Chen, ; Roh, Kim, Jang, & Shin, ). Similarly, incubation with ARS led to oxidative DNA damage, induction of DNA double‐strand breaks and increase of micronuclei (MN) frequency in both cancer cell lines and normal cells, including human lymphocytes (Aquino et al, ; Aquino, Ferreira, & Luis, ; Berdelle, Nikolova, Quiros, Efferth, & Kaina, ; Li et al, ; Mota et al, ; Wang et al, ).…”

“…Both reactive oxygen species (ROS)-dependent and ROS-independent apoptosis were reported to occur after ARS exposure in several kinds of tumor cells (Ba et al, 2012;Greenshields et al, 2017;Pang et al, 2016;Qin et al, 2015). Likewise, both caspase-dependent and caspaseindependent mechanisms of apoptotic cell death were observed to happen in cancer cell lines subjected to ARS treatment (Greenshields et al, 2017;Ilamathi & Sivaramakrishnan, 2017;Li et al, 2017;Papanikolaou et al, 2014). Additionally, ARS triggers cell death mechanisms other than apoptosis, such as necrosis, autophagy, oncosis and ferroptosis, which might be coupled with elevated ROS production (Berdelle et al, 2011;Chen et al, 2014;Du, Zhang, Ma, & Ji, 2010;Eling, Reuter, Hazin, & Hamacher-brady, 2015;Greenshields et al, 2017;Roh et al, 2017).…”