Aescin-induced reactive oxygen species play a pro-survival role in human cancer cells via ATM/AMPK/ULK1-mediated autophagy.

Aescin, a natural mixture of triterpene saponins, has been reported to exert anticancer effect. Recent studies show that aescin increases intracellular reactive oxygen species (ROS) levels. However, whether the increased ROS play a role in the anticancer action of aescin remains to be explored. In this study, we demonstrated that aescin (20-80 µg/mL) dose-dependently induced apoptosis and activated mammalian target of rapamycin (mTOR)-independent autophagy in human hepatocellular carcinoma HepG2 cells and colon carcinoma HCT 116 cells. The activation of autophagy favored cancer cell survival in response to aescin, as suppression of autophagy with ATG5 siRNAs or 3-methyladenine (3-MA), a selective inhibitor of autophagy, promoted aescin-induced apoptosis in vitro, and significantly enhanced the anticancer effect of aescin in vivo. Meanwhile, aescin dose-dependently elevated intracellular ROS levels and activated Ataxia-telangiectasia mutated kinase/AMP-activated protein kinase/UNC-51-like kinase-1 (ATM/AMPK/ULK1) pathway. The ROS and ATM/AMPK/ULK1 pathway were upstream modulators of the aescin-induced autophagy, as N-acetyl-L-cysteine (NAC) or ATM kinase inhibitor (KU-55933) remarkably suppressed aescin-induced autophagy and consequently promoted aescin-induced apoptosis, whereas overexpression of ATG5 partly attenuated NAC-induced enhancement in aescin-induced apoptosis. In conclusion, this study provides new insights into the roles of aescin-mediated oxidative stress and autophagy in cancer cell survival. Our results suggest that combined administration of the antioxidants or autophagic inhibitors with aescin might be a potential strategy to enhance the anticancer effect of aescin.

Downregulation of MACC1 inhibits the viability, invasion and migration and induces apoptosis in esophageal carcinoma cells through the phosphatase and tensin homolog/phosphoinositide 3-kinase/protein kinase B signaling pathway.

As an oncogene, MACC1 serves an important function in cancer progression and metastasis. However, the effect of MACC1 in esophageal carcinoma (EC) remains to be fully understood. The present study assessed the association between MACC1 expression and the progression of EC cells. A small interfering (si)RNA was delivered into EC cells to downregulate MACC1 expression. The MTT assay demonstrated that EC cell viability was reduced by siRNA-MACC1. Decreasing MACC1 expression increased the apoptotic rate of EC cells compared with control cells. Transwell and Matrigel assays demonstrated that EC cell migration and invasion, respectively, were downregulated by siRNA-MACC1. Furthermore, knocking down MACC1 suppressed the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway by upregulating the expression of phosphatase and tensin homolog (PTEN), a tumor suppressor. The results of the present study revealed that MACC1 expression affected cellular functions of the EC cells through the PTEN/PI3K/Akt signaling pathway. Therefore, MACC1 may potentially serve as a novel biomarker and therapeutic target for EC.