ABSTRACT
Imbalance of redox homeostasis may be responsible for the resistance of cancer to chemotherapy. Currently, increasing studies demonstrated that vitamin K3 (VK3), which promoted the production of ROS, had potential to be developed as an anti-tumor agent. We found SKOV3/DDP cells with high levels of p62 were insensitive to VK3 compared with SKOV3 cells. Furthermore, Nrf2 downstream antioxidant genes such as HO-1(heme oxygenase 1) and NQO1 (NAD (P) H: quinone oxidoreductase 1) were upregulated in SKOV3/DDP cells with VK3 treatment, which indicated VK3 activated Nrf2 signaling in SKOV3/DDP cells. Moreover, co-localization of p62 and Keap1 was also observed. Suppression of p62 expression increased the apoptosis induced by VK3, and the expression of Nrf2, HO-1 and NQO1 were all downregulated in SKOV3/DDP cells. Our results suggested that overexpressed p62 may protect cells from oxidative damage caused by VK3 through activating Keap1/Nrf2 signaling in ovarian cancer.
ABSTRACT
SKOV3/DDP human ovarian cancer cells have been shown to be resistant to cisplatin. Although the BH3 mimetic S1 induces cell death in several types of tumor cells, it is unclear whether it induces death in drug-resistant cells. Herein, we found that S1 induced endoplasmic reticulum (ER) stress-associated apoptosis in both SKOV3 and SKOV3/DDP cells. S1 activated autophagy at early time points in SKOV3/DDP cells, and inhibition of autophagy increased ER stress-associated apoptosis. Collectively, our data indicate that autophagy plays a protective role, but it cannot protect against S1-induced cell death in cisplatin-resistant SKOV3/DDP cells.
Subject(s)
Biomimetics , Drug Resistance, Neoplasm/drug effects , Endoplasmic Reticulum Stress/drug effects , Ovarian Neoplasms/drug therapy , Proto-Oncogene Proteins c-bcl-2/pharmacology , Apoptosis/drug effects , Autophagy/drug effects , Cell Line, Tumor , Cisplatin/administration & dosage , Female , Humans , Mitochondrial Membrane Transport Proteins , Ovarian Neoplasms/genetics , Ovarian Neoplasms/pathology , Proto-Oncogene Proteins c-bcl-2/chemistryABSTRACT
Previous results showed that a novel BH3 mimetic S1 could induce cell death in a wide range of cancer types in vitro through Bax/Bak-dependent apoptosis. We demonstrated that in addition to mitochondrial pathway apoptosis, endoplasmic reticulum (ER) stress-associated apoptosis was also induced by S1. Moreover, S1 can induce autophagy in U251 cells, which may occur through ER stress and disruption of the association of Bcl-2 and Beclin 1. Inhibition of autophagy by the autophagic inhibitors 3-methyladenine (3-MA) or chloroquine (CQ) increased S1-induced apoptosis. In conclusion, autophagy plays an important role in S1-induced U251 cell death.