Therapeutic targeting of autophagy in cancer. Part II: pharmacological modulation of treatment-induced autophagy

Cucurbitacin B induces DNA damage and autophagy mediated by reactive oxygen species (ROS) in MCF-7 breast cancer cells

Cucurbitacin B (Cuc B), a natural compound extracted from cucurbitaceous plants, demonstrated potent anticancer activities, while the underlying mechanisms remain unclear. We investigated the anticancer effect of Cuc B on MCF-7 breast cancer cells. Cuc B drastically decreased cell viability in a concentration-dependent manner. Cuc B treatment caused DNA damage, as shown by long tails in the comet assay and increased γH2AX protein expression. Immunofluorescence staining showed that Cuc B treatment induced nuclear γH2AX foci. Cuc B activated DNA damage pathways by phosphorylation of ATM/ATR [two large phosphatidylinositol-3-kinase-like kinase family (PIKKs) members]. Furthermore, it also induced autophagy, as evidenced by monodansylcadaverine (MDC) staining and autophagic protein expression. In addition, Cuc B treatment led to increased reactive oxygen species (ROS) formation, which was inhibited by N-acetyl-L-cysteine (NAC) pretreatment. NAC pretreatment inhibited Cuc-B-induced DNA damage and autophagy. Taken together, these results suggest that ROS-mediated Cuc-B-induced DNA damage and autophagy in MCF-7 cells, which provides new insights into the anticancer molecular mechanism of Cuc B.

The multi-targeted tyrosine kinase inhibitor vandetanib plays a bifunctional role in non-small cell lung cancer cells

Vandetanib, a multikinase inhibitor, is a target of drug treatments for non-small cell lung cancer (NSCLC). However, phase II and III clinical trials have not conclusively demonstrated the curative effects of vandetanib for NSCLC, and the reasons for this are unknown. In the present study, we use the NSCLC cell line Calu-6 as a model to determine the cellular and biological effects of vandetanib. Our results demonstrate that vandetanib impairs Calu-6 cell migration and invasion. We find that vandetanib can directly inhibit RET activity, which influences the Rho-JNK pathway. Overexpression of a constitutively active Rho GTPase antagonizes the inhibitory effects of vandetanib on Calu-6 cells invasion and JNK pathway activation. In addition, vandetanib induces autophagy by increasing the level of reactive oxygen species (ROS) in Calu-6 cells, and blockade of autophagy or ROS effectively enhances the cell death effect of vandetanib. In this study, we find vandetanib is of a double effect in some NSCLC cells, presenting new possibilities for the pharmacological treatment of NSCLC and introducing a novel role for vandetanib in treatment options.

Molecular mechanisms of etoposide

Etoposide derives from podophyllotoxin, a toxin found in the American Mayapple. It was first synthesized in 1966 and approved for cancer therapy in 1983 by the U.S. Food and Drug Administration (Hande, 1998[25]). Starting from 1980s several studies demonstrated that etoposide targets DNA topoisomerase II activities thus leading to the production of DNA breaks and eliciting a response that affects several aspects of cell metabolisms. In this review we will focus on molecular mechanisms that account for the biological effect of etoposide.

Targeting autophagy for therapy of gastric cancer

Gastric cancer is one of the most common malignant neoplasms. Surgery represents the main approach for this disease. Notwithstanding the advances in surgical techniques, there has been still a minimal improvement in overall survival with a significant increase in relapse rates. Although the development of new drugs has significantly improved the effectiveness of chemotherapy, the prognosis of patients with unresectable or metastatic gastric carcinoma remains poor. Therefore, it is necessary to find some new ways against gastric carcinogenesis. It has been shown that autophagy plays a dual role in the transformation and progression of gastric cancer; activation and induction of autophagy can lead to gastric carcinogenesis. Recently, several agents targeting autophagy molecules in gastric carcinogenesis have been investigated. This article reviews the regulation of autophagy with inhibitors or inducers to treat gastric cancer, and discusses how they regulate autophagy as a targeted therapy for gastric cancer.