salvianolic-acid-B and 3-methyladenine

Salvianolic Acid B (Sal B), an active compound extracted from the Chinese herb Salvia miltiorrhiza, is attracting more and more attention due to its biological activities, including antioxidant, anticoagulant and antitumor effects. However, autophagy induction in cancer cells by Sal B has never been recognized. In this study, we demonstrated that Sal B induced cell death and triggered autophagy in HCT116 and HT29 cells in a dose-dependent manner. Specific inhibition of autophagy by 3-MA or shRNA targeting Atg5 rescued Sal B-induced cell death in vitro and in vivo, suggesting that Sal B-induced autophagy may play a pro-death role and contribute to the cell death of colorectal cancer cell lines. Furthermore, AKT/mTOR signaling pathway was demonstrated to be a critical mediator in regulating Sal B-induced cell death. Overexpression of AKT by the transfection with AKT plasmid or pretreatment with insulin decreased Sal B-induced autophagy and cell death. Inversely, inhibition of AKT by LY294002 treatment markedly enhanced Sal B-induced autophagy and cell death. Taken together, our results demonstrate, for the first time, that Sal B is a novel autophagy inducer and exerts its antitumor activity as a single agent in colorectal cancer cells through the suppression of AKT/mTOR pathway.

Topics: Adenine; Animals; Antineoplastic Agents; Autophagosomes; Autophagy; Autophagy-Related Protein 5; Benzofurans; Chromones; Colorectal Neoplasms; Drugs, Chinese Herbal; Female; HCT116 Cells; HT29 Cells; Humans; Mice; Mice, Inbred BALB C; Mice, Nude; Microscopy, Electron, Transmission; Microscopy, Fluorescence; Morpholines; Proto-Oncogene Proteins c-akt; RNA Interference; RNA, Small Interfering; Salvia miltiorrhiza; Signal Transduction; TOR Serine-Threonine Kinases; Xenograft Model Antitumor Assays

Chinese medicines are emerging as an attractive new generation of anticancer drugs. Here, we explored the impact of salvianolic acid B (Sal B), the major water-soluble compounds of Danshen, on apoptosis and autophagy of human hepatocellular carcinoma cells (HCC). We also investigated the related molecular mechanisms. We found that Sal B exhibits potent ability to inhibit HCC cells viability in a concentration-dependent manner, and to induce apoptosis via the mitochondrial apoptosis pathway. Additionally, Sal B could also induce autophagy. Furthermore, pretreatment with the autophagy inhibitor chloroquine or 3-methyladenine showed the potential in attenuating the apoptosis rate induced by Sal B. Mechanistically, Sal B treatment inhibited the AKT/mTOR signaling cascade in vitro. Overexpression of AKT abolished the effects of Sal B on HCC cells, suggesting a critical role of the AKT/mTOR signaling pathway in Sal B-induced biological effects. Our results indicated that the mitochondrial pathway was involved in Sal B-induced apoptosis of HCC cells. Moreover, the AKT/mTOR signaling pathway was involved in Sal B-induced autophagy, which promoted apoptosis. This study may provide a promising strategy for using Sal B as a chemotherapeutic agent for patients with HCC.

Topics: Adenine; Antineoplastic Agents; Apoptosis; Autophagy; Beclin-1; Benzofurans; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Proliferation; Chloroquine; Drugs, Chinese Herbal; Humans; Liver Neoplasms; Mitochondria; Proto-Oncogene Proteins c-akt; RNA Interference; RNA, Small Interfering; Salvia miltiorrhiza; Signal Transduction; TOR Serine-Threonine Kinases