Acetyl-macrocalin B suppresses tumor growth in esophageal squamous cell carcinoma and exhibits synergistic anti-cancer effects with the Chk1/2 inhibitor AZD7762.

Natural products derived from herbal medicines have become a major focus of anti-cancer drug discovery studies. Acetyl-macrocalin B (A-macB) is an ent-diterpenoid isolated from Isodon silvatica. This study aimed to examine the effect and molecular action of A-macB in esophageal squamous cell carcinoma (ESCC) and explore possible drug synergistic modalities. A-macB induced cellular reactive oxygen species (ROS) generation, initiated the p38 mitogen-activated protein kinase (MAPK) signaling pathway, and triggered the caspase-9-dependent apoptosis cascade in ESCC cells. The ROS scavenger N-acetylcysteine (NAC) and the specific p38 inhibitor SB203580 reversed the effects of A-macB on the p38 network and thus rescued ESCC cells from apoptosis. The cellular ROS increase was at least partially due to the suppression of glutathione-S-transferase P1 (GSTP1) by A-macB. A-macB also upregulated the Chk1/Chk2-Cdc25C/Cdc2/Cyclin B1 axis to induce G2/M phase arrest. The cell growth inhibition induced by A-macB was further enhanced by AZD7762, a specific Chk1/Chk2 inhibitor, with a combination index (CI) of <1. Moreover, A-macB efficiently suppressed xenograft growth without inducing significant toxicity, and AZD7762 potentiated the effects of A-macB in the suppression of tumor growth in vivo. Taken together, A-macB is a promising lead compound for ESCC and exerts synergistic anti-cancer effects with AZD7762.

Wang JN ，Che Y ，Yuan ZY ，Lu ZL ，Li Y ，Zhang ZR ，Li N ，Li RD ，Wan J ，Sun HD ，Sun N ，Puno PT ，He J ... -  《-》

Acetyl-macrocalin B, an ent-kaurane diterpenoid, initiates apoptosis through the ROS-p38-caspase 9-dependent pathway and induces G2/M phase arrest via the Chk1/2-Cdc25C-Cdc2/cyclin B axis in non-small cell lung cancer.

Wang JN ，Zhang ZR ，Che Y ，Yuan ZY ，Lu ZL ，Li Y ，Li N ，Wan J ，Sun HD ，Sun N ，Puno PT ，He J ... -  《-》

Longikaurin A, a natural ent-kaurane, induces G2/M phase arrest via downregulation of Skp2 and apoptosis induction through ROS/JNK/c-Jun pathway in hepatocellular carcinoma cells.

Liao YJ ，Bai HY ，Li ZH ，Zou J ，Chen JW ，Zheng F ，Zhang JX ，Mai SJ ，Zeng MS ，Sun HD ，Pu JX ，Xie D ... -  《Cell Death & Disease》

The 3-deoxysappanchalcone induces ROS-mediated apoptosis and cell cycle arrest via JNK/p38 MAPKs signaling pathway in human esophageal cancer cells.

The 3-deoxysappanchalcone (3-DSC), a chemical separated from Caesalpinia sappan L, has been substantiated to display anti-inflammatory, anti-influenza, and anti-allergy activities according to previous studies. However, the underlying mechanisms of action on esophageal cancer remain unknown. The present research aims to survey the action mechanisms of 3-DSC in esophageal squamous cell carcinoma (ESCC) cells in vitro. Evaluation of cytotoxicity was determined by MTT tetrazolium salt assay and soft agar assay. Cell cycle distribution, apoptosis induction, reactive oxygen species (ROS) generation, mitochondrial membrane potential (MMP), and multi-caspases activity were appreciated by Muse™ Cell Analyzer. The expressions of cell cycle- and apoptosis-related proteins were presented using Western blotting. 3-DSC blocked cell growth and colony formation ability in a concentration-dependent manner and invoked apoptosis, G2/M cell cycle arrest, ROS production, MMP depolarization, and multi-caspase activity. Furthermore, Western blotting results demonstrated that 3-DSC upregulated the expression of phospho (p)-c-jun NH2-terminal kinases (JNK), p-p38, cell cycle regulators, pro-apoptotic proteins, and endoplasmic reticulum (ER) stress-related proteins whereas downregulated the levels of anti-apoptotic proteins and cell cycle promoters. The effects of 3-DSC on ROS induction were counteracted by pretreatment with N-acetyl-L-cysteine (NAC). Also, our results indicated that p38 (SB203580) and JNK (SP600125) inhibitor slightly inhibited 3-DSC-induced apoptosis. These results showed that 3-DSC-related G2/M phase cell cycle arrest and apoptosis by JNK/p38 MAPK signaling pathway in ESCC cells were mediated by ROS. ROS generation by 3-DSC in cancer cells could be an attractive strategy for apoptosis of cancer cells by inducing cell cycle arrest, ER stress, MMP loss, multi-caspase activity, and JNK/p38 MAPK pathway. Our findings suggest that 3-DSC is a promising novel therapeutic candidate for both prevention and treatment of esophageal cancer.

Kwak AW ，Lee MJ ，Lee MH ，Yoon G ，Cho SS ，Chae JI ，Shim JH ... -  《-》

OP16, a novel ent-kaurene diterpenoid, potentiates the antitumor effect of rapamycin by inhibiting rapamycin-induced feedback activation of Akt signaling in esophageal squamous cell carcinoma.

Hyperactivation of mTOR signaling pathway has been viewed as a significant molecular pathogenesis of cancer. However, inhibition of mTOR by rapamycin and its analogs could induce numerous negative feedback loops to attenuate their therapeutic efficacy. As a traditional Chinese herbal medicine, Rabdosia rubescens has been used to treat esophageal squamous cell carcinoma (ESCC) for hundreds of years, and its major effective component is oridonin. Here we reported that OP16, a novel analog of oridonin, showed potent inhibition of cell proliferation and Akt phosphorylation in ESCC cells. The combination of OP16 and rapamycin possesses synergistic anti-proliferative and pro-apoptotic effects both in ESCC cells and ESCC xenografts, and no obvious adverse effect was observed in vivo. Mechanistic analysis revealed that OP16 could inhibit rapamycin-induced Akt activation through the p70S6K-mediated negative feedback loops, and the combination of OP16 and rapamycin was more effective in activating caspase-dependent apoptotic signaling cascade. This study supports the combined use of OP16 with rapamycin as a feasible and effective therapeutic approach for future treatment of ESCC.

Peng KZ ，Ke Y ，Zhao Q ，Tian F ，Liu HM ，Hou G ，Lu Z ... -  《-》