Eukaryotes initiate autophagy when facing environmental changes such as a lack of external nutrients. However, the mechanisms of autophagy initiation are still not fully elucidated. Here, we showed that deacetylation of ATG4B plays a key role in starvation-induced autophagy initiation. Specifically, we demonstrated that ATG4B is activated during starvation through deacetylation at K39 by the deacetylase SIRT2. Moreover, starvation triggers SIRT2 dephosphorylation and activation in a cyclin E/CDK2 suppression–dependent manner. Meanwhile, starvation down-regulates p300, leading to a decrease in ATG4B acetylation at K39. K39 deacetylation also enhances the interaction of ATG4B with pro-LC3, which promotes LC3-II formation. Furthermore, an in vivo experiment using Sirt2 knockout mice also confirmed that SIRT2-mediated ATG4B deacetylation at K39 promotes starvation-induced autophagy initiation. In summary, this study reveals an acetylation-dependent regulatory mechanism that controls the role of ATG4B in autophagy initiation in response to nutritional deficiency.
Autophagy is closely related to the growth and drug resistance of cancer cells, and autophagy related 4B (ATG4B) performs a crucial role in the process of autophagy. The long non-coding RNA (lncRNA) colorectal neoplasia differentially expressed (CRNDE) promotes the progression of hepatocellular carcinoma (HCC), but it is unclear whether the tumor-promoting effect of CRNDE is associated with the regulation of ATG4B and autophagy. Herein, we for the first time demonstrated that CRNDE triggered autophagy via upregulating ATG4B in HCC cells. Mechanistically, CRNDE enhanced the stability of ATG4B mRNA by sequestrating miR-543, leading to the elevation of ATG4B and autophagy in HCC cells. Moreover, sorafenib induced CRNDE and ATG4B as well as autophagy in HCC cells. Knockdown of CRNDE sensitized HCC cells to sorafenib in vitro and in vivo. Collectively, these results reveal that CRNDE drives ATG4B-mediated autophagy, which attenuates the sensitivity of sorafenib in HCC cells, suggesting that the pathway CRNDE/ATG4B/autophagy may be a novel target to develop sensitizing measures of sorafenib in HCC treatment.
Sorafenib is the first-line drug used in the treatment of liver cancer; however, drug resistance seriously limits the clinical response to sorafenib. The present study investigated the molecular mechanisms of sorafenib resistance in liver cancer cells. The data indicated that forkhead box M1 (FoxM1) was significantly overexpressed in sorafenib-resistant cells, at the mRNA and protein levels. Knockdown of FoxM1 rendered drug-tolerant cells sensitive to sorafenib. Furthermore, FoxM1 was upregulated at the transcriptional level. Overexpression of c-jun was associated with the upregulation of FoxM1. The results of a reporter gene assay, electrophoretic mobility shift assay and chromatin immunoprecipitation assay demonstrated that there is an activator protein-1 (AP1) binding site in the promoter of FoxM1, located at-608 to-618. Knockdown of c-jun significantly decreased the levels of FoxM1, accompanied by enhanced cell sensitivity to sorafenib. Furthermore, the activation of AKT contributed to the upregulation of c-jun and FoxM1. Inhibition of AKT using BEZ-235 markedly suppressed the upregulation of c-jun and FoxM1, and increased the sensitivity of drug-resistant cells to sorafenib in vitro and in vivo. The data indicated that the activation of the AKT/AP1/FoxM1 signaling axis is an important determinant of sorafenib tolerance.
Vascular endothelial growth factor receptor (VEGFR) is an important receptor tyrosine kinase (RTK) in the induction of angiogenesis. Abnormal activation of VEGFR leads to several disorders including cancer. Nowadays, inhibition of VEGFR kinase has been one of the most powerful clinical strategies in cancer treatment and great efforts to design and synthesize small molecular VEGFR inhibitors for cancer research have been made in recent years. This review highlights the major progress and development of them, including their structure and pharmacophore features, biological activities and structure-activity relationships (SAR). Special attentions are paid to the compounds available in market or in advanced clinical stages.
Aim: Liver cancer is one of the most common malignancies and has a high recurrence rate. However, current treatment strategies do not achieve satisfactory outcomes in the clinic. To explore a new strategy to enhance the effectiveness of chemotherapy in liver cancer, we investigated whether dichloroacetate (DCA) could enhance the sensitivity of liver cancer cells to pirarubicin (THP).Methods: Liver cancer cells were treated with DCA alone, THP alone, or DCA and THP combined. Cell viability was determined by the CCK-8 assay. Cell apoptosis was analyzed by flow cytometer. Reactive oxygen species (ROS) were detected using a CM-H2DCFDA fluorescence probe. Protein levels were identified by immunoblotting. Results:The results revealed that DCA significantly enhanced the antitumor effect of THP in liver cancer cells. Changes in morphology and adherence ability were observed, as well as decreased cell viability. The results of flow cytometry showed that the combination of THP and DCA significantly increased apoptosis of liver cancer cells. Moreover, compared with THP alone, combination treatment with DCA significantly increased THP-triggered ROS generation in liver cancer cells. The antioxidant N-acetyl-L-cysteine reversed the synergistic effect of DCA and THP on ROS generation, cell viability and apoptosis. Furthermore, phosphorylation of c-Jun N-terminal kinase
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.