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HMGB1-mediated autophagy attenuates gemcitabine-induced apoptosis in bladder cancer cells involving JNK and ERK activation.

ABSTRACT: High-mobility group box 1 (HMGB1) has been found to mediate autophagy during chemotherapy in several cancers. However, whether HMGB1plays a role in autophagy and chemoresistance in bladder cancer is elusive. In this report, HMGB1 expression was found to be increased in 30 primary bladder cancer tissue specimens compared to their matched adjacent non-tumor tissues. While gemcitabine induced apoptotic cell death, it also induced HMGB1 expression and autophagy in bladder cancer T24 and BIU-87 cells. Suppressing HMGB1 expression with siRNA strongly potentiated gemcitabine-induced apoptosis. HMGB1 siRNA or autophagy inhibitors suppressed gemcitabine-induced autophagy. Further, gemcitabine activated c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinase (ERK) and Bcl-2 phosphorylation, and blocking ERK and JNK inhibited autophagy and increased apoptosis in gemcitabine-treated cells. Interestingly, suppressing HMGB1 expression attenuated gemcitabine-induced ERK and JNK activation and Bcl-2 phosphorylation. Thus, our results suggest that while gemcitabine kills bladder cancer cells through apoptosis, a cytoprotective autophagy is also induced involving HMGB1-mediated JNK and ERK to counteract the cytotoxicity of gemcitabine, and intervention targeting this pathway may improve the anticancer efficacy of gemcitabine against bladder cancer.

SUBMITTER: Yin H

PROVIDER: S-EPMC5641078 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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HMGB1-mediated autophagy attenuates gemcitabine-induced apoptosis in bladder cancer cells involving JNK and ERK activation.

Yin Hubin H Yang Xiaoyu X Gu Wen W Liu Yan Y Li Xinyuan X Huang Xiaolong X Zhu Xin X Tao Yong Y Gou Xin X He Weiyang W

Oncotarget 20170511 42

High-mobility group box 1 (HMGB1) has been found to mediate autophagy during chemotherapy in several cancers. However, whether HMGB1plays a role in autophagy and chemoresistance in bladder cancer is elusive. In this report, HMGB1 expression was found to be increased in 30 primary bladder cancer tissue specimens compared to their matched adjacent non-tumor tissues. While gemcitabine induced apoptotic cell death, it also induced HMGB1 expression and autophagy in bladder cancer T24 and BIU-87 cells ...[more]

PMID: 29069735

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Project description:Chemotherapy-induced reduction in tumor load is a function of apoptotic cell death, orchestrated by intracellular caspases. However, the effectiveness of these therapies is compromised by mutations affecting specific genes, controlling and/or regulating apoptotic signaling. Therefore, it is desirable to identify novel pathways of cell death, which could function in tandem with or in the absence of efficient apoptotic machinery. In this regard, recent evidence supports the existence of a novel cell death pathway termed autophagy, which is activated upon growth factor deprivation or exposure to genotoxic compounds. The functional relevance of this pathway in terms of its ability to serve as a stress response or a truly death effector mechanism is still in question; however, reports indicate that autophagy is a specialized form of cell death under certain conditions.We report here the simultaneous induction of non-canonical autophagy and apoptosis in human cancer cells upon exposure to a small molecule compound that triggers intracellular hydrogen peroxide (H(2)O(2)) production. Whereas, silencing of beclin1 neither inhibited the hallmarks of autophagy nor the induction of cell death, Atg 7 or Ulk1 knockdown significantly abrogated drug-induced H(2)O(2)-mediated autophagy. Furthermore, we provide evidence that activated extracellular regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) are upstream effectors controlling both autophagy and apoptosis in response to elevated intracellular H(2)O(2). Interestingly, inhibition of JNK activity reversed the increase in Atg7 expression in this system, thus indicating that JNK may regulate autophagy by activating Atg7. Of note, the small molecule compound triggered autophagy and apoptosis in primary cells derived from patients with lymphoma, but not in non-transformed cells.Considering that loss of tumor suppressor beclin 1 is associated with neoplasia, the ability of this small molecule compound to engage both autophagic and apoptotic machineries via ROS production and subsequent activation of ERK and JNK could have potential translational implications.

Project description:Platycodin D, the main saponin isolated from Chinese herb Platycodonis Radix, exhibits anticancer activities against various cancer cell lines. Here we evaluated its anticancer action against human hepatocellular carcinoma cells in vitro and in vivo, and elucidated the relationship between platycodin D-induced apoptosis and autophagy.The viability of human hepatocellular carcinoma BEL-7402 cells was evaluated with MTT assay, and the apoptosis was examined using Annexin V/PI and Hoechst 33342 staining assays. Monodansylcadaverine (MDC) staining was used to label autophagic vacuoles. The proteins were detected using Western blot analysis. For studying its anticancer action in vivo, platycodin D (5 and 10 mg· kg(-1)·d(-1)) was intraperitoneally injected to BEL-7402-bearing mice for 21 days.Platycodin D (5-40 μmol/L) inhibited the cell proliferation in vitro with IC50 values of 37.70±3.99, 24.30±2.30 and 19.70±2.36 μmol/L at 24, 48 and 72 h, respectively. Platycodin D (5-20 μmol/L) dose-dependently increased BEL-7402 cell apoptosis, increased the Bax/Bcl-2 ratio and the levels of cleaved PARP and cleaved caspase-3, and decreased the level of Bcl-2. Furthermore, platycodin D (5-20 μmol/L) induced autophagy in BEL-7402 cells, as evidenced by formation of cytoplasmic vacuoles, increased amounts of LC3-II, and increased numbers of MDC-positive cells. Pretreatment with the autophagy inhibitor chloroquine (5 μmol/L) or BAF (50 nmol/L) significantly enhanced platycodin D-induced proliferation inhibition and apoptosis. Moreover, platycodin D (20 μmol/L) activated the ERK and JNK pathways in BEL-7402 cells, and simultaneous blockage of the two pathways effectively suppressed platycodin D-induced autophagy and enhanced platycodin D-induced apoptosis. In BEL-7402-bearing mice, platycodin D (10 mg·kg(-1)•d(-1)) significantly reduced relative tumor volume with decreased body weight.Platycodin D not only inhibits the proliferation of BEL-7402 cells but also suppresses BEL-7402 xenograft tumor growth. Platycodin D-induced cell proliferation inhibition and apoptosis are amplified by co-treatment with autophagy inhibitors.

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HMGB1-mediated autophagy attenuates gemcitabine-induced apoptosis in bladder cancer cells involving JNK and ERK activation.

Publications

HMGB1-mediated autophagy attenuates gemcitabine-induced apoptosis in bladder cancer cells involving JNK and ERK activation.

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