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HMGB1-mediated autophagy promotes docetaxel resistance in human lung adenocarcinoma.

Pan B, Chen D, Huang J, Wang R, Feng B, Song H, Chen L - Mol. Cancer (2014)

Bottom Line: Mechanistic investigation revealed that HMGB1 promoted the formation of the Beclin-1-PI3K-III complex through activating the mitogen-activated protein kinase (MEK)-extracellular signal-regulated kinase (ERK) signaling pathway, thereby regulating autophagosome formation.Our results demonstrated that HMGB1-regulated autophagy is a significant contributor to docetaxel resistance in LAD cells.Suppression of HMGB1 or limiting HMGB1 cytosolic translocation diminished autophagic protection in response to docetaxel in LAD cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medical Oncology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing 210002, P,R, China. songhaizhu@163.com.

ABSTRACT

Background: Docetaxel resistance remains a major obstacle in the treatment of non-small cell lung cancer (NSCLC). High-mobility group box 1 (HMGB1) has been shown to promote autophagy protection in response to antitumor therapy, but the exact molecular mechanism underlying HMGB1-mediated autophagy has not been clearly defined.

Methods: Lung adenocarcinoma (LAD) cells were transfected with pcDNA3.1-HMGB1 or HMGB1 shRNA, followed by docetaxel treatment. Cell viability and proliferation were tested by MTT assay and colony formation assay, respectively. Annexin V flow cytometric analysis and western blot analysis of activated caspase3 and cleaved PARP were used to evaluate apoptosis, while immunofluorescence microscopy and transmission electron microscopy were applied to assess autophagy activity. The formation of the Beclin-1-PI3K-III complex was examined by immunoprecipitation analysis. NOD/SCID mice were inoculated with docetaxel-resistant SPC-A1/DTX cells transfected with control or HMGB1 shRNA.

Results: HMGB1 translocated from the nucleus to the cytoplasm in LAD cells exposed to docetaxel and acted as a positive regulator of autophagy, which inhibited apoptosis and increased drug resistance. Suppression of HMGB1 restored the sensitivity of LAD cells to docetaxel both in vivo and in vitro. Mechanistic investigation revealed that HMGB1 promoted the formation of the Beclin-1-PI3K-III complex through activating the mitogen-activated protein kinase (MEK)-extracellular signal-regulated kinase (ERK) signaling pathway, thereby regulating autophagosome formation.

Conclusions: Our results demonstrated that HMGB1-regulated autophagy is a significant contributor to docetaxel resistance in LAD cells. Suppression of HMGB1 or limiting HMGB1 cytosolic translocation diminished autophagic protection in response to docetaxel in LAD cells.

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Model depicting the mechanism by which HMGB1 modulates docetaxel resistance by regulating autophagy. Docetaxel promotes the cytosolic translocation of HMGB1. Cytosolic HMGB1 acts as an activator of autophagy, which potentiates the formation of the Beclin-1-PI3K-III complex through activating the MEK/ERK1/2 signaling pathway. PI3K-III also serves as an upstream signal of MEK/ERK1/2 for facilitating the core complex formation.
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Figure 9: Model depicting the mechanism by which HMGB1 modulates docetaxel resistance by regulating autophagy. Docetaxel promotes the cytosolic translocation of HMGB1. Cytosolic HMGB1 acts as an activator of autophagy, which potentiates the formation of the Beclin-1-PI3K-III complex through activating the MEK/ERK1/2 signaling pathway. PI3K-III also serves as an upstream signal of MEK/ERK1/2 for facilitating the core complex formation.

Mentions: In addition, we verified that the activation of the MEK-ERK1/2 signaling pathway was involved in HMGB1-mediated formation of the Beclin-1-PI3K-III complex. HMGB1 was shown to bind with Beclin-1, which then promotes Beclin-1-PI3K-III complex formation[28]. However, the assembly of the complex appears to differ in cell- and/or tissue-dependent manners[36]. A previous study indicated that ULK1-FIP200 complex formation is required for the interaction of this complex in osteosarcoma cells[37]. We found that inhibition of HMGB1 or MEK also limited the interaction between Beclin-1 and PI3K-III. However, the negative regulation of the Beclin-1- PI3K-III complex mediated by HMGB1 can be reversed after upregulation of MEK activity. Together with data from the mechanistic studies, we propose a model in which HMGB induces Beclin-1-PI3K-III complex formation through activating the MEK/ERK1/2 signaling pathway. Moreover, PI3K-III also serves as an upstream signal of MEK/ERK1/2 for facilitating the core complex formation in HMGB1-regulated autophagy (FigureĀ 9).


HMGB1-mediated autophagy promotes docetaxel resistance in human lung adenocarcinoma.

Pan B, Chen D, Huang J, Wang R, Feng B, Song H, Chen L - Mol. Cancer (2014)

Model depicting the mechanism by which HMGB1 modulates docetaxel resistance by regulating autophagy. Docetaxel promotes the cytosolic translocation of HMGB1. Cytosolic HMGB1 acts as an activator of autophagy, which potentiates the formation of the Beclin-1-PI3K-III complex through activating the MEK/ERK1/2 signaling pathway. PI3K-III also serves as an upstream signal of MEK/ERK1/2 for facilitating the core complex formation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4125709&req=5

Figure 9: Model depicting the mechanism by which HMGB1 modulates docetaxel resistance by regulating autophagy. Docetaxel promotes the cytosolic translocation of HMGB1. Cytosolic HMGB1 acts as an activator of autophagy, which potentiates the formation of the Beclin-1-PI3K-III complex through activating the MEK/ERK1/2 signaling pathway. PI3K-III also serves as an upstream signal of MEK/ERK1/2 for facilitating the core complex formation.
Mentions: In addition, we verified that the activation of the MEK-ERK1/2 signaling pathway was involved in HMGB1-mediated formation of the Beclin-1-PI3K-III complex. HMGB1 was shown to bind with Beclin-1, which then promotes Beclin-1-PI3K-III complex formation[28]. However, the assembly of the complex appears to differ in cell- and/or tissue-dependent manners[36]. A previous study indicated that ULK1-FIP200 complex formation is required for the interaction of this complex in osteosarcoma cells[37]. We found that inhibition of HMGB1 or MEK also limited the interaction between Beclin-1 and PI3K-III. However, the negative regulation of the Beclin-1- PI3K-III complex mediated by HMGB1 can be reversed after upregulation of MEK activity. Together with data from the mechanistic studies, we propose a model in which HMGB induces Beclin-1-PI3K-III complex formation through activating the MEK/ERK1/2 signaling pathway. Moreover, PI3K-III also serves as an upstream signal of MEK/ERK1/2 for facilitating the core complex formation in HMGB1-regulated autophagy (FigureĀ 9).

Bottom Line: Mechanistic investigation revealed that HMGB1 promoted the formation of the Beclin-1-PI3K-III complex through activating the mitogen-activated protein kinase (MEK)-extracellular signal-regulated kinase (ERK) signaling pathway, thereby regulating autophagosome formation.Our results demonstrated that HMGB1-regulated autophagy is a significant contributor to docetaxel resistance in LAD cells.Suppression of HMGB1 or limiting HMGB1 cytosolic translocation diminished autophagic protection in response to docetaxel in LAD cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medical Oncology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing 210002, P,R, China. songhaizhu@163.com.

ABSTRACT

Background: Docetaxel resistance remains a major obstacle in the treatment of non-small cell lung cancer (NSCLC). High-mobility group box 1 (HMGB1) has been shown to promote autophagy protection in response to antitumor therapy, but the exact molecular mechanism underlying HMGB1-mediated autophagy has not been clearly defined.

Methods: Lung adenocarcinoma (LAD) cells were transfected with pcDNA3.1-HMGB1 or HMGB1 shRNA, followed by docetaxel treatment. Cell viability and proliferation were tested by MTT assay and colony formation assay, respectively. Annexin V flow cytometric analysis and western blot analysis of activated caspase3 and cleaved PARP were used to evaluate apoptosis, while immunofluorescence microscopy and transmission electron microscopy were applied to assess autophagy activity. The formation of the Beclin-1-PI3K-III complex was examined by immunoprecipitation analysis. NOD/SCID mice were inoculated with docetaxel-resistant SPC-A1/DTX cells transfected with control or HMGB1 shRNA.

Results: HMGB1 translocated from the nucleus to the cytoplasm in LAD cells exposed to docetaxel and acted as a positive regulator of autophagy, which inhibited apoptosis and increased drug resistance. Suppression of HMGB1 restored the sensitivity of LAD cells to docetaxel both in vivo and in vitro. Mechanistic investigation revealed that HMGB1 promoted the formation of the Beclin-1-PI3K-III complex through activating the mitogen-activated protein kinase (MEK)-extracellular signal-regulated kinase (ERK) signaling pathway, thereby regulating autophagosome formation.

Conclusions: Our results demonstrated that HMGB1-regulated autophagy is a significant contributor to docetaxel resistance in LAD cells. Suppression of HMGB1 or limiting HMGB1 cytosolic translocation diminished autophagic protection in response to docetaxel in LAD cells.

Show MeSH
Related in: MedlinePlus