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ATAD2 interacts with C/EBPβ to promote esophageal squamous cell carcinoma metastasis via TGF-β1/Smad3 signaling.

ABSTRACT:

Background

Distant metastasis is the leading cause of death for esophageal squamous cell carcinoma (ESCC) with limited treatment options and unsatisfactory effectiveness. Bromodomain (BRD) containing proteins are emerging targets for cancer therapy with promising effects. As a unique member of BRD family, the function and molecular mechanism of ATAD2 in cancer development is seldomly investigated.

Methods

The clinical impact of ATAD2 was assessed both at RNA and protein level in 75 and 112 ESCC patients separately. The biological function of ATAD2 was investigated in vitro and in vivo. Signaling pathway and downstream effectors of ATAD2 were identified by RNA sequencing, luciferase reporter, co-immunoprecipitation, chromatin immunoprecipitation, immunofluorescence and western blot assay.

Results

We found that elevated ATAD2 expression was significantly associated with lymph node metastasis, advanced clinical stage as well as poor survival of ESCC patients. Silencing ATAD2 significantly suppressed ESCC cell migration and invasion in vitro, and inhibited tumor growth and lung metastasis in vivo. Mechanically, we identified a new cofactor, C/EBPβ. ATAD2 directly interacted with C/EBPβ and promoted its nuclear translocation, which directly bound to the promoter region of TGF-β1 and activated its expression. Further, we demonstrated that TGF-β1 activated its downstream effectors in a Smad3 dependent manner. In addition, we further found that ATAD2 promoted ESCC metastasis through TGF-β signaling induced Snail expression and the subsequent epithelial-mesenchymal transition.

Conclusion

Our findings demonstrated the pro-metastatic function of ATAD2 and uncovered the new molecular mechanism by regulating C/EBPβ/TGF-β1/Smad3/Snail signaling pathway, thus providing a potential target for the treatment of ESCC metastasis.

SUBMITTER: Cao LJ

PROVIDER: S-EPMC7986551 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundRadiation-induced bystander effect (RIBE) can promote tumor metastasis contributing to the failure of radiotherapy for esophageal squamous cell carcinoma (ESCC). Aberrant expression of DJ-1 has been identified in ESCC; however, the relationship between DJ-1 and RIBE in ESCC remains unknown.MethodsWe detected DJ-1 in the serum and cell supernatants by enzyme-linked immunosorbent assay (ELISA) and evaluated tumor metastasis by phenotypic experiments in vivo and in vitro. RNA-seq, mass spectrometry, western blot (WB), immunoprecipitation (IP), and dual-luciferase reporter assays were performed to explore the underlying mechanisms.ResultsDJ-1 was highly expressed in the serum of patients with ESCC receiving radiotherapy and was significantly overexpressed in the medium of ESCC cells receiving irradiation. DJ-1 promoted tumor metastasis via the TGF-β1 pathway. Mechanistic studies revealed that DJ-1 bound to HSC70 to promote Smad3 phosphorylation and nuclear aggregation in a protein-interaction manner, which activated the transcription of Thrombospondin-1 (TSP1). Subsequently, the activation of TGF-β1 by TSP1 re-promoted Smad3 phosphorylation and nuclear aggregation, constituting a positive feedback loop to strengthen the metastasis of ESCC cells, which was effectively blocked by LY2109761 and LSKL. Moreover, higher levels of serum DJ-1 in patients with ESCC were related to a poorer prognosis of radiotherapy.ConclusionsIrradiation can induce ESCC cells secreting DJ-1. Secreted DJ-1 enters bystander cells to initiate activation of the TGF-β1 pathway via the DJ-1/HSC70/Smad3 signaling axis. The TSP1/TGF-β1/Smad3 positive feedback pathway constitutes the core pathway that promotes ESCC metastasis. DJ-1 is a useful biomarker for predicting the efficacy of radiotherapy and a potential therapeutic target for reversing RIBE in ESCC. Schematic diagram showing the underlying mechanism that irradiation-induced secretion of DJ-1 accelerates the metastasis of bystander ESCC cells.