TGIF2-Induced HMGB3 Promotes Esophageal Squamous Cell Carcinoma Progression Through TGFβ Signaling

Abstract

Background: Proliferation and metastasis are the major malignant phenotypes of esophageal squamous cell carcinoma (ESCC) and the main causes for poor survival in patients with ESCC. Nevertheless, the underlying mechanisms of ESCC proliferation and metastasis remains unclear. The high mobility group box protein family 3 (HMGB3) is one of the HMGB family members. It is critically involved in the occurrence and development of various carcinomas. However, the knowledge of HMGB3 in ESCC remains limited. In this study, we elucidated the role of HMGB3 in ESCC proliferation and metastasis, and the concrete mechanism. Methods: Expression level of HMGB3 and TGF-β interacting factor 2 (TGIF2) in ESCC cell lines and tissues was quantified by qRT-PCR, Western Blot, and immunohistochemistry. In vitro and in vivo assays revealed the functions of TGIF2 and HMGB3 in ESCC. RNA-seq was performed to search for the downstream signaling of HMGB3. ChIP assay and were performed to explore the relationship of HMGB3 and TGIF2. HMGB3-interacting protein was validated by immunoprecipitation.Results: Higher expression of TGIF2 and HMGB3 was observed in ESCC cell lines and tissues and was associated with worse prognosis of ESCC patients. TGIF2 and HMGB3 upregulation could promote ESCC proliferation and metastasis, and vice versa. TGIF2 and HMGB3 upregulation can activate Smad-dependent TGF-β signaling. TGIF2 can transcriptionally regulate HMGB3, and its TGF-β inducing capability and oncogenic role are at least partly HMGB3-dependent. Additionally, TLR3 was identified as a client protein of HMGB3, and their combination might be the reason of TGF-β activation. Conclusions: Collectively, HMGB3-dependent TGIF2 overexpression activates TGF-β signaling and promotes the proliferation and metastasis of ESCC via TLR3 regulation. These findings revealed that TGIF2 and HMGB3 could be prognostic indicators of ESCC and targeting TGIF2/HMGB3/TLR3 axis might improve the OS of ESCC patients.