# TGIF2-mediated HMGB3 overexpression promotes esophageal squamous cell carcinoma proliferation and metastasis through TLR3/TGF-β signaling

## TL;DR

This study shows that HMGB3 overexpression, driven by TGIF2, promotes the growth and spread of esophageal cancer through TLR3 and TGF-β signaling.

## Contribution

The novel finding is the TGIF2-mediated HMGB3 overexpression mechanism in ESCC progression via TLR3/TGF-β signaling.

## Key findings

- HMGB3 overexpression is linked to poor prognosis in ESCC patients.
- TGIF2 transcriptionally up-regulates HMGB3, which activates TGF-β signaling through TLR3.
- Targeting the TGIF2/HMGB3/TLR3/TGF-β axis may offer a new therapeutic strategy for ESCC.

## Abstract

Proliferation and metastasis are the core malignant characteristics in esophageal squamous cell carcinoma (ESCC) that contribute to poor prognosis. However, the mechanisms underlying cell proliferation and metastasis remain elusive. We explored the function of high-mobility group box (HMGB3) in promoting ESCC progression. HMGB3 expression in ESCC tissues and cell lines was quantified using quantitative PCR, Western blotting, and immunohistochemistry. The proliferative and migratory characteristics of ESCC cells were assessed using in vitro and in vivo assays, respectively. An RNA sequencing analysis was conducted to identify the downstream signaling pathways of HMGB3. Co-immunoprecipitation was performed to identify HMGB3-interacting proteins. HMGB3 transcriptional regulation was investigated using luciferase reporter and chromatin immunoprecipitation assays. Elevated levels of HMGB3 were observed in both patient-derived ESCC tissues and ESCC cell lines and were correlated with poor patient prognosis. HMGB3 up-regulation promoted ESCC proliferation and metastasis, whereas HMGB3 down-regulation inhibited these processes. Mechanistically, homeodomain protein transforming growth factor beta (TGF-β)-induced factor homeobox 2 (TGIF2) transcriptionally up-regulates HMGB3. HMGB3 subsequently activates TGF-β signaling through its regulation of and interaction with toll-like receptor 3 (TLR3), ultimately promoting ESCC proliferation and metastasis. Clinically, HMGB3 expression was positively correlated with TGIF2 and TGF-β, and patients with ESCC who positively co-expressed TGIF2/HMGB3, HMGB3/TGF-β, or TGIF2/TGF-β exhibited poor prognosis. The functional role of HMGB3 in ESCC proliferation and metastasis was illustrated in our research. Targeting the TGIF2/HMGB3/TLR3/TGF-β axis has the potential to serve as a promising therapeutic approach.