Dear Editor,
We extend our sincere appreciation for the insightful and constructive editorial by Dr. Many Sze Man Chan and Dr. Terence Kin Wah Lee regarding our study on MET promotes hepatocellular carcinoma (HCC) development through the promotion of Tribbles Pseudokinase 3 (TRIB3)-mediated forkhead box O1 (FOXO1) degradation [
1,
2]. Their comprehensive analysis not only underscores the clinical relevance of our findings but also raises critical questions that will guide future investigations into the MET-TRIB3-FOXO1 axis. We are honored to contribute to this academic discourse, which advances our collective understanding of MET-driven HCC progression and potential therapeutic interventions.
MET is overexpressed in 30–50% of human HCC cases [
3] and the activation of constitutive MET signaling is predominantly categorized within the high-proliferation molecular subclass in HCC [
4]. However, the precise molecular mechanisms through which MET signaling functions in HCC remain incompletely understood, which limits the effectiveness of therapies targeting MET with inhibitors in HCC. In our study, we sought to elucidate the molecular underpinnings of MET-induced HCC progression and to investigate potential reasons for the suboptimal outcomes of MET inhibition in clinical settings. Utilizing a hydrodynamic tail vein injection (HTVi) mouse model co-expressing MET and β-catenin, we identified TRIB3 as a key mediator of MET signaling. Mechanistically, MET activation drives TRIB3 expression through the ERK-SP1 signaling cascade. Chromatin immunoprecipitation assays confirmed SP1 binding to the TRIB3 promoter, and ERK inhibition abrogated MET-induced TRIB3 upregulation.
TRIB3, in turn, recruits the E3 ubiquitin ligase COP1 to facilitate the proteasomal degradation of FOXO1, a well-known tumor suppressor [
5,
6]. This mechanism was consistently observed in HCC, colon, and breast cancer cell lines, underscoring its broader oncogenic relevance. The TRIB3-COP1-FOXO1 complex reinforces MET-driven proliferation and invasion by upregulating MET, CCND1, and TWIST1—genes previously reported to lie downstream of FOXO1 [
7-
9] thereby forming a positive feedback loop that drives HCC progression. To explore the therapeutic potential of targeting TRIB3, we employed adeno-associated virus 8, a well-established vector for liver-directed gene therapy known for its ability to achieve high-level and stable transgene expression without significant toxicity [
10], to knock down TRIB3 expression in vivo. This intervention significantly suppressed tumor growth and improved overall survival. Small-molecule drugs that specifically target TRIB3 or specific inhibitors that disrupt the interaction between TRIB3 and COP1 require further research.
In our clinical cohort of 75 HCC patients, TRIB3 expression positively correlated with MET and SP1 levels but negatively with FOXO1. Patients with high MET/TRIB3 expression exhibited the poorest overall survival and recurrence-free survival, underscoring the prognostic value of this signaling cascade. To facilitate clinical translation, we are developing a multiplex immunohistochemistry panel to quantify MET, TRIB3, and FOXO1 levels in biopsy specimens, with the goal of constructing a predictive model for MET inhibitor responsiveness.
Dr. Many Sze Man Chan and Dr. Terence Kin Wah Lee’s letter provided valuable insights; however, our study still has certain limitations. One key aspect is the HTVi model overexpresses MET and β-catenin, which may not fully recapitulate the heterogeneity of human HCC. We are now validating our findings in orthotopic HCC models derived from patient-derived xenografts with endogenous MET amplification or β-catenin mutations. Furthermore, our patient cohort primarily includes HBV-related HCC. Given the rising incidence of non-alcoholic steatohepatitis (NASH)-related HCC, we plan to extend our investigation to NASH-driven tumors to assess pathway conservation across etiologies. Moreover, TRIB3 is known to regulate lipid metabolism via COP1-mediated ubiquitination of ACC in normal hepatocytes [
11]. Whether this metabolic role contributes to tumorigenesis or therapy resistance remains to be clarified. Further studies are needed to dissect TRIB3’s context-dependent roles in normal and malignant liver tissues. Additionally, HGF/MET signaling plays a crucial role in regulating tumor microenvironment (TME) [
12], cancer stem cell (CSC) plasticity [
13] and drug resistance [
14]—areas in which TRIB3 may also exert influence. These aspects warrant further exploration.
In conclusion, we strongly agree with Dr. Chan and Dr. Lee’s characterization of the TRIB3 as a new mediator in MET-driven HCC. Our study not only unveils a mechanism of MET-driven HCC but also lays the groundwork for personalized treatment strategies through biomarker-guided stratification and combination therapy. We are grateful to the editorial team for their astute observations, which have inspired us to deepen our exploration of TRIB3 in TME regulation, CSC biology, and therapeutic resistance.
Moving forward, we are committed to translating these insights into clinical applications, including trials evaluating dual inhibition of MET and TRIB3. By addressing the limitations noted above and fostering collaborative research, we hope to develop effective therapeutic options for patients with MET-driven HCC, who currently have limited treatment alternatives.
Once again, we extend our heartfelt thanks to Dr. Chan and Dr. Lee for their generous and constructive commentary.
FOOTNOTES
-
Authors’ contribution
Data collection and analysis: All authors. Manuscript drafting and revision: All authors.
-
Conflicts of Interest
The authors have no conflicts to disclose.
Abbreviations
hydrodynamic tail vein injection
non-alcoholic steatohepatitis
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