ADCY7 dictates N-cadherin stability to inhibit HCC metastasis

Abstract

Background & aims: Hepatocellular carcinoma (HCC), the third leading cause of cancer-related mortality worldwide, remains a therapeutic challenge because of its propensity for early recurrence and metastasis. Our previous study has identified adenylate cyclase 7 (ADCY7), a member of the adenylate cyclase family, as a tumor suppressor in HCC through T cell-dependent immunity. Nevertheless, the exact role and underlying mechanisms of ADCY7 in HCC metastasis remain largely unknown.

Methods: Immunohistochemistry was used to measure the expression levels of ADCY7 in HCC and its clinical relevance (n = 142). Transwell assay was conducted to examine cell migration and invasion. Tail-vein lung metastasis HCC model was utilized for in vivo experiments. Furthermore, the role of ADCY7 in regulating N-cadherin levels was investigated via quantitative PCR, Western blot, immunofluorescence, and co-immunoprecipitation.

Results: Our results demonstrated that ADCY7 functioned as a critical suppressor of HCC metastasis. Clinically, reduced ADCY7 expression correlated with metastatic progression and poor prognosis (p = 0.02) in patients with HCC. Functional studies showed that ADCY7 re-expression potently inhibited HCC cell migration (p <0.0001) and invasion (p <0.0001) in vitro and attenuated pulmonary metastasis (p <0.05) in vivo. Mechanistically, ADCY7 served as a molecular scaffold to enhance the interaction between N-cadherin and the E3 ubiquitin ligase SMURF2 (SMAD Specific E3 Ubiquitin Protein Ligase 2), facilitating N-cadherin's K48 linked polyubiquitination at lysine 896 (K896) and promoting its degradation through proteasomal and lysosomal pathways. Importantly, exosomes harboring ADCY7 could be internalized by other HCC cells, suppressing N-cadherin expression and thus reducing metastatic burden.

Conclusions: Collectively, our findings unveil ADCY7 as a metastasis suppressor and highlight its therapeutic potential as a molecular target for combating HCC.

Impact and implications: We have identified ADCY7 and exosomal ADCY7 as potential therapeutic targets for inhibiting HCC metastasis. Our experimental results indicated that ADCY7 could induce the ubiquitination and degradation of N-cadherin by acting as a molecular scaffold to enhance the interaction between N-cadherin and the E3 ubiquitin ligase SMURF2, consequently impeding HCC metastasis. Therefore, ADCY7 holds great promise as a therapeutic target for HCC.

Keywords: ADCY7; Exosomes; Hepatocellular carcinoma; Metastasis; N-cadherin.