A splicing variant of Merlin promotes metastasis in hepatocellular carcinoma

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Merlin, encoded by the NF2 tumor suppressor gene, is vital in preventing cancer growth and spread.
• The functional roles of different Merlin splicing forms remain largely unexplored.
• Low Merlin levels in hepatocellular carcinoma (HCC) correlate with poor prognosis, especially in metastatic cases.

Purpose of the Study:

• To investigate the role of Merlin splicing variants in HCC tumorigenesis and metastasis.
• To elucidate the functional impact of a specific Merlin variant, (Δ2-4)Merlin, on HCC progression.
• To understand the molecular mechanisms by which (Δ2-4)Merlin contributes to HCC metastasis.

Main Methods:

• Analysis of Merlin and (Δ2-4)Merlin levels in HCC and portal vein tumor thrombus (PVTT) specimens.
• Cellular and molecular assays to assess the binding interactions of (Δ2-4)Merlin with β-catenin and ERM proteins.
• Investigation of (Δ2-4)Merlin's effects on β-catenin and stemness gene expression, epithelial-mesenchymal transition (EMT), cell migration, and in vivo metastasis.

Main Results:

• The (Δ2-4)Merlin splicing variant is amplified in HCC and PVTT, and in a PVTT-derived cell line (CSQT2).
• (Δ2-4)Merlin impairs wild-type Merlin's binding to β-catenin and ERM, localizing to the cytoplasm instead of the cell surface.
• Overexpression of (Δ2-4)Merlin enhances β-catenin and stemness gene expression, promotes EMT, increases cell migration, and drives lung metastasis in vivo.

Conclusions:

• The (Δ2-4)Merlin variant disrupts normal Merlin tumor-suppressive functions.
• (Δ2-4)Merlin acts as an oncogenic driver, promoting HCC cell migration and metastasis.
• Targeting the (Δ2-4)Merlin variant may offer a therapeutic strategy for advanced HCC.