Commonly observed RNF43 mutations retain functionality in attenuating Wnt/β-catenin signaling and unlikely confer...

Area of Science:

• Oncology
• Molecular Biology
• Cancer Genetics

Background:

• RNF43 mutations are linked to Wnt/β-catenin pathway activation in cancer.
• Inactivating RNF43 mutations are hypothesized to sensitize cancer cells to Wnt-targeted therapies.
• The precise impact of RNF43 mutations on Wnt/β-catenin signaling regulation remains unclear.

Purpose of the Study:

• To investigate the functional consequences of RNF43 mutations on Wnt/β-catenin signaling.
• To determine which types of RNF43 mutations confer Wnt-dependency in cancer cells.
• To evaluate the clinical implications of RNF43 mutation status for Wnt-based therapeutic strategies.

Main Methods:

• Analysis of RNF43 mutation location in tumors with functional mismatch repair.
• Expression of C-terminal truncation mutants and wild-type RNF43.
• CRISPR-Cas9-mediated knockout of RNF43 in KM12 and HEK293T cells.
• Assessment of β-catenin signaling, Wnt-receptor turnover, and DVL-binding.

Main Results:

• Predominant 5' location of truncating RNF43 mutations in mismatch repair-proficient tumors.
• C-terminal RNF43 truncations (e.g., p.G659fs) showed no significant effect on β-catenin signaling or Wnt-receptor turnover.
• N-terminal RNF43 mutations were identified as the primary drivers of Wnt-dependency in colorectal cancer cells.
• No link was confirmed between RNF43 mutations and p53 or E-cadherin breakdown.

Conclusions:

• C-terminal RNF43 mutations do not appear to activate Wnt/β-catenin signaling.
• Only N-terminal RNF43 mutations confer Wnt-dependency, impacting therapeutic strategies.
• Wnt-based therapeutics should be used cautiously in cancer patients with RNF43 mutations, particularly those with C-terminal alterations.