Beta-catenin S45F mutation results in apoptotic resistance

Summary

Wnt/beta-catenin signaling is one of the key cascades regulating embryogenesis and tissue homeostasis; it has also been intimately associated with carcinogenesis. This pathway is deregulated in several tumors, including colorectal cancer, breast cancer, and desmoid tumors. It has been shown that CTNNB1 exon 3 mutations are associated with an aggressive phenotype in several of these tumor types and may be associated with therapeutic tolerance. Desmoid tumors typically have a stable genome with beta-catenin mutations as a main feature, making these tumors an ideal model to study the changes associated with different types of beta-catenin mutations. Here, we show that the apoptosis mechanism is deregulated in beta-catenin S45F mutants, resulting in decreased induction of apoptosis in these cells. Our findings also demonstrate that RUNX3 plays a pivotal role in the inhibition of apoptosis found in the beta-catenin S45F mutants. Restoration of RUNX3 overcomes this inhibition in the S45F mutants, highlighting it as a potential therapeutic target for malignancies harboring this specific CTNNB1 mutation. While the regulatory effect of RUNX3 in beta-catenin is already known, our results suggest the possibility of a feedback loop involving these two genes, with the CTNNB1 S45F mutation downregulating expression of RUNX3, thus providing additional possible novel therapeutic targets for tumors having deregulated Wnt/beta-catenin signaling induced by this mutation.