# BRAFV600E augments WNT signaling in colorectal cancer via aberrant DNA methylation

## TL;DR

This study shows that the BRAFV600E mutation in colorectal cancer boosts WNT signaling by changing DNA methylation patterns, and DNA demethylation can reduce this effect.

## Contribution

The study reveals a novel mechanism by which BRAFV600E enhances WNT signaling through DNA methylation changes in colorectal cancer.

## Key findings

- BRAFV600E correction suppresses WNT target genes and upregulates WNT antagonists.
- DNA methylation patterns in BRAFV600E organoids alter WNT signaling through hypermethylation of key genes.
- Demethylation treatment inhibits WNT signaling in BRAFV600E mutant colorectal cancer.

## Abstract

The BRAFV600E mutation drives an aggressive subtype of colorectal cancer (CRC). Although WNT signaling activation is a hallmark of CRC, APC mutations are uncommon in BRAF-V600E mutant CRC, and RNF43 mutations are instead suspected to drive WNT pathway activation. Here, we investigated WNT pathway activation in BRAF-V600E mutant CRC using CRISPR-LbCpf1-corrected BRAF (V600E) and RNF43 (P441fs) organoids. BRAFE600V organoids regained dependency on EGF receptor signaling, and lost tumorigenic potential. Under identical growth conditions, correction of BRAFV600E, rather than RNF43P441fs, suppressed WNT target genes and upregulated epithelial differentiation genes and WNT antagonist genes. DNA methylation analysis revealed promoter hypermethylation of WNT antagonist genes and gene body hypermethylation —associated with transcriptional upregulation— of key WNT effectors (LGR5, EPHB2, and TCF4) in BRAFV600E organoids. Demethylation treatment resulted in upregulation of WNT antagonists and reduced WNT target gene expression in BRAFV600E organoids. Our results demonstrate that BRAFV600E enhances WNT pathway activation through modulation of DNA methylation patterns.

•CRISPR-mediated genome editing reveals late-stage cancer cell reliance on driver mutations•Unexpectedly, the BRAFV600E mutation mediates increased WNT target gene expression•BRAFV600E augments WNT signaling by altering the DNA methylation landscape•DNA demethylating agents are effective WNT signaling inhibitors in BRAF-V600E mutant CRC

CRISPR-mediated genome editing reveals late-stage cancer cell reliance on driver mutations

Unexpectedly, the BRAFV600E mutation mediates increased WNT target gene expression

BRAFV600E augments WNT signaling by altering the DNA methylation landscape

DNA demethylating agents are effective WNT signaling inhibitors in BRAF-V600E mutant CRC

Epigenetics; Cell biology; Cancer