FOXA1 mutations alter pioneering activity, differentiation and prostate cancer phenotypes

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Mutations in the transcription factor FOXA1 are found in a specific group of prostate cancers.
• The functional impact and gain- or loss-of-function nature of FOXA1 mutations remain largely unknown.

Purpose of the Study:

• To analyze the landscape of FOXA1 mutations in human prostate cancers.
• To investigate the functional consequences of FOXA1 mutations on cellular behavior and gene regulation.

Main Methods:

• Annotation of FOXA1 mutations from 3,086 prostate cancer samples.
• Functional assays using mouse prostate organoids and reporter assays.
• Assay for transposase-accessible chromatin using sequencing (ATAC-seq) to assess chromatin accessibility and DNA binding.

Main Results:

• Identified two mutation hotspots in the FOXA1 forkhead domain: Wing2 and R219.
• Wing2 mutations occurred in all stages of adenocarcinoma, while R219 mutations were enriched in metastatic neuroendocrine tumors.
• FOXA1 mutants demonstrated gain-of-function in proliferation assays; R219 mutants specifically blocked luminal differentiation and promoted mesenchymal/neuroendocrine programs.
• ATAC-seq revealed mutant-specific chromatin changes and altered FOXA1 binding motifs, with R219 mutants favoring non-canonical motifs.

Conclusions:

• FOXA1 mutations significantly alter its pioneering function and DNA binding preferences.
• These alterations disrupt normal luminal epithelial differentiation programs.
• The findings support the role of lineage plasticity in prostate cancer progression.