FoxA1/2-dependent epigenomic reprogramming drives lineage switching in lung adenocarcinoma [HiChIP]

The ability of cancer cells to alter their identity is essential for tumor survival and progression. Loss of the pulmonary lineage specifier NKX2-1 within KRAS-driven lung adenocarcinoma (LUAD) enhances tumor progression and results in a pulmonary-to-gastric lineage switch that is dependent upon the activity of pioneer factors FoxA1 and FoxA2; however, the underlying mechanism remains largely unknown. Here, we show that FoxA1/2 reprogram the epigenetic landscape of NKX2-1-negative LUAD to facilitate a gastric differentiation program. Using sequential recombination models, we find that FoxA1/2 are required for demethylation of gastric-defining genes after Nkx2-1 deletion. FoxA1 colocalizes with TET3, an enzyme that mediates DNA demethylation, in NKX2-1-negative tumors. Deletion of Foxa1/2 results in loss of TET3 occupancy at key gastric marker genes, indicating that FoxA1/2 recruit TET3 to lineage-specific sites. H3K27ac ChIP-seq and HiChIP show that FoxA1/2 also control the activity of enhancers and promoters as well as their 3D interactions at gastric target genes following NKX2-1 loss. Furthermore, oncogenic KRAS is required for the FoxA1/2-dependent epigenetic reprogramming in NKX2-1-negative LUAD. This work demonstrates the role of FoxA1/2 in rewiring the methylation and histone landscape and cis-regulatory dynamics of NKX2-1-negative LUAD to drive cancer cell lineage switching. Overall design: To identify FoxA1/2-dependent epigenetic interactome changes, HiChIP was performed on sorted GFP+, DAPI+ nuclei from KN and KNF1F2 tumors.