Moreover, a recent study found that PDXs from the luminal AR+ subtype (LAR+) of ER−/PR−/HER2− BC (TNBC), which accounts for up to 9% of all TNBCs [141] and is characterized by AR activation, are highly enriched in PI3KCA and AKT1 mutations (100% in LAR+ TNBC vs. 7.5% in other subtypes of TNBCs) [142]. Here, ESR1 is linked to breast cancer.