Targeting an ASCL1-WNT11-ERK feed-forward loop to overcome pyrotinib resistance in HER2-positive breast cancer.

Pyrotinib resistance remains a therapeutic obstacle in human epidermal growth factor receptor 2-positive (HER2+) breast cancer (BC), and tumor-selective strategies to restore drug response are lacking. Here, we identify ASCL1 as a mediator of pyrotinib resistance. ASCL1 was elevated in resistant cells and pretreatment tumors from pyrotinib-resistant patients. High ASCL1 expression was associated with shorter overall survival after adjustment for TNM stage. Mechanistically, ASCL1 promotes WNT11 transcription, thereby engaging non-canonical WNT11-ROR2 signaling to sustain ERK phosphorylation under pyrotinib treatment. Persistent ERK activity promotes CREB1 phosphorylation and p-CREB1 binding to the ASCL1 promoter and enhances its transcription, forming an ERK-CREB1-ASCL1-WNT11 feed-forward loop that reinforces resistance. To overcome this resistance program, we develop HApt-PEG-ZIF-8@siASCL1/Pyrotinib, a HER2 aptamer-guided ZIF-8 nanoplatform for tumor-selective co-delivery of ASCL1 siRNA and pyrotinib. This nanoplatform exhibits minimal hemolysis, enhanced uptake in HER2+ BC cells, prolonged circulation, and improved tumor delivery efficiency in vivo. Co-delivery suppresses ASCL1/WNT11 signaling and downstream p-ERK and p-CREB1, inhibits proliferation, migration, and invasion, induces apoptosis, and achieves robust antitumor efficacy in pyrotinib-resistant xenografts without detectable systemic toxicity. Together, this study reveals an ASCL1-driven resistance mechanism and establishes a HER2-targeted nanotherapeutic strategy to restore pyrotinib sensitivity, supporting ASCL1 as a therapeutic target in HER2+ BC.