AKAP13 regulates GLI1/ULK1 axis and drive tumor resistance to next-generation HER2-targeted therapies.

Next-generation HER2-targeted therapies including tyrosine kinase inhibitors (TKIs) and antibody-drug conjugates (ADCs) improve survival of HER2-positive cancer patients. However, mechanisms of primary and acquired resistance remain unclear. Here, we reported that primary HER2-specific targeted therapy (tucatinib) resistant or sensitive breast cancers derived from clinical trial patients exhibited differential protein profiles. Prolonged tucatinib exposure induced autophagy pathway enrichment in HER2-positive breast cancer cells. Integrated high-throughput analyses identified A-kinase anchoring protein (AKAP)13 as a critical molecule involved in both primary and acquired resistance and an independent predictor of poor prognosis. Silencing of AKAP13 significantly diminished novel HER2-targeted therapies resistance. Mechanistically, AKAP13 inhibits autophagosome formation by suppressing the expression of ULK1, a kinase essential for autophagy initiation. ULK1 transcription is driven by GLI1, which binds to the ULK1 promoter via its arginine-592 residue. We further elucidated that the RhoGEF domain of AKAP13 activates RhoA, which subsequently triggers the activation of PKA anchored to AKAP13. The activated PKA then inhibits the nuclear translocation of GLI1, thereby repressing its transcriptional activity on ULK1. In vivo and in vitro experiments demonstrated the synergistic efficacy of tucatinib and AKAP13 inhibitor A13. In the validation phase, organoids were constructed using tissue obtained via puncture from patients resistant to trastuzumab deruxtecan, confirming upregulation of AKAP13 and A13-mediated reversal of resistance to novel HER2-targeted therapies. Collectively, these findings highlight the role of AKAP13 in drug resistance and propose A13 as a promising therapeutic strategy for HER2-positive breast cancer. Model diagram of this study and proposed molecular mechanisms.