RFX2-BNIP3 axis-driven adaptive mitophagy promotes resistance to ACK1-targeted therapy in non-small cell lung cancer

Activated Cdc42-associated kinase 1 (ACK1) is an oncogenic non-receptor kinase that promotes tumor cell survival and impairs T-cell activation. Targeting ACK1 has great promise in cancer control. However, tumor adaptive responses that may limit the anticancer efficacy of ACK1 inhibition (ACK1i) remain unclear. We found that ACK1i treatment triggered the PINK1/PARKIN-mediated adaptive mitophagy by upregulating the mitophagy receptor BNIP3. Mass/Spectrometry and co-immunoprecipitation (Co-IP) results indicated that ACK1 interacted with transcription factor regulatory factor X 2 (RFX2) through its MHR domain, and competitively inhibits RFX2 ubiquitination via the E3 ubiquitin ligase MIB1. Conversely, ACK1i facilitates MIB1-mediated RFX2 ubiquitination and degradation. Moreover, we observed that RFX2 is a transcriptional suppressor of BNIP3 using luciferase reporter gene assays and chromatin immunoprecipitation (ChIP). Overall, ACK1i treatment causes RFX2 instability and thereby diminishes RFX2's suppressive effects on BNIP3 transcription, leading to BNIP3 accumulation and the activation of mitophagy pathways. This adaptive mitophagy allows NSCLC cells to survive under ACK1 inhibition, potentially reducing the efficacy of ACK1i. ACK1i combined with mitophagy-inhibiting agents may attain a more accomplished response in NSCLC. In conclusion, ACK1i induced mitophagy through the release of RFX2 inhibition on BNIP3 transcription, thereby driving adaptive resistance. Inhibiting mitophagy sensitizes NSCLC to ACK1i.