RAD51AP1-MYC-Sam68 positive transcriptional feedback loop maintains lung cancer stemness.

Maintenance of cancer stemness drives lung cancer recurrence, metastasis, and refractoriness. Limited drug efficacy against existing stemness mechanisms suggests the existence of undiscovered complex regulatory networks. Previously, we found that RAD51AP1 is positively associated with lung cancer stemness; here, we showed that it promotes stemness maintenance in vitro and in vivo. Mechanistically, using cleavage under targets and tagmentation (CUT&Tag), dual-luciferase reporter assay (DLRA), DNA pull-down-WB, and chromatin immunoprecipitation (ChIP)-qPCR, we confirmed that RAD51AP1 transcriptionally upregulates MYC by binding to its promoter region, thereby enhancing stemness. Using a DNA pull-down assay combined with liquid chromatography-mass spectrometry (LC-MS), DLRA, and ChIP-qPCR, we verified that Sam68 binds the RAD51AP1 promoter to enhance its transcription. More importantly, MYC, conversely, targets the Sam68 promoter and upregulates its transcription. Thus, we identified a lung cancer stemness regulatory model: the RAD51AP1-MYC-Sam68-RAD51AP1 positive transcriptional feedback loop. Targeting this cascade has the potential to reverse cancer stemness and advance clinical therapies.