USP28-mediated deubiquitination of FOXK1 activates the Hippo signaling pathway to regulate cell proliferation and radiosensitivity in lung cancer.

Aims: Radioresistance remains a significant challenge for lung cancer therapeutics. Forkhead box K1 (FOXK1) plays a role in regulating various biological processes and the progression of multiple cancers. However, the role of FOXK1 in lung cancer progression and radioresistance are not fully understood.

Main Methods: Functional analyses were conducted on lung cancer cells transfected with specified siRNAs or plasmids. The ubiquitination of FOXK1 was evaluated by in vitro ubiquitination assays. RNA sequencing analysis was conducted to identify the downstream signaling pathway regulated by FOXK1. Mouse xenograft models were constructed using lung cancer cells with stable expression of either sh-NC or sh-FOXK1. Immunohistochemistry was used to assess FOXK1 and USP28 expression levels in lung cancer and paired normal lung tissues.

Key Findings: We found that elevated FOXK1 expression markedly enhances radioresistance and tumorigenesis in lung cancer. Furthermore, we demonstrated that ubiquitin specific peptidase 28 (USP28) interacts with and targets FOXK1 for deubiquitination and stabilization. Moreover, we showed that FOXK1 exerts its biological function via activating the Hippo pathway.

Significance: Our research showed that FOXK1 is deubiquitinated by USP28 and facilitates cell proloferation and radioresistance by activating the Hippo pathway, suggesting that FOXK1 may act as a potential radiosensitizing target for lung cancer.