SuFu somatic mutations are recognized as novel markers for genomic instability and tumor growth in lung...

Lung adenocarcinoma (LUAD), the predominant histological subtype of non-small cell lung cancer, remains a leading cause of cancer-related mortality worldwide. Suppressor of fused (SuFu) protein, a key negative regulator of the Hedgehog (Hh) signaling pathway, exhibits context-dependent roles in cancer, functioning variably as an oncogene or tumor suppressor. While loss-of-function mutations in SuFu have been implicated in tumorigenesis across several cancer types, their clinical significance in LUAD remains unclear. The study aimed to explore SuFu's regulatory effects in LUAD and evaluate its clinical value as a biomarker.

Endogenous molecular data of SuFu in LUAD were obtained from public bioinformatics databases to investigate SuFu's impact on tumor mutational burden (TMB) and survival. Additionally, immunohistochemical staining was performed to analyze SuFu's impact on clinical features and overall survival (OS). SuFu was knocked out in A549 cells, followed by transcriptome sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Three mutant (MT) SuFu vectors were constructed. Dual-luciferase assays and Co-immunoprecipitation (Co-IP) experiments were conducted using these vectors to explore the functional interaction between SuFu and Glioma-associated oncogene homolog 1 (Gli1). Overexpressing cell lines of MT SuFu were established in H1975, and the transcription level of Gli1 was detected by real-time quantitative polymerase-chain reaction (RT-qPCR). Overexpressing cell lines of wild type (WT) SuFu were established in A549 and H1975, and the regulatory effect of WT SuFu on the growth of LUAD was verified through functional experiments in vitro and in vivo.

The bioinformatics analysis results indicated that SuFu was negatively correlated with TMB in LUAD, while the latter was positively correlated with high-grade node stage (N stage) and higher overall stage. In addition, high expression of SuFu significantly improved the prognosis of LUAD patients, while SuFu mutations significantly reduced the OS. Immunohistochemical results further confirmed that WT SuFu inhibited T stage, N stage, M stage, and overall stage progression, and improved OS. In A549 cells, knocking out SuFu upregulated the response level of the Hh signaling pathway. In LUAD, the endogenous expression of SuFu was not significantly reduced, but it possessed a mutation rate of approximately 1%. The dual-luciferase assays and Co-IP experiments demonstrated that SuFu mutation significantly upregulated the transcriptional activity of Gli1 and downregulated the binding strength with Gli1. RT-qPCR revealed that MT SuFu upregulated Gli1's transcription level. Functional experiments in vitro and in vivo demonstrated the tumor-suppressing effect of WT SuFu.

SuFu's rare somatic mutations (~1%) had clinical value and were confirmed as markers of LUAD progression, providing new insights into the pathogenesis of LUAD. Potential therapeutic strategies involving the SuFu-Gli1 axis have also been proposed for precision medicine in the treatment of LUAD.