Guanylate binding protein 5 triggers NF-κB activation to foster radioresistance, metastatic progression and PD-L1 expression in oral squamous cell carcinoma.

Radioresistance and metastasis are critical issues in managing oral squamous cell carcinoma (OSCC). Although immune checkpoint inhibitors (ICIs) has been recommended to treat OSCC, lacking useful biomarkers limited their anti-cancer effectiveness. We found that guanylate binding protein 5 (GBP5) is upregulated in primary tumors and associates with radioresistance in OSCC. GBP5 expression causally associated with cellular radioresistance and migration ability in the OSCC cell variants. GBP5 upregulation was examined to be correlated with NF-κB activation and programmed cell death-ligand 1 (PD-L1) elevation in OSCC samples. GBP5 knockdown was mitigated, but overexpression enhanced, NF-κB activity and PD-L1 expression in the OSCC cells. NF-κB inhibition by SN50 dramatically suppressed the GBP5-forested irradiation resistance, cellular migration ability and PD-L1 expression in OSCC cells. Importantly, GBP5 upregulation predicted a favorable outcome in cancer patients received ICI treatment. Our findings provide GBP5 as a useful biomarker to predict the anti-OSCC effectiveness of irradiation and ICIs.

AIM2 promotes irradiation resistance, migration ability and PD-L1 expression through STAT1/NF-κB activation in oral squamous cell carcinoma.

BACKGROUND: Radioresistance and lymph node metastasis are common phenotypes of refractory oral squamous cell carcinoma (OSCC). As a result, understanding the mechanism for radioresistance and metastatic progression is urgently needed for the precise management of refractory OSCC. Recently, immunotherapies, e.g. immune checkpoint inhibitors (ICIs), were employed to treat refractory OSCC; however, the lack of predictive biomarkers still limited their therapeutic effectiveness. METHODS: The Cancer Genome Atlas (TCGA)/Gene Expression Omnibus (GEO) databases and RT-PCR analysis were used to determine absent in melanoma 2 (AIM2) expression in OSCC samples. Colony-forming assay and trans-well cultivation was established for estimating AIM2 function in modulating the irradiation resistance and migration ability of OSCC cells, respectively. RT-PCR, Western blot and flow-cytometric analyses were performed to examine AIM2 effects on the expression of programmed death-ligand 1 (PD-L1) expression. Luciferase-based reporter assay and site-directed mutagenesis were employed to determine the transcriptional regulatory activity of Signal Transducer and Activator of Transcription 1 (STAT1) and NF-κB towards the AIM2-triggered PD-L1 expression. RESULTS: Here, we found that AIM2 is extensively upregulated in primary tumors compared to the normal adjacent tissues and acts as a poor prognostic marker in OSCC. AIM2 knockdown mitigated, but overexpression promoted, radioresistance, migration and PD-L1 expression via modulating the activity of STAT1/NF-κB in OSCC cell variants. AIM2 upregulation significantly predicted a favorable response in patients receiving ICI treatments. CONCLUSIONS: Our data unveil AIM2 as a critical factor for promoting radioresistance, metastasis and PD-L1 expression and as a potential biomarker for predicting ICI effectiveness on the refractory OSCC.

NEDD8 promotes radioresistance via triggering autophagy formation and serves as a novel prognostic marker in oral squamous cell carcinoma.

BACKGROUND: Radiotherapy is the first-line regimen for treating oral squamous cell carcinoma (OSCC) in current clinics. However, the development of therapeutic resistance impacts the anticancer efficacy of irradiation in a subpopulation of OSCC patients. As a result, discovering a valuable biomarker to predict radiotherapeutic effectiveness and uncovering the molecular mechanism for radioresistance are clinical issues in OSCC. METHODS: Three OSCC cohorts from The Cancer Genome Atlas (TCGA), GSE42743 dataset and Taipei Medical University Biobank were enrolled to examine the transcriptional levels and prognostic significance of neuronal precursor cell-expressed developmentally downregulated protein 8 (NEDD8). Gene set enrichment analysis (GSEA) was utilized to predict the critical pathways underlying radioresistance in OSCC. The colony-forming assay was used to estimate the consequences of irradiation sensitivity after the inhibition or activation of the NEDD8-autophagy axis in OSCC cells. RESULTS: NEDD8 upregulation was extensively found in primary tumors compared to normal adjacent tissues and potentially served as a predictive marker for the therapeutic effectiveness of irradiation in OSCC patients. NEDD8 knockdown enhanced radiosensitivity but NEDD8 overexpression reduced it in OSCC cell lines. The inclusion of MLN4924, a pharmaceutical inhibitor for NEDD8-activating enzyme, dose-dependently restored the cellular sensitivity to irradiation treatment in irradiation-insensitive OSCC cells. Computational simulation by GSEA software and cell-based analyses revealed that NEDD8 upregulation suppresses Akt/mTOR activity to initiate autophagy formation and ultimately confers radioresistance to OSCC cells. CONCLUSION: These findings not only identify NEDD8 as a valuable biomarker to predict the efficacy of irradiation but also offer a novel strategy to overcome radioresistance via targeting NEDD8-mediated protein neddylation in OSCC.