In this study we assessed the clinical significance of an epithelial-mesenchymal transition (EMT) gene signature and explored its association with the tumor microenvironment related to immunotherapy in patients with head and neck squamous cell carcinoma (HNSCC). Genes were selected when mRNA levels were positively or negatively correlated with at least one well-known EMT marker. We developed an EMT gene signature consisting of 82 genes. The patients were classified into epithelial or mesenchymal subgroups according to EMT signature. The clinical significance of the EMT signature was validated in three independent cohorts and its association with several immunotherapy-related signatures was investigated. The mesenchymal subgroup showed worse prognosis than the epithelial subgroup, and significantly elevated PD-1, PD-L1, and CTLA-4 levels, and increased interferon-gamma, cytolytic, T cell infiltration, overall immune infiltration, and immune signature scores. The relationship between PD-L1 expression and EMT status in HNSCC after treatment with TGF-β was validated in vitro. In conclusion, the EMT gene signature was associated with prognosis in HNSCC. Additionally, our results suggest that EMT is related to immune activity of the tumor microenvironment with elevated immune checkpoint molecules. Epithelial-mesenchymal transition (EMT) refers to a process whereby the adhesive polarity of epithelial cancer cells dissipates and changes to mesenchymal cells. This occurs in conjunction with increased cell migration and invasiveness and is also known to play an important role in cytoskeletal remodeling and resistance to apoptosis 1. Several studies have reported the association of EMT activation with cancer metastasis, resistance to anticancer drugs, and thus a poor prognosis 2-4. Head and neck squamous carcinoma (HNSCC) is the sixth most prevalent cancer worldwide, with mortality rates of 40-50% despite advances in radiation and surgical treatments 5. Radiotherapy and cytotoxic chemotherapy for HNSCC are associated with substantial toxicity and morbidity. There is no biomarker that can predict response to treatments, such as radiotherapy, chemotherapy, and especially immunotherapy in patients with HNSCC. Immunotherapy has begun a new era in cancer treatment by using treatments such as checkpoint inhibitors that target the host immune system instead of tumors 6. Immune checkpoint inhibitors have showed promising preliminary data and were approved for use by the FDA in patients with advanced HNSCC 7-9. Few studies have reported the impact of EMT on the interactions between cancer and immune cells. We sought to develop an EMT gene signature that can predict prognosis by systematically analyzing genomic data from several independent cohorts of patients with HNSCC. In addition, we analyzed the association between EMT gene signatures and several immunotherapy-related gene signatures with the aim of determining whether the activation status of EMT signatures corresponds to the tumor microenvironment related to immunotherapy.

Although the genetic alteration of CUB and Sushi multiple domains 1 (CSMD1) is known to be associated with poor prognosis in several cancers, there is a lack of clinical relevance in head and neck cancer. The aim of this study was to offer insight into the clinical significance of CSMD1, utilizing a multimodal approach that leverages publicly available independent genome-wide expression datasets. CSMD1-related genes were found and analyzed to examine the clinical significance of CSMD1 inactivation in the HNSCC cohort of publicly available databases. We analyzed the frequency of somatic mutations, clinicopathologic characteristics, association with immunotherapy-related gene signatures, and the pathways of gene signatures. We found 363 CSMD1-related genes. The prognosis of the CSMD1-inactivated subgroup was poor. FBXW7, HLA-A, MED1, NOTCH2, NOTCH3, and TP53 had higher mutation rates in the CSMD1-inactivated subgroups. The Interferon-gamma score and immune signature score were elevated in CSMD1-inactivated subgroups. We identified several CSMD1-related pathways, such as the phosphatidylinositol signaling system and inositol phosphate metabolism. Our study using three large and independent datasets suggests that CSMD1-related gene signatures are associated with the prognosis of HNSCC patients.

The probability of recurrence of cancer after adjuvant or definitive radiotherapy in patients with human papillomavirus-negative (HPV(-)) head and neck squamous cell carcinoma (HNSCC) varies for each patient. This study aimed to identify and validate radiation sensitivity signature (RSS) of patients with HPV(-) HNSCC to predict the recurrence of cancer after radiotherapy. Materials and Methods: Clonogenic survival assays were performed to assess radiosensitivity in 14 HNSCC cell lines. We identified genes closely correlated with radiosensitivity and validated them in The Cancer Genome Atlas (TCGA) cohort. The validated RSS were analyzed by ingenuity pathway analysis (IPA) to identify canonical pathways, upstream regulators, diseases and functions, and gene networks related to radiosensitive genes in HPV(-) HNSCC. Results: The survival fraction of 14 HNSCC cell lines after exposure to 2 Gy of radiation ranged from 48% to 72%. Six genes were positively correlated and 35 genes were negatively correlated with radioresistance, respectively. RSS was validated in the HPV(-) TCGA HNSCC cohort (n = 203), and recurrence-free survival (RFS) rate was found to be significantly lower in the radioresistant group than in the radiosensitive group (p = 0.035). Cell death and survival, cell-to-cell signaling, and cellular movement were significantly enriched in RSS, and RSSs were highly correlated with each other. Conclusion: We derived a HPV(-) HNSCC-specific RSS and validated it in an independent cohort. The outcome of adjuvant or definitive radiotherapy in HPV(-) patients with HNSCC can be predicted by analyzing their RSS, which might help in establishing a personalized therapeutic plan.

The FAT1 gene functions as a tumor suppressor or promoter and remains incompletely understood. We examined the clinical significance of FAT1 in head and neck squamous cell carcinoma (HNSCC) using four publicly available HNSCC cohorts and one HNSCC cohort enrolled at a tertiary medical center. We developed FAT1 signatures reflecting FAT1 mutations and mRNA expression using one cohort. Patients with HNSCC were classified into FAT1-associated low risk (FAT1-LR; n = 195) and FAT1associated high risk (FAT1-HR; n = 371) subgroups. The five-year overall survival and recurrence-free survival rates were significantly lower in the FAT1-HR subgroup than in the FAT1-LR subgroup (P = 0.01 and 0.003, respectively). The clinical significance of FAT1 was validated using four independent cohorts. Cox proportional hazards models showed that the FAT1 signature was an independent prognostic factor for HNSCC patients. In addition, FAT1 signature was associated with the response to radiotherapy, advanced stage, and human papilloma virus (HPV) status in HNSCC patients. In conclusion, the FAT1 gene signature was associated with prognosis of HNSCC and may help to provide personalized treatments for HNSCC patients.

Background: We propose a novel prognostic biomarker-based strategy for increasing the efficacy of radiotherapy (RT) in head and neck squamous cell carcinoma (HNSCC). Materials and Methods: We identified genes associated with superoxide dismutase 2 (SOD2) and nuclear factor erythroid-2-related factor 2 (NRF2) from gene-expression data of The Cancer Genome Atlas (TCGA) by calculating Pearson correlation. Patients were divided into two groups using hierarchical clustering. Colonyformation assay was performed to determine radioresistance in HNSCC cell line CAL27. Pathway analysis was conducted using The Database for Annotation, Visualization and Integrated Discovery (DAVID). Results: We developed a 49gene signature with SOD2-and NRF2-associated genes. Using mRNA expression data for the 49-gene signature, we performed hierarchical clustering to stratify patients into two subtypes, subtype A and B. In the TCGA cohort, subgroup A demonstrated a better prognosis than subgroup B in patients who received RT. The signature robustness was evaluated in other independent cohorts. We showed through colony-formation assay that depletion of SOD2 or NRF2 leads to increased radiosensitivity. Conclusion: We identified and validated a robust gene signature of SOD2-and NRF2associated genes in HNSCC and confirmed their link to radioresistance using in vitro assay, providing a novel biomarker for the evaluation of HNSCC prognosis.