HNSCC is highly heterogeneous tumor with very poor prognosis and its incidence is increasing every year. The five-year survival rate is only 40–50% [2]. With the expanding research in the field of gene sequencing technology, gene expression profiling has attracted increasing attention, and has been used to identify prognostic markers associated with the heterogeneity of tumors. Therefore, screening for prognostic molecular markers that fully reflect the tumor biological characteristics may provide clinicians with novel tools to treat HNSCC patients. In this study, we screened DEGs in head and neck cancer tissues and adjacent non-tumor tissues, and performed Uni-variate, Lasso, and Multi-variate Cox analysis to establish a prognostic risk model for HNSCC. We identified seven DEGs: SLURP1, SCARA5, CLDN10, MYH11, CXCL13, HLF, and ITGA3, and among them MYH11 and ITGA3 were defined risk factors and the remainder as protective factors.
Five of the seven gene signatures have previously been linked to head and neck cancer. SCARA5, a member of scavenger receptor Type A family, is able to bind lipopolysaccharide, bacteria, and nucleotides to charge residues in the cysteine domain. The reduction of SCARA5 expression can promote invasiveness and proliferation of oral tumor cells, and the expression of SCARA5 was found to be down-regulated in oral tumors [15]. In addition, the SCARA5 receptor can recognize and engulf pathogens, and then transmit intracellular signals to generate an immune response. When the number of receptors is reduced, the cell is unable to mount an immune-induced defense. SCARA5 expression is usually downregulated in hepatocellular carcinoma due to high promoter methylation and allele imbalance [16].
MYH11, a smooth muscle myosin, may be involved in cell migration and adhesion, intracellular transport, and signal transduction, and as a contractile protein, it converts the chemical energy hydrolyzed by adenosine triphosphate (ATP) into mechanical energy [17]. MYH11 is closely related to the survival of HNSCC, acute myeloid leukemia, colorectal cancer, bladder cancer, and other tumors[18–20].
CXCL13 is an independent and cloned B lymphocyte chemokine named Angie, which is an antimicrobial peptide. CXC chemokines are highly expressed in spleen follicles, lymph nodes, and Peyer's patch. It promotes B-cell migration by stimulating chemotaxis into cells expressing Burkitt lymphoma receptor 1(Blr-1) and calcium influx [21, 22]. Previous studies have shown that CXCL13 is associated with the prognosis of various cancers. For example, oral squamous cell carcinoma, breast cancer, and prostate carcinoma [23–25].
Hlf-encoded proteins are a member of the proline and acid-rich (PAR) protein family, which activate transcription by forming homotypic or heterotypic dimers with other PAR family members and binding specific promoter elements. It has been reported that, HLF is closely related to the prognosis in liver cancer, gastric cancer, and lung cancer among others [26–28].
The ITGA3-encoded protein belongs to the integrin family. Integrin is an isomeric membrane protein composed of chains and chains, which acts as a cell surface adhesion molecule. the down-regulation of ITGA3 reduces the phosphorylation of AKT, ERK1/2, and FAK in SAS cells and significantly inhibited migration of cancer cells and invasion of HNSCC cells. High expression of ITGA3 predicted poor survival in patients with HNSCC [29]. Moreover, several studies have confirmed that ITGA3 is a marker of glioblastoma, pancreatic cancer, and thyroid cancer [30–32].
The role of SLURP1 and CLDN10 in head and neck cancer has not been described. The protein encoded by SLURP1, a member of the Ly6/uPAR family, has anti-tumor activity [33]. SLURP1 is related to the occurrence and development of pancreatic cancer. First, it can not only reduced invasion of cancer cells by controlling AKT, ERK, and NF-kB signaling, but also attenuates nicotine-mediated migration and invasion possibly through competing binding sites [34]. Furthermore, mutations in SLURP1 can increase the incidence of melanoma and mucosal skin cancer [35].
Studies have shown that CLDN10 is highly expressed in thyroid papillary carcinoma, and can affect cell proliferation, migration, and invasion in vitro; further, it plays the role of tumor promoter, and the up-regulation of CLDN10 is related to lymph node metastasis [36]. In contrast, low expression of CLDN10 indicated poor prognosis in lung cancer patients. The expression of CLDN10 was negatively correlated with the expression of c-fos. c-fos is considered a recognized oncogene, CLDN10 may control the invasion and metastasis of lung cancer cells by inhibiting the c-fos pathway [37]. In our study, the down-regulation of CLDN10 was associated with poor survival rates for HNSCC, which was consistent with the latter view. The mechanism of SLURP1 and CLDN10 in head and neck tumors deserves further study.
Many studies have shown that the immune system acts to control tumor growth and progression, and the prognosis of the tumor is related to lymphocyte infiltration. As an emerging anti-tumor force, immunotherapy has shown great therapeutic potential in many cancers, HNSCC is no exception. In addition, HNSCC patients with highly infiltrated CD8 T cells have a better prognosis, especially in patients who are HPV positive [38].
Our research has many advantages. First, the number of samples was much larger than in previously published studies, we integrated 9 GEO data sets and TCGA data sets, which provided full verification of the signature and made the prognostic gene model more reliable. Second, we identified several previously under-evaluated genes with unknown functions. Furthermore, we also analyzed the relevance between prognostic gene expression and the immune microenvironment. Nonetheless, the present study also includes certain limitations. First, we originally wanted to include more datasets to better validate our biomarkers. However, due to different platforms, there is a possibility of sampling deviation in gene expression values, even though we have attempted to corrected for this potential error. Second, the results obtained by bioinformatics analysis alone are not sufficient and need to be confirmed by experimental verification. Therefore, further identification of prognostic biomarkers requires experimental studies with larger samples and experimental validation.