ABSTRACT
Tongue squamous cell carcinoma (TSCC) is a prevalent form of oral malignancy, with increasing incidence. Unfortunately, the 5-year survival rate for patients has not exceeded 50%. Studies have shown that sex-determining region Y box 9 (SOX9) correlates with malignancy and tumor stemness in a variety of tumors. To investigate the role of SOX9 in TSCC stemness, we analyzed its influence on various aspects of tumor biology, including cell proliferation, migration, invasion, sphere and clone formation, and drug resistance in TSCC. Our data suggest a close association between SOX9 expression and both the stemness phenotype and drug resistance in TSCC. Immunohistochemical experiments revealed a progressive increase of SOX9 expression in normal oral mucosa, paracancerous tissues, and tongue squamous carcinoma tissues. Furthermore, the expression of SOX9 was closely linked to the TNM stage, but not to lymph node metastasis or tumor diameter. SOX9 is a crucial gene in TSCC responsible for promoting the stemness function of cancer stem cells. Developing drugs that target SOX9 is extremely important in clinical settings.
Subject(s)
Carcinoma, Squamous Cell , Mouth Neoplasms , Tongue Neoplasms , Humans , Carcinoma, Squamous Cell/pathology , Tongue Neoplasms/metabolism , Cell Line, Tumor , Mouth Neoplasms/genetics , Tongue/metabolism , Tongue/pathology , Cell Proliferation , Gene Expression Regulation, Neoplastic , Cell Movement/genetics , SOX9 Transcription Factor/genetics , SOX9 Transcription Factor/metabolismABSTRACT
Chemotherapy resistance is a major limiting factor in the cure of patients with laryngeal squamous cell carcinoma (LSCC). Lymphocyte antigen 6 superfamily member D (Ly6D) is highly expressed in various tumors, but its role and underlying molecular mechanisms in chemoresistance of LSCC cells remains largely unclear. In this study, we reveal that overexpression of Ly6D facilitates LSCC cell chemoresistance, while Ly6D silencing abolishes this phenotype. Moreover, bioinformatics analysis, PCR array, and functional analysis confirmed that activation of the Wnt/ß-catenin pathway contributes to Ly6D-mediated chemoresistance. The genetic and pharmacological inhibition of ß-catenin compromises chemoresistance mediated by Ly6D overexpression. Mechanistically, Ly6D overexpression significantly attenuates the expression of miR-509-5p, thereby unleashing its target gene CTNNB1 to activate Wnt/ß-catenin pathway and ultimately promote chemoresistance. In contrast, Ly6D augmenting ß-catenin-mediated chemoresistance in LSCC cells were reversed by ectopic expression of miR-509-5p. Furthermore, ectopic expression of miR-509-5p markedly repressed the two other targets, MDM2 and FOXM1. Taken together, these data not only reveal the key role of Ly6D/miR-509-5p/ß-catenin in chemotherapy resistance, but also provide a new strategy for the clinical treatment of refractory LSCC.
