Background/Aim: To investigate the impact of PDZ-binding kinase (PBK) on the clinical outcome of patients with oral squamous cell carcinoma (OSCC) who received radiotherapy. Patients and Methods: PBK immunoreactivity of cancer specimens obtained from 179 patients with primary OSCC was analyzed by immunohistochemistry. Results: High PBK expression in tumor cells tended to be associated with advanced N-stage. The 5-year survival rate was greater for patients with high total PBK expression than in those with low PBK expression. After adjustment, high PBK remained associated with a favorable outcome. In subgroups according to tumor stage, the prognostic role was significant in patients with stage III/IV rather than those with stage I/II disease. Conclusion: We suggest that PBK expression should be used as an independent prognostic marker for patients with OSCC treated with radiotherapy, especially for those with advancedstage disease.Oral squamous cell carcinomas (OSCCs) are the most common among all head and neck squamous cell cancers (1). In 2020, cancer of the lip and oral cavity accounted for more than 377,713 cases and 177,757 deaths worldwide (2). Individuals from developing countries where there is higher number of risk factors, such as smoking, betel nut chewing, and alcohol consumption, are at an increased risk for developing OSCC. In Taiwan, OSCC is the fourth common cancer type (approximate incidence rate of 29 per 100,000 population and mortality of 32 per 100,000 population) and the second cancer type with the fastest increasing incidence (3). The Surveillance, Epidemiology, and End Results Cancer Statistics Review reported that the 5-year relative survival rate patients with locally advanced oral cavity and oropharyngeal cancer is 54.7% whereas it is 82.5% for those with early-stage disease (4).Many efforts have been made to identify biomarkers or specific genes that might provide useful information for clinical patient management. The complex pathogenesis of oral cancer is driven by DNA-repair genes, tumor-suppressor genes, and well-recognized factors, such as alcohol, betel nut chewing, and viral infection (5, 6). PDZ-binding kinase (PBK), also known as lymphokine-activated killer T-celloriginated protein kinase, is a mitogen-activated protein kinase kinase-like serine/threonine kinase that is involved in cell-cycle regulation via a cyclin B1-dependent manner, and in mitotic progression (7-9). PBK is found in proliferative tissues, such as testis, fetal, and neuronal stem cells; studies have found PBK overexpression in various malignancies, such as leukemia, Burkitt's lymphoma, breast cancer, and lung cancer (10-13). PBK is up-regulated in tumors; however, reports on the clinical significance of PBK are lacking. Our previous research showed the unfavorable 2177 *These Authors contributed equally to this study.
