Absence of Salivary lncRNA-XIST Indicates High Susceptibility to Oral Cancer

Oral cancer is one of the most common malignancies worldwide, with a two- or three-fold prevalence among men than among women. Except for lifestyle-related risk factors including smoking, drinking, and betel chewing, family history is a major determinant of risk in the absence of exposure to carcinogens. Genes predicting the susceptibility to oral cancer are associated with cell proliferation, cell invasion, angiogenesis, and DNA repair. Few studies have investigated sex-dependent X-linked gene expression in oral cancer. Hence, this study aimed to analyze salivary X-linked lncRNA-XIST, XIST anti-transcript TSIX, and X-linked tumor suppressor gene LDOC1 expression levels, their role in oral squamous cell carcinoma (OSCC) and correlations among clinicopathological data. Expression levels of these three genes were analyzed via quantitative polymerase chain reaction (qPCR) in the saliva of 59 OSCC patients and 43 healthy controls. Correlations among gene expression levels and clinicopathological characteristics were analyzed. Women lacking salivary XIST were 26-fold more susceptible (P < 0.0001) to OSCC than healthy women. TSIX and LDOC1 expression levels were positively correlated in all subjects, except for men with OSCC. LDOC1 was significantly downregulated in men with OSCC (P = 0.016) and significantly correlated with well-differentiated tumors (P = 0.001).