Background: This study examined Sal-like protein (SALL)3 methylation profiles of head and neck cancer (HNSCC) patients at diagnosis and follow-up and evaluated their prognostic significance and value as a biomarker. SALL3 expression was examined in a panel of cell lines by quantitative reverse transcription polymerase chain reaction (RT-PCR). The methylation status of the SALL3 promoter was examined by quantitative methylation-specific PCR.
Results: SALL3 promoter methylation was associated with transcriptional inhibition and was correlated with disease recurrence in 64.8% of cases, with an odds ratio of 1.914 (95% confidence interval: 1.157-3.164; P = 0.011) by multivariate Cox proportional hazard regression analysis. SALL3 promoter hypermethylation showed highly discriminatory receiver operator characteristic curve profiles that clearly distinguished HNSCC from adjacent normal mucosal tissue, and was correlated with reduced disease-free survival (DFS) (log-rank test, P = 0.01). Hypermethylation of tumor-related genes was higher among patients with SALL3 methylation than among those without methylation (P < 0.001). Furthermore, SALL3 hypermethylation was associated with expression of TET1, TET2, and DNMT3A genes.
Conclusions: This study suggests that CpG hypermethylation is a likely mechanism of SALL3 gene inactivation, supporting the hypothesis that the SALL3 gene may play a role in the tumorigenesis of HNSCC and may serve as an important biomarker.
Keywords: Biomarker; Head and neck cancer; Hypermethylation; Real-time PCR; SALL3; Tumor-suppressor genes.