Aberrant methylation and expression of DAPk1 in human hypopharyngeal squamous cell carcinoma

Abstract

Conclusion: These findings indicate that in hypopharyngeal squamous cell carcinoma (HSCC), hypermethylation and down-regulation of death-associated protein kinase-1 (DAPk1) are common events, which are associated with a poor prognosis. Objectives: This study aimed to investigate the methylation and expression of DAPk1, a tumor suppressor gene, in HSCC, and explore its clinical significance. Methods: The tumor and adjacent non-tumor tissues were collected from 53 patients with HSCC. The methylation status of DAPk1 was detected by methylation–specific polymerase chain reaction (MSP), and expression of DAPk1 was determined with real-time reverse transcriptase polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blot at mRNA or protein levels. Correlations between the findings and patients’ clinicopathological parameters were further evaluated. Results: The methylation ratio of DAPk1 in tumor tissues (60.38%) was significantly higher than that in the adjacent non-tumor tissues (26.42%) (p = 0.001), while DAPk1 expression in the tumors was down-regulated markedly (real-time RT-PCR, p = 0.002; immunohistochemistry, p = 0.006; Western blot, p < 0.001). DAPk1 methylation was negatively correlated with its mRNA expression (p = 0.002, r = –0.521). Both hypermethylation and down-regulation of DAPk1 were closely related to lymph node metastasis (p = 0.001 and 0.001, respectively), advanced TNM stage (p = 0.009 and 0.019, respectively), and low survival rates (p = 0.031 and 0.045, respectively).

Keywords:

• DAPk1
• HSCC
• prognosis
• lymph node metastasis
• polymerase chain reaction
• PCR

Acknowledgments

This work was supported by the Independent Innovation Foundation of Shandong University (IIFSDU, #2012TS156) and Shandong Provincial Natural Science Foundation, China (#ZR2013HM107). We thank Dr Chao Ma (Department of Basic Medicine, Qilu Hospital of Shandong University) for giving us technological assistance.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.