Promoter methylation analysis of DKK2 may be a potential biomarker for early detection of cervical cancer

BACKGROUND: Dickkopf 2 (DKK2) plays an important role in multiple cancers. Its potential value in the clinical diagnosis of cervical cancer has remained unclear. OBJECTIVES: To investigate the expression and promoter methylation levels of DKK2 in cervical cancer and their clinicopathological associations. METHODS: We used the Gene Expression Omnibus, Oncomine, Cancer Genome Atlas, and University of ALabama at Birmingham CANcer data analysis databases, reverse transcription-PCR, and methylation-specific PCR analysis to predict and examine the expression of DKK2 mRNA and DKK2 methylation levels in cell lines and cervical cancer tissues from 79 patients with cervical cancer and 63 with cervical precancerous lesions including 25 with low-grade squamous intraepithelial lesions (LSIL) and 38 patients with high-grade squamous intraepithelial lesions (HSIL). RESULTS: DKK2 mRNA expression was downregulated in all cancer cell lines and cervical cancer tissues, whereas hypermethylation of DKK2 was higher in cervical cancer tissue samples. DKK2 methylation in cervical cancer was significantly higher than that in HSIL (χ(2) = 8.346, P = 0.004), whereas DKK2 methylation in HSIL was significantly higher than that in normal cervical samples (χ(2) = 7.934, P = 0.005) and in LSIL samples (χ(2) = 4.375, P = 0.037). DKK2 silencing caused by its promoter hypermethylation was confirmed by treatment with the methyltransferase inhibitor 5-Aza-dC in cell lines. Patients with lymph node metastasis exhibited increased promoter methylation frequency (χ(2) = 5.239, P = 0.022) and low DKK2 mRNA expression (χ(2) = 3.958, P = 0.047) compared with patients with no lymph node metastasis. Patients with high-risk human papillomavirus infection exhibited increased promoter methylation frequency (χ(2) = 6.279, P = 0.015). CONCLUSIONS: DKK2 epigenetic changes of DKK2 may play a key role in the development of cervical cancer, suggesting that DKK2 hypermethylation could be used as a triage test for screening, early diagnosis, or risk prediction of cervical cancer.