J Cancer 2019; 10(7):1755-1763. doi:10.7150/jca.28577 This issue

Research Paper

Downregulation of DACT-2 by Promoter Methylation and its Clinicopathological Significance in Prostate Cancer

Shibao Li1,2*, Lingyu Yin1,2*, Kai Huang3*, Yao zhao1, Haoliang Zhang1,2, Chenchen Cai1, Yinhai Xu2, Lingyan Huang1, Xiaozhou Wang4, Ting Lan1, Hongchun Li1,2✉, Ping Ma1,2✉

1. School of Medical Technology, Xuzhou Medical University, Xuzhou 221004, China;
2. Department of Laboratory Medicine, Affiliated Hospital of Xuzhou Medical University, Xuzhou 221002, China;
3. Department of Urology, Northern Jiangsu People's hospital, Yangzhou 225001 China;
4. The center of functional experiment, Xuzhou Medical University, Xuzhou Jiangsu 221004, China.
*Equal contributors

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/). See http://ivyspring.com/terms for full terms and conditions.
Li S, Yin L, Huang K, zhao Y, Zhang H, Cai C, Xu Y, Huang L, Wang X, Lan T, Li H, Ma P. Downregulation of DACT-2 by Promoter Methylation and its Clinicopathological Significance in Prostate Cancer. J Cancer 2019; 10(7):1755-1763. doi:10.7150/jca.28577. Available from https://www.jcancer.org/v10p1755.htm

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Backgrounds: Dapper homolog (DACT) 2, a member of DACT gene family, is frequently down-regulated in various malignancies and linked to tumor progression. However, the regulatory mechanism of DACT-2 expression and its biological role in human prostate cancer (PCa) remains elusive. Here, we investigated the expression and an epigenetic change of DACT-2 in prostate cancer, and determined if these findings were correlated with clinicopathologic characteristics of PCa.

Methods: The expression profile of DACT-2 of was detected by qRT-PCR, Western blotting, and immunohistochemistry in four prostate cell lines (RWPE-1, LNCaP, PC-3 and DU145), 56 cases of frozen prostate tissues (forty-seven primary prostate carcinomas, nine paired noncancerous and cancerous prostate tissues) and a tissue microarray sets including 100 paraffin-embedded prostate samples (3 normal tissues, 2 cases of adjacent tissues and 95 cases of cancer). Subsequently, the regulatory mechanism of DACT-2 down-regulation was investigated through methylation-specific PCR (MSP) and bisulfite sequencing (BSP). The role of DACT-2 in prostate cancer cell migration and invasion was respectively examined by wound healing and transwell assay. After 5-aza-2'-deoxycytidine treatment of prostate cancer cells, qRT-PCR was used to detect whether the expression of DACT-2 gene mRNA in the cells recovered.

Results: Immunohistochemical results shown that the DACT-2 protein was strongly (3+) expressed in the cytoplasm of all 5 noncancerous tissues and 12.7% (12/95) prostate cancer (PCa) tissues. Whereas 68.4% (65/95) PCa samples and 18.9% (18/95) PCa tissues respectively displayed weakly (1+) expressed and moderately (2+) expressed. In addition, DACT-2 expression was negatively associated with Gleason score in tumor specimens (p=0.029). What's more, down-regulation and promoter methylation of DACT-2 were observed in 68.1% (32/47) frozen PCa tissues and all three prostate cancer cell lines. And, the expression of DACT-2 mRNA was restored by the treatment of demethylated drug 5-aza-2'-deoxycytidine in all prostate cancer lines. Prostate cancer cells invasion and migration were significantly suppressed by ectopic expression of DACT-2 in vitro.

Conclusions: Our study provides evidence that DACT-2 may be a useful biomarker for distinguishing prostate tumor tissues from non-cancerous samples and a potential target for epigenetic silencing in primary prostate Cancer.

Keywords: prostate cancer, DACT-2, methylation, Gleason score, TNM staging