The Silencing of CCND2 by Promoter Aberrant Methylation in Renal Cell Cancer and Analysis of the Correlation between CCND2 Methylation Status and Clinical Features

Lu Wang,Jie Jin,Guanyu Kuang,Yu Fan,Yang Yang,Yun Cui,Qian Zhang,Lian Zhang,Jindong Sheng,Xin Gao

doi:10.1371/journal.pone.0161859

Abstract

Cyclin D2 (CCND2) is a member of the D-type cyclins, which plays a pivotal role in cell cycle regulation, differentiation and malignant transformation. However, its expression status and relative regulation mechanism remains unclear in renal cell cancer (RCC). In our study, the mRNA expression level of CCND2 is down-regulated in 22/23 paired RCC tissues (p<0.05). In addition, its protein expression level is also decreased in 43/43 RCC tumor tissues compared with its corresponding non-malignant tissues (p<0.001). We further detected that CCND2 was down-regulated or silenced in 6/7 RCC cell lines, but expressed in “normal” human proximal tubular (HK-2) cell line. Subsequently, MSP and BGS results showed that the methylation status in CCND2 promoter region is closely associated with its expression level in RCC cell lines. Treatment with 5-Aza with or without TSA restored CCND2 expression in several methylated RCC cell lines. Among the 102 RCC tumors, methylation of CCND2 was detected in 29/102 (28%) cases. Only 2/23 (8.7%) adjacent non-malignant tissues showed methylation. We then analyzed the correlation of clinical features and its promoter methylation. Collectively, our data suggested that loss of CCND2 expression is closely associated with the promoter aberrant methylation.

Highlights

In mammals, loss control of cell cycle is a distinctive feature of human carcinogenesis
Serial analysis of gene expression had previously revealed that, CCND2 expression level was significantly lower in renal cell cancer (RCC) tissues
To check the validity of these findings, we performed Real-time PCR to evaluate the mRNA status of CCND2 in 23 paired RCC tumors and adjacent non-malignant tissues

Summary

Introduction

Loss control of cell cycle is a distinctive feature of human carcinogenesis. The phosohorylation of RB inactivates it and leads to the activation of transcription factors such as E2F suppressed by RB, which increased the activation of transcription of genes involved in DNA synthesis and induced cells to enter S phase [4]. Owing to their pivotal role in cell cycle regulation, the abnormal and untimely expression of these proteins is likely to disturb cell cycle and promote the carcinoma transformation [5,6]

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