Serine/threonine kinases 31(STK31) may be a novel cellular target gene for the HPV16 oncogene E7 with potential as a DNA hypomethylation biomarker in cervical cancer.

Fu-Fen Yin,Fu-Fen Yin,Xiao-Ning Bi,You-Lin Wang,Yan-Kui Wang,Yan-Kui Wang,Ning Wang,Ning Wang,Xiao-Ning Bi,Bing Luo,Xiao Yu,Xiao-Hui Xu,Xiao-Hui Xu,Cheng-Quan Zhao,Cheng-Quan Zhao

doi:10.1186/s12985-016-0515-5

Abstract

BackgroundCervical cancer (CC) is a leading cause of mortality in females, especially in developing countries. The two viral oncoproteins E6 and E7 mediate the oncogenic activities of high-risk human papillomavirus (hrHPV), and hrHPV, especially HPV16 or/and HPV18 (HPV16/18) play critical roles in CC through different pathways. STK31 gene of which the expression has been proven to be regulated by the methylation status of its promoter, is one of the novel cancer/testis (CT) genes and plays important roles in human cancers. Reasearches have indicated that viral infection is correlated to the methylation statuses of some genes. Herein, we detected methylation status of the STK31 gene in cervical tumors and explored its interaction with HPV16 or/and HPV18 (HPV16/18) infection.MethodsBisulfite genomic sequencing PCR (BGS) combined with TA clone, methylation-specific PCR (MSP) were used to analyze methylation statuses of the STK31 gene promoter/exon 1 region in HPV16/18-positive, HPV-negative CC cell lines; ectopically expressed HPV16 E6, -E7, and -E6/E7 CC cells; normal cervical tissues and cervical tumor tissues of different stages. The mRNA and protein expressions of STK31 were detected by RT-PCR and western blotting.ResultsThe STK31 gene promoter/exon 1 was hypomethylated in the HPV16/18-positive cell lines HeLa, SiHa and CaSki, and the mRNA and protein expression were detected. In contrast, the STK31 gene exhibited hypermethylation and silenced expression in the HPV-negative CC cells C33A and HT-3. Compared with the primary HPV-negative CC cell lines, the STK31 methylation was downregulated, and STK31 expression was induced in the HPV16E7/E67 transfected cells. The methylation statuses and expressions of STK31 were verified in the cervical tumor samples at different stages. Additionally, chemotherapy treatment may influence STK31 expression by regulating its methylation status.ConclusionsSTK31 may be a novel cellular target gene for the HPV16 oncogeneE7. The HPV16 oncogene E7 may affect STK31 expression through a methylation-mediated mechanism. The aberrant methylation of the STK31 promoter/exon 1 region may be a precursor of human cervical carcinogenesis and a potential DNA aberrant methylation biomarker of conditions ranging from precancerous disease to invasive cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0515-5) contains supplementary material, which is available to authorized users.

Highlights

Cervical cancer (CC) is a leading cause of mortality in females, especially in developing countries
HPV16 E7 and E6/E7 oncoproteins induced or influenced Serine/threonine kinases 31 (STK31) gene expression in CC cells through regulating the methylation status of STK31 The transfection efficiency was tested by western blotting, which revealed that the transfected cells successfully expressed the E6, -E7, or -E6/E7 proteins (Fig. 1a)
The reverse-transcription PCR (RT-PCR) and western blotting results (Fig. 1b) revealed that STK31 expression was present in the HPV16/18-positive cervical cell lines HeLa, SiHa, and CaSki cells but silenced in the HPV-negative CC cell lines C33A and HT-3 cells

Summary

Introduction

Cervical cancer (CC) is a leading cause of mortality in females, especially in developing countries. The two viral oncoproteins E6 and E7 mediate the oncogenic activities of high-risk human papillomavirus (hrHPV), and hrHPV, especially HPV16 or/and HPV18 (HPV16/18) play critical roles in CC through different pathways. STK31 gene of which the expression has been proven to be regulated by the methylation status of its promoter, is one of the novel cancer/testis (CT) genes and plays important roles in human cancers. The two viral oncoproteins E6 and E7 mediate the oncogenic activities of high-risk human papillomavirus (hrHPV), especially HPV16 or/and HPV18 (HPV16/18), which have been demonstrated to play critical roles in CC through different pathways [2, 3]. The results have demonstrated that the STK31 gene play crucial roles in human cancers. The biological function of STK31 and the potentially associated epigenetic mechanism have not yet been investigated in CC

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