title: 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.
abstract: BACKGROUND
  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. 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.
  
  
  METHODS
  Bisulfite 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  STK31 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.
authors.affiliation: Department of Obstetrics and Gynecology, Affiliate Hospital of Qingdao University, Qingdao, China.
authors.forename: Fu-Fen
authors.initials: FF
authors.lastname: Yin
authors.affiliation: Department of Obstetrics and Gynecology, Affiliate Hospital of Qingdao University, Qingdao, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.affiliation: Department of Obstetrics and Gynecology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Xiao-Ning
authors.initials: XN
authors.lastname: Bi
authors.affiliation: Department of Obstetrics and Gynecology, Affiliate Hospital of Qingdao University, Qingdao, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Yu
authors.affiliation: Department of Obstetrics and Gynecology, Affiliate Hospital of Qingdao University, Qingdao, China.
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Xu
authors.affiliation: Department of Urology, Shanghai Institute of Andrology, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: You-Lin
authors.initials: YL
authors.lastname: Wang
authors.affiliation: Department of Pathology, Magee-Womens Hospital, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
authors.forename: Cheng-Quan
authors.initials: CQ
authors.lastname: Zhao
authors.affiliation: Department of Medical Microbiology, Qingdao University Medical College, Qingdao, 266021, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Luo
authors.affiliation: Department of Obstetrics and Gynecology, Affiliate Hospital of Qingdao University, Qingdao, China. qdwykpro@163.com.
authors.forename: Yan-Kui
authors.initials: YK
authors.lastname: Wang
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D054884:Host-Pathogen Interactions; D052162:Human papillomavirus 16 / Q000502:physiology*; D052161:Human papillomavirus 18 / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009856:Oncogene Proteins, Viral / Q000378:metabolism; D050725:Papillomavirus E7 Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis*; D060888:Real-Time Polymerase Chain Reaction; D002583:Uterine Cervical Neoplasms / Q000473:pathology* / Q000821:virology
chemical_list: D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; C052633:E7 protein, Human papillomavirus type 18; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; C059731:oncogene protein E7, Human papillomavirus type 16; D004247:DNA; D017346:Protein Serine-Threonine Kinases; C000592903:STK31 protein, human
keywords: 5-aza-2′deoxycytidine; Biomarker; Cervical cancer; DNA methylation; Human papillomavirus; STK31