title: Circulating Methylated XAF1 DNA Indicates Poor Prognosis for Gastric Cancer.
abstract: Methylated DNA in fluids may be a suitable biomarker for cancer patients. XAF1 has been shown to be frequently down-regulated in human gastric cancer (GC). Here, we investigated if XAF1 methylation in GC could be a useful biomarker.
  
  
  
  Real-time RT-PCR was used to detect XAF1 mRNA expression; immunohistochemistry and western blot were used to examine XAF1 protein expression in GC tissues (n = 202) and their corresponding para-cancerous histological normal tissues (PCHNTs). Real-time methylation specific-PCR was used to investigate XAF1 promoter methylation in the same panel of GC tissues, their PCHNTs and sera.
  
  
  
  We confirmed frequent XAF1 down-regulation in both mRNA and protein levels in GC tissues as compared to normal controls and PCHNTs. XAF1 hypermethylation was evidenced in 83.2% (168/202) of GC tissues and 27.2% (55/202) of PCHNTs, while no methylation was detected in the 88 normal controls. The methylation level in GC tissues was significantly higher than that in PCHNTs (p<0.05). The hypermethylation of XAF1 significantly correlated with the down-regulation of XAF1 in GC tissues in both mRNA and protein levels (p<0.001 each). Moreover, we detected high frequency of XAF1 methylation (69.8%, 141 out of 202) in the sera DNAs from the same patients, while the sera DNAs from 88 non-tumor controls were negative for XAF1 methylation. The XAF1 methylation in both GC tissues and in the sera could be a good biomarker for diagnosis of GC (AUC = 0.85 for tissue and AUC = 0.91 for sera) and significantly correlated with poorer prognosis (p<0.001). In addition, after-surgery negative-to-positive transition of XAF1 methylation in sera strongly associated with tumor recurrence.
  
  
  
  1) Dysfunction of XAF1 is frequent and is regulated through XAF1 promoter hypermethylation; 2) Detection of circulating methylated XAF1 DNAs in the serum may be a useful biomarker in diagnosis, evaluating patient's outcome (prognosis and recurrence) for GC patients.
authors.affiliation: Zhejiang Cancer Research Institute, Zhejiang Province Cancer Hospital, Zhejiang Cancer Center, Hangzhou, Zhejiang, China.
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Ling
authors.forename: Ping
authors.initials: P
authors.lastname: Lv
authors.forename: Xiao-Xiao
authors.initials: XX
authors.lastname: Lu
authors.forename: Jiang-Liu
authors.initials: JL
authors.lastname: Yu
authors.forename: Jing
authors.initials: J
authors.lastname: Han
authors.forename: Li-Sha
authors.initials: LS
authors.lastname: Ying
authors.forename: Xin
authors.initials: X
authors.lastname: Zhu
authors.forename: Wang-Yu
authors.initials: WY
authors.lastname: Zhu
authors.forename: Xian-Hua
authors.initials: XH
authors.lastname: Fang
authors.forename: Shi
authors.initials: S
authors.lastname: Wang
authors.forename: Yi-Chen
authors.initials: YC
authors.lastname: Wu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D014408:Biomarkers, Tumor / Q000097:blood / Q000235:genetics; D045744:Cell Line, Tumor; D019175:DNA Methylation; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000097:blood* / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000097:blood* / Q000235:genetics*; D009364:Neoplasm Recurrence, Local / Q000235:genetics / Q000378:metabolism; D011379:Prognosis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D047368:Tumor Burden
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D014408:Biomarkers, Tumor; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C417551:XAF1 protein, human