title: Possible roles of a tumor suppressor gene PIG11 in hepatocarcinogenesis and As2O3-induced apoptosis in liver cancer cells.
abstract: BACKGROUND
  Our previous studies demonstrated that p53-induced gene 11 (PIG11) was involved in arsenic trioxide (As(2)O(3))-induced apoptosis in human gastric cancer MGC-803 cells. Here, we studied further PIG11 expression in human hepatocellular carcinoma (HCC) tissues and cell lines and compared the sensitivity to As(2)O(3)-induced cell apoptosis in HepG2 and L-02 cells.
  
  
  METHODS
  PIG11 expression in human normal liver tissues, HCC tissues, and cell lines was determined by immunohistochemistry and immunocytochemistry methods, using an anti-human PIG11 antibody. Cell viability was estimated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diplenyltetrazolium bromide (MTT) assay. Cell apoptosis was determined by flow cytometry. Reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blotting were performed to analyze PIG11 mRNA and protein expression in cells. Protein intensity was calculated by comparison with the intensity of beta-actin, using densitometry. PIG11 was knocked down using small interfering RNA (siRNA).
  
  
  RESULTS
  We found that PIG11 expression was significantly downregulated in HCC tissue and the cell lines (Bel-7402, SMMC-7721, HepG2 cells). Further, HepG2 cells were more sensitive to As(2)O(3)-induced apoptosis than L-02 cells. The expression of PIG11 mRNA and protein was upregulated to a greater extent in HepG2 than in L-02 cells. In the presence of actinomycin D or cycloheximide, the amount of PIG11 protein expression did not increase. Likewise, the inhibition of PIG11 by siRNA decreased As(2)O(3)-induced PIG11 protein expression by more than 85% and partially prevented As(2)O(3)-induced apoptosis in both HepG2 and L-02 cells.
  
  
  CONCLUSIONS
  The above results demonstrated that the PIG11 gene may be involved in As(2)O(3)-induced apoptosis in HepG2 cells and suggested that the adaptive response of PIG11 expression is one of the important factors in enhancing cell sensitivity to As(2)O(3)-induced apoptosis.
authors.affiliation: Cancer Research Institute, Nanhua University, Hengyang, Hunan, China.
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Liu
authors.forename: Xiu-Fang
authors.initials: XF
authors.lastname: Xiong
authors.forename: Ying
authors.initials: Y
authors.lastname: Song
authors.forename: Rong-Jun
authors.initials: RJ
authors.lastname: Tang
authors.forename: Xiao-Qiu
authors.initials: XQ
authors.lastname: Liang
authors.forename: En-Hua
authors.initials: EH
authors.lastname: Cao