Malignant transformation and EGFR activation of immortalized mouse liver epithelial cells caused by HBV enhancer-X from a human hepatocellular carcinoma.
We have previously observed that all human hepatocellular carcinomas (HCCs) from HBV carriers examined had the integrated X region. In this study, HBV DNA was isolated from an integration site in one HCC that had a single, very small integrated viral DNA including the X region, but it had no expression of X gene as poly(A)RNA. It was found that HBV DNA was present between alphoid repetitive sequences, and it included Enhancer and X regions, encompassing the adr sequence from 910 to 1811. Nucleotides for 8 amino acids at the 3' end, a stop codon of X gene and a poly(A) signal downstream of X gene were lost by integration, and nucleotides for 7 amino acids and a stop codon were substituted by a connected alphoid sequence. When this cloned HBV DNA was transfected with an expression vector to an immortalized mouse liver epithelial cell line, MLE-10, malignant transformation occurred. Transformants having expressed poly(A)RNA of the X gene showed anchorage-independent growth in soft agar and tumor formation in the subcutis of nude mice. The mRNA level of EGFR was found to be remarkably enhanced in X-transformed cells, in contrast with the absence of this mRNA in parental and ras-transformed MLE-10. Our data provide evidence that the Enhancer-X region alone is the key contributor to the malignant change of pre-malignant liver cells in HBV carriers through activation of some specific genes, such as EGFR.
Miyaki
M
M
Hereditary Tumor Research Project, Tokyo Metropolitan Komagome Hospital, Tokyo, Japan. mmiyaki@opal.famille.ne.jp
Sato
C
C
Sakai
K
K
Konishi
M
M
Tanaka
K
K
Muraoka
M
M
Kikuchi-Yanoshita
R
R
Nadaoka
Y
Y
Kanda
H
H
Kitagawa
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology / Q000821:virology; D002353:Carrier State; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D004273:DNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D004279:DNA, Viral / Q000235:genetics / Q000302:isolation & purification; D004742:Enhancer Elements, Genetic; D066246:ErbB Receptors / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006509:Hepatitis B / Q000235:genetics*; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D008099:Liver; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology / Q000821:virology; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D014158:Transcription, Genetic
D004273:DNA, Neoplasm; D004279:DNA, Viral; D012333:RNA, Messenger; D066246:ErbB Receptors