A selective splicing variant of hepcidin mRNA in hepatocellular carcinoma cell lines.
Hepcidin is a main regulator of iron metabolism, of which abnormal expression affects intestinal absorption and reticuloendothelial sequestration of iron by interacting with ferroportin. It is also noted that abnormal iron accumulation is one of the key factors to facilitate promotion and progression of cancer including hepatoma. By RT-PCR/agarose gel electrophoresis of hepcidin mRNA in a hepatocellular carcinoma cell line HLF, a smaller mRNA band was shown in addition to the wild-type hepcidin mRNA. From sequencing analysis, this additional band was a selective splicing variant of hepcidin mRNA lacking exon 2 of HAMP gene, producing the transcript that encodes truncated peptide lacking 20 amino acids at the middle of preprohepcidin. In the present study, we used the digital PCR, because such a small amount of variant mRNA was difficult to quantitate by the conventional RT-PCR amplification. Among seven hepatoma-derived cell lines, six cell lines have significant copy numbers of this variant mRNA, but not in one cell line. In the transient transfection analysis of variant-type hepcidin cDNA, truncated preprohepcidin has a different character comparing with native preprohepcidin: its product is insensitive to digestion, and secreted into the medium as a whole preprohepcidin form without maturation. Loss or reduction of function of HAMP gene by aberrantly splicing may be a suitable phenomenon to obtain the proliferating advantage of hepatoma cells.
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Yasumichi
Y
Toki
Department of Gastrointestinal Immunology and Regenerative Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan. Electronic address: k-sasaki@asahikawa-med.ac.jp.
Katsunori
K
Sasaki
Department of Legal Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Hiroki
H
Tanaka
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Masayo
M
Yamamoto
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Mayumi
M
Hatayama
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Satoshi
S
Ito
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Katsuya
K
Ikuta
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Motohiro
M
Shindo
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Takumu
T
Hasebe
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Shunsuke
S
Nakajima
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Koji
K
Sawada
Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, Hokkaido 078-8510, Japan.
Mikihiro
M
Fujiya
Oncology Center, Asahikawa Medical University Hospital, Hokkaido 078-8510, Japan.
Yoshihiro
Y
Torimoto
Department of Gastroenterology, International University of Health and Welfare Hospital, Tochigi 329-2763, Japan.
Takaaki
T
Ohtake
Department of Gastroenterology, International University of Health and Welfare Hospital, Tochigi 329-2763, Japan.
Yutaka
Y
Kohgo
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D005091:Exons; D057809:HEK293 Cells; D064451:Hepcidins / Q000235:genetics*; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000235:genetics* / Q000378:metabolism*
C578702:HAMP protein, human; D064451:Hepcidins; D020033:Protein Isoforms; D012333:RNA, Messenger; D012334:RNA, Neoplasm
Aberrant splicing; Cell lines; HAMP gene; Hepatocellular carcinoma; Hepcidin mRNA