Expression of Fas and anti-Fas-mediated apoptosis in human hepatocellular carcinoma cell lines.
OBJECTIVE
Fas transduces apoptotic signals upon cross-linking with the Fas ligand, which is experimentally replaced by anti-Fas antibodies. Because little is known about Fas expression and function in hepatocellular carcinoma, these issues are addressed in the current article.


METHODS
We examined Fas expressions at protein and mRNA levels, and susceptibility to anti-Fas-mediated apoptosis, on six hepatocellular carcinoma cell lines.


RESULTS
Two cell lines constitutively expressed high levels of Fas both on their cell surface and in their cytoplasm, whereas the other four cell lines expressed Fas mainly in their cytoplasm. Fas mRNA of normal size was detected in all cell lines in reverse transcriptase-polymerase chain reaction analyses. Although a Fas mRNA variant, suggesting a soluble Fas molecule, was detected in the two cell lines expressing high levels of Fas, its amount was very small compared to that of normal-sized Fas transcript. Anti-Fas dose-dependently induced apoptosis exclusively in the two cell lines which constitutively express high levels of cell surface Fas. However, after preincubation with interferon-gamma, one cell line with low surface Fas expression became anti-Fas sensitive equivalent to the two cell lines expressing surface Fas at high levels. Studies of two clonally related cell lines showed that dedifferentiated clones had lower Fas expression and resistance to anti-Fas, suggesting deterioration of Fas system after clonal cell dedifferentiation.


CONCLUSIONS
These findings suggest sensitivity to anti-Fas is virtually relevant to cell surface Fas, but not to cytoplasmic Fas expression. However, its expression level does not correlate to sensitivity to anti-Fas.
First Department of Pathology, Kurume University School of Medicine, Japan.
H
H
Yano
K
K
Fukuda
M
M
Haramaki
S
S
Momosaki
S
S
Ogasawara
K
K
Higaki
M
M
Kojiro
D000970:Antineoplastic Agents / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D001323:Autoantibodies / Q000494:pharmacology*; D015139:Blotting, Southern; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D002455:Cell Division / Q000187:drug effects; D004587:Electrophoresis, Agar Gel; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D007371:Interferon-gamma / Q000494:pharmacology; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D015345:Oligonucleotide Probes / Q000737:chemistry; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology
D000970:Antineoplastic Agents; D001323:Autoantibodies; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D019014:fas Receptor; D007371:Interferon-gamma