The role of caspase 3 in producing cytokeratin 19 fragment (CYFRA21-1) in human lung cancer cell lines.
The CYFRA 21-1 assay, which detects cytokeratin 19 (CK19) fragment, is widely used as a tumor marker for lung cancer, particularly non-small cell lung cancer. However, the reason that some lung cancer cell lines release CYFRA 21-1 in culture supernatants and others do not remains unclear. We hypothesized that the release of CYFRA 21-1 might be related to the expression of CK19 and caspase 3. In order to prove this, the quantities of mRNA for CK19 were evaluated by the competitive reverse transcriptase-polymerase chain reaction (RT-PCR). CK19 protein synthesis was also evaluated by Western blotting and immunohistochemistry, and the levels of CYFRA 21-1 in the culture supernatant were measured by an immunoradiometric assay. The expression of mRNA for caspase 3 was evaluated by the RT-PCR, and caspase 3 protein synthesis was also evaluated by immunohistochemistry. In 13 lung cancer cell lines, the amounts of mRNA for CK19 correlated with the levels of CYFRA 21-1 in culture supernatants, results of Western blotting for CK19, and positivities of immunohistochemistry for CK19. In 5 cell lines that produced a significant amount of CYFRA 21-1, the level of CYFRA 21-1 correlated with the positivity of RT-PCR for caspase 3 and immunohistochmistry for caspase 3. This suggests that caspase 3 played a role in the formation of CYFRA 21-1. In addition, the specific inhibitor of caspase 3 significantly inhibited the release of CYFRA 21-1 in culture supernatants. In conclusion, we demonstrate that caspase 3, which cleaves several intermediate filaments and carries out cell apoptosis, played an important role in producing CYFRA 21-1 in human lung cancer cell lines.
First Department of Internal Medicine, Kagawa Medical University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan.
K
K
Dohmoto
S
S
Hojo
J
J
Fujita
Y
Y
Yang
Y
Y
Ueda
S
S
Bandoh
Y
Y
Yamaji
Y
Y
Ohtsuki
N
N
Dobashi
T
T
Ishida
J
J
Takahara
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000951:Antigens, Neoplasm / Q000096:biosynthesis*; D017209:Apoptosis; D014408:Biomarkers, Tumor; D015153:Blotting, Western; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases / Q000096:biosynthesis / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007150:Immunohistochemistry; D053539:Keratin-19; D007633:Keratins / Q000096:biosynthesis*; D008175:Lung Neoplasms / Q000378:metabolism*; D051379:Mice; D008957:Models, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D053539:Keratin-19; D012333:RNA, Messenger; C102012:antigen CYFRA21.1; D007633:Keratins; C505407:CASP3 protein, human; C505514:CASP6 protein, human; C505409:Casp3 protein, mouse; C505516:Casp6 protein, mouse; D053148:Caspase 3; D053178:Caspase 6; D020169:Caspases