Am. J. Respir. Cell Mol. Biol., Vol 16, No. 5, 05 1997, 597-604.
Production of cytokeratin 19 fragment by human squamous lung cancer cell lines
H Satoh, H Ishikawa, M Fujiwara, YT Yamashita, M Ohtsuka, T Ogata, S Hasegawa and H Kamma
Department of Respiratory Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba-City, Japan.
Cytokeratins form part of the cytoskeleton of both normal and malignant
epithelium. A novel tumor marker measuring cytokeratin 19 (CK-19) fragment
has been introduced and proven to be suitable for monitoring therapy and
following cases of non-small cell lung cancer, squamous cell lung cancer in
particular. However, whether the serum level of CK- 19 fragment reflects
the number of proliferating tumor mass remains unknown. We studied the
CK-19 fragment produced by two human squamous cell lung cancer cell lines.
In Western blotting analysis, culture supernatants of both cell lines
displayed bands of 37 and 40 kDa, which represented the CK-19 fragment and
the intact CK-19, respectively. Gel filtration demonstrated that a part of
soluble CK-19 was released as a large complex form in culture supernatants.
The level of CK-19 fragment in culture supernatants increased during the
exponential growth phase. CK-19 level decreased by an addition of a
cytotoxic agent to non- significant level though the transient release of
CK-19 fragment occurred during the first 2 days. After all, soluble CK-19
fragments were detected in culture supernatants of human lung cancer cell
lines and its level reflected proliferating cancer cells though it was not
determined whether CK-19 fragments were released directly from live cells.
