H. Satoh et al., PRODUCTION OF CYTOKERATIN-19 FRAGMENT BY HUMAN SQUAMOUS LUNG-CANCER CELL-LINES, American journal of respiratory cell and molecular biology, 16(5), 1997, pp. 597-604
Cytokeratins form part of the cytoskeleton of both normal and malignan
t epithelium. A novel tumor marker measuring cytokeratin 19 (CK-19) fr
agment has been introduced and proven to be suitable for monitoring th
erapy 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 unkno
wn. We studied the CK-19 fragment produced by two human squamous cell
lung cancer cell lines. In Western blotting analysis, culture supernat
ants of both cell lines displayed bands of 37 and 40 kDa, which repres
ented the CK-19 fragment and the intact CK-19, respectively. Gel filtr
ation demonstrated that a part of soluble CK-19 was released as a larg
e complex form in culture supernatants. The level of CK-19 fragment in
culture supernatants increased during the exponential growth phase. C
K-19 level decreased by an addition of a cytotoxic agent to non-signif
icant level though the transient release of CK-19 fragment occurred du
ring the first 2 days. After all, soluble CK-19 fragments were detecte
d in culture supernatants of human lung cancer cell lines and its leve
l reflected proliferating cancer cells though it was not determined wh
ether CK-19 fragments were released directly from live cells.