A human small cell lung cancer cell line, U-1906, developed altered functional properties upon continuous in vitro cultivation. Cells obtained at late (U-1906 L) and early (U-1906 E) passages of cultivation differ in drug resistance to the cytostatic therapeutic agents cisplatin and doxorubicin. The U-1906 L cells are 1.6-fold and 1.3-fold more resistant to cisplatin and doxorubicin respectively, than are the U-1906 E cells. In the more resistant U-1906 L cells, the total glutathione (GSH plus GSSG) level is 40% lower, whereas the activities of GSH-linked enzymes such as GSH peroxidase and GSH transferases are significantly higher. Quantitative analysis with isoenzyme-specific ELISAs demonstrated increased concentrations of all three of the measurable GSTs, M1-1, M3-3 and P1-1, in the more resistant cells. The intracellular protein expression patterns of the U-1906 E and the U-1906 L cells are very similar as revealed by two-dimensional denaturing electrophoresis, but show significant alterations in the concentrations of some components. Two 35 kDa proteins of different pI values, the concentrations of which are increased in the U-1906 L cells, were both identified as glyceraldehyde-3-phosphate dehydrogenase, either by N-terminal or by internal amino acid sequence analysis. The present study demonstrates that the increased resistance of the U-1906 L cells may involve multiple detoxification mechanisms and that the contribution of the GSH-linked detoxification can be ascribed to the elevation of cytosolic GST isoenzymes, GSH peroxidase and glutathione reductase, rather than to the intracellular GSH concentrations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.