Nuclear and DNA-binding proteins in human brain tumors

Nuclear proteins obtained from human brain tumor cell lines by differential salt extraction were subjected to high-resolution two-dimensional electrophoresis. Several hundred spots were detectable in the low salt (0.4 M NaCl) extract using silver staining. These patterns exhibited remarkable differences between the different cell lines we analyzed. A less complex pattern occurred when nuclei were subsequently treated with high salt (2.5 M NaCl/5 M urea). We compared the electropherograms from various human glioblastoma cell lines and found them very similar and even a high degree of similarity occurs between glioblastomas and other human tumor cell lines. Beside these more general observations we detected several proteins at least enriched in human glioblastomas which were totally absent in low grade astrocytomas and nonglial tumors. They could be separated from the bulk of nonspecific proteins by simple modifications of the isoelectric focusing conditions. From these results we conclude that nuclear proteins obtained by sequential salt extraction and separated by two-dimensional techniques may provide tumor specific proteins suitable for antibody production.