Two-dimensional polyacrylamide gel electrophoresis of nuclear proteins in human meningiomas

The nuclear protein fraction from human meningioma cells was compared with the nuclear protein fraction of fibroblasts, derived from the same patients. The protein pattern obtained was visualized either with the silver stain technique or from labelled cells by fluorography. Whereas no specific polypeptides corresponding to tumor cells or fibroblasts could be detected in one‐dimensional polyacrylamide gel electrophoresis (1‐DE), small differences occur in the two‐dimensional gel patterns (2‐DE), using the silver protein detection. Cell cultures which were labelled during phase G 1 show twice as many polypeptides on the 2‐DE electropherogram with respect to the silver‐stained gels. Besides several proteins detectable in tumor cells and fibroblasts with both methods, a set of 5 polypeptides with an apparent molecular weight (Mr) of 30 000 and an isoelectric point (pI) near 6.1 could be detected in the 2‐DE pattern from labelled tumor cells. Furthermore, the tumor cells showed a remarkably enhanced incorporation of label in proteins in the pH range 5.5–7.0 and with Mr from 14 000–40 000. The fluorograms from both cell types reveal more than 40 polypeptides with a pI of 4.5–5.5 and an Mr from 12 000–45 000, which had never been detected on the silver‐stained electropherograms. The results indicate that cells derived from meningiomas exhibit a pattern of nuclear proteins quite similar to that obtained from fibroblasts with the same diploid karyotype. Furthermore, it seems necessary to combine the high‐resolution separation techniques with other analytical methods, e. g. specific labelling procedures, to enlighten the role of nuclear proteins during the onset of tumorgenesis.