Inter- and intraclonal variability of polypeptides synthesized in a rat hepatoma cell line. Quantitative two-dimensional gel analysis

The occurrence of chromosome segregational defects is an intrinsic and heritable property of oral squamous cell carcinoma cell lines

Chromosomal segregational defects are commonly observed in cancer cells and are an important source of genetic instability. It is currently unknown whether these mitotic defects are the result of a subpopulation of defective cells or reflect characteristics of the population of cells as a whole. In this study, we compared chromosomal segregational defects in two oral squamous cell carcinoma cell lines and five single-cell clones from each of those cell lines. We used immunofluorescence microscopy to quantitate the occurrence of multipolar metaphase spindles, lagging chromosomes at metaphase and anaphase, and anaphase bridges. We conclude that chromosome segregational defects in these cancer cell lines represent an intrinsic and inherited tendency toward segregational defects in the general cell population, rather than the existence of a subpopulation of cells with segregational defects.

Expression of tumor-associated protein variants in chemically induced rat hepatomas and transformed rat liver cell lines determined by two-dimensional electrophoresis

High resolution two-dimensional electrophoresis (2-DE), using the rat liver as a model, was applied to study hepatocarcinogenesis induced by different chemical carcinogens. Several tumor-associated protein variants were detected by 2-DE in chemically induced rat hepatomas and transformed rat liver cell lines compared to normal rat liver tissue. Proliferation-related protein changes and/or protein alterations due to culture conditions were corrected for by comparison with 2-DE patterns of isolated cells from regenerating liver and short-term cultivated liver cells. Some of the tumor-associated variants were further characterized: (i) By peptide mapping with limited proteolysis we detected clear relationships between several variants. (ii) By studying post-translational modifications phosphorylated and glycosylated variants could be determined. (iii) A tumor-associated protein variant was identified by amino acid analysis and amino acid sequencing.

Quantitative two-dimensional gel electrophoresis analysis of human fibroblasts transformed by ras oncogenes

Quantitative two-dimensional gel electrophoresis was used to compare the cellular protein patterns of a normal foreskin-derived human fibroblasts cell line (LG1) and three immortal derivatives of LG1. One derivative, designated MSU-1.1 VO, was selected for its ability to grow in the absence of serum and is non-tumorigenic in athymic mice. The other two strains were selected for focus-formation following transfection with either Ha-ras or N-ras oncogenes and form high grade malignant tumors. Correspondence and cluster analysis provided a nonbiased estimate of the relative similarity of the different two-dimensional patterns. These techniques separated the gel patterns into three distinct classes: LG1, MSU-1.1 VO, and the ras transformed cell strains. The MSU-1.1 VO cells were more closely related to the parental LG1 than to the ras-transformed cells. The differences between the three classes were primarily quantitative in nature: 16% of the spots demonstrated statistically significant changes (P < 0.01, T test, mean ratio of intensity > 2) in the rate of incorporation of radioactive amino acids. The patterns from the two ras-transformed cell strains were similar, and variations in the expression of proteins that occurred between the separate experiments obscured consistent differences between the Ha-ras and N-ras transformed cells. However, while only 9 out of 758 spots were classified as different (1%), correspondence analysis could consistently separate the two ras transformants. One of these spots was five times more intense in the Ha-ras transformed cells than the N-ras.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein differences in tau mutant hamsters: candidate clock proteins

In the tau mutant hamster, the period of the circadian rhythm is shortened from about 24 h to about 22 h in heterozygotes and to about 20 h in homozygotes. Understanding the biochemical basis of the period changes in the tau mutant may elucidate the regulation of the vertebrate pacemaker. Using two-dimensional gel electrophoresis, we have found two sets of proteins that differ between the different genotypes. P33tau (about 33 kDa; pI 6.5) was found in all gels from wild type and heterozygous animals, but was absent in gels from all except one of the homozygous mutant animals. P32tau (about 32 kDa; pI 4.8) was a chain of spots, which showed a striking difference in pattern between gels from wild type animals and from mutant animals. P33tau was greatly enriched in soluble cellular fractions, whereas P32tau was found only in insoluble fractions. These differences between P33tau and P32tau were apparent in gels from both SCN and cortical tissue, suggesting that both proteins are distributed throughout the brain. These proteins should be useful as new tools to explore the biochemistry of circadian pacemakers.