Increased fraction of acid-soluble proteins in 0.35 M NaCl extracts of nuclei from rat liver tumors

Tumor-derived components were responsible for suppression of ornithine decarboxylase activity in the rat wounded skin

To elucidate the principal cause of delayed wound healing in a tumor-bearing host, the effect of Yoshida sarcoma-derived components on dermal wound healing was investigated in rats with the aid of ornithine decarboxylase (ODC) activity and in vivo bromodeoxyuridine (BrdU) labeling index. The ODC activity in the wounded skin decreased 3 and 7 days after intraperitoneal inoculation of Yoshida sarcoma cells (378.0 +/- 37.3 on Day 3, 280.0 +/- 140.0 on Day 7 vs. 809.3 +/- 109.5 pmol/mg protein/hour on Day 0). When administered 24 hours before and immediately after wounding, the crude nuclear component of the tumor cells significantly decreased the ODC activity in the wounded skin as compared with the control (185.9 +/- 159.8 vs. 534.0 +/- 59.1), but the non-nuclear component was not effective. When nuclear extracts of Yoshida sarcoma cells were intraperitoneally administered immediately after wounding, the 0.15 M or 0.35 M NaCl extract significantly suppressed ODC activity in the wounded skin (233.5 +/- 14.5 and 352.3 +/- 63.2 pmol/mg protein/hour, respectively) in comparison to the control (445.9 +/- 73.6). The BrdU labeling index of epidermal basal cells adjacent to the edge of the wound decreased up to 52% of the control by injection of the 0.15 M extract. It seems that tumor-derived nuclear components may be responsible for delayed wound healing which is commonly observed in cancer cachexia.

Changes in the glucose-6-phosphatase complex in hepatomas

Hepatomas tend to have a decreased glucose-6-phosphatase activity. We have observed phenotypic stability for this change in Morris hepatomas transplanted in rats. To determine if this decrease is selective for translocase functions or the hydrolase activity associated with glucose-6-phosphatase, we have compared activities in liver and hepatomas with glucose-6-phosphate or mannose-6-phosphate as substrates and with intact or histone-disrupted microsomes. In five out of seven subcutaneously transplanted rat hepatoma lines, the microsomal mannose-6-phosphatase activity was lower than in preparations from liver of normal or tumor-bearing rats. With liver microsomes and with most hepatoma microsomes, preincubation with calf thymus histones caused a greater increase in mannose-6-phosphatase than in glucose-6-phosphatase activity. In studies with liver and hepatoma microsomes there were similar increases in mannose-6-phosphatase activity with total calf thymus histones and arginine-rich histones. A smaller increase was seen with lysine-rich histones. The effect of polylysine was similar to the action of lysine-rich histones. There was only a small effect with protamine at the same concentration (1 mg/ml). Rat liver or hepatoma H1 histones gave only about half the activation seen with core nucleosomal histones. Our data suggested that microsomes of rat hepatomas tend to have decreased translocase and hydrolase functions of glucose-6-phosphatase relative to activities in untransformed liver.

Utility of protein electrophoretic analysis in the characterization of malignant tissues

High-resolution electrophoresis of samples from malignant tissues and tumour cells has developed from a simple analytical tool to a high-tech system requiring a lot of satellite techniques. Though this developmental history now demands additional expensive instrumentation and a detailed knowledge of protein chemistry, the usefulness of this technique in tumour biology has been dramatically enhanced. Consequently, electrophoretic techniques combined with additional high-resolution and sensitive analytical tools can now be used to elucidate a particular phenotype of a cancer cell; moreover, the chemical nature of this phenotype can be revealed. The way from the protein backwards to the gene is now open!

Chromatin solubilization in rapidly growing hepatomas

The presence of substantial amounts of DNA in the cytosol fractions prepared from rapidly growing transplanted rat hepatomas was confirmed. Agarose gel electrophoresis of this DNA from the Morris hepatomas 7288CTC, 7777, and 7800 suggested that it corresponds primarily to nucleosome monomers with smaller amounts of nucleosome dimers and trimers. Despite the evidence for solubilization of chromatin in rapidly growing hepatomas the potential DNA endonuclease activity was less in nuclei from these tumors than in nuclei from more slowly growing hepatomas or host livers. It was suggested that focal necrosis in rapidly growing solid tumors may be associated with the influx of divalent cations and the activation of DNA endonuclease activity.

Differences between HMG1 proteins isolated from normal and tumour cells

The properties of the non-histone chromosomal high-mobility-group 1 (HMG1) proteins from rat liver and Guerin ascites tumour cells (GAT cells) were compared and showed the following differences: (1) five spots were missing in the peptide map of HMG1 from GAT cells in comparison with that of HMG1 from rat liver; (2) HMG1 from GAT cells was about 5-times more poly(ADP)-ribosylated; (3) HMG1 from GAT cells which was found acetylated in vivo and incorporated [14C]acetate in vitro, whereas no incorporation of the label was detected in HMG1 from rat liver; (4) HMG1 from GAT cells exhibited pronounced ability to form oligomers at physiological ionic strength, while HMG1 from rat liver was predominantly in monomeric form. This property of HMG1 from GAT cells was lost upon deacetylation.

DNA in cytosol fractions obtained by differential centrifugation of homogenates of rapidly growing liver tumors

Preliminary work revealed that the cytosol fractions obtained by differential centrifugation of homogenates of the rapidly growing Morris hepatomas 7777 and 7288CTC contained substantially more DNA than could be detected with the more slowly growing hepatoma 5123C or the liver of tumor-bearing rats. The amount of DNA in the cytosol fractions of the rapidly growing hepatomas was decreased by concentrations of cations which are known to promote precipitation of solubilized chromatin. Data on the incorporation of [3H]thymidine into DNA of nuclear and cytosol fractions and the time-dependent effects of hydroxyurea were compatible with initial nuclear synthesis and later release of the DNA seen in the cytosol fractions. The amount of this DNA was increased in larger tumors and was less in isolated cells than in solid tumors. Postmortem changes in the liver and hepatoma 5123C, but not in hepatomas 7777 and 7288CTC, resulted in a large increase in DNA appearing in the cytosol fraction. The results indicated that the measurement of DNA in cytosol fractions may serve as a guide to the existence of necrosis in tumors, but is not always proportional to the degree of necrosis.