It is proposed that most neoplasms arise from a single cell of origin, and tumor progression results from acquired genetic variability within the original clone allowing sequential selection of more aggressive sublines. Tumor cell populations are apparently more genetically unstable than normal cells, perhaps from activation of specific gene loci in the neoplasm, continued presence of carcinogen, or even nutritional deficiencies within the tumor. The acquired genetic insta0ility and associated selection process, most readily recognized cytogenetically, results in advanced human malignancies being highly individual karyotypically and biologically. Hence, each patient's cancer may require individual specific therapy, and even this may be thwarted by emergence of a genetically variant subline resistant to the treatment. More research should be directed toward understanding and controlling the evolutionary process in tumors before it reaches the late stage usually seen in clinical cancer.

http://science.sciencemag.org/content/sci/194/4260/23.full.pdf

The clonal evolution of tumor cell populations

The biology of cancer: metabolic reprogramming fuels cell growth and proliferation

The concentrations of bases, nucleosides, and nucleosides mono-, di- and tri-phosphate are compared for about 600 published values. The data are predominantly from mammalian cells and fluids. For the most important ribonucleotides average concentrations ±SD (μM) are: ATP, 3,152±1,698; GTP, 468±224; UTP, 567±460 and CTP, 278±242. For deoxynucleosidestriphosphate (dNTP), the concentrations in dividing cells are: dATP, 24±22; dGTP, 5.2±4.5; dCTP, 29±19 and dTTP 37±30. By comparison, dUTP is usually about 0.2 μM. For, the 4 dNTPs, tumor cells have concentrations of 6–11 fold over normal cells, and for the 4 NTPs, tumor cells also have concentrations 1.2–5 fold over the normal cells. By comparison, the concentrations of NTPs are significantly lower in various types of blood cells. The average concentration of bases and nucleosides in plasma and other extracellular fluids is generally in the range of 0.4–6 μM; these values are usually lower than corresponding intracellular concentrations. For phosphate compounds, average cellular concentrations are: Pi, 4400; ribose-1-P, 55; ribose-5-P, 70 and P-ribose-PP, 9.0. The metal ion magnesium, important for coordinating phosphates in nucleotides, has values (mM) of: free Mg2+, 1.1; complexed-Mg, 8.0. Consideration of experiments on the intracellular compartmentation of nucleotides shows support for this process between the cytoplasm and mitochondria, but not between the cytoplasm and the nucleus.

Physiological concentrations of purines and pyrimidines.

Chemistry of biologically important synthetic organoselenium compounds.

Polyamines in rapid growth and cancer

The nucleoli of the adult and embryonic liver, Morris 9121, 8995, 7787, and R-7 hepatomas, and the liver after prolonged aflatoxin B1 treatment were compared with respect to size and ultrastructure. Embryonic liver cells had enlarged nucleoli with well-demarcated fibrillar and granular components of the nucleoli. Cells of Morris Hepatoma 7787, 9121, R-7, and 8995 had enlarged nucleoli. The demarcation of fibrillar and granular components in the nucleolonemas was similar to that of normal liver in the Morris Hepatoma 7787 and was progressively less in Hepatomas 9121, R-7, and 8995.

The ratios of the area containing fibrillar components to the total nucleolar area of normal liver, embryonic liver, and Morris hepatomas were within the same range despite differences in the sizes of the nucleoli.

The morphologic resemblance of the nucleoli of the 7787 hepatoma to that of the normal liver may be related to the greater similarity of the base composition of rapidly labeled nucleolar RNA of this tumor to that of normal liver than that found for other tumors. In liver cells of aflatoxin B1-treated rats, the enlarged nucleoli resembled those of regenerating liver.

From these studies, it appears that the Morris hepatomas contain a spectrum of variation of nucleolar morphology ranging from those of the rapidly growing transplantable tumors to that of normal liver. These data support the view (3) that studies on ultrastructure do not provide diagnostic criteria for tumors, at least with the method of fixation and staining employed in this study.

Comparative studies of the nucleoli of Morris hepatomas, embryonic liver, and aflatoxin B1-treated liver of rats.

Summary Comparative studies on nuclei and chromatin of hepatomas and rat liver were performed because of reports that malignant tumors contain higher amounts of acidic nuclear proteins than nonmalignant tissues. The studies involved the protein composition of nuclei and chromatin, the amounts of total nuclear and chromosomal RNA, the phosphate content of nuclear proteins, thermal denaturation experiments with chromatin preparations, and experiments on the template activities of chromatin in a DNA polymerase system. No differences were found in the chemical composition of nuclei or chromatin between hepatoma 5123C and host liver. Novikoff cells showed increased amounts of residual nuclear protein and total nuclear and chromosomal RNA. The phosphate content of nuclear proteins of hepatoma 5123C was found to be very close to that of host liver. The phosphorylation of the histones and chromosomal nonhistone proteins of Novikoff cells was found to be lower than that of hepatoma 5123C and host liver. Thermal denaturation experiments revealed nearly identical temperatures of half-melting ( T m ) and total hyperchromicities for chromatin preparations of hepatoma 5123C, host liver, and Novikoff cells. The template activities of chromatin of hepatoma 5123C and hepatoma 7800 were found to be lower than the template activities of chromatin of their host livers. Chromatin of Novikoff cells showed a lower template activity than chromatin of normal liver.

Comparative Studies on Nuclei and Chromatin of Hepatomas and Rat Liver

Summary Deamination of deoxycytidylate, deoxyguanylate, and deoxyadenylate, as well as deoxyadenosine and deoxyguanosine, by rat liver and several hepatomas was studied by a method based on the determination by a Conway diffusion technic of the ammonia formed. Several factors affecting the enzyme reactions were considered, and the application of the method to the estimation of deaminase activity in tissues with low activity was demonstrated. By this technic it was shown that normal rat liver had a deoxycytidylate deaminase activity of 46 µmoles deaminated/gm protein/hr. Dunning hepatoma consistently exhibited half this activity, whereas the activity of Reuber and a number of sublines of Morris 5123 tumor were in the normal range. Extremely high activities were found in the McCoy MDAB and Novikoff hepatomas, in confirmation of previous reports. The deamination of deoxyadenylate and deoxyguanylate by tumor and normal tissues was considerable, but, since the activity measured may be the resultant of the combined action of as many as three enzymes, the relationship of purine deoxynucleotide deamination to hepatoma growth cannot be determined until the enzymes are separated. The deamination of deoxyadenosine and deoxyguanosine, on the other hand, is less equivocal, and it was observed that these enzyme activities varied greatly in different hepatomas when compared with normal liver. Because of this and the large differences in deoxycytidylate deaminase activities, it was suggested that each hepatoma may have a unique pattern of deoxynucleotide metabolism.

https://cancerres.aacrjournals.org/content/canres/23/3/454.full.pdf

Some observations on the deamination of deoxynucleotides and deoxynucleosides by normal rat liver and hepatomas.

Summary The activities of glutamine synthetase, glutamine aminotransferase, and transglutaminase have been assayed in a number of hepatomas. No correlation exists between any of the enzyme activities and the growth rate, the chromosome number, or the degree of differentiation of the hepatomas. Glutamine synthetase activity declined with successive transplantations in some hepatoma lines. Adrenalectomy lowered the enzyme activity in young rat liver, and cortisol administration raised it. In adult rat liver, such manipulations had little effect on the enzyme activity. Moreover, the responsiveness of glutamine synthetase in several hepatoma lines to adrenalectomy and cortisol treatment far exceeded that in young rat liver. Cortisol elevated glutamine synthetase activity 14-fold in Hepatoma 7800 grown in intact rats and 20-fold in the same hepatoma grown in adrenalectomized rats. The hormone, however, did not affect the enzyme activity in the host livers of either group. Similar differences in response to cortisol between the enzyme in other hepatomas and that in the host livers have been observed. The induction of glutamine synthetase by cortisol does not appear to arise from an increase in tissue amino acid concentration following the hormonal treatment. In addition, thyroxine enhanced glutamine aminotransferase activity in the 2 hepatoma lines studied but not in the host livers. The action of both cortisol and thyroxine was blocked by actinomycin D when given together with the hormone. However, actinomycin D was devoid of its blocking effect when given after glutamine synthetase had been fully induced by cortisol. Under none of the conditions did the antibiotic affect the enzyme in the host livers. Furthermore, glutamine synthetase in Hepatomas 9618A, 8999, and 7800 also showed a greater sensitivity to protein or amino acid content of the diet than did the enzyme in the host livers. Thus, a series of metabolic modulations (adrenalectomy, administration of cortisol and thyroxine, treatment with actinomycin D, and ingestion of low- and high-protein diets) has demonstrated the responsiveness of the enzymes in several hepatomas and the lack of it in the host livers. We suggest that overresponsiveness by some enzymes in these hepatomas is a manifestation of deranged control mechanisms for synthesis of the enzymes in cells that have reacquired the type of regulation prevailing in liver of the animal during the early period of life.

Responsiveness of glutamine-metabolizing enzymes in Morris hepatomas to metabolic modulations.

Summary Present chromosome data indicate that, among the transplantable Morris rat hepatomas, only six are diploid (9618A, 9633, 7794A, 7800, 9121, and 9098), and only two (9618A, 9633) have a completely normal karyotype. Two previously diploid hepatomas (9618B, 9611B) have recently undergone transition to an aneuploid state. Despite the difficulty in obtaining adequate chromosome preparations from the slow-growing tumor lines, regular reexamination seems indicated on those being used for metabolic studies.

/pdf/chromosomes-of-minimal-deviation-hepatomas-a-further-report-3fdw104xif.pdf

Harold P. Morris

Papers

Comparative studies of the nucleoli of Morris hepatomas, embryonic liver, and aflatoxin B1-treated liver of rats.

Comparative Studies on Nuclei and Chromatin of Hepatomas and Rat Liver

Some observations on the deamination of deoxynucleotides and deoxynucleosides by normal rat liver and hepatomas.

Responsiveness of glutamine-metabolizing enzymes in Morris hepatomas to metabolic modulations.

Chromosomes of "minimal deviation" hepatomas: a further report on diploid tumors.