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

From isotonic extracts of fast-growing Morris hepatoma 3924A, a soluble protein kinase was purified about 25-fold by diethylaminoethyl cellulose column chromatography followed by gel filtration on a Sephadex G-200 column and isoelectrofocusing electrophoresis. The enzyme preparation phosphorylated itself and did not require any added substrate. The reaction was greatly stimulated by H1 histone as well as by polylysine. Polyarginine and other histone fractions were less effective. Spermine and spermidine were slightly active. Acid hydrolysis of the phosphorylated product resulted in the identification of phosphoserine and phosphothreonine in a ratio of about 1.2:1. Analysis of sodium dodecyl sulfate:polyacrylamide gel electrophoresis revealed that histones were not phosphorylated, but endogenous proteins with approximate molecular weights of around 7 × 10 4 were labeled. The enzyme did not show homogeneous size distribution upon gel filtration on a Sephadex column, but the major fraction corresponded to an approximate molecular weight of 2.6 × 10 5 . Nevertheless, the enzyme showed a single isoelectric point of 4.9. K m for adenosine triphosphate was about 4 × 10 -6 m. Apparent K a was 8 βg/ml for polylysine and 16 µg/ml for whole histone. A pH optimum was 7.5 to 8.5. In the absence of polylysine, the enzyme showed a biphasic concentration curve for Mg 2+ with an optimum concentration of 50 to 100 mm, but in the presence of polylysine the curve was normalized and the optimum concentration was 3 to 100 mm. Subcellular fractionation with organic solvents revealed that the enzyme did not represent a leakage of nuclear phosphoproteins into the cytoplasm during isolation procedures. The enzyme was not stimulated or inhibited by cyclic nucleotides and is clearly distinguished from cyclic nucleotide-dependent protein kinases.

https://cancerres.aacrjournals.org/content/canres/38/10/3532.full.pdf

Requirement of Polycations for the Enzymatic Activity of a New Protein Kinase-Substrate Complex from Morris Hepatoma 3924A

A sensitive and reliable procedure was developed for measurement of inorganic pyrophosphatase (PPiase) activity in crude tissue preparations, based on intensification of the ammonium phosphomolybdate color with malachite green, and was applied to normal rat and mouse tissues and to a series of rat hepatic neoplasms. Assays were conducted on the soluble fractions obtained by high-speed centrifugation; these contained >85% of the total activity. Activity was very high in rat and mouse livers, with mean values of 116 and 145 units/g, respectively. Specific activity in rat liver was not changed significantly on prolonged fasting or refeeding; total liver activity fluctuated in parallel with the weight of the organ. Activity in 17- to 21-day fetal liver was one-third to one-fourth that of adult maternal livers and rose to the adult level by 4 to 5 weeks after birth. Regenerating liver over 3 days following partial hepatectomy had the same specific activity as that of the normal, dissected portions. Activity in hepatomas was high although variable, ranging from 13 to 72 units/g, with no clear correlation with growth rate or degree of differentiation. To determine relationships of PPiase to alkaline phosphatase, a comparative study was conducted using starch gel electrophoresis at pH 7.0. Slices of the gel were treated either with pyrophosphate at pH 7.2 or with p-nitrophenyl phosphate at pH 9.0, and phosphate color was developed as mentioned above. All tissues exhibited a major band of pyrophosphatase activity, which was without alkaline phosphate activity. Liver, kidney, and some tumors sporadically displayed two minor bands, the slower of which also contained alkaline phosphatase activity and migrated like purified calf intestinal alkaline phosphatase, which also exhibited low PPiase activity. The faster band was faint, was not always observed, and displayed no alkaline phosphatase activity. Alkaline phosphatase activity was very low in all soluble tissue preparations. These results indicate that the major soluble PPiase is widely distributed in normal tissues and liver neoplasms, and its high activity can account for maintenance of an adequate phosphate pool during rapid cell proliferation. Preliminary data on the crude enzyme present in hepatomas reveal a very low Ks of the order of 6 to 10 µm, and absolute Mg2+ requirement, and a pH optimum of 7.2.

https://cancerres.aacrjournals.org/content/canres/41/5/1866.full.pdf

Activities and properties of inorganic pyrophosphate in normal tissues and hepatic tumors of the rat.

Summary Maximum DNA synthesis occurred later after partial hepatectomy in mouse liver than in rat liver, and there was a similar delay in maximum glycogen depletion. The decline in activities of glycogen synthetase and phosphorylase did not parallel changes in glycogen concentration in the regenerating rat liver, being less pronounced and occurring later after partial hepatectomy. The glycogen concentration of two slowly growing hepatomas (9618A and 7787) was greater than in the rapidly growing hepatomas examined (5123tc and 7777). In vitro assays of tumor glycogen synthetase activity showed a decrease to less than 25% of the activity in normal or host liver. On addition of glucose 6-phosphate this change was less marked, and in the slowest growing hepatoma (9618A) there was no significant difference in activity. Glycogen phosphorylase activity was decreased in the hepatomas, and, most noticeably in the rapidly growing hepatomas, there was an increase in the stimulation of activity by AMP. The effect of cystcinc on glycogen phosphorylase activity in the rapidly growing hepatoma 7777 differed from that in rat liver or gastrocnemius muscle. Acid α-glucosidase activity was increased in the rapidly growing hepatomas but not in regenerating rat liver. It was concluded that glycogen metabolism in slowly growing hepatomas more closely resembles that in normal rat liver than does glycogen metabolism in rapidly growing hepatomas.

Glycogen Metabolism in Regenerating Liver and Liver Neoplasms

Summary The effects of hydrocortisone, glucagon, and adrenalectomy on certain enzymes of hepatomas and the host livers, i.e., tyrosine- a -ketoglutarate transaminase, serine dehydratase, glucose-6-phosphate dehydrogenase, citrate cleavage enzyme, and glucose-6-phosphatase, were studied in Buffalo strain rats bearing Morris hepatomas 9618A, 9633, 7800, or 5123C under controlled feeding and lighting conditions. The purpose of the experiment was to determine whether the hepatomas with diploid chromosome number would respond to hormonal treatments in a manner similar to normal rat liver. The response of tyrosine- a -ketoglutarate transaminase activity to hormones in normal adult rat liver was proportional to the protein content in the diets. The activity of Hepatoma 7800 was increased significantly by hydrocortisone and was decreased by adrenalectomy, independently of dietary protein, but it was not changed by glucagon treatments. Hepatoma 9633 did not show any change in activity after treatment with either hydrocortisone or glucagon, or by the combination. The combined treatment by hydrocortisone and glucagon brought about increased activity of tyrosine transaminase in Hepatoma 9618A. The high or derepressed level of activity in Hepatoma 5123C was decreased after adrenalectomy. Serine dehydratase activity in Hepatoma 7800 increased after the repeated injection of hydrocortisone for 7 days; this was the case in normal adult rat liver. Activity of this enzyme in Hepatomas 9618A and 9633 did not increase even after the combined treatment with hydrocortisone and glucagon. The activity in Hepatoma 5123C decreased in adrenalectomized rats, compared with that in control rats, regardless of dietary protein. Repeated treatments with hydrocortisone brought about significant decreases in the activity of glucose-6-phosphate dehydrogenase in Hepatomas 7800, 9618A, and 9633, just as in normal adult rat liver. Glucagon had no effect on the activity of this enzyme. After adrenalectomy, an increased level of activity in Hepatomas 7800 and 5123C was observed. Contrasted to the variable effect of hydrocortisone on citrate cleavage enzyme in normal adult rat liver, all of the hepatomas assayed showed no change in activity. Hepatoma 7800 showed increased activity of glucose-6-phosphatase after the repeated injection of hydrocortisone, as did normal adult rat liver. The combined treatments of hydrocortisone and glucagon showed an apparent increase in the activity in Hepatoma 9618A but not in Hepatoma 9633. It was of interest to note that the enzyme activities in each hepatoma line responded differently to the hormonal treatments, but the enzyme patterns after hormonal manipulation could be related to the range of activities observed in normal rat liver at different developmental stages. The observations support the concept that neoplasia results from a change that prevents the maturation of a dividing cell to a nondividing adult cell which is responsive to organismic controls. Thus, the question of whether the hepatomas respond to hormonal treatments as normal liver responds must be placed in the context of our knowledge of how immature hepatocytes respond to organismic controls and not in the restricted frame of reference represented by livers from young adult animals.

Systematic oscillations in metabolic activity in rat liver and hepatomas: effect of hydrocortisone, glucagon, and adrenalectomy on diploid and other hepatoma lines.

Three transplantable kidney adenocarcinomas were induced in Buffalo strain rats ingesting 4′-fluoro-4-biphenylacetamide. Although all are comparatively slowly growing, these three transplantable neoplasms have different growth rates. Histologically, they are well-differentiated adenocarcinomas, composed of generally uniform cells resembling kidney tubular cells, and they appear to be only slightly deviated from normal kidney tissue. Focal microscopic lesions similar to the larger neoplasms were noted in other portions of the kidneys in which the tumors developed. No pulmonary metastases have been observed.

Harold P. Morris

Papers

Requirement of Polycations for the Enzymatic Activity of a New Protein Kinase-Substrate Complex from Morris Hepatoma 3924A

Activities and properties of inorganic pyrophosphate in normal tissues and hepatic tumors of the rat.

Glycogen Metabolism in Regenerating Liver and Liver Neoplasms

Systematic oscillations in metabolic activity in rat liver and hepatomas: effect of hydrocortisone, glucagon, and adrenalectomy on diploid and other hepatoma lines.

Transplantable Adenocarcinomas of the Rat Kidney Possessing Different Growth Rates