Embed Size (px)
Citation preview
[CANCER RESEARCH 43. 1019-1023, March 1983]0008-5472/83/0043-0000$02.00
Furine and Pyrimidine Enzymic Programs and Nucleotide Pattern in Sarcoma1
George Weber,2 Michael E. Burt, Robert C. Jackson, Noemi Prajda, May S. Lui, and Eiji Takeda
Laboratory for Experimental Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46223 [G. W., R. C. J., N. P., M. S. L., E. T.], and the SurgeryBranch, National Cancer Institute, NIH, Bethesda, Maryland 20205 [M. E. B.]
ABSTRACT
The purpose of this study was to elucidate the enzymicprogram and nucleotide pattern of a chemically induced, trans-
plantable sarcoma and to compare the biochemical makeupwith that of normal and differentiating skeletal muscle in therat.
The activities of 28 key enzymes of pyrimidine, purine, andcarbohydrate metabolism were determined in the 100,000 xg supernatant fluid or in purified extracts. The concentrationsof the adenosine, guanosine, uridine, and cytidine mono-, di-,and triphosphates were measured by high-pressure liquid chro-matography of samples prepared by the freeze-clamp method.
The results of enzymic and metabolite assays were given innmol/hr/mg protein and nmol/g, respectively, and for comparability were also expressed as percentages of the muscleof adult rat as the reference normal tissue in this study. Thesepercentages denote that the activities in sarcoma or in differentiating muscle were higher or lower than those in the muscleof adult rats.
In pyrimidine metabolism, the specific activities of cytidinediphosphate reducÃase, cytidine triphosphate synthetase, andthymidine kinase increased in the sarcoma 60-, 78-, and 80-
fold over those of the muscle. The activities of the key glycolyticenzymes, hexokinase and phosphofructokinase, increased 7-and 3-fold, whereas that of pyruvate kinase decreased to 35%.The activities of glucose-6-phosphatase and fructose-1,6-di-
phosphatase declined to 42 and 48%, respectively. The activities of enzymes involved in pentose phosphate production andutilization increased, with that of the glucose-6-phosphate de-hydrogenase being elevated 288-fold. The activity of galacto-kinase was unchanged, whereas that of uridine diphosphoglu-
cose pyrophosphorylase decreased to 22%. In purine metabolism, the activities of the first three enzymes of guanosinetriphosphate biosynthesis, inosine monophosphate dehydro-
genase, guanosine monophosphate synthetase, and guanosinemonophosphate kinase, increased 22-, 2-, and 5-fold, respectively. In contrast, the activities of adenylosuccinate lyase andadenosine monophosphate deaminase decreased to 28 and42%. The activities of adenosine deaminase and kinase increased 1.8- and 3.5-fold. The activity of the rate-limitingenzyme of de novo inosine monophosphate biosynthesis, ami-dotransferase, increased 13-fold, whereas that of the rate-limiting purine-catabolic enzyme, xanthine oxidase, decreasedto 54%.
In the sarcoma, the concentrations of adenosine tri-, di-, and
monophosphate decreased to 24, 49, and 76%. In contrast,the pools of guanosine tri-, di-, and monophosphate increased9- to 11-fold, and those of the uridylates were also elevated
1This investigation was supported by USPHS Grants CA-13526, CA-05034.
and CA-10792.2 To whom requests for reprints should be addressed.
Received July 22, 1982; accepted December 3, 1982.
4.5- to 12-fold. The cytidine triphosphate concentration increased 17-fold. In the muscle, the concentrations of cytidinediphosphate, inosine monophosphate, and xanthosine mono-
phosphate were too low for the sensitivity of our method todetect, but these pools were well measurable in the sarcoma.
The enzymic program of sarcoma was distinguished fromthat of the muscle of 6-day-old rats by the quantitatively more
pronounced alterations in the sarcoma. The activities of uridinephosphorylase, hexokinase, 6-phosphogluconate dehydroge-
nase, and adenosine deaminase were higher in sarcoma butwere lower or not significantly altered in 6-day-old muscle as
compared to activities of adult muscle. The activities of adenosine monophosphate deaminase and xanthine oxidase decreased in sarcoma, whereas they were unchanged or increased, respectively, in 6-day-old muscle.
In the sarcoma, important segments of alterations in enzy-
mology of carbohydrate, purine, and pyrimidine metabolismwere identified that proved to be a program shared with thatobserved in chemically induced and virus-derived transplanta-
ble rat and avian hepatocellular carcinomas and in primaryhuman liver, kidney, and colon neoplasms. There were alsosarcoma-specific markers in the enzymic programs and nucleotide patterns that readily distinguish this tumor from otherexamined neoplasms.
The present investigation revealed a formidable biochemicalcapacity for replication in the sarcoma cells. These biochemicalstudies also point out possible targets in the strategy of anti-
cancer drug treatment of sarcoma.
INTRODUCTION
Previous work in this laboratory demonstrated, in a spectrumof chemically induced, transplantable hepatocellular carcinomas of the liver, a transformation- and progression-linked im
balance in the activities of key enzymes of carbohydrate,purine, and pyrimidine metabolism and in the pattern of ribo-
nucleotides and deoxyribonucleoside triphosphates (3, 9, 10).Subsequent studies indicated the presence of the metabolicimbalance in a series of carcinomas of kidney and colon in therat and mouse and, recently, in human renal and colon carcinomas (1,2,12). The purpose of the present investigation wasto answer the following questions. Is the biochemical imbalancediscovered in carcinomas applicable to sarcoma? Are theenzymic indications of an imbalance in the cellular metabolicprograms verifiable by the pattern of nucleotides in sarcoma?Is the biochemical pattern of the sarcoma different from that ofdifferentiating muscle? Is it possible to identify a shared patternof biochemical imbalance in carcinomas and sarcoma? Arethere any sarcoma-specific biochemical alterations?
MATERIALS AND METHODS
For these studies, a methylcholanthrene-induced sarcoma line car
ried in male Fischer (F344) rats (Charles River Laboratories, Portage,
MARCH 1983 1019
on May 14, 2021. © 1983 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from
G. Weber et al.
Mich.) and skeletal muscles from control, normal rats of the same sex,strain, age, and weight were used. The tumor was a rhabdomyosar-
coma; the induction, maintenance, histology, and biological behaviorare described in detail elsewhere.3 This is a fairly rapidly growing
neoplasm which resembles the macroscopic appearance and growthrate of hepatoma 3924A and reaches a diameter of 1.5 cm in about 14days, with death occurring 30 to 34 days after inoculation. The 12- to18-day-old tumor has no necrosis, and it is well suited for the metabolic
studies that were conducted.The animals were inoculated s.c. by injection of 106 viable tumor
cells, and 1 week later the tumor-bearing and control rats were shipped
by air from the National Cancer Institute to Indiana University. All ratswere housed in individual cages in air-conditioned rooms, which were
illuminated daily from 6 a.m. to 7 p.m. Purina laboratory chow andwater were available ad libitum. Rats were always killed between 9 and10 a.m.
Biochemical Methods. Animals were stunned, decapitated, andbled; tumors were excised, and 10% homogenates were prepared inthe appropriate media as reported earlier (1, 2, 13). For the freeze-
clamp studies, the animals received light ether anesthesia, and tumorsand muscles were removed as described elsewhere (1 7).
Preparation of the extracts and methods for measurement of enzymes were described in detail elsewhere (1, 2, 5, 13). Preliminarykinetic studies were carried out to ensure that the enzyme assays wereconducted under linear kinetic conditions, at optimum substrate andactivator concentrations, and that the activities measured were proportionate with the amount of enzyme added and reaction time elapsed.Preparation of the tissue material for determination of concentrationsof ribonucleotides and deoxynucleoside triphosphates by high-pres
sure liquid chromatography and enzymatic methods (3) was citedelsewhere. Protein content was determined by a standard procedure(7).
Expression and Evaluation of Results. Enzymic activities werecalculated as nmol product formed per hr, per g (wet weight) of tissue,per average cell or per mg protein, as specific activity. The concentrations of nucleotides were calculated in nmol per g (wet weight) oftissue.
The results were subjected to statistical evaluation by means of thet test for small samples. Differences between means yielding a probability of less than 5% were considered to be of statistical significance.
RESULTS AND DISCUSSION
Enzymic Programs of Muscle and Sarcoma
The activities of key enzymes of carbohydrate, purine, andpyrimidine metabolism are summarized in Table 1, which provides the means and standard errors of activities observed innormal muscle and the results in the sarcoma as percentagesof the values in muscle. In pyrimidine metabolism, the activitiesof the synthetic enzymes were low as compared to thoseobserved in rat liver (16). In the muscle, the rate-limiting enzyme of CTP biosynthesis, CTP synthetase, had an activityabout one-tenth that in liver. The activity of thymidine kinase
was also low; however, that of the other salvage enzyme,uridine kinase, was the highest in this group of syntheticenzymes. The activity of uridine kinase was 5 times higher thanthat of the enzymes of the de novo synthetic pathway, orotidine5'-monophosphate decarboxylase and orotate phosphoribo-
syltransferase.
3 M. B. Popp, M. E. Burt, and M. F. Brennan. Natural history and cell of origin
of a methylcholanthrene-induced sarcoma in the Fischer 344 rat, submitted forpublication.
In the sarcoma, the activities of all synthetic enzymes examined were very markedly increased as compared to muscle,ranging from a rise of 78- to 80-fold for thymidine kinase andCTP synthetase to increases of 26- and 14-fold for uridine
kinase and uracil phosphoribosyltransferase. These elevationswere much more marked (about 10-fold higher) than were
those observed in the rapidly growing liver tumors comparedto the resting liver (16).
In carbohydrate metabolism in the muscle, the activities ofthe key glycolytic enzymes, hexokinase, phosphofructokinase,and pyruvate kinase, were higher than those in rat liver (11).This is expected in view of the well-known glycolytic capacity
of skeletal muscle. In the sarcoma, the activities of phosphofructokinase and hexokinase increased 3- to 7-fold, which is in
line with observations made in hepatic carcinomas of similarrapid growth rates (11 ). In contrast to results in hepatomas,the activity of pyruvate kinase, which is orders of magnitudehigher than any other enzyme that we have studied, wasdecreased to one-third of that observed in the control muscle.
In muscle, the gluconeogenic enzymes, glucose-6-phospha-tase and fructose-1,6-diphosphatase, were present only in low
activities, which were further decreased to 42 to 48% in thesarcoma. These results are in line with the decline in activitiesof gluconeogenic enzymes first reported in hepatomas (11 ).
In pentose phosphate metabolism in the muscle, the activityof glucose-6-phosphate dehydrogenase proved to be rate lim
iting, being 10 times lower than that of the subsequent enzyme,6-phosphogluconate dehydrogenase. The activity of glucose-6-phosphate dehydrogenase was the lowest among the enzymes of carbohydrate metabolism examined in this study.Therefore, it is interesting that in the sarcoma the activity ofthis dehydrogenase was increased the most markedly of all theenzymes assayed, i.e., 288-fold over the value of normal control muscle. The 6-phosphogluconate dehydrogenase activitywas elevated 12-fold. Transaldolase, which channels fructose6-phosphate into ribose 5-phosphate biosynthesis, in the muscle had an activity twice as high as that of 6-phosphogluconatedehydrogenase, and the activity increased 7.7-fold in the sarcoma. The enzyme that utilized ribose 5-phosphate for phos-phoribosylpyrophosphate biosynthesis, phosphoribosyl pyro-
phosphate synthetase, also had low activity in the muscle, butit increased only 1.5-fold in the sarcoma.
In purine metabolism among the synthetic enzymes, theactivity of IMP dehydrogenase was the lowest, resembling thatin liver (5). However, the muscle activity was much lower thanthat in the rat liver. In the sarcoma, the dehydrogenase activityincreased 22-fold, the highest rise among all the purine en
zymes examined. The activities of the enzymes involved in GTPbiosynthesis subsequent to the action of IMP dehydrogenase,GMP synthetase and GMP kinase, were orders of magnitudehigher than that of the rate-limiting enzyme, the dehydrogenase. These enzymic activities increased in the sarcoma to 2-to 5-fold the values of the muscle. It is interesting that the
activities of the enzymes of the purine cycle, adenylosuccinaseand AMP deaminase, were decreased in the sarcoma, indicating that this cycle which may be a characteristic liver andmuscle function was decreased in the sarcoma. The activity ofAMP deaminase was the highest among the purine enzymes inthe muscle. The activities of enzymes involved in adenosinemetabolism, adenosine deaminase and kinase, were also high,but these activities further increased 1.8- and 3.5-fold. This
1020 CANCER RESEARCH VOL. 43
on May 14, 2021. © 1983 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from
Biochemistry of Rat Sarcoma
Table 1
Enzymic programs of muscle and sarcoma in rat
Metabolic areas andenzymesPyrimidineCDP
reducÃaseThymidineklnaseCTPsynthetaseOrotidine
5'-monophosphatedecar-boxylaseOrotate
phosphoribosyltransferaseUracilphosphoribosyltransferaseUridinekinaseUridine
phosphorylaseGlycolysisHexokinasePhosphofructokinasePyruvate
kinaseGluconeogenesisGlucose-6-phosphataseFructose-1
,6-diphosphatasePentose
phosphateGlucose-6-phosphatedehydroge-nase6-Phosphogluconate
dehydroge-naseTransaldolasePhosphoribosyl
pyrophosphate synthetaseEC
no.1.17.4.12.7.1.216.3.4.24.1.1.232.4.2.102.4.2.92.7.1.482.4.2.32.7.1.12.7.1.112.7.1.403.1.3.93.1.3.111.1.1.491.1.1.442.2.1.22.7.6.1Adultmuscle
(nmol/hr/mgprotein)0.0430.280.483.753.900.8019.800.18478.03,340.0488,000.01,130.01,190.057.0598.01.180.076.0±±±±±±±±±±±±±±±±±0.005a0.040.060.090.450.170.830.0032.0190.012,000.090.070.01.015.0110.02.5Sarcoma(%
ofmuscle)5,95368,004"7.768"5,086"3,589"3,425"2,626"1,378"686"314"35"42"48"28,825*1.154"770"158"6-day-ol'lmusclo(% of adult
muscle)i,noo"600"376"1,431"976"1,722"5847"18"1.215"80"175"
GalactoseGalactokinase 2.7.1.6Uridine diphosphoglucose pyro- 2.7.7.9
phosphorylase
PurineIMP dehydrogenase 1.2.1.14GMP synthetase 6.3.5.2GMP kinase 2.7.4.8Adenylosuccinate lyase 6.3.4.4AMP deaminase 3.5.4.6Adenosine deaminase 3.5.4.4Adenosine kinase 2.7.1.20Amidotransferase 2.4.2.14Xanthine oxidase 1.2.3.2
3.917.4
0.038 ±14.5 ±
840.0520.0
18,640.0955.0104.0
7.84.9 ±
0.41.5
0.0070.4
37.010.0
149.035.0
0.044.01.0
9522"
2,160218"524"
28"
<177"351 "
1,345"54"
504"
144115
188"200"
Mean ±S.E. of 4 or more experiments.' Significantly different from muscle of adult rats (p < 0.05).
behavior is in contrast with that in hepatic carcinoma where inthe rapidly growing tumors the activity of adenosine deaminasewas increased 3- to 4.5-fold and that of adenosine kinase
decreased to less than 20% of that observed in the control liver(4).
The activity of the first committed enzyme of de novo purinebiosynthesis, amidophosphoribosyltransferase (amidotransfer-ase), in the sarcoma was markedly increased (13-fold),whereas that of the rate-limiting catabolic enzyme, xanthine
oxidase, was decreased to 54%. As a result, the ratio ofamidotransferase to xanthine oxidase was markedly elevated.
Enzymic Program of Differentiating Muscle
The enzymic program of differentiating muscle of the rat(Table 1) shows some similarities to and also sharp differencesfrom that of the sarcoma. The activities of the pyrimidine-synthetic enzymes were increased in comparison with normalmuscle, but to a smaller extent than those of the sarcoma.However, uridine phosphorylase activity was decreased. The
activity of hexokinase was decreased to 47%, whereas in thesarcoma it was increased to 686%. The pyruvate kinase activitywas 18%, whereas in the sarcoma it was 35%, of the normalmuscle. Minor increases were observed in the activities ofglucose-6-phosphate dehydrogenase and transaldolase. However, the activity of 6-phosphogluconate dehydrogenase wasdecreased, whereas in the sarcoma it was elevated 12-fold. In
purine metabolism, the GMP kinase activity was as high as inthe sarcoma. However, the activities of AMP deaminase andadenosine deaminase in the developing muscle were the sameas in normal muscle, whereas in sarcoma the first one decreased and the latter increased. In the 6-day-old muscle, theamidotransferase activity was 2-fold higher whereas in thesarcoma it was 13-fold higher than in the normal muscle. In thesarcoma, the xanthine oxidase activity was decreased,whereas it was high in the differentiating muscle. Thus, theenzymic program of the sarcoma can be readily separated fromthat of the differentiating muscle through the quantitativelymore pronounced alterations in the sarcoma and by the different behavior of uridine phosphorylase, hexokinase, 6-phos-
MARCH 1983 1021
on May 14, 2021. © 1983 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from
G. Weber et al.
phogluconate dehydrogenase, AMP deaminase, adenosine de-
aminase, and xanthine oxidase.
Ribonucleotide Pattern in Muscle and Sarcoma
The overall pattern of purine and pyrimidine ribonucleotidesin muscle (Table 2) resembled that of liver in that the concentrations of adenylates were 2 orders of magnitude higher thanthose of the other nucleotides and the concentrations of cyti-
dylates were the lowest (3). Particularly low CTP concentrationwas found in the muscle, the other nucleotides (CDP, IMP, andXMP) being too low to measure with accuracy by currentmethods. The strikingly high concentrations of ATP and ADPwere in line with expectations for these nucleotides because oftheir vital role in muscle function.
Comparison of the purine and pyrimidine ribonucleotide concentrations shows a characteristic pattern in the sarcoma. Theconcentrations of ATP, ADP, and AMP and total adenylates inthe sarcoma decreased to 24, 49, 76, and 32%, respectively,of those observed in normal muscle. The decrease in concentration of adenylates is similar to that in renal cell carcinomas(18) and hepatomas (3, 17) in the rat. By contrast, the concentrations of GTP, GDP, GMP, and total guanylates were verymarkedly increased over those in muscle. The 9-fold increasein concentration of GTP and the elevation in that of totalguanylates (14-fold) were in marked contrast with values in rat
liver carcinomas which were in the normal range of the controlliver. The concentrations of DTP, UDP, the UDP sugars, andtotal uridylates were markedly increased in the sarcoma butwere not significantly altered in the rapidly growing hepatoma.The 17-fold increase in CTP concentration is the most markedamong the ribonucleotides in the sarcoma; a 4- to 5-fold
elevation was observed in the rapidly growing hepatoma3924A.
The decreased concentration of adenylates is in line with thedecrease in the activities of enzymes of de novo ATP production in the sarcoma (Table 2). The increased concentrations ofGTP, GDP, and GMP reflect the elevated activities of IMP
Table 2
Purine and pyrimidine ribonucleotides in rat sarcoma and skeletal muscle
NucleotidesATPADPAMPSAAdenylate
chargeGTPGDPGMPEGUTPUDPUMPUDP
sugarsSUCTPCDPIMPXMPnmol/g.Muscle4725151021864530.85191203162170971763000±±±±±±+±±±±311a70574374254118193wet
wtSarcoma113074316520380.74188134122444282207149513115151395519±±±±±±±±±±±±±±±±15737201079833282434113831537%
ofmuscle24°49"7632b87989"111661432"4546121
76529b654"17006
Mean ±S.E. of 4 or more experiments.' Significantly different from muscle (p < 0.05).
dehydrogenase, GMP synthetase, and GMP kinase (Table 1).The elevated concentrations of UTP, UDP, and UMP are ingood agreement with the marked increase in the activities ofenzymes involved in the de novo and salvage pathways ofuridylate biosynthesis. The increased concentration of CTPreflects the elevation in the activity of the rate-limiting enzyme
of biosynthesis, CTP synthetase (Table 1).
Identification of Shared Programs in Neoplasms and Tumor-specific Enzymic and Metabolic Pattern in Sarcoma
Shared Programs in Different Types of Neoplastic Cells.In elucidating the biochemical strategy of gene logic, it wasreported from this laboratory that there are shared programs inthe enzymic and metabolic imbalance that are displayed invarious types of neoplasms (9, 10, 14). Evidence was presented that important segments of alterations in enzymology ofcarbohydrate, purine, pyrimidine, and other metabolic areasoccurred in chemically induced and virus-derived, transplant-
able rat, mouse, and avian tumors and in primary human liverand kidney and colon neoplasms (1, 6, 8, 15). Three majoraspects of gene logic were identified in the various tumors (14).
Reciprocal regulation plays a vital role in control of the rateand direction of opposing metabolic pathways by determiningthe amounts of antagonistic key enzymes (14). This metabolicimbalance amplifies the metabolic capabilities of the tumorcells. Such a pattern was observed in the present investigationin the sarcoma in the elevation in activity of the syntheticenzyme, amidotransferase, and the decline in that of the opposing catabolic enzyme, xanthine oxidase. This reciprocalregulation resulted in a 31-fold increase in the ratio of theactivities of the opposing enzymes of purine metabolism whichis more marked than the rise observed for this enzyme ratio inother tumors.
A second principle that we identified in purine and pyrimidinemetabolism was the relationship of the extent of rise in activityof an enzyme in a tumor compared with the absolute activityobserved in the homologous normal tissue of origin. An example of this relationship is in human colon tumor where theactivities of thymidine kinase and CTP synthetase which werethe lowest in normal colon mucosa were increased the mostmarkedly in the neoplasms (1). A similar relationship holds inthe sarcoma where thymidine kinase, CTP synthetase, andCDP reducÃase had the lowest activities in the muscle, butthese activities were increased to the greatest extent amongthe pyrimidine-synthetic enzymes in the sarcoma. In purinemetabolism in the muscle, the activity of IMP dehydrogenasewas the lowest; in the sarcoma, it was increased the mostmarkedly among the enzymes of purine biosynthesis.
Observations in an array of 14 different rat, mouse, avian,and human tumors indicated the operation of an integratedprogram of enzymic and metabolic imbalance that conferredselective advantages to the cancer cells (6, 8, 9, 10, 14). Inthe sarcoma, we confirmed the presence of a coordinatedpattern of alterations in the activities of key enzymes yieldinga highly meaningful picture (Tables 1 and 2).
Tumor-specific Differences. In parallel with striking similarities in the overall biochemical strategy of different cancercells, we also expect organ- and cell-specific alterations in
neoplasms of different cellular origin, and we reported suchdifferences for the various tumor systems (1, 14). In the sar-
1022 CANCER RESEARCH VOL. 43
on May 14, 2021. © 1983 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from
Biochemistry of Rat Sarcoma
coma, a striking contrast with other neoplasms was the decrease in activity of pyruvate kinase which was ubiquitouslyincreased in all other tumors examined thus far. In sarcoma,galactokinase activity did not increase, but it was elevated 4-
fold in human colon carcinoma. In sarcoma, the activities ofAMP deaminase and adenylosuccinase decreased, but theyincreased in liver and kidney tumors. The activity of adenosinekinase that was low in rapidly growing hepatomas showed a3.5-fold increase in the sarcoma. These alterations provide apattern of sarcoma-specific markers that distinguishes the en-
zymic features of this tumor from those of any others that wehave examined thus far. There are also differences in thenucleotide pattern where the marked increases in concentrations of guanylates and uridylates contrast with the normal livervalues observed in hepatocellular carcinomas. In sarcoma, the17-fold increase of CTP concentration was quantitatively farbeyond the rise in hepatoma 3924A (4- to 5-fold). Thesedifferences assist in characterizing the metabolic individualityof the sarcoma and in the biochemical differential diagnosis ofthis tumor.
Selective Advantages Conferred to Sarcoma Cells by theEnzymic and Metabolic Imbalance. The biological malignancyand rapid growth rate of the sarcoma are reflected in thepronounced elevations in the activities of key enzymes ofpyrimidine and purine biosynthesis and in the decrease incatabolic capacity (9, 10). The increased activities of keyenzymes of glycolysis and pentose phosphate production andutilization should provide an increased capability for the production of ribose 5-phosphate and phosphoribosyl pyrophos-
phate.The markedly enlarged pools of guanylates, uridylates, and
cytidylates should provide a stepped-up capability for nucleic
acid production, in particular, the provision of substrate forribonucleotide reducÃasefor the de novo biosynthesis of deoxy-
nucleoside triphosphates. The markedly increased capacitiesof the salvage pathways, as shown by elevated activities ofthymidine kinase (80-fold) and uridine kinase (26-fold), would
contribute strongly to the increased potential for nucleic acidbiosynthesis. The enzymic and metabolic imbalance discovered in the sarcoma should confer selective advantages tothese cancer cells. The pronounced enzymic and metabolicimbalance and particularly the increase in both de novo andsalvage enzymic activities explain, in part at least, the difficulties encountered in the chemotherapeutic control of this malignant neoplasm.
Relevance of Enzymology of Sarcoma to the Design ofAnticancer Drug Treatment. The difficulties in achieving lasting remissions in experimental or human sarcomas by inhibitorsof the de novo pathways of pyrimidine metabolism may beexplained, in part at least, by the operation and increasedactivities of the powerful salvage enzymes, uridine kinase,uracil phosphoribosyltransferase, and thymidine kinase, whichwere markedly elevated in the sarcoma. The stepped-up activity of uridine-cytidine kinase is particularly important becausethis enzyme provides the uridylates, the pool of which is profoundly enlarged in the sarcoma. This enzyme also activatescytidine and yields CMP. Thus, through the elevated activity of
this enzyme, an inhibition by drugs of the final common pathwayof CTP biosynthesis, CTP synthetase (e.g., by glutamine antagonists or competitive inhibitors), also would be circumvented.The marked elevation in thymidine kinase activity provides aheightened capacity for production of thymidylates which arealso crucial for DNA biosynthesis. In the design of combinationchemotherapy of sarcoma, there is a need for agents that inaddition to inhibition of the de novo pathways would block theactivities of the salvage synthetic processes. The present studies, while revealing the formidable biochemical capacities displayed by sarcoma cells, also point out possible approaches inthe strategy of anticancer drug treatment of this neoplasm.
REFERENCES
1. Dentón, J. E., Lui, M. S., Aoki. T., Sebolt. J., Takeda, E., Eble, J. N., Glover,J.L., and Weber, G. Enzymology of pyrimidine and carbohydrate metabolismin human colon carcinomas. Cancer Res., 42: 1176-1183, 1982.
2. Jackson, R. C., Goulding, F. J., and Weber, G. Enzymes of purine metabolism in human and rat renal cortex and renal cell carcinoma. J. Nati. CancerInst., 62. 749-754. 1979.
3. Jackson, R. C., Lui, M. S., Boritzki, T. J., Morris, H. P.. and Weber, G.Purine and pyrimidine nucleotide patterns of normal, differentiating andregenerating liver and of hepatomas in rats. Cancer Res., 40: 1286-1291,1980.
4. Jackson, R. C.. Morris, H. P., and Weber, G. Enzymes of the purineribonucleotide cycle in rat hepatomas and kidney tumors. Cancer Res., 37:3057-3065, 1977.
5. Jackson, R. C., Morris, H. P., and Weber, G. Partial purification, propertiesand regulation of inosine 5'-phosphate dehydrogenase in normal and malignant rat tissues. Biochem. J.. 166: 1-10, 1977.
6. Kovalszky, I , Jeney. A., Asbot, R., and Lapis, K. Biochemistry and enzymeinduction in MC-29 virus-induced transplantable avian hepatoma. CancerRes., 36. 2140-2145, 1976.
7. Lowry, O. H., Rosebrough, N. J., Farr, A. L., and Randall, R. J. Proteinmeasurement with the Folin phenol reagent. J. Biol. Chem., 193: 265-275,
1951.8. Prajda, N.. Eckhardt, S., Suba, Z., and Lapis. K. Biochemical behavior of
MC-29 virus-induced transplantable chicken hepatoma. J. Toxicol. Environ.Health, 5. 503-508, 1979.
9. Weber, G. Enzymology of cancer cells, Part 1. N. Engl. J. Med.. 296: 486-493. 1977.
10. Weber. G. Enzymology of cancer cells. Part 2. N. Engl. J. Med.. 296: 541-551, 1977.
11. Weber, G. Differential carbohydrate metabolism in tumor and host. In: M. S.Arnott, J. van Eys, and Y.-M. Wang (eds.). Molecular Interrelations ofNutrition and Cancer (UT System Cancer Center 34th Annual Symposiumon Fundamental Cancer Research), pp. 191 -208. New York: Raven Press,1982.
12. Weber, G., Goulding, F. J., Jackson, R. C.. and Eble, J. N. Biochemistry ofhuman renal cell carcinoma. In: W. Davis and K. R. Harrap (eds.). Characterization and Treatment of Human Tumours, pp. 227-234. Amsterdam:Excerpta Medica, 1978.
13. Weber, G., Hager, J. C., Lui, M. S., Prajda, N., Tzeng, O. Y., Jackson, R. C..Takeda, E., and Eble, J. N. Biochemical programs of slowly and rapidlygrowing human colon carcinoma xenografts. Cancer Res., 41: 854-859,
1981.14. Weber. G., Lui, M. S., Takeda, E., and Dentón, J. E. Enzymology of human
colon tumors. Life Sci., 27: 793-799, 1980.15. Weber, G., Olah. E., Lui, M. S.. Kizaki, H., Tzeng, D. Y., and Takeda, E.
Biochemical commitment to replication in cancer cells. Adv. Enzyme Regul.,18: 3-26, 1980.
16. Weber, G., Shiotani, T., Kizaki, H., Tzeng, D., Williams. J. C., and Gladstone,N. Biochemical strategy of the genome as expressed in regulation of pyrimidine metabolism. Adv. Enzyme Regul., 76: 3-19, 1978.
17. Weber, G., Stubbs, M., and Morris, H. P. Metabolism of hepatomas ofdifferent growth rates in situ and during ischemia. Cancer Res., 37. 2177-2183, 1971.
18. Williamson, D. H., Krebs, H. A.. Stubbs. M., Page, M. A., Morris. H. P., andWeber, G. Metabolism of renal tumors in situ and during ischemia. CancerRes., 30: 2049-2054. 1970.
MARCH 1983 1023
on May 14, 2021. © 1983 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from
1983;43:1019-1023. Cancer Res George Weber, Michael E. Burt, Robert C. Jackson, et al. Pattern in SarcomaPurine and Pyrimidine Enzymic Programs and Nucleotide
Updated version
http://cancerres.aacrjournals.org/content/43/3/1019
Access the most recent version of this article at:
E-mail alerts related to this article or journal.Sign up to receive free email-alerts
Subscriptions
Reprints and
To order reprints of this article or to subscribe to the journal, contact the AACR Publications
Permissions
Rightslink site. Click on "Request Permissions" which will take you to the Copyright Clearance Center's (CCC)
.http://cancerres.aacrjournals.org/content/43/3/1019To request permission to re-use all or part of this article, use this link
on May 14, 2021. © 1983 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from
