Mammary Tumor Regression

Role of site-selective cAMP analogs in the control and reversal of malignancy

Two isoforms of cAMP receptor protein, RI and RII, the regulatory subunits of cAMP-dependent protein kinase, transduce opposite signals, the RI being stimulatory and the RII being inhibitory of cell proliferation. In normal cells RI and RII exist at a specific physiological ratio whereas in cancer cells such physiological balance of these receptor proteins is disrupted. Reversal and suppression of malignancy can be achieved when the physiologic ratio of these intracellular signal transducers of cAMP is restored as shown by the use of site-selective cAMP analogs, antisense oligodeoxynucleotides or gene transfer, suggesting new approaches to cancer control.

Effects of 3-chloromethylthiochromone-1,1-dioxide on nucleic acid, protein, and aerobic and anaerobic metabolism of Ehrlich ascites tumor cells

3-Chloromethylthiochromone-1,1-dioxide was observed to be a potent inhibitor of Ehrlich ascites carcinoma growth and a moderate inhibitor of P-388 lymphocytic leukemia growth at 10 mg/kg/day. Preliminary in vitro studies showed that the agents significantly inhibited RNA and DNA synthesis in Ehrlich ascites cells. In vivo studies after dosing on Days 6, 7, and 8 demonstrated the same reductions in nucleic acid synthesis and a moderate reduction in protein synthesis. The primary site of nucleic acid synthesis, which was blocked by 3-chloromethylthiochromone, was at orotidine monophosphate decarboxylase in the primidine pathway. Other enzymes, in anaerobic and aerobic glycolysis, which were blocked include hexokinase, phosphofructokinase, succinic and alpha-ketoglutarate dehydrogenases, as well as States 3 and 4 of oxidative phosphorylation.

3,4-bis(3'-hydroxyphenyl)hexane--a new mammary tumor-inhibiting compound. Studies on the mechanism of action on the DMBA-induced, hormone-dependent mammary tumor of the rat

Biochemical properties, such as the activities of eight carbohydrate-metabolism-linked enzymes and four acid hydrolases, and histological characteristics of growing and regressing DMBA-induced mammary tumors of the SD-rat after ovariectomy or treatment of the host with hexesterol, tamoxifen, and 3,4-bis(3'-hydroxyphenyl)hexane were determined. Significant differences were found between growing and regressing tumors regardless of the treatment animals had been subjected to. Only few differences in biochemical parameters could be found within the group of tumors regressing due to the applied therapy. The histological signs of regressing tumors were very diverse, but no phenomenon typical of a specific treatment could be found. It cannot be decided whether the partial antiestrogen, 3,4-bis(3'-hydroxyphenyl)hexane unfolds its antimammary tumor activity by means of its estrogenic or its antiestrogenic potency. The hypothesis that estrogens inhibit mammary tumor growth by directing neoplastic cell metabolism toward secretion is not supported by these findings.

Antitumor agents XLVII: The effects of bisbrusatolyl malonate on P-388 lymphocytic leukemia cell metabolism

Bisbrusatolyl malonate, which was shown previously to be active against P-388 lymphocytic leukemia cell growth, was investigated for inhibitory effects on nucleic acid and protein synthesis. DNA and RNA synthesis as well as protein synthesis were markedly inhibited at 10,25, and 50 mu mole final concentrations in vitro. The major sites of inhibition of nucleic acid synthesis appeared to be DNA polymerase, messenger and transfer RNA polymerases, orotidine-5'-monophosphate decarboxylase, phosphoribosyl pyrophosphate amino transferase, and dihydrofolate reductase. Moderate inhibition of nucleotide kinase activities and oxidative phosphorylation processes occurred after drug treatment. Cyclic adenosine monophosphate levels were reduced. Protein synthesis was inhibited during the elongation step of peptide synthesis. The data suggested that bisbrusatolyl malonate interfered with the peptide bond formation. However, the ongoing polypeptide synthesis must be completed before the drug can bind to the ribosome effectively.

Enzymatic and ultrastructural study of lysosomes in rats bearing radiation-induced thyroid follicular carcinoma

Radiation-induced well-differentiated and poorly differentiated follicular thyroid cancers were transplanted into the intrascapular fat pads of male Fisher 144 rats. The tumors grew in the recipient rats and after a time interval were removed and studied along with normal rat thyroids for lysosomal activity and ultrastructural characteristics. Plasma from experimental and control rats was also studied for lysosomal activity. Rats with radiation-induced thyroid carcinoma had a decrease in growth rate compared with normal rats. There was no significant increase in plasma lysosomal enzymes in the experimental rats. Well-differentiated thyroid carcinomatous tissue showed increased total activities of lysosomal enzymes as well as a difference in subcellular distribution compared with normal and poorly differentiated carcinomatous tissue. Electron microscopy of normal and carcinomatous tissue demonstrated the greatest number of lysosomes in the well-differentiated carcinoma and the fewest in the poorly differentiated carcinoma.

Effects of cis-malonato-diammino platinum (II) on P-388 lymphocytic leukemia cell metabolism

cis-Malonato-diammino platinum(II) significantly inhibited P-388 lymphocytic leukemia cell proliferation at 10 mg/kg/day. Incorporation studies showed that DNA synthesis was inhibited following in vivo drug therapy. The major inhibitory effects appeared to be on thymidine kinase and dihydrofolate reductase activities and on overall purine synthesis, with marginal effects on DNA polymerase and ribonucleotide reductase activities. In addition to the DNA inhibition, a marked increase in cyclic adenosine 3',5'-monophosphate levels was noted, which correlated with a rapid decrease in histone phosphorylation. Other minor effects of the drug included significant reduction of proteolytic activity, suppression of States 4 and 3 respiration, and an increase in adenosine triphosphatase and acid phosphatase activities of P-388 cells.

Antitumor agents XLI: Effects of eupaformosanin on nucleic acid, protein, and anaerobic and aerobic glycolytic metabolism of Ehrlich ascites cells

The major effect of eupaformosanin as an antineoplastic agent on Ehrlich ascites cell metabolism was to inhibit deoxyribonucleic acid synthesis, specifically at deoxyribonucleic acid polymerase and thymidylate synthetase enzymatic sites. Both pyrimidine and purine systems of Ehrlich ascites were marginally inhibited. Ribonucleic acid synthesis and messenger and ribosomal polymerase activities also were suppressed. Cyclic adenosine monophosphate levels were increased significantly, which correlated with the drastic reduction of histone phosphorylation. Eupaformosanin also suppressed a number of glycolytic and Krebs cycle enzymes as well as oxidative phosphorylation in vitro. All of the inhibited enzymes are known thiol-bearing enzymes that can undergo a Michael-type addition with the alpha-methylene-gamma-lactone moiety of eupaformosanin, as shown with other sesquiterpene lactones.

Antitumor agents. XXXIV: Mechanism of action of bruceoside A and brusatol on nucleic acid metabolism of P-388 lymphocytic leukemia cells

The quassinoids bruceantin, brucein D, brucein E, bruceoside A, and brusatol significantly inhibited P-388 lymphocytic leukemic cell RNA and protein synthesis in tissue culture. However, DNA synthesis inhibition seemed to correlate more directly with the anti-neoplastic activity of these compounds in the in vivo P-338 survival system. In vitro, brusatol and bruceoside A marginally inhibited 10-day P-388 lymphocytic leukemia DNA polymerase, RNA polymerase, thymidylate synthetase, dihydrofolate reductase, phosphoribosyl pyrophosphate aminotransferase, and cathepsin protease activities. In vivo studies demonstrated similar inhibition and elevated cyclic AMP levels, correlating positively with the antineoplastic activity of individual compounds. Purine synthesis was inhibited drastically by brusatol in vivo, and one key inhibition site in purine synthesis was at phosphoribosyl pyrophosphate aminotransferase, the regulatory enzyme. Histone phosphorylation and ribonucleotide reductase activity also were inhibited marginally by brusatol.

Boron betaine analogs: antitumor activity and effects on Ehrlich ascites tumor cell metabolism

Several newly synthesized boron betaine analogs had antitumor activity in Ehrlich ascites, Walker 256 ascites carcinosarcoma, and Lewis lung screens and marginal activity in the B-16 melanotic melanoma screen. In vivo testing demonstrated that trimethylamine-cyanoborane inhibied Ehrlich ascites cell DNA and protein syntheses as well as gene modulation by chromatin protein phosphorylation and methylation. Trimethylamine-cyanoborane increased cyclic-AMP levels. In vitro testing showed that nuclear DNA polymerase, thymidylate synthetase, S-adenosylmethyltransferase, nonhistone chromatin methylation, deoxyribonuclease, ribonuclease, and cathepsin were inhibited by the boron analogs. These compounds did not demonstrate high antitumor activity at the doses employed, but blockage of methyl transfer from S-adenosylmethionine was established as a feasible method for controlling cell proliferation.

Antineoplastic agents III: effects of dibromoethyl and vinyl esters of N-benzyloxycarbonyl-l-phenylalanine on Ehrlich ascites tumor cell metabolism

Evidence is presented that N-benzyloxycarbonyl-L-phenylalanine vinyl ester and 1,2-dibromoethyl ester are inhibitors of Walker 256 carcinosarcoma and Ehrlich ascites carcinoma tumor growth. The major effects of these two agents on Ehrlich ascites cell metabolism were the inhibition of deoxyribonucleic acid and protein synthesis and the alteration of cellular regulatory processes controlling cytokinetics. Deoxynucleotide (purine) kinase enzymes appeared to be the focal site for inhibition of deoxyribonucleic acid synthesis with marginal inhibition of thymidylate synthetase activity. Cyclic adenosine monophosphate levels were elevated by drug treatment whereas chromatin protein phosphorylation, cell respiration, and lysosomal activities were inhibited. N-Benzyloxycarbonyl-L-phenylalanine 1,2-dibromoethyl ester was a latent in vitro chymotrypsin inhibitor. Some preliminary evidence suggests that these activated esters may inhibit cellular enzymatic activity by alkylating imidazole and lysine residues of proteins.

Dibutyryl cyclic AMP mimics ovariectomy: nuclear protein phosphorylation in mammary tumor regression

Growth of mammary carcinoma induced by 7,12-dimethyl-benz(a) anthracene is arrested by either ovariectomy or treatment with N6,O2-dibutyryl cyclic adenosine 3',5'-monophosphate (dibutyryl cyclic AMP). When this occurs, a new nonhistone protein species becomes the predominant endogenous substrate of cyclic AMP-dependent protein kinase in the tumor nuclei. Phosphorylation of this regression-associated protein ceases when resumption of tumor growth is induced by either the injection of 17 beta-estradiol or cessation of dibutyryl cyclic AMP treatment. Thus phosphorylation of regression-associated protein may play a role in the regression of hormone-dependent mammary tumors.

Sesquiterpene antitumor agents: inhibitors of cellular metabolism

Helenalin and tenulin injected into CF1 male mice bearing Ehrlich ascites tumors inhibit DNA synthesis and DNA polymerase enzymatic activity in the tumor cells. Helenalin inhibited protein synthesis. Both drugs increased the concentration of adenosine 3',5'-monophosphate, and interfered with glycolytic and mitochondrial energy processes. Cholesterol synthesis was also inhibited, resulting in lower serum cholesterol levels in tumor-bearing animals. Data obtained in vitro indicate that the cyclopentenone-bearing sesquiterpene lactone and related compounds do not alkylate puring bases of nucleic acids but rather undergo a Michael-type addition reaction with the sulfhydryl groups of reduced glutathione and l-cysteine. Thus, the inhibition of cellular enzyme activities and metabolism that has been observed with these drugs might be explained by the occurrence of a Michael-type teaction.

Biochemical changes during regression and regrowth of hormone-dependent GR mouse mammary tumors

Discontinuation of recommencement of estrone-progesterone treatment causes regression and regrowth, respectively, of transplantable hormone-dependent GR mouse mammary tumors. This tumor model was found convenient for the demonstration of hormonal responses in hormone-dependent mouse mammary tumor cells. Tumor regression was palpable 2 days after discontinuation of hormonal treatment and tumors reached half their size within 3-6 days. At this point, hormones were readministered and 2-4 days later the tumors had grown to their preregression size. In the growing and regressing tumor we have investigated: (1) the content of RNA, DNA and protein per g wet weight, (2) in vivo incorporation for 45 min of 32P-orthophosphate into RNA and DNA and the 35S-methionine incorporation into protine; (3) SDS polyacrylamide gel electrophoresis of soluble proteins after in vivo incorporation of 14C- and 3H-leucine. The RNA content per g wet weight was found to decrease during regression and to increase during regrowth. DNA and protein content showed no variation. RNA/DNA ratio thus varied in parallel to the RNA content. The precuursor incorporation into all three macromolecular species decreased during regression. The incorporation into DNA showed the most pronounced decrease. After readministration of hormones, regrowth was accompanied by a rapid increase in precursor incorporation into RNA, while the incorporation into DNA showed a lag of 1 to 2 days. SDS polyacrylamide gel electrophoresis was carried out with soluble proteins labelled in vivo with 14C- and 3H-leucine during regression and regrowth, respectively. No differences in 14C/3H ratios could be demonstrated for the major fractions detectable in the electropherogram.

A preliminary study of elevated alkaline phosphatase and cathepsin in bronchial aspirates of patients with lung cancer and bronchitis

The measurement of acid and alkaline phosphatase and cathepsin activities in bronchial aspirates obtained through bronchoscopy from a series of 75 patients suggests a procedure that may have value as a routine diagnostic examination. Using this approach, seven patients with neoplasms in the lung showed elevated levels of alkaline phosphatase and cathepsin in bronchial aspirates without elevation in acid phosphatase activity.

In vivo inhibition of growth of two hormone-dependent mammary tumors by dibutyryl cyclic AMP

Growth of hormone-dependent rat mammary tumors was arrested in vivo by N(6),O(2)'-dibutyryl cyclic adenosine 3',5'-monophosphate. Estrogen concentration did not change, but acid ribonuclease activity and synthesis increased during treatment with the dibutyryl cyclic nucleotide, as was shown during tumor regression due to hormonal deprivation. Growth arrest, thus, appears to derive from enhanced tissue catabolism.