Abundant TGF{alpha} a precursor and EGF receptor expression as a possible mechanism for the preferential growth of carcinogeninduced preneoplastic and neoplastic hepatocytes in rats

Expression of transforming growth factor a (TGF     

TGF{alpha} is differentially expressed in liver foci induced by diethylnitrosamine initiation and peroxisome proliferator promotion

Transforming growth factor     

Nitroso transfer from {alpha}-nitrosamino aldehydes: implications for carcinogenesis

Six alkylnitmamino ethanols (R-N(N0)-CH₂CH₂0H; R = Me, nBu,sBu, iBu, tBu, HOCH₂CH₂), including the potent carcinogen N-nitrosodiethanolamine,have been shown to undergo efficient liver alcohol dehydrogenasecatalyzed oxidation to their corresponding -nitrosamino aldehydes.Five structurally representative nitrosamino-ethanals (RN( NO)CH₂CH0,R = 4-ClC₆H₄-, CH₃-, nBu-, tBu-, HOCH₂CH₂-) have been synthesized.Each of these compounds demonstrates the unusual property offacile transnirosation to a secondary amine. Transnitrosationto dimethylamhe, pyrrolidine, morpholine and N-methylanllinehas been shown. This reaction occurs rapidly at room temperaturein organic solvents but is somewhat slower in aqueous bufferdue to extensive equitibrium formation of gem diols by hydrationof the aldehyde group. In aqueous media the transnitrosationrate increases with increasing pH from 7to9anddoesnotocavatpH4.Transnitrosationtoprimaryamines results in deamination (benzylamine benzyl alcohol).The transnitrosation reaction is accompanied by the formationof imines of glyoxal (R - N = CH - CH = N - R) which appearas primary amines and glyoxal in aqueous sdution. Other productshave also been characterized as well. These chmical and biochemicaldata, taken together with results in other laboratories, providestrong support for our hyppothesis that certin ß-oxidizednitrosamines can be activated to proximate or ultimate carcinogensby biochemical oxidation to produce highly reactive nitrosamines.     

Covalent hydration: a possible mechanism for aza-arene carcinogenesis

It is hypothesized that differences in the carcinogenicity of certain aza-arenes and their carbocyclic analogs may originate from the ability of the former to form covalent hydrates. The hypothesis is primarily based on a comparison of the carcinogenicity of several aza-arenes with that of corresponding carbocyclic compounds and of aromatic amines which are structurally related to the hydrated aza-arenes. Additional evidence is provided by the regiochemistry of cytochrome P-450 catalyzed oxidation of quinoline.     

Involvement of transforming growth factor {alpha} (TGF{alpha}) and epidermal growth factor receptor (EGFR) in sex hormone-induced prostatic dysplasia and the growth of an androgen-independent transplantable carcinoma of the prostate

We previously reported the induction of dysplasia, a putativeprecursor of carcinoma, in the dorsolateral prostates (DLPs)of Noble rats by the combined administration of testosterone(T) and estradiol-17ß (E₂) for 16 weeks. Additionally,we demonstrated growth of the AIT, a DLP-derived, androgen-independent,transplantable solid tumor, in castrated syngeneic hosts. Inthis investigation, using Northern blot hybridization, radioimmunoassaysand radioligand assays, we showed that transforming growth factor-     

Modification of carcinogenesis by {alpha}-tocopherol, t-butylhydro-quinone, propyl gallate and butylated hydroxytoluene in a rat multi-organ carcinogenesis model

Effects of the dietary antioxidants     

Expression of cytokines, TNF-{alpha} and IL-1{alpha}, in MAM acetate and 1-hydroxyanthraquinone-induced colon carcinogenesis of rats

The expression of cytokines, TNF-     

Modulation of mouse skin tumor promotion by dietary 13-cis-retinoic acid and {alpha}-difluoromethylornithine

The effects of dietary supplementation of 13-cis-retinoic acid(13-cis-RA) and -difluoromethylornithine (DFMO) in the drinkingwater on 12-O-tetradecanoylphorbol-13-acetate (TPA)-promotedskin tumor formation was determined. Administration of 13-cis-RAin the diet and DFMO in the drinking water was started 1 weekand 2 days before the first TPA application to the dimethylbenz[a]anthracene-initiatedskin of either female CD-I or SENCAR mice, respectively. Dietary13-cis-RA failed to inhibit both the tumor yield and the incidence;papillomas per mouse at 0, 5, 50, 100 and 200 mg/kg diet 13-cis-RAdoses were 25, 30, 22, 28 and 25 respectively at 18 weeks ofpromotion treatment and at all doses 100% of the mice bore papillomas.However, dietary 13-cis-RA dramatically reduced the size ofskin tumor promoted with TPA. 13-cis-RA at doses of 5, 50, 100and 200 mg/kg diet inhibited skin papillomas (> 4 mm diameter)per mouse by 28, 55, 76 and 93%, respectively. Retinoid treatmentdid not affect body weight gains and the survival was more than80% in all groups. In accord with our previous findings, DFMOwhen given in drinking water, was a very effective inhibitorof mouse skin tumor promotion by TPA; DFMO at 0.25% concentrationinhibited the number of papillomas by 50%. Inhibition of skintumor promotion by combined treatments with dietary 13-cis-RA(100 mg/kg) and DFMO (0.25%) in the drinking water was possiblyadditive. The retinoid and DFMO preclude TPA-increased ornithinedecarboxylase (ODC) activity and the accumulation of putrescineby differential effects on ODC, an enzyme associated with skintumor promotion by TPA.     

CANCER BIOLOGY: Effects of dietary {beta}-carotene and selenium on initiation and promotion of pancreatic carcinogenesis in azaserine-treated rats

In the present study the effects of 0.1 or 1.0 g ß-carotene/kg diet (LßC or HßC) and 1.0 mg or 2.5 mgselenium/kg diet (LSel or HSel), as well as combinations ofthe respective low and high concentrations of ß-caroteneand selenium (LMix or HMix) on the initiation/early promotionphase or on the late promotion phase of pancreatic carcinogenesisin azaserine-treated rats, were investigated using cell proliferationand volumetric data of atypical acinar cell foci (AACF) as parameters.The present results indicate chemo-preventive effects of dietaryselenium, dietary ß-carotene and of their combinationon the development of acinar pancreatic lesions induced in ratsby azaserine. The inhibitory effect was most pronounced whenß-carotene and/or selenium were added to the dietsduring the late promotion phase of the carcinogenic process,although inhibition was also observed with these compounds whenthey were added to the diets during the first 5 weeks of thestudy only (initiation/early promotion phase). Neither in theinitiation/ early promotion phase nor in the late promotionphase was a dose-related trend observed. The multiplicitiesof AACF with a diameter over 1.0 mm and of carcinomas in situ(CIS), as well as the incidence of CIS were not significantlydifferent among the groups. However, in the late promotion experimenta dose-related decline in multiplicity could be observed inthe selenium supplemented groups and in the groups receivingcombinations of ß-carotene and selenium. Cell proliferationin azaserine-induced AACF, as estimated by the bromodeoxyuridine(BrdU) labeling index, was significantly higher in HßC,HSel, LMix and HMix groups (initiation/early promotion phase)as well as in HßC, LSel, HSel, LMix and HMix groupsGate promotion phase) than in high fat controls. From the presentresults it can be concluded that: (i) ß-carotene andselenium have inhibitory effects on pancreatic carcinogenesisinduced in rats by azaserine; (ii) the most clear effects wereobserved when selenium was given as such, or in combinationwith ß-carotene during the late promotion phase; and(iii) ß-carotene and selenium stimulate cell proliferationin AACF.     

Involvement of transforming growth factor-{alpha} and its receptor in a model of DES-induced renal carcinogenesis in the Syrian hamster

This study explores the role played by TGF in estrogen-inducedrenal tumors. Tumors were induced in male Syrian hamster bychronic administration of diethylstilbestrol (DES). Six experimentalgroups (n = 5–9) were chronically exposed to DES and sacrificedafter 1, 2, 4, 6, 9 and 11 months, respectively. In the courseof treatment, the nephrons were the site of an important increaseof cell turnover, which was characterized by a process of hyperplasia/dysplasiain proximal tubules preceding the neoplastic transformation.In treated animals and in controls, the analysis of renal tissueby Western blot revealed the presence of a 6 kDa polypeptidecrossreacting with anti-TGF antibody. In controls, TGF immunoreactivitywas localized in proximal and in distal tubules. Before tumordevelopment (1–4 months), TGF RIA showed an increase ofTGF concentration in renal tissue, in parallel with the increasedcell proliferation observed in proximal tubules. In addition,Western blot analysis also demonstrated in kidney tissue thepresence of a 165 kDa protein displaying the immunoreactivityof EGF/TGF receptor. The receptor immunoreactivity was localizedin proximal tubular cells suggesting an involvement of TGF intubular epithelial growth through autocrine or paracrine pathways.In large neoplasms, immunocytochemistry revealed only clustersof transformed cells intensely stained by the anti-TGF antibody.These cells displayed the appearance of stellate or polyhedriccells infiltrating adjacent neoplastic tissues. Antisera raisedagainst intra-or extracytoplasmic domains of the EGF/TGF receptorwere assayed to localize this receptor in the tumors. In contrastwith tubular structures, immunoreactivity to EGF/TGF receptorwas never detected in tumoral tissue. The apparent absence ofEGF/TGF receptor immunoreactivity in malignant cells seems toexclude an involvement of this growth factor in the tumorigenicprocess, although it could be involved in tumor neovascularization.     

Inhibitory effects of glutathione level-raising agents and D-{alpha}-tocopherol on ornithine decarboxylase induction and mouse skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate

The constituent amino acids of reduced glutathione (GSH), GSHitself, and D--tocopherol inhibited 12-O-tetradecanoylphorbol-13-acetate(TPA)-induced ornithine decarboxylase (ODC, L-omithine carboxy-lyase,EC 4.1.1.17 [EC] ) activity in mouse epidermis in vivo and in vitro.The inhibitory effects of cysteine (Cys), GSH and D--tocopherolon ODC induction were proportional to their abilities to decreasethe incidence of skin tumors in the initiation-promotion protocol.Moreover, the ability of the constituent amino acids of GSHand GSH to inhibit TPA-induced ODC activity correlated wellwith their ability to increase the ratio of GSW/oxidized glutathione(GSSG) in isolated epidermal cells. In vitro, various treatmentswith 1 mM GSH, 1 mM glutamic acid (Glu), 1 mM glycine (Gly),0.4 mM Cys and/or 0.2 mM cystine (CysCys) inhibited dramaticallythe sharp decline in the intracellular ratio of GSH/GSSG causedby 0.1 µM TPA. Since the inhibitory effects of Cys onboth the decrease in the ratio of GSH/GSSG and the inductionof ODC activity by TPA were greatly reduced by the inhibitorsof -glutamyl transpeptidase and -glutamylcysteine synthetase,it is suggested that some of the inhibitory effects of Glu,Cys and Gly on tumor promotion could result from their interferencewith the metabolism of the tripeptide GSH, a natural antioxidantwhich inhibits chemical carcinogenesis. The free radical scavengerD--tocopherol, which did not alter directly the intracellularratio of GSH/GSSG, also prevented completely the decrease inthe ratio of GSH/GSSG caused by TPA. These results, therefore,suggest that GSH level-raising agents and other antioxidantsmight inhibit by diverse means the effects of TPA on GSH metabolismand skin tumor promotion.     

Autocrine interaction between TGF alpha and the EGF-receptor: quantitative requirements for induction of the malignant phenotype

Alterations affecting the epidermal growth factor (EGF)/transforming growth factor alpha (TGF alpha)-responsive mitogenic pathway are frequently detected in malignancies. In particular, the EGF-receptor (EGFR) molecule has been found overexpressed in a number of human tumors, and TGF alpha is produced by a large array of tumor cells. Gene transfer experiments have previously demonstrated that expression of either TGF alpha or EGFR alone is not sufficient to induce the transformed phenotype in NIH3T3 cells. In this study we sought to investigate the biological effect of expression of TGF alpha and high levels of EGFR in this model system. We demonstrate that the gene for TGF alpha acts as a potent oncogene in NIH3T3 cells overexpressing EGFR (NIH-EGFR, greater than 10(6) EGFR). We further show that TGF alpha directly stimulates proliferation of the cell in which it is produced and provide evidence that the extracellular compartment of the transformed cell is the major site of interaction between TGF alpha and EGFR. Analysis of human tumor cell lines revealed a strong correlation between expression of TGF alpha and overexpression of EGFR. Moreover, high levels of EGF-independent tyrosine phosphorylation of the EGFR were detected both in NIH-EGFR expressing TGF alpha and in high EGFR and TGF alpha coexpressing human tumor cell lines. Thus, the two events instituting the EGFR/TGF alpha autocrine loop responsible for transformation in vitro may play a role in the development of some human malignancies.     

Influence on cell-cell communication (dye-transfer) of the oncogenic {beta}-blocker DL-ZAMI 1305: possible relation to tumor promotion

The effect of the oncogenic ß-blocker DL-1-(2-nitro-3-methyl-phenoxy)-3-tert-butyl-amino-propan-2-ol(DL-ZAMI 1305) on intercellular communication between culturedcells was studied. Intercellular communication of Chinese hamsterV79 cells was measured by the dye-transfer method in which thespread of intracellularly microinjected fluorescent probe, LuciferYellow CH, through gap-junctions was used as an index of intercellularcommunication. When V79 cells are cultured with non-toxic doses(1–60 µg/ml) of DL-ZAMI 1305, a significant inhibitionof dye-transfer is observed after 4 h. The inhibition is dose-relatedand >90% inhibition is seen at the dose of 50 µg/ml.When DL-ZAMI 1305 is added at 0 and 24 h of experiment, itsinhibitory effect is maintained for at least 48 h at high doses(50–60 µg/ml), whereas for lower doses of DL-ZAMI1305, some recovery is seen after 24 h incubation. These resultsare suggestive of a possible tumor-promoting activity of DL-ZAMI1305; in vivo studies on this carcinogen are in progress.     

Hereditary persistence of {alpha}-fetoprotein: Case report and review of the literature

Persistently elevated -fetoprotein (AFP) levels of 24 to 30µg/ml (normal <10 µg/ml) were found in a 38-year-old healthyman. Subsequently, AFP was found to be elevated in another five out of 13family members within three generations. The pedigree is consistent with anautosomal dominant inheritance pattern. No discernible disease and nofunctional abnormality appears to be associated with this clinically benigndisorder which has been recorded in the literature on four occasions todate. The reported AFP levels in these other cases ranged from 18 to 198µg/ml.Physiologically, AFP is mainly produced in the liver and the yolk sac ofhuman fetuses more than four weeks old, with peak values of up to 4 mg/ml at12 to 16 weeks of gestation. After birth, AFP levels usually fall, withineight to 12 months, to a very low concentration of <10 µg/ml andpersist at low levels throughout life. However, AFP levels can rise abovenormal in both children and adults in distinct conditions and diseases whichwill be discussed.Hereditary persistence of -fetoprotein (HPAFP) should be consideredin both children and adults with unexplained and persistent elevation of AFPe.g., those screened for hepatocellular carcinoma or diagnosed for germ celltumor. It should also be recognized in AFP screening for neural tube defectsor Down's syndrome during pregnancy. Hereditary persistence of AFP can beeasily confirmed by analyzing AFP levels in family members.     

Mutagenicity and synthesis of {alpha}-substituted N-nitrosamines: derivatives with dithiocarbamic acid

Disulfiram (DSF) can considerably alter the organotropy of chemicalcarcinogens. For N-nitrosodimethylamine and for N-nitrosodiethylaminethe organotropy is shifted from the liver to the nasal cavityor the oesophagus, respectively. Whereas the influence of DSFor its metabolites on enzyme systems has been studied, littleis known about its interaction with the carcinogens at a molecularlevel. Therefore, postulated reaction products of a series of-hydroxylated N-nitroso-dialkylamines and dithiocarbamate weresynthesized and tested for mutagenicity in Salmonella typhimuriumTA 1535. The results show that the compounds conjugated at aprimary -C-atom are not mutagenic, whereas those conjugatedat a secondary -C-atom are active. The primary N-nitroso-dithiocarbamatesrepresent unique examples of inactivated dialkyl-nitrosaminederivatives. In addition, their formation in vitro was indirectlydemonstrated. The possible role these inactivated compoundsmay play during the DSF-modulation of carcinogenesis will bediscussed.