Oncologic feasibility of D1+ gastrectomy for patients with cT1N1, cT2N0-1, or cT3N0 gastric cancer

IntroductionD2 gastrectomy has shown a survival benefit in patients with highly advanced gastric cancer; however, it remains unclear whether D2 gastrectomy is required for patients with early-stage advanced gastric cancer or early gastric cancer with limited lymph node metastasis. This analysis aimed to clarify the oncologic feasibility of D1+ gastrectomy in patients with cT1N1, cT2N0-1, or cT3N0 gastric cancer.MethodsThis retrospective cohort analysis included 466 patients with cT1N1, cT2N0-1, or cT3N0 gastric cancer who received curative gastrectomy with either D2 or D1+ dissection. Surgical outcomes were compared between the D2 group (n = 406) and the D1+ group (n = 60).ResultsThe number of patients with higher age and higher comorbidity index was greater in the D1+ group than in the D2 group. Postoperative complications were significantly lower in the D1+ group than in the D2 group (10.0% vs. 26.8%, p = 0.004). No statistically significant difference in 5-year overall survival (p = 0.146) and disease-specific survival (p = 0.807) between the groups was noted. The incidence of local recurrences (p = 0.500) and that of lymph node recurrences (p = 1.000) were also similar between the groups. Multivariable analysis for overall survival identified age, clinical node-positive status, high Charlson score (≥3), advanced pathological stage (≥III), and postoperative complication (grade ≥ II) as independent prognostic factors. The propensity score-matched analysis showed very similar survival outcomes between the groups.ConclusionD1+ gastrectomy may be oncologically feasible for patients with cT1N1, cT2N0-1, or cT3N0 stage gastric cancer.     

Acetyl coenzyme A-dependent metabolic activation of N-hydroxy-3, 2'-dimethyl-4-aminobiphenyl and several carcinogenic N-hydroxy arylamines in relation to tissue and species differences, other acyl donors, and arylhydroxamic acid-dependent acyltransferases

The metabolic activation of several carcinogenic N-hydroxy (N-OH)-arylaminesby cytosolic S-acetyl coenzyme A (AcCoA)-dependent enzymes wasexamined in tissues and species susceptible to arylamine carcinogenesis.Comparisons of the AcCoA-dependent activity were also made withknown cytosolic arylhydroxamic acid-dependent acyltransferasesand with the ability of different acyl donors to mediate thebinding of N-OH-arylamines to DNA. With rat hepatic cytosol,AcCoA-dependent DNA binding was demonstrated for several [³H]N-OH-arylamines,in the order: N-OH-3, 2'-dimethyl-4-aminobiphenyl (N-OH-DMABF),N-OH-2-aminofluorene (N-OH-AF) > N-OH-4-aminobiphenyl >N-OH-N'-acetylbenzidine > N-OH-2-naphthylamine; N-OH-N-methyl-4-amino-azobenzenewas not a substrate. No activity was detected in dog hepaticor bladder cytosol with any of the N-OH-arylamines tested. Usingeither N-OH-DMABP or N-OH-AF and rat hepatic cytosol, activationto DNA-bound products was also detected with acetoacetyl- andpropionyl-CoA but not with folinic acid or six other acyl CoA's.However, p-nitro-phenyl acetate which is known to generate acetyl-enzymeintermediates effectively replaced AcCoA. Subcellular fractionationof rat liver showed that the AcCoA-dependent DNA-binding ofN-OH-DMABP with cytosol was 5 times greater than that obtainedwith the microsomal or mitochondrial/nuclear fractions. Furthermore,the cytosolic activity was insensitive to inhibition by theesterase/deacetylase inhibitor, paraoxon; while the activityof the other subcellular fractions was completely inhibited(>95%). AcCoA-dependent activation of N-OH-DMABP was alsodetected with rat tissue cytosols from intestine, mammary glandand kidney, which like the liver, are targets for arylamine-inducedtumorigenesis. Using N-OH-DMABP, AcCoA-dependent DNA-bindingactivity was also detected in the hepatic cytosols from severalspecies in the order: rabbit > hamster > rat, human >guinea pig > mouse. In contrast, the arylhydroxamic acid,N-OH-N-acetyl-DMABP, was not activated to a DNA-binding metaboliteby the hepatic cytosolic N, O-acyltransferase of any of thesespecies, thus suggesting that the AcCoA-mediated binding ofN-OH-DMABP results from the direct formation of N-acetoxy-DMABP.With N-OH-AF as the substrate, the AcCoA-dependent activationwas in the order: rabbit > guinea pig, hamster > mouse> human, rat. In contrast to the AcCoA-dependent activationof N-OH-AF, only very low N-OH-N-acetyl-4-aminobiphenyl-dependenttransacetylase and N-OH-N-acetyl-2-aminofluorene N, O-acyitransferaseactivity was detected in the hepatic cytosols for the human,guinea pig, and mouse. Selected inhibitors did not discriminatebetween the three acyltransferase activities in rat hepaticcytosol; and up to 40% inhibition was observed with 100 µM4-aminoazobenzene or pentachlorophenol. These studies indicatethat the AcCoA-dependent formation of reactive N-acetoxy arylaminesby cytosolic acetyltransferase(s) could serve as a major metabolicactivation pathway in several species, particularly those whichcannot utilize arylhydrox-amic acids as acyl donors for intramolecularN, O-acyltransfer or for intermolecular transacetylation ofN-OH-arylamines.     

重组人干扰素α2a和GFE-1多肽融合基因的克隆、表达及活性测定

目的:构建IFN-α2a-GFE-1融合蛋白基因表达载体,获得高质量生物产品。方法:应用聚合酶链式反应技术(PCR)对干扰素(IFN)α2a3'端酶切位点进行改造,人工合成编码能特异性高效结合肺组织的GFE-1寡核苷酸片段,二者连接后克隆入pGEM3Zf质粒,进行序列分析,将融合蛋白基因克隆入pBV220表达载体,在大肠杆菌中表达,对IFN-α2a-GFE-1表达产物纯化、鉴定及体外活性检测。结果:利用PCR的方法成功地改造了IFN-α2a3'端酶切位点,成功的将GFE-1多肽与IFN-α2a3'端连接,构建了IFN-α2a-GFE-1融合蛋白的基因克隆载体pGEM3Zf-GFE-1,DNA测序完全正确。构建了IFN-α2a-GFE-1融合蛋白基因原核表达载体pBV220-IFN-α2a-GFE-1,经温度诱导在大肠杆菌中有效表达。纯化了IFN-α2a-GFE-1融合蛋白,SDS-PAGE凝胶电泳检测纯度大95%,比活性达5.8×109U/mg。结论:IFN-α2a-GFE-1融合蛋白基因的成功克隆、表达、纯化和活性测定,为研制一种具有导向性治疗肺癌、肺纤维化等疾病的有效药品奠定基础。     

Metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by hamster, mouse and rat intestine: relevance of species differences

We recently demonstrated the metabolism of 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone(NNK) in rat intestinal segments, as well as the inducibilityof intestinal NNK metabolism by starvation or acetone treatmentTo improve our understanding of intestinal NNK turnover we haveadditionally investigated NNK metabolism in isolated perfusedjejunal segments from NMRI mice and Syrian golden hamsters.[¹⁴C]NNK (1 µmol/1) was metabolized extensively by jejunalsegments from female NMRI mice (88.5%) and female Syrian hamsters(86.4%), whereas in male NMRI mouse segments a slightly lowermetabolism (68.8%) was observed. a-Hydroxylation was the predominantmetabolic pathway in mice (58% of total metabolism), whereasin female Syrian hamsters N-oxidation accounted for>50% ofthe metabolites [4-(methynitrosamino)-1-(3-pyridyl-N-oxide)-1-butanol27 %, 4-(methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone22% of total radioactivity]. Formation of 4-(methylnitros-amino)-l-(3-pyridyl)-l-butanol(NNAL) was low in both species. Total NNK metabolism in maleNMRI mice was increased by starvation to 84.4% and by acetonetreatment to 90.0% of the absorbed radioactivity. This increasewas due to an increase in N-oxidation, whereas the amounts of-hydroxides and NNAL remained unchanged. In female Syrian hamstersacetone treatment had only minimal effects upon the metabolitecomposition. Acetone-treated NMRI mice and Syrian hamsters wereadditionally gavaged with the chemopreventive agent phenethyl-isothiocyanate(PEITC). In mice this treatment slightly decreased keto acidformation (0.6-fold, P < 0.05), whereas in hamsters PEITChad no effect In summary, intestinal metabolism of NNK in rats,mice and hamsters differs in both the extent of total metabolism(hamsters mice > rats) and the metabolite composition, indicatingmajor species differences.     

YpT1-2N0 rectal cancer after neoadjuvant chemoradiation has lower survival compared with pT1-2N0 rectal cancer

Pathologic T1-2N0 rectal cancer shows an excellent prognosis without preoperative or postoperative chemoradiation. However, oncologic outcome of ypT1-2N0 remains unclear and undetermined. Thus, the aim of this study was to compare the survival of ypT1-2 and pT1-2 rectal cancer patients after radical resection and identify risk factors of ypT1-2 rectal cancer in Surveillance, Epidemiology, and End Results Program (SEER)-registered rectal cancer patients. The results showed that ypT1-2N0 rectal cancer after neoadjuvant chemoradiation has lower survival compared with pT1-2N0 rectal cancer and mucinous/signet-ring cancer and less than 12 lymph nodes retrieval were two risk factors in ypT1-2 patients. These results suggest that ypT1-2 patients with one or two risk factors may benefit from postoperative adjuvant chemotherapy.     

Metabolism of aromatic amines: relationships of N-acetylation, O-acetylation, N,O-acetyltransfer and deacetylation in human liver and urinary bladder

N-Acetoxyarylamines are reactive metabolites that are implicatedin the initiation of the carcinogenic process by some N-substitutedaryl compounds. The objective of this study was to explore therelationship between the production of these reactive speciesand N-acetylation (NAT), a reaction previously demonstratedto be polymorphic in the human. Human liver and urinary bladdermucosa samples were frozen within 4–8 h post mortem. Thesetissues were assayed for the (i) O-acetylation (OAT) of N-hydroxy-3,2'-di-methyl-4-aminobiphenyl (N-OH-DMABP) by acetyl CoA, (ii)intramolecular N,O-acetyltransfer (AHAT) of N-hydroxy-2-acetylaminofluorene(N-OH-AAF), (iii) NAT of 2-aminofluorene (2-AF) and p-aminobenzoicacid (PABA) by acetyl CoA and (iv) deacetylation of N-OH-AAF.Cytosolic AHAT and OAT showed partial inhibition by paraoxon.The ratio of paraoxon insensitive AHAT to OAT to NAT of PABAto NAT of 2-AF appears to be 1:2:11:22 using freshly made cytosolsfrom frozen livers. Freezing of the cytosol resulted in extensiveloss of activities. All four of these cytosolic enzyme activitiesexhibited a similar polymorphic response. Microsomal deacetylationshowed a monomorphic response. Similar to the liver, urinarybladder epithelial cells also catalyzed the same reactions.However, the OAT and AHAT activities were detected mainly inmicrosomes. These data suggest that phenotypically rapid acetylatorshave a greater biochemical potential for the metabolic activationof aromatic amines by pathways that involve O-acetylation.     

UDP-GalNAc:Fuc{alpha}1-2Gal{alpha}1-3GalNAc transferase activity in hamster pancreatic cancers and in normal hamster alimentary tissues

Ductal adenocarcinomas induced by N-nitrosobis(2-oxopropyl)aminetreatment in Syrian hamsters produce blood group-A antigen,which is not present in normal hamster pancreas. To understandthe underlying mechanism of A antigen neoexpression in pancreaticcancer cells, we examined the activity of UDP-GalNAc: Fuc1–2Gal1–3GalNActransferase (A-transferase), the enzyme responsible for bloodgroup-A antigen production. The specific activity of A-transferasein the pancreatic cancers was 8 nmol/mg protein/h in membranepreparations, 0.3 nmol/mg protein/h in whole cell extracts,and undetectable in normal hamster pancreas. Significant A-transferaseactivity was found in normal tissues expressing blood group-Aantigen. Although both normal (gastric antrum, colon) and pancreaticcancer cells showed similar enzymatic characteristics (optimalpH, substrate affinity, optimal [Mn²⁺]), there was a differencein the requirement for divalent cations. The A-transferase incancer cells showed a more stringent requirement for Mn²⁺. Theseresults suggest that A-transferase is activated during nitrosamine-inducedpancreatic carcinogenesis, which results in the neoexpressionof blood group-A antigen. The difference in divalent cationrequirements between A-transferase activities of cancer andnormal cells may indicate that there are multiple A-transferasespresent in hamster tissues.     

Augmentation of UDP-GalNAc: Fucalpha1-2Gal alpha1-3 N-acetylgalactosaminyl transferase activity in nitrosamine-induced hamster pancreatic cancers

Pancreatic cancers induced by N-nitrosobis(2-oxopropyl)amine (BOP) in hamsters produce blood group-A antigen (BG-A Ag), which is not present in the normal pancreas. To understand the neo-expression mechanism of BG-A Ag, we examined uridine diphosphate (UDP)-N-acetylgalactosamine (GalNAc): fucose (Fuc) alpha1-2 galactose (Gal) alpha1-3 GalNAc transferase (alpha1-3 GalNAc Tf) activity, the enzyme responsible for BG-A production. The specific activity of alpha1-3 GalNAc Tf in pancreatic cancers was approximately 8,000 nmole/g protein/h, whereas it was absent from the normal pancreas. Although the antrum and colon express A-Tf and BG-A Ag, the divalent cation requirements of alpha1-3 GalNAc Tf in these tissues were different from those of cancers. These results suggest that alpha1-3 GalNAc Tf is activated during BOP-induced pancreatic carcinogenesis, and that there are multiple alpha1-3 GalNAc Tf isozymes present in hamster tissues.     

Tissue distribution of N-acetyltransferase 1 and 2 catalyzing the N-acetylation of 4-aminobiphenyl and O-acetylation of N-hydroxy-4-aminobiphenyl in the congenic rapid and slow acetylator Syrian hamster

N-acetyltransferase 1 (NAT1) and 2 (NAT2) enzymes catalyzing both deactivation (N-acetylation) and activation (O-acetylation) of arylamine carcinogens such as 4-aminobiphenyl (ABP) were investigated in a Syrian hamster model congenic at the NAT2 locus. NAT2 catalytic activities (measured with p-aminobenzoic acid) were significantly (P < 0.001) higher in rapid than slow acetylators in all tissues (except heart and prostate where activity was undetectable in slow acetylators). NAT1 catalytic activities (measured with sulfamethazine) were low but detectable in most tissues tested and did not differ significantly between rapid and slow acetylators. ABP N-acetyltransferase activity was detected in all tissues of rapid acetylators but was below the limit of detection in all tissues of slow acetylators except liver where it was about 15-fold lower than rapid acetylators. ABP N-acetyltransferase activities correlated with NAT2 activities (r2 = 0.871; P < 0.0001) but not with NAT1 activities (r2 = 0.132; P > 0.05). Levels of N-hydroxy-ABP O-acetyltransferase activities were significantly (P < 0.05) higher in rapid than slow acetylator cytosols for many but not all tissues. The N-hydroxy-ABP O-acetyltransferase activities correlated with ABP N-acetyltransferase activities (r2 = 0.695; P < 0.0001) and NAT2 activities (r2 = 0.521, P < 0.0001) but not with NAT1 activities (r2 = 0.115; P > 0.05). The results suggest widespread tissue distribution of both NAT1 and NAT2, which catalyzes both N- and O-acetylation. These conclusions are important for interpretation of molecular epidemiological investigations into the role of N-acetyltransferase polymorphisms in various diseases including cancer.     

Comparative kinetic studies on aflatoxin B1- DNA binding and aflatoxin B1-glutathione conjugation with rat and hamster livers in vitro

Inhibition of microsome mediated aflatoxin B₁ (AFB₁) bindingto exogenous or endogenous DNA by cytosolic glutathione (GSH)S-transferases is well established from our earlier studies.Correlation between inhibition of AFB₁-DNA binding and AFB₁-GSHconjugation in vitro using rat and hamster liver subcellularfractions is elucidated in this report. Even though hamsterliver microsomes catalyzed AFB₁ binding to exogenous DNA threetimes as much as the rat, hamster cytosol inhibited AFB₁-DNAbinding catalyzed by either microsomes severalfold more thanthe rat cytosol. AFB₁ - DNA binding is found to be inverselyrelated to AFB₁-GSH conjugation at all AFB₁ concentrations (2–100µM)studied. Presence of either styrene oxide or 3,3,3-trichloropropeneoxide at 1 mM level diminished AFB₁-GSH formation in vitro confirmingsome competition by these epoxides with AFB₁-epoxide for cytosolicGSH S-transferases. In a reconstituted system with endogenousDNA, the ratio of AFB₁-GSH to AFB₁-DNA binding was found tobe 10–15 times higher with the hamster in comparison withthe rat indicating enhanced inactivation of the ultimate carcinogenicmetabolite in the hamster. These results are discussed in relationto AFB₁-DNA binding and AFB₁ hepatocardnogenicity in resistantand sensitive species.     

Binding of N-acetylbenzidine and N,N''-diacetylbenzidine to hepatic DNA of rat and hamster in vivo and in vitro

Benzidine, a potent hepatocarcinogen in rodents, is readilymetabolised to acetylated derivatives. In this study, the covalentbinding of [³H-acetyl]N-acetylbenzidine and [³H-acetyl]N,N'-diacetylbenzidineto liver DNA in rats and hamsters was investigated. Bindingto liver DNA of rats at 1 or 7 days after i.p. injection ofN-acetylbenzidine was 2-fold higher than that observed in theliver DNA of hamsters which had been similarly treated. Analysisof enzymically hydrolysed DNA from both species indicated thepresence of a single adduct which co-eluted with N-(deoxyguanosin-8-yl)-N'-acetylbenzidine. In vitro treatment of rat or hamster liverslices with N-acetylbenzidine also resulted in covalent bindingto hepatic DNA and the identical DNA adduct was detected atlevels comparable to that observed in vivo. When N,N'-diacetylbenzidinewas injected i.p. into rats, a comparatively low level of bindingto liver DNA was observed. Following enzymic hydrolysis, themajor DNA adduct detected by h.p.l.c. analysis was again N-(deoxyguanosin-8-yl)-N'-acetylbenzidineaccompanied by a small amount of N-(deoxyguanosin-8-yl)-N,N'-diacetylbenzidine.In vitro incubation of N,N'-diacetylbenzidine with rat liverslices resulted in DNA binding levels similar to that observedwith N-acetylbenzidine. In contrast to what was found in vivo,N-(deoxyguanosin-8-yl)-N,N'-diacetylbenzidine was the majoradduct detected in DNA from rat liver slices. These data suggestthat both N-hydroxy-N'-acetylbenzidine and N-hydroxy-N,N'-diacetylbenzidineare proximate carcinogenic species of benzidine, with N-hydroxy-N'-acetylbenzidinethe more important. The low level of N-(deoxyguanosin-8-yl)N,N'-diacetylbenzidineobserved in vivo may be due to its rapid repair. Alternatively,N-sulphonyloxy-N,N'-diacetylbenzidine, which would produce thisadduct on reaction with DNA, may be efficiently detoxified invivo.     

Genotoxicity of 1- and 2-nitropropane in the rat

2-Nitropropane (2-NP) is a rat liver carcinogen, whilst the 1-isomer is non-carcinogenic in rodents. Although DNA repair tests in the rat liver discriminated clearly between the carcinogenic and the non-carcinogenic isomer, uniformly negative results have been published for the mouse bone marrow micronucleus test (BMMN test) with both isomers. Therefore, the latter assay did not discriminate between the carcinogenic and the non-carcinogenic isomer. To investigate whether this is due to endpoint specificity or organospecificity of 2-NP, studies were carried out in the rat in which micronucleus induction (bone marrow and liver) and unscheduled DNA synthesis (UDS) induction (liver) were measured after oral treatment with either nitropropane isomer. 2-NP induced UDS in the liver whilst the 1-isomer was negative, thus confirming the published studies. In the BMMN test, occasional small increases in the incidence of micronuclei were found for both compounds, but results were interpreted as negative after considering the control background data and the lack of reproducibility. By contrast, the liver micronucleus test revealed a clastogenic effect of 2-NP in the liver. This indicates that 2-NP induces chromosome aberrations as well as DNA repair in vivo, but it seems to act organospecifically. For 1-NP a slightly increased incidence of micronuclei was found in the liver, which was accompanied by a markedly increased mitotic index. It therefore remains questionable as to whether this increased micronucleus frequency for 1-NP is an indicator of a clastogenic effect, or whether it is caused by an increased cell proliferation induced by 1-NP. Consequently, it is too early to conclude whether the liver micronucleus assay is able to discriminate between the carcinogenic and non-carcinogenic isomer. However, the results provide further evidence that bone marrow assays are insufficient for the detection of all genotoxic carcinogens in vivo. This indicates the need for analysing a second tissue, particularly when negative bone marrow results have been obtained with in vitro genotoxins.     

DNA single-strand breaks and toxicity induced by 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone or N-nitrosodimethylamine in hamster and rat liver

Syrian golden hamsters and F344 rats display contrasting susceptibilitiesto hepatocarcinogenesis induced by the tobacco-specific nitrosamine4-(methylnitrosamino)-1-(3-pyri-dyl)-1-butanone (NNK) and N-nitrosodimethylamine(NDMA). In this study, the time courses of DNA single-strandbreaks (SSB) and toxicity induced by NNK and NDMA in hamsterand rat liver were compared. DNA SSB reached a maximum 12 hafter carcinogen treatment, partially correlating with previousreports on time courses of DNA methyiation. The persistenceof DNA SSB up to 2–3 weeks after NNK or NDMA treatmentreflects a deficient repair of some DNA lesions. No significantspecies differences in the kinetics of DNA SSB induction andrepair were observed following NNK or NDMA (0.39 mmol/kg) treatment.However, NNK induced slightly more DNA SSB than NDMA in bothspecies. This could reflect the formation of intermediates withmore DNA-damaging capacity or inhibiting DNA processes. A significanthepatoxic effect of NNK, evaluated by plasma markers of liverinjury, was observed in rats and hamsters 12–24 h post-treatment.In contrast, NDMA induced earlier (<12 h) enzyme elevations.Maximum hepatotoxic effects were observed 24 h (NNK-treatedhamsters and rats, NDMA-treated rats) or 2 weeks (NDMA-treatedhamsters) after carcinogen administration. Three weeks aftertreatment, hepatotoxicity of NNK and NDMA was still detectedin hamsters, but not in rats. These results suggest that thetoxic effects of NNK and NDMA initiate a regenerative processthat occurs faster in rat than in hamster liver. Since hepatocarcinogenesisoccurs in NNK- but not in NDMA-treated rats, promutagenic lesionsgenerated from NNK might be fixed preferentially during cellproliferation.     

Immunocytochemical identification of DNA adducts, O6-methylguanine and 7-methylguanine, in respiratory and other tissues of rat, mouse and Syrian hamster exposed to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone

The present paper reports about an immunocytochemical inventoryof the cell types involved in the metabolic activation of thetobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK) to a DNA methylating metabolite. The formation and distributionof the methylated DNA bases O⁶-methylguanine (O⁶-meGua) and7-methylguanine (7-MeGua) were studied in respiratory tissues,oesophagus, liver, kidneys, pancreas, small intestine, colonand prostate of rat, mouse and hamster 6 h after treatment witha single dose of 30 mg NNK/kg. The tissue-and cell-specificdistribution of O⁶-meGua- and 7-meGua-specific nuclear stainingshowed the same patterns and were remarkably similar in rat,mouse and hamster in spite of the diverging spectra of NNK-inducedtumours in these species. In nasal tissue, a target for NNK-inducedtumourigenesis in rat and hamster, but not in mouse, adduct-specificnuclear staining was observed in all three species in sustentacularcells, Bowman glands, respiratory epithelial cells and serousglands. Both methylated DNA bases were also observed in basalcells of the olfactory epithelium of rat and (occasionally)hamster, but not in those of the mouse. In the trachea, a targetfor NNK-induced tumourigenesis in hamster only, substantialadduct-specific nuclear staining was found in basal epithelialand glandular cells of the hamster; in the same cells of ratand mouse only a weak nuclear staining was found. In the lung,a common target for NNK-induced tumourigenesis, the formationof O⁶-meGua and 7-meGua was restricted predominantly to bronchialand proximal bronchiolar epithelium. Nuclear staining in therat was occasionally found in alveolar cells and was also observedin hepatocytes. In the three species investigated, O⁶-meGua-and 7-MeGua-specific nuclear staining was found in target andnon-target tissues. Apparently, and in analogy with resultsobtained in other studies, the species-specific organotropyfor tumour formation of NNK is not exclusively determined byDNA methylation. Expanding methylation data with literaturedata on factors considered to be involved in tumour formation,namely proliferation, toxicity and DNA repair among others,still did not lead to a satisfactory explanation for the species-specificorganotropy observed. Additional factors (yet to be identified),need to be taken into account in order to explain (and predict)tumourigenic effects induced by monofunctional methylating agents.     

Comparative carcinogenicities of 1-, 2-, and 4-nitropyrene and structurally related compounds in the female CD rat

The comparative carcinogenicities of N-hydroxy-N-acetyl-1-aminopyrene, N-acetyl-1-aminopyrene, and 1-, 2-, and 4-nitropyrene were determined following i.p. injection into weaning female CD rats (67 mumol/kg body weight in dimethyl sulfoxide; 3 times/week for 4 weeks). At sacrifice 61 weeks after the first injection the incidences of malignant mammary tumors were increased significantly to 45 and 24% in the 4-nitropyrene- and N-hydroxy-N-acetyl-2-aminofluorene-treated groups, respectively. Cellular altered foci in the liver were increased significantly in the N-acetyl-1-aminopyrene-, N-hydroxy-N-acetyl-1-aminopyrene-, and N-hydroxy-N-acetyl-2-aminofluorene- treated groups; the latter two compounds also led to significantly increased formation of hyperplastic nodules in this organ. Significant increases in leukemia induction were observed in animals treated with 2-nitropyrene or N-hydroxy-N-acetyl-2-aminofluorene. In an experiment designed to compare the influence of the route of administration on the carcinogenic potential of this agent, 1-nitropyrene was injected i.p. or s.c. into weanling female CD rats (100 mumol/kg body weight; once a week for 4 weeks). The animals were sacrificed at 87 to 90 weeks after the first treatment. The incidences of mammary gland tumors in animals receiving injections of 1-nitropyrene by either route (59%) were significantly higher than in solvent-injected controls (37%). The incidences of adenocarcinoma in the i.p. 1-nitropyrene group (28%) and fibroadenoma in the s.c. 1-nitropyrene group (52%) were significantly higher than in the control animals (7 and 27%, respectively). These data suggest that the demonstration of the weak carcinogenicity of 1-nitropyrene is probably more a function of the length of the observation period than of the routes of administration used here. A further exploration of the effect of the route of administration involved treatment of weanling female CD rats by direct injection of 1-, 2-, or 4-nitropyrene into the mammary fat pads. A total of 2.04 mumol of the nitrocompound in dimethyl sulfoxide was injected into the mammary glands under each of the 6 left nipples. The right mammary glands were treated with the solvent only. Injections of the thoracic nipple areas were carried out on day 1; inguinal areas were treated on day 2. The animals were sacrificed after 77 weeks. The number of mammary tumor-bearing animals (23 of 28), the number with fibroadenoma (15 of 28), and the number with adenocarcinoma (19 of 28) were significantly increased in the 4-nitropyrene-treated group as compared with animals treated with only dimethyl sulfoxide.(ABSTRACT TRUNCATED AT 400 WORDS)     

Increased expression and activation of matrix metalloproteinase-2 (MMP-2) in O-1N: hamster oral squamous cell carcinoma with high potential lymph node metastasis

Oral squamous cell carcinoma (OSCC) is one of the most common head and neck cancers with poor clinical outcome. MMP-2 was implied to contribute to the invasiveness and metastatization of various malignancies because of the degradation of type IV collagen. In this experiment, ELISA, Western blot and Q-RT-PCR was performed to investigate the expression and activation of MMP-2 in serum and tumor from hamster oral cancer model with high lymph node metastasis based on the various stages of OSCC development. Active MMP-2 in the serum was found elevated during oral cancer progression. In the metastatic stage, total MMP-2 level was 46% higher than it in the expansive stage, while active MMP-2 level increased 6-fold than it in the expansive stage. MMP-2 serum activation ratio was significantly enhanced in the metastatic stage than before tumor transplantation and that in the expansive stage. MMP-2 protein and MMP-2 mRNA was found to be increased during oral cancer development in hamster models. The increase of MMP-2 expression and activation starts prior to the metastasis occurrence, indicating the important role of MMP-2 in the early phase of oral cancer progression. Active MMP-2 level in serum may be a useful indicator for monitoring oral cancer progression.     

Quantitative structure-activity relationships: analysis of interactions of 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2-substituted analogues with rat, mouse, guinea pig, and hamster cytosolic receptor

The competitive receptor binding affinities of thirteen 2-substituted 3,7,8-trichlorodibenzo-p-dioxins to hepatic cytosol from rat, mouse, guinea pig, and hamster were determined with [3H]-2,3,7,8-tetrachlorodibenzo-p-dioxin as the radioligand. Multiple parameter linear regression analysis of the binding data from the four species gave the following equations: pEC50 (rat) = 7.196 + 0.600 pi - 0.255 delta Es - 1.683 HB pEC50 (mouse) = 6.365 + 1.641 pi + 1.206 sigma 0 pEC50 (hamster) = 7.416 + 1.026 pi + 0.509 delta Es + 0.748 sigma 0 pEC50 (guinea pig) = 6.892 + 1.035 pi where pi, delta Es, HB, sigma 0, and Vw are physicochemical parameters for substituent lipophilicity, steric effect, hydrogen bonding capacity, electronegativity, and van der Waals volume (relative to H), respectively. These equations demonstrate that there are important species differences in the receptor protein binding site interactions with the substituted analogues. These data, coupled with the known species differences in the molecular properties of the receptor proteins, are evidence for a heterologous nature of the receptor between mammalian species. Multiple parameter linear regression analysis of the relative aryl hydrocarbon hydroxylase (AHH) induction potencies of these analogues in rat hepatoma H-4-II E-cells in culture gave the following equation. The correlation pEC50 (AHH induction) = 3.208 + 0.950 pEC50 (rat binding) - 0.955 delta B5 between receptor binding and AHH induction was dependent on a steric parameter (delta B5, STERIMOL) and the results suggest that an additional substituent-dependent process (e.g., an activation step) may be required after initial ligand-receptor binding for the ultimate expression of the receptor-mediated response (i.e., AHH induction).