Epidemiology of cancers of infectious origin and prevention strategies.

Infectious and parasitic diseases represent the third cause of cancer worldwide. A number of infectious and parasitic agents have been suspected or recognized to be associated with human cancers, including DNA viruses, such as papillomaviruses (several HPV types), herpesviruses (EBV and KSHV), polyomaviruses (SV40, MCV, BK, and JCV), and hepadnaviruses (HBV); RNA viruses, such as flaviviruses (HCV), defective viruses (HDV), and retroviruses (HTLV-I, HTLV-II, HIV-1, HIV-2,HERV-K, and XMRV); bacteria, such as H. pylori, S. typhi, S. bovis, Bartonella, and C. pneumoniae; protozoa, such as P. falciparum; trematodes, such as S. haematobium, S. japonicum, S. mansoni, O. viverrini, O. felineus, and C. sinensis. Each one of the chronic infections with H. pylori, HPV, and HBV/HCV is responsible for approximately the 5% of all human cancers. The primary prevention of infection-related cancers is addressed both to avoidance and eradication of chronic infections and to protection of the host organism. Vaccines provide fundamental tools for the prevention of infectious diseases and related cancers. The large-scale application of the HBV vaccine has already shown to favorably affect the epidemiological burden of primary hepatocellular carcinoma, and HPV vaccines have specifically been designed in order to prevent cervical cancer and other HPV-related cancers. The secondary prevention of infection-associated cancers has already found broad applications in the control of cervical cancer. Detection of early gastric cancer by endoscopy has been applied in Asian countries. Avoidance of local relapses, invasion, and metastasis may be achieved by applying tertiary prevention, which targets specific mechanisms, such as angiogenesis.

Extracellular vesicles in biological fluids. A biomarker of exposure to cigarette smoke and treatment with chemopreventive drugs.

Extracellular vesicles (EVs) are released from cells and enter into body fluids thereby providing a toxicological mechanism of cell-cell communication. The present study aimed at assessing (a) the presence of EVs in mouse body fluids under physiological conditions, (b) the effect of exposure of mice to cigarette smoke for 8 weeks, and (c) modulation of smoke-related alterations by the nonsteroidal anti-inflammatory drug celecoxib, a selective cyclooxygenase-2 inhibitor. To this purpose, ICR (CD-1) mice were either unexposed or exposed to cigarette smoke, either treated or untreated with oral celecoxib. EVs, isolated from bronchoalveolar lavage fluid (BALF), blood serum, and urines, were analyzed by nanoparticle tracking analysis and flow cytometry. EVs baseline concentrations in BALF were remarkably high. Larger EVs were detected in urines. Smoking increased EVs concentrations but only in BALF. Celecoxib remarkably increased EVs concentrations in the blood serum of both male and female smoking mice. The concentration of EVs positive for EpCAM, a mediator of cell-cell adhesion in epithelia playing a role in tumorigenesis, was much higher in urines than in BALF, and celecoxib significantly decreased their concentration. Thus, the effects of smoke on EVs concentrations were well detectable in the extracellular environment of the respiratory tract, where they could behave as delivery carriers to target cells. Celecoxib exerted both protective mechanisms in the urinary tract and adverse systemic effects of likely hepatotoxic origin in smoke-exposed mice. Detection of EVs in body fluids may provide an early diagnostic tool and an end-point exploitable for preventive medicine strategies.

Estimates of the incidence of infection-related cancers in Italy and Italian regions in 2018.

INTRODUCTION: Chronic infections and infestations represent one of the leading causes of cancer. Eleven agents have been categorized by the International Agency for Research on Cancer (IARC) in Group 1, 3 in Group 2A and 4 in Group 2B. We previously estimated that the incidence of cancers associated with infectious agents accounted for the 8.5% of new cancer cases diagnosed in Italy in 2014. METHODS: In the present study we evaluated the incidence of cancer in Italy and in the 20 Italian regions in 2018, based on the data of Cancer Registries, and calculated the fraction attributable to infectious agents. RESULTS: Cancers of infectious origin contributed to the overall burden of cancer in Italy with more than 27,000 yearly cases, the 92% of which was attributable to Helicobacter pylori, human papillomaviruses, and hepatitis B and C viruses. With the exception of papillomavirus-related cancers, the incidence of cancers of infectious origin was higher in males (16,000 cases) than in females (11,000 cases). There were regional and geographical variations of cancers depending on the type of cancer and on the gender. Nevertheless, the overall figures were rather similar, the infection-related cancers accounting for the 7.2, 7.6, and 7.1% of all cancers in Northern, Central, and Southern Italy, respectively. CONCLUSIONS: The estimate of the incidence of cancers attributable to infectious agents in Italy in 2018 (7.3% of all cancer cases) is approximately half of the worldwide burden, which has been estimated by IARC to be the 15.4% of all cancer cases in 2012.

Metabolic reduction of chromium by alveolar macrophages and its relationships to cigarette smoke.

Pulmonary alveolar macrophages (PAM), obtained by bronchoalveolar lavage from 47 individuals, reduced hexavalent chromium [Cr(VI)] and decreased its mutagenicity. Their specific activity--mostly mediated by cytosolic, enzyme-catalyzed mechanisms--was significantly higher than in corresponding preparations of mixed-cell populations from human peripheral lung parenchyma or bronchial tree, or from rat lung or liver. At equivalent number of PAM, Cr(VI) reduction, total protein, and some oxidoreductase activities were significantly increased in smokers. No appreciable variation could be detected between lung cancer and noncancer patients. In rats, the Cr(VI)-reducing activity of PAM preparations was induced by Aroclor 1254. Thus, alveolar macrophages provide crucial defense mechanisms not only by phagocytizing metals, but also by metabolically reducing Cr(VI). The epithelial-lining fluid (ELF) also displayed some Cr(VI) reduction. Together with already investigated metabolic processes occurring inside lung cells, these mechanisms are expected to determine thresholds in the pulmonary carcinogenicity of chromium.

Potent carcinogenicity of uncovered halogen lamps in hairless mice.

Uncovered halogen quartz lamps, which are potently genotoxic both in prokaryotic and human cells due to the emission of far-UV radiation (UVB and UVC), were assayed for carcinogenicity in three strains of hairless mice (SKH-1, MF-1, and C3H) of both sexes. As assessed in 5 independent experiments, no spontaneous skin tumor was observed, even after more than 2 years, in 49 animals used as unexposed controls or in 29 animals exposed to halogen lamps equipped with a common glass cover. In contrast, almost all of the 185 mice exposed to the light emitted by low-voltage (12 V) and low-power (50 W) tungsten bulbs, equipped with dichroic diffusers, contracted multiple skin tumors of various histological type, both benign and malignant. Tumors were induced over a range of illuminance levels (1,000, 3,333, 5,000, and 10,000 lux) and daily exposure times (1.5, 3, 6, and 12 h). The tumor latency times were quite short and significantly correlated with the daily exposure times, as well as with the square of the distance (46-194 cm) from the illumination source. A carcinogenic effect was even observed when exposure was discontinued well before the appearance of skin lesions. Both in vitro genotoxicity data and animal carcinogenicity data support the view that the light emitted by uncovered halogen lamps, to which an enormous number of individuals are exposed, may pose carcinogenic risks to humans. Without renouncing the benefits of this modern illumination system, UV-blocking devices should be compulsory.

Induction by carcinogens and chemoprevention by N-acetylcysteine of adducts to mitochondrial DNA in rat organs.

Damage to mitochondrial DNA (mtDNA) has been postulated to be associated with aging, cancer, and other chronic degenerative diseases which are the predominant causes of death in the population. We used molecular dosimetry techniques, i.e., 32P postlabeling and synchronous fluorescence spectrophotometry, in order to evaluate the formation of adducts to both mtDNA and nuclear DNA (nDNA) in different organs of rats exposed to genotoxic carcinogens. Adducts to mtDNA were detected following administration of benzo(a)pyrene i.p. or 2-acetylaminofluorene by gavage as well as following exposure of animals to cigarette smoke. mtDNA adduct levels were consistently higher than those to nDNA in the same cells, and qualitative differences were also pointed out in the case of the aromatic amine. The oral administration of the thiol N-acetylcysteine, one of the most promising cancer chemopreventive agents endowed with nucleophilic and antioxidant properties, produced a significant decrease of mtDNA adducts in the liver of 2-acetylaminofluorene-treated rats and, sharply, in the lung and liver of rats exposed to cigarette smoke.

Specificity and inducibility of the metabolic reduction of chromium(VI) mutagenicity by subcellular fractions of rat tissues.

The mutagenicity of sodium dichromate in the Ames test was decreased as a consequence of chromium(VI) reduction by tissue postmitochondrial (S-9 or S-12) fractions from untreated rats with the following rank of efficiency: liver; kidney; and lung. The effects of lung preparations were significantly enhanced following the intratracheal administration of high doses (0.25 mg/kg) of dichromate itself, 5 times per week for 4 weeks (i.e., 20 fractionated instillations). No changes were conversely detected following single weekly doses of 1.25 mg/kg for the same period (i.e., four cumulative instillations). The local stimulation of chromium(VI) metabolism was also confirmed by testing the mutagenicity of calcium chromate and chromium trioxide, whereas the metabolism of a number of other activatable or deactivatable mutagens was not significantly affected by intratracheal treatment with chromium(VI). Of three enzyme inducers injected i.p. which modified the spectral properties and/or concentration of cytochromes P-450 in liver and lung microsomes, only Aroclor 1254 proved to stimulate chromium(VI) metabolism in lung cells. In liver cells, Aroclor 1254 and to a lower extent phenobarbital induced chromium(VI) reduction, while 3-methylcholanthrene was ineffective. Pretreatment of rats with these three compounds resulted in a selective induction of the metabolic activation of promutagens [benzo(a)pyrene and its trans-7,8-diol, 2-aminofluorene, aflatoxin B1] and of the metabolic deactivation of direct-acting mutagens [2-methoxy-6-chloro-9-[3-(2-chloroethyl)-aminopropylamino] acridine X 2HCl, epichlorohydrin, 4-nitroquinolino-N-oxide] by S-12 and microsomal fractions. These findings indicate that, in addition to already recognized detoxification mechanisms operating outside target cells (26), specific and inducible chromium-reducing pathways, mediating threshold phenomena in chromium carcinogenesis, do also occur in the intracellular environment.

Prominent role of DT-diaphorase as a cellular mechanism reducing chromium(VI) and reverting its mutagenicity.

Rat liver postmitochondrial (S-12) fractions accounted for the bulk of the activity of whole cell homogenates in reducing chromium(VI) and accordingly in decreasing its mutagenicity. Both cytosolic (S-105) and microsomal fractions concurred to this process, which in all subcellular preparations tested was selectively induced by phenobarbital and especially by Aroclor 1254, but not by 3-methylcholanthrene. Cytosolic fractions were markedly more efficient in reducing chromium(VI) than microsomal fractions recovered from the same amount of tissue (liver or lung), although the latter preparations had a higher specific activity. The microsomal activity was exclusively NADPH dependent. A minor part of the cytosolic reduction was determined by nonenzymatic components, notably by some electron donors and chiefly by reduced glutathione, which proved to reduce chromium(VI) at physiological concentrations. However, also in cytosolic fractions, the most important contribution to chromium reduction was enzyme catalyzed, as shown by the following properties: thermolability; requirement for exogenous NADH or NADPH [supplied as such or in the form of a NADPH-generating system (S-9 mix)]; and saturation by chromium(VI). The likely involvement of DT-diaphorase in this metabolic process is supported by several findings, including its sharp pH dependence and its partial suppression by known inhibitors of this enzyme protein, such as p-chloromercuribenzoate, L-thyroxine, and dicumarol (which conversely did not counteract the metabolic deactivation of the other direct-acting mutagens 2-methoxy-6-chloro-9-[3-(2-chloroethyl)aminopropylamino]acridine 2HCl and epichlorohydrin). Similarly, cytosolic reduction of chromium(VI) was partially inhibited by selective metabolic depletors of both coenzymes of DT-diaphorase, i.e., NADPH and NADH. Pretreatment of rats with enzyme inducers (phenobarbital and 3-methylcholanthrene) stimulated the activity of DT-diaphorase in liver cytosolic fractions. A dramatic stimulation (35 to 40 times over untreated controls) was produced by Aroclor 1254, which also coinduced the liver cytosolic activity of enzymes involved in the glucose 6-phosphate-dependent pathway of both nicotinamide-adenine-dinucleotide phosphate and glutathione reduction (glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and glutathione reductase). In the lung cytosol, a slight yet significant stimulation of some of these enzyme activities was determined by the daily intratracheal instillations of high doses of chromium(VI) itself for 4 weeks, a condition which has been found to enhance the pulmonary metabolism of this metal ion.

Pulmonary metabolism of mutagens and its relationship with lung cancer and smoking habits.

The S-12 fractions of lung peripheral parenchyma obtained from 80 male individuals, aged 17-71 years, were assayed as blind samples for the ability either to convert promutagens into bacterial mutagens or to decrease the potency of direct-acting mutagens in the Ames reversion test. In this system, lung preparations were completely ineffective in activating an N-nitroso compound (i.e., N-nitrosomorpholine) and polycyclic aromatic hydrocarbons [i.e., 3-methylcholanthrene and benzo(a)pyrene] or their metabolites [i.e., 3-hydroxy-benzo(a)pyrene and benzo(a)pyrene-trans-7,8-diol]. They yielded a borderline and sporadic activation of a cigarette smoke condensate, and a weak but frequent activation of an aromatic amine (i.e., 2-aminofluorene), of a heterocyclic amine (i.e., 2-amino-3,4-dimethylimidazo[4,5-f] and of a diamide (i.e., cyclophosphamide). The pulmonary metabolism was more oriented in the sense of detoxification, as shown by the consistent decrease of potency of direct-acting mutagens, including a metal (i.e., sodium dichromate), an acridine and nitrogen mustard derivative (i.e., 2-methoxy-6-chloro-9-[3-(2-chloromethyl)aminopropylamino]acridine or ICR 191), an epoxide (i.e., epichlorohydrin) and an N-oxide (i.e., 4-nitroquinoline-N-oxide). As assessed by means of a numerical score quantifying the variation of mutagenicity, a marked interindividual variability (up to 20-fold) was detected in the ability of lung specimens to affect the mutagenicity of test compounds. Such variability was not significantly related to the protein concentration of S-12 fractions, nor to the age of the patients under scrutiny, who during hospitalization were on normal institutional diets and did not receive any special drug treatment. The only significant difference between 20 noncancer and 60 lung cancer patients, irrespective of the histological type, was a decreased activation of cyclophosphamide in the latter group. Probably due to the high prevalence of smokers among lung cancer patients, a significantly decreased activation of cyclophosphamide was also observed in the group of smokers. Smoking habits were associated with a stimulation of detoxifying mechanisms which, in agreement with the results of a previous study with human alveolar macrophages (F. L. Petrilli et al., J. Clin. Invest., 77:1917-1924, 1986), was significant in the case of sodium dichromate. Such effect was further enhanced by considering only individuals smoking during the last 24 h before collecting lung specimens, and under these conditions it became significant also for ICR 191.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of mutagens and carcinogens in woodchuck liver and its relationship with hepatitis virus infection.

Thirty-six wild-caught woodchucks (Marmota monax) were characterized according to sex, weight, trapping locality, liver pathology, and serum or hepatic markers of woodchuck hepatitis virus. Liver subcellular fractions were assayed for microsomal cytochromes P-450, aryl hydrocarbon hydroxylase, glutathione, cytosolic enzymes involved in its metabolism (glutathione S-transferase, glutathione peroxidase, and glutathione reductase), in the hexose monophosphate shunt (glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase), NADH- and NADPH-dependent diaphorases, and DT diaphorase. Moreover, liver postmitochondrial fractions were assayed for their ability to activate procarcinogens [i.e., a tryptophan pyrolysate product, aflatoxin B1, 2-aminofluorene, and trans-7,8-dihydrobenzo(a)pyrene] to mutagenic metabolites in the Ames reversion test and to decrease the activity of direct-acting mutagens [i.e., 4-nitroquinoline N-oxide, 2-methoxy-6-chloro-9-[3-(2-chloroethyl)aminopropylamino]acridine X 2HCl, and sodium dichromate]. A considerable interindividual variability in metabolism was observed among the examined woodchucks. Some of the investigated parameters were more elevated in virus carriers, especially in those suffering from chronic active hepatitis, but only a few of the recorded differences (i.e., oxidized glutathione reductase and NADPH-dependent diaphorase) were statistically significant. The comparison of the monitored activities in woodchucks and in other rodent species (rat and mouse) led to the conclusion that the liver metabolism of mutagens and carcinogens in woodchucks is more oriented in the sense of activation, while detoxification mechanisms are more efficient in rats and mice.

DNA-damaging activity in vivo and bacterial mutagenicity of sixteen hydrazine derivatives as related quantitatively to their carcinogenicity.

Sixteen hydrazine derivatives (hydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, phenylhydrazine, procarbazine, isoniazid, isocarboxazid, nialamide, 2,4-dinitrophenylhydrazine, phenelzine, hydralazine, dihydralazine, carbamylhydrazine, mebanazine, iproniazid, and 1-carbamyl-2-phenylhydrazine) were tested for DNA-damaging activity by the alkaline elution technique and for mutagenic activity in the Salmonella-microsome (Ames) test. The first nine compounds listed (56%) were found to induce a significant DNA fragmentation in the liver and/or in the lung of i.p.-treated male Swiss mice. The DNA-damaging potency varied over an approximately 30-fold range. Thirteen of the first 14 compounds listed (81% of the total), isocarboxazid being inactive, were positive in the Ames test, with a broad range of activity towards the five bacterial strains of Salmonella typhimurium used (TA1535, TA100, TA1537. TA1538, and TA98) and of metabolic behavior in the presence of S-9 mix containing rat liver, mouse liver, or mouse lung postmitochondrial preparations from Aroclor-treated animals. The mutagenic potency varied over an almost 7000-fold range. For 11 of the 16 hydrazine derivatives tested, homogeneous carcinogenicity data (induction of pulmonary tumors in mice chronically treated p.o.) were available from literature. Elaboration of these data showed that carcinogenic potency varied over an approximately 1900-fold range. The five most potent carcinogens were all positive in the DNA damage test. Their carcinogenic potency varied over a 130-fold rage and their DNA-damaging potency varied over a 22-fold range. DNA-damaging potency seemed to vary on a more compressed scale, but regression analysis indicated the existence of a strong positive correlation between in vivo DNA-damaging and carcinogenic potencies, while a lack of correlation was found between mutagenic and carcinogenic potencies. There was no correlation between DNA-damaging and mutagenic potencies.

Modulation of biomarkers by chemopreventive agents in smoke-exposed rats.

Chemoprevention opens new perspectives in the prevention of cancer and other chronic degenerative diseases associated with tobacco smoking, exploitable in current smokers and, even more, in exsmokers and passive smokers. Evaluation of biomarkers in animal models is an essential step for the preclinical assessment of efficacy and safety of potential chemopreventive agents. Groups of Sprague Dawley rats were exposed whole body to a mixture of mainstream and sidestream cigarette smoke for 28 consecutive days. Five chemopreventive agents were given either with drinking water (N-acetyl-L-cysteine, 1 g/kg body weight/day) or with the diet (1,2-dithiole-3-thione, 400 mg; Oltipraz, 400 mg; phenethyl isothiocyanate, 500 mg; and 5,6-benzoflavone, 500 mg/kg diet). The monitored biomarkers included: DNA adducts in bronchoalveolar lavage cells, tracheal epithelium, lung and heart; oxidative damage to pulmonary DNA; hemoglobin adducts of 4-aminobiphenyl and benzo(a)pyrene-7,8-diol-9,10-epoxide; micronucleated and polynucleated alveolar macrophages and micronucleated polychromatic erythrocytes in bone marrow. Exposure of rats to smoke resulted in dramatic alterations of all investigated parameters. N-Acetyl-L-cysteine, phenylethyl isothiocyanate, and 5,6-benzoflavone exerted a significant protective effect on all alterations. 1,2-Dithiole-3-thione was a less effective inhibitor and exhibited both a systemic toxicity and genotoxicity in alveolar macrophages, whereas its substituted analogue Oltipraz showed limited protective effects in this model. Interestingly, combination of N-acetyl-L-cysteine with Oltipraz was the most potent treatment, resulting in an additive or more than additive inhibition of smoke-related DNA adducts in the lung and hemoglobin adducts. These results provide evidence for the differential ability of test agents to modulate smoke-related biomarkers in the respiratory tract and other body compartments and highlight the potential advantages in combining chemopreventive agents working with distinctive mechanisms.

Inhibition of angiogenesis-driven Kaposi's sarcoma tumor growth in nude mice by oral N-acetylcysteine.

The thiol N-acetyl-L-cysteine (NAC), an analogue and precursor of reduced glutathione, has cancer chemopreventive properties attributable to its nucleophilicity, antioxidant activity, and a variety of other mechanisms. We demonstrated recently that NAC has anti-invasive, antimetastatic, and antiangiogenic effects in in vitro and in vivo test systems. In the present study, s.c. transplantation of KS-Imm cells in (CD-1)BR nude mice resulted in the local growth of Kaposi's sarcoma, a highly vascularized human tumor. The daily administration of NAC with drinking water, initiated after the tumor mass had become established and detectable, produced a sharp inhibition of tumor growth, with regression of tumors in half of the treated mice along with a markedly prolonged median survival time. The production of vascular endothelial growth factor (VEGF) and certain proliferation markers (proliferating cell nuclear antigen and Ki-67) were significantly lower in Kaposi's sarcomas from NAC-treated mice than from control mice. Treatment of KS-Imm cells with NAC in vitro resulted in a dose-dependent inhibition of chemotaxis and invasion through inhibition of gelatinase-A (matrix metalloproteinase-2, MMP-2) activity without altering MMP-2 or MMP-9 mRNA levels. NAC also significantly inhibited VEGF production but did not affect proliferation markers in vitro. Reverse transcription-PCR analysis indicated that total VEGF mRNAs were reduced by 10 mM NAC. Taken together, these findings provide evidence that NAC, the safety of which even at high doses has been established in almost 40 years of clinical use, in addition to its chemopreventive action, has a strong antiangiogenic potential that could be exploited for preventing cancer progression as well as used in cancer adjuvant therapy.

Chemoprevention of carcinogen-DNA adducts and chronic degenerative diseases.

Molecular dosimetry techniques were exploited in order to assess the efficacy of experimental chemoprevention assays and to evaluate the involvement of DNA alterations, not only in cancer but also in other chronic degenerative diseases. In agreement with other protective effects previously observed in the same animal models, the thiol N-acetylcysteine (NAC) totally prevented or significantly reduced the formation of carcinogen-DNA adducts in three experimental systems in rats. Thus, as assessed by 32P postlabeling, supplement of the diet with NAC decreased both deoxyguanosine-C8-aminofluorene adducts (butanol enrichment) and deoxyguanosine-N2-acetylaminofluorene adducts (nuclease P1 enrichment) formed in rat liver following dietary administration of 2-acetylaminofluorene for 3 weeks. DNA adducts were detected by synchronous fluorescence spectrophotometry in rat liver, lung, heart, and testis following a daily i.t. instillation of benzo(a)pyrene for 3 consecutive days. The whole-body exposure of rats to mainstream cigarette smoke for 40 consecutive days resulted in the appearance of DNA adducts in heart, lung, and aorta, whereas no adduct was detected by synchronous fluorescence spectrophotometry in liver, brain, and testis. Multiple DNA adducts in the aorta were also measured by 32P postlabeling. Administration of NAC by gavage inhibited the formation of DNA adducts in all organs of rats treated with benzo(a)pyrene or exposed to cigarette smoke. It is of interest that a single chemopreventive agent can display a broad-spectrum protective ability. The selective localization of DNA adducts in different organs depends on pharmacokinetics, metabolic capacity, DNA repair efficiency, and cell proliferation rate. Whereas inhibition by NAC of DNA adducts in testis can be correlated with its demonstrated ability to prevent dominant lethal mutations, we raise the hypothesis that DNA adducts in lung, heart, and aorta may be pathogenetically associated with lung cancer, cardiomyopathies, and arteriosclerosis, respectively. In order to explore the involvement of molecular and biochemical alterations in human arteriosclerosis, we started an extensive collaborative project and report here preliminary data showing the presence of DNA adducts in aorta smooth muscle cells obtained from arteriosclerotic patients.

Biomarker alterations produced in rat lung by intratracheal instillations of air particulate extracts and chemoprevention with oral N-acetylcysteine.

Organic matter extracts were obtained from particulates recovered from 10,000-m3 air samples collected in Sicily (Italy). The overall concentrations of acenaphthene, benzo(a)pyrene, phenanthrene, anthracene, fluoranthene, and pyrene were 526 ng/m3 air in a highly polluted urban area and 48 ng/m3 in a rural area affected by motor vehicle traffic pollution. After metabolic activation, both samples were mutagenic in Salmonella typhimurium his(-) strains of the TA and YG series, with potencies in TA100 of 140.7 and 11.8 revertants/m3 air, respectively. The samples, resuspended in tricaprylin, were instilled intratracheally in Sprague-Dawley rats for 5 consecutive days, accounting for a cumulative dose in each animal of the organic fractions extracted from 400 m3 air, which corresponds approximately to the volume of air inhaled by a man in 1 month. Treatment with the rural area sample and, at higher levels, with the urban area sample resulted in the formation of adducts to lung DNA, as assessed both by synchronous fluorescence spectrophotometry and by 32P postlabeling, which showed the appearance of up to six individual adducts emerging from diffuse diagonal radioactive zones. The adducts were more efficiently detected by extraction with butanol than by digestion with nuclease P1. DNA binding of air particulate extracts was followed by alterations of early damage biomarkers only in the rats treated with the urban area sample. Repair of DNA damage in lung cells was inferred from a significant stimulation of the nuclear enzyme poly(ADP-ribose) polymerase compared with that in sham-exposed rats. Among the cells recovered by bronchoalveolar lavage, an increase in polymorphonucleate leukocytes and cells of the ciliated respiratory epithelium was accompanied by a relative decrease in pulmonary alveolar macrophages. The frequency of micronuclei was significantly enhanced both in epithelial cells and alveolar macrophages, and binucleated macrophages were also more frequent in treated rats. The thiol N-acetylcysteine, one of the most promising cancer chemopreventive agents, was administered with drinking water to a group of animals receiving the air particulate polycyclic aromatic hydrocarbon fraction from the urban area. N-acetylcysteine prevented or considerably attenuated the alterations of all monitored parameters. These findings provide evidence that, even under outstandingly high exposure conditions, it is possible to protect the respiratory tract from DNA-binding and DNA-damaging air particulate carcinogens.

Patterns of DNA adduct formation in liver and mammary epithelial cells of rats treated with 7,12-dimethylbenz(a)anthracene, and selective effects of chemopreventive agents.

7,12-Dimethylbenz(a)anthracene (DMBA) is a prototype carcinogen that induces a high yield of mammary tumors in rats after a single feeding. We investigated the induction and chemoprevention of DNA adducts in female Sprague Dawley rats receiving DMBA by gavage according to a variety of treatment schedules. The patterns of 32P-postlabeled DNA adducts in liver and mammary epithelial cells were similar to those produced by the in vitro reaction of metabolically activated DMBA with calf thymus DNA. There was a high and statistically significant correlation between dose of DMBA administered to rats (0, 0.6, 2.4, and 12 mg/kg body weight) and levels of DNA adducts in both types of cells. The regression lines relating DMBA doses to total DNA adduct levels were significantly divergent and crossed at 1.5 mg/kg body weight, indicating that, at lower doses, the formation of DNA adducts is more intense in target mammary cells, whereas at higher doses, DNA adduct levels are more elevated in liver cells, presumably due to the greater metabolic capacity of this organ. When the rats were sacrificed 7 days rather than 2 days after DMBA administration, DNA adduct levels were approximately halved in both liver and mammary cells. The observed patterns can be interpreted based on toxicokinetic factors, local and distant metabolism, removal of DNA adducts by excision repair, and cell proliferation rate. Of three chemopreventive agents given with the diet to rats treated with 12 mg of DMBA, 5,6-benzoflavone (1650 ppm) was the most effective, inhibiting DNA adduct formation in liver and mammary cells by 96.5 and 83.5%, respectively. Feeding of 1,2-dithiole-3-thione (600 ppm) inhibited this biomarker by 68.5 and 50.2%, whereas butyl hydroxyanisole (BHA; 5000 ppm) showed a significant inhibition in the liver (46.5%) but was ineffective in mammary cells (29.0%, not significant). These data correlate nicely with the results of a parallel study in which 5,6-benzoflavone, 1,2-dithiole-3-thione, and BHA inhibited formation of hemoglobin adducts by 80.0, 44.0, and 0%, respectively; the incidence of mammary tumors by 82.4, 47.1, and 5.9%, respectively; and their multiplicity by 92.6, 80.0, and 7.4%, respectively. Therefore, biomarkers of biologically effective dose are highly predictive of the efficacy of chemopreventive agents in the DMBA rat mammary model. The selective inhibition by BHA of DNA adducts in the liver but not in mammary cells is consistent with the finding that this phenolic antioxidant stimulated phase II activities in the liver but not in the mammary gland (L. L. Song et al., manuscript in preparation). In any case, the broad-spectrum inducer 5,6-BF appears to be more effective than the two monofunctional phase II inducers, presumably because an enhanced activation of DMBA to reactive metabolites is coordinated with their blocking, detoxification, and excretion.

Third International Conference on Mechanisms of Antimutagenesis and Anticarcinogenesis.

This conference, attended by scientists from 27 countries, focused on the most recent advances in the field of antimutagenesis and anticarcinogenesis. Particular emphasis was given to the mechanistic approach, which is believed to be an essential prerequisite for a safer and more effective implementation of chemoprevention of cancer and of mutation-related diseases. The arrangement of the six regular sessions basically followed and updated the detailed classification of mechanisms of inhibitors of mutagenesis and carcinogenesis proposed by S. De Flora and C. Ramel (Mutat. Res., 202: 285-306, 1988), covering both extracellular and cellular mechanisms involved in the prevention of mutations and cancer initiation, as well as in the modulation of later stages of the carcinogenesis process. In addition, a workshop was devoted to methodological aspects concerning the modulation of the genotoxic and carcinogenic response. The present report covers the main themes of overview lectures or research communications presented by more than 60 speakers. Most presentations were multi-authored, as the result of collaborative studies, in several cases at the international level, but only the names of speakers will be given.

Cancer biomarkers in human atherosclerotic lesions: detection of DNA adducts.

Since somatic mutations are suspected to contribute to the pathogenesis not only of cancer but also of atherosclerotic plaques, we measured DNA adducts in the smooth muscle layer of atherosclerotic lesions in abdominal aorta specimens taken at surgery from seven patients. DNA adducts were evaluated in three laboratories by means of different molecular dosimetry methods, including: (a) HPLC/fluorescence, which specifically identifies the DNA adducts of the anti-benzo(a)pyrene (BPDE) isomer; (b) two- and three-dimensional synchronous fluorescence spectrophotometries, which detect DNA adducts of BPDE and other reactive metabolites of polycyclic aromatic hydrocarbons; and (c) 32P postlabeling, which reveals the presence of a variety of types of DNA adducts. The HPLC/fluorescence method provided for the first time evidence for the presence of BPDE-DNA specific adducts in three of six specimens tested. Synchronous fluorescence spectrophotometry displayed broad areas of fluorescence in all seven specimens, thereby suggesting the occurrence not only of BDPE-DNA but also of other DNA adducts with similar fluorescence characteristics. All specimens were also positive at 32P postlabeling, which revealed multiple spots detectable following enrichment either with nuclease P1 or butanol, indicative of the presence of different aromatic DNA adducts. Thus, the data obtained by applying typical cancer biomarkers provide further support to the hypothesis that there may be similarities between the carcinogenic and the atherogenic processes, and in particular that genetic alterations caused by DNA-binding agents in the artery wall may be detected in atherosclerotic lesions.

Cancer biomarkers in human atherosclerotic lesions: no evidence of p53 involvement.

In order to assess similarities between the atherogenic and the carcinogenic processes, we investigated whether the p53 tumor suppressor gene, the most commonly altered gene in human cancer, may be also involved in human atherosclerotic lesions. The medium layers of abdominal aorta fragments taken at surgery from 32 patients were subjected to immunohistochemical analysis, using either monoclonal (Pab 1801) or polyclonal (CM-1) antibodies, and to molecular analysis by the PCR-based denaturing gradient gel electrophoresis approach. The results obtained indicated that p53 mutations are not involved in the pathogenesis of atherosclerotic lesions, and that no accumulation of the wild-type protein occurs in smooth muscle cells of these lesions. A polymorphism characterized by an AT to GC transition at codon 213 (CGA --> CGG) causing no aminoacid substitution (Arg --> Arg) was detected in the 10.5% of the examined patients. Our negative findings do not support the hypothesis that the atherosclerotic plaques may be pathogenetically akin to benign tumors yet they are not in contrast with this theory, since in most cases p53 is involved in advanced stages of the carcinogenesis process.

Oltipraz chemoprevention trial in Qidong, People's Republic of China: results of urine genotoxicity assays as related to smoking habits.

A Phase II chemoprevention trial was carried out in Qidong, Jiangsu Province, People's Republic of China. The recruited subjects, all of whom were positive for serum aflatoxin-albumin adducts, were divided into three treatment arms: placebo; oltipraz ([5-(2-pyrazinyl)-4-methyl-1,2-dithiol-3-thione]) given daily at 125 mg p.o.; and oltipraz given once per week at 500 mg p.o. Besides biomarkers related to aflatoxin B(1) exposure, the genotoxicity of blind-coded urine XAD-2 concentrates was evaluated in 201 subjects on the fifth and seventh week of intervention. Genotoxicity was assessed both in the Ames reversion test in strain YG1024 of Salmonella typhimurium, in the presence of an exogenous metabolic system (S9 mix), with or without beta-glucuronidase, and in a DNA repair test in Escherichia coli. Heating of concentrated urine samples or of cigarette smoke condensates was discovered to result in a significant enhancement of their mutagenicity. It was also found that the mutagenicity of condensates from the most extensively used brands of cigarettes in Qidong was much lower than that of Western cigarette brands. Urine mutagenicity was unrelated to treatment with oltipraz, intervention time, gender, and supplement of S9 mix with beta-glucuronidase. Mutagenicity was significantly but variably higher in cigarette smokers than in nonsmokers, which suggests that the urinary excretion of mutagens in the examined population was not exclusively attributable to smoking. Nevertheless, within smokers (28% of the recruited subjects; 67% of all males), the mutagenic potency was significantly correlated with the self-reported number of cigarettes smoked per day and, even more sharply, with the cotinine concentrations in urines. In conclusion, this study demonstrated the validity of urine mutagenicity assays as a biomarker of tobacco smoke exposure that can be investigated on a relatively large scale in chemoprevention trials and provided evidence that oltipraz treatment had no influence on this parameter in the examined population.