Genetic, Epigenetic and Transcriptome Alterations in Liposarcoma for Target Therapy Selection

Liposarcoma (LPS) is one of the most common adult soft-tissue sarcomas (STS), characterized by a high diversity of histopathological features as well as to a lesser extent by a spectrum of molecular abnormalities. Current targeted therapies for STS do not include a wide range of drugs and surgical resection is the mainstay of treatment for localized disease in all subtypes, while many LPS patients initially present with or ultimately progress to advanced disease that is either unresectable, metastatic or both. The understanding of the molecular characteristics of liposarcoma subtypes is becoming an important option for the detection of new potential targets and development novel, biology-driven therapies for this disease. Innovative therapies have been introduced and they are currently part of preclinical and clinical studies. In this review, we provide an analysis of the molecular genetics of liposarcoma followed by a discussion of the specific epigenetic changes in these malignancies. Then, we summarize the peculiarities of the key signaling cascades involved in the pathogenesis of the disease and possible novel therapeutic approaches based on a better understanding of subtype-specific disease biology. Although heterogeneity in liposarcoma genetics and phenotype as well as the associated development of resistance to therapy make difficult the introduction of novel therapeutic targets into the clinic, recently a number of targeted therapy drugs were proposed for LPS treatment. The most promising results were shown for CDK4/6 and MDM2 inhibitors as well as for the multi-kinase inhibitors anlotinib and sunitinib.

Perspectives of Cell Sensitivity/Resistance Assay in Soft Tissue Sarcomas Chemotherapy

Treatment of highly malignant soft tissue sarcomas (STSs) requires multicomponent therapy including surgery, radiotherapy, and chemotherapy. Despite the advancements in targeted cancer therapies, cytostatic drug combinations remain the gold standard for STS chemotherapy. The lack of algorithms for personalized selection of STS chemotherapy leads to unhelpful treatment of chemoresistant tumors, causing severe side effects in patients. The goal of our study is to assess the applicability of in vitro chemosensitivity/resistance assays (CSRAs) in predicting STS chemoresistance. Primary cell cultures were obtained from 148 surgery samples using enzymatic and mechanical disaggregation. CSRA was performed using resazurin-based metabolic activity measurement in cells cultured with doxorubicin, ifosfamide, their combination and docetaxel, gemcitabine, and also their combination for 7 days. Both the clinical data of patients and the CSRA results demonstrated a higher resistance of some cancer histotypes to specific drugs and their combinations. The correlation between the CSRA results for doxorubicin and ifosfamide and clinical responses to the combination chemotherapy with these drugs was demonstrated via Spearman rank order correlation. Statistically significant differences in recurrence-free survival were also shown for the groups of patients formed, according to the CSRA results. Thus, CSRAs may help both practicing physicians to avoid harmful and useless treatment, and researchers to study new resistance markers and to develop new STS drugs.

Targeting Features of Curaxin CBL0137 on Hematological Malignancies In Vitro and In Vivo

The anticancer activity of Curaxin CBL0137, a DNA-binding small molecule with chromatin remodulating effect, has been demonstrated in different cancers. Herein, a comparative evaluation of CBL0137 activity was performed in respect to acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia and multiple myeloma (MM) cultured in vitro. MTT assay showed AML and MM higher sensitivity to CBL0137's cytostatic effect comparatively to other hematological malignancy cells. Flow cytometry cell cycle analysis revealed an increase in subG1 and G2/M populations after CBL0137 cell treatment, but the prevalent type of arrest varied. Apoptosis activation by CBL0137 measured by Annexin-V/PI dual staining was more active in AML and MM cells. RT2 PCR array showed that changes caused by CBL0137 in signaling pathways involved in cancer pathogenesis were more intensive in AML and MM cells. On the murine model of AML WEHI-3, CBL0137 showed significant anticancer effects in vivo, which were evaluated by corresponding changes in spleen and liver. Thus, more pronounced anticancer effects of CBL0137 in vitro were observed in respect to AML and MM. Experiments in vivo also indicated the perspective of CBL0137 use for AML treatment. This in accordance with the frontline treatment approach in AML using epigenetic drugs.

Molecular Mechanisms of Anticancer Activity of N-Glycosides of Indolocarbazoles LCS-1208 and LCS-1269

Novel indolocarbazole derivatives named LCS were synthesized by our research group. Two of them were selected as the most active anticancer agents in vivo. We studied the mechanisms of anticancer activity in accordance with the previously described effects of indolocarbazoles. Cytotoxicity was estimated by MTT assay. We analyzed LCS-DNA interactions by circular dichroism in cholesteric liquid crystals and fluorescent indicator displacement assay. The effect on the activity of topoisomerases I and II was studied by DNA relaxation assay. Expression of interferon signaling target genes was estimated by RT-PCR. Chromatin remodeling was analyzed–the effect on histone H1 localization and reactivation of epigenetically silenced genes. LCS-induced change in the expression of a wide gene set was counted by means of PCR array. Our study revealed the cytotoxic activity of the compounds against 11 cancer cell lines and it was higher than in immortalized cells. Both compounds bind DNA; binding constants were estimated—LCS-1208 demonstrated higher affinity than LCS-1269; it was shown that LCS-1208 intercalates into DNA that is typical for rebeccamycin derivatives. LCS-1208 also inhibits topoisomerases I and IIα. Being a strong intercalator and topoisomerase inhibitor, LCS-1208 upregulates the expression of interferon-induced genes. In view of LCSs binding to DNA we analyzed their influence on chromatin stability and revealed that LCS-1269 displaces histone H1. Our analysis of chromatin remodeling also included a wide set of epigenetic experiments in which LCS-1269 demonstrated complex epigenetic activity. Finally, we revealed that the antitumor effect of the compounds is based not only on binding to DNA and chromatin remodeling but also on alternative mechanisms. Both compounds induce expression changes in genes involved in neoplastic transformation and target genes of the signaling pathways in cancer cells. Despite of being structurally similar, each compound has unique biological activities. The effects of LCS-1208 are associated with intercalation. The mechanisms of LCS-1269 include influence on higher levels such as chromatin remodeling and epigenetic effects.

A Brief Overview of the Paradoxical Role of Glucocorticoids in Breast Cancer

Glucocorticoids (GCs) are stress hormones that play multiple roles in the regulation of cancer cell differentiation, apoptosis, and proliferation. Some types of cancers, such as hematological malignancies, can be effectively treated by GCs, whereas the responses of epithelial cancers to GC treatment vary, even within cancer subtypes. In particular, GCs are frequently used as supporting treatment of breast cancer (BC) to protect against chemotherapy side effects. In the therapy of nonaggressive luminal subtypes of BC, GCs can have auxiliary antitumor effects due to their cytotoxic actions on cancer cells. However, GCs can promote BC progression, colonization of distant metastatic sites, and metastasis. The effects of GCs on cell proliferation vary with BC subtype and its molecular profile and are realized via the activation of glucocorticoid receptor (GR), a well-known transcriptional factor involved in the regulation of the expression of multiple genes, cell-cell adhesion, and cell migration and polarity. This review focuses on the roles of GC signaling in the adhesion, migration, and metastasis of BC cells. We discuss the molecular mechanisms of GC actions that lead to BC metastasis and propose alternative pharmacological uses of GCs for BC treatment.

Prevention of Colorectal Carcinogenesis by DNA-Binding Small-Molecule Curaxin CBL0137 Involves Suppression of Wnt Signaling

Chemoprevention is considered a valid approach to reduce the incidence of colorectal cancer, one of the most common malignancies worldwide. Here, we investigated the tumor-preventive activity of curaxin CBL0137. This compound represents a new class of nonmutagenic DNA-binding small molecules that alter chromatin stability and inhibit the function of the histone chaperone FACT. Among downstream effects of CBL0137 treatment are activation of p53 and type I interferons and inhibition of NFκB, HSF1, and MYC. In addition, our data show that in both human and mouse colorectal cancer cells in vitro, CBL0137 inhibits the APC/WNT/β-catenin signaling pathway, which plays a key role in colon carcinogenesis. Using quantitative RT-PCR and microarray hybridization, we have demonstrated decreased expression of multiple components and downstream targets of the WNT pathway in colon cancer cells treated with CBL0137. At the same time, CBL0137 induced expression of WNT antagonists. Inhibition of WNT signaling activity by CBL0137 was also confirmed by luciferase reporter assay. Tumor-preventive activity of CBL0137 in vivo was tested in a murine model of colorectal carcinogenesis induced by 1,2-dimethylhydrazine (DMH), which is known to involve WNT pathway dysregulation. After DMH subcutaneous treatment, mice were administered CBL0137 in drinking water. Efficacy of CBL0137 in suppressing development of colorectal cancer in this model was evidenced by reduced incidence of adenocarcinomas and adenomas in both males and females and decrease in tumor multiplicity. These data support the prospective use of CBL0137 in chemoprevention of colorectal cancer as well as of other malignances associated with activated WNT signaling.

Alterations in WNT Signaling in Leukemias

The WNT/β-catenin signaling pathway plays an important role in the differentiation and proliferation of hematopoietic cells. In recent years, special attention has been paid to the role of impairments in the WNT signaling pathway in pathogenesis of malignant neoplasms of the hematopoietic system. Disorders in the WNT/β-catenin signaling in leukemias identified to date include hypersensitivity to the WNT ligands, epigenetic repression of WNT antagonists, overexpression of WNT ligands, impaired β-catenin degradation in the cytoplasm, and changes in the activity of the TCF/Lef transcription factors. At the molecular level, these impairments involve overexpression of the FZD protein, hypermethylation of the SFRP, DKK, WiF, Sox, and CXXC gene promoters, overexpression of Lef1 and plakoglobin, mutations in GSK3β, and β-catenin phosphorylation by the BCR-ABL kinase. This review is devoted to the systematization of these data.

Re-Examination of the Esophageal Squamous Cell Carcinoma Model in Rats Induced by N-Nitrososarcosine Ethyl Ester Precursors

Studies of the molecular mechanisms of esophageal cancer development have to be carried out on sufficient amount of tumor material, obtained under conditions of controlled exposure to carcinogenic factors. Esophageal cancer models on laboratory animals serve an indispensable source of this material. One of these models is esophageal cancer induction in rats by N-nitroso compound precursors. Despite adequate reproduction of human esophageal cancer, this model in fact has not been used since the 1990ies. Re-examination of esophageal cancer model, induced by N-nitrososarcosine ethyl ester precursors, is carried out and its efficiency in induction of squamous cell carcinoma is confirmed.

Rapatar, a nanoformulation of rapamycin, decreases chemically-induced benign prostate hyperplasia in rats

Benign prostatic hyperplasia (BPH) is the most common age-related disease in men. Here we tested the efficacy of Rapatar, a micellar nanoformulation of rapamycin, in two rat models of BPH: testosterone-induced and sulpiride-induced hyperplasia in ventral lobes and lateral/dorsal lobes, respectively. We found that Rapatar prevented hypertrophic and hyperplastic abnormalities and degenerative alterations in both BPH models. Rapatar normalized weight of the lateral lobes in sulpiride-induced BPH, the most relevant animal model of human BPH. Unlike Finasteride, a standard therapy of BPH, Rapatar reduced inflammation caused by sulpiride. No obvious side effects of Rapatar were detected. Our data provide a rationale for clinical trials of Rapatar in patients suffering from BPH.

Abstract 2731: Detection of blastomogenic activity of DNA minor groove binding ligands by SMART in Drosophila

The increasing request of chemical safety assessment demands alternative methods to animal experimentation. Internationally accepted short-term assays are capable of detecting five different categories of change: gene mutation; clastogenicity; aneuploidy and non-disjunction; DNA damage as measured by DNA repair; in vitro cell transformation. Recently it was demonstrated that loss of heterozigocity (LOH) through homologous recombination, causing manifestation of a recessive mutant allele, represent frequent DNA rearrangements in tumors of patients with inherited retinoblastoma and Li-Fraumeni syndrome. LOH may be detected easily using the test for somatic mutation and recombination in Drosophila elaborated more than 30 years ago in our laboratory and currently known as SMART. The assay is based on the manifestation of recessive mutant allele after inactivation of wild type one due to somatic point mutation, chromosomal deletion or loss of heterozygocity. Recently we improve SMART to detect blastomogenic activity of chemicals using wtsP4/+ heterozygous larvae. Wts gene is involved in cell cycle regulation and its homologues are tumor suppressor genes in mice and human. Hereby we demonstrate benefits of SMART in the analysis of genotoxic effects of minor groove binding ligands (MGBLs), Hoechst 33258 and Hoechst 33342, and two new bisbenzimidazols: 1-[6-(4-methylpiperazin-1-yl)-1H,3’H-2,5’-bibenzimidazol-2’-yl]methanacetamide N-[6-(4-methylpiperazin-1-yl)-1H,3’H-2,5’-bibenzimidazol-2’-yl]methanacetamide. Hoechst 33258 and Hoechst 33342 are widely used in molecular biology. Evaluation of their genotoxicity is complex due to the mode of its action. They neither alkylate DNA nor form interstrand-crosslinks or DNA adducts and bind DNA via electrostatic, hydrogen and van der Waals bonds and inhibit some enzymes, causing genetic damage in an indirect way. On account of that they are negative in the main Salmonella/ microsome reverse mutation assay using TA 98 and TA 100 strains. Marginal mutagenicity was detected only in a special TA102 strain. In the conventional 6-thioguanine resistance assay on Chinese hamster V79 cells Hoechst 33342 harbors mutagenic activity at highly toxic concentrations only. In our study all bisbenzimidazols produced significant increase of wtsP4 clone frequency at non-toxic concentrations. These dyes exhibited dose-dependent blastomogenic effect, and Hoechst 33342 showed twice higher clone frequency than others that is associated with different cell-membrane penetration. We demonstrate TOPO I inhibition for all MGBLs analyzed. Surprisingly, new derivatives were mutagenic in Ames assay. Thus, our investigation of MGBL mutagenic properties demonstrates the necessity to include the tests for both point mutagenesis and recombinogenic activity determination. Drosophila SMART assay using wtsP4/+ heterozygous larvae seems to be promising in this way.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2731. doi:10.1158/1538-7445.AM2011-2731

Comparative reactivity of mismatched and unpaired bases in relation to their type and surroundings. Chemical cleavage of DNA mismatches in mutation detection analysis

Systematic study of chemical reactivity of non-Watson-Crick base pairs depending on their type and microenvironment was performed on a model system that represents two sets of synthetic DNA duplexes with all types of mismatched and unmatched bases flanked by T.A or G.C pairs. Using comparative cleavage pattern analysis, we identified the main and additional target bases and performed quantitative study of the time course and efficacy of DNA modification caused by potassium permanganate or hydroxylamine. Potassium permanganate in combination with tetraethylammonium chloride was shown to induce DNA cleavage at all mismatched or bulged T residues, as well as at thymines of neighboring canonical pairs. Other mispaired (bulged) bases and thymine residues located on the second position from the mismatch site were not the targets for KMnO(4) attack. In contrast, hydroxylamine cleaved only heteroduplexes containing mismatched or unmatched C residues, and did not modify adjacent cytosines. However when G.C pairs flank bulged C residue, neighboring cytosines are also attacked by hydroxylamine due to defect migration. Chemical reactivity of target bases was shown to correlate strongly with the local disturbance of DNA double helix at mismatch or bulge site. With our model system, we were able to prove the absence of false-negative and false-positive results. Portion of heteroduplex reliably revealed in a mixture with corresponding homoduplex consists of 5% for bulge bases and "open" non-canonical pairs, and 10% for wobble base pairs giving minimal violations in DNA structure. This study provides a complete understanding of the principles of mutation detection methodology based on chemical cleavage of mismatches and clarifies the advantages and limitations of this approach in various biological and conformational studies of DNA.

Genetic polymorphism and variability of chemical carcinogenesis

Risk assessment in chemical carcinogenesis involves ratios of several factors. Individual responses of an organism to carcinogenic agents depend on polymorphism of enzymes responsible for metabolic activation/detoxification of carcinogens, DNA repair, and apoptosis, as well as promotion and progression in malignantly transformed cells. The effects of a particular polymorphic variant are manifested only in the case of its high penetrance. An integral effect is formed by the ratio of procarcinogenic and anticarcinogenic effects. The complexity of risk assessment depends on the gene polymorphism mosaic involved, directly or indirectly, in tumorigenesis and upstream/downstream interactions of gene products.

Spontaneous DNA-DNA interaction of homologous duplexes and factors affecting the result of heteroduplex formation

Mutation detection and mismatch repair investigations based on heteroduplex formation require a linear DNA structure. DNA branching, described previously under physiological conditions, has been analysed in the heteroduplex formation process. Symmetrical chi-structures were detected after heteroduplex formation by gel electrophoresis and electron microscopy. Buffer composition, DNA concentration and duplex end-sequences influence DNA branching. Duplexes with homologous central regions but non-complementary ends do not form hybrid heteroduplexes or hybrid Holliday junctions. Our results explain the requirements for efficient heteroduplex formation, which were previously determined empirically: special solution composition, optimal DNA concentration and GC clamps. This provides the theoretical background for further optimisation of the procedure.

NovelTP53 gene mutations in tumors of Russian patients with breast cancer detected using a new solid phase chemical cleavage of mismatch method and identified by sequencing

Mutations in the tumor-suppressor p53 gene TP53 are frequent in most human cancers including breast cancer. A new solid phase chemical cleavage of mismatch method (CCM) allowed rapid and efficient screening and analysis of the TP53 gene in DNA samples extracted from tumors of 89 breast cancer patients. The novel CCM technique utilized silica beads and the potassium permanganate/tetraethylammonium chloride (KMnO(4)/TEAC) and hydroxylamine (NH(2)OH) reactions were performed sequentially in a single tube. Mutation analysis involved amplification of five different fragments of the TP53 gene using DNA from the 89 tumor samples, then pairing of the 391 labeled PCR products and forming heteroduplexes. A total of 41 unique signals were revealed in the analysis of TP53 exons 5-9 and eight were identified by direct sequencing. The three novel mutations detected are c.600T>G (p.Asn200Lys), c.601T>G (p.Leu201Val), and c.766-768delACA (p.Thr256del). The detected mutations c.638G>T (p.Arg213Leu), c.730G>T (p.Gly244Cys), and c.758C>T (p.Thr253Ile) have not been reported in breast cancer but have been recorded in tumors of other organs. A previously reported mutation c.535C>T (p.His179Tyr) and a heterozygous polymorphism c.639A>G were also detected. Of the 41 unique signals, 36 were not identified as a sequence change. As direct sequencing requires the mutant allele concentration to be greater than 30% when the mutant allele is present in a mixture with the wild-type allele, the CCM method represents a more sensitive technique requiring a lower mutant allele concentration in the wild-type mixture compared with direct sequencing. This reveals the advantage of CCM for unknown point mutation detection in DNA samples of cancer patients.

Mechanism of spontaneous DNA-DNA interaction of homologous linear duplexes

Previously, we demonstrated the interaction of homologous linear duplexes with formation of four-way DNA structures on the model of five PCR products. We propose that homologous duplex interaction is initiated by the nucleation of several dissociated base pairs of the complementary ends of two fragments with Holliday junction formation, in which cross point migration occurs via spooling of DNA strands from one duplex to the other one, finally resulting in complete resolution into new or previously existing duplexes. To confirm that DNA-DNA interaction involves formation of four-way DNA structures with strand exchange at the cross point, we have demonstrated the strand exchange process between identical duplexes using homologous fragments, harboring either biotin label or (32)P-label. Incubation of the mixture resulted in the addition of (32)P-label to biotin-labeled fragments, and the intensity of (32)P-labeling of biotinylated fragments was dependent upon the incubation duration. DNA-DNA interaction is not based on surface-dependent denaturing, as Triton X-100 does not decrease the formation of complexes between DNA duplexes. The equilibrium concentration of Holliday junctions depends on the sequences of the fragment ends and the incubation temperature. The free energy of Holliday junction formation by the fragments with GC and AT ends differed by 0.6 kcal/mol. Electron microscopic analysis demonstrated that the majority of Holliday junctions harbor the cross point within a 300 base pair region of the fragment ends. This insight into the mechanism of homologous duplex interaction extends our understanding of different DNA rearrangements. Understanding of DNA-DNA interaction is of practical use for better interpretation and optimization of PCR-based analyses.

Induction of tumor clones in D. melanogaster wts/+ heterozygotes with chemical carcinogens

Ten chemicals were assessed for blastomogenic activity in adult wts/+ heterozygotes of D. melanogaster. All of the strong mammalian carcinogens tested (benzo(a)pyrene (B(a)P), pyrene, aflatoxin B(1), 2-acetylaminofluorene (2-AAF) and cis-dichlorodihydroxydiamminoplatinum IV) were also shown to be strong Drosophila blastomogens. They induced several times more tumors than their counterparts that are less carcinogenic for mammals (4-acetylaminofluorene (4-AAF), aflatoxins B(2) and G(2)) and 4-(methylnitrosamino)-1-(-3-pyridine)-1-butanone (NNK). Benzo(e)pyrene (B(e)P) and pyrene demonstrated minor effects. Most tumors were localized on the wing and notum, which are the derivatives of the wing disc. Humeri derived from dorsal prothoracic disc and the abdominal tergites and sternites had the lowest number of tumors. The tumor frequency in the cross of the wild type females with wts(P2)/TM6B males was different from that in the reciprocal cross. The former type of cross exhibited consistently higher tumor frequency both in the experimental and control series.

Interaction of linear homologous DNA duplexes via Holliday junction formation

Interaction of linear homologous DNA duplexes by formation of Holliday junctions was revealed by electrophoresis and confirmed by electron microscopy. The phenomenon was demonstrated using a model of five purified PCR products of different size and sequence. The double-stranded structure of interacting DNA fragments was confirmed using several consecutive purifications, S1-nuclease analysis, and electron microscopy. Formation of Holliday junctions depends on DNA concentration. A thermodynamic equilibrium between duplexes and Holliday junctions was shown. We propose that homologous duplex interaction is initiated by nucleation of several dissociated terminal base pairs of two fragments. This process is followed by branch migration creating a population of Holliday junctions with the branch point at different sites. Finally, Holliday junctions are resolved via branch migration to new or previously existing duplexes. The phenomenon is a new property of DNA. This type of DNA-DNA interaction may contribute to the process of Holliday junction formation in vivo controlled by DNA conformation and DNA-protein interactions. It is of practical significance for optimization of different PCR-based methods of gene analysis, especially those involving heteroduplex formation.

Holliday junctions are formed in concentrated solutions of purified products of DNA amplification

Previously, using concentrated solutions of PCR products of five different genes, we described the appearance in these solutions of DNA structures with molecular weights approximately twice greater than that of double-strand (ds) fragments and with even higher molecular weight. Since this phenomenon was shown to be not dependent on the size or sequence of the DNA fragments, we suggested that it is due to interaction of DNA duplexes. The double-sized dsDNA complex containing four polynucleotide strands of two DNA fragments was named a "tetramer". Our present work is devoted to elucidation of peculiarities of tetramer formation and its structure in solutions of a purified PCR product of p53 cDNA. We found that the intensity of tetramer formation depends on the concentration of the PCR product in solution. Three subsequent purifications of the PCR product were performed using DNA-binding matrix, but the tetramers appeared again after every procedure. After purification of PCR product preliminarily treated with S1-nuclease, tetramers appeared again, indicating that these structures are formed from dsDNA fragments. Purification of the tetramers on DNA-binding matrix led to the appearance of the initial dsDNA fragments as the main DNA structure. When electroelution and column filtration by centrifugation were used, the purification procedure was speeded up, and a solution with a higher amount of the tetramer was obtained. Electron microscopy revealed the presence of four-stranded symmetrical structures with crossing chains known as Holliday junctions. Thus, for the first time the ability of homologous dsDNA fragments to interact with the formation of Holliday junctions without participation of cell proteins has been demonstrated.

The expression of insecticide resistance-related cytochrome P450 forms is regulated by molting hormone in Drosophila melanogaster

The expression and enzymatic activities of insecticide resistance-related cytochrome P450B are increased by the treatment with 20-hydroxyecdysone (20HE) in D. melanogaster Oregon R flies. We have explored the role of this hormone in the maintenance of P450B basal expression. Arrest of ecdysone synthesis led to a decrease in CYP6A2 mRNA level, as well as in P450B expression and activities. This effect occurred both in insecticide susceptible (ecd1) and resistant (IRED) strains carrying the temperature-sensitive ecd mutation. The role of the 20HE in the regulation of cytochrome P450-mediated insecticide resistance has been proposed.

K-ras mutation in sputum of patients with or without lung cancer

K-ras mutation appears in about 60% of patients with non-small-cell lung cancer (NSCLC). This frequency and its presence in normal appearing tissues point to the potential of ras oncogene mutation to serve as a good biomarker. Using enriched PCR (EPCR), which enables the detection of one mutant allele in the presence of 10,000 normal alleles, we have determined the frequency of mutant ras alleles in the sputum samples of patients with or without lung cancer. Samples were collected from 17 patients with NSCLC and from 40 controls who suffered from non-oncological lung diseases, including bronchitis, asthma, and pneumonia. Of the 37 samples obtained from patients with lung cancer, 18 were found to harbor ras oncogene mutations (48%). Of the 40 cases that were free of lung cancer, five were found to harbor this mutation (12.5%). The difference between the two frequencies was found to be significant (P < 0.01). These findings indicate that (a) K-ras oncogene mutation can be identified in routinely obtained sputum samples of patients who may be at risk of developing lung cancer and (b) the higher frequency of these mutations in samples of patients with lung cancer points to the potential use of the ras mutation as a biomarker for either exogenous or endogenous exposure to carcinogens. Thus, the ability to examine sputum provides a powerful and convenient source of sampling and may be adapted for future large-scale screening.

Genotoxicity and carcinogenicity testing of 1,2-dibromopropane and 1,1,3-tribromopropane in comparison to 1,2-dibromo-3-chloropropane

The activities of 1,2-dibromopropane (DBP) and 1,1,3-tribromopropane (TBP) were studied in seven genotoxicity assays, (i) SOS-induction in E. coli, (ii) DNA repair in primary rat hepatocyte culture, (iii) the Salmonella/microsome assay, (iv) a host-mediated assay using Salmonella, (v) the somatic mutation and recombination assay in Drosophila melanogaster, (vi) HGPRT-mutagenesis assay in ARL 18 cells, and (vii) micronucleus formation assay in mouse polychromatophylic erythrocytes (PCE), forestomach (FS), glandular stomach (GS), duodenum (D), jejunum (J), cecum (C) and liver (L). The halopropanes were also tested for tumor formation in the fish Danio rerio. DBP was active in assays (ii), (v), (vii FS) and (vii L). TBP was positive in assays (ii) and (iii), strongly positive in (vii L) and borderline positive in (iv). However, neither DBP nor TBP induced tumors in fish, in contrast to the carcinogenic 1,2-dibromo-3-chloropropane. The genotoxicity and potential carcinogenicity of DBP and TBP in mammals is discussed.

Inducibility of various cytochrome P450 isozymes by phenobarbital and some other xenobiotics in Drosophila melanogaster

The inducibility of cytochrome P450 isozymes has been investigated in the Drosophila melanogaster insecticide susceptible (Oregon R) and insecticide resistant (91R) strains. Both the level and induction kinetics of 7-ethoxycoumarin O-deethylase activity were stimulated by phenobarbital (PB) to a lower extent than that of aryl hydrocarbon hydroxylase in the Oregon R strain. The basal level of the cytochrome P450-linked activities in insecticide resistant flies was higher than that noted in susceptible ones. However, treatment with PB has increased levels of 7-ethoxycoumarin O-deethylase and aryl hydrocarbon hydroxylase activities more in susceptible flies than in resistant ones. In contrast to PB, the polycyclic aromatic hydrocarbon benzo[a]pyrene induced both activities in 91R flies to a greater extent than in Oregon R ones. The potent PB-like inducer in mice but not in rats 1.4-bis[2-(dichloropyridyloxy)]-benzene failed to induce the cytochrome P450 system in D. melanogaster, when triphenyldioxane (PB-like inducer in rats but not in mice) markedly affected this system in a PB-like manner. The SDS-PAGE followed by immunoblotting analysis using monoclonal antibodies 13-2e and 8-1d have shown that the level of the 56,000 and 54,000 Da insecticide resistance-related forms has increased in the susceptible strain by PB and some other PB like inducers. The relationship between these isozymes appearance and 7-ethoxycoumarin O-deethylase activity has been discussed.

The clastogenic and mutagenic effects of ascorbigen and 1'-methylascorbigen

Ascorbigen, which occurs naturally in the human diet, and a synthetic analogue (1'-methylascorbigen), were assayed for cytotoxic and clastogenic activities in a SV40-transformed Indian Muntjac cell line (SVM), and for mutagenic activity in the Ames test using Salmonella typhimurium strains TA98 and TA100. Ascorbigen had no effect upon the clonal survival of SVM at concentrations below 0.21 mg/ml and did not induce either chromosome aberrations or sister-chromatid exchanges (SCEs) at any concentration tested up to the maximum compatible with the assay conditions; nor did it induce mutations in either Salmonella strain. In contrast, 1'-methylascorbigen was an order of magnitude more cytotoxic, demonstrating a Dq of 0.03 mg/ml, and whilst it too was not found to induce chromosome aberrations it did induce SCEs in SVM (although only at highly cytotoxic doses) and mutations in the Ames test.

The effect of the cytochrome P-450 system inducers on the development of Drosophila melanogaster

D. melanogaster development was markedly retarded and its survival decreased by larvae treatment with compounds being strong inducers of the cytochrome P-450 2B in mammals--phenobarbital (PB*), perfluorodecaline (PFD), transtilbene oxide (TSO), and triphenyldioxane (TPD). At the same time, the weak inducer hexobarbital or the selective cytochrome P-450 inducer in mice but not in rats 1,4-bis[2-(dichloropyridyl-oxy)]-benzene (DPB) did not affect the larvae development. The cytochrome P-450 1A1 inducers benzo(a)anthracene (BA) and beta-naphtoflavone (BNF) were also not effective. The toxicity of phenobarbital was shown to be decreased by the cytochrome P-450 inhibitor piperonyl butoxide by adding 20-hydroxyecdysone or by treatment with aminophylline--the indirect enhancer of ecdysone production in the larval prothoracic gland. The hypothesis of the moulting hormone degradation as the cause of elevated larvae mortality resulting from the induced high mixed function oxidase activity has been discussed.

The carcinogen benzo(e)pyrene is metabolized by DM15 cells without an uncoupling effect on their gap junctions

Benzo(e)pyrene (B(e)P) promotes carcinogenesis in the skin. Unlike some other promoters however, B(e)P does not produce an uncoupling effect on gap junction permeability in DM15 transformed fibroblasts. This study demonstrates that DM15 cells exhibit a relatively high level of B(e)P metabolism. Moreover, although pretreatment of DM15 cells with benz(a)anthracene results in an 8-fold increase of arylhydrocarbon hydroxylase activity and a 2-fold increase in the rate of B(e)P metabolism, it did not enable B(e)P to affect Lucifer Yellow transfer between DM15 cells. We conclude that neither B(e)P nor its metabolites are capable of uncoupling gap junction permeability in DM15 cells.

Xenobiotic-metabolizing enzymes and benzo[a]pyrene metabolism in the benzo[a]pyrene-sensitive mutant strain of Drosophila simulans

Basal levels of aryl hydrocarbon hydroxylase, epoxide hydrolase and glutathione S-transferase enzyme activities, cytochrome P-450 content and inducibility of enzymes with phenobarbital were found to be similar in the microsomes of D. simulans mutant strain 364yv, which is sensitive to the toxic and mutagenic effects of benzo[a]pyrene (BP), and of the wild resistant Turku strain. In contrast, increases in the rate of BP turnover per molecule of cytochrome P-450, intensity of the hemoprotein band with apparent molecular weight 56,000 and the yield of BP 7,8-dihydrodiol and 9,10-dihydrodiol occurred only in microsomes of BP-pretreated 364yv flies but not of Turku ones. It is likely that BP induces an aberrant form of cytochrome P-450 in 364yv flies with a rare mutation in one of the P-450 regulating genes.

A Drosophila simulans mutant strain sensitive to benzo[a]pyrene and 2-acetylaminofluorene

We have identified a Drosophila simulans mutant, 364 yu, that is sensitive to the toxic effects of the procarcinogens B(a)P and 2-AAF. Heterozygotes obtained by crossing it to the wild resistant Turku strain (female 364 yu x male Turku) were more sensitive than heterozygotes obtained from the reciprocal cross (female Turku x male 364 yu) to both the toxic and the mutagenic effects of B(a)P in Drosophila tests that measured lethality and the induction of somatic mosaicism, respectively. The non-carcinogens pyrene, B(e)P and 4-AAF were only weakly toxic and non-mutagenic. In the Ames test B(a)P activation with S15 fractions prepared from the homogenates of Drosophila larvae and imagoes of the 364 yu strain, as well as of the more resistant D. melanogaster y ++/+ w sn3 heterozygotes, did not significantly increase the number of S. typhimurium TA100 revertants even following pretreatment with inducers of microsomal monooxygenases (B(a)P, PCB, PB). As for 2-AAF, a certain increase was observed following only PB, but not B(a)P pretreatment. Possible mechanisms of B(a)P and 2-AAF sensitivity of the 364 yu strain, and perspectives on using it for monitoring genotoxic environmental pollutants, are discussed.

Assessment of major carcinogens and alkaloids in the tobacco and mainstream smoke of USSR cigarettes

Tobacco and mainstream smoke of USSR cigarettes were analyzed for carcinogens. The pH values of suspensions of the tobacco (5.4-5.6) and the nitrate content of the tobaccos (0.4-1.7%) were as expected for flue-cured and sun-cured tobaccos and mixtures thereof. The nicotine levels of the cigarette tobaccos (0.76-0.94%) and total alkaloid content (0.85-1.08%) were relatively low compared with tobaccos used in Western European and US cigarettes. The concentrations of tobacco-specific N-nitrosamines in the cigarette tobaccos were also low (N'-nitrosonornicotine 0.36-0.85 microgram/g) compared with those in bright, oriental and blended cigarette tobaccos in Western countries (0.3-19 microgram/g). The 2 non-filter and 4 filter cigarettes from the USSR had slow burning rates and yielded 14.0-16.7 puffs/cigarette, while puff yields for commercial cigarettes in Western countries average less than or equal to 11 puffs/cigarette. Consequently, tar and benzo(a)pyrene yields in the smoke of all cigarettes as well as nitrosamine yields were high, especially in the smoke of the filter cigarettes. It appears that an increase in the burning rates of these cigarettes should lead to lower smoke yields.

Carcinogenic substances in Soviet tobacco products

Chemical carcinogens were determined in mainstream smoke from nonfilter cigarettes produced and consumed in the USSR and in nass, a mixture of tobacco, lime, ash and cotton oil. Cigarettes contained high levels of tar (23-25 mg/cigarette) and nicotine (1.5-1.9 mg/cigarette) and, generally, a high content of polycyclic aromatic hydrocarbons, which are major epithelial carcinogens, N-nitrosamines, which are organ-specific carcinogens, and some carcinogenic metals, such as arsenic and chromium. Nass contained the tobacco-specific N-nitroso compounds, N'-nitrosonornicotine, N'-nitrosoanatabine, N'-nitrosoanabasine and 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone, as well as volatile N-nitrosamines, but at levels lower than in other types of chewing tobacco and snuff. The low levels in nass are due to the short ageing process used, in contrast to commercially produced chewing tobacco and fine-cut snuff, which are highly processed products requiring long ageing and fermentation.

The effect of complete carcinogens on intercellular transfer of lucifer yellow in fibroblast culture

The effect on permeability of gap junctions of complete powerful carcinogens, 3-methylcholanthrene (MC), 7,12-dimethylbenz(a)anthracene (DMBA), ethyl methanesulfonate (EMS), and weak carcinogens, benz(a)anthracene (BA), benzo(e)pyrene (B(e)P) as well as the aryl-hydroxylase inhibitor 7,8-benzoflavone (7,8-BF) has been studied with the use of a dye-coupling technique and transformed Djungarian hamster DM15 fibroblasts. MC, EMS and 7,8-BF were found to exert a strong inhibitory effect on cell-to-cell dye transfer. BA and DMBA had the uncoupling activity only in 2 out of 4 experiments. B(e)P was not shown to affect LY transfer between DM15 cells. The uncoupling effect of MC, 7,8-BF and EMS (only when EMS used at the concentration of 600 micrograms/ml but not 1000 micrograms/ml) appeared reversible. The causes of failure to detect DMBA and B(e)P effects on gap junctions are discussed.

Identification of tumor promoters by their inhibitory effect on intercellular transfer of lucifer yellow

The effect of the tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA), mezerein, teleocidin, anthralin, the Ca2+-ionophore A23187, butylated hydroxytoluene (BHT), dichlorodiphenyltrichloroethane (DDT) and phenobarbital (PB) on lucifer yellow transfer in cultures of SV-40-transformed Djungarian hamster fibroblasts was studied. TPA, mezerein, teleocidin, A23187, DDT and BHT exerted a strong inhibitory effect on cell-to-cell dye transfer. Anthralin uncoupled cells in 3 experiments out of 6. PB appeared to enhance lucifer yellow transfer. Sodium nitrite, a substance with unknown promoting activity, effectively uncoupled cells. All the promoters investigated had a reversible effect on the dye transfer. The value of the dye transfer method for promoter screening is discussed.

Mycotoxin induction of somatic mosaicism in Drosophila and DNA repair in mammalian liver cell cultures

The genotoxic activity of four mycotoxins has been studied. A high level of somatic mutagenesis in imaginal disk of Drosophila melanogaster larvae and DNA repair synthesis in human embryo and adult rat liver cells cultures was induced only by the strong carcinogen aflatoxin B1. Patulin somewhat elevated the level of somatic mutations in D. melanogaster, but did not elicit DNA repair synthesis. Citrinin and stachybotryotoxin were inactive in both systems.

Changes in toxic and antitumor properties of ftorafur by induction or inhibition of the microsomal enzymes activity

The inducers of microsomal drug-metabolizing enzymes phenobarbital (PB) and 20-methylcholanthrene (MC) inhibited the lethargic effect of high doses of ftorafur in C57BL/6j mice, but stimulated the animal mortality at days 4-8 after the drug administration. The opposite effect has been obtained by the combination of ftorafur with the inhibitor of the microsomal enzymes SKF 525A. Animal pretreatment with PB or with PB + MC markedly enhanced the antineoplastic activity of ftorafur in Rauscher leukemia-, leukemia La-, or hemangiopericytoma-bearing mice but seemed unlikely to afford any therapeutic advantage over this drug because the lethal toxicity of ftorafur was increased.

The retrospective study of the carcinogenic hydrocarbon benz[a]pyrene in the biosphere

The major aim of this study was to determine taking, as an example, the carcinogenic polycyclic aromatic hydrocarbon benz[a]pyrene (BaP), the present biologically active compounds in the early historical and geological epochs with the following assessment of the degree of danger of such compounds in the modern times. In the first section of work, study results of soil samples in the areas of eternal frost confirmed the presence of BaP in the frozen layers of soil aged 10 years, 100 years, 3000--4000 and 10,000 years of age. In the second part of the work, results are furnished on the BaP content in the ice of modern glaciers and their moraines, located in Kamchatka. BaP was found in 11 samples in the concentration of 0.001--0.003 microgram/l. These data represent the first results in the retrospective study of carcinogenic substances in the biosphere.

On the carcinogenic polycyclic aromatic hydrocarbon benzo(a)pyrene in volcano exhausts

The content of benzo(a)pyrene in the juvenile ashes of the volcano Tyatya (Kunashir Island, Kuriles) and in the soil, vegetation and volcanic mud collected near volcanos in Kamchatka was studied. It was concluded that volcanic activity does not play a large role in forming the background level of this carcinogen in the human environment.