Strong Mutagen Research Articles

Fabrication of MOF-on-MOF composites by surfactant-assisted growth strategy for SPME of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants with strong carcinogenicity and mutagenicity, which cause great harm to the environment and food. Herein, a composite (NH2-MIL-88@PCN-224) was prepared through a guest PCN-224 in situ grown on the host NH2-MIL-88 by a surfactant-assisted growth strategy, and successfully applied for solid-phase microextraction (SPME) of PAHs from milk samples. The prepared SPME coatings exhibited high extraction and adsorption capacity for PAHs due to their porous structure, ultra-large specific surface area, strong π-π stacking, hydrophobic interactions and size-matching effects. The SPME-GC-FID method based on NH2-MIL-88@PCN-224 coated fibers has the significant advantages of wide linear range (1–200 ng mL−1), low detection limit (0.003–0.020 ng mL−1), high recoveries (92.15–106.64 %) and good reproducibility. This work overcomes the lattice-matching limitation by adopting a surfactant-assisted growth strategy, which offers a new direction for the preparation of ultra-high-performance SPME coatings with extremely high extraction efficiency, exceptional thermal stability, and long service life, and greatly expands the variety of MOF SPME coatings.

Instant catapult steam explosion combined with ammonia water: A complex technology for detoxification of aflatoxin-contaminated peanut cake with the aim of producing a toxicity-free and nutrients retention of animal feed

Aflatoxin is one of the most toxic biotoxins found in contaminated agricultural products. It has strong mutagenicity, carcinogenesis and teratogenicity to humans and animals. In this study, instant catapult steam explosion combined with ammonia water was examined for its potential to degrade aflatoxin B1 in peanut cake in order to improve its utilization as a toxic-free animal feed. Incubation of AFB1-containing peanut cake followed by processing with Instant Catapult Steam Explosion (ICSE) led to approximately 79.03 % degradation of AFB1, while the degradation of AFB1 was up to 91.48 % under the treatment of ICSE combined with 4 % NH₃·H₂O at 1.2 MPa in 200 s of process time. After treatment, nutrients in peanut cake were not significantly changed. The toxicity of AFB1 degradation products was evaluated and the results showed that the toxicity of these products were found to be substantially less than that possessed by AFB1. A low chemical pollution, efficient and toxic-free technology system of AFB1 degradation was established, which detoxify aflatoxin-contaminated biomass for sustainable and safe utilization of agricultural biomass as animal feed.

Rapid and simultaneous analysis of monoiodoacetic acid and inorganic iodine in drinking water by capillary electrophoresis-inductively coupled plasma mass spectrometry

Monoiodoacetic acid (MIAA) is a disinfection by-product formed during water disinfection through the oxidation of iodide, followed by a reaction with natural organic matter. It exhibits high toxicity and strong mutagenicity and is potentially carcinogenic to humans. Therefore, the simultaneous detection of MIAA and inorganic iodine can enable the safety assessment of drinking water and expand the study of the dynamic transformation process between the two forms. Currently, there is a lack of efficient and rapid universal screening methods for MIAA and inorganic iodine. In this work, a simple and efficient method was developed to combine capillary electrophoresis with inductively coupled plasma mass spectrometry using a spray-efficient nebulizer interface for the speciation analysis of I− , IO3− , and MIAA. The method is based on qualitative analysis of retention time and quantitative determination using peak area. The detection limits of the three iodine forms were 0.16 μg L−1, 0.40 μg L−1, and 1.22 μg L−1, respectively. By coupling two instruments, the method combines the advantages of rapidity and accuracy with high injection efficiency. It is also more environmentally friendly as it does not require complex pre-treatment and avoids the use of toxic organic compounds. The accuracy of this method has been validated through the incorporation of authentic samples, paving the way for its deployment in the risk assessment of substantial volumes of drinking water and the expansion of the novel approach for further investigation into the genesis and transformation of MIAA.

Air-soil cycling of oxygenated, nitrated and parent polycyclic aromatic hydrocarbons in source and receptor areas

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives, OPAHs and NPAHs, are semivolatile air pollutants which are distributed and cycling regionally. Subsequent to atmospheric deposition to and accumulation in soils they may re-volatilise, a secondary source which is understudied.We studied the direction of air-soil mass exchange fluxes of 12 OPAHs, 17 NPAHs, 25 PAHs and one alkylated PAH in two rural environments being influenced by the pollutant concentrations in soil and air, by season, and by land cover. The OPAHs and NPAHs in samples of topsoil, of ambient air particulate and gas phases and in the gas-phase equilibrated with soil were analysed by GC-APCI-MS/MS. The pollutants soil burdens show a pronounced seasonality, a winter maximum for NPAHs and PAHs and a summer maximum for OPAHs. One order of magnitude more OPAH and parent PAH are found stored in forest soil than in nearby grassland soil. Among a number of 3–4 ring PAHs, the OPAHs benzanthrone and 6H-benzo(c,d)pyren-6-one, and the NPAHs 1- and 2-nitronaphthalene, 9-nitrophenanthrene and 7-nitrobenz(a)anthracene are found to re-volatilise from soils at a rural background site in central Europe in summer. At a receptor site in northern Europe, net deposition of polycyclic aromatic compounds (PACs) prevails and re-volatilisation occurs only sporadic.Re-volatilisation of a number of PACs, including strong mutagens, from soils in summer and even in winter indicates that long-range atmospheric transport of primary PAC emissions from central Europe to receptor areas might be enhanced by secondary emissions from soils.

Phenolic compounds occurrence and human health risk assessment in potable and treated waters in Western Cape, South Africa.

Phenolic pollutants from industrial and agricultural activities pose a major threat to the world's potable water supply. The persistent micro-pollutants often find their way into drinking water sources with possible adverse human health implications. In this study, bottled water, tap water, and wastewater treatment plant (WWTP) effluent samples from the Boland region of the Western Cape, South Africa were assessed to determine 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) levels using HPLC/DAD instrumentation. The selected area is known for its vast agricultural ventures and wineries. Evaluation of the human health risk (cancer risk) for the pollutants was conducted using the hazard quotient (HQ). The Ames mutagenicity test was also conducted using the Salmonella typhimurium T98 and T100 strains and the S9 activation enzyme. Trace levels of the phenolics were detected in the samples with a range of 9.32 × 10-7-1.15 × 10-4mg/L obtained for 4-CP, and 8.80 × 10-7-1.72 × 10-4mg/L recorded for 2,4-DCP. Both compounds had levels below the limit of 0.01mg/L prescribed by South African legislation. The assessed HQ for the phenolic concentrations indicates a low level of potential ecological risk and none of the samples had a cancer risk value that exceeded the regulatory limit. The possibility of the analyzed samples causing cancer is unlikely, but non-carcinogenic adverse effects were found. Strong mutagenicity was observed for the T98 strains with a potential ability to cause mutation toward the insertion or deletion of a nucleotide. The T100 bacterial strain showed very slight mutagenicity potential, however, it is unlikely to cause any mutation. The levels of phenolics in the potable water samples may pose a significant threat to human health. Hence, screening persistent organic chemicals in potable water sources and evaluating their potential human health effects is pertinent to prevent associated health challenges.

Degradation of Aflatoxin B1 in Moldy Maize by Pseudomonas aeruginosa and Safety Evaluation of the Degradation Products

Aflatoxin B1 (AFB1) is the most harmful mycotoxin commonly found in food and feed. Pollution from AFB1 causes serious economic and health issues worldwide because it causes strong mutagenicity and carcinogenicity in humans and animals. In this study, Pseudomonas aeruginosa was used to degrade AFB1 in moldy maize, and the safety of this biological method was investigated using genotoxicity and cytotoxicity tests. Using response surface methodology, we established the optimal conditions for degrading AFB1 by the fermentation supernatant of P. aeruginosa. Under these conditions, the degradation rate of AFB1 reached 99.67%. Furthermore, the Ames mutagenicity test showed that AFB1 treated with P. aeruginosa fermentation supernatant for 72 h was not mutagenic. CCK-8 cell assay showed that AFB1 cytotoxicity was significantly reduced after degradation. Overall, our findings show that the fermentation supernatant of P. aeruginosa may be a good candidate for biodegradation of AFB1.

NATURAL WASTE USE FOR MYCOTOXINS ADSORPTION

Food safety is one of the top-priority directions. In the developed countries the international standards are observed via systematic monitoring and protection of corresponding conditions that to a considerable degree eliminates toxins penetration into the food. However, in the developing countries there is no possibility of using the international regulations, so the food is stored under unacceptable conditions that leads to its contamination. Based on the above mentioned, the considerable part of spread of strong mutagens – aflatoxins falls on storage conditions. Mycotoxins are excreted by molds, so they are the natural pollutants of food products, which may accumulate during storage period, as well. At that time, mycotoxins may enter the food chain: plant – biomass – animal – human. Therefore, the goal of our work is creation of optimum storage conditions for agricultural products in order to not promote development of microscopic fungi entered from the environment and to deliver food products to the customer in unharmed marketable condition. Mycotoxins are one of the most important biogenic toxins, which infect food, and causes mycotoxicosis – toxification of humans and animals when entering their organisms [1,2].

Quantitative analysis of polycyclic aromatic hydrocarbons (PAHs) in water by surface-enhanced Raman spectroscopy (SERS) combined with Random Forest

Polycyclic aromatic hydrocarbons (PAHs) have strong carcinogenicity, teratogenicity, mutagenicity and other adverse effects on human beings. They are one of the most dangerous pollutants, which have attracted great attention in the past decades. In this work, aiming at the actual problems that water environment is polluted and human health is threatened by PAHs, surface enhanced Raman spectroscopy (SERS) combined with Random Forest (RF) calibration models were used to quantitative analysis of phenanthrene and fluoranthene in water. Firstly, the SERS data was collected after samples mixed with Ag NPs, after 31 PAHs samples were prepared. Secondly, it was discussed how spectral preprocessing integration strategies affect on the prediction performance of the RF calibration models. And then, the effect of mutual information (MI) variable selection method on the performance of RF calibration models was explored. Finally, the RF calibration models were established for phenanthrene and fluoranthene. For the prediction set, a lowest mean relative error (MRE) and a largest determination coefficient (R2) were obtained. For quantitative analysis of phenanthrene, the final prediction performance results show that R2p is 0.9780, and MREp is 0.0369 based on the D1st-WT-RF calibration model. For fluoranthene, WT-D1st-MI-RF is a better calibration model, and corresponding to R2p and MREp are 0.9770 and 0.0694, respectively. Hence, a rapid and accurate quantitative method of PAHs is established for the real-time detection of water environmental pollution, which is intended to provide new ideas and methods for the quantitative analysis of PAHs in water.

Potent mutagenicity of an azide, 3-azido-1,2-propanediol, in human TK6 cells

Sodium azide is a strong mutagen that has been successfully employed in mutation breeding of crop plants. In biological systems, it is metabolically converted to the proximate mutagen azidoalanine, which requires further bioactivation to a putative ultimate mutagen that remains elusive. The nature of the DNA modifications induced by azides leading to mutations is also unknown. Other mutagenic organic azido compounds seem to share the same bioactivation pathway to the ultimate mutagenic species as they induce point mutations dependent on the same DNA repair pathways. We investigated mutations induced by the representative mutagen 3-azido-1,2-propanediol (azidoglycerol, AZG) in the human TK6 cell line. Until now, azides have been considered to be non-mutagens and non-carcinogens in mammals, including humans, as judged only by the conventional clastogenicity chromosomal aberration types of bioassays. Here, we show the potent mutagenicity of AZG in cultured human cells, comparable to alkylating agents such as methyl methanesulfonate at concentrations with similar lethality. The potent ability of an organic azide to induce base substitutions in a mammalian system raises an alert with respect to human exposure to organic and inorganic azido compounds.

One-pot green synthesis of poly(hexamethylenediamine-tannic acid)-bacterial cellulose composite for the reduction, immobilization, and recovery of Cr(VI)

Hexavalent chromium Cr(VI) is one of the most toxic heavy metal pollutants in water due to its high water solubility, high toxicity, strong mutagenicity and carcinogenicity. To enable efficient Cr(VI) removal from wastewater, it remains difficult to fabricate advanced adsorbents with good selectivity and high adsorption capacity in large scale. Herein, a poly(hexamethylenediamine-tannic acid)-bacterial cellulose (denoted as HTA-BC) composite was prepared by using natural raw materials with abundance, low cost and nontoxicity in a facile one-step method and applied for the decontamination of highly toxic Cr(VI). The as-synthesized HTA-BC functionalized with abundant amino and phenolic hydroxyl groups had demonstrated high capacity (534.8 mg g−1) and good selectivity for Cr(VI) scavenging. Notably, the treatment of real water samples with the HTA-BC composite could efficiently reduce the concentration of the spiked Cr(VI) below the acceptable levels for drinking water. Moreover, high-purity Cr2O3 was obtained by calcination of the Cr species-laden HTA-BC to ensure that the toxic Cr(VI) residing in the spent adsorbents can’t leak out into the surroundings, thus avoiding the secondary pollution. The natural abundance, low cost, easy availability, and sustainability of the raw materials, combined with the facile and green synthesis endowed the HTA-BC composite with great potential for not only decontaminating Cr(VI) wastewater, but also recycling Cr by calcination of the Cr-laden HTA-BC. Moreover, no secondary pollution would be brought during the synthesis and the post-treatment after the Cr(VI) removal, thus it is expected to be a green and sustainable approach for the purification of Cr(VI) containing wastewater.

Some aspects of toxic secretions accumulation in mammalian organisms

А qualitative method was used in the study. The article describes the terrain of the studied territories, the heterogeneity of the biotic component, the description of the aspects of the accumulation of toxic excretions on mammalian organisms.During the investigation, the main environmental pollutants in the Pavlodar region and their impact on the organisms of mammals were studied. Catching of animals is carried out according to standard methods using accounting lines: trap-lines and trapping grooves. The aspects of bioaccumulation of fluorine, benz (a) pyrene, heavy metals (lead, zinc, arsenic, mercury) in the organisms of animal populations inhabiting the urban areas of Pavlodar region have been determined. The main fluoride depot is bone tissue. Heavy metals tend to accumulate in the fur of mammals, as well as in the liver, kidneys, lungs and genitals. The most dangerous for animal health is benzo (a) pyrene, which can accumulate in adipose tissue. Benz (a) pyrene, being the strongest mutagen, can lead to the formation of malignant tumors. The degree of accumulation of toxic secretions directly depends on the habitat of animals and the type of food. It was found that contaminants can accumulate in bone, connective and epithelial tissues.

The 28\u2009+\u200928\xa0day design is an effective sampling time for analyzing mutant frequencies in rapidly proliferating tissues of MutaMouse animals

The Organisation for Economic Co-Operation and Development Test Guideline 488 (TG 488) uses transgenic rodent models to generate in vivo mutagenesis data for regulatory submission. The recommended design in TG 488, 28 consecutive daily exposures with tissue sampling three days later (28 + 3d), is optimized for rapidly proliferating tissues such as bone marrow (BM). A sampling time of 28 days (28 + 28d) is considered more appropriate for slowly proliferating tissues (e.g., liver) and male germ cells. We evaluated the impact of the sampling time on mutant frequencies (MF) in the BM of MutaMouse males exposed for 28 days to benzo[a]pyrene (BaP), procarbazine (PRC), isopropyl methanesulfonate (iPMS), or triethylenemelamine (TEM) in dose–response studies. BM samples were collected + 3d, + 28d, + 42d or + 70d post exposure and MF quantified using the lacZ assay. All chemicals significantly increased MF with maximum fold increases at 28 + 3d of 162.9, 6.6, 4.7 and 2.8 for BaP, PRC, iPMS and TEM, respectively. MF were relatively stable over the time period investigated, although they were significantly increased only at 28 + 3d and 28 + 28d for TEM. Benchmark dose (BMD) modelling generated overlapping BMD confidence intervals among the four sampling times for each chemical. These results demonstrate that the sampling time does not affect the detection of mutations for strong mutagens. However, for mutagens that produce small increases in MF, sampling times greater than 28 days may produce false-negative results. Thus, the 28 + 28d protocol represents a unifying protocol for simultaneously assessing mutations in rapidly and slowly proliferating somatic tissues and male germ cells.

Structure-activity relationship (SAR) studies on the mutagenic properties of 2,7-diaminofluorene and 2,7-diaminocarbazole derivatives

We discovered that 2,7-diaminofluorene or 2,7-diaminocarbazole moiety can be employed as a core structure of highly effective NS5A inhibitors that are connected through amide bonds to proline-valine-carbamate motifs. Amide bonds can be easily cleaved via various metabolic pathways upon administration into the body, and metabolites containing 2,7-diaminofluorene and 2,7-diaminocarbazole core structures have been known to be strong mutagens. To avoid the mutagenesis issue of these core structures, we examined various functional groups at the C9 or N9 position of 2,7-diaminofluorene or 2,7-diaminocarbazole, respectively, through the Ames test in TA98 and TA100 mutants of Salmonella typhimurium LT-2. We discovered that, through proper alkyl substitution at the C9 or N9 position, 2,7-diaminofluorene and 2,7-diaminocarbazole moieties can be successfully employed in drug discovery without necessarily causing mutagenicity problems.

Interacting mechanism of benzo(a)pyrene with free DNA in vitro

Polycyclic aromatic hydrocarbons are environmental pollutants with strong carcinogenicity, indirect teratogenicity, and mutagenicity. This study explored the interaction mechanism of benzo(a)pyrene with free DNA in vitro by using various analytical methods. UV–vis spectra showed that benzo(a)pyrene and DNA formed a new benzo(a)pyrene–DNA complex. The thermal melting temperature of DNA increased by 12.7 °C, showing that the intercalation of benzo(a)pyrene into DNA could promote the stability of the DNA double helix structure. The intercalation of benzo(a)pyrene with DNA in vitro was further confirmed by fluorescence microscopy with magnetic beads. Fluorescence spectra showed that the interaction between DNA and benzo(a)pyrene decreased the fluorescence intensity of benzo(a)pyrene, and the maximum quenching rate was 27.89%. The quenching mode of benzo(a)pyrene was static quenching. Thermodynamic data showed that the main driving forces were van der Waals forces and hydrogen bonds, and the reaction was spontaneous. The results of this study provided a novel insight for the establishment of polycyclic aromatic hydrocarbon capture and elimination through polycyclic aromatic hydrocarbon–DNA intercalation.

Новий морфотип овочевої кукурудзи, отриманий методом експериментального мутагенезу

Goal. To obtain genetic mutations using strong chemical mutagens, which have a broad spectrum of action (sodium azide (NaN3) and 5-bromuracil (5BrUra)), with the aim to involve in the selection process; to improve existing and create new high-yielding hybrids of vegetable corn with improved qualities. Methods. Analysis of literature sources, use of strong chemical mutagens, instrumental and statistical. Results. It was established that 5BrUra can be used as a chemical mutagen on corn plants, and point mutations, which are formed under the influence of that mutagen, are a valuable genetic material in selection practice. A new promising genotype of vegetable corn was obtained. According to the results of comparative evaluation of the phenotypes of the obtained mutant form and the studied collection samples, their significant differences were established. The branching of the obtained form of plants occurs from the base of the rod to the apex, while for known mutant forms — partially from the base to the middle of the rod, or the rod does not branch at all, and several lateral branches are formed. Conclusions. The possibility of using 5-bromuracil as a chemical mutagen on plants has been established. Point mutations, which are manifested under the influence of this mutagen, are valuable genetic material in selection practice. According to the results of comparative evaluation of the obtained mutant forms with collectible samples, it was found that the phenotype of the studied forms have significant differences. A new form of vegetable corn was obtained on the basis of cob branching, which is promising for further research and introduction into production as a new generation of baby corn.

Protective effect of hawthorn extract against genotoxicity induced by benzo(<alpha>)pyrene in C57BL/6 mice

Benzo(<alpha>)pyrene [B(<alpha>)P], widely originated from environmental pollution or food process such as roasting and frying, is a strong mutagen and potent carcinogen. Utilization of hawthorn has been reported against physical mutagens. Our study found that hawthorn extract (HE) contained abundant phenolic compounds, wherein chlorogenic acid was 2.78mg/g, procyanidine B2 was 3.58mg/g, epicatechin was 2.99mg/g DW, which may contribute to anti-genotoxicity activity. So, the role of HE against B(<alpha>)P-induced genotoxicity in C57BL/6 mice was further assessed. Fifty mice were distributed into five groups: control group, B(<alpha>)P group (30mg/kg, i.p.), B(<alpha>)P+HE-L group (100mg/kg, i.g.), B(<alpha>)P+HE-M group (200mg/kg, i.g.), B(<alpha>)P+HE-H group (400mg/kg, i.g.). Mice were orally administered with solutions of HE for 10 days and injected intraperitoneally with B(<alpha>)P for 3 days from the 8th day. Results showed that B(<alpha>)P can induce significantly pathological damage in liver, lung and spleen, as well as decrease white blood cells (WBCs). Remarkably elevated levels of reactive oxygen species (ROS), DNA strand breaks (DSBs) and G1 cell cycle arrest were also found in B(<alpha>)P group, with upregulated expressions of p-H2AX, p-p53 and p21 in bone marrow cells. With administration of HE, liver, lung and spleen injury significantly mitigated, while WBCs were evidently increased in B(<alpha>)P-treated mice. Consistently, HE markedly reduced level of ROS, DSBs and G1 cell cycle arrest accompanied by reducing expressions of p-H2AX, p-p53 and p21 in bone marrow cells. Combined, these results indicated a protective role of HE on B(<alpha>)P-induced genotoxicity.

Assessment of Pig-a, Micronucleus, and Comet Assay Endpoints in Tg.RasH2 Mice Carcinogenicity Study of Aristolochic Acid I.

A newly developed in vivo Pig-a gene mutation assay displays great potential for integration into genotoxicity tests. To obtain more evidence for application of the Pig-a assay, we integrated this assay, micronucleus test in peripheral blood (MN-pb test) and bone marrow (MN-bm test), as well as a Comet assay into a transgenic RasH2 mice carcinogenicity study. Fourteen male RasH2 mice and five wild-type (WT) mice were treated with a strong mutagen aristolochic acid I at a dose of 5 mg/kg/day for 4 consecutive weeks. Mice recovered in 5 weeks. Peripheral bloods were collected for Pig-a assay, MN-pb test, and Comet assay at several time points, while bone marrow and target organs were harvested for the MN-bm test and pathological diagnosis after mice were euthanized. Finally, 13 of the 14 RasH2 mice developed squamous cell carcinomas in the forestomach, while there were no carcinomas in the WT mice. Pig-a mutant frequencies (MFs) consecutively increased throughout the study to a maximum value of approximately 63-fold more than background. These frequencies were relative to the incidence, size, and malignant degree of tumors. Micronucleated reticulocytes increased from Day 1 to Day 49, before returning to background levels. No positive responses were observed in either the MN-bm test or the Comet assay. Results suggested that, when compared with the other two tests, the Pig-a assay persistently contributed to sustaining MFs, enhanced detection sensitivity due to the accumulation of Pig-a mutations, and demonstrated better predictability for tumorigenicity. Environ. Mol. Mutagen. 61:266-275, 2020. © 2019 Wiley Periodicals, Inc.

Removal of toxic chemical ethidium monoazide bromide using graphene oxide: Thermodynamic and kinetics study

Toxic chemical and a strong mutagen ethidium monoazide bromide (EMA) adsorption on the graphene oxide (GO) surface from aqueous solution was investigated. Influencing parameters such as temperature of solution, contact time, ethidium monoazide bromide initial concentration and pH were studied. According to the results of EMA adsorption on graphene oxide, 17 min and pH 10 was selected as the optimum time and pH, respectfully. Adsorption experiments were carried out at various temperatures from 288 to 303 K. The maximum absorption wavelength of EMA is 420 nm. In this study, pseudo-first-order, pseudo-second-order, Elovich, and the intra-particle diffusion kinetic models were used for kinetic study of EMA adsorption process. The results of kinetic study showed that there is a good fit of the experimental kinetic data of EMA adsorption on the surface of GO to the linear form of type (I) of the pseudo-second-order model, because it possess least value of average relative error ARE (%) and high value of linear regression (R2). Thermodynamic parameters; Gibbs energy (∆G°), entropy (∆S°), and enthalpy (∆H°); were calculated and results indicated that EMA adsorption on GO surface as absorbent was spontaneous and endothermic.

Abstract 3416: APOBEC3C-H gene expression and APOBEC3-mediated RNA editing in breast cancer tumors are associated with immune response and improved outcome

Abstract APOBEC enzymes are strong mutagens in breast cancer. High APOBEC3B (A3B) expression in tumors is associated with poor prognosis, but clinical significance of the other APOBEC3s (A3A, C-H) is unclear. We investigated the associations of A3A and C-H with survival and tumor immune activity in 1091 primary breast cancer tumors of The Cancer Genome Atlas project. Tumor cytolytic activity, T cell receptor (TCR) diversity, and immune cell fractions were estimated from RNA sequencing data. Patients were divided into 3 equal groups by gene expression to compare high and low expressors. Cox, Spearman and t tests were used for survival, correlation and comparison analyses, respectively. Hallmark gene-sets were used for enrichment analysis. RNA editing was determined from whole exome and RNA sequencing data for 5,208 sites of 3,630 gene transcripts that are known to undergo APOBEC3-mediated RNA editing. Examination of 55 breast cancer cell-lines of Cancer Cell Line Encyclopedia showed that A3B and A3C represented 91% of A3 gene expression. Examination of Illumina Human Body Map showed that all APOBEC3s are expressed in leukocytes at a 4-450x higher level compared to breast. In patients, expression of A3B but not other APOBEC3s was higher in tumors compared to normal tissue (4.5x). A3C-H expression levels correlated positively with both leukocyte and lymphocyte fractions in tumor (r = 0.29-0.70 and 0.20-0.50, resp.). Expression of genes related to immune function like interferon response and complement activation was enriched in high A3C-H expressors, which also had significantly more CD4 and CD8 T cells, and TCR diversity (2.3-4.0x, 2.1-5.4x and 1.3-2.1x, resp.). Concordantly, for each of A3C-H, expression correlated with tumor immune cytolytic activity (r = 0.31-0.79), which was increased 3.1-7.9x in high expressors. A3B or A3A gene expression levels had no effect on overall survival (OS), but higher expression for each of A3C-H was significantly associated with improved OS (HR = 0.45-0.66). To obtain insights on any causative mechanism for the prognostic value of A3C-H expression, we examined APOBEC3-mediated C&amp;gt;U RNA editing in the tumors. RNA editing at a mean level of 6.3% (SD = 4.3%) was observed among tumors for 767 genes. Editing was not associated with tumor subtype or pathologic stage but tumors with high editing had 1.4-11x higher gene expression of A3A and C-H (P &amp;lt;0.05 for all). TCR diversity and immune cytolytic activity in tumors correlated with RNA editing (P &amp;lt;0.001 for both), and increased editing was associated with improved disease-free interval (P &amp;lt;0.05). Even though APOBEC3C-H are DNA mutators, their high expression in tumor is associated with a strong immune response and improved survival in breast cancer. This is also observed for APOBEC3-mediated RNA editing, suggesting that RNA editing of specific genes by APOBEC3s may be promoting immune activity against cancer. Note: This abstract was not presented at the meeting. Citation Format: Mariko Asaoka, Santosh K. Patnaik, Eriko Katsuta, Takashi Ishikawa, Kazuaki Takabe. APOBEC3C-H gene expression and APOBEC3-mediated RNA editing in breast cancer tumors are associated with immune response and improved outcome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3416.

Abstract 3715: Cancer as a consequence of breaking through evolutionary constraints on longevity

Abstract It is well known that the risk of cancer increases with age, but when viewed through a comparative lens, this risk is species specific and exists at a relatively low background in the animal kingdom. The exceptions, where cancer is a major cause of mortality, are humans and companion dogs and cats. Indeed, it is estimated that more than 50% of pet dogs that reach the age of 10-years will die from cancer. Colloquially, there is a perception that there is a “cancer epidemic” in dogs caused by exposures to real or perceived mutagens, but this hypothesis is based on presumptions for which supporting evidence is weak or absent. Here, we propose an alternative hypothesis, that replacing natural selection with artificial selection for form and function, and superimposing longevity that breaks the evolutionary constraints for that species inevitably creates cancer-prone phenotypes. Modern pet dogs have achieved a social status equivalent to human family members. With this have come better health care, reduced early mortality, and greater longevity. Although dogs were first domesticated15,000 to 20,000 years ago and breeds were derived over the last 200 to 400 years, significant gains in longevity and the recognition of cancer as a major cause of mortality in pet dogs have taken place over the past 40 to 60 years, coinciding with the transition of dogs from working animals to pets. Breaking through the evolutionary constraint on longevity comes at a price: long-lived species such as elephants, whales, mole rats, and others have acquired a diversity of cancer-protective mechanisms, achieving a balance between longevity and their reproductive and energetic investments over tens of millions of years. But no such cancer-protective mechanisms have been identified in dogs, or for that matter in humans. In both species, risk increases with age, but in dogs, risk is magnified by artificial selection. Osteosarcoma provides an example that can be generalized. The underlying causal factor is selective breeding for large size, but this is only able to manifest itself because modern pet dogs exceed their evolutionarily expected lifespan by at least 2 or 3 times. We conclude that appreciating the role of longevity as a major cause of cancer in pet dogs, as well as in other model organisms will improve our ability to design and interpret experiments that will show greater fidelity when translated to humans, where the same risk factors are operative, although they are partly masked by the influence of behavioral or occupational exposures to strong mutagens. Citation Format: Jaime F. Modiano, Aaron L. Sarver. Cancer as a consequence of breaking through evolutionary constraints on longevity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3715.