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PubMed2002

Directed evolution of toluene ortho-monooxygenase for enhanced 1-naphthol synthesis and chlorinated ethene degradation.

Trichloroethylene (TCE) is the most frequently detected groundwater contaminant, and 1-naphthol is an important chemical manufacturing intermediate. Directed evolution was used to increase the activity of toluene ortho-monooxygenase (TOM) of Burkholderia cepacia G4 for both chlorinated ethenes and naphthalene oxidation. When expressed in Escherichia coli, the variant TOM-Green degraded TCE (2.5 +/- 0.3 versus 1.39 +/- 0.05 nmol/min/mg of protein), 1,1-dichloroethylene, and trans-dichloroethylene more rapidly. Whole cells expressing TOM-Green synthesized 1-naphthol at a rate that was six times faster than that mediated by the wild-type enzyme at a concentration of 0.1 mM (0.19 +/- 0.03 versus 0.029 +/- 0.004 nmol/min/mg of protein), whereas at 5 mM, the mutant enzyme was active (0.07 +/- 0.03 nmol/min/mg of protein) in contrast to the wild-type enzyme, which had no detectable activity. The regiospecificity of TOM-Green was unchanged, with greater than 97% 1-naphthol formed. The beneficial mutation of TOM-Green is the substitution of valine to alanine in position 106 of the alpha-subunit of the hydroxylase, which appears to act as a smaller "gate" to the diiron active center. This hypothesis was supported by the ability of E. coli expressing TOM-Green to oxidize the three-ring compounds, phenanthrene, fluorene, and anthracene faster than the wild-type enzyme. These results show clearly that random, in vitro protein engineering can be used to improve a large multisubunit protein for multiple functions, including environmental restoration and green chemistry.

Burkholderia cepacia↗
PubMed1983

Tumor promoter 12-O-tetradecanoylphorbol 13-acetate stimulates simian virus 40 induction by DNA-damaging agents and tumor initiators.

Simian virus 40 (SV40)-transformed Syrian hamster kidney cells produce infectious SV40 virus particles after treatments which damage DNA, such as UV irradiation or mitomycin C treatment. We have found that the induction of SV40 by DNA-damaging agents is greatly stimulated when a typical tumor promoter, 12-O-tetradecanoylphorbol 13-acetate (TPA), is present in the medium. Phorbol, which has a molecular structure similar to TPA but does not have any tumor-promoting activity, showed no such stimulatory effect on SV40 induction. This apparent synergistic effect of DNA-damaging agents and tumor promoter (TPA) was more pronounced when a tumor initiator, benzo [a]pyrene or 2-acetamido-fluorene, was combined with TPA. The effect of TPA on UV-triggered SV40 induction was greatly influenced by the timing of TPA addition to the culture medium, which was most efficient when addition of TPA was 5 to 20 h before UV irradiation. The effect of TPA, however, was not observed in SV40 rescue from hamster cells by cell fusion with permissive monkey (C7) cells.

2-Acetylaminofluorene↗
PubMed1993

Pseudomonas aeruginosa UG2 rhamnolipid biosurfactants: structural characterization and their use in removing hydrophobic compounds from soil.

The structure of two rhamnolipid biosurfactants produced by Pseudomonas aeruginosa UG2 was studied. Analyses by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy showed these two rhamnolipids to be alpha-L-rhamnopyranosyl-beta-hydroxydecanyol-beta-hydroxydecanoate and 2-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosyl-beta-hydroxydecan oyl-beta- hydroxydecanoate. The ability of UG2 rhamnolipid biosurfactants to enhance removal of naphthalene, anthracene, phenanthrene, fluorene, 2,2',5,5'-tetrachlorobiphenyl, and 3,3',4,4',5,5'-hexachlorobiphenyl into the aqueous phase was affected by soil type, hydrocarbon equilibration time, and biosurfactant adsorption to soil. Partially purified UG2 biosurfactants at a concentration of 5 g/L removed approximately 10% more hydrocarbon from a sandy loam soil than slit loam soil. High levels of UG2 rhamnolipids adsorbed to soil. In 18% (w/v) soil slurries 74, 49, 38, and 20% of 0.5, 1, 2, and 5 g UG2 rhamnolipids/L, respectively, were bound to the soil phase. Sodium dodecyl sulphate recovered lower levels and Witconol SN70 higher levels of phenanthrene and 2,2',5,5'-tetrachlorobiphenyl than UG2 biosurfactants.

Carbohydrate Sequence↗
PubMed1996

Selective enumeration of aromatic and aliphatic hydrocarbon degrading bacteria by a most-probable-number procedure.

A most-probable-number (MPN) procedure was developed to separately enumerate aliphatic and aromatic hydrocarbon degrading bacteria, because most of the currently available methods are unable to distinguish between these two groups. Separate 96-well microtiter plates are used to estimate the sizes of these two populations. The alkane-degrader MPN method uses hexadecane as the selective growth substrate and positive wells are detected by reduction of iodonitrotetrazolium violet, which is added after incubation for 2 weeks at 20 degrees C. Polycyclic aromatic hydrocarbon degraders are grown on a mixture of phenanthrene, anthracene, fluorene, and dibenzothiophene in a second plate. Positive wells turn yellow to greenish-brown from accumulation of the partial oxidation products of the aromatic substrates and they can be scored after a 3-week incubation period. These MPN procedures are accurate and selective. For pure cultures, heterotrophic plate counts on a nonselective medium and the appropriate MPN procedure provide similar estimates of the population density. Bacteria that cannot grow on the selective substrates do not produce false positive responses even when the inoculum density is very high. Thus, this method, which is simple enough for use in the field, provides reliable estimates for the density and composition of hydrocarbon-degrading microbial populations.

Bacteria↗
PubMed1996

Growth of rhodococcus S1 on anthracene.

Three slow-growing bacteria were isolated from a mixed culture enriched for growth on anthracene, using creosote-contaminated soil as the inoculum. Organisms were shown to use anthracene by the production of a clear zone around the colony after a mineral salts agar plate was sprayed with anthracene. All three bacteria were nonmotile, nonsporulating, gram-positive rods and stained acid-fast. Physiological and biochemical tests, GC content, and cell wall lipid patterns of whole cell methanolysates indicated that they belonged to the Nocardia-Mycobacterium-Rhodococcus group. On the basis of these characteristics and pyrolysis gas chromatography, they were assigned to the genus Rhodococcus. Growth of the isolates was slow on crystalline anthracene, giving a doubling time of 1.5-3 days, and they grew mainly on the crystal surface. When anthracene was supplied by precipitation from a solvent, doubling time was reduced to 1 day. All three isolates mineralized anthracene but not phenanthrene or naphthalene, nor could they grow on naphthalene, phenanthrene, fluorene, fluoranthene, acenaphthene, pyrene, chrysene, or naphthacene as sole carbon source. One isolate, Rhodococcus S1, was able to use 2-methylanthracene or 2-chloroanthracene as carbon source but not 1- or 9-substituted analogs. These results suggest that the initial enzyme attacking anthracene in these isolates has a narrow substrate specificity.

Anthracenes↗
PubMed1989

Mechanism of chloride uptake in rabbit corneal epithelium.

The mechanism of chloride uptake at the basal membrane (stromal side) of rabbit corneal epithelium was examined by observing the effects of ion transport inhibitors and ion concentrations on the stimulated epithelial short-circuit current (Isc). Loop diuretics inhibited the theophylline-stimulated peak and sustained Isc. Treatment with 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, 0.2 mM) and/or 5-(N,N-dimethyl)amiloride (0.1 mM) as well as the potent anion exchange inhibitor, 5c(+)[(2,3,9,9a-tetrahydro-1H-fluoren-7-yl)oxy]acetic acid (0.01 mM), had no significant effect on Isc. These results are consistent with Cl- uptake by a Na+-Cl- or Na+-K+-2Cl- cotransport mechanism rather than Cl(-)-HCO3(-)-OH- exchange coupled to Na+-H+ exchange. Incubation in low [Na+] or [Cl-] before stimulation with forskolin (0.1 mM) reduced both peak and sustained Isc, and saturation kinetics were exhibited. Hill coefficients for [Na+] and [Cl-] were 0.99 and 1.04, respectively, for peak Isc and 0.66 and 1.18, respectively, for sustained Isc. Apparent ion affinities for Na+ and Cl- were 13.5 and 18 mM, respectively, for peak Isc and 15 and 22 mM, respectively, for sustained Isc. These results favor Cl- uptake by a 1 Na+:1 Cl- cotransport mechanism for the rabbit corneal epithelium, but involvement of K+ in this process has not been eliminated.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2006

Identification of a lead small-molecule inhibitor of the Aurora kinases using a structure-assisted, fragment-based approach.

Aurora A and Aurora B are potential targets for anticancer drug development due to their roles in tumorigenesis and disease progression. To identify small-molecule inhibitors of the Aurora kinases, we undertook a structure-based design approach that used three-dimensional structural models of the Aurora A kinase and molecular docking simulations of chemical entities. Based on these computational methods, a new generation of inhibitors derived from quinazoline and pyrimidine-based tricyclic scaffolds were synthesized and evaluated for Aurora A kinase inhibitory activity, which led to the identification of 4-(6,7-dimethoxy-9H-1,3,9-triaza-fluoren-4-yl)-piperazine-1-carbothioic acid [4-(pyrimidin-2-ylsulfamoyl)-phenyl]-amide. The lead compound showed selectivity for the Aurora kinases when it was evaluated against a panel of diverse kinases. Additionally, the compound was evaluated in cell-based assays, showing a dose-dependent decrease in phospho-histone H3 levels and an arrest of the cell cycle in the G(2)-M fraction. Although biological effects were observed only at relatively high concentrations, this chemical series provides an excellent starting point for drug optimization and further development.

Antineoplastic Agents↗
PubMed1987

Inhibition by dehydroepiandrosterone of liver preneoplastic foci formation in rats after initiation-selection in experimental carcinogenesis.

The effect of dehydroepiandrosterone (DHEA) on the development of liver preneoplastic foci was evaluated. The experimental protocol used initiation by diethylnitrosamine (DENA), followed by selective growth induced by partial hepatectomy (PH), in rats fed an N-acetylamino-fluorene (AAF)-containing diet, and followed by a standard diet with or without 0.05% phenobarbital (PB). DHEA (0.6%) was administered in the diet for 4 or 7 weeks after DENA injection (treatments A and B) or for 3 weeks after the end of AAF feeding (treatment C). On the 7th week after DENA injection, DHEA treatments A and C caused slight decrease of body weight and 40-60% increase in liver weight and cell size; number of nuclei per g of liver was not changed. The dietary treatment also caused a marked decrease of liver glucose-6-phosphate dehydrogenase (G6PD) activity and of the percentage of the gamma-glutamyltranspeptidase (GGT)-positive liver. PB increased G6PD activity and GGT-positive liver. This effect was oblated by DHEA treatments A and C. On the 7th week, the labeling index (LI) was low in surrounding liver, and high in GGT-positive foci. PB had an enhancing effect, while DHEA treatments A and C were inhibitory. G6PD was low at the end of DHEA treatment B, but it returned to normal values 4 weeks after the end of this treatment. At this time no effect of DHEA treatment B was observed on the extent of GGT-positive liver and LI.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Acetylaminofluorene↗
PubMed1986

Adrenergic receptors in human liver plasma membranes: predominance of beta 2- and alpha 1-receptor subtypes.

Adrenergic receptors in human liver plasma membranes were characterized by radioligand binding assays. The binding of [3H]dihydroalprenolol [( 3H]DHA) to partially purified membranes was rapid, of high affinity, saturable, and stereospecific. The binding of [125I]iodocyanopindolol to the same membranes was also saturable and stereospecific, but extremely slow, and at 37 C required about 6 h for equilibration. The maximum number of binding sites from six livers determined with these two beta-receptor ligands was 36-83 fmol/mg protein. Catecholaminergic agonists competed for these binding sites in the order typical for beta 2-adrenergic receptors. IPS 339 [(tertiarybutylamino-3-ol-2-propyl)oximino-9-fluorene hydrochloride], a beta 2-selective antagonist, was at least 3 orders of magnitude more potent in inhibiting the binding of [3H]DHA than the beta 1-antagonist, atenolol. Computer-aided analysis of the competition curves as well as Hofstee transformations of the binding data indicated the predominance of the beta 2-subtype. The GTP analog guanyl-5'-yl-imidodiphosphate, decreased the binding affinity of the agonist, l-isoproterenol, indicating the modulation of agonist-promoted coupling of the receptors to guanine nucleotide regulatory proteins. The maximum number of binding sites for the binding of [3H]prazosin and [3H]dihydroergocryptine were the same (60-70 fmol/mg protein), indicating that the majority of the alpha-receptors are of the alpha 1-subtype. Competition experiments with prazosin and yohimbine confirmed the predominance of the alpha 1-receptor subtype, although the presence of alpha 2-receptors cannot be completely ruled out. These results indicate that adrenergic receptors in human liver plasma membranes are predominantly of the beta 2- and alpha 1-subtypes.

Aged↗
PubMed1997

Synthesis, affinity at 5-HT2A, 5-HT2B and 5-HT2C serotonin receptors and structure-activity relationships of a series of cyproheptadine analogues.

Cyproheptadine is a drug that shows high affinity for type 2 (5-HT2) receptors. We studied a series of compounds obtained by modification of the tricyclic system of Cyp (dibenzocycloheptadiene): 2f (thioxanthene), 2g (xanthene), 2h (dihydrodibenzocycloheptadiene), 2j (diphenyl), 2i (fluorene), and 3b (phenylmethyl). Their activities at the rat cerebral cortex 5-HT2A receptor were (pKi +/- S.E.M.): 8.80 +/- 0.11 (Cyp), 8.60 +/- 0.07 (2f), 8.40 +/- 0.02 (2g), 8.05 +/- 0.03 (2h), 7.87 +/- 0.12 (2j), 6.70 +/- 0.02 (2i) and 6.45 +/- 0.02 (3b); those at the rat stomach fundus 5-HT2B receptor (pA2 +/- S.E.M.) were: 9.14 +/- 0.25 (Cyp), 8.49 +/- 0.07 (2f), 7.58 +/- 0.58 (2g), 7.02 +/- 0.14 (2h), 6.07 +/- 0.20 (2j), and undetectable (2i, 3b): and those at the pig choroidal plexus 5-HT2C receptor (pKi +/- S.E.M.) were: 8.71 +/- 0.08 (Cyp), 8.68 +/- 0.01 (2f), 8.58 +/- 0.20 (2g), 7.95 +/- 0.05 (2h), 7.57 +/- 0.04 (2j), 6.98 +/- 0.04 (2i) and 6.63 +/- 0.20 (3b). The slopes did not differ significantly from unity. The compounds exhibited the same order of activities at every type of receptor, and the most active molecules presented certain steric (butterfly conformation of the tricyclic system) and electrostatic (proton affinity on the top of the central rings) patterns. It is concluded that the activity of cyproheptadine derivatives at 5-HT2 receptors is related to these molecular features, which make feasible a common disposition to interact with all three 5-HT2 subtypes.

Animals↗
PubMed2001

Facile solid-phase synthesis of sulfated tyrosine-containing peptides: Part II. Total synthesis of human big gastrin-II and its C-terminal glycine-extended peptide (G34-Gly sulfate) by the solid-phase segment condensation approach.

Application of the fluoren-9-ylmethoxycarbonyl (Fmoc)-based solid-phase segment condensation approach to the preparation of sulfated peptides was investigated through the synthesis of human big gastrin-II, a 34-residue sulfated tyrosine [Tyr(SO3H)]-containing peptide. Highly acid-sensitive 2-chlorotrityl resin (Clt resin) was exclusively employed as an anchor-resin for the preparation of the three peptide segments having the C-terminal Pro residue as well as of the Tyr(SO3H)-containing resin-bound segment. By using the PyBOP-mediated coupling protocol [PyBOP=benzotriazolyloxytris(pyrrolidino)phosphonium hexafluorophosphatel, we successively condensed each segment and constructed the 34-residue peptide-resin without any difficulty. The final acid treatment of the fully protected peptide-resin at low temperature (90% aqueous TFA, 0 degree C for 8 h), which can detach a Tyr(SO3H)-containing peptide from the resin and remove the protecting groups concurrently with minimum deterioration of the sulfate, afforded a crude sulfated peptide. After one-step HPLC purification, a highly homogeneous human big gastrin-II was easily obtained in 14% yield from the protected peptide-resin. The sulfate form of the C-terminal glycine-extended gastrin (G34-Gly sulfate), a posttranslational processing intermediate of gastrin-II, was also successfully prepared with the segment condensation approach (11% yield). These results demonstrated the usefulness of the segment condensation protocol for preparing large Tyr(SO3H)-containing peptides.

Gastrins↗
PubMed1989

[Synthesis of 2-oxooctahydroimidazo[1,2-alpha]pyridine-3-spiro-4'-piperidine derivatives possessing antiapomorphine activity].

4'-Carbamoyl-1,4'-bipiperidine 1 was dehydrogenated on Pd-C to give 2-oxo-2,3,5,6,7,8-hexahydroimidazo[1,2-alpha]pyridine-3-spiro-4'-p iperidine 2, which was reduced to 2-oxo-1,2,3,5,6,7,8,8a-octahydroimidazo[1,2-alpha]pyridine-3-spiro -4'- piperidine 3 with NaBH4. The iminodibenzyl and similar derivatives of 2 and 3 were synthesized and evaluated by using antiapomorphine test in mice. The derivatives of 3 had more potent antagonistic activity than those of 2 and the order of potency of 3 was: chloriminodibenzyl greater than chlordibenzocycloheptene greater than iminodibenzyl greater than iminostilbene greater than fluorene. Further chemical modification of the most active chloriminodibenzyl derivative 8, such as the substitution of Cl atom to Br atom, N-methylation on amine moiety, the replacement of imidazopyridine ring to imidazopyrrole ring, did not give any positive effect. Therefore, 8 may have potential usefulness as an antipsychotic drug.

Animals↗
PubMed1981

Characterization of beta-adrenoceptors in the dog saphenous vein.

In vitro experiments were carried out on strips of the dog saphenous vein to characterize beta-adrenoceptors mediating relaxation. Four beta-adrenoceptor agonists, isoproterenol, salbutamol, procaterol and alpha-(3,4,5-trimethoxyphenethylaminomethyl)-3,4-dihydroxybenzylalcohol hydrochloride (T-1583), all produced concentration-dependent relaxation of venous strips contracted by 10(-6) M methoxamine. These four drugs behaved as full agonists. In producing venous relaxation, procaterol was about 2.5 times more potent, and salbutamol and T-1583 were 7 and 98 times less potent than isoproterenol, on a molar basis. The concentration-relaxation response curves to the four agonists were shifted in a parallel way to the right by (t-butyl-amino-3-ol-2-propyl)oximino-9 fluorene hydrochloride (IPS 339), a selective beta 2-adrenoceptor antagonist, and by practolol. However, pA2-values for IPS 339 against the four agonists were all nearly 11.0, whereas those for practolol were all nearly 5.7. We conclude that beta-adrenoceptors in the dog saphenous vein mediating relaxation are predominantly on the beta 2 type.

Adrenergic beta-Agonists↗
PubMed2004

The abundances of fragment ions formed via skeletal rearrangements from 2,5-disubstituted-1,3,4-oxadiazoles and their theoretical calculated stabilities.

Protonated molecules of 2,5-di-R1,R2-substituted-1,3,4-oxadiazoles lose isocyanic acid (loss of mass 43) via skeletal rearrangement. This was observed in low-energy CID mass spectra recorded by using electrospray ionisation (ESI). On electron ionisation induced decomposition these compounds also reveal complex skeletal rearrangement, consisting on N2 and CO elimination, leading to the formation of fluorene or indene type ions. It was found that abundances of fragment ions formed in these processes are in good agreement with their theoretically calculated stabilities. In the case of ESI use the fragment ion abundances were calculated in relation to [M+H]+ ion abundances and for EI use, where extensive fragmentations proceed, the sums of the abundances of [M-N2-CO]+. ions and abundances of fragment ions derived from them, were expressed as a percentage of total-ion current.

Journal Article↗
PubMed2002

Molecular bases of aerobic bacterial degradation of dioxins: involvement of angular dioxygenation.

In the last decade, extensive investigation has been done on the bacterial degradation of dioxins and its related compounds, because this class of chemicals is highly toxic and has been widely distributed in the environment. These studies have revealed the primary importance of a novel dioxygenation reaction, called angular dioxygenation, in the aerobic bacterial degradation pathway of dioxin. Accompanied by the electron transport proteins, Rieske nonheme iron oxygenase catalyzes the incorporation of oxygen atoms to the ether bond-carrying carbon (the angular position) and an adjacent carbon, resulting in the irreversible cleavage of the recalcitrant aryl ether bond. The 2,2',3-trihydroxybiphenyl or 2,2',3-trihydroxydiphenyl ether derivatives formed are degraded through meta cleavage. In addition to the degradation system of dibenzofuran and dibenzo-p-dioxin (the nonchlorinated model compounds of dioxin), those of fluorene and carbazole were shown to function in dioxin degradation. Some dioxin degradation pathways have been studied biochemically and genetically. In addition, feasibility studies have shown that some dioxin-degrading strains can function in actual dioxin-contaminated soil. These studies provide useful information for the establishment of a bioremediation method for dioxin contamination. This review summarizes recent progress on molecular and biochemical bases of the bacterial aerobic degradation of dioxin and related compounds.

Aerobiosis↗
PubMed2004

Multiplicity of 2,3-dihydroxybiphenyl dioxygenase genes in the Gram-positive polychlorinated biphenyl degrading bacterium Rhodococcus rhodochrous K37.

Rhodococcus rhodochrous K37, a Gram-positive bacterium grown under alkaline conditions, was isolated for its ability to metabolize PCBs. Analysis revealed that it has eight genes encoding extradiol dioxygenase, which has 2,3-dihydroxybiphenyl 1,2-dioxygenase activity, and these genes were designated bphC1 to bphC8. According to the classification of extradiol dioxygenases [Eltis, L. D., and Bolin, J. T., J. Bacteriol., 178, 5930-5937 (1996)], BphC3 and BphC6 belong to the type II enzyme group. The other six BphCs were classified as members of the type I extradiol dioxygenase group. BphC4 and BphC8 were classified into a new subfamily of type I, family 3. Two linear plasmids, 200 kb and 270 kb in size, were found in K37, and the bphC6 and bphC8 genes were located in the 200 kb linear plasmid. Northern hybridization analysis revealed that the bphC1, bphC2, and bphC7 genes were induced in the presence of testosterone, the bphC6 gene was induced by fluorene, and the bphC8 gene was induced by biphenyl. All eight BphC products exhibited much higher substrate activity for 2,3-dihydroxybiphenyl than for catechol, 3-methylcatechol, or 4-methylcatechol.

Blotting, Northern↗
PubMed2004

Application of benzo(a)pyrene and coal tar tumor dose-response data to a modified benchmark dose method of guideline development.

Assessment of cancer risk from exposure to polycyclic aromatic hydrocarbons (PAHs) has been traditionally conducted by applying the conservative linearized multistage (LMS) model to animal tumor data for benzo(a)pyrene (BaP), considered the most potent carcinogen in PAH mixtures. Because it has been argued that LMS use of 95% lower confidence limits on dose is unnecessarily conservative, that assumptions of low-dose linearity to zero in the dose response imply clear mechanistic understanding, and that "acceptable" cancer risk rests on a policy decision, an alternative cancer risk assessment approach has been developed. Based in part on the emerging benchmark dose (BMD) method, the modified BMD method we used involves applying a suite of conventional mathematical models to tumor dose-response data. This permits derivation of the average dose corresponding to 5% extra tumor incidence (BMD0.05) to which a number of modifying factors are applied to achieve a guideline dose, that is, a daily dose considered safe for human lifetime exposure. Application of the modified BMD method to recent forestomach tumor data from BaP ingestion studies in mice suggests a guideline dose of 0.08 microg/kg/day. Based on this and an understanding of dietary BaP, and considering that BaP is a common contaminant in soil and therefore poses human health risk via soil ingestion, we propose a BaP soil guideline value of 5 ppm (milligrams per kilogram). Mouse tumor data from ingestion of coal tar mixtures containing PAHs and BaP show that lung and not forestomach tumors are most prevalent and that BaP content cannot explain the lung tumors. This calls into question the common use of toxicity equivalence factors based on BaP for assessing risk from complex PAH mixtures. Emerging data point to another PAH compound--H-benzo(c)fluorene--as the possible lung tumorigen.

Animals↗