Metal carcinogenesis in experimental animals

Direct Interaction with Cellular Targets as the Mechanism for Chromium Carcinogenesis

The carcinogenic activity of chromium appears to be due to its direct interaction with cellular targets and not to nonspecific solid-state carcinogenesis. Chromium was evaluated at 2 valences, Cr+3 (as CrCl3 and Cr+6 (as K2Cr2O7), for its toxicity, transforming activity, and ability to induce chromosomal aberrations in tertiary cultures of mouse fetal cells. The ID50 (dose for 50 percent inhibition of cell growth) of Cr+3 was approximately 4 times greater than that of Cr+6 after 96 h of exposure, and about 29 times greater than that of Cr+6 after 1 h of exposure. At equitoxic concentrations, both chromium valences induced the same degree of morphologic changes and alterations of growth behavior, but Cr+6 produced more chromosomal aberrations. Using autoradiography in an established cloned line of mouse cells, unscheduled DNA synthesis was observed in cells previously exposed to Cr+6 but not in cells previously exposed to Cr+3.

Strain a Mouse Lung Tumor Bioassay

This report summarizes data on the testing of 228 chemicals for carcinogenic activity by the strain A mouse lung adenoma bioassay. The assay is of six months duration and can distinguish two-fold dose differences in carcinogenic potential of compounds from a variety of chemical classes. Most compounds that induced lung tumors in strain A mice have also evoked a neoplastic response in other experimental animal bioassays and/or demonstrated mutagenic activity in various short-term tests. Recommendations are made for future studies on the: (a) distribution and metabolism of chemicals in strain A mouse lung tissue and in specific lung cell types, (b) ability of the lung adenoma bioassay to detect promoting agents, and (c) use of the bioassay to investigate the interactions of more than one chemical.

Total hip arthroplasty-related osteogenic osteosarcoma: case report and review of the literature

BACKGROUND

Orthopedic implant-related sarcoma is an exceedingly rare, but a known complication of total hip arthroplasty (THA).

CASE PRESENTATION

The authors describe clinical and radiologic features, histologic appearance, and treatment of osteogenic osteosarcoma located in the proximal femoral diaphysis associated with an unstable femoral prosthesis following THA in a 65-year-old male patient. The patient with HLA-B27 positive ankylosing spondylitis underwent arthroplasty 15 years ago.

CONCLUSIONS

The neoplastic process may be considered as an extraordinary complication of THA and might just be coincidental or the result of some derangement of the healing process in host tissue with no definitely proven hypothesis that the implants or their by-products are carcinogenic. The soluble chemical substances from the implanted prosthetic material are, at least in animals, suspected to play a vital role in the pathogenesis of the neoplastic transformation of the bone tissue. The presented case shall alert orthopedic surgeons to clinical, radiologic, and macroscopic similarities between a malignant tumor and benign lesions caused by wear debris at THA sites. At the examination of plane X-rays of patients with THA loosening, the differential diagnosis should always include osteogenic sarcoma, as well. To our knowledge, there have been only nine cases of THA-related osteogenic osteosarcomas described in the English-language literature.

Prosthetic implant associated sarcomas: a case report emphasizing surface evaluation and spectroscopic trace metal analysis

Advances with implantation of synthetic biomaterials in the setting of orthopedic surgery have clearly resulted in improvements in patient outcomes. However, all implants have been shown to have associated risks. For example, ionic and particulate debris from implants have been shown to engage in biological interactions with the native tissue, and have been associated with a wide range of metabolic, bacteriologic, immunologic, and oncogenic effects. The propensity of synthetic biomaterials to undergo degradation, producing an inflammatory reaction or other sequelae, has been well recognized. The use of porous implants, which allow for a greater interface area between native tissue and the prosthesis, may magnify the interaction between biologically active tissue and synthetic devices in some situations, giving rise to new and intriguing issues concerning biocorrosion and biocompatibility. In this article, we report the case of a high-grade conventional osteosarcoma occurring at the site of a modular porous-surfaced titanium and cobalt alloy total hip prosthesis 3 years after device implantation. Detailed spectroscopic trace metal analysis was performed and elevated levels of both vanadium and chromium, but not aluminum, nickel, or titanium were identified in the tumor.

Orthopaedic implant-related sarcoma: a study of twelve cases

Sarcoma developing in association with a metallic orthopaedic prosthesis or hardware is an uncommon, but well recognized complication. We review 12 cases of sarcomas arising in bone or soft tissue at the site of orthopaedic hardware or a prosthetic joint. Nine patients were male, and three were female. Their ages ranged from 18 to 85 (mean 55) years at the time of diagnosis of the malignancy. Five patients had undergone hip arthroplasty for degenerative joint disease, four had been treated with intramedullary nail placement for fracture, two had staples placed for fixation of osteotomy, and one had hardware placed for fracture fixation followed years later by a hip arthroplasty. The time interval between the placement of hardware and diagnosis of sarcoma was known in 11 cases and ranged from 2.5 to 33 (mean 11) years. The patients presented with pain, swelling, or loosening of hardware and were found to have a destructive bone or soft tissue mass on radiography. Two sarcomas were located primarily in the soft tissue and 10 in bone. Seven patients developed osteosarcoma, four malignant fibrous histiocytoma, and one a malignant peripheral nerve sheath tumor. All sarcomas were high grade. Three patients had metastatic disease at the time of diagnosis. Follow-up was available on eight patients: five patients died of disease 2 months to 8 years (mean 26 months) after diagnosis; two patients died without evidence of disease 7 and 30 months after diagnosis; and one patient is alive and free of disease 8 years after diagnosis. Sarcomas that occur adjacent to orthopaedic prostheses or hardware are of varied types, but are usually osteosarcoma or malignant fibrous histiocytoma. They behave aggressively and frequently metastasize. Clinically, they should be distinguished from non-neoplastic reactions associated with implants, such as infection and a reaction to prosthetic wear debris.

Cytotoxicity evaluation of 43 metal salts using murine fibroblasts and osteoblastic cells

Metallic biomaterials are generally used for replacement of structural components of the human body such as bones, joints, and tooth roots. When they are implanted inside a body, metallic biomaterials may corrode and/or wear, releasing metal ions and debris which may have toxic effects on tissues and organs. Since it is important for biomaterials to have no toxicity against a living body, a systematic and quantitative evaluation of the cytotoxicity of metallic elements is required for the development of new metallic biomaterials with superior biocompatibility. In this study, the cytotoxicity of 43 metal salts were evaluated by the colony formation method using two kinds of cultured cells. The effects of the difference in valence numbers of metallic elements in the salts on cytotoxicity were examined. The cytotoxicity of the salts of metallic elements' oxo acids was also investigated. As a result, the intensity of metal salts' cytotoxicity tends to be quite similar between MC3T3-E1 and L929 (the correlation coefficient of metal salts' IC50s is 0.82). The intensity of metal salts' cytotoxicity depends on the kinds of metallic elements, their chemical states, and concentrations. The IC50 of the highest toxic salt is 1.36 x 10(-6) mol L-1, which differs four orders of magnitude from the IC50 of the lowest toxic salt. K2Cr2O7, CdCl2, VCl3, AgNO3, HgCl2, SbCl3, BeSO4, and InCl3 are high toxic salts in which IC50s are smaller then 10(-5) mol L-1 for both or either of the cell lines. HgCl, Tl(NO3)3, GaCl3, CuCl2, MnCl2, CoCl2, ZnCl2, NiCl2, SnCl2, IrCl4, TlNO3, CuCl, RhCl3, Pb(NO3)2, Cr(NO3)3 and Bi(NO3)3 are relatively high toxic salts in which IC50s are smaller than 10(-4) mol L-1 for both or either cell lines.

Crystal structures of the copper and nickel complexes of RNase A: metal-induced interprotein interactions and identification of a novel copper binding motif

We report the crystal structures of the copper and nickel complexes of RNase A. The overall topology of these two complexes is similar to that of other RNase A structures. However, there are significant differences in the mode of binding of copper and nickel. There are two copper ions per molecule of the protein, but there is only one nickel ion per molecule of the protein. Significant changes occur in the interprotein interactions as a result of differences in the coordinating groups at the common binding site around His-105. Consequently, the copper- and nickel-ion-bound dimers of RNase A act as nucleation sites for generating different crystal lattices for the two complexes. A second copper ion is present at an active site residue His-119 for which all the ligands are from one molecule of the protein. At this second site, His-119 adopts an inactive conformation (B) induced by the copper. We have identified a novel copper binding motif involving the alpha-amino group and the N-terminal residues.

Induction of the human growth hormone gene placed under human hsp70 promoter control in mouse cells: a quantitative indicator of metal toxicity

An in vitro test method for general metal toxicity screening was designed, based on the cellular response to stress. The expression of a transfected human growth hormone gene sequence driven by the human heat-shock protein 70 promoter in NIH/3T3 cells was used as marker of noxious contact with metal compounds. Out of a series of 31 metals, 17 were competent for inducing this stress response system. According to the effective concentration and to the intensity of the response, three different clusters of positive compounds emerged and were ranked as strong, intermediate strength and weak inducers. These results correlated well with data from other in vivo and in vitro metal toxicity studies, including LD50 in mice. Apparently the positive/negative compounds also fitted well with data from genotoxicity and carcinogenesis studies on metal salts.

A status report of possible risks of base metal alloys and their components

Sensitivity to base metal alloys and the components, both generalized skin reactions and local reactions, has been well documented. With the present trend toward increased use of these alloys by the dental profession, the short- and long-term implications of their use needs to be investigated. This article reviews the background, intake, and current use of two of the most commonly used metal alloys and their components. It also describes their mechanisms of action at the cellular level, the hazard to technicians, patients, and dentists, and the current health standards for airborne exposure in dental laboratories.

Role of dietary magnesium and/or manganese variables on Ehrlich ascites tumor-bearing mice

Female Swiss albino mice were placed on seven dietary regimens for five weeks. These regimens differed only in magnesium and/or manganese contents. At the end of the feeding period, the animals were inoculated with Ehrlich ascites tumor. Ten days after transplantation, Ehrlich ascites carcinoma (EAC) cells were harvested, and all animals were killed. EAC cells and plasma samples were subjected to several biochemical tests. The results suggest several conclusions. 1. Dietary supplements of magnesium and/or manganese have no effect on retarding tumor growth in vivo. 2. Dietary restriction of manganese and combined magnesium and manganese gave promising effects on retarding tumor growth in vivo. 3. Dietary magnesium deficiency, per se, had no significant effect on tumor regression in vivo. 4. In contrast to in vitro studies, manganese supplementation appeared to exert no effect on tumor progression in vivo. 5. Magnesium supplementation seemed to have no effect on tumor progression in vivo, which is in agreement with in vitro studies.

Difference circular dichroism studies of copper and nickel binding to D-penicillamine in the presence of human serum albumin

The binding of copper and nickel to D-penicillamine in the presence of human serum albumin (HSA) has been studied using difference circular dichroism (CD). The difference CD spectra due to penicillamine in HSA-Cu2+-penicillamine systems at pH 6 are indicative of ternary complexes between HSA, copper and penicillamine. On the other hand, the difference spectra due to penicillamine in HSA-Ni2+-penicillamine systems resemble that due to the Ni2+-penicillamine complex, indicating that mostly binary complexes are formed. The formation of stable complexes between penicillamine and copper or nickel (whether they are of the binary or mixed ligand type) may be important in the therapeutic action of this drug.

Chloride ion nuclear magnetic resonance spectroscopy probe studies of copper and nickel binding to serum albumins

The binding of Cu2+ and Ni2+ to bovine, dog, and human serum albumin has been studied by the 35Cl NMR probe technique. The number of primary copper sites were estimated to be 1.3 for human serum albumin, 3.1 for bovine serum albumin, and 6.6 for dog serum albumin. A similar number of primary nickel sites was determined for each of these albumins. On the basis of the chloride probe experiments, it appears that both copper and nickel have the same binding sites on albumin.

Cytogenetic effects of cadmium accumulation on water hyacinth (Eichhornia crassipes)

Cadmium was bioassayed to observe cytogenetic effects in the water hyacinth (Eichhornia crassipes). Plants were exposed for 96 hr to freshwater containing 0.01, 0.05, 0.10, 1.5, and 10 mg/liter of cadmium. Metal concentrations in tissues were determined by atomic absorption spectrophotometry. The highest level was found in roots, thus root-tip cells were used for cytogenetic studies; after 24 hr of exposure, micronuclei, c-mitotic effects, and pycnosis were detected and after 48 hr polyploidy was observed. A linear relationship between frequencies of micronuclei and cadmium concentrations was found: at 1.5, and 10 mg/liter micronuclei numbers were always the lowest. The inhibition of cell proliferation. shown by the low mitotic index, was proportional to the concentration and time of exposure. From the results presented in this paper it may be concluded that water hyacinth is a good sensor, due to its fast rate of metal accumulation, which allows an easy way to determine the presence of potential mutagenic compounds in water.

Copper and nickel binding to canine serum albumin. A circular dichroism study

The binding of copper and nickel to canine serum albumin has been studied using circular dichroism. In the 320-700 nm region, only a single positive extremum was observed at about 664-667.5 nm for copper bound to canine serum albumin. The intensity of this extremum was found to increase until a Cu2+/albumin molar ratio of 3 was reached. Further addition of Cu2+ led to a decrease in ellipticity. The absence of any extrema in the 560-570 and 480-510 nm regions showed that histidines were not involved in copper binding to canine albumin. In the case of nickel, initial binding was found to take place at the N-terminal tripeptide. At higher nickel to albumin molar ratios, circular dichroism spectra indicated the presence sulfur containing ligands but showed no evidence for the involvement of histidines. Canine serum albumin was found to bind six or more Cu2+ and Ni2+ ions with affinities that are lower than for human or bovine serum albumin.

Ion-specific electrode study of copper binding to serum albumins

The binding of copper to bovine, human, rabbit, rat, and porcine albumin has been studied using a cupric ion-specific electrode. The results were analyzed in terms of Scatchard expression assuming two classes of independent binding sites. The high-affinity constants for copper binding to the albumin show the same trend as the first association constants for nickel binding, namely, rabbit greater than human greater than rat greater than pig. Despite the similarity in the primary amino acid sequence for human and bovine serum albumin, the former has only one high-affinity site for copper, while the latter has more than three sites.

Malignant lymphoma associated with internal fixation of a fractured tibia

A case of malignant lymphoma in association with the plating of a fractured tibia 17 years previously is presented. The literature is briefly reviewed, and attention is drawn to the reported association between tumor and internal fixation in animals.

Electron-transport cytochrome P-450 system is involved in the microsomal metabolism of the carcinogen chromate

The kinetics of chromate reduction by liver microsomes isolated from rats pretreated with phenobarbital or 3-methylcholanthrene with NADPH or NADH cofactor have been followed. Induction of cytochrome P-450 and NADPH-cytochrome P-450 reductase activity in microsomes by phenobarbital pretreatment caused a decrease in the apparent chromate-enzyme dissociation constant, Km, and an increase in the apparent second-order rate constant, kcat/Km, but did not affect the kcat of NADPH-mediated microsomal metabolism of chromate. Induction of cytochrome P-448 in microsomes by 3-methylcholanthrene pretreatment did not affect the kinetics of NADPH-mediated reduction of chromate by microsomes. The kinetics of NADH-mediated microsomal chromate reduction were unaffected by the drug treatments. The effects of specific enzyme inhibitors on the kinetics of microsomal chromate reduction have been determined. 2'-AMP and 3-pyridinealdehyde-NAD, inhibitors of NADPH-cytochrome P-450 reductase and NADH-cytochrome b5 reductase, inhibited the rate of microsomal reduction of chromate with NADPH and NADH. Metyrapone and carbon monoxide, specific inhibitors of cytochrome P-450, inhibited the rate of NADPH-mediated microsomal reduction of chromate, whereas high concentrations of dimethyl-sulfoxide (0.5 M) enhanced the rate. These results suggest that the electron-transport cytochrome P-450 system is involved in the reduction of chromate by microsomal systems. The NADPH and NADH cofactors supply reducing equivalents ultimately to cytochrome P-450 which functions as a reductase in chromate metabolism. The lower oxidation state(s) produced upon chromate reduction may represent the ultimate carcinogenic form(s) of chromium. These studies provide evidence for the role of cytochrome P-450 in the activation of inorganic carcinogens.

Carcinogenicity, mutagenicity and teratogenicity of nickel

Nickel is widely used in the metallurgical industry, and although not released extensively into the environment, may represent a hazard to human health. Owing to their low absorption from the gastrointestinal tract, nickel compounds, except nickel carbonyl, are essentially non-toxic after ingestion. Epidemiological investigations and experimental studies have demonstrated that certain nickel compounds are extremely potent carcinogens after inhalation, but also that the carcinogenic risk is limited to conditions of occupational exposure. The relatively small number of mutagenicity studies performed up to now do not yet allow definite conclusions as to whether nickel is mutagenic. Nickel can cross the placenta and has embryotoxic and teratogenic properties. The principal hazard of nickel to man, beside its carcinogenicity, however, is its ability to provoke reactions of sensitization.

Nickel carbonate induces DNA-protein crosslinks and DNA strand breaks in rat kidney

DNA lesions were observed in kidney nuclei isolated from rats 20 h after i.p. injection with nickel carbonate. Dose-dependent, nickel-induced DNA crosslinks and DNA single strand breaks were detected using the alkaline elution technique. The DNA crosslinks were determined to be completely DNA-protein in nature. The DNA damage induced by nickel carbonate is discussed relative to the carcinogenicity of nickel compounds.

A 2 year oral carcinogenicity study with cadmium on rats

A longterm 2-year feeding study on cadmium using CdCl2 . 1H2O has been performed on Wistar-rats. The tested Cd2+-dietary levels were 1, 3, 10 and 50 ppm, respectively. Fifty male and 50 female rats were used for each of the levels. Hundred rats of each sex served as controls. No effects occurred on food intake and survival rate at any dietary level. Growth was unchanged up to 10 ppm whereas 50 ppm resulted in lower weight gain in males only. Histopathological evaluation of a large variety of tissues revealed a number of tumours. Cadmium administered orally was not associated with an increased incidence of total numbers of tumours or of any specific type of neoplasia, although the highest level tested resulted in adverse effects.

Carcinogenicity, teratogenicity and mutagenicity of arsenic

Arsenic may be released into the environmental through industrial processes and through the generation of power from coal. It is also widely used in agriculture and was formerly used extensively in medicine. For the general population, exposure to arsenic occurs mainly through the ingestion of foodstuffs containing inorganic and organic arsenicals. Trivalent arsenicals are regarded as being primarily sulfhydryl reagents with the result they inhibit a number of thiol-dependent enzymic systems in various tissues. Arsenite also has an effect on DNA synthesis and DNA repair. Owing to its lower affinity for hydroxy and thiol groups, pentavalent arsenate inhibits fewer enzymic systems. Although there is no reliable evidence that arsenic produces tumors in experimental animals, epidemiological studies show that the incidence of epidermoid carcinomas of the skin and lungs, and of pre-cancerous dermal keratoses, is significantly increased in human subjects who have been chronically exposed to arsenic compounds by oral or respiratory routes. Arsenic appears to be one of the only teratogenic members of the Group V metals. Most of the studies performed on the mutagenic activity of arsenic have provided positive results. They involve experiments on microorganisms, plant material and Drosophila as well as observations on the ability of this metal to induce, in vitro and in vivo, chromosomal aberrations in mammalian cells.

Chromate metabolism in liver microsomes

The carcinogenicity and mutagenicity of various chromium compounds have been found to be markedly dependent on the oxidation state of the metal. The carcinogen chromate was reduced to chromium(III) by rat liver microsomes in vitro. Metabolism of chromate by microsomal enzymes occurred only in the presence of either NADPH or NADH as cofactor. The chromium(III) generated upon metabolism formed a complex with the NADP(+) cofactor. Significant binding of chromium to DNA occurred only when chromate was incubated in the presence of microsomes and NADPH. Specific inhibitors of the mixed function oxidase enzymes, 2'-AMP, metyrapone, and carbon monoxide, inhibited the rate of reduction of chromate by microsomes and NADPH. The possible relationship of metabolism of chromate and its interaction with nucleic acids to its carcinogenicity and mutagenicity is discussed.

Mechanisms of metal carcinogenesis

Experimental observations that pertain to mechanisms of metal carcinogenesis are summarized, with emphasis upon (a) interactions of metals with nucleic acids in vitro; (b) impairment by metals of the fidelity of DNA replication by DNA polymerase in vitro; (c) mutagenicity of metals in microorganisms; (d) cytogenetic aberrations induced by metals in tissue culture cells; (e) induction by metals of neoplastic transformation of tissue culture cells; and (f) nuclear uptake of metals in vivo and concomitant inhibitory effects of metals on synthesis of nucleic acids. Considered in toto, the experimental data support the somatic mutation hypothesis of chemical carcinogenesis. Sufficient experimental evidence is available regarding four carcinogenic metals (As, Be, Cr, and Ni) to permit speculations about the molecular reactions whereby these metals may induce somatic mutations.

Oxidation of inactive trivalent chromium to the mutagenic hexavalent form

Soluble trivalent chromium compounds (chromium potassium sulfate, chromium nitrate, chromium chloride, neochromium and chromium alum) were inactive for Salmonella typhimurium TA100, even at milligram amounts per plate. No effect could be detected either in the absence or in the presence of rat-liver, lung or muscle microsomal fractions, of rat-muscle mitochondria (with or without ATP), of oxidized glutathione (GSSG), or of human serum, plasma or erythrocyte lysates. Conversely, addition of a strongly oxidizing agent (potassium permanganate) resulted in toxic effects in plates incorporating more than 40--80 microgram of compounds and elicited a dose-effect mutagenic response at 10--40 microgram per plate. These effects could be ascribed to oxidation of chromium from the trivalent to the active hexavalent state. Insoluble chromite, as tested in the spot test, was spontaneously mutagenic, owing to contamination of the industrial product with hexavalent chromium. The results obtained may be useful to interpret the findings of carcinogenicity tests and to predict health hazards linked to chromium.

Lung tumor response in mice to metals and metal salts

Two studies tested the ability of metals and their salts to produce lung tumors in strain A mice. Of 13 compounds examined, lead subacetate, manganous sulfate, molybdenum trioxide, and nickelous acetate elicited a weakly carcinogenic response following intraperitoneal injection. Nine metallic compounds were negative. There was no evidence of cocarcinogenic effect between metals and the chemical carcinogen, 3-methylcholanthrene. On the basis of these and other data, recommendation is made for further investigations in metal carcinogenesis.

MP35N: a corrosion resistant, high strength alloy for orthopedic surgical impants: bio-assay results

A cobalt based alloy, MP35N, with excellent mechanical properties has been recently introduced as a material for surgical orthopedic implants. A study was made of local and systemic host response to this material in two different mammal species. The implantation time ranged from one to 12 months. The result of this study indicated: MP35N produces a degree of local tissue response comparable to that of 316L stainless steel. No systemic side effects were observed during the implantation times included in this study.