Cancer risk from inorganics

Long-Term Outcomes After Metal-on-Metal Total Hip Arthroplasty With a 28-mm Head: A 17- to 23-Year Follow-Up Study of a Previous Report

BACKGROUND

Second-generation, metal-on-metal total hip arthroplasty (MoM THA) using a 28-mm head has shown favorable results compared with large head MoM THA. The purpose of this study is to evaluate the long-term outcomes of cementless primary MoM THA with a 28-mm head and the incidence of osteolysis using computed tomography.

METHODS

A total of 92 patients (53 men and 39 women) who underwent primary cementless MoM THA (114 hips) with a 28-mm head were enrolled in this study. Their mean age was 46.2 years at the time of surgery. The mean follow-up duration was 20 years. The Harris hip score, presence of thigh or groin pain, radiographic results, presence of peri-implant osteolysis, histologic analysis, and Kaplan-Meier survival curves were evaluated.

RESULTS

The mean preoperative Harris hip score of 50.5 improved to 85.1 at the final follow-up. Eight patients (8 hips) experienced groin pain, but none had thigh pain. Twelve revisions (6.2%) were performed including 10 hips for aseptic loosening with osteolysis and 2 hips for periprosthetic fracture around the stem. At 23 years, 91% of patients were free from revision of the acetabular component due to aseptic loosening and 90.1% were free from revision of both femoral and acetabular components due to any reason. Osteolysis was identified around the cup in 12 cases (10.5%) and around the stem in 7 cases (6.1%).

CONCLUSION

MoM THA with a 28-mm head showed a relatively low rate of aseptic implant loosening at a mean follow-up of 20 years.

Ensemble modeling coupled with six element concentrations in human blood for cancer diagnosis

Six important metal contents (i.e., zinc, barium, magnesium, calcium, copper, and selenium) in blood samples coupled with an ensemble classification algorithm have been used for the classification of normal people and cancer patients. A dataset containing 42 healthy samples and 32 cancer samples was used for experiment. The prediction results from this method outperformed those from the newly developed support vector machine, i.e., a sensitivity of 100%, a specificity of 95.2%, and an overall accuracy of 98.6%. It seems that ELDA coupled with blood element analysis can serve as a valuable tool for diagnosing cancer in clinical practice.

Classification models for detection of lung cancer based on nine element distribution of urine samples

The detection of lung cancer has a special value in the diagnosis of cancer diseases. Based on nine elemental concentrations (i.e., chromium, iron, manganese, aluminum, cadmium, copper, zinc, nickel, and selenium) in urine samples and an ensemble linear discriminant analysis (ELDA), a detection method for lung cancer has been developed. A dataset containing 30 healthy samples and 27 lung cancer samples is used for experiment. The whole dataset was first split into a training set with 29 samples and a test set with 28 samples. The prediction results from the ELDA classifier were compared with those from single Fisher's discriminate analysis (FDA). On the test set, the ELDA classifier achieved better performance, that is, a sensitivity of 100%, a specificity of 86.7%, and an overall accuracy of 92.9%, while the FDA classifier had a sensitivity of 92.3%, a specificity of 93.3%, and an overall accuracy of 92.9%. The superiority of ELDA to FDA is ascribed to the fact that ELDA can model more nonlinear relationships through the cooperation of several single models, suggesting that ensemble modeling is more advisable in such a task.

Comparative evaluation of trace metal distribution and correlation in human malignant and benign breast tissues

Selected trace metals were analyzed in human malignant and nonmalignant (benign) breast tissue samples by the flame atomic absorption spectrophotometric method. In malignant tissues, dominant mean concentrations were revealed by Na, K, Ca, Mg, Fe, Zn, and Al at 927, 552, 231, 61.7, 36.5, 18.3, and 8.94 microg/g, respectively, while the mean metal levels in benign tissues were 903, 435, 183, 63.3, 24.7, 14.5, and 10.1 microg/g, respectively. Average concentrations of Cd, Co, Cr, Cu, Fe, Mn, K, Ca, and Zn were noted to be significantly higher in the malignant tissues compared with the benign tissues. Significantly strong correlations (r > 0.50) in malignant tissues were observed between Mn and Co, Mn and Cd, Cd and Cr, Fe and Mn, Cd and Co, Fe and Co, Mg and Pb, Cd and Fe, Mg and Ni, Pb and Ni, Ni and Sr, and Fe and Pb, whereas, Cd and Co, Cd and Mn, Co and Mg, Co and Mn, Cu and Mn, Co and Ni, Mg and Ni, Cd and Cu, Cd and Ni, Ca and Mg, Mn and Pb, Cu and Ni, Fe and Ni, Cd and Mg, Co and Cu, Cr and Na, and Cd and Cr revealed strong and significant relationships in benign tissues at p < 0.001. Principal component analysis of the metals data yielded six principal components for malignant tissues and five principal components for benign tissues, with considerably different loadings, duly supported by cluster analysis. The study revealed a considerably different pattern of distribution and mutual correlations of trace metals in the breast tissues of benign and cancerous patients.

Reduction of wear in total hip replacement prostheses by amorphous diamond coatings

Wear-debris-induced periprosthetic bone loss and aseptic loosening is regarded as the main long-term problem of total hip replacements (THRs). In this study the amount of wear debris from articulating surfaces of THRs was reduced so as to be close to negligible by the use of high-quality amorphous diamond (AD) coatings deposited by pulsed plasma arc techniques. The wear rates determined in a commercial hip simulator for 15 million walking cycles (corresponding to about 15 years of clinical use) in serum lubrication were even 1,000,000 times lower than the clinical values for conventional THRs (polyethylene-metal or metal-metal pairs). Elimination of wear debris and good biomechanical performance should provide a substantial improvement of the clinical longevity of the THRs.

A comparative analysis of the heavy metal loading of small mammals in different regions of Bulgaria II: chromosomal aberrations and blood pathology

Heavy metal content was monitored in small mammals inhabiting mountain ecosystems and two industrial polluted regions in Bulgaria. Rodents (Microtus arvalis, M. rossiaemeridionalis, Clethrionomys glareolus, Pitymys subterraneus, Chionomys nivalis, Apodemus flavicollis, A. sylvaticus, and Mus macedonicus) were used as zoomonitors. Pathological changes in chromosome status, hematological indices, and blood cell morphology were analyzed in the context of heavy metal bioaccumulation. Significant correlations were obtained between the heavy metal load of zoomonitors and the frequency of chromosomal aberrations and pathological changes in erythrocytes (mainly micronuclei and basophilic granulations). It is suggested that mercury is a strong damaging factor for chromosomes and red blood cell apparatus.

The counterface, surface smoothness, tolerances, and coatings in total joint prostheses

Proper counterface material combinations, surface finish, and tolerances of contact surfaces are important issues in minimizing friction, wear, and corrosion of total joint prostheses. In the current study, the potential of novel amorphous diamond coatings to solve some present problems in total joint prostheses was studied by using tribological tests with a hip joint simulator and pin-on-disk testers. Based on the tests, the wear of amorphous diamond is negligible compared with conventional hip joint materials (10,000 to 1,000,000 times lower). The coefficient of friction of diamond-coated artificial hip joint was 0.03 to 0.06 when tested in saline solution with loads from 200 to 1000 kg for as many as two million cycles. The friction remained stable throughout the tests. Methylmethacrylate (bone cement) is a typical source of third body wear particles in cemented total hip replacements. The wear tests showed that bone cement (containing hard ceramic particles of barium sulfate or zirconia) severely scratched cobalt chromium molybdenum alloy samples. These scratches enhance the wear of softer counterpart materials, such as polyethylene or bone cement, whereas diamond-coated surfaces remained undamaged. High quality amorphous diamond coatings offer superior stability (minimal wear debris release in surrounding tissues) and good biomechanical performance.

Cancer risk after metal on metal and polyethylene on metal total hip arthroplasty

The incidence of cancer after metal on metal total hip arthroplasty (McKee-Farrar) and polyethylene on metal total hip arthroplasty (Brunswik, Lubinus) was compared with that of the general population in Finland. The mean followup time for the patients who had metal on metal total hip arthroplasty was 15.7 (9092 person years) and for the patients who had polyethylene on metal total hip arthroplasty it was 12.5 years (19,846 person years). One hundred thirteen malignant cancers were observed in patients who had metal on metal total hip arthroplasty and 212 were observed in patients who had polyethylene on metal total hip arthroplasty. The standardized incidence ratio for all cancers of the metal on metal arthroplasty group was 0.95 (95% confidence limits 0.79-1.13) and that of the polyethylene on metal arthroplasty group was 0.76 (95% confidence limits 0.68-0.86). The risk of total cancer in the patients who had metal on metal total hip arthroplasty was 1.23-fold compared with that of the patients who had polyethylene on metal total hip arthroplasty. Both groups had significantly less lung cancer than the general population: the leukemia incidence in the patients who had metal on metal total hip arthroplasty was slightly increased (observed to experienced 7/3.03, standardized incidence ratio 0.61; 95% confidence limits 0.17-1.56). The leukemia rate of the patients who had metal on metal total hip arthroplasty was 3.77-fold compared with that of the patients who had polyethylene on metal total hip arthroplasty, but this difference was not statistically significant. No sarcomas were observed at the site of the prosthesis. The incidence of the other forms of cancers did not differ significantly from those in the general population. The observed variation in the incidence of different cancers among patients who had total hip arthroplasty compared with the general population suggests that factors other than total hip arthroplasty play a major role in the origin of cancer.

Enhanced metallothionein gene expression is associated with protection from cadmium-induced genotoxicity in cultured rat liver cells

Metallothioneins (MTs) are low-molecular-weight, cysteine-rich proteins that appear to play an important role in the cellular defense system against cadmium toxicity. Although substantial evidence exists demonstrating a reduction in cadmium toxicity concomitant with MT induction, little is known about the possible effects of stimulation of MT synthesis on cadmium-induced genotoxicity. Thus, the alkaline elution technique was used to assess single-strand DNA damage (SSD) in TRL-1215 cells, a liver-derived cell line shown to have inducible MT gene expression. The SSD accumulated over a 2-h time period in a time-dependent manner following exposure to 500 microM CdCl2. Low-concentration cadmium pretreatment (10 microM CdCl2, 24 h) provided protection against the genotoxicity of high-concentration cadmium (500 microM CdCl2, 2 h). A 2-h exposure to 500 microM CdCl2 had no effect on viability, as assessed using a tetrazolium-dye based assay, in cells from either the pretreated or nonpretreated group. Metallothionein was induced in a time-dependent manner by low-concentration cadmium pretreatment: Exposure for 24 and 48 h resulted in 3.3- and 6.4-fold increases, respectively. In addition, a 24-h exposure to low-concentration cadmium resulted in an increase in MT-I gene expression. Cadmium accumulation was 2.6-fold greater in low-concentration cadmium-pretreated cells as compared to nonpretreated cells. These data demonstrate that low-concentration cadmium pretreatment provides protection against cadmium-induced single-strand DNA damage and support the hypothesis that this protection is due to stimulation of MT gene expression.

Effect of dietary vitamin D3 (cholecalciferol) on colon carcinogenesis induced by 1,2-dimethylhydrazine in male Fischer 344 rats

This study examined the effect of increasing dietary vitamin D on chemically induced colon carcinogenesis. Male Fischer 344 rats were first injected with 1,2-dimethylhydrazine (200 mg/kg) and then fed one of five dietary levels of vitamin D as cholecalciferol (250, 1,000, 2,000, 4,000, and 10,000 IU/kg diet) for nine months. Dietary vitamin D3 had no effect on weight gain. Plasma 25-hydroxyvitamin D3 levels were similar for the 1,000 and 2,000 IU/kg groups but varied in a dose-related manner for the other groups. Vitamin D did not significantly alter the tumor incidence in either the distal or the proximal colon. No significant differences in the labeling index were found in either the proximal or the distal colon. Within the distal colon, the proliferative zone increased in a dose-related manner. Distribution of labeled cells within the crypt compartments was not affected by dietary vitamin D. Bone and serum minerals in general were unaffected by dietary vitamin D. This study shows that, at this level of dietary calcium, vitamin D did not affect 1,2-dimethylhydrazine-induced colon carcinogenesis.

The genetic toxicology of cobalt

Genetic and related effects of cobalt compounds are reviewed and discussed with respect to mechanisms. In prokaryotic assays, Co(II) salts generally are nonmutagenic. In Saccharomyces cerevisiae, CoCl2 is mutagenic to mitochondrial genes and weakly mutagenic or nonmutagenic to chromosomal genes. In plants, Co(II) salts induced gene mutations and chromosomal aberrations. In mammalian cells in vitro, Co(II) compounds caused DNA strand breaks, sister-chromatid exchanges and aneuploidy, but not chromosomal aberrations. In two cell lines, CoCl2 was weakly mutagenic. Interestingly, the poorly soluble compound CoS caused DNA strand breaks and morphological transformation of mammalian cell lines. In contrast to its weak clastogenic and mutagenic properties, cobalt(II) exerts pronounced antimutagenicity in bacteria and mostly comutagenic effects in mammalian cells. In Escherichia coli CoCl2 lowered the frequency of mutations induced by MNNG, uv or X rays. In Chinese hamster V79 cells, CoCl2 enhanced the mutagenicity and clastogenicity of uv light but not of gamma rays. Regarding direct genotoxic mechanisms, Co(II) induces the formation of reactive oxygen species when combined with hydrogen peroxide in cell-free systems. At high (i.e., millimolar) concentrations, Co(II) also decreases the fidelity of DNA synthesis. Regarding anti- and co-mutagenic mechanisms, evidence for the interference of Co(II) with DNA repair processes is discussed. These mechanisms are regarded as relevant for the risk assessment of human exposure to cobalt in combination with other agents.

Cadmium-induced DNA strand damage in cultured liver cells: reduction in cadmium genotoxicity following zinc pretreatment

It is well established that zinc can decrease the carcinogenicity and toxicity of cadmium. In some tissues this may be due to the induction of metallothionein (MT). Therefore, in the present investigation, the effect of zinc pretreatment on cadmium-induced DNA strand damage was determined. The alkaline elution technique was used to assess DNA single strand damage (SSD) in cultured cells derived from rat hepatocytes (TRL-1215), a cell line previously shown to have an active MT gene. The ability to detect SSD in TRL-1215 was established following exposure to gamma-irradiation. Exposure to increasing doses of gamma-irradiation (150-600 rad) resulted in a dose-dependent increase in SSD. Exposure of TRL-1215 cells to CdCl2 for 1 hr at 37 degrees C, using concentrations from 5 to 250 microM, failed to induce detectable SSD in these cells; however, exposure to 500 microM CdCl2 resulted in significant SSD. A time-dependent increase in SSD was demonstrated following a 2 hr continuous exposure to 500 microM CdCl2. Pretreatment of cells with 80 microM zinc acetate, 18 hr prior to exposure to 500 microM CdCl2, resulted in markedly reduced SSD when compared to non-pretreated cells. Zinc pretreatment increased the level of MT gene expression as well as MT protein production. The decrease in DNA strand damage associated with cadmium exposure was not due to a decrease in cadmium accumulation by zinc pretreated cells. In fact, cellular cadmium burden was increased over 2-fold following zinc pretreatment. In addition to protection against cadmium genotoxicity, zinc pretreatment also reduced the cytotoxicity associated with a 2-hr, 500 microM cadmium exposure. These data indicate that zinc pretreatment reduces cadmium genotoxicity, possibly through alterations in MT gene expression.

Toxicological principles of metal carcinogenesis with special emphasis on cadmium

Metals are an important and emerging class of carcinogens. At least three metals, specifically nickel, chromium, and arsenic, are confirmed human carcinogens, and several more are suspected to have carcinogenic potential in man. Considering that the list of known human carcinogens of any type is very small, it becomes clear that metals make up a substantial portion of the list. Furthermore, many metals are very potent carcinogens in laboratory animals. Despite this, relatively little attention has been given to the topic of metal carcinogenesis. The reasons for this relative lack of attention are not clear but perhaps are fostered by a perception that, because metals are the simplest of molecules, their mechanism of action must also be simple. This could not be farther from the truth and, although no clear mechanisms have emerged in the area of metal carcinogenesis, it has become apparent that they are anything but simple. Metal carcinogens possess several unique characteristics including a remarkable target site specificity. Detection of the mechanism, or mechanisms, of metal carcinogenesis has, however, proven elusive, in part because of a wide diversity of metallic carcinogenic agents and the intricate nature of metal interactions in biologic systems. The following review explores this broad topic, with special emphasis on toxicological principles including dose-response relationships and potential mechanisms, using cadmium as an example.

Altered cytokeratin expression and differentiation induction during neoplastic transformation of cultured rat liver cells by nickel subsulfide

Rat liver T51B cells were maintained in the presence of low concentrations of Ni(II) derived from alpha Ni3S2 for 3-15 months in culture in order to monitor cytokeratin, differentiation, and transformation patterns. Nickel exposures caused irreversible, heritable juxtanuclear aggregates of cytokeratin CK55, which increased in size and complexity with prolonged nickel exposure, eventually resembling Mallory bodies and expressing glutamyltransferase. Altered cytokeratin expression was accompanied by induction of differentiation, with markers of both bile ductular cells and hepatocytes, such as induction of cytokeratin polypeptides CK39 and CK49, cell morphology, and cytokeratin filament network changes; whereas control cultures similarly maintained for long periods in culture remained unchanged. Altered cytokeratin expression was also accompanied by acquisition of transformation markers--loss of density dependence, progression toward calcium independence, and (benign) growth in nude mice. Observed cytokeratin aberrations may be a factor in nickel carcinogenesis, in view of the known affinity of the metal for cellular structural proteins, especially keratin, which play a role in maintenance of cell behavior.

In vitro interaction of mutagenic chromium (VI) with red blood cells

The interaction of mutagenic Cr(VI) with red blood cells has been studied by ESR spectroscopy. Signals of two Cr(V) species are observed almost immediately after contacting red cells with chromate(VI) aqueous solution at pH 7.4. The signal at go = 1.985, which decays within one hour, is attributed to a Cr(V) complex formed by glutathione due its reducing and chelating ability. The other signal at go = 1.979, which is distinctly more persistent, may indicate that some immobilization of the formed Cr(V) ions takes place on the macromolecular cell components, e.g. glycoproteins.