The role of transferrins in gallium uptake

Gallium-Based Liquid Metal Materials for Antimicrobial Applications

The hazards caused by drug-resistant bacteria are rocketing along with the indiscriminate use of antibiotics. The development of new non-antibiotic antibacterial drugs is urgent. The excellent biocompatibility and diverse multifunctionalities of liquid metal have stimulated the studies of antibacterial application. Several gallium-based antimicrobial agents have been developed based on the mechanism that gallium (a type of liquid metal) ions disorder the normal metabolism of iron ions. Other emerging strategies, such as physical sterilization by directly using LM microparticles to destroy the biofilm of bacteria or thermal destruction via infrared laser irradiation, are gaining increasing attention. Different from traditional antibacterial agents of gallium compounds, the pronounced property of gallium-based liquid metal materials would bring innovation to the antibacterial field. Here, LM-based antimicrobial mechanisms, including iron metabolism disorder, production of reactive oxygen species, thermal injury, and mechanical destruction, are highlighted. Antimicrobial applications of LM-based materials are summarized and divided into five categories, including liquid metal motors, antibacterial fabrics, magnetic field-responsive microparticles, liquid metal films, and liquid metal polymer composites. In addition, future opportunities and challenges towards the development and application of LM-based antimicrobial materials are presented.

Iron-Sulfur Cluster Biogenesis as a Critical Target in Cancer

Cancer cells preferentially accumulate iron (Fe) relative to non-malignant cells; however, the underlying rationale remains elusive. Iron-sulfur (Fe-S) clusters are critical cofactors that aid in a wide variety of cellular functions (e.g., DNA metabolism and electron transport). In this article, we theorize that a differential need for Fe-S biogenesis in tumor versus non-malignant cells underlies the Fe-dependent cell growth demand of cancer cells to promote cell division and survival by promoting genomic stability via Fe-S containing DNA metabolic enzymes. In this review, we outline the complex Fe-S biogenesis process and its potential upregulation in cancer. We also discuss three therapeutic strategies to target Fe-S biogenesis: (i) redox manipulation, (ii) Fe chelation, and (iii) Fe mimicry.

Yield of Total Body GA-67 Scintigraphy in the Staging of Non-Small Cell Lung Cancer

One hundred and one patients with histologically proved non-small cell lung cancer underwent whole body gallium-67 (TB Ga-67) scintigraphy as a part of their routine pretreatment evaluation. Twenty-eight of these patients were subsequently operated and pathologically staged for hilar and mediastinal disease. Two other patients underwent mediastinoscopy, but were judged unresectable at that time. All had computed tomography (CT) of the thorax, as well as radionuclide or CT scans of suspicious metastatic areas, and were carefully followed-up. When possible, a biopsy was performed of each suspected metastasis. Primary lung tumors concentrated Ga-67 in 94 patients. Sensitivity, specificity, and accuracy for hilar and mediastinal node metastases were 58%, 89%, and 77%, respectively. There were no false-negative gallium scans as regards secondary involvement of both liver and bone, whereas only 1 of the 4 brain metastases was detected by the technique. Sensitivity, specificity, and accuracy for all metastatic sites were 82%, 38%, and 56%, respectively. Fifty-five patients were classified as having a more advanced stage of disease by TB Ga-67 scintigraphy than at the initial clinical evaluation. However, 42 gallium-staged patients were ultimately re-classified differently according to all available clinical data. Using TB Ga-67 scintigraphy, 21 patients were found to have occult metastases which would not otherwise have been recognized; for the above reason, an unnecessary intervention was avoided in 6 of them.

[Basic Study for the Purpose of Developing a Quantitative 67Ga-SPECT Measurement Method]

PURPOSE

⁶⁷Ga-single photon emission computed tomography (SPECT) images vary according to the imaging time and image display methods. The calculation of an index, such as the standardized uptake value used in positron emission tomography, from ⁶⁷Ga-SPECT images would enable the accurate evaluation of the region of accumulation. The purpose of this study was to elucidate the conversion formula, the lower detection limit (LDL), and recovery coefficient (RC) for quantifying the radiation concentration in the ⁶⁷Ga accumulation site.

METHODS

After chronologically obtaining SPECT/CT images at a radiation concentration of 1.0-442.4 kBq/mL with 27 bottles (diameter: 48 mm, 100 mL), the radiation concentration conversion formula was calculated using the successive approximation reconstruction method. The conversion coefficient was then calculated from the relationship between the count rate and the radiation concentration, and the LDL was determined. To compensate for the partial volume effect, the recovery curve was calculated using the mean SPECT count for six bottles (diameter: 9, 18, 29, 38, 48, and 94 mm).

RESULTS

There was a linear relationship between the radiation concentration and the count rate with a good correlation (r=0.99). The LDL was 1.0 kBq/mL. The recovery curve reached a plateau at a diameter of at least 48 mm.

CONCLUSION

The calculation of the absorbed dose index was possible using the radiation concentration conversion formula and the RC.

Aluminum Homeostasis in Man

Aluminum is the most prevalent metal found in nature and represents the third most abundant element of the earth's crust. In light of man's wide exposure to aluminum compounds, a review of the literature was undertaken to determine the extent of the available literature concerning the absorption, distribution, excretion, and metabolism of aluminum in man. In relative terms, the gastrointestinal tract is the major portal of entry for aluminum. The lungs play only a minor role, and there is no evidence to suggest that the dermal absorption of aluminum occurs. The gastrointestinal tract is only very slightly permeable to aluminum and provides a relatively effective barrier to its absorption. In the blood, aluminum is primarily bound to serum proteins (80%); however, a sufficient concentration of dialyziable or “free” (20%) aluminum exists to provide for its distribution. Aluminum can be found in every tissue and a normal body content of aluminum for reference man can now be calculated at 0.295 g. Present data suggest that bone may offer a major site of aluminum deposition. Urine provides at least one mechanism of aluminum excretion. However, aluminum's low renal clearance rate (2 ml/min) clearly suggests that other more efficient mechanisms for excretion exist. In fact, preliminary data indicate that bile may play some as yet undefined role in the removal process. The lack of a biologically convenient radiolabeled form of aluminum has severely handicapped the elucidation of aluminum metabolism. The chemical form of aluminum in blood, urine, or the tissues remains unknown. The liver is believed to play some role in aluminum metabolism, but no direct proof of this is available at present.

Lymphoma: imaging in the evaluation of residual masses

In the management of patients with lymphoma, imaging is essential not only for diagnosis but also to define prognosis and treatment by staging. Imaging is also used to assess the response to treatment that may affect the treatment strategy: new chemotherapeutic drug combinations and autologous stem cell transplantation. These different therapies have increased the need for higher accuracy to assess the response to treatment. Standardised imaging response criteria must be well known by radiologists involved in the management of patients with lymphoma. Criteria are mainly volumetric, and are obtained from CT scans. Functional imaging techniques have been shown to provide better information on the viability of residual masses than does CT assessment of size changes.

CT remains the main imaging technique to assess response to treatment based on volumetric international criteria. New functional imaging tools evaluating perfusion (CT and MRI), and particularly glucose uptake (PET), will probably play an important role in bringing additional information on the metabolism of lymphomatous masses.

Recent advances in the diagnosis and therapy of richter’s syndrome

Richter's syndrome (RS) denotes the development of aggressive lymphoma that arises in patients with chronic lymphocytic leukemia (CLL). Presenting features typically include a rapid clinical deterioration with fever in the absence of infection, progressive lymph node enlargement, and an elevation in serum LDH. Diagnostic biopsy of affected sites usually reveals large cell lymphomas; however, Hodgkin variant cases have been described. Richter's transformation occurs in approx 5% of CLL patients and may be associated with infection with Epstein-Barr virus (EBV). Chromosome 11 and 14 abnormalities have also been described as well as tumor suppressor gene defects involving p53, p21, and p27. Treatment options for these patients are limited and include combination chemotherapy with or without the addition of monoclonal antibodies and stem cell transplantation. Response to therapy is variable and generally short-lived. Median survival is usually in the order of 5-8 mo. More effective management for RS is needed as well as prognostic models that will identify CLL patients at risk of transformation. This review will address the current status of RS and deal with the pathophysiology, diagnostic approach, and treatment of this challenging disease.

Imaging: Staging and evaluation of lymphoma using nuclear medicine

The management of lymphoma is dependent on accurate staging of the disease and evaluation of histology and other risk factors. Advances in imaging techniques have improved the assessment of disease status and evaluation of the efficacy of different treatment modalities. While computed tomography remains the cornerstone of imaging for the assessment of disease status, it provides no understanding of the metabolic or functional parameters of the disease. Nuclear medicine techniques permit the evaluation of functional status, and nuclear medicine is likely to have its greatest impact in the detection of viable tumor in persistent masses. Nuclear imaging can be conducted using single photon agents, such as 67 Ga-citrate with SPECT (single photon emission computed tomography), or with positron emitters, such as 18 F-fluorodeoxyglucose (FDG) with PET (positron emission tomography). Many studies have indicated that FDG-PET is as good as or better than 67 Ga-SPECT for the detection of lymphoma. Thus, FDG-PET may be preferable to 67 Ga-SPECT for disease evaluation, staging, and follow-up. The superiority of FDG-PET compared with other imaging modalities strongly argues that it should be incorporated into the treatment paradigm. At present, FDG-PET scanning is not routinely available in all institutions; however, a role can be indicated for FDG-PET in several areas of lymphoma management, including initial staging, predicting response to therapy (during and following chemotherapy), and identification of residual tumor. This article examines the role of the different imaging techniques available and the use of these techniques in the staging and evaluation of patients with Hodgkin's and non-Hodgkin's lymphoma.

Gallium in cancer treatment

Gallium (Ga) is the second metal ion, after platinum, to be used in cancer treatment. Its activities are numerous and various. It modifies three-dimensional structure of DNA and inhibits its synthesis, modulates protein synthesis, inhibits the activity of a number of enzymes, such as ATPases, DNA polymerases, ribonucleotide reductase and tyrosine-specific protein phosphatase. Ga alters plasma membrane permeability and mitochondrial functions. Ga salts are taken up more efficiently and more specifically by tumour cells when orally administered. New compounds have been prepared: Ga maltolate, doxorubicin-Ga-transferrin conjugate and Tris(8-quinolinolato)Ga(III), which show interesting activities. Ga toxicity is well documented in vitro and in vivo in animals. In humans, the oral administration Ga is less toxic, and allows a chronic treatment, allowing an improvement of its bioavailability in tumours, by comparison with the parenteral use. The anticancer activity of Ga salts has been demonstrated but other effects have also been noted such as many bone effects that could be useful in bone metastatic patients. Its has also been shown that a long period of administration could induce tumour fibrosis. Ga is synergistic with other anticancer drugs. Although not as potent as platinum in vitro, the anticancer activity of Ga should not be ignored, but the schedule of administration still needs to be optimised and new compounds are now under clinical investigations.

Treatment with gallium nitrate: evidence for interference with iron metabolism in vivo

Gallium, when bound to transferrin, has been previously shown to cause tumor cell cytotoxicity by preventing cellular uptake of transferrin bound iron in vitro. Patients treated with constant infusion gallium nitrate for carcinoma show a rise in serum iron within 6 hr of the start of treatment. Serum iron returns to baseline by 24 hr post-infusion. Atomic analysis of iron and gallium content of Sephadex G-150 fractions of treatment sera indicate that about an equimolar amount of gallium and iron are associated with transferrin. These gallium and iron concentrations result in inhibition of transferrin mediated iron uptake in vitro, and in vivo allow for > 90% saturation of transferrin with metal. All seven patients who completed two courses of gallium therapy exhibited hypochromic microcytic anemia (mean fall in hemoglobin 3.5 grams %). Evidence for red cell iron depletion was confirmed by an increase (mean 3.3-fold) in zinc protoporphyrin levels. Since transferrin receptor increases on gallium treated iron requiring cells in vitro, we assessed cell surface transferrin receptor on peripheral blood lymphocytes by measuring fluorescent transferrin receptor antibody binding. A population of highly transferrin receptor positive cells peaks at 48 hr into the infusion. DNA analysis as well as double staining indicate the majority of transferrin receptor positive cells are unstimulated B lymphocytes. These studies provide the first documentation that constant infusion gallium treatment results in significant interference with iron metabolism and evidence for tissue iron depletion in vivo. These changes may correlate with therapeutic effects of gallium such as tumor response.

Transferrin enhances the antiproliferative effect of aluminum on osteoblast-like cells

Aluminum (Al) retention in the body can cause metabolic bone disease. This disorder is characterized by reductions in the number of osteoblasts, a feature that suggests a disturbance in bone cell proliferation or differentiation. Because Al as well as iron (Fe) can bind to transferrin (TF) in plasma, the role of TF as a modifier of osteoblast proliferation was examined in UMR-106-01 osteoblast-like cells by measuring the incorporation of tritiated thymidine ([3H]-TdR) into DNA (counts.min-1.microgram cell protein-1, means +/- SE) during 48-h incubations in serum-free medium (SFM). In the absence of TF, DNA synthesis decreased when media levels of Al exceeded 6-10 microM. The mitogenic response to physiological levels of unsaturated TF (apo-TF) was attenuated however during incubations with TF that was partially saturated with Al (Al-TF). A similar inhibitory response was seen in cells incubated with the antiproliferative agent gallium (Ga) when added to SFM as partially saturated Ga-TF. TF produced a shift to the left in the inhibitory dose-response curve to Al in osteoblast-like cells; thus, DNA synthesis decreased at substantially lower media concentrations of Al in cells grown in SFM containing partially saturated Al-TF. The results indicate that TF is an important determinant of the inhibitory effect of Al on DNA synthesis by osteoblast-like cells at the micromolar levels of Al that can occur in plasma in vivo.

Studies on 67Ga uptake by mouse granuloma tissues

In connection with the uptake of 67Ga into the inflammatory tissues, such as granuloma tissues produced with turpentine oil, the influence of Fe3+ on the uptake of 67Ga into mouse granuloma and normal tissues and on the uptake of 125I-labeled transferrin and 59Fe were investigated. Fe3+ decreased the uptake of 67Ga into the liver and spleen, but had no influence on the uptake of 67Ga into the granuloma tissues. The uptake patterns of 125I-labeled transferrin and 59Fe in the granuloma tissues were not consistent with that of 67Ga at all. These results show that the uptake of 67Ga into the granuloma tissues occurs in a free, transferrin-unbound form, but into the liver and spleen in a transferrin-bound form.

67Ga in transferrin-unbound form is taken up by inflamed liver of mouse treated with CCl4

In order to investigate whether or not transferrin is involved in the uptake of 67Ga by inflamed liver (acute inflammatory tissues) the uptake of 67Ga by the liver of mice treated with carbon tetrachloride (CCl4) was studied. The serum GPT value reached its maximum on the 1st day after the CCl4 treatment. The uptake of 67Ga by the liver also reached its maximum on the 1st day after the CCl4 treatment and the amount uptaken into inflamed liver was about 6 times that uptaken into normal liver. On the other hand, the uptake of 125I-transferrin into inflamed liver on the 1st day after CCl4 treatment was only about 1.6 times that into normal liver. Moreover, cold Fe3+ decreased the uptake of 67Ga by normal liver but increased the uptake of 67Ga by inflamed liver. These results show that transferrin plays an important role in the uptake of 67Ga by normal liver but not by inflamed liver, i.e. 67Ga in the transferrin-unbound form is preferentially taken up by inflamed liver.

Effects of iron-binding proteins on in vitro uptake of 67Ga-citrate by tumor cells

A comparative study of carrier-free 67Ga-citrate uptake by Ehrlich ascites tumor cells in the presence of lactoferrin, transferrin and ferritin has demonstrated that lactoferrin considerably increases the uptake of 67Ga, and that this increase seems to be determined by its iron-load. The other iron-binding proteins assayed have a null or negative effect. Their behavior in the presence of sodium citrate supports the concept of lactoferrin-binding by the cells as responsible for the uptake. The different behavior of 67Ga-citrate iron-binding protein complexes appears to support this hypothesis.

Involvement of transferrin in the uptake of 67Ga in inflammatory and normal tissues

The results from gel chromatography and electrophoresis showed that 67Ga is exclusively bound with transferrin both in vitro and in vivo, but high concentrations of sodium citrate strongly inhibited the binding of 67Ga to transferrin. The influence of sodium citrate on the uptake of 67Ga into inflammatory and normal soft tissues was also investigated. Sodium citrate decreased the uptake of 67Ga into the liver and spleen, but had no influence on the uptake of 67Ga into inflammatory tissue. These results suggest that the uptake of 67Ga into normal soft tissues occurs in a transferrin-bound form but into inflammatory tissue in an unbound form.

The effect of FeCl3 on the accumulation of gallium-67 into inflammatory and normal tissues

The effect of FeCl3 on the uptake of 67Ga by inflammatory and normal tissues was studied to clarify the role of transferrin in 67Ga uptake by inflammatory tissue. The administration of FeCl3 5 min before the injection of 67Ga decreased the uptake of 67Ga by liver and spleen, but had little effect on the uptake of 67Ga by the inflammatory tissue. These results suggest that 67Ga is taken up by normal tissues in a transferrin-bound form but in an unbound form by inflammatory tissue. On the other hand, when FeCl3 was simultaneously injected with 67Ga, the uptake of 67Ga by liver and spleen was markedly increased but the uptake by inflammatory tissue was decreased.

Gallium-transferrin as a macromolecular tracer of vascular permeability

Labeling of plasma transferrin with gallium was investigated to determine whether the gallium-transferrin complex could be effectively used as a macromolecular tracer in studies of capillary permeability using Positron Emission Tomography (PET). Three gallium-plasma preparations were tested and 2 h biodistribution studies were performed in rats. The three preparations gave similar blood clearance and tissue distribution data, but the methods used for evaluating gallium-transferrin binding were found to be suboptimal. Gallium clearance from blood was biexpoential with both components faster than that of 125I-albumin. Gallium distribution spaces in all tissues including intracerebral Walker-256 tumors were larger than those of albumin. These results indicate a relative instability of the gallium-transferrin complex in vivo, which appears to preclude its use as an acceptable radiolabeled protein for vascular permeability studies using PET.

Pulmonary gallium uptake in rats with granulomatosis induced by complete Freund adjuvant

To investigate the mechanism of gallium-67 uptake in lung granulomatosis, we studied 13 rats in which lung granulomatosis was induced by injection of complete Freund adjuvant (CFA) and 14 controls. Gallium uptake was assessed in bronchoalveolar lavage fluid and lavaged lung. The cells responsible for gallium uptake were identified by latent image activation autoradiography. Gallium activity in both lavaged lungs and bronchoalveolar cells (BAC) was higher in CFA-treated animals than in controls [172,205 +/- 134,783 DPM versus 44,456 +/- 14,486 DPM +/- SD (p less than 0.05) and 40,083 +/- 16,350 DPM versus 9100 +/- 4114 DPM (p less than 0.05), respectively]. In control rats, about two-thirds of total lung gallium was located in the interstitium, whereas in CFA-treated rats it was found in the mononuclear cells of lung granulomas. Gallium tracks were more numerous in the alveolar macrophages (AM) of CFA-treated rats than in control AM (28.4 +/- 10.0/field versus 8.4 +/- 3.8/field, p less than 0.001) but the number of tracks was proportional to the number of AM (52.4 +/- 18.7 versus 12.2 +/- 4.3, respectively; p less than 0.001). It is concluded that in rats with CFA-induced lung granulomatosis 1) pulmonary gallium uptake increases, 2) mononuclear cells are responsible for this uptake in both granulomas and AM, and 3) the increased uptake is due to the increased number of mononuclear cells.

Effects of different transferrin forms on transferrin receptor expression, iron uptake, and cellular proliferation of human leukemic HL60 cells. Mechanisms responsible for the specific cytotoxicity of transferrin-gallium

We have previously shown that human leukemic cells proliferate normally in serum-free media containing various transferrin forms, but the addition of transferrin-gallium leads to inhibition of cellular proliferation. Because gallium has therapeutic potential, the effects of transferrin-gallium on leukemic cell proliferation, transferrin receptor expression, and cellular iron utilization were studied. The cytotoxicity of gallium is considerably enhanced by its binding to transferrin and cytotoxicity can be reversed by transferrin-iron but not by other transferrin forms. Exposure to transferrin-gallium leads to a marked increase in cell surface transferrin binding sites, but despite this, cellular 59Fe incorporation is inappropriately low. Although shunting of transferrin-gallium to another cellular compartment has not been ruled out, other studies suggest that transferrin-gallium impairs intracellular release of 59Fe from transferrin by interfering with processes responsible for intracellular acidification. These studies, taken together, demonstrate that inhibition of cellular iron incorporation by transferrin-gallium is a prerequisite for inhibition of cellular proliferation.

Systemic and lung protein changes in sarcoidosis. Lymphocyte counts, gallium uptake values, and serum angiotensin-converting enzyme levels may reflect different aspects of disease activity

BAL lymphocyte percentages, quantitated gallium-67 lung uptake, and SACE levels have all been proposed as measures of disease activity in sarcoidosis. We analyzed 32 paired sera and BAL fluids from sarcoidosis patients by high-resolution agarose electrophoresis to look for protein changes characteristic of systemic or local inflammation and compared the results with those from the above tests. Nine patients (group 1) had serum inflammatory protein changes and increased total protein, albumin, beta 1-globulin (transferrin), and gamma-globulin levels in fluid recovered by BAL. Thirteen patients (group 2) had normal protein levels in sera but abnormal protein levels in BAL specimens. Ten patients (group 3) had normal protein levels in sera and in BAL specimens. Patients in groups 1 and 2 had a disproportionate increase in beta 1-globulin (transferrin) and gamma-globulin levels in their BAL specimens. The BAL lymphocyte percentage changes paralleled the BAL protein level changes, suggesting relationships among the immunoregulatory role of these cells, increased local immunoglobulin synthesis, and the pathogenesis of altered alveolar permeability. Gallium-67 uptake was highest in patients with serum inflammatory protein changes. Thus, systemic inflammation may facilitate pulmonary gallium-67 uptake, possibly by changes in BAL fluid or serum transferrin saturation and/or kinetics. SACE levels showed no relationship to changes in the levels of serum or BAL proteins. These data suggest that the various proposed measures of disease activity reflect different aspects of inflammation in sarcoidosis.

The influence of isotopic and nonisotopic carriers on the biodistribution and biokinetics of M3+-citrate complexes

The influence of carrier amounts of Fe, Ga, and Tm on the biodistribution of 67Ga-, 59Fe-, and 167Tm-citrate in mice was investigated. Our results suggest that 167Tm, unlike 67Ga and 59Fe, is not transported by transferrin in the blood. Of the three radioisotopes tested, 167Tm had the highest tumor/background ratio (10 h after the injection). The application of Fe carrier led to an enhancement of the elimination of 67Ga from the blood and muscles, resulting in a better tumor/background ratio.

[Effect of pH and the binding anion on In3+-transferrin interaction: spectroscopic study of the perturbed angular correlation of 172-245 keV gamma rays of indium 111]

The formation of ternary complexes, transferrin-anion-In111 has been investigated by means of gamma-gamma coincidence spectrometry of the 172-245 keV rays. The angular correlation between the two gamma-rays emitted in cascade depends on the magnetic and electric fields gradients, consequently the chemical structure of metal holder. Any modification of this structure causes the variation of angular correlation. The study of G22 (infinity) as function of pH (G22(infinity): integrated perturbed angular correlation coefficient) has been performed to turn out the hydrolysis of In111 in aqueous solution, metal complex formation in presence of chelating agents (citric acid and sodium bicarbonate) and the formation of protein-metal complexes. The presence of complexing agents limits the domain of In111 colloid existence and allows fast transfer of ionised indium on the transferrin. Two types of metal-protein interactions has been turn out. The first in the weakly acidic range of pH is characterized by an affinity constant near to this of citric acid. The second lying in neutral and basic range of pH, where the formation rate of transferrin-In111 complex is fast (t less than 500 s). In citrate medium, for pH 6-7,5 the rate of metal transfer on the protein, studied by means of G22 (infinity) = f(t), is function of pH. The binding anion appears as an indispensable element for the formation of protein-metal complexes. The In111 previously chelated by 8-Hydroxyquinoline is fixed by the protein if only exits a binding anion in the solution. This mays bring in the formation of an intermediate active state, indispensable step for the ternary complex formation transferrin-anion-In111.