LINE-1 global DNA methylation, iron homeostasis genes, sex and age in sudden sensorineural hearing loss (SSNHL)

BACKGROUND

Sudden sensorineural hearing loss (SSNHL) is an abrupt loss of hearing, still idiopathic in most of cases. Several mechanisms have been proposed including genetic and epigenetic interrelationships also considering iron homeostasis genes, ferroptosis and cellular stressors such as iron excess and dysfunctional mitochondrial superoxide dismutase activity.

RESULTS

We investigated 206 SSNHL patients and 420 healthy controls for the following genetic variants in the iron pathway: SLC40A1 - 8CG (ferroportin; FPN1), HAMP - 582AG (hepcidin; HEPC), HFE C282Y and H63D (homeostatic iron regulator), TF P570S (transferrin) and SOD2 A16V in the mitochondrial superoxide dismutase-2 gene. Among patients, SLC40A1 - 8GG homozygotes were overrepresented (8.25% vs 2.62%; P = 0.0015) as well SOD2 16VV genotype (32.0% vs 24.3%; P = 0.037) accounting for increased SSNHL risk (OR = 3.34; 1.54-7.29 and OR = 1.47; 1.02-2.12, respectively). Moreover, LINE-1 methylation was inversely related (r2 = 0.042; P = 0.001) with hearing loss score assessed as pure tone average (PTA, dB HL), and the trend was maintained after SLC40A1 - 8CG and HAMP - 582AG genotype stratification (ΔSLC40A1 = + 8.99 dB HL and ΔHAMP = - 6.07 dB HL). In multivariate investigations, principal component analysis (PCA) yielded PC1 (PTA, age, LINE-1, HAMP, SLC40A1) and PC2 (sex, HFEC282Y, SOD2, HAMP) among the five generated PCs, and logistic regression analysis ascribed to PC1 an inverse association with moderate/severe/profound HL (OR = 0.60; 0.42-0.86; P = 0.0006) and with severe/profound HL (OR = 0.52; 0.35-0.76; P = 0.001).

CONCLUSION

Recognizing genetic and epigenetic biomarkers and their mutual interactions in SSNHL is of great value and can help pharmacy science to design by pharmacogenomic data classical or advanced molecules, such as epidrugs, to target new pathways for a better prognosis and treatment of SSNHL.

Adenoviral Vector for Enhanced Prostate Cancer Specific Transferrin Conjugated Drug Targeted Therapy

Prostate cancer (PCa) is one of the leading causes of death for men worldwide. Unlike some other types of cancer, there is a lack of targeted therapy for prostate cancer patients that can kill cancer cells but do much less damage to the normal tissue. In this paper, we report on an adenoviral vector enhanced prostate cancer specific transferrin conjugated drug targeted therapy. In particular, a functional PCa-specific gene probe is introduced to drive and up-regulate the transferrin receptor expression on the PCa via adenoviral vector. As a result, significantly enhanced accumulation of nanoscale transferrin-doxorubicin (Tf-DOX) protein drug conjugates and concomitant notably elevated PCa tumor inhibition are observed. This conceptual strategy provides the proof-of-concept for the targeted therapy of PCa that is highly desired but not yet developed.

Active targeting of orthotopic glioma using biomimetic liposomes co-loaded elemene and cabazitaxel modified by transferritin

BACKGROUND

Effective treatment of glioma requires a nanocarrier that can cross the blood-brain barrier (BBB) to target the tumor lesion. In the current study, elemene (ELE) and cabazitaxel (CTX) liposomes were prepared by conjugating liposomes with transferrin (Tf) and embedding the cell membrane proteins of RG2 glioma cells into liposomes (active-targeting biomimetic liposomes, Tf-ELE/CTX@BLIP), which exhibited effective BBB infiltration to target glioma.

RESULTS

The findings showed that Tf-ELE/CTX@BLIP was highly stable. The liposomes exhibited highly significant homologous targeting and immune evasion in vitro and a 5.83-fold intake rate compared with classical liposome (ELE/CTX@LIP). Bioluminescence imaging showed increased drug accumulation in the brain and increased tumor penetration of Tf-ELE/CTX@BLIP in orthotopic glioma model nude mice. Findings from in vivo studies indicated that the antitumor effect of the Tf-ELE/CTX@BLIP led to increased survival time and decreased tumor volume in mice. The average tumor fluorescence intensity after intravenous administration of Tf-ELE/CTX@BLIP was 65.2, 12.5, 22.1, 6.6, 2.6, 1.5 times less compared with that of the control, CTX solution, ELE solution, ELE/CTX@LIP, ELE/CTX@BLIP, Tf-ELE/CTX@LIP groups, respectively. Histopathological analysis showed that Tf-ELE/CTX@BLIP were less toxic compared with administration of the CTX solution.

CONCLUSION

These findings indicate that the active-targeting biomimetic liposome, Tf-ELE/CTX@BLIP, is a promising nanoplatform for delivery of drugs to gliomas.

Entropy-Driven Quick Loading of Functional Proteins in Nanohydrogels for Highly Efficient Tumor Targeting Therapy

With the gradual deep understanding of the tumorigenesis and development process, nanodrug are thought to have great prospects for individualized treatment of tumors. To deliver adequate concentration of active ingredients to targeted tissues, proteins are usually used as carriers to avoid clearance by the immune system. Herein, a new strategy is developed for preparation of the protein-functionalized targeting nanodrugs; different kinds of proteins (albumin, horseradish, transferrin, and ricin) can be quickly loaded in polyacrylic acid nanohydrogels (PAA-NGs) without discrimination within 1 min under the strong driving force of entropy; and the loading efficiency can reach 99% with about 50% loading content. Meanwhile, the activity of the released protein can be well retained. After oriented binding of the targeting agent on the surface of the nanocarriers by a unique and facile technique, the protein-loaded nanodrug exhibits excellent tumor cell uptake and targeting effect. The excellent targeting ability from the oriented binding is further proved by comparing with the non-oriented targeting system. With quick loading of the anti-tumor protein of ricin and oriented binding of transferrin protein (Tf), the targeting nanodrug (PAA-BB@Ricin/Tf) shows a remarkable anti-tumor effect. This study proves a new universal delivery and targeting strategy for improving the nanodelivery system, which has great potentials for clinical application.

From Rust to Quantum Biology: The Role of Iron in Retina Physiopathology

Iron is essential for cell survival and function. It is a transition metal, that could change its oxidation state from Fe²⁺ to Fe³⁺ involving an electron transfer, the key of vital functions but also organ dysfunctions. The goal of this review is to illustrate the primordial role of iron and local iron homeostasis in retinal physiology and vision, as well as the pathological consequences of iron excess in animal models of retinal degeneration and in human retinal diseases. We summarize evidence of the potential therapeutic effect of iron chelation in retinal diseases and especially the interest of transferrin, a ubiquitous endogenous iron-binding protein, having the ability to treat or delay degenerative retinal diseases.

[Non-transferrin-bound iron: a promising biomarker in iron overload disorders]

Iron overload disorders are common and, if left untreated, severe systemic diseases that can have both genetic and acquired causes. Hereditary haemochromatosis, β-thalassaemia, myelodysplastic syndromes and sickle cell disease are among the most important examples. Iron that is not bound to transferrin, haem or ferritin (non-transferrin-bound iron, NTBI) seems to play a key role in the pathophysiology of these disorders. NTBI is a heterogeneous group of potentially toxic iron complexes in plasma which are generated almost exclusively under pathological conditions. Cellular uptake of NTBI contributes to its toxicity and is mediated by several organ-specific transporters and receptors. NTBI-induced toxicity is the result of oxidative damage to various macromolecules by reactive oxygen species (ROS). In the near future, we hypothesize that NTBI will have important implications for both diagnosis and treatment of iron overload disorders. However, before NTBI can be applied to patient care, the currently available assays need further clinical and analytical validation.

Iron overload, hematopoietic cell transplantation, and graft-versus-host disease

Many patients who undergo hematopoietic cell transplantation (HCT) present with anemia and have received red blood cell transfusions before HCT. As a result, iron overload is frequent and appears to be particularly prominent in patients with myelodysplastic syndromes. There is evidence that peritransplant events contribute to further iron accumulation, although the mechanism that disrupts normal iron homeostasis remains to be determined. Recent studies suggest that iron overload, as determined by ferritin levels, a surrogate marker for iron, is a risk factor for increased non-relapse mortality after HCT. Iron overload is associated with an increased rate of infections, in particular with fungal organisms. Furthermore anecdotal data suggest that increased hepatic iron may mimic the clinical picture of (chronic) graft-versus-host-disease (GVHD). Whether excess iron contributes to GVHD and whether iron depletion, be it by phlebotomy or chelation, reduces the post-transplantation complication rate and improves transplant outcome is yet to be determined.

Fusion-proteins as biopharmaceuticals--applications and challenges

As the genetic combination of originally separate proteins, fusion proteins are successful biopharmaceuticals. This review summarizes the fusion proteins that are approved for use in the clinic and those that are currently in clinical trials. Fusion proteins can be categorized into several groups according to their features. In the first group, effector molecules are fused to Fc domains, albumin or transferrin to extend the plasma half-life of the fusion product. In the second group, toxicity is conveyed by fusion proteins to toxins, enzymes or cytokines. The third application, which is not yet in clinical trials, utilizes fusion partners to enable novel delivery and targeting routes. Besides some specific disadvantages, many examples of fusion proteins suffer from the challenge of immunogenicity; however, future applications with novel fusion partners will reach beyond cancer, immunology and inflammation.

Improving Therapeutic Properties of Protein Drugs through Alteration of Intracellular Trafficking Pathways

Although intracellular trafficking processes can play a central role in the physiological function of a protein, these same processes can also limit the benefit of the protein when it is taken out of its physiological context and used as a protein drug. Therefore, the properties of certain protein drugs may be improved by manipulating their trafficking pathways to suit their therapeutic function. A detailed consideration of the factors that govern how protein traffic is routed among different cellular destinations can be used to ascertain molecular design criteria for engineering a protein drug so as to alter its trafficking pathway in a beneficial manner. In this review, we summarize studies that have applied this approach to achieve the following three improvements in protein drug function: (1) half-life extension of the Fc fragment of IgG, (2) half-life extension of granulocyte colony-stimulating factor, and (3) increase in cellular association of transferrin.

Effective anti-tumor activity of oxaliplatin encapsulated in transferrin-PEG-liposome

Oxaliplatin (trans-L-diaminocyclohexane oxalatoplatinum, L-OHP) is a novel cisplatin derivative that can improve the side effects of cisplatin such as toxicity to the kidneys and peripheral nerve system. However, L-OHP is effective only when combined with 5-Fluorouracil (5-FU) and Leucovorin. The relatively low anti-tumor index of L-OHP alone is because low levels accumulate in tumor tissues due to high partitioning to erythrocytes in vivo. A successful outcome of cancer therapy using L-OHP requires the selective delivery of a relatively high concentration of the drug to tumors. The present study examines tumor-selective delivery of L-OHP using liposomes modified with transferrin-conjugated polyethyleneglycol (TF-PEG-liposomes). Delivery using these liposomes significantly reduced L-OHP partitioning to erythrocytes and improved the circulation time of L-OHP in vivo, resulting in enhanced extravasation of liposomes into tumors. The TF-PEG-liposomes maintained a high L-OHP concentration in tumors for over 72 h after intravenous injection, which was longer than that of the liposomes modified with PEG (PEG-liposomes). Intravenously administered L-OHP encapsulated within TF-PEG-liposomes (L-OHP: 5 mg/kg) suppressed tumor growth more effectively than PEG-liposomes, Bare-liposomes and free L-OHP. Although L-OHP is usually combined with 5-FU and Leucovorin, our results suggest that L-OHP encapsulated within TF-PEG-liposomes has potential for cancer therapy.

Therapeutic potential of iron chelators in diseases associated with iron mismanagement

A considerable array of diseases are now recognized to be associated with misplacement of iron. Excessive deposits of the metal in sensitive tissue sites can result in formation of destructive hydroxyl radicals as well as in stimulation of growth of neoplastic and microbial cell invaders. To counteract potential iron damage, hosts employ the iron chelators, transferrin and lactoferrin. These proteins have been recently developed into pharmaceutical products. Additionally, a variety of low molecular mass iron chelators are being used/tested to treat whole body iron loading, and specific diseases for which the metal is a known or suspected risk factor.

Effect of repeated apotransferrin administrations on serum iron parameters in patients undergoing myeloablative conditioning and allogeneic stem cell transplantation

Myeloablative conditioning prior to allogeneic stem cell transplantation causes a rapid increase in transferrin saturation and potentially toxic non-transferrin-bound iron (NTBI) in plasma. We have studied the ability of repeatedly administered apotransferrin to maintain this iron in a transferrin-bound form. Twenty adult patients undergoing myeloablative conditioning and allogeneic stem cell transplantation were enrolled to receive apotransferrin with one of three dosage regimens. Ten consecutive patients with the same preconditioning were studied as controls. At the highest dose level, full transferrin saturation and appearance of NTBI were prevented in five of the eight patients. Serum iron increased significantly more in the patients receiving apotransferrin than in the controls and remained elevated until erythropoietic recovery. From the increment of iron saturation and the amount of endogenous and administered apotransferrin, an average 180 mumol of iron per day was bound to transferrin during the first 4 d after the start of the conditioning therapy. Thereafter, iron accumulation levelled off in most patients. The results suggested that about half of the amount of iron normally transported to erythropoiesis was initially released to plasma after induction of the erythroid arrest. Complete iron binding with apotransferrin would apparently require very high apotransferrin doses.

Clinical studies with targeted toxins in malignant glioma

Targeted toxins represent a new class of agents with high specificity for tumor cells. Toxins in current clinical use for the treatment of brain tumors are mostly recombinant polypeptides consisting of a tumor-selective ligand coupled to a peptide toxin of bacterial origin. Targeted toxins are highly potent - one single molecule of toxin is enough to cause cell death. Toxins are able to kill tumor cells independent of any malignancy-associated genetic alterations and/or mutations. The blood-brain barrier has been a major obstacle for using targeted toxins for treatment of malignant glioma. Convection-enhanced delivery (CED), a method for delivery of large molecules to brain tissue via continuous interstitial microinfusion, has permitted direct administration of toxins to brain tumors or to surrounding brain tissue infiltrated by tumor cells. Four targeted toxins advanced to at least phase II clinical trials and are being used for treatment of adult or pediatric patients with recurrent or progressive malignant glioma. These are IL4-P. aeruginosa exotoxin (IL4-PE, NBI-3001), tumor growth factor (TGF)alpha-P. aeruginosa exotoxin (TP-38), IL13-P. aeruginosa exotoxin (IL13-PE38), and transferrin-C. diphtheriae toxin (TransMID(trade mark), Tf-CRM107). All of these toxins have shown an acceptable profile of toxicity and safety in phase I and II clinical studies and have demonstrated some evidence for tumor response. Current phase I and II clinical protocols are exploring several parameters, such as placement of catheters for CED either intratumorally or in the brain tissue surrounding a tumor, surgical resection of tumor before or after toxin infusion, and single vs. repeated infusion. Two large randomized and controlled phase III multicenter studies using IL13-PE38 or TransMID(trade mark) are currently enrolling patients. This review summarizes the study protocols and key findings of all previously completed and currently ongoing clinical studies with targeted toxins for malignant glioma. It offers in addition an outlook into future areas of development of targeted toxins, such as improved delivery modes and non-invasive in vivo imaging of intracerebral and intratumoral distribution of toxin in patients.

Remyelination after cuprizone-induced demyelination in the rat is stimulated by apotransferrin

Twenty-one-day-old Wistar rats were fed a diet containing 0.6% cuprizone for 2 weeks. Studies carried out after withdrawal of cuprizone showed histological evidences of marked demyelination in the corpus callosum. Biochemical studies of isolated myelin showed a marked decrease in myelin proteins, phospholipids, and galactocerebrosides as well as a marked decrease in myelin yield. Treatment of these animals with a single intracranial injection of 350 ng of apotransferrin at the time of withdrawal of cuprizone induced a marked increase in myelin deposition resulting in a significantly improved remyelination, evaluated by histological, immunocytochemical, and biochemical parameters, in comparison to what was observed in spontaneous recovery. Immunocytochemical studies of cryotome sections to analyze developmental parameters of the oligodendroglial cell population at the time of termination of cuprizone and at different times thereafter showed that in the untreated animals, there was a marked increase in the number of NG2-BrdU-positive precursor cells together with a marked decrease in MBP expression at the peak of cuprizone-induced demyelination. As expected, the amount of precursor cells decreased markedly during spontaneous remyelination and was accompanied by an increase in MBP reactivity. In the apotransferrin-treated animals, these phenomena occurred much faster, and remyelination was much more efficient than in the untreated controls. The results of this study suggest that apotransferrin is a very active promyelinating agent which could be important for the treatment of certain demyelinating conditions.

The anti-malaria drug artesunate inhibits replication of cytomegalovirus in vitro and in vivo

Treatment of human cytomegalovirus (HCMV) infections with any of the currently available antiviral agents is frequently associated with the occurrence of severe complications, seriously threatening the successful outcome of treatment. Therefore, the development of novel antiviral strategies is a challenging goal of current investigations. Previously, we reported that artesunate (ART) is an effective, non-cytotoxic inhibitor of HCMV in vitro. Here, we demonstrate that the efficacy of the antiviral effect of ART is augmented by co-treatment of HCMV-infected fibroblasts with ferrous iron, i.e. Ferrosanol, and/or the iron transfer-mediating molecule holo-transferrin. This could alleviate the HCMV-induced modulation of cell surface expression of adhesion molecule Thy-1, suggesting that ART might be able to prevent pro-inflammatory effects of infection. The iron-enhanced, antiviral effect of ART could also be demonstrated in cultured cells infected with rat cytomegalovirus. Experiments using the RCMV/rat model showed that both the viral DNA load and virus titers in the salivary glands from infected rats were significantly reduced upon treatment with ART. Furthermore, an additive antiviral effect for ART together with each one of conventional anti-HCMV drugs, i.e. ganciclovir, cidofovir or foscarnet, was detected in HCMV-infected fibroblasts. These findings might open new perspectives regarding the use of ART in clinical trials.

Transferrin: structure, function and potential therapeutic actions

There are many proteins that can multi-task. Transferrin, widely known as an iron-binding protein, is one such example of a multi-tasking protein. In this review, the multiple biological actions of transferrin, including its growth and cytoprotective activities, are discussed with the view of highlighting the potential therapeutic applications of this protein.

Targeted molecular therapy for malignant gliomas

Advances in our understanding of the molecular changes and resultant cellular effects in malignant glioma are expanding the opportunities for novel targeted therapies. At present, chemotherapy and radiation followed by chemotherapy with nonselective cytotoxic agents is emerging as a standard treatment option for patients with malignant glioma. Unfortunately significant improvements in response and survival have not occurred for the majority of patients. The continued improvement in patient outcomes will require the incorporation of glioma-specific therapies either in the form of compounds specifically targeted to glioma-specific receptors or that inhibit signaling pathways promoting glioma survival and progression.

Intratumoral immunotoxin treatment of human malignant brain tumors in immunodeficient animals

Treatment of malignant brain tumors remains a clinical challenge. New treatment modalities are under investigation and among these are intratumoral infusion of immunotoxins that bind to specific cell surface molecules on the malignant cells. We have compared the efficacy of the 425.3-PE immunotoxin (which targets the epidermal growth factor [EGF] receptor) with the well-known immunotoxin Tfn-CRM107 (which targets the transferrin receptor), for the treatment of subcutaneous and intracranial human gliomas in nude animals. Bolus intratumoral administration of 1 microg Tfn-CRM107 or 425.3-PE into sc U87Mg tumors in nude mice reduced the tumor volume to 29 and 79%, respectively, of that in the control group 18 days after start of treatment. Higher doses of Tfn-CRM107 were toxic to the animals, whereas 425.3-PE was tolerated, with a dose-response relationship of up to 8 microg, a dose that reduced the tumor volume to 2% of control. In nude rats, treatment of intracerebral U87Mg tumors with Tfn-CRM107 proved ineffective and doses above 10 ng/animal were toxic to tumor-bearing rats. In contrast, intratumoral administration of 4 microg 425.3-PE increased symptom-free survival from 23 days to 40 days, with 2/9 surviving more than 90 days. We have recently shown that immunodeficient rats inoculated intracerebrally with precultured glioblastoma biopsy specimens develop highly infiltrative brain tumors. Direct interstitial infusion of immunotoxins into such tumors reduced the number of animals with detectable tumors at autopsy after 3 months, from 8/9 in the control animals to 4/6 and 2/6 in animals treated with Tfn-CRM107 and 425.3-PE, respectively. In conclusion, the anti-EGF receptor immunotoxin 425.3-PE exhibited promising efficacy, comparable to or better than that of Tfn-CRM107, an immunotoxin that in early clinical trials has been found to give responses in patients with brain tumors.

In vitro and in vivo efficacy of acid-sensitive transferrin and albumin doxorubicin conjugates in a human xenograft panel and in the MDA-MB-435 mamma carcinoma model

Acid-sensitive transferrin and albumin conjugates with doxorubicin have recently been developed with the aim of circumventing the systemic toxicity and improving the therapeutic efficacy of this anticancer agent. The in vitro activity of two acid-sensitive transferrin and albumin doxorubicin conjugates and free doxorubicin was evaluated in twelve human tumour xenografts using a clonogenic assay. The inhibitory effects and the activity profile of the conjugates was, in general, comparable to that of doxorubicin (mean IC(70) -value for doxorubicin approximately 0.1 microM and 0.1 - 0.4 microM for the conjugates). Subsequently, the efficacy of an acid-sensitive transferrin and albumin doxorubicin conjugate, which both incorporated a phenylacetyl hydrazone bond as a predetermined breaking point, was evaluated in the xenograft mamma carcinoma model MDA-MB-435 in comparison to free doxorubicin (dose, i.v.: 2 x 4, 8 and 12 mg/kg). The conjugates showed significantly reduced toxicity (reduced lethality and body weight loss) with a concomitantly stable or slightly improved antitumour activity compared to free doxorubicin. At the dose of 12 mg/kg mortality was unacceptably high in the doxorubicin treated group ( approximately 80%); in contrast, no mortality was observed with the conjugate treated animals with body weight loss < 10 %. In a further experiment, therapy with the acid-sensitive doxorubicin albumin conjugate at 3 x 12 mg/kg in the MDA-MB-435 model resulted in a significantly improved antitumour activity over free doxorubicin at its optimal dose of 2 x 8 mg/kg. In conclusion, acid-sensitive transferrin and albumin doxorubicin conjugates can be administered at higher doses than free doxorubicin in nude mice models with a concomitant improvement in antitumour activity. Interestingly, there is no pronounced difference between identically constructed transferrin and albumin doxorubicin conjugates with regard to in vitro or in vivo efficacy.

Development of a pharmaceutical apotransferrin product for iron binding therapy

High-dose chemotherapy of patients with haematological malignancies results in extracellular iron accumulation and appearance of non-transferrin-bound iron, which is thought to predispose the patients to septic infections and contribute to organ toxicity. We describe the development of a human plasma-derived apotransferrin product for iron binding therapy. The product is purified from Cohn fraction IV of human plasma by two ion exchange chromatography steps and ultrafiltration. The process comprises solvent detergent treatment as the main virus inactivation step and 15 nm virus filtration and polyethylene glycol precipitation as removal steps for physico-chemically resistant infectious agents. Product characterization by electrospray and MALDI-TOF mass spectrometry indicated no other chemical modifications than N-linked glycan chains and disulphide bonds, except minor oxidation. The purity of the product was more than 98%, main impurities being IgG, IgA and hemopexin. The product had intact iron binding capacity and native conformation. A stable liquid formulation for the finished product was developed. The product has proved safe and well tolerated in early clinical trials in iron binding therapy.

Vascular protection by chloroquine during brain tumor therapy with Tf-CRM107

Tf-CRM107 is a conjugate of transferrin and a point mutant of diphtheria toxin that selectively kills cells expressing high levels of the transferrin receptor. Tf-CRM107 has been infused intratumorally into patients with malignant brain tumors. Although approximately half of the patients exhibit tumor responses, patients receiving higher doses of Tf-CRM107 may develop magnetic resonance image (MRI) evidence of toxicity indicative of small vessel thrombosis or petechial hemorrhage. Consistent with these clinical results we found that intracerebral injection of Tf-CRM107 into rats at total doses > or =0.025 microg causes brain damage detectable by MRI and histology. To widen the therapeutic window of Tf-CRM107, we explored ways to prevent this damage to the vasculature. We reasoned that the vasculature may be protected to a greater extent than tumor from Tf-CRM107 infused into brain parenchyma by i.v. injection of reagents with low blood-brain barrier permeability that block the toxicity of Tf-CRM107. Chloroquine, a well-characterized antimalarial drug, blocks the toxicity of diphtheria toxin and Tf-CRM107. Systemic administration of chloroquine blocked the toxicity of Tf-CRM107 infused intracerebrally in rats and changed the maximum tolerated dose of Tf-CRM107 from 0.2 to 0.3 microg. Moreover, chloroquine treatment completely blocked the brain damage detected by MRI caused by intracerebral infusion of 0.05 microg of Tf-CRM107. In nude mice bearing s.c. U251 gliomas, chloroquine treatment had little effect on the antitumor efficacy of Tf-CRM107. Thus, chloroquine treatment may be useful to reduce the toxicity of Tf-CRM107 for normal brain without inhibiting antitumor efficacy and increase the therapeutic window of Tf-CRM107 for brain tumor therapy.

Engineering receptor-mediated cytotoxicity into human ribonucleases by steric blockade of inhibitor interaction

Several nonmammalian members of the RNase A superfamily exhibit anticancer activity that appears to correlate with resistance to the cytosolic ribonuclease inhibitor (RI). We mutated two human ribonucleases-pancreatic RNase (hRNAse) and eosinophil-derived neurotoxin (EDN)-to incorporate cysteine residues at putative sites of close contact to RI, but distant from the catalytic sites. Coupling of Cys89 of RNase and Cys87 of EDN to proteins at these sites via a thioether bond produced enzymatically active conjugates that were resistant to RI. To elicit cellular targeting as well as to block RI binding, transferrin was conjugated to a mutant human RNase, rhRNase(Gly89)-->Cys) and a mutant EDN (Thr87-->Cys). The transferrin-rhRNase(Gly89-->Cys) thioether conjugate was 5000-fold more toxic to U251 cells than recombinant wild-type hRNase. In addition, transferrin-targeted EDN exhibited tumor cell toxicities similar to those of hRNase. Thus, we endowed two human RI-sensitive RNases with greater cytotoxicity by increasing their resistance to RI. This strategy has the potential to generate a novel set of recombinant human proteins useful for targeted therapy of cancer.

Mechanism of action and spectrum of cell lines sensitive to a doxorubicin-transferrin conjugate

A transferrin-doxorubicin conjugate exhibited greatly increased cytotoxicity relative to unconjugated doxorubicin toward a variety of cultured tumor cell lines. An L929 cell line selected for doxorubicin resistance was as sensitive to the transferrin-doxorubicin conjugate as was the parental unselected line. Quantitative measurements of doxorubicin fluorescence in single L929 cells showed that uptake was similar in amount when cells were exposed to equivalent concentrations of doxorubicin presented either free or as the transferrin-doxorubicin conjugate. However, unconjugated drug fluorescence was distributed in membranes, cytoplasm and nucleus, whereas conjugate fluorescence was confined mainly to the cytoplasmic compartment. In as much as NADPH-dependent free radical formation is a known mechanism of doxorubicin cytotoxicity, localization in the vicinity of NADPH production might facilitate this cytotoxic pathway. Neither cytotoxicity nor uptake of the conjugate quantified by doxorubicin fluorescence was significantly blocked by excess free transferrin, and the conjugate was not concentrated in the plasma membrane at 4 degrees C. These findings suggest that conjugate internalization is not entirely dependent on transferrin receptor binding.

Protective effect of exogenous transferrin against hyperoxia: a study on premature rabbits

We hypothesized that an increase in plasma iron binding capacity would decrease the generation of oxygen radicals and of lipid peroxides. To test this hypothesis, we studied whether supplementation of transferrin (TF) in premature rabbits would modify the degree of hyperoxic lung injury. Animals, delivered prematurely at 29 days of gestation (term 31 days), were randomized and given either 0.5 g/kg of albumin (Alb) (n = 116) or 0.5 g/kg of iron-free TF (n = 132) intravenously within 2 hours after birth. Another group was randomized to receive saline (n = 15), or either 0.35 g/kg (n = 12) or 0.70 g/kg of iron-free TF (n = 8). After exposure to a 100% oxygen environment for 2 or 4 days, the animals were killed, and plasma and bronchoalveolar lavage (BAL) fluid was recovered. Infusion of TF caused a dose-dependent increase in the concentration of TF and an increase in the unsaturated iron-binding capacity. Administration of TF at birth increased the gradient of TF between serum and alveolar epithelial lining fluid on day 4, suggesting decreased alveolar-capillary permeability. BAL fluid and plasma from TF-supplemented animals contained less lipid peroxidation products and more inhibitor of lipid peroxidation than BAL fluid or plasma from Alb-treated animals. In TF-treated animals, the recovery of protein in BAL fluid (TF group, 1.26 +/- 0.07 mg; Alb group, 1.78 +/- 0.10 mg; P = 0.02) and the water content of the extravascular lung tissue (TF group, 78.5 +/- 1.4%; Alb group, 83.2 +/- 1.3%; P = 0.05) were lower than in Alb-treated animals. We propose that supplementation of iron-free TF decreases iron-catalyzed redox reactions and may decrease hyperoxic lung injury in the premature.

Tumor regression with regional distribution of the targeted toxin TF-CRM107 in patients with malignant brain tumors

We investigated regional therapy of recurrent malignant brain tumors with transferrin-CRM107, a conjugate of human transferrin (Tf) and a genetic mutant of diphtheria toxin (CRM107) that lacks native toxin binding. Physiological barriers to delivering proteins to tumor and surrounding infiltrated brain were circumvented with high-flow interstitial microinfusion. At least a 50% reduction in tumor volume on magnetic resonance imaging (MRI) occurred in 9 of 15 patients who could be evaluated (60%), including two complete responses. Peritumoral toxicity developed 1-4 weeks after treatment in three of three patients at 1.0 microg/ml, but in zero of nine patients treated at lower concentrations. No symptomatic systemic toxicity occurred. Regional perfusion with Tf-CRM107 produces tumor responses without systemic toxicity in patients with malignant brain tumors refractory to conventional therapy. Direct interstitial infusion can be used successfully to distribute a large protein in the tumor and infiltrated brain surrounding the tumor.

Antineoplastic drugs that interfere with iron metabolism in cancer cells

Normal iron metabolism can be perturbed with iron chelators, toxic metals that bind to transferrin, toxic metals bound to transferrin or antineoplastic agents covalently linked to transferrin. These agents cause significant inhibition of tumor cell growth in cell culture and have been shown to have significant in vivo antineoplastic activity. Cell culture studies showed that deferoxamine mesylate inhibits cell growth and division in both the MCF-7 human breast and HeLa human cervical carcinoma cell lines. Animal studies demonstrated that when deferoxamine mesylate is injected intravenously into rats that are on a low iron diet, there is a significant reduction in the growth of 13762NF mammary adenocarcinomas. Gallium, indium and the antineoplastic agent cisplatin were bound to the iron binding site of transferrin and inhibit the growth of malignant carcinoma cell lines. Gallium-transferrin and indium-transferrin were at least 10 times more inhibitory to both MCF-7 and HeLa cell lines than their free salts. Further cell culture studies demonstrated that cisplatin-transferrin complexes act synergistically with doxorubicin to inhibit the growth of cultured MCF-7 cells. In a Phase I clinical trial of cisplatin-transferrin complex there was a 36% (four of 11 patients) response rate in breast cancer patients with advanced disease. In a second clinical study the sequential administration of deferoxamine mesylate (2 days at 6 g/day in 8 hrs), cisplatin-transferrin complex (7 days at 500 mg/day) and FAC (5-fluorouracil, doxorubicin and cyclophosphamide at 450, 45 and 450 mg/m2, respectively) to advanced breast cancer patients resulted in partial responses in seven of eight patients treated. Future work will concentrate on substituting transferrin based agents with daunorubicin or doxorubicin attached to the surface of the transferrin, and gallium or indium bound to the iron binding site, to increase efficacy of the second component of the sequential combination chemotherapy.

Alteration in the organ distribution of iron by truncated transferrin: implications for iron chelation therapy

The ability of the partial molecule of transferrin, truncated transferrin (t-Tf), to act as an excretable biologic iron chelator was examined. We confirmed the observations of Zak and Aisen (Zak O, Aisen P. Biochem Biophys Acta 1985;1952:24-8) that thermolysin treatment of human transferrin produces half molecules that retain iron-binding capacity. These molecules are poorly recognized by surface receptors on either human or murine cells. Although the plasma half-life of human transferrin in mice is moderately long (40 hours), injection of t-Tf into mice results in its rapid clearance (half-life = 10 minutes). Injection of iron 59-labeled transferrin results in the deposition of iron in the major hematopoetic organs of mice such as the spleen, bone marrow, and liver. Injection of 59Fe-labeled t-Tf results in the quantitative recovery of iron in the kidneys: 59Fe is retained in the kidney for substantial periods of time with little evidence of its excretion into urine. Injection of iodine 125-labeled t-Tf also results in the deposition of radioactivity in the kidneys, but 125I is rapidly excreted into the urine, where it is detected as free iodine. These results indicate that although t-Tf is directed to the kidney and filtered by the glomerulus, the molecule is reabsorbed and degraded, and iron is retained. These results have implications in the design of iron chelators.

Unresponsiveness to human leukocytes in immunosuppressed mice by combined donor-derived human transferrin and antigens

Previous work on the facilitation of xenogeneic and allogeneic bone marrow engraftment in irradiated mice and dogs with transferrins allowed the development of a model for induction of an apparently durable state of immunological unresponsiveness or 'tolerance' in chemically immunosuppressed mice. The system is based on the simultaneous and combined administration of donor-derived cell antigens, namely human leukocytes, and specific donor-derived or plasma pool human transferrin into BALB/c or C57BL/6 mice previously treated with prednisolone and cyclophosphamide on day 0 and day 1 of the experiment. A properly timed presentation of both donor-specific or plasma pool transferrin and leukocyte antigens into the mice on day 3 and day 16 of the experiment, in the course of initial restoration of their lymphohaemopoietic tissues and cells after severe immunosuppression, results 1-3 months later, in their inability to 'recognize' human donor lymphocytes and to mount an immediate or a delayed-type immune response against human antigens. This durable state of unresponsiveness was evaluated by a complement-mediated cytotoxicity assay, with a mixed lymphocyte culture method and confirmed by the abrogation of the humoral (antibody response to human erythrocytes) and of the cell-mediated (popliteal lymph node test) immune responses in vivo. Our findings demonstrate the capacity of human plasma-derived transferrins to induce a state of durable unresponsiveness (xenogeneic tolerance?) in mice when administered with human antigens in the course of regeneration of stem cells in the bone marrow and lymphatic organs.

Donor-derived plasma transferrin facilitates the engraftment of xenogeneic (rat) bone marrow in irradiated mice

Endogenous factors originally found in the bone marrow (BM) and facilitating the engraftment of xenogeneic (rat) BM in lethally irradiated mice have been recently identified as transferrins (Tf). Tf have been separated and purified from plasma pools of inbred Rii/2 rats and injected in lethally irradiated BALB/c and C57BL/6 mice 1 h before the infusion of BM and for several days after BM transplantation. Other groups of irradiated mice have been similarly treated with human Tf, Tf from other strains of rats different from the BM donors and with human or rat serum albumin. A remarkable facilitation of BM engraftment and a durable graft-versus-host disease (GVHD)-free hemopoietic chimerism have been achieved in the irradiated mice when a combination of BM and Tf from the same donor rat (Rii/2) strain was used for transplantation. Durable survival and persistent chimerism were not observed in the control groups. It seems that donor Tf profoundly affects the outcome of BM transplantation when combined with donor BM. These results indicate that the mechanism by which Tf promotes engraftment of xenogeneic BM deserves investigation in order to improve this novel procedure and to extend it to other species and possibly to man.

Transferrin-ricin A chain toxin limits the development of experimental proliferative vitreoretinopathy

This study was designed to determine the safety and efficacy of transferrin-ricin A chain toxin (Tfr-rRA) at preventing retinal detachment in a rabbit model of proliferative vitreoretinopathy (PVR). The toxicity of intravitreal Tfr-rRA (1000-5000 ng) was determined by indirect ophthalmoscopy and electroretinography on days 1, 5, 8, 16, 26 and 48 post-injection, and by light and transmission electron microscopy conducted on eyes enucleated 48 days after drug exposure. PVR was created by injecting 25,000 homologous fibroblasts into the vitreous cavity of eyes which had previously undergone a gas compression vitrectomy. Eyes then received intravitreal Tfr-rRA (2000 ng) or vehicle. Animals were examined on days 1, 4, 7, 10, 14, 21 and 28 post-injection. Intravitreal injection of 1000 and 2000 ng Tfr-rRA did not show ophthalmoscopic or electroretinographic toxicity. Injection of 5000 ng Tfr-rRA showed mild retinal whitening, retinal arteriolar narrowing, and electroretinographic toxicity, but no morphologic damage, such as photoreceptor loss, nuclear layer vacuolation, or inflammatory cell infiltration, to the retina. Tfr-rRA (2000 ng) injected intravitreally 3 days after fibroblast injection prevented traction retinal detachment in 90% of eyes compared to 22% of sham treated eyes (P < 0.001). The data from this study suggest that transferrin-ricin A chain toxin (2000 ng) safely and effectively limits retinal detachment in experimental PVR.

Facilitation of DLA-incompatible marrow grafts by donor-specific serum transferrin?

Studies in mice have shown that donor-specific plasma transferrin (TF) given to the recipient in the peritransplant period facilitates engraftment of marrow from histoincompatible donors. Dogs given 920 cGy of total body irradiation (TBI) and infused with marrow from an unrelated major histocompatibility complex (DLA) different donor generally fail to engraft; only approximately 20% of dogs achieve sustained engraftment. We have now investigated in this model whether the infusion of donor-specific plasma TF would facilitate engraftment. Ten dogs were given TBI, followed at 23 h by an intravenous dose of TF, at 24 h by marrow from the same donor, and another dose of TF at 48 h; six dogs also received postgrafting methotrexate (MTX). Seven dogs (three of four without MTX, four of six with MTX) had sustained engraftment, and three dogs failed to engraft. A single dog given third-party TF failed to engraft. Among five dogs not given TF two achieved sustained engraftment. This pilot study suggests that donor-specific TF facilitates engraftment of DLA-incompatible marrow. Further studies are warranted.

[In vitro effect of BITO preparation, ceruloplasmin, transferrin, and essentiale on the intensity of lipid peroxidation during thermal injury]

BITO decreased the intesity of lipid peroxdation; intensity of intravascular hemolyses at termal trauma. It increased oxidability of lipids of blood serum, liver and brain. Its antioxidative activity may be explainde by the presence of ceruloplasmin, posessing antioxidative activity may be explained by the presence of ceruloplasmin, posessing ascorbate oxidase, ferroxidase and superoxide dismutase activities. Lipid components of the fraction play a role of "structural antioxidants".

[Treatment of iron deficiency in infancy with iron-acetyl transferrin]

In twenty eight patients with iron deficiency the efficacy of iron-acetil-transferrin treatment (2-3 mg/kg/die) has been evaluated from the changes of the following variables: RBC and reticulocyte count, Hb concentration, MCV, MCH, serum ferritin, serum iron, TIBC, and ZnPP. These variables were assessed before and after three months of treatment in all patients, and after three months from the end of the treatment in thirteen patients. At the end of the treatment there was a significant increase of RBC count, Hb concentration, MCV, MCH, serum ferritin, serum iron, and TIBC, a significant decrease of ZnPP, while reticulocyte count remained essentially unchanged. After three months from the end of the treatment only serum ferritin and ZnPP underwent an additional significant increase and decrease, respectively. In twenty-six patients serum ferritin values returned to normal. The changes of RBC and reticulocyte count, Hb concentration, MCV, serum iron, and TIBC were larger the lower the initial values, suggesting that the efficacy of the treatment is greater the more serious the iron deficiency.

[Metabolic changes of iron in mental patients]

Ferro metabolism abnormalities have been related to behavioral and intelectual performance, depression and low response antidepressants in adults. For studying the clinical meaning of those abnormalities in psychiatric patients, sideremia, transferrin and transferrin saturation level were determined in 228 in-patients. The results show a decreased sideremia and transferrin saturation level in elder patients, and more severe abnormalities in patients with a history of somatic disorders and in those with current somatic pathology associates to psychiatric pathology. There is an increasing cortisol postdexametasona in low transferrin patients, as the only data that relate ferro metabolism and depression. Relation between ferro metabolism and: response to treatment, neuropsychological performance and others demographic, clinical, developmental and biological features of the studied have not been detected.

In vivo cytotoxicity and antineoplastic activity of a transferrin-daunorubicin conjugate

Transferrin, the major iron-binding protein in the plasma of vertebrate species, is an essential growth factor for proliferating malignant cells. The specific receptor binds diferric transferrin and is endocytosed into the cell. We would like to take advantage of this physiologic phenomenon using an active transferrin-daunorubicin conjugate to target cancer cells. We have compared the in vitro and the in vivo activity of free daunorubicin and of daunorubicin transferrin conjugate on cancer cells. The results suggest that our conjugate is less toxic and more active upon malignant cells than the free drug, daunorubicin, while being less toxic for normal cells.

Kinetics of internalization and cytotoxicity of transferrin-neocarzinostatin conjugate in human leukemia cell line, K562

Human serum transferrin was conjugated with an anticancer-active polypeptide, neocarzinostatin, by using N-succinimidyl 1-3-(2-pyridyldithio)propionate. The conjugate consisted of 1.8 mol of neocarzinostatin per 1 mol of transferrin on average and retained cytotoxic activity against human tumor cells. This conjugate was capable of binding to the transferrin receptor of human myelogenous leukemia K562 cells and was internalized by endocytosis. The LD50 values of the conjugate and neocarzinostatin alone in the presence of excess native bovine transferrin were 0.20 microgram/ml and 1.80 micrograms/ml, respectively, suggesting that the effect of the conjugate was greater than that of neocarzinostatin alone. A pulse-chase experiment using 125I-labeled conjugate revealed that 25% of the internalized conjugate was degraded in lysosomes and the rest was recycled back to the cell surface without degradation. About 75% of this conjugate recycled back to the cell surface in 18.3 min (3.4 min for receptor binding and 14.9 min for recycling to the cell surface through the acidosomes), while the rest was delivered from the cell surface to the lysosome in 19.6 min. This phenomenon was confirmed by chasing the radioactivity in subcellular fractions separated by Percoll density gradient centrifugation. Therefore, it was concluded that this conjugate is internalized specifically by transferrin receptors and is at least partly transferred to and accumulated in lysosomal compartments, resulting in the inhibition of cellular DNA synthesis.