Chelators controlling metal metabolism and toxicity pathways: applications in cancer prevention, diagnosis and treatment

Chelating drugs and chelator metal complexes are used for the prevention, diagnosis and treatment of cancer. Cancer cells and normal cells require essential metal ions such as iron, copper and zinc for growth and proliferation. Chelators can target the metabolic pathways of cancer cells through the control of proteins involved in the regulation of these metals and also of other molecules involved in cell cycle control, angiogenesis and metastatic suppression. Other targets include the inhibition of specific proteins such as ribonucleotide reductase involved in DNA synthesis, the inhibition of free radical damage on DNA caused by iron and copper catalytic centers, the inhibition of microbial growth in immuno compromised cancer patients and the decorporation of radioactive and other toxic metals causing cancer. Chelating drugs and metal ions can affect the metabolism, efficacy and toxicity of anti-cancer drugs such as doxorubicin, mitozantrone, bleiomycin and hydroxyurea (HU). Although many experimental chelators have been shown to be effective as anti-cancer agents, only a few, e.g., dexrazoxane, deferoxamine (DFO) and triapine, have reached the stage of clinical testing or application. In many experimental models, deferiprone (L1) has been shown to be effective in cancer prevention and treatment, and in the inhibition of doxorubicin-induced cardiotoxicity. New anti-cancer drugs could be developed using chelators and chelator complexes with platinum and other metals, and also new protocols of combinations of chelators with known anti-cancer drugs.     

Prognostic relevance of mitotic activity in patients with node-negative breast cancer.

The prognostic relevance of mitotic activity was analyzed in a series of 306 patients with node-negative breast cancer treated with locoregional therapy alone, until early relapse. Mitotic activity was evaluated as the number of mitotic figures per 10 high-power fields (mitotic activity index) or per 1000 tumor cells (mitotic index). Counting was carried out blindly by two observers. A high correlation was observed between the two determinations (r(s) =.96, P <.001). For clinical analysis, three mitotic activity index subgroups (mitotic figures/field 相似文献   

Definition of efficiency in vacuum therapy – a randomised controlled trial comparing Redon drains with V.A.C.® Therapy™

Redon drains are still used to suction wounds for vacuum sealing. Vacuum‐assisted closure (V.A.C.^®; Kinetic Concepts Inc, San Antonio, TX) is a computer‐controlled therapy system for delivering topical negative pressure therapy. The efficiency of V.A.C. in the treatment of pressure ulcers was prospectively studied in a randomised controlled trial in which patients with pressure ulcers were randomly assigned to negative pressure wound therapy (NPWT) using either V.A.C. or Redon bottles. The target parameters were absolute and relative proportion of wound area consists of granulation tissue, fibrin and necrosis. Other outcome measures were the number of dressing changes and time invested using each system. The study was terminated after a post hoc analysis after inclusion of ten patients because of the significantly better results when using V.A.C., and the substantially larger care effort needed in the Redon group compared with the V.A.C. group. An increase in surface granulation tissue of 54% was observed in the V.A.C. group, and a reduction in the Redon group (P = 0·001). The Redon group showed an increase in fibrin tissue at the wound base of 21·8%, whereas in the V.A.C group, a 27% reduction was observed (P = 0·035). Necrosis was reduced in the V.A.C. group, but this difference did not reach significance. Redon bottles are not a good alternative for V.A.C. therapy for delivering NPWT.     

Effective Combination Therapy of Deferiprone and deferoxamine for the Rapid Clearance of Excess Cardiac IRON and the Prevention of Heart Disease in Thalassemia. The Protocol of the International Committee on Oral Chelators

The International Committee on Oral Chelators (ICOC) combination therapy protocol involving the administration of deferiprone (L1) during the day (80–110 mg/kg/day) and deferoxamine (DFO) (40–60 mg/kg at least 3 days/week) during the night for 8–12 hours using a pump, or the whole 24 hours using an elastomeric pump infuser, has been tested in 11 thalassemia patients (seven males, four females) over a period of 9–28 months. The patients had variable serum ferritin levels (0.54–4.6 mg/L) and cardiac iron load ranging from normal to severe siderosis levels (MRI T2*: 4.7–45 ms). There was a substantial overall reduction in serum ferritin levels (0.17–2.16 mg/L) and normalization of cardiac iron (MRI T2* >20 ms) in all patients. In two patients with severe and moderate cardiac iron load range levels, cardiac iron normalization was achieved within 9–10 months. Two patients on L1 monotherapy (80–120 mg/kg/day) maintained normal range MRI T2* cardiac iron levels over the same period. The ICOC combination therapy protocol appears to be the most effective and least cumbersome form of chelation treatment for the rapid clearance of excess iron from the heart.     

Molecular factors and mechanisms affecting iron and other metal excretion or absorption in health and disease: the role of natural and synthetic chelators

The maintenance of iron and other essential metal ion balance in humans is based on the presence of homeostatic mechanisms of regulatory absorption, storage, re-utilisation and excretion. There are a number of factors and mechanisms that can affect the level of iron excretion or absorption and overall body iron stores. Net iron loss due to increased iron excretion by comparison to dietary iron absorption is considered as one of the causes of iron deficiency anaemia. Body iron loss greater than normal has been shown in many other conditions. These include the increase in urinary iron excretion observed in iron loaded patients, the substantial reduction in serum ferritin and liver iron of ex-thalassaemia patients several years following bone marrow transplantation and the increase in iron excretion in normal individuals following long term sport activities. There are differences in the metabolism, mode of action, interactions with the iron pools and routes of iron excretion, of the iron chelating drugs deferiprone (L1), deferoxamine and other experimental chelators such as ICL670 in iron-loaded patients. Naturally occurring chelators and some synthetic drugs are known to bind iron and affect iron absorption and excretion. The molecular characteristics of naturally occurring or synthetic chelators can influence other aspects of iron metabolism in addition to iron absorption or excretion. Similar mechanisms and factors can affect the metabolism of other essential metals. The understanding of the mechanisms involved in iron excretion and their overall effects on body iron levels can facilitate the design of new chelators and improved therapeutic protocols for the treatment of conditions of iron and other metal metabolic imbalance and toxicity.     

Low serum ferritin levels are misleading for detecting cardiac iron overload and increase the risk of cardiomyopathy in thalassemia patients. The importance of cardiac iron overload monitoring using magnetic resonance imaging T2 and T2*

The incidence of cardiomyopathy was monitored in a 6-year follow-up study involving 56 transfused thalassemia patients treated with deferoxamine (DFO), deferiprone (L1) or their combination. During this period, five female patients on regular subcutaneous or intravenous DFO presented with cardiac complications. Three patients suffered congestive heart failure and the other two arrhythmias. Four of the five patients maintained serum ferritin levels of about 1 mg/L or below and the fifth about 1.5 mg/L for several years prior to the cardiomyopathy. Cardiac magnetic resonance imaging (MRI) T2* and T2 was performed in four patients after the cardiomyopathy, identifying the presence of moderate-to-heavy siderosis. The treatment of the five patients has since changed, involving mainly the use of L1. Low serum ferritin levels appear to be misleading for detecting cardiac iron overload and this may increase the risk of cardiomyopathy. The MRI T2 and T2* relaxation time measurements are a more accurate method of detecting cardiac iron overload. Chelation therapy using L1 or appropriate L1/DFO combinations can reduce cardiac iron overload and the mortality rate in thalassemia patients.     

Interactions of hydroxycarbamide (hydroxyurea) with iron and copper: implications on toxicity and therapeutic strategies

Presented at the 19th International Conference on Chelation, London, UK, 13-16 November 2009 Preliminary spectrophotometric and potentiometric studies have shown that hydroxycarbamide or hydroxyurea (HU) can interact with copper(II) [Cu(II)], iron(II) [Fe(II)] and Fe(III) ions and form complexes, for example, a ratio of 1 HU:1 metal at pH 5. The affinity for Cu (log β1 = 3.1) and Fe (log β1 = 5) by HU is much lower than that of the Fe and Cu chelating drug deferiprone (L1), which is used for the treatment of iron overload. It is anticipated that under certain conditions of high concentrations of these metal ions such as in transfusional iron overload, the therapeutic, pharmacological and toxicological properties of HU could be affected. It is also suggested that excess chelatable and labile forms of Fe or Cu ions, such as non transferrin-bound iron (NTBI) or intracellular low molecular weight labile iron, are among the main factors that may cause variations in the therapeutic response to HU in cancer, sickle cell anemia, thalassemia intermedia and other groups of patients. Further studies are needed to clarify the interaction mechanisms of HU with metal ions in vitro, in vivo and in clinical conditions.     

Hb A2 Episkopi – a novel δ-globin chain variant [HBD:c.428C>T] in a family of mixed Cypriot–Lebanese descent

Objectives: Thalassaemia is a potentially lethal inherited anaemia, caused by reduced or absent synthesis of globin chains. Measurement of the minor adult haemoglobin Hb A₂, combining α- with δ-globin, is critical for the routine diagnosis of carrier status for α- or β-thalassaemia. Here, we aim to characterize a novel δ-globin variant, Hb A₂ Episkopi, in a single family of mixed Lebanese and Cypriot ancestry with mild hypochromic anaemia and otherwise normal globin genotype, which also presents with a coincidental 0.78-Mb sequence duplication on chromosome 1 (1q44) and developmental abnormalities.

Methods: Analyses included comprehensive haematological analyses, cation-exchange high-performance liquid chromatography (CE-HPLC), cellulose acetate electrophoresis (CAE), Sanger sequencing and structure-based stability predictions for Hb A₂ Episkopi.

Results: The GCT?>?GTT missense mutation, underlying Hb A₂ Episkopi, HBD:c.428C?>?T, introduces a cd142 codon change in the mature protein, resulting in reduced normal Hb A₂ amounts and a novel, less abundant Hb A₂ variant (HGVS: HBD:p.A143V), detectable as a delayed peak by CE-HPLC. The latter was in line with structure-based stability predictions, which indicated that the substitution of a marginal, non-helical and non-interface residue, five amino acids from the δ-globin chain carboxy-terminus, was moderately destabilizing.

Discussion: Detection of the new variant depends on the diagnostic set-up and had failed by CAE and on an independent CE-HPLC system, which, in unfavourable circumstances, may lead to misdiagnoses of β-thalassaemia as α-thalassaemia. Given the mixed background of the affected family, the ethnic origin of the mutation is unclear, and this study thus suggests awareness for possible detection of Hb A₂ Episkopi in both the Cypriot and the Lebanese populations.     

Surveillance data for human leishmaniasis indicate the need for a sustainable action plan for its management and control,Greece, 2004 to 2018

BackgroundThe World Health Organization (WHO) lists human leishmaniasis as a neglected tropical disease; it is not under surveillance at European level.AimWe present surveillance data for visceral (VL) and cutaneous (CL) leishmaniasis for the period 2004 to 2018 in Greece to assess their public health importance.MethodsWe extracted data from the mandatory notification system to analyse separately imported and domestic cases of VL and CL. A case was defined by clinical manifestations compatible with VL or CL and laboratory confirmation.ResultsBetween 2004 and 2018, 881 VL (862 domestic, 19 imported) and 58 CL cases (24 domestic, 34 imported) were recorded. The mean annual notification rate of domestic VL was 0.5 per 100,000 (range: 0.12–1.43/100,000) with a statistically significant increasing trend (p = 0.013). Cases were reported by all regions. The highest notification rate occurred in the age group 0–4 years (1.3/100,000). Overall 24% (164/680) of the cases were immunocompromised and their proportion increased after 2010 (p < 0.001). The mean annual notification rate of domestic CL was 0.05 per 100,000 (range: 0.01–0.19/100,000) with the highest rate in the age group 5–14 years (0.03/100,000). Cases were recorded in six of the 13 regions. Among 34 imported CL cases, 29 were foreign nationals.ConclusionVL is endemic in Greece, with an increasing trend and a considerable burden of severe disease and young children being most affected. CL is rarely reported. A sustainable action plan is needed to reduce the burden of VL and prevent local transmission of CL.