Epidemiologic evidence of an association between body iron stores and risk of cancer

Iron Supplementation Increases Tumor Burden and Alters Protein Expression in a Mouse Model of Human Intestinal Cancer

Iron supplements are widely consumed. However, excess iron may accelerate intestinal tumorigenesis. To determine the effect of excess iron on intestinal tumor burden and protein expression changes between tumor and normal tissues, ApcMin/+ mice were fed control (adequate) and excess iron (45 and 450 mg iron/kg diet, respectively; n = 9/group) for 10 wk. Tumor burden was measured, and two-dimensional fluorescence difference gel electrophoresis was used to identify differentially expressed proteins in tumor and normal intestinal tissues. There was a significant increase (78.3%; p ≤ 0.05) in intestinal tumor burden (mm2/cm) with excess iron at wk 10. Of 980 analyzed protein spots, 69 differentially expressed (p ≤ 0.05) protein isoforms were identified, representing 55 genes. Of the isoforms, 56 differed (p ≤ 0.05) between tumor vs. normal tissues from the adequate iron group and 23 differed (p ≤ 0.05) between tumors from the adequate vs. excess iron. Differentially expressed proteins include those involved in cell integrity and adaptive response to reactive oxygen species (including, by gene ID: ANPEP, DPP7, ITGB1, PSMA1 HSPA5). Biochemical pathway analysis found that iron supplementation modulated four highly significant (p ≤ 0.05) functional networks. These findings enhance our understanding of interplay between dietary iron and intestinal tumorigenesis and may help develop more specific dietary guidelines regarding trace element intake.

Hereditary hemochromatosis: Temporal trends, sociodemographic characteristics, and independent risk factor of hepatocellular cancer – nationwide population-based study

BACKGROUND

Hereditary hemochromatosis (HH) has an increased risk of hepatocellular cancer (HCC) both due to genetic risks and iron overload as iron overload can be carcinogenic; HH impacts the increasing risk of HCC, not only through the development of cirrhosis but concerning hepatic iron deposition, which has been studied further recently.

AIM

To evaluate HH yearly trends, patient demographics, symptoms, comorbidities, and hospital outcomes. The secondary aim sheds light on the risk of iron overload for developing HCC in HH patients, independent of liver cirrhosis complications. The study investigated HH (without cirrhosis) as an independent risk factor for HCC.

METHODS

We analyzed data from National Inpatient Sample (NIS) Database, the largest national inpatient data collection in the United States, and selected HH and HCC cohorts. HH was first defined in 2011 International Classification of Disease - 9^th edition (ICD-9) as a separate diagnosis; the HH cohort is extracted from January 2011 to December 2019 using 275.01 (ICD-9) and E83.110 (ICD-10) diagnosis codes of HH. Patients were excluded from the HH cohort if they had a primary or secondary diagnostic code of cirrhosis (alcoholic, non-alcoholic, and biliary), viral hepatitis, alcoholic liver disease, non-alcoholic fatty liver disease (NAFLD), and non-alcoholic steatohepatitis (NASH). We removed these patients from the HH cohort to rule out bias or ICD-10 diagnostic errors. The HCC cohort is selected from January 2011 to December 2019 using the ICD-9 and ICD-10 codes of HCC. We selected a non-HCC cohort with the 1:1 fixed ratio nearest neighbor (greedy) propensity score method using the patients' age, gender, and race. We performed multivariate analysis for the risk factors of HCC in the HCC and non-HCC matched cohort. We further analyzed HH without cirrhosis (removing HH patients with a diagnosis of cirrhosis) as an independent risk factor of HCC after adjusting all known risk factors of HCC in the multivariate model.

RESULTS

During the 2011-2019 period, a total of 18031 hospitalizations with a primary or secondary diagnosis of HH (excluding liver diseases) were recorded in the NIS database. We analyzed different patients’ characteristics, and we found increments in inpatient population trend with a Ptrend < 0.001 and total hospital cost of care trend from $42957 in 2011 to $66152 in 2019 with a Ptrend < 0.001 despite no change in Length of Stay over the last decade. The multivariate analyses showed that HH without cirrhosis (aOR, 28.8; 95%CI, 10.4–80.1; P < 0.0001), biliary cirrhosis (aOR, 19.3; 95%CI, 13.4–27.6; P < 0.0001), non-alcoholic cirrhosis (aOR, 17.4; 95%CI, 16.5–18.4; P < 0.0001), alcoholic cirrhosis (aOR, 16.9; 95%CI, 15.9–17.9; P < 0.0001), hepatitis B (aOR, 12.1; 95%CI, 10.85–13.60; P < 0.0001), hepatitis C (aOR, 8.58; 95%CI, 8.20–8.98; P < 0.0001), Wilson disease (aOR, 4.27; 95%CI, 1.18–15.41; P < 0.0001), NAFLD or NASH (aOR, 2.96; 95%CI, 2.73–3.20; P < 0.0001), alpha1-antitrypsin deficiency (aOR, 2.10; 95%CI, 1.21–3.64; P < 0.0001), diabetes mellitus without chronic complications (aOR, 1.17; 95%CI, 1.13–1.21; P < 0.0001), and blood transfusion (aOR, 1.80; 95%CI, 1.69–1.92; P < 0.0001) are independent risk factor for liver cancer.

CONCLUSION

Our study showed an increasing trend of in-hospital admissions of HH patients in the last decade. These trends were likely related to advances in diagnostic approach, which can lead to increased hospital utilization and cost increments. Still, the length of stay remained the same, likely due to a big part of management being done in outpatient settings. Another vital part of our study is the significant result that HH without cirrhosis is an independent risk factor for HCC with adjusting all known risk factors. More prospective and retrospective large studies are needed to re-evaluate the HH independent risk in developing HCC.

Basal Ganglia Iron Content Increases with Glioma Severity Using Quantitative Susceptibility Mapping: A Potential Biomarker of Tumor Severity

BACKGROUND AND PURPOSE

Gliomas have been found to alter iron metabolism and transport in ways that result in an expansion of their intracellular iron compartments to support aggressive tumor growth. This study used deep neural network trained quantitative susceptibility mapping to assess basal ganglia iron concentrations in glioma patients.

MATERIALS AND METHODS

Ninety-two patients with brain lesions were initially enrolled in this study and fifty-nine met the inclusion criteria. Susceptibility-weighted images were collected at 3.0 T and used to construct quantitative susceptibility maps via a deep neural network-based method. The regions of interest were manually drawn within basal ganglia structures and the mean voxel intensities were extracted and averaged across multiple slices. One-way ANCOVA tests were conducted to compare the susceptibility values of groups of patients based on tumor grade while controlling for age, sex, and tumor type.

RESULTS

The mean basal ganglia susceptibility for patients with grade IV tumors was higher than that for patients with grade II tumors (p = 0.00153) and was also higher for patients with grade III tumors compared to patients with grade II tumors (p = 0.020), after controlling for age, sex, and tumor type. Patient age influenced susceptibility values (p = 0.00356), while sex (p = 0.69) and tumor type (p = 0.11) did not.

CONCLUSIONS

The basal ganglia iron content increased with glioma severity. Basal ganglia iron levels may thus be a useful biomarker in glioma prognosis and treatment, especially with regard to iron-based cancer therapies.

Role of endolysosome function in iron metabolism and brain carcinogenesis

Iron, the most abundant metal in human brain, is an essential microelement that regulates numerous cellular mechanisms. Some key physiological roles of iron include oxidative phosphorylation and ATP production, embryonic neuronal development, formation of iron-sulfur clusters, and the regulation of enzymes involved in DNA synthesis and repair. Because of its physiological and pathological importance, iron homeostasis must be tightly regulated by balancing its uptake, transport, and storage. Endosomes and lysosomes (endolysosomes) are acidic organelles known to contain readily releasable stores of various cations including iron and other metals. Increased levels of ferrous (Fe2+) iron can generate reactive oxygen species (ROS) via Fenton chemistry reactions and these increases can damage mitochondria and genomic DNA as well as promote carcinogenesis. Accumulation of iron in the brain has been linked with aging, diet, disease, and cerebral hemorrhage. Further, deregulation of brain iron metabolism has been implicated in carcinogenesis and may be a contributing factor to the increased incidence of brain tumors around the world. Here, we provide insight into mechanisms by which iron accumulation in endolysosomes is altered by pH and lysosome membrane permeabilization. Such events generate excess ROS resulting in mitochondrial DNA damage, fission, and dysfunction, as well as DNA oxidative damage in the nucleus; all of which promote carcinogenesis. A better understanding of the roles that endolysosome iron plays in carcinogenesis may help better inform the development of strategic therapeutic options for cancer treatment and prevention.

Risk of hematological malignancy in blood donors: A nationwide cohort study

Background

There has been a concern that blood donations can increase the risk of hematological malignancies. We investigated if blood donations increase the risk of developing hematological malignancies, specifically acute lymphoblastic leukemia, acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), chronic myeloid leukemia, Hodgkin lymphoma, and myeloma, as well other non‐Hodgkin lymphoma.

Study Design and Methods

In total, the study included 1,021,433 Swedish blood donors, with 19.5 million person‐years of follow‐up. Two sets of analysis were performed. In the first cohort analysis, standardized incidence ratios (SIRs) were calculated, comparing the incidence of the different types of hematological cancers in blood donors to that of the general population. In the second analysis, a nested case–control study was conducted, investigating the association between number of donations and the risk of each type of malignancy.

Results

Apart from a modestly elevated risk of CLL (SIR, 1.07; 95% confidence interval [CI], 1.01‐1.15) and a modestly decreased risk of AML (SIR, 0.85; 95% CI, 0.77‐0.83), the risk of hematological malignancies did not differ between blood donors and the general population. In the nested case–control study there were no convincing associations between number of prior whole blood donations and site‐specific malignancy risk.

Conclusions

There was no convincing evidence of an increased risk in any hematological malignancy when interpreting the results from both series of analyses.

Measurement of OH* Generation by Pulverized Minerals Using Electron Spin Resonance Spectroscopy and Implications for the Reactivity of Planetary Regolith

Mineral analogs to silicate phases common to planetary regolith, including olivine; the pyroxenes augite and diopside; the plagioclase feldspars labradorite, bytownite, and albite; the Johnson Space Center-1A lunar regolith simulant; as well as quartz (used as a reference), were subjected to mechanical pulverization by laboratory milling for times ranging from 5 to 45 min. Pulverized minerals were then incubated in an aqueous solution containing the free radical spin trapping compound 5,5-Dimethyl-1-Pyrroline-N-Oxide for times ranging from 5 to 30 min. These slurries were then analyzed by Electron Paramagnetic Resonance spectroscopy to quantify the amount of hydroxyl radical (the neutral charge form of the hydroxide ion, denoted as OH*) formed in solution. We find that all tested materials generate an Electron Paramagnetic Resonance spectrum indicating the formation of OH* with concentrations ranging between 0.1 and 1.5 μM. We also find that, in general, mineral pulverization time is inversely correlated to OH* generation, while OH* generation is positively correlated to mineral fluid incubation time for phases that have iron in their nominal chemical formulae, suggesting the possible action of Fenton reaction as a cofactor in increasing the reactivity of these phases. Our results add to a body of literature that indicates that the finely comminuted minerals and rocks present in planetary regolith are capable of generating highly reactive and highly oxidizing radical species in solution. The results provide the foundation for further in vitro and in vivo toxicological studies to evaluate the possible health risks that future explorers visiting the surfaces of planetary bodies may face from these reactive regolith materials.

Perturbation of Iron Metabolism by Cisplatin through Inhibition of Iron Regulatory Protein 2

Cisplatin is classically known to exhibit anticancer activity through DNA damage in the nucleus. Here we found a mechanism by which cisplatin affects iron metabolism, leading to toxicity and cell death. Cisplatin causes intracellular iron deficiency through direct inhibition of the master regulator of iron metabolism, iron regulatory protein 2 (IRP2) with marginal effects on IRP1. Cisplatin, but not carboplatin or transplatin, binds human IRP2 at Cys512 and Cys516 and impairs IRP2 binding to iron-responsive elements of ferritin and transferrin receptor-1 (TfR1) mRNAs. IRP2 inhibition by cisplatin caused ferritin upregulation and TfR1 downregulation leading to sustained intracellular iron deficiency. Cys512/516Ala mutant IRP2 made cells more resistant to cisplatin. Furthermore, combination of cisplatin and the iron chelator desferrioxamine enhanced cytotoxicity through augmented iron depletion in culture and xenograft mouse model. Collectively, cisplatin is an inhibitor of IRP2 that induces intracellular iron deficiency.

Serum Se, Ni, and As are associated with HPV infection and CIN2+ among Uyghur women in rural China

Background

Cervical cancer incidence and mortality is high in Uyghur ethnics. Their life style and dietary habit were different from other ethnics living together. Study on the role of trace elements in HPV infection and cervical lesion of Uyghur minority is needed for future intervention and prevention work.

Methods

In total, 833 Uyghur women were randomly selected from the screening site and hospital. The concentrations of the trace elements As, Fe, Cd, Ni, Cu, Zn, Mn, and Se were determined by atomic absorption spectrophotometry and inductively coupled plasma atomic emission spectroscopy. Univariate analysis was performed with chi-squared test between the HPV-positive and HPV-negative groups and between the case group and the control group. Multivariate analysis was performed with logistic regression.

Results

An As concentration ≥ 0.02 mg/kg was a risk factor for HPV infection (OR > 1, P < 0.05), and Ni concentration ≥ 0.1232 mg/kg and Se concentration ≥ 0.02 mg/kg were protective factors (OR < 1, P < 0.05). Concentrations of Fe ≥ 6.9153 mmol/L and As ≥0.02 mg/kg were risk factors for CIN2+ (OR > 1, P < 0.05), and concentrations of Ni ≥0.0965 mg/kg and Se ≥0.02 mg/kg were protective factors (OR < 1, P < 0.05).

Conclusions

Low serum concentrations of Se and Ni and a high serum concentration of As might be related to HPV infection and CIN2+ in Uyghur women in rural China.

Carcinogenesis-related changes in iron metabolism in chronic obstructive pulmonary disease subjects with lung cancer

Chronic obstructive pulmonary disease (COPD) is often accompanied by lung cancer. In our previous work, it was observed that matrix metalloproteinase-3 and haptoglobin (HP) polymorphisms were potential markers of enhanced susceptibility to lung cancer development among male COPD subjects. Here, results are reported on blood serum levels of several proteins involved in iron metabolism, inflammation and the oxidative stress response compared between the same groups of subjects. The blood serum levels of tumor necrosis factor α (TNFα), transferrin, hepcidin, ferritin, soluble transferrin receptor and 8-oxo-2'-deoxyguanosine were compared, as well as total iron-binding capacity (TIBC) and ceruloplasmin ferroxidase activity in two groups of subjects: Male COPD patients (54 subjects) and male COPD patients diagnosed with lung cancer (53 subjects). Statistically significant differences were identified between the two groups in transferrin and TNFα levels, as well as in TIBC; all three parameters were lower in the group consisting of COPD patients diagnosed with lung cancer (P<0.01). It was also revealed that HP genotype 1/2 was concomitant with low transferrin blood level in subjects with COPD; this apparent dependence was absent in the COPD + cancer subjects. The results indicate a role of iron metabolism in the susceptibility to lung cancer in COPD-affected subjects. They also emphasize the importance of individual capacity for an effective response to oxidative stress during the pathogenic process as HP is a plasma protein that binds free hemoglobin and its polymorphism results in proteins with altered hemoglobin-binding capacity and different antioxidant and iron-recycling functions.

Evidence that iron overload plus croton oil induce skin tumours in mice

Iron overload is known to occur due to different factors including genetic disorders. It has been shown that iron overload predisposes humans to an increased risk of cancer. However, the mechanism by which iron overload enhances chemically induced carcinogenesis is not known. In this report, for the first time it is shown that iron overload acts as a tumour initiator. Female albino Swiss mice were given iron dextran 1 mg/mouse per day intramuscularly for 15 days and croton oil 0.5 mg in 200 mL acetone/mouse topically twice a week for 30 weeks. During this period, the animals were observed for tumour incidence. There were significantly higher yields of tumours in those animals receiving both iron and croton oil. However, the group of animals treated only with acetone, iron, croton oil and 7,12-dimethylben-z(a)anthracene (DMBA) alone did not develop any tumours during 30 weeks of observation. Further, croton oil-mediated induction in cutaneous lipid peroxidation (LPO) level was higher in the iron-overload group. The results of this study suggest that oxidative stress generated by iron overload is responsible for croton oilmediated skin carcinogenesis.

SmokeHaz: Systematic Reviews and Meta-analyses of the Effects of Smoking on Respiratory Health

BACKGROUND

Smoking tobacco increases the risk of respiratory disease in adults and children, but communicating the magnitude of these effects in a scientific manner that is accessible and usable by the public and policymakers presents a challenge. We have therefore summarized scientific data on the impact of smoking on respiratory diseases to provide the content for a unique resource, SmokeHaz.

METHODS

We conducted systematic reviews and meta-analyses of longitudinal studies (published to 2013) identified from electronic databases, gray literature, and experts. Random effect meta-analyses were used to pool the findings.

RESULTS

We included 216 articles. Among adult smokers, we confirmed substantially increased risks of lung cancer (risk ratio (RR), 10.92; 95% CI, 8.28-14.40; 34 studies), COPD (RR, 4.01; 95% CI, 3.18-5.05; 22 studies), and asthma (RR, 1.61; 95% CI, 1.07-2.42; eight studies). Exposure to passive smoke significantly increased the risk of lung cancer in adult nonsmokers and increased the risks of asthma, wheeze, lower respiratory infections, and reduced lung function in children. Smoking significantly increased the risk of sleep apnea and asthma exacerbations in adult and pregnant populations, and active and passive smoking increased the risk of tuberculosis.

CONCLUSIONS

These findings have been translated into easily digestible content and published on the SmokeHaz website.

Effect of Nordic Walking training on iron metabolism in elderly women

BACKGROUND

Despite several, well-documented pro-healthy effects of regular physical training, its influence on body iron stores in elderly people remains unknown. At the same time, body iron accumulation is associated with high risk of different morbidities.

PURPOSE

We hypothesized that Nordic Walking training would result in pro-healthy changes in an elderly group of subjects by reducing body iron stores via shifts in iron metabolism-regulating proteins.

METHODS

Thirty-seven women aged 67.7±5.3 years participated in this study. They underwent 32 weeks of training, 1-hour sessions three times a week, between October 2012 and May 2013. Fitness level, blood morphology, CRP, vitamin D, ferritin, hepcidin, and soluble Hjv were assessed before and after the training.

RESULTS

The training program caused a significant decrease in ferritin, which serves as a good marker of body iron stores. Simultaneously, the physical cardiorespiratory fitness had improved. Furthermore, blood hepcidin was positively correlated with the ferritin concentration after the training. The concentration of blood CRP dropped, but the change was nonsignificant. The applied training resulted in a blood Hjv increase, which was inversely correlated with the vitamin D concentration.

CONCLUSION

Overall the Nordic Walking training applied in elderly people significantly reduced blood ferritin concentration, which explains the observed decrease in body iron stores.

Risk of illness, hospitalization and death in a cohort of blood donors in Italy

OBJECTIVE

The aim of this study was to determine whether blood donors (BDs), compared with non blood donors (nBDs), present significant differences in risk of illness, hospitalization and death.

METHODS

All subjects included in the database of the Association of Voluntary Italian Blood Donors of Ferrara entered the study. The analysis only included residents who donated at least once. For each BD, four age- and sex-matched non-donor controls were selected from the master archive of the Province of Ferrara. Then, all hospitalizations of BDs and controls from January 2005 to December 2010 were extracted from the hospital admission and discharge database of the region.

RESULTS

During the considered period, 26,140 hospital admissions in BDs and 98,685 in controls were recorded; 11,862 individual BDs and 43,138 nBDs. Compared with controls, BDs were characterized by older age, lower average number of admissions and diagnoses, Charlson comorbidity index score, shorter hospital length-of-stay (LOS), lower mortality rates and higher age at death. Age at death was significantly higher for BDs with longer duration and higher number of donations. In particular, blood donation was not related to an increased risk of malignancies. The main limitation of this study is potential selection bias (i.e. a healthy donor effect). Matching with the control population also has its limitations.

CONCLUSIONS

This study confirms that BDs have a lower risk of hospitalization, and, more specifically, do not have an increased risk of malignancies, leukemias, lymphomas and myeloma.

Hepatic iron overload and hepatocellular carcinoma

In recent years it has become increasingly evident that excess body iron may be complicated by the supervention of hepatocellular carcinoma (HCC). Hereditary hemochromatosis (HH) was the first condition in which hepatic iron overload was shown to predispose to the development of HCC. The inherited predisposition to excessive absorption of dietary iron in HH is almost always the result of homozygosity of the C282Y mutation of the HFE gene, which causes inappropriately low secretion of hepcidin. HCC develops in 8-10% of patients with HH and is responsible for approximately 45% of deaths in the HCC patients. Cirrhosis is almost always present when HCC is diagnosed. Dietary iron overload is a condition which occurs in rural-dwelling Black Africans in southern Africa as a result of the consumption, over time, of large volumes of alcohol home-brewed in iron containers and having, as a consequence, a high iron content. Iron loading of the liver results and may be complicated by malignant transformation of the liver (relative risk of approximately 10.0). Accompanying cirrhosis does occur but is less common than that in HH. The development of HCC as a consequence of increased dietary iron, and the fact that it may develop in the absence of cirrhosis, has been confirmed in an animal model. Drinking water with a high iron content might contribute to the high incidence of HCC in parts of Taiwan. The metabolic syndrome [obesity, insulin resistance type 2 (or diabetes mellitus type 2), non-alcoholic fatty liver or non-alcoholic steatohepatitis] has in recent years become a major public health problem in some resource-rich countries. A link between excess body iron and insulin resistance or the metabolic syndrome has become apparent. The metabolic syndrome may be complicated by the supervention of HCC, and recent evidence suggests that increased body iron may contribute to this complication.

Premenopausal plasma ferritin levels, HFE polymorphisms, and risk of breast cancer in the nurses' health study II

BACKGROUND

Evidence from the Nurses' Health Study II (NHSII) suggests that red meat consumption is associated with increased breast cancer risk in premenopausal women. Iron may be responsible by contributing to oxidative stress or effects on immune function.

METHODS

We conducted a case-control study nested within the NHSII, examining prediagnostic plasma ferritin (n = 795 cases, 795 controls), 15 hemochromatosis gene (HFE) single-nucleotide polymorphisms (SNP; n = 765 cases, 1,368 controls), and breast cancer risk. Cases were diagnosed after providing blood samples between 1996 and 1999. ORs and 95% confidence intervals (CI) were calculated for ferritin levels by conditional logistic regression and for HFE SNPs by unconditional logistic regression.

RESULTS

We did not observe a significant association between ferritin levels and breast cancer (top vs. bottom quartile multivariate OR: 1.05; 95% CI, 0.77-1.45; PTrend = 0.77). Results did not change when restricted to women who were premenopausal at blood draw, and were similar when cases were examined by hormone receptor status, and menopausal status at diagnosis. No HFE SNPs were significantly associated with breast cancer in a log-additive manner. Among controls, ferritin levels were nominally associated with SNPs rs9366637 (PTrend = 0.04), rs6918586 (PTrend = 0.06), and rs13161 (PTrend = 0.07), but results did not remain significant after adjusting for multiple testing.

CONCLUSIONS

Ferritin levels and HFE SNPs were not associated with breast cancer risk in this population.

IMPACT

Components of red meat other than iron are likely responsible for its positive association with breast cancer in premenopausal women.

Dietary and prophylactic iron supplements : Helpful or harmful?

Mild hypoferremia represents an aspect of the ability of the body to withhold iron from pathogenic bacteria, fungi, and protozoa, and from neoplastic cells. However, our iron-withholding defense system can be thwarted by practices that enhance iron overload such as indiscriminate iron fortification of foods, medically prescribed iron supplements, alcohol ingestion, and cigarette smoking. Elevated standards for normal levels of iron can be misleading and even dangerous for individuals faced with medical insults such as chronic infection, neoplasia, cardiomyopathy, and arthritis. We are becoming increasingly aware that the wide-spread hypoferremia in human populations is a physiological response to insult rather than a pathological cause of insult, and that attempts to correct the condition by simply raising iron levels may not only be misguided but may actually impair host defense.

Dose-response relationship of lung cancer to amount smoked, duration and age starting

AIM: To quantify smoking/lung cancer relationships accurately using parametric modelling.

METHODS: Using the International Epidemiological Studies on Smoking and Lung Cancer database of all epidemiological studies of 100+ lung cancer cases published before 2000, we analyzed 97 blocks of data for amount smoked, 35 for duration of smoking, and 27 for age started. Pseudo-numbers of cases and controls (or at risk) estimated from RRs by dose level formed the data modelled. We fitted various models relating log_e RR to dose (d), including βd, βd^Y and βlog_e (1 + Wd), and investigated goodness-of-fit and heterogeneity between studies.

RESULTS: The best-fitting models for log_e RR were 0.833 log_e [1 + (8.1c/10)] for cigarettes/d (c), 0.792 (y/10)^0.74 for years smoked (y) and 0.176 [(70 - a)/10]^1.44 for age of start (a). Each model fitted well overall, though some blocks misfitted. RRs rose from 3.86 to 22.31 between c = 10 and 50, from 2.21 to 13.54 between y = 10 and 50, and from 3.66 to 8.94 between a = 30 and 12.5. Heterogeneity (P < 0.001) existed by continent for amount, RRs for 50 cigarettes/d being 7.23 (Asia), 26.36 (North America) and 22.16 (Europe). Little heterogeneity was seen for duration of smoking or age started.

CONCLUSION: The models describe the dose-relationships well, though may be biased by factors including misclassification of smoking status and dose.

Loss of Hfe leads to progression of tumor phenotype in primary retinal pigment epithelial cells

PURPOSE

Hemochromatosis is a disorder of iron overload arising mostly from mutations in HFE. HFE is expressed in retinal pigment epithelium (RPE), and Hfe(-/-) mice develop age-related iron accumulation and retinal degeneration associated with RPE hyperproliferation. Here, the mechanism underlying the hyperproliferative phenotype in RPE was investigated.

METHODS

Cellular senescence was monitored by β-galactosidase activity. Gene expression was monitored by real-time PCR. Survivin was analyzed by Western blot and immunofluorescence. Migration and invasion were monitored using appropriate kits. Glucose transporters (GLUTs) were monitored by 3-O-methyl-D-glucose uptake. Histone deacetylases (HDACs) were studied by monitoring catalytic activity and acetylation status of histones H3/H4.

RESULTS

Hfe(-/-) RPE cells exhibited slower senescence rate and higher survivin expression than wild type cells. Hfe(-/-) cells migrated faster and showed greater glucose uptake and increased expression of GLUTs. The expression of HDACs and DNA methyltransferase (DNMTs) also was increased. Similarly, RPE cells from hemojuvelin (Hjv)-knockout mice, another model of hemochromatosis, also had increased expression of GLUTs, HDACs, and DNMTs. The expression of Slc5a8 was decreased in Hfe(-/-) RPE cells, but treatment with a DNA methylation inhibitor restored the transporter expression, indicating involvement of DNA methylation in the silencing of Slc5a8 in Hfe(-/-) cells.

CONCLUSIONS

RPE cells from iron-overloaded mice exhibit several features of tumor cells: decreased senescence, enhanced migration, increased glucose uptake, and elevated levels of HDACs and DNMTs. These features are seen in Hfe(-/-) RPE cells as well as in Hjv(-/-) RPE cells, providing a molecular basis for the hyperproliferative phenotype of Hfe(-/-) and Hjv(-/-) RPE cells.

Iron deficiency accelerates Helicobacter pylori-induced carcinogenesis in rodents and humans

Gastric adenocarcinoma is strongly associated with Helicobacter pylori infection; however, most infected persons never develop this malignancy. H. pylori strains harboring the cag pathogenicity island (cag+), which encodes CagA and a type IV secretion system (T4SS), induce more severe disease outcomes. H. pylori infection is also associated with iron deficiency, which similarly augments gastric cancer risk. To define the influence of iron deficiency on microbial virulence in gastric carcinogenesis, Mongolian gerbils were maintained on iron-depleted diets and infected with an oncogenic H. pylori cag+ strain. Iron depletion accelerated the development of H. pylori-induced premalignant and malignant lesions in a cagA-dependent manner. H. pylori strains harvested from iron-depleted gerbils or grown under iron-limiting conditions exhibited enhanced virulence and induction of inflammatory factors. Further, in a human population at high risk for gastric cancer, H. pylori strains isolated from patients with the lowest ferritin levels induced more robust proinflammatory responses compared with strains isolated from patients with the highest ferritin levels, irrespective of histologic status. These data demonstrate that iron deficiency enhances H. pylori virulence and represents a measurable biomarker to identify populations of infected persons at high risk for gastric cancer.

Iron deficiency accelerates Helicobacter pylori-induced carcinogenesis in rodents and humans

Gastric adenocarcinoma is strongly associated with Helicobacter pylori infection; however, most infected persons never develop this malignancy. H. pylori strains harboring the cag pathogenicity island (cag+), which encodes CagA and a type IV secretion system (T4SS), induce more severe disease outcomes. H. pylori infection is also associated with iron deficiency, which similarly augments gastric cancer risk. To define the influence of iron deficiency on microbial virulence in gastric carcinogenesis, Mongolian gerbils were maintained on iron-depleted diets and infected with an oncogenic H. pylori cag+ strain. Iron depletion accelerated the development of H. pylori-induced premalignant and malignant lesions in a cagA-dependent manner. H. pylori strains harvested from iron-depleted gerbils or grown under iron-limiting conditions exhibited enhanced virulence and induction of inflammatory factors. Further, in a human population at high risk for gastric cancer, H. pylori strains isolated from patients with the lowest ferritin levels induced more robust proinflammatory responses compared with strains isolated from patients with the highest ferritin levels, irrespective of histologic status. These data demonstrate that iron deficiency enhances H. pylori virulence and represents a measurable biomarker to identify populations of infected persons at high risk for gastric cancer.

Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BACKGROUND

Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. We summarize evidence for various indices.

METHODS

Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Data were extracted on design, exposures, histological types and confounder adjustment. RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose-response. Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma ("squamous") and adenocarcinoma ("adeno").

RESULTS

287 studies (20 subsidiary) were identified. Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Relationships were somewhat stronger in later starting and larger studies. RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. Covariate-adjustment little affected RR estimates.

CONCLUSIONS

The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. This emphasises the causal nature of the relationship. Our results quantify the relationships more precisely than previously.

Associations of 9p21 variants with cutaneous malignant melanoma, nevi, and pigmentation phenotypes in melanoma-prone families with and without CDKN2A mutations

Chromosome 9p21 has been implicated in the pathogenesis of cutaneous malignant melanoma (CMM). In addition to CDKN2A, the major known high-risk susceptibility gene for CMM, recent studies suggest that other 9p21 genes may be involved in melanoma/nevi development. To identify 9p21 variants that influence susceptibility to CMM and number of nevi in CMM-prone families with and without CDKN2A mutations, we analyzed 562 individuals (183 CMM) from 53 families (23 CDKN2A+, 30 CDKN2A-) for 233 tagging SNPs in 21 genes at 9p21. Single SNP- and gene-based regression analyses were used to assess the risk of CMM, nevi count, skin complexion, and tanning ability associated with these SNPs and genes. We found that SNP rs7023329 in the MTAP gene was associated with number of nevi (P (trend) = 0.003) confirming a recent finding by a genome-wide association study. In addition, three SNPs in the ACO1 gene, rs7855483 (P (trend) = 0.002), rs17288067 (P (trend) = 0.0009), and rs10813813 (P (trend) = 0.005), showed the strongest associations with CMM risk. None of the examined 9p21 SNPs was associated with skin complexion, whereas two SNPs, rs10964862 in IFNW1 (P (trend) = 0.003), and rs13290968 in TUSC1 (P (trend) = 0.0006), were associated with tanning ability. Gene-based analyses suggested that the ACO1 gene was significantly associated with CMM (P = 0.0004); genes IFNW1 (P = 0.002) and ACO1 (P = 0.0002) were significantly associated with tanning ability. Our findings are consistent with recent proposals that additional 9p21 genes may contribute to CMM susceptibility in CMM-prone families. These genetic variants may, at least partially, exert their effects through nevi and tanning ability.

HFE C282Y homozygotes are at increased risk of breast and colorectal cancer

The evidence that mutations in the HFE gene for hemochromatosis are associated with increased cancer risk is inconsistent. The Melbourne Collaborative Cohort Study is a prospective cohort study that commenced recruitment in 1990. Participants born in Australia, New Zealand, the United Kingdom, or Ireland (n = 28,509) were genotyped for the HFE C282Y (substitution of tyrosine for cysteine at amino acid 282) variant. Incident cancers were ascertained from Australian cancer registries during an average of 14 years follow-up. Hazard ratios (HRs), confidence intervals (CIs), and P values were obtained from separate Cox regression analyses for colorectal, breast, and prostate cancers, all other solid cancers, and all cancers. Compared to those with no C282Y variant, C282Y homozygotes were at increased risk of colorectal cancer (HR = 2.28; 95% CI = 1.22, 4.25; P = 0.01) and female C282Y homozygotes were at increased risk of developing breast cancer (HR = 2.39; 95% CI = 1.24, 4.61; P = 0.01), but male C282Y homozygotes were not at increased risk for prostate cancer (HR = 0.96; 95% CI = 0.43, 2.15; P = 0.92). C282Y/H63D compound heterozygotes were not at increased risk for colorectal cancer (HR = 1.27; 95% CI = 0.80, 2.01), breast cancer (HR = 1.16; 95% CI = 0.74, 1.84), or prostate cancer (HR = 1.08; 95% CI = 0.68, 1.70).

CONCLUSION

HFE C282Y homozygotes have twice the risk of colorectal and breast cancer compared with those individuals without the C282Y variant.

Ferritin levels, inflammatory biomarkers, and mortality in peripheral arterial disease: a substudy of the Iron (Fe) and Atherosclerosis Study (FeAST) Trial

BACKGROUND

This study delineated correlations between ferritin, inflammatory biomarkers, and mortality in a cohort of 100 cancer-free patients with peripheral arterial disease (PAD) participating in the Veterans Affairs (VA) Cooperative Study #410, the Iron (Fe) and Atherosclerosis Study (FeAST). FeAST, a prospective, randomized, single-blind clinical trial, tested the hypothesis that reduction of iron stores using phlebotomy would influence clinical outcomes in 1227 PAD patients randomized to iron reduction or control groups. The effects of statin administration were also examined in the Sierra Nevada Health Care (SNHC) cohort by measuring serum ferritin levels at entry and during the 6-year study period. No difference was documented between treatment groups in all-cause mortality and secondary outcomes of death plus nonfatal myocardial infarction and stroke. Iron reduction in the main study caused a significant age-related improvement in cardiovascular disease outcomes, new cancer diagnoses, and cancer-specific death.

METHODS

Tumor necrosis factor (TNF)-alpha, TNF-alpha receptors 1 and 2, interleukin (IL)-2, IL-6, IL-10, and high-sensitivity C reactive protein (hs-CRP) were measured at entry and at 6-month intervals for 6 years. Average levels of ferritin and lipids at entry and at the end of the study were compared. The clinical course and ferritin levels of 23 participants who died during the study were reviewed.

RESULTS

At entry, mean age of entry was 67 +/- 9 years for the SNHCS cohort, comparable to FeAST and clinical and laboratory parameters were equivalent in substudy participants randomized to iron reduction (n = 51) or control (n = 49). At baseline, 53 participants on statins had slightly lower mean entry-level ferritin values (114.06 ng/mL; 95% confidence interval [CI] 93.43-134.69) vs the 47 off statins (127.62 ng/mL; 95% CI, 103.21-152.02). Longitudinal analysis of follow-up data, after adjusting for the phlebotomy treatment effect, showed that statin use was associated with significantly lower ferritin levels (-29.78 ng/mL; Cohen effect size, -0.47 [t(df, 134) = 2.33, P = .02]). Mean follow-up average ferritin levels were higher in 23 participants who died (132.5 ng/mL; 95% CI, 79.36-185.66) vs 77 survivors (83.6 ng/mL; 95% CI, 70.34-96.90; Wilcoxon P = .05). Mean follow-up IL-6 levels were higher in dead participants (21.68 ng/mL; 95% CI, 13.71-29.66) vs survivors (12.61 ng/mL; 95% CI, 10.72-14.50; Wilcoxon P = .018). Ferritin levels correlated (Pearson) with average IL-6 levels (r = 0.1845; P = .002) and hsCRP levels (r = .1175; P = .04) during the study.

CONCLUSION

These data demonstrate statistical correlations between levels of ferritin, inflammatory biomarkers, and mortality in this subset of patients with PAD.

Body iron store as a predictor of oxidative DNA damage in healthy men and women

While iron plays an important role in many cellular functions, excess iron storage induces DNA damage by generating hydroxyl radicals and thus promotes carcinogenesis. However, it remains unclear whether body iron levels that are commonly observed in a general population are related to oxidative DNA damage. We examined the association between serum ferritin concentrations and levels of urinary 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of systemic oxidative DNA damage and repair, in 528 Japanese men and women aged 21-67 years. Men had much higher ferritin levels than in women, and the levels were significantly greater in women aged 50 years or older than in women aged less than 50 years. Urinary 8-OHdG concentrations were significantly and positively associated with serum ferritin levels in all the subgroups. The Spearman rank correlation coefficients were 0.47, 0.76, and 0.73 for men overall, women aged less than 50 years, and women aged 50 years or older, respectively. These associations were materially unchanged after adjustment for potential confounding variables. In men, a more pronounced association was observed in nonsmokers than in smokers. Our results suggest body iron storage is a strong determinant of levels of systemic oxidative DNA damage in a healthy population.

Lactoferrin and cancer disease prevention

Lactoferrin (LF) is an iron-binding glycoprotein that is composed of the transferrin family and is predominantly found in the products of the exocrine glands located in the gateways of the digestive, respiratory, and reproductive systems, suggesting a role in the non-specific defence against invading pathogens. Additionally, several physiological roles have been attributed to LF, namely regulation of iron homeostasis, host defence against infection and inflammation, regulation of cellular growth, and differentiation and protection against cancer development and metastasis. These findings have suggested LF's great potential therapeutic use in cancer disease prevention and/or treatment, namely as a chemopreventive agent. This review looks at the recent advances in understanding the mechanisms underlying the multifunctional roles of LF and future perspectives on its potential therapeutic applications.

Prevalence of hepatic iron overload and association with hepatocellular cancer in end-stage liver disease: results from the National Hemochromatosis Transplant Registry

BACKGROUND

It is unclear whether mild to moderate iron overload in liver diseases other than hereditary haemochromatosis (HH) contributes to hepatocellular carcinoma. This study examined the association between hepatic iron grade and hepatocellular carcinoma in patients with end-stage liver disease of diverse aetiologies.

METHODS

The prevalence of hepatic iron overload and hepatocellular carcinoma was examined in 5224 patients undergoing liver transplantation. Explant pathology reports were reviewed for the underlying pathological diagnosis, presence of hepatocellular carcinoma and degree of iron staining. The distribution of categorical variables was studied using chi(2) tests.

RESULTS

Both iron overload and hepatocellular carcinoma were the least common with biliary cirrhosis (1.8 and 2.8% respectively). Hepatocellular carcinoma was the most common in patients with hepatitis B (16.7%), followed by those with hepatitis C (15.1%) and HH (14.9%). In the overall cohort, any iron overload was significantly associated with hepatocellular carcinoma (P=0.001), even after adjustment for the underlying aetiology of liver disease. The association between hepatic iron content and hepatocellular carcinoma was the strongest in patients with biliary cirrhosis (P<0.001) and hepatitis C (P<0.001).

CONCLUSIONS

Iron overload is associated with hepatocellular carcinoma in patients with end-stage liver disease, suggesting a possible carcinogenic or cocarcinogenic role for iron in chronic liver disease.

Does excess iron play a role in breast carcinogenesis? An unresolved hypothesis

Free iron is a pro-oxidant and can induce oxidative stress and DNA damage. The carcinogenicity of iron has been demonstrated in animal models, and epidemiologic studies have shown associations with several human cancers. However, a possible role of excess body iron stores or of elevated iron intake in breast carcinogenesis has received little attention epidemiologically. We propose that iron overload and the disruption of iron homeostasis with a resulting increase in free iron may contribute to the development of breast cancer, and we summarize the relevant evidence from mechanistic studies, animal experiments, and studies in humans. Over time a high intake of iron can lead to iron overload. Furthermore, body iron stores increase in women following menopause. Reactive oxygen species produced by normal aerobic cellular metabolism can lead to the release of free iron from ferritin. In the presence of superoxide radical and hydrogen peroxide, stored ferric iron (Fe(3+)) is reduced to ferrous iron (Fe(2+)), which catalyzes the formation of the hydroxyl radical (*OH). *OH in turn can promote lipid peroxidation, mutagenesis, DNA strand breaks, oncogene activation, and tumor suppressor inhibition, increasing the risk of breast cancer. In addition to its independent role as a proxidant, high levels of free iron may potentiate the effects of estradiol, ethanol, and ionizing radiation - three established risk factors for breast cancer. In order to identify the role of iron in breast carcinogenesis, improved biomarkers of body iron stores are needed, as are cohort studies which assess heme iron intake. Ultimately, it is important to determine whether iron levels in the breast and iron-induced pathology are higher in women who go on to develop breast cancer compared to women who do not.

Liver exposure to xenobiotics: the aging factor and potentials for functional foods

Hepatocytes isolated from 20- and 4-month Wistar rats and cultured with or without alpha-linolenic acid (LNA) were then added with nutraceutical YHK or sylibin before the test with iron or copper. Overall, YHK proved to be more effective than sylibin in Fe/Cu-induced peroxidative damage on normal and LNA-loaded hepatocytes (p < 0.05). YHK exerted a significant protection against DPPH radical-scavenging activity in the "old" group (p versus sylibin) and against lipophilic generators in both age groups (p < 0.05 versus sylibin). Both compounds were ineffective on age-related increase of surface-charge density. These preliminary data suggest that age per se enhances the vulnerability of hepatocytes to xenobiotics, whereas some safe nutraceuticals seem to exert significant protective effects.

Iron status and risk of cancers in the SU.VI.MAX cohort

The aim of the present study was to evaluate the relation between iron status and cancer in a population of middle-aged adults living in France where iron supplementation and iron-fortified foods are rarely used. The SU.VI.MAX study is a randomized, double-blind, placebo-controlled primary prevention trial evaluating the effect of antioxidant supplementation on chronic diseases in women aged 35-60 and men aged 45-60 y. At baseline, concentrations of hemoglobin, serum transferrin and serum ferritin were measured in 10,197 subjects. Data on dietary intake were estimated from six 24-h dietary records completed during the first 2 study years and available for 5287 subjects. All cancer cases that occurred during the 7.5-y follow-up were validated. In men, baseline serum transferrin and serum ferritin concentrations did not differ between subjects with cancers (n = 467) and those without. In women, serum ferritin was higher (P < 0.0001) and serum transferrin tended to be lower (P < 0.08) in cancer cases. Iron status was not related to cancer risk in men, but women with serum ferritin concentrations > 160 microg/L had an increased risk of cancer (odds ratio = 1.88, 95% CI: 1.05,3.35). No relation was found between dietary iron intake and risk of all cancer sites combined for either men or women. Our results suggest that iron status is not a predictor of cancer risk in men, whereas a serum ferritin concentration > 160 microg/L may be associated with an increase in cancer risk in women.

HFE gene mutations in susceptibility to childhood leukemia: HuGE review

The hereditary hemochromatosis (HHC) gene, HFE on chromosome 6p21.3, encodes a protein involved in iron homeostasis. HFE mutations have low penetrance with a mild effect on serum iron levels. Animal, twin, and population studies have shown that carrier state for C282Y can increase iron levels. A proportion of heterozygotes show slightly elevated serum iron levels. Increased serum iron has been suggested to increase the risk for oxidative damage to DNA. Epidemiologic studies established a correlation between iron levels and cancer risk. Case-control studies have reported associations between HFE mutations C282Y/H63D and several cancers, some of which in interaction with the transferrin receptor gene TFRC or dietary iron intake. Increased cancer risk in C282Y carriers is likely due to higher iron levels in a multifactorial setting. In childhood acute lymphoblastic leukemia (ALL), there is an association of C282Y with a gender effect in two British populations. No association has been found in acute myeloblastic leukemia and Hodgkin disease in adults. The childhood leukemia association possibly results from elevated intracellular iron in lymphoid cells increasing the vulnerability to DNA damage at a critical time window during lymphoid cell development. Interactions of HFE with environmental and genetic factors, most of which are recognized, may play a role in modification of susceptibility to leukemia conferred by C282Y. Given the population frequency of C282Y and the connection between iron and cancer, clarification of the mechanism of HFE associations in leukemia and cancer will have strong implications in public health.

Metal-induced oxidative damage in cultured hepatocytes and hepatic lysosomal fraction: beneficial effect of a curcumin/absinthium compound

OBJECTIVE

Metals undergo redox cycling and there is increasing evidence of free radical generation and oxidative injury in the pathogenesis of liver injury and fibrosis in metal storage diseases. The aim of the present study was to test a natural hepatoprotective compound in metal-induced liver injury.

METHODS

Hepatocytes were isolated from Wistar rats by collagenase perfusion method and cultured as such and also with alpha-linolenic acid (LNA)-bovine serum albumin (BSA). Hepatocytes were then cultured with a graded dilution of PN-M001 (100 microg/mL and 200 microg/mL), which is a curcuma/absinthium-containing compound, or sylibin (100 microg/mL) dissolved in dimethyl sulfoxide for 10 min before the addition of metallic salts (iron, copper and vanadium). Lysosomal fractions were prepared for lysosome fragility tests in which beta-galactosidase activity and lactate dehydrogenase (LDH) leakage were measured, as well as oxidative damage tests in the presence of hydrophilic and lipophilic free radical generators. Quenching activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH) was also assessed.

RESULTS

Malonildialdehyde accumulation in the medium showed a direct time-course increase with incubation time. Both PN-M001 and sylibin showed a significant protective effect against all challenge metal ions, as expressed by the half inhibition concentration (IC(50)) against lipid peroxidation. However, on a molar ratio, sylibin seemed to be more effective than PN-M001 in Fe-induced peroxidative damage (P < 0.05). Both test compounds, irrespective of the concentration, significantly reduced the LDH and beta-galactosidase concentration in the lysosomal fractions. As compared with untreated lysosomal fractions challenged with the two peroxide radicals generators, either PN-M001 or sylibin exerted significant protection However, PN-M001 was significantly better than sylibin in suppressing acid phosphatase enzyme activity. Both compounds showed comparable and significant DPPH radical-scavenging activity.

CONCLUSION

These data support the potential clinical application of curcumin-containing compounds.

Iron, hemochromatosis, and hepatocellular carcinoma

Hereditary hemochromatosis (HH) is associated with an increased risk for hepatocellular carcinoma (HCC). The risk previously had been estimated to be as high as 200-fold increased. Recent studies suggest that the risk for HCC in HFE -associated HH may be much lower and occurs predominantly in patients with cirrhosis at the time of diagnosis. The risk for HCC also is increased among patients with African iron overload and possibly in other iron-loading disorders such as homozygous beta thalassemia. The greatly increased iron stores in the liver observed in these disorders can stimulate carcinogenesis via both direct and indirect pathways. The prevalence of HCC also appears to be higher among patients with end-stage liver disease undergoing liver transplantation. It is not clear whether mildly to moderately increased hepatic iron stores or HFE mutations are associated independently with an increased risk for HCC among patients with other types of liver disease. In this article, the incidence and prevalence of HCC in patients with HH and other liver diseases associated with iron overload are discussed as well as the possible mechanisms for the increased risk for hepatic carcinogenesis in these disorders.

Progressive iron overload enhances chemically mediated tumor promotion in murine skin

Iron overload has been shown to enhance chemically mediated cutaneous tumor promotion in animals. However, the majority of these animal studies have used high concentrations of iron before initiating tumor development. The current study was designed to evaluate the effect of small doses of iron on the promotion stage of chemically mediated cutaneous carcinogenesis. We found an increased tumor response in mice initiated with dimethylbenz(a)anthracene (DMBA) when iron at the dose levels of 0.5, 1.0, and 1.5mg/mouse was injected (intramuscularly) once a week into mice at the promotion stage of skin carcinogenesis, employing 12-O-tetradecanoyl phorbol-13-acetate (TPA)/benzoyl peroxide (BPO) as tumor promoter. The appearance of first papilloma and the number of tumors/mouse were recorded weekly. When compared to the control (non-iron-treated) group, the iron-treated groups showed an augmented incidence of tumors and number of tumors/mouse. In iron-treated mice, tumors appeared earlier than in the control group. TPA/BPO treatment resulted in a significant decrease in the activities of antioxidant enzymes and depletion in the level of epidermal reduced glutathione (GSH). TPA treatment in non-iron-treated mice resulted in approximately 20-40% decrease in GSH level and in the activities of antioxidant enzymes, whereas 1.5-mg iron treatment along with TPA treatment resulted in about approximately 30-70% decrease in GSH level and in the activities of antioxidant enzymes. Similarly, treatment of iron along with BPO treatment resulted in a dose-dependent higher depletion of GSH and the antioxidant enzymes as compared to non-iron-treated animals treated with BPO. Further, TPA/BPO-mediated induction in ornithine decarboxylase activity and [3H]thymidine incorporation in cutaneous DNA was approx two- to threefold higher in mice treated with iron as compared to non-iron-treated mice. Cutaneous lipid peroxidation and iron levels were also higher in mice treated with iron as compared to non-iron-treated mice. These data suggest that progressive iron overload can enhance the tumor promotion ability of TPA/BPO in DMBA-initiated murine skin.

Reliability of serum iron, ferritin, nitrite, and association with risk of renal cancer in women

Reliability of serum levels of iron, ferritin and nitrite (NO(2)(-)) over a 2-year period were evaluated in 40 healthy women (20 pre-menopausal and 20 post-menopausal), ages 39-65 years, from the New York University Women's Health Study (NYUWHS). Three blood samples per woman collected at yearly intervals were analyzed. Reliability coefficients (RCs) of serum iron, ferritin, and nitrite were 0.03 (95% confidence interval (CI), 0-0.33), 0.90 (95% CI, 0.79-0.95), and 0.72 (95% CI, 0.50-0.86), respectively, for pre-menopausal women, and 0.26 (95% CI, 0-0.56), 0.77 (95% CI, 0.59-0.89), and 0.55 (95% CI, 0.30-0.77), respectively, for post-menopausal women. In a case-control study nested within NYUWHS cohort, serum levels of nitrite, ferritin, and iron were measured in women apparently healthy at the time of blood donation but diagnosed with renal cancer 1.8-12.2 years later (n=24) and in individually matched controls (two per case). The results suggest that high serum levels of ferritin and nitrite may be associated with a decreased risk of renal cancer (odds ratio (OR), 0.55, 95% CI, 0.15-2.01 for ferritin, and OR, 0.52, 95% CI, 0.17-1.60 for nitrite in women with above median level as compared to women with below median level). The possible role of ferritin and nitrite in renal cancer is discussed.

Morbidity risk in HFE associated hereditary hemochromatosis C282Y heterozygotes

Hereditary hemochromatosis (HHC) is a late-onset, autosomal recessive disorder leading to a chronic iron overload syndrome, finally causing diabetes, cardiomyopathy and liver disease. HHC is the most common single gene disorder in northern Europeans that occurs with a frequency of approximately 0.5%, and most of these patients carry the C282Y and H63D mutation in the HFE gene on chromosome 6p21.3. The vast majority of HHC patients are homozygous for the C282Y mutation, but HHC phenotypes are observed in other genotypes. Expression of the disease, in those homozygous for the C282Y mutation, is highly variable depending on the various features of the population studied. C282Y heterozygotes have slightly increased iron stores and in absence of other genetic and/or environmental factors do usually not develop the HHC phenotype. It is currently a matter of debate whether C282Y heterozygotes may have an increased risk for morbidity. Different studies investigating the association of C282Y heterozygocity with morbidity have given conflicting results, as is exemplified by extrahepatic cancers, cardiovascular diseases, alcoholic liver disease, and diabetes. However, there are examples of clear and unambiguous disease associations, such as with sporadic pophyria cutanea tarda. It remains to be seen whether a strong correlation between the C282Y heterozygous state and distinct pathological conditions will exist and large-scale genotyping studies will help to identify such potential risk groups in the future.

Low iron state is associated with reduced tumor promotion in a two-stage mouse skin carcinogenesis model

The purpose of this study was to investigate the effect of low iron state in a two-stage mouse skin carcinogenesis model using 7,12-dimethylbenz[a]anthracene (DMBA)-initiated and benzoyl peroxide (BPO)-promoted cutaneous tumorigenesis. All mice were treated with DMBA. Low iron state was achieved by injection with phenylhydrazine hydrochloride and feeding low iron diet. A low iron state resulted in a decrease in tumor incidence (papillomas and carcinomas) and number of tumors/mouse. Also, the conversion of papillomas to carcinomas was lower in mice on a low iron state. BPO treatment enhanced epidermal lipid peroxidation (LPO) and was accompanied by a depletion in the level of epidermal reduced glutathione (GSH) and decrease in the activities of antioxidant enzymes. BPO treatment also increased ornithine decarboxylase (ODC) activity and [3H]thymidine incorporation into cutaneous DNA. Mice in a low iron state were less susceptible to the effects of BPO treatment, as was apparent from a partial recovery of GSH levels and the activities of antioxidant enzymes, as well as a lower induction in ODC activity, [3H]thymidine incorporation into cutaneous DNA and lesser epidermal LPO. As expected, cutaneous iron levels were lower in mice on a low iron state. Thus, our data show that the tumor-promoting potential of BPO is reduced by low iron state in a two-stage mouse skin carcinogenesis model.

Chronic exposure to high levels of dietary iron fortification increases lipid peroxidation in the mucosa of the rat large intestine

There is increasing evidence that excess dietary iron may be a risk factor for colorectal cancer. However, the majority of animal studies looking at possible mechanism have used unrealistically high concentrations of iron. The current study was designed to test whether chronic exposure to high levels of iron fortification affects the free radical generating capacity of the lumenal contents, mucosal lipid peroxidation and crypt cell proliferation. Rats were fed diets containing either 29 mg/kg or 102 mg/kg of elemental iron for 6 mo. The free radical generating capacity of lumenal contents was assessed using an in vitro assay. Crypt cell proliferation rate was measured in tissues taken from the cecum and colon, with the remaining tissue being used for the assessment of lipid peroxidation. Chronic feeding of iron did not increase crypt cell proliferation rate in either the colon or cecum, but it was associated with an increase in free radical generating capacity in the colon and increased lipid peroxidation, particularly in the cecum. These results may be relevant to epidemiological evidence showing that dietary iron is associated with the risk of proximal colon cancer in humans.

Role of iron-dextran on 7,12-dimethylbenz(a) anthracene-initiated and croton oil-promoted cutaneous tumorigenesis in normal and pregnant mice

Skin chemical carcinogenesis has been divided into the process of initiation, promotion and progression. Earlier, we showed the role of iron overload in the promotion stage of skin carcinogenesis. In this communication, we report that iron overload does not augment croton oil-mediated tumor promotion in 7,12-dimethylbenz(a)anthracene (DMBA)-initiated pregnant mice skin tumorigenesis. Virgin female Swiss mice were given 1 mg iron/mouse/day parenterally for 2 weeks to induce iron overload. After the last injection, a group of mice was left with male mice for 10 days. These animals showed an increase in cutaneous iron concentration as compared to normal mice. Papillomas were induced in mice skin by a single topical application of DMBA as initiator. A week after the initiation, promoting agent, croton oil was applied twice per week for 20 weeks. The appearance of the first tumor (papilloma), number of tumors/mouse and percentage incidence were recorded. When compared to the iron unloaded control and iron overload pregnant groups, the iron overload virgin animals showed an increased incidence of tumors. In iron overload virgin animals, tumors appeared earlier and also the numbers of tumors/mouse were significantly higher. However, in iron overload pregnant animals, diminished tumor incidence was observed and the numbers of tumors matched the result of normal pregnant animals. Our results show that iron overload in pregnant mice does not participate in the augmentation of DMBA- and croton oil-induced skin tumorigenesis.