Role of iron biomarkers and iron intakes in lung cancer risk: A systematic review and meta-analysis

Strength in Numbers: Identifying a Significant Association between High Serum Ferritin Levels and Newly Diagnosed Malignancy in a Large Health Organization Cohort

BACKGROUND

Ferritin, an iron storage protein and acute phase reactant, has been implicated in various aspects of human health and disease, including cancer. Previous studies have identified elevated serum ferritin (SF) levels in several cancer types, but a comprehensive examination across different malignancies remains lacking. This study aims to fill this gap by utilizing anonymized data from Maccabi Health Services (MHS), one of Israel's largest health organizations, to explore the association between elevated SF levels and the diagnosis of different malignancies.

METHODS

An extensive dataset from MHS, comprising 2.7 million members, including 1.3 million individuals who underwent SF level testing, was analyzed. ORs and 95% confidence intervals were calculated to assess the association between high SF levels and cancer diagnosis. Subgroup analysis was conducted to investigate variations across different malignancies.

RESULTS

The analysis revealed a significant association between elevated SF levels and cancer diagnosis among MHS members, with an OR of 1.9 (95% confidence interval, 1.71-2.15). Subgroup analysis unveiled differences in the association across malignancy types, with hematologic, hepatobiliary, and respiratory malignancies more strongly associated with high SF levels.

CONCLUSIONS

This study provides further support for the link between elevated SF levels and malignancy, leveraging a vast dataset from MHS, underscoring potential utilities of elevated SF levels as a potential indicator for cancer with a variable role among different malignancy types.

IMPACT

The identification of elevated SF levels as a potential indicator for underlying malignancy for seemingly healthy individuals.

Proteomic Analysis of Plasma Exosomes Enables the Identification of Lung Cancer in Patients With Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is confirmed as an independent risk factor for the development of lung cancer. Although low-dose CT screening significantly reduces the mortality rate of lung cancer, the misdiagnosis and missed diagnosis rates remain high in the COPD population. Additionally, several COPD patients are unable to undergo invasive histological examinations. Therefore, there is an urgent need for minimally invasive biomarkers to screen or diagnose lung cancer in COPD patients. In this study, peripheral blood samples were collected from COPD patients with and without lung cancer. Plasma exosomes (EVs) were extracted for proteomic analysis. Sixteen differentially expressed proteins (DEPs) were preliminarily selected via label-free quantification (LFQ) proteomic technology and comprehensive bioinformatics analysis. Parallel reaction monitoring (PRM) targeted validation identified five candidate proteins associated with COPD with lung cancer. Compared to the COPD group, KRT1, KRT9, and KRT10 were significantly upregulated in the COPD with lung cancer group, while GPLD1 and TF were downregulated. The biomarkers identified in our study provide a foundation for non-invasive screening and diagnosis of lung cancer in COPD patients and exploration of the mechanisms shared between COPD and lung cancer.

Iron and cancer: overview of the evidence from population-based studies

Iron is an essential nutrient required for various physiological processes in the body. However, iron imbalance can potentially contribute to initiating and promoting cancer development. Epidemiological studies have investigated the relationship between dietary iron intake and the risk of different types of cancer, yet, not all studies have consistently shown a significant association between dietary iron and cancer risk. Also, studies have shown different effects of dietary heme and non-heme iron intake on cancer risk. While some epidemiological studies suggest a possible link between high dietary iron (mainly heme-iron) intake and increased cancer risk, the evidence remains inconsistent. Moreover, multiple iron biomarkers, which can mirror physiological iron status, have demonstrated varied correlations with the risk of cancer, contingent upon the specific biomarker analyzed and the type of cancer being investigated. Here, we have investigated the current evidence on the potential relationship between dietary iron intake on one hand, and iron biomarkers on the other hand, with the risk of developing different types of cancer, including breast, prostate, lung, pancreatic, colon, colorectal, and liver cancers. Further research is warranted to better understand the complex relationship between dietary iron, physiological iron and cancer development. Future research should account for factors that affect and interact with dietary iron and physiological iron levels, such as genetic susceptibility, overall diet quality, and lifestyle habits.

Dietary iron and the risk of lung cancer

Animal models have suggested the carcinogenic effect of iron due to its oxidative potential. The lung is particularly vulnerable to oxidative stress. However, epidemiological studies investigating the association between dietary iron and the risk of lung cancer have reported inconclusive results. In this systematic review and meta-analysis, we aimed to clarify this association. Methods: We searched PubMed, Web of Science, Scopus and Google scholar for eligible articles published through May 2023 reporting the Relative Risk (RR), Hazard Ratio (HR) or Odds Ratio (OR) with 95% confidence interval (95% CI). Case-control and cohort studies that examined the relationship between dietary iron and lung cancer risk were included and review and meta-analyses articles, experimental studies, abstracts, letters to editor and studies with insufficient data were excluded. Finally, three case-control studies and 6 cohort studies were included. Random effect models were used to calculate the pooled results. Results: Nine studies (cases n=21,943, participants n=1,542,993) were included. There were no significant associations between the highest dietary total iron (heme and non-heme) (RR: 1.09, 95% CI: 0.78 to 1.51) or heme iron (RR: 1.01, 95% CI: 0.73 to 1.38) intake compared to the lowest intake with lung cancer risk. Null-associations were also observed in the subgroup analysis based on smoking status and lung cancer histology. However, in the subgroup of women (cases n=5074), heme iron was associated with a 14% increase in the risk of lung cancer (RR: 1.14, 95% CI: 1.01 to 1.29). Conclusions: The current results demonstrated that there is no significant relationship between dietary iron intake and the risk of lung cancer. However, a positive association was observed between dietary heme iron and the risk of lung cancer in women, which may require further investigation.

Iron homeostasis in older adults: balancing nutritional requirements and health risks

Iron plays a crucial role in many physiological processes, including oxygen transport, bioenergetics, and immune function. Iron is assimilated from food and also recycled from senescent red blood cells. Iron exists in two dietary forms: heme (animal based) and non-heme (mostly plant based). The body uses iron for metabolic purposes, and stores the excess mainly in splenic and hepatic macrophages. Physiologically, iron excretion in humans is inefficient and not highly regulated, so regulation of intestinal absorption maintains iron homeostasis. Iron losses occur at a steady rate via turnover of the intestinal epithelium, blood loss, and exfoliation of dead skin cells, but overall iron homeostasis is tightly controlled at cellular and systemic levels. Aging can have a profound impact on iron homeostasis and induce a dyshomeostasis where iron deficiency or overload (sometimes both simultaneously) can occur, potentially leading to several disorders and pathologies. To maintain physiologically balanced iron levels, reduce risk of disease, and promote healthy aging, it is advisable for older adults to follow recommended daily intake guidelines and periodically assess iron levels. Clinicians can evaluate body iron status using different techniques but selecting an assessment method primarily depends on the condition being examined. This review provides a comprehensive overview of the forms, sources, and metabolism of dietary iron, associated disorders of iron dyshomeostasis, assessment of iron levels in older adults, and nutritional guidelines and strategies to maintain iron balance in older adults.

Dietary Antioxidants and Lung Cancer Risk in Smokers and Non-Smokers

Smoking is considered a major risk factor in the development of lung diseases worldwide. Active smoking and secondhand (passive) smoke (SHS) are related to lung cancer (LC) risk. Oxidative stress (OS) and/or lipid peroxidation (LP) induced by cigarette smoke (CS) are found to be involved in the pathogenesis of LC. Meta-analyses and other case-control/prospective cohort studies are inconclusive and have yielded inconsistent results concerning the protective role of dietary vitamins C and E, retinol, and iron intake against LC risk in smokers and/or non-smokers. Furthermore, the role of vitamins and minerals as antioxidants with the potential in protecting LC cells against CS-induced OS in smokers and non-smokers has not been fully elucidated. Thus, this review aims to summarize the available evidence reporting the relationships between dietary antioxidant intake and LC risk in smokers and non-smokers that may be used to provide suggestions for future research.