Joint effects of dietary trace metals and DNA repair capacity in lung cancer risk

Mendelian randomization study indicates lack of causal associations between iron status and lung cancer

Observational studies provided conflicting results on the association between iron status and the risk of lung cancer. The aim of our study was to investigate the effect of genetically determined iron status on lung cancer risk using a mendelian randomization (MR) approach. Single-nucleotide polymorphisms for iron status were selected from a genome-wide meta-analysis of 48,972 subjects. Genetic association estimates for risk of lung cancer were derived from a Genome-Wide Association Study (GWAS) summary performed by the International Lung Cancer Consortium. The inverse-variance weighted method was used for the main analyses and sensitivity analyses. MR analysis demonstrated that increased genetically-predicted iron status did not causally increase risk of lung cancer. The odds ratios were 1.11 (95% CI, 0.92, 1.34; P = .26), 0.76 (95% CI, 0.52, 1.12; P = .17), 1.09 (95% CI, 0.86, 1.38; P = .47), and 0.91 (95% CI, 0.81, 1.02; P = .11) per 1 standard deviation increment of serum iron, ferritin, transferrin saturation, and transferrin levels, respectively. No observed indication of heterogeneity (P for Q > 0.05) or pleiotropy (P for intercept > 0.05) were found from the sensitivity analysis. The MR study indicated that genetic iron status was not causally associated with the risk of lung cancer, the causal relationship between iron status and lung cancer needs to be further elucidated by additional studies that strictly control for confounding factors.

Ferroptosis and Its Potential Role in Lung Cancer: Updated Evidence from Pathogenesis to Therapy

Lung cancer is characterized by high morbidity and mortality rates, and its occurrence is associated with many types of cell death. As a new form of regulated cell death, ferroptosis is an iron- dependent pattern of cell death and characterized by lethal accumulation of lipid-based reactive oxygen species (ROS), which is different from apoptosis, necrosis and autophagy at both the morphological and biochemical levels. It plays an important role in the development of lung cancer and induction of ferroptosis in lung cancer cells has become a new strategy for anti- lung cancer treatment. However, a few reviews summarized ferroptosis and its role in lung cancer has not been elucidated, and the precise mechanism of ferroptosis modeling lung cancer has not yet been revealed till date. Herein, we review the latest literature on the process of ferroptosis regarding lung cancer, including basic molecular or biology mechanistic studies both in vivo and in vitro, as well as human studies with a more translational or clinical approach. This review provides a practical, concise and updated outline on the mechanisms and therapeutic strategies in lung cancer with ferroptosis alterations. Looking ahead, further studies are required to uncover the possible modulatory relationship between ferroptosis and lung cancer.

Association of various dietary habits and risk of lung cancer: an updated comprehensive literature review

Lung cancer remains the leading cause of cancer death in both men and women worldwide. Tobacco smoking remains the single most important factor. Recent research has focused on the role of nutrition and dietary habits on lung tumorigenesis. With many individual reports on separate dietary aspects, no single review is available in the literature that summarizes the updated studies. To our knowledge, this is the first review that comprehensively reviews the updated literature on the effect of dietary habits on lung cancer. This review was concluded in February 2019 and included all meta-analyses, systematic reviews, and literature reviews. Thirty studies were retrieved in total. Items in the diet that offer a protective effect on lung parenchyma are fruits, vegetables, fish, nuts, soy, B vitamins, vitamin D, vitamin E, vitamin C, and zinc. Changing dietary habits to decrease the risk of lung cancer can be performed in parallel with smoking cessation programs. There is a need for future studies with large sample sizes to accurately evaluate some aspects of nutrition and their effect on lung cancer risk. Physicians are encouraged to provide nutritional advice to their patients.

Circulating essential metals and lung cancer: Risk assessment and potential molecular effects

OBJECTIVE

Essential metals play important roles in the carcinogenic process. However, seldom longitudinal investigations have evaluated their roles in lung cancer development. We aimed to investigate the associations between multiple essential metals and lung cancer incidence and to explore the potential mechanisms.

METHODS

A nested case-control study of 440 incident lung cancer cases and 1:3 frequency matched 1320 healthy controls from the Dongfeng-Tongji Cohort was conducted. The baseline plasma concentrations of 11 essential metals (cobalt, copper, iron, manganese, molybdenum, rubidium, selenium, strontium, stannum, vanadium, and zinc) were measured, and their associations with lung cancer incidence were estimated. Effect of positive metal (zinc) on 4-year telomere attrition was then evaluated among an occupational cohort of 724 workers. We also assessed the transcriptional regulation effects of plasma zinc on mRNA expression profiles, and the expressions of zinc-related genes were further compared in pair-wised lung tumor and normal tissues.

RESULTS

Elevated plasma level of zinc was associated with lower incident risk of lung cancer [OR (95% CI) = 0.89 (0.79, 0.99)] and decreased 4-year telomere attrition [β (95% CI) = -0.73 (-1.27, -0.19)]. These effects were pronounced among males. In particularly, zinc could regulate the expressions of 8 cancer-related genes, including SOD1, APE, TP53BP1, WDR33, LAPTM4B, TRIT1, HUWE1, and ZNF813, which were over-expressed in lung tumor tissues.

CONCLUSIONS

We propose that high plasma zinc could prevent incident lung cancer, probably by slowing down telomere attrition and regulating the expressions of cancer-related genes. These results provided a new insight into lung cancer prevention.

Association between serum copper levels and lung cancer risk: A meta-analysis

OBJECTIVE

To evaluate the association between serum copper levels and lung cancer risk.

METHODS

We searched the electronic PubMed, WanFang, CNKI, and SinoMed databases to identify studies including information on serum copper levels and lung cancer. Standard mean differences and corresponding 95% confidence intervals were calculated using Stata 12.0 software. We performed a meta-analysis on the identified studies overall and according to geographic location. We also evaluated heterogeneity among the studies and the occurrence of publication bias.

RESULTS

Thirty-three articles including 3026 cases and 9439 controls were included in our study. The combined results showed that serum copper levels were higher in patients with lung cancer compared with controls without lung cancer, though the results showed high heterogeneity. In a subgroup analysis according to geographic location, significant associations between copper levels and lung cancer were found for both Asian and European populations. No publication bias was detected in this meta-analysis.

CONCLUSIONS

High serum copper levels could increase the risk of lung cancer, suggesting that environmental copper exposure may be a risk factor for the development of lung cancer.

Serum copper and zinc levels and the risk of oral cancer: A new insight based on large-scale case-control study

OBJECTIVE

Limited evidence exists on the roles of serum copper (Cu) and zinc (Zn) in oral cancer risk. We aimed to preliminarily explore the association between serum Cu and Zn levels and oral cancer risk with relatively large-scale samples.

METHODS

Serum Cu and Zn levels of 344 oral cancer patients and 1,122 matched healthy controls in this case-control study were measured by inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Restricted cubic spline revealed the U-shaped relationship between serum Cu or Zn levels and the risk of oral cancer. Serum deficient or elevated levels of Cu were significantly associated with the risk of oral cancer: The ORs were 1.38 (95% CI: 1.01-1.89) and 2.82 (95% CI: 1.60-4.98), respectively. The positive association of serum low or high levels of Zn with oral cancer risk was also observed: The ORs were 2.72 (95% CI: 1.60-4.62) and 12.41 (95% CI: 9.09-16.93), respectively. Additionally, there were multiplicative interactions between the aforementioned trace elements and smoking.

CONCLUSIONS

This preliminary study suggests that both serum excess and deficient levels of Cu or Zn were significant correlation with oral cancer risk, which may provide a new insight on the roles of serum Cu and Zn in oral cancer.

MicroRNA-related genetic variants in iron regulatory genes, dietary iron intake, microRNAs and lung cancer risk

Background

Genetic variations in MicroRNA (miRNA) binding sites may alter structural accessibility of miRNA binding sites to modulate risk of cancer. This large-scale integrative multistage study was aimed to evaluate the interplay of genetic variations in miRNA binding sites of iron regulatory pathway, dietary iron intake and lung cancer (LC) risk.

Patients and methods

The interplay of genetic variant, dietary iron intake and LC risk was assessed in large-scale case-control study. Functional characterization of the validated SNP and analysis of target miRNAs were performed.

Results

We found that the miRNA binding site SNP rs1062980 in 3' UTR of Iron-Responsive Element Binding protein 2 gene (IREB2) was associated with a 14% reduced LC risk (P value = 4.9×10 - 9). Comparing to AA genotype, GG genotype was associated with a 27% reduced LC risk. This association was evident in males and ever-smokers but not in females and never-smokers. Higher level of dietary iron intake was significantly associated with 39% reduced LC risk (P value = 2.0×10 - 8). This association was only present in individuals with AG + AA genotypes with a 46% reduced risk (P value = 1.0×10 - 10), but not in GG genotype. The eQTL-analysis showed that rs1062980 significantly alters IREB2 expression level. Rs1062980 is predicted to alter a miR-29 binding site on IREB2 and indeed the expression of miR-29 is inversely correlated with IREB2 expression. Further, we found that higher circulating miR-29a level was significantly associated with 78% increased LC risk.

Conclusion

The miRNA binding site SNP rs1062980 in iron regulatory pathway, which may alter the expression of IREB2 potentially through modulating the binding of miR-29a, together with dietary iron intake may modify risk of LC both individually and jointly. These discoveries reveal novel pathway for understanding lung cancer tumorigenesis and risk stratification.

Zinc transporters are differentially expressed in human non-small cell lung cancer

Lung cancer is one of the most common human malignancies worldwide, but its oncogenesis process remains unclear. Recent studies demonstrated that zinc (Zn) and Zn transporters were associated with the development and progression of human cancers. The role of Zn transporters including ZIPs and ZnTs in lung cancer, however, has never been evaluated. Thus, we aimed to investigate the expression levels of all human Zn transporters, including 14 ZIPs and 10 ZnTs, in eight different lung cancer cell lines and paired human tumor tissues. We observed great variations in ZIPs and ZnTs mRNA levels across cell lines and human lung cancer specimens. ZIPs showed a tendency to be upregulated, while ZnTs exhibited a downward expression trend. ZIP4 was overexpressed in six lung cancer cell lines and 59% (26/44) of tumor tissues, which was consistent with results from lung cancer datasets including TCGA database. Our results indicated that the dysregulation of Zn transporters may contribute to lung tumorigenesis.

Dietary mineral intake and lung cancer risk: the Rotterdam Study

Objective

Limited data are available on the role of mineral intake in the development of lung cancer (LC). We investigated whether dietary calcium, copper, iron, magnesium, selenium and zinc intake were associated with LC risk.

Methods

We analyzed data from 5435 participants of the Rotterdam Study, a prospective population-based cohort study among subjects aged 55 years and older. At baseline (1990–1993), diet was measured by a validated food frequency questionnaire. LC events were diagnosed on the basis of pathology data and medical records. Hazard ratios (HRs) on LC for energy-adjusted mineral intake were calculated using Cox regression models while adjusting for potential confounders.

Results

During a follow-up period of 22 years, we identified 211 incident cases of LC. A higher zinc intake was associated with 42 % reduction in risk of LC (top tertile vs. first tertile: HR 0.58, 95 % CI 0.35; 0.94, P-for trend = 0.039). Similarly, high intake of iron was associated with reduced risk of LC (top tertile vs. first tertile: HR 0.58, 95 % CI 0.37; 0.92, P-for trend = 0.021). There was no association between dietary intake of calcium, copper, magnesium and selenium and LC risk.

Conclusions

Our results suggest that dietary zinc and iron intake are associated with reduced risk of LC. No evidence was found for an association between calcium, copper, magnesium and selenium intake and LC risk.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-016-1210-4) contains supplementary material, which is available to authorized users.

Serum Copper and Zinc Levels Among Iranian Colorectal Cancer Patients

Alterations of trace element concentrations adversely affect biological processes and could promote carcinogenesis. Only a few studies have investigated the degree of changes in copper and zinc levels in colorectal cancer (CRC). The aim of the present study was to compare the serum copper (Cu) and zinc (Zn) concentrations in patients with CRC from Iran with those of healthy subjects. Cu and Zn concentrations in the serum of 119 cancer patients and 128 healthy individuals were measured by atomic absorption spectrometry. We found a significant decrease in the total mean serum Cu and Zn concentrations in CRC patients as compared with the control group (137.5 ± 122.38 vs. 160.68 ± 45.12 μg/dl and 81.04 ± 52.05 vs. 141.64 ± 51.75, respectively). However, the serum Cu/Zn ratio in the patient group was significantly higher than that measured in the control group (p = 0.00). There was no significant difference in the mean values of serum Cu and Zn concentrations between young (<60 years) and elderly (≥60 years) patients. However, the Cu/Zn ratio in <60-year cases was significantly higher than that in ≥60-year age group (p < 0.05). In addition, mean serum Cu level in normal weight patients was significantly higher than that in overweight/obese cases (132.31 ± 87.43 vs. 103.81 ± 53.72 μg/dl, respectively) (p < 0.05). There was no difference in mean serum Cu and Zn concentrations in patients stratified by the site, stage, or differentiation grade of tumors. Our findings suggest that imbalance in Cu and Zn trace element level is associated with CRC and might play an important role in cancer development among Iranian patients.

Zinc and copper levels in bladder cancer: a systematic review and meta-analysis

It is well documented that oxidative stress is involved in the pathogenesis of bladder cancer. Zinc (Zn) and copper (Cu) are important components of antioxidants. However, the association between Zn or Cu levels and bladder cancer remains elusive. The present study was designed to investigate the alteration of serum and urinary levels of Zn or Cu in bladder cancer patients compared with controls by performing a systematic review. We searched the PubMed, Embase, and Cochrane databases from January 1990 to March 2013 to identify studies that met our predefined criteria. Six studies were included. Bladder cancer patients demonstrated significantly lower levels of serum Zn (three studies, random effects standard mean deviation (SMD): -1.072, 95 % CI: -1.489 to -0.656, P <0.0001), markedly higher levels of serum Cu (three studies, random effects SMD: 1.069, 95 % CI: 0.302 to 1.836, P = 0.006) and urinary Zn (three studies, random effects SMD: 2.114, 95 % CI: 0.328 to 3.899, P = 0.02) compared with controls. No obvious difference was observed in urinary Cu levels between bladder cancer patients and controls (two studies, random effects SMD: 0.153, 95 % CI: -0.244 to 0.55, P = 0.449). No evidence of publication bias was observed. In conclusion, the disorder of Zn and Cu is closely associated with bladder cancer. Frequent monitoring and early intervention should be recommended.

Investigating multiple candidate genes and nutrients in the folate metabolism pathway to detect genetic and nutritional risk factors for lung cancer

PURPOSE

Folate metabolism, with its importance to DNA repair, provides a promising region for genetic investigation of lung cancer risk. This project investigates genes (MTHFR, MTR, MTRR, CBS, SHMT1, TYMS), folate metabolism related nutrients (B vitamins, methionine, choline, and betaine) and their gene-nutrient interactions.

METHODS

We analyzed 115 tag single nucleotide polymorphisms (SNPs) and 15 nutrients from 1239 and 1692 non-Hispanic white, histologically-confirmed lung cancer cases and controls, respectively, using stochastic search variable selection (a Bayesian model averaging approach). Analyses were stratified by current, former, and never smoking status.

RESULTS

Rs6893114 in MTRR (odds ratio [OR] = 2.10; 95% credible interval [CI]: 1.20-3.48) and alcohol (drinkers vs. non-drinkers, OR = 0.48; 95% CI: 0.26-0.84) were associated with lung cancer risk in current smokers. Rs13170530 in MTRR (OR = 1.70; 95% CI: 1.10-2.87) and two SNP*nutrient interactions [betaine*rs2658161 (OR = 0.42; 95% CI: 0.19-0.88) and betaine*rs16948305 (OR = 0.54; 95% CI: 0.30-0.91)] were associated with lung cancer risk in former smokers. SNPs in MTRR (rs13162612; OR = 0.25; 95% CI: 0.11-0.58; rs10512948; OR = 0.61; 95% CI: 0.41-0.90; rs2924471; OR = 3.31; 95% CI: 1.66-6.59), and MTHFR (rs9651118; OR = 0.63; 95% CI: 0.43-0.95) and three SNP*nutrient interactions (choline*rs10475407; OR = 1.62; 95% CI: 1.11-2.42; choline*rs11134290; OR = 0.51; 95% CI: 0.27-0.92; and riboflavin*rs8767412; OR = 0.40; 95% CI: 0.15-0.95) were associated with lung cancer risk in never smokers.

CONCLUSIONS

This study identified possible nutrient and genetic factors related to folate metabolism associated with lung cancer risk, which could potentially lead to nutritional interventions tailored by smoking status to reduce lung cancer risk.

Mineral intake and lung cancer risk in the NIH-American Association of Retired Persons Diet and Health study

BACKGROUND

Using data from a case-control study, we previously reported that low dietary intakes of magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), but not selenium (Se) and calcium (Ca), were associated with increased lung cancer risk. Due to dietary recall bias in case-control studies, our objective was to assess whether these findings hold in a prospective cohort study.

METHODS

We analyzed data from the NIH-American Association of Retired Persons Diet and Health study of 482,875 subjects (288,257 men and 194,618 women) who were cancer-free and completed a food frequency questionnaire at enrollment between 1995 and 2003. Cox proportional hazards models were computed to estimate the relative risk adjusted for potential confounders.

RESULTS

During a mean follow-up of 7 years, 7,052 lung cancer cases were identified. For all subjects, we observed no significant associations between total (diet + supplement) Ca, Mg, Fe, Cu, Se, and Zn intakes and lung cancer risk. Total Ca intake was protective (P trend < 0.05) for current smokers and subjects with adenocarcinomas. Total Mg intake increased risk (P trend < 0.05) in men and current smokers. Total Fe intake was inversely associated with risk in women (P trend < 0.01). For dietary minerals, Mg increased risk (P trend < 0.05) in all subjects, among men and current smokers. Increased dietary Ca intake reduced risk in women (P trend = 0.05). Dietary Fe decreased risk in all subjects and among women (P trend < 0.05). Mineral intake from supplements did not affect lung cancer risk.

CONCLUSIONS

Dietary minerals are risk factors for lung cancer.

IMPACT

Dietary mineral consumption may influence lung cancer risk, but the associations differ by type of mineral and population subgroups.

Pooling dietary data using questionnaires with open-ended and predefined responses: implications for comparing mean intake or estimating odds ratios

In the current era of diet-gene analyses, large sample sizes are required to uncover the etiology of complex diseases. As such, consortia form and often combine available data. Food frequency questionnaires, which commonly use 2 different types of responses about the frequency of intake (predefined responses and open-ended responses), may be pooled to achieve the desired sample size. The common practice is to categorize open-ended responses into the predefined response categories. A problem arises when the predefined categories are noncontiguous: possible open-ended responses may fall in gaps between the predefined categories. Using simulated data modeled from frequency of intake among 1,664 controls in a lung cancer case-control study at The University of Texas M. D. Anderson Cancer Center (Houston, Texas, 2000-2005), the authors describe the effect of different categories of open-ended responses that fall in between noncontiguous, predefined response sets on estimates of the mean difference in intake and the odds ratios. A significant inflation of false positives appears when comparing mean differences of intake, while the bias in estimating odds ratios may be acceptably small. Therefore, if pooling data cannot be restricted to the same type of response, inferences should focus on odds ratio estimation to minimize bias.

Reduced DNA repair capacity for removing tobacco carcinogen-induced DNA adducts contributes to risk of head and neck cancer but not tumor characteristics

PURPOSE

Although cigarette smoking and alcohol use are known risk factors for squamous cell carcinoma of head and neck (SCCHN), only a few exposed individuals develop this disease, suggesting an individual susceptibility. In this study, we investigated the associations between genetically determined DNA repair capacity (DRC) for removing tobacco-induced DNA adducts and risk of SCCHN and tumor characteristics.

EXPERIMENTAL DESIGN

We measured DRC in cultured T lymphocytes using the host-cell reactivation assay in a hospital-based case-control study of 744 SCCHN patients and 753 age-, sex-, and ethnicity-matched cancer-free controls recruited from The University of Texas M.D. Anderson Cancer Center.

RESULTS

Patients with SCCHN had significantly lower mean DRC (8.84% +/- 2.68%) than controls (9.97% +/- 2.61%; P < 0.0001), and the difference accounted for approximately 2-fold increased risk of SCCHN [adjusted odds ratio (OR), 1.91; 95% confidence interval (CI), 1.52-2.40] after adjustment for other covariates. Compared with the highest DRC quartile of controls, this increased risk was dose dependent (second highest quartile: OR, 1.40; 95% CI, 0.99-1.98; third quartile: OR, 1.87; 95% CI, 1.34-2.62; and fourth quartile: OR, 2.76; 95% CI, 1.98-3.84, respectively; P(trend) < 0.0001). We also assessed the performance of DRC in risk prediction models by calculating the area of under the receiver operating characteristic curve. The addition of DRC to the model significantly improved the sensitivity of the expanded model. However, we did not find the association between DRC and tumor sites and stages.

CONCLUSION

DRC is an independent susceptibility biomarker for SCCHN risk but not a tumor marker.

Impact of inorganic nutrients on maintenance of genomic stability

Maintenance of genome stability is of fundamental importance for counteracting carcinogenesis. Many human genome instability syndromes exhibit a predisposition to cancer. An increasing body of epidemiological evidence has suggested a link between nutrient status and risk of cancer. Like other chemicals, nutrients can be toxic when consumed in excess. It has become clear that both nutritional deficiency and toxicity can compromise the integrity of the genome. This article focuses on roles of inorganic trace nutrients, including selenium, copper, zinc, and iron, in the redox regulation of genome stability and how they relate to the pathologies of genomic instability syndromes and cancer.

Dietary boron and hormone replacement therapy as risk factors for lung cancer in women

Hormone replacement therapy (HRT) may reduce lung cancer risk. Dietary boron may have actions similar to those of HRT; however, no previous study has reported the associations between dietary boron intake and lung cancer risk or the joint effects of boron intake and HRT use on lung cancer risk. The authors examined the associations between boron intake and the joint effects of boron intake and HRT on lung cancer risk in women. In an ongoing case-control study in Houston, Texas (July 1995 through April 2005, end date for this analysis), 763 women were diagnosed with lung cancer, and 838 were matched healthy controls with data on both diet and HRT. Multiple logistic regression analyses were conducted to assess the associations between dietary boron and HRT with lung cancer risk. After adjustment for potential confounders, the odds ratios for lung cancer with decreasing quartiles of dietary boron intake were 1.0, 1.39 (95% confidence interval (CI): 1.02, 1.90), 1.64 (95% CI: 1.20, 2.24), and 1.95 (95% CI: 1.42, 2.68) mg/day, respectively, for all women (p(trend) < 0.0001). In joint-effects analyses, compared with women with high dietary boron intake who used HRT, the odds ratio for lung cancer for low dietary boron intake and no HRT use was 2.07 (95% CI: 1.53, 2.81). Boron intake was inversely associated with lung cancer in women, whereas women who consumed low boron and did not use HRT were at substantial increased odds.