Plausible Role of Estrogens in Pathogenesis, Progression and Therapy of Lung Cancer

Hypoxia drives estrogen receptor β-mediated cell growth via transcription activation in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a highly malignant tumor with a poor prognosis. Hypoxia conditions affect multiple cellular processes promoting the adaptation and progression of cancer cells via the activation of hypoxia-inducible factors (HIF) and subsequent transcription activation of their target genes. Preliminary studies have suggested that estrogen receptor β (ERβ) might play a promoting role in the progression of NSCLC. However, the precise mechanisms, particularly its connection to HIF-1α-mediated modulation under hypoxia, remain unclear. Our findings demonstrated that the overexpression of ERβ, not ERα, increased cell proliferation and inhibition of apoptosis in NSCLC cells and xenografts. Tissue microarray staining revealed a strong correlation between the protein expression of HIF-1α and ERβ. HIF-1α induced ERβ gene transcription and protein expression in CoCl2-induced hypoxia, 1% O2 incubation, or HIF-1α overexpressing cells. ChIP identified HIF-1α binding to a hypoxia response element in the ESR2 promoter. The suppression of HIF-1α and ERβ both in vitro and in vivo effectively reduced the tumor growth, thus emphasizing the promising prospects of targeting HIF-1α and ERβ as a therapeutic approach for the treatment of NSCLC. KEY MESSAGES: ERβ, not ERα, increases cell proliferation and inhibition of apoptosis in NSCLC cells and xenografts. A strong correlation exists between the protein expression of HIF-1α and ERβ. HIF-1α induced ERβ gene transcription and protein expression in hypoxic cells via binding to HRE in the ESR2 promoter. The suppression of HIF-1α and ERβ both in vitro and in vivo effectively reduced the NSCLC tumor growth.

Analysis of Modular Hub Genes and Therapeutic Targets across Stages of Non-Small Cell Lung Cancer Transcriptome

Non-small cell lung cancer (NSCLC), representing 85% of lung cancer cases, is characterized by its heterogeneity and progression through distinct stages. This study applied Weighted Gene Co-expression Network Analysis (WGCNA) to explore the molecular mechanisms of NSCLC and identify potential therapeutic targets. Gene expression data from the GEO database were analyzed across four NSCLC stages (NSCLC1, NSCLC2, NSCLC3, and NSCLC4), with the NSCLC2 dataset selected as the reference for module preservation analysis. WGCNA identified eight highly preserved modules-Cyan, Yellow, Red, Dark Turquoise, Turquoise, White, Purple, and Royal Blue-across datasets, which were enriched in key pathways such as "Cell cycle" and "Pathways in cancer", involving processes like cell division and inflammatory responses. Hub genes, including PLK1, CDK1, and EGFR, emerged as critical regulators of tumor proliferation and immune responses. Estrogen receptor ESR1 was also highlighted, correlating with improved survival outcomes, suggesting its potential as a prognostic marker. Signature-based drug repurposing analysis identified promising therapeutic candidates, including GW-5074, which inhibits RAF and disrupts the EGFR-RAS-RAF-MEK-ERK signaling cascade, and olomoucine, a CDK1 inhibitor. Additional candidates like pinocembrin, which reduces NSCLC cell invasion by modulating epithelial-mesenchymal transition, and citalopram, an SSRI with anti-carcinogenic properties, were also identified. These findings provide valuable insights into the molecular underpinnings of NSCLC and suggest new directions for therapeutic strategies through drug repurposing.

Age at first sexual intercourse, age at menarche, and age at menopause: a mendelian randomization study on lung cancer risk

Background

There is increasing evidence that sex hormones are involved in the development of lung cancer, but the correlation between the reproductive behavior that changes sex hormone levels and lung cancer is not yet clear. Many previous studies have investigated the association between reproductive factors and lung cancer risk, but the results have been inconsistent. Therefore, we conducted a two-sample Mendelian randomization (MR) analysis to explore the potential relationship between age at first sexual intercourse (AFS), age at menarche, and age at menopause, and lung cancer.

Methods

We performed a MR analysis of the data from the genome-wide association study (GWAS) of European ancestry to evaluate the independent effects of three reproductive behaviors on lung cancer overall (LUCA), lung adenocarcinoma (LUAD), lung squamous cell carcinoma (LUSC), and small cell lung cancer (SCLC). We mainly used the inverse-variance weighting method for the MR analysis. Sensitivity was determined by a MR-pleiotropy residual sum and outlier analysis, a weighted median analysis, a MR-Egger analysis, and a leave-one-out analysis.

Results

The MR analysis results revealed that older AFS had a causal relationship with LUCA [odds ratio (OR) =0.6283, 95% confidence interval (CI): 0.4959-0.7961, P=0.0001), LUAD (OR =0.7042, 95% CI: 0.4967-0.9984, P=0.049), and LUSC (OR =0.6231, 95% CI: 0.4386-0.8853, P=0.0083).

Conclusions

Our results revealed a causal relationship between older AFS and a lower risk of lung cancer. Our findings emphasize the importance of providing sex education, as early sexual intercourse may have undesirable effects. In addition, early psychological treatment is also essential.

Long-term trends of lung cancer incidence and survival in southeastern China, 2011-2020: a population-based study

BACKGROUND

Lung cancer is the primary cause of cancer-related deaths in China. This study analysed the incidence and survival trends of lung cancer from 2011 to 2020 in Fujian Province, southeast of China, and provided basis for formulating prevention and treatment strategies.

METHODS

The population-based cancer data was used to analyse the incidence of lung cancer between 2011 and 2020, which were stratified by sex, age and histology. The change of incidence trend was analysed using Joinpoint regression. The relative survival of lung cancer with onset in 2011-2014, 2015-2017 and 2018-2020 were calculated using the cohort, complete and period methods, respectively.

RESULTS

There were 23,043 patients diagnosed with lung cancer in seven registries between 2011 and 2020, with an age-standardized incidence rate (ASIR) of 37.7/100,000. The males ASIR increased from 51.1/100,000 to 60.5/100,000 with an annual percentage change (APC) of 1.5%. However, females ASIR increased faster than males, with an APC of 5.7% in 2011-2017 and 21.0% in 2017-2020. Compared with 2011, the average onset age of males and females in 2020 was 1.5 years and 5.9 years earlier, respectively. Moreover, the proportion of adenocarcinoma has increased, while squamous cell carcinoma and small cell carcinoma have decreased over the past decade. The 5-year relative survival of lung cancer increased from 13.8 to 23.7%, with a greater average increase in females than males (8.7% and 2.6%). The 5-year relative survival of adenocarcinoma, squamous cell carcinoma and small cell carcinoma reached 47.1%, 18.3% and 6.9% in 2018-2020, respectively.

CONCLUSIONS

The incidence of lung cancer in Fujian Province is on the rise, with a significant rise in adenocarcinoma, a younger age of onset and the possibility of overdiagnosis. Thus, Fujian Province should strengthen the prevention and control of lung cancer, giving more attention to the prevention and treatment of lung cancer in females and young populations.

GPCRs and fibroblast heterogeneity in fibroblast-associated diseases

G protein-coupled receptors (GPCRs) are the largest and most diverse class of signaling receptors. GPCRs regulate many functions in the human body and have earned the title of "most targeted receptors". About one-third of the commercially available drugs for various diseases target the GPCRs. Fibroblasts lay the architectural skeleton of the body, and play a key role in supporting the growth, maintenance, and repair of almost all tissues by responding to the cellular cues via diverse and intricate GPCR signaling pathways. This review discusses the dynamic architecture of the GPCRs and their intertwined signaling in pathological conditions such as idiopathic pulmonary fibrosis, cardiac fibrosis, pancreatic fibrosis, hepatic fibrosis, and cancer as opposed to the GPCR signaling of fibroblasts in physiological conditions. Understanding the dynamics of GPCR signaling in fibroblasts with disease progression can help in the recognition of the complex interplay of different GPCR subtypes in fibroblast-mediated diseases. This review highlights the importance of designing and adaptation of next-generation strategies such as GPCR-omics, focused target identification, polypharmacology, and effective personalized medicine approaches to achieve better therapeutic outcomes for fibrosis and fibrosis associated malignancies.

The association between hormone therapy and the risk of lung cancer in postmenopausal women: a 16-year nationwide population-based study

OBJECTIVE

Although an association between hormone therapy (HT) and the risk of developing lung cancer has been reported, the results on the topic are inconsistent. Our study objective was to investigate whether postmenopausal women who undergo HT exhibit a risk of developing lung cancer.

METHODS

In this matched cohort study, we obtained the data of 38,104 postmenopausal women older than 45 years who were treated using HT between 2000 and 2015 from Taiwan's National Health Insurance Research Database, and 152,416 matched participants who were not treated using HT were enrolled as controls at a 1:4 ratio.

RESULTS

We used a Cox proportional hazards regression model to identify the risk of developing lung cancer during 16 years of follow-up, and the results indicate no significant difference in the proportion of postmenopausal women treated using HT ( P = 0.129) who developed lung cancer and that of those not treated using HT (0.866% [330 of 38,104] vs 0.950% [1,449 of 152,416]). After adjustment for age and other variables, the adjusted hazard ratio was 0.886 (95% CI, 0.666-1.305, P = 0.433), indicating no association between HT and lung cancer development in postmenopausal women. In a subgroup analysis, the risk of lung cancer was significantly lower in the women who were treated using HT when the HT cumulative dosage was ≥401 mg or when the therapy duration was ≥5 years compared with in those not treated using HT; the adjusted hazard ratios were 0.633 (95% CI, 0.475-0.930; P < 0.001) and 0.532 (95% CI, 0.330-0.934; P < 0.001), respectively, after adjustment.

CONCLUSIONS

Our results indicate that HT is not associated with the risk of lung cancer development in postmenopausal women; furthermore, a higher cumulative dosage and the long-term effects of HT reduce the risk of developing lung cancer.

Secular-Trend Analysis of the Incidence Rate of Lung Squamous Cell Carcinoma in Taiwan

Lung cancer is the leading cause of cancer deaths worldwide, and squamous cell carcinoma (SQC) is Taiwan's second most common lung carcinoma histotype. This study aimed to investigate changes in the long-term trend of the SQC incidence rate in Taiwan. SQC cases between 1985 and 2019 were adopted from Taiwan's Cancer Registry System; the age-adjusted incidence rate was calculated using the World Standard Population in 2000. The long-term trends of the age, period, and birth cohort effect of SQC incidence rates were estimated using the SEER Age-Period-Cohort Web Tool. The results revealed that the incidence of lung carcinoma in Taiwan increased, while the incidence of SQC exhibited a slight decrease during this study period. The age rate ratio (ARR) of the incidence rate in men declined gradually, and the period effect changed more slowly for women than men. The cohort effect formed a bimodal curve. The annual percentage change results for women indicated that the ARR decreased from 1.652 (95% confidence interval (CI): 1.422, 1.9192) at 30 to 34 years to 0.559 (95% CI: 0.4988, 0.6265) at 75 to 79 years; the period effect decreased from 1.2204 (95% CI: 1.1148, 1.336) in 1995 to 1999 to 0.608 (95% CI: 0.5515, 0.6704) in 2015 to 2019, with a greater decline in the later period. The cohort effect was unimodal, with the SQC risk value peaking in the 1915 birth cohort and exhibiting a steady decline thereafter. The results of this study suggest that a decrease in the smoking rate may be the reason for the decline in the incidence of SQC, and we observed a similar trend between SQC and the smoking rate in men.

Bisphenol A and Di(2-Ethylhexyl) Phthalate promote pulmonary carcinoma in female rats via estrogen receptor beta: In vivo and in silico analysis

The prevalence of lung cancer in women currently merits our attentions. However, cigarette exposure alone does not tell the whole story that lung cancer is more prevalent among non-smoking women. Since female lung cancer is closely linked to estrogen levels, many of endocrine disrupting chemicals (EDCs), as the substances similar to estrogen, affect hormone levels and become a potential risk of female lung cancer. Additionally, the combined toxicity of EDCs in daily environment has only been discussed on a limited scale. Consequently, this study explored the cancer-promoting effect of two representative substances of EDCs namely Bisphenol A (BPA) and Di(2-Ethylhexyl) Phthalate (DEHP) after their exposure alone or in combination, using a rat pulmonary tumor model published previously, combining bioinformatics analysis based on The Comparative Toxicogenomics Database (CTD) and The Cancer Genome Atlas (TCGA) databases. It demonstrated that BPA and DEHP enhanced the promotion of pulmonary tumor in female rats, either alone or in combination. Mechanistically, BPA and DEHP mainly directly bound and activated ESR2 protein, phosphorylated CREB protein, activated HDAC6 transcriptionally, induced the production of the proto-oncogene c-MYC, and accelerated the formation of pulmonary tumor in female rats. Remarkably, BPA, rather than DEHP, exhibited a much more critical effect in female lung cancer. Additionally, the transcription factor ESR2 was most affected in carcinogenesis, causing genetic disruption. Furthermore, the TCGA database revealed that ESR2 could enhance the promotion and progression of non-small cell lung cancer in females via activating the WNT/β-catenin pathway. Finally, our findings demonstrated that BPA and DEHP could enhance the promotion of pulmonary carcinoma via ESR2 in female rats and provide a potential and valuable insight into the causes and prevention of lung cancer in non-smoking women due to EDCs exposure.

Induction of 2-hydroxycatecholestrogens O-methylation: A missing puzzle piece in diagnostics and treatment of lung cancer

Lung cancer is one of the most common cancers worldwide, causing nearly one million deaths each year. Herein, we present the effect of 2-methoxyestradiol (2-ME), the endogenous metabolite of 17β-estradiol (E2), on non-small cell lung cancer (NSCLC) cells. We observed that 2-ME reduced the viability of lung adenocarcinoma in two-dimensional (2D) and three-dimensional (3D) spheroidal A549 cell culture models. Molecular modeling was carried out aiming to visualize amino acid residues within binding pockets of the acyl-protein thioesterases, namely 1 (APT1) and 2 (APT2), and thus to identify which ones were more likely involved in the interaction with 2-ME. Our findings suggest that 2-ME acts as an APT1 inhibitor enhancing protein palmitoylation and oxidative stress phenomena in the lung cancer cell. In order to support our data, metabolomics of blood serum from NSCLC patients was also performed. Moreover, computational analysis suggests that 2-ME as compared to other estrogen metabolism intermediates is relatively safe in terms of its possible non-receptor bioactivity within healthy human cells due to a very low electrophilic potential and hence no substantial risk of spontaneous covalent modification of biologically protective nucleophiles. We propose that 2-ME can be used as a selective tumor biomarker in the course of certain types of lung cancers and possibly as a therapeutic adjuvant or neoadjuvant.

Burden of lung cancer along with attributable risk factors in China from 1990 to 2019, and projections until 2030

OBJECTIVE

This study aimed to identify and project the epidemiological trends and the burden of lung cancer in China.

METHODS

We extracted incidence, mortality, disability-adjusted life-years (DALYs) and age-standardized rates of lung cancer in China, between 1990 and 2019, from the Global Burden of Disease Study (2019). The estimated annual percentage change (EAPC) was applied to quantify the trends of lung cancer burden. Furthermore, we used the Bayesian age-period-cohort model to project the incidence and mortality in the next decade.

RESULTS

From 1990 to 2019, the estimated national number of lung cancer incident cases increased by 224.0% to 832,920, deaths increased by 195.4% to 757,170 and DALYs increased by 146.1% to 17,128,580, respectively. Meanwhile, the ASIR, ASMR and ASDR showed an upward trend (EAPC of 1.33, 0.94 and 0.42, respectively). The ASIR and ASMR among males were about 2 times more than females, but the increase in ASIR in females (EAPC = 2.24) was more obvious than those in males (EAPC = 0.10) from 2020 to 2030. In China, smoking remained responsible for the highest burden of lung cancer, but the contribution of ambient particulate matter pollution to DALYs increased from 10.6% in 1990 to 22.5% in 2019 in total population. Moreover, we predicted that the number of deaths from lung cancer will increase by 42.7% in China by 2030.

CONCLUSION

In China, the burden of lung cancer has been increasing over the past three decades, which highlights more targeted intervention measures are needed to reduce the burden of lung cancer.

Loss of Frizzled 9 in Lung Cells Alters Epithelial Phenotype and Promotes Premalignant Lesion Development

The transmembrane receptor Frizzled 9 (FZD9) is important for fetal neurologic and bone development through both canonical and non-canonical WNT/FZD signaling. In the adult lung, however, Fzd9 helps to maintain a normal epithelium by signaling through peroxisome proliferator activated receptor γ (PPARγ). The effect of FZD9 loss on normal lung epithelial cells and regulators of its expression in the lung are unknown. We knocked down FZD9 in human bronchial epithelial cell (HBEC) lines and found that downstream EMT targets and PPARγ activity are altered. We used a FZD9-/- mouse in the urethane lung adenocarcinoma model and found FZD9-/- adenomas had more proliferation, increased EMT signaling, decreased activation of PPARγ, increased expression of lung cancer associated genes, increased transformed growth, and increased potential for invasive behavior. We identified PPARγ as a transcriptional regulator of FZD9. We also demonstrated that extended cigarette smoke exposure in HBEC leads to decreased FZD9 expression, decreased activation of PPARγ, and increased transformed growth, and found that higher exposure to cigarette smoke in human lungs leads to decreased FZD9 expression. These results provide evidence for the role of FZD9 in lung epithelial maintenance and in smoking related malignant transformation. We identified the first transcriptional regulator of FZD9 in the lung and found FZD9 negative lesions are more dangerous. Loss of FZD9 creates a permissive environment for development of premalignant lung lesions, making it a potential target for intervention.

Management of menopause: a view towards prevention

Women spend approximately one-third of their lives with menopause, which occurs around 50 years of age. It is now appreciated that several important metabolic and cardiovascular disease risks emerge during the menopausal transition. Many important conditions occur 10-15 years after menopause, including weight gain and obesity, metabolic syndrome, diabetes, osteoporosis, arthritis, cardiovascular disease, dementia, and cancer; therefore, the occurrence of menopause heralds an important opportunity to institute preventative strategies. These strategies will lead to improved quality of life and decreased mortality. Various strategies are presented for treating symptoms of menopause and diseases that are asymptomatic. Among several strategies is the use of hormone therapy, which has efficacy for symptoms and osteoporosis, and can improve metabolic and cardiovascular health. When instituted early, which is key, in younger postmenopausal women (under 60 years) oestrogen has been found to consistently decrease mortality with a favourable risk-benefit profile in low-risk women. Prospective data show that long-term therapy might not be required for this benefit.

Application of two-dimensional difference gel electrophoresis to identify protein changes between center, margin, and adjacent non-tumor tissues obtained from non-small-cell lung cancer with adenocarcinoma or squamous cell carcinoma subtype

Lung cancer is responsible for the most cancer-related mortality worldwide and the mechanism of its development is poorly understood. Proteomics has become a powerful tool offering vital knowledge related to cancer development. Using a two-dimensional difference gel electrophoresis (2D-DIGE) approach, we sought to compare tissue samples from non-small-cell lung cancer (NSCLC) patients taken from the tumor center and tumor margin. Two subtypes of NSCLC, adenocarcinoma (ADC) and squamous cell carcinoma (SCC) were compared. Data are available via ProteomeXchange with identifier PXD032736 and PXD032962 for ADC and SCC, respectively. For ADC proteins, 26 significant canonical pathways were identified, including Rho signaling pathways, a semaphorin neuronal repulsive signaling pathway, and epithelial adherens junction signaling. For SCC proteins, nine significant canonical pathways were identified, including hypoxia-inducible factor-1α signaling, thyroid hormone biosynthesis, and phagosome maturation. Proteins differentiating the tumor center and tumor margin were linked to cancer invasion and progression, including cell migration, adhesion and invasion, cytoskeletal structure, protein folding, anaerobic metabolism, tumor angiogenesis, EMC transition, epithelial adherens junctions, and inflammatory responses. In conclusion, we identified several proteins that are important for the better characterization of tumor development and molecular specificity of both lung cancer subtypes. We also identified proteins that may be important as biomarkers and/or targets for anticancer therapy.

Estrogens, Cancer and Immunity

Sex hormones are included in many physiological and pathological pathways. Estrogens belong to steroid hormones active in female sex. Estradiol (E2) is the strongest female sex hormone and, with its receptors, contributes to oncogenesis, cancer progression and response to treatment. In recent years, a role of immunosurveillance and suppression of immune response in malignancy has been well defined, forming the basis for cancer immunotherapy. The interplay of sex hormones with cancer immunity, as well as the response to immune checkpoint inhibitors, is of interest. In this review, we investigate the impact of sex hormones on natural immune response with respect to main active elements in anticancer immune surveillance: dendritic cells, macrophages, lymphocytes and checkpoint molecules. We describe the main sex-dependent tumors and the contribution of estrogen in their progression, response to treatment and especially modulation of anticancer immune response.

CircCAMSAP1 promotes non-small cell lung cancer proliferation and inhibits cell apoptosis by sponging miR-1182 and regulating BIRC5

Recently, various studies have suggested that circular RNAs (circRNAs) are ubiquitous in various malignant events, including non-small cell lung cancer (NSCLC) and are closely related to cell proliferation and apoptosis. Unfortunately, the molecular functions involved in this action still have little overlap. Therefore, this study aimed to identify a novel circCAMSAP1 role in NSCLC. Overexpression of circCAMSAP1 has been demonstrated in NSCLC lung tissues and cell lines. Sequencing and RNase R experiments were planned to determine whether circCAMSAP1 is looped and exists in NSCLC. We also found that downregulated circCAMSAP1 repressed cell proliferation and increased apoptosis of NSCLC cells in vitro and suppressed xenograft tumor growth in vivo. Furthermore, a luciferase assay revealed that circCAMSAP1 could regulate baculoviral inhibitor of apoptosis protein (IAP) repeat containing 5 (BIRC5, also known as survivin) expression by directly binding to miR-1182. However, BIRC5 without 3ʹ untranslated regions (3ʹUTR) could reverse the influence of downregulated circCAMSAP1 on proliferation and apoptosis in NSCLC. Together, our findings reveal a novel mechanism by which the circCAMSAP1/miR-1182/BIRC5 axis promotes NSCLC progression.

Targeting Estrogens and Various Estrogen-Related Receptors against Non-Small Cell Lung Cancers: A Perspective

Non-small cell lung cancers (NSCLCs) account for ~85% of lung cancer cases worldwide. Mammalian lungs are exposed to both endogenous and exogenous estrogens. The expression of estrogen receptors (ERs) in lung cancer cells has evoked the necessity to evaluate the role of estrogens in the disease progression. Estrogens, specifically 17β-estradiol, promote maturation of several tissue types including lungs. Recent epidemiologic data indicate that women have a higher risk of lung adenocarcinoma, a type of NSCLC, when compared to men, independent of smoking status. Besides ERs, pulmonary tissues both in healthy physiology and in NSCLCs also express G-protein-coupled ERs (GPERs), epidermal growth factor receptor (EGFRs), estrogen-related receptors (ERRs) and orphan nuclear receptors. Premenopausal females between the ages of 15 and 50 years synthesize a large contingent of estrogens and are at a greater risk of developing NSCLCs. Estrogen-ER/GPER/EGFR/ERR-mediated activation of various cell signaling molecules regulates NSCLC cell proliferation, survival and apoptosis. This article sheds light on the most recent achievements in the elucidation of sequential biochemical events in estrogen-activated cell signaling pathways involved in NSCLC severity with insight into the mechanism of regulation by ERs/GPERs/EGFRs/ERRs. It further discusses the success of anti-estrogen therapies against NSCLCs.

Role of sex hormones in lung cancer

Lung cancer represents the world's leading cause of cancer deaths. Sex differences in the incidence and mortality rates for various types of lung cancers have been identified, but the biological and endocrine mechanisms implicated in these disparities have not yet been determined. While some cancers such as lung adenocarcinoma are more commonly found among women than men, others like squamous cell carcinoma display the opposite pattern or show no sex differences. Associations of tobacco product use rates, susceptibility to carcinogens, occupational exposures, and indoor and outdoor air pollution have also been linked to differential rates of lung cancer occurrence and mortality between sexes. While roles for sex hormones in other types of cancers affecting women or men have been identified and described, little is known about the influence of sex hormones in lung cancer. One potential mechanism identified to date is the synergism between estrogen and some tobacco compounds, and oncogene mutations, in inducing the expression of metabolic enzymes, leading to enhanced formation of reactive oxygen species and DNA adducts, and subsequent lung carcinogenesis. In this review, we present the literature available regarding sex differences in cancer rates, associations of male and female sex hormones with lung cancer, the influence of exogenous hormone therapy in women, and potential mechanisms mediated by male and female sex hormone receptors in lung carcinogenesis. The influence of biological sex on lung disease has recently been established, thus new research incorporating this variable will shed light on the mechanisms behind the observed disparities in lung cancer rates, and potentially lead to the development of new therapeutics to treat this devastating disease.

Age at first birth and lung cancer: a two-sample Mendelian randomization study

Background

Growing evidence suggests that female reproductive factors, like age at first birth (AFB), may play a potential role in the progression of lung cancer (LC). However, previous studies are susceptible to confounding factors, inadequate attention to variation by histology or reverse causality. Few studies have comprehensively evaluated their association and the causal effect remains unclear.

Methods

We aimed to determine whether AFB is causally correlated with the risk of LC, by means of utilizing aggregated data from the large genome-wide association studies conducted on AFB (251,151 individuals) and data of LC from International Lung and Cancer Consortium (ILCCO, 11,348 cases and 15,861 controls). We used 10 AFB-related single nucleotide polymorphisms as instrument variables and applied several two-sample Mendelian randomization (MR) methods. Secondary results according to different histological subtypes of lung cancer were also implemented.

Results

Conventional inverse-variance weighted method indicated that genetic predisposition towards number unit (1 year) increase of AFB was associated with a 18% lower risk of LC [odds ratio (OR) =0.82, 95% confidence interval (CI): 0.69–0.97; P=0.029]. When results were examined by histotypes, an inverse association was observed between genetically predisposed number unit (1 year) increase of AFB and lung adenocarcinoma (OR =0.75, 95% CI: 0.59–0.97, P=0.017) but not with squamous cell lung cancer (OR =0.77, 95% CI: 0.57–1.05, P=0.103). The results demonstrated no association between number unit decrease of AFB and LC. Pleiotropy was not presented through sensitivity analyses including MR pleiotropy residual sum and outlier test (P=0.412). Genetic predisposition towards older AFB was additionally associated with longer years of schooling (OR =1.12, 95% CI: 1.08–1.16, P<0.001), lower body mass index (OR =0.93, 95% CI: 0.88–0.98, P=0.004) and less alcohol consumption (OR =0.99, 95% CI: 0.99–1.00, P=0.004).

Conclusions

Our study suggested that older AFB was a causal protective factor in the progression of LC. Further studies elucidating the potential mechanisms are needed.