Estrogen promotes benzo[a]pyrene-induced lung carcinogenesis through oxidative stress damage and cytochrome c-mediated caspase-3 activation pathways in female mice
Highlights
► Estrogen may contribute to the development of smoking-induced lung cancer in women. ► We examine the effects of estradiol on benzo[a]pyrene-induced lung carcinogenesis. ► B[a]P cause oxidative stress, upregulate Cyt-c and caspase-3, induce lung cancer. ► E2 promote these tumorigenic effects of B[a]P in female mice. ► Activation of Cyt-c-mediated caspase-3 pathway may be involved in this process.
Introduction
Lung cancer is the leading cause of cancer death worldwide, especially in the United States [1], [2], Europe [3], and China [4]. Presently, lung cancer accounts for more deaths in women than any other cancer, and this number is more than the combined number of the second and third most fatal cancers in women (breast and colon cancer, respectively [5]. It is a well-established fact that cigarette smoking is the principal cause of lung cancer in both men and women. The majority of studies in the past have reported that the risk of lung cancer is higher in male smokers than that in female smokers [6], [7]. However, several recent studies have indicated that the absolute risk for lung cancer is higher for women than for men [8], [9], [10], [11]. Recently, the International Early Lung Cancer Action Program Investigators reported that women who smoke are at a high risk of lung cancer than men of the same age who smoke the same number of cigarettes [5]. This is the first prospective cohort study in which such a gender difference has been observed. In our recent experiments, we found a similar result that gender differences may influence the occurrence of smoke-induced lung tumors and antioxidant intervention in mice [12]. We hypothesized that hormonal factors could provide a possible explanation for these gender-based differences in lung cancer. Some data confirmed this hypothesis from the results of epidemiological investigations [10], [11], [13], [14], [15], [16] and cell lines experiments [17]. However, to date, there is no in vivo direct evidence to support this hypothesis.
Benzo[a]pyrene (B[a]P) is one of the main carcinogens in cigarette smoke, and also a known human carcinogen [18]. Because of the carcinogenic effects of B[a]P, it has been utilized as a tool reagent to induce lung tumorigenesis in the evaluation of in vivo carcinogenic assay systems [19], [20], [21]. Estrogen is one of the vital hormones that regulate lung development [22]. Several reports of sex differences in lung cancer risk and disease presentation suggest that use of hormone-replacement therapy (HRT) was associated with a higher risk of adenocarcinoma of the lung compared with never use, and a positive interaction was noted between HRT, smoking, and adenocarcinoma of the lung [23], and estrogen may be involved in the etiology of lung cancer, particularly adenocarcinoma in women [24]. Additionally, 17-beta-estradiol acts as a mitogen for NSCLC cells in vitro and in vivo [13] and can modulate the expression of genes in NSCLC cell lines that are important for control of cell proliferation [25]. The drug tamoxifen (TAM) is the most widely used drug for the treatment of estrogen receptor (ER)-positive breast cancer, and exerts its antiestrogenic effect both by displacing the growth-promoting natural hormone estradiol-17beta from its receptor [26] and by blocking the stimulatory effects of IL-6 on 17beta-OH steroid dehydrogenase [27]. TAM works by competitively blocking the binding of estrogens to the ER, which leads to inhibition of estrogen-responsive genes such as those responsible for growth and angiogenesis within the tumor [28].
In the present study, we comprehensively evaluated the role of 17 beta-estradiol (E2) in promoting the genesis of lung cancer induced by benzo[a]pyrene (B[a]P) in female mice, and investigated the effects of E2 on B[a]P induced oxidative stress damage and cytochrome c-mediated activation of caspase-3 pathways.
Section snippets
Chemicals
Estrogen [17 beta-estradiol (E2)], B[a]P, tamoxifen (TAM), and olive oil were all purchased from Sigma–Aldrich company (USA).
Animals
Healthy 5-week-old female Swiss mice (Kunming mice; weight, 18 ± 2 g) were purchased from Center of Animal, Academy of Military Medical Sciences, Beijing, China. The mice did not show any signs of infectious disease (pathogenic agents). They were housed in polypropylene cages with tight-fitting wire screen lids made of conventional bedding materials. The mice were monitored
Changes of mice body weights and survival rate curves of the mice during the experiment
All animals showed good tolerance to E2, TAM, and B[a]P exposure. There was no death due to experimental factors throughout the study. Overall, body weight was the lowest in the B[a]P + TAM + E2 group, and this weight was significantly lower than that in the control group (P < 0.05). The body weights of mice in other groups did not differ significantly, but the body weight of the B[a]P-exposed mice was lower than that of the mice in other groups (P > 0.05) (Supplementary materials, S-Figure 1). Only a
Discussion
In this study, we developed an animal model to evaluate the role of E2 in the development and growth of lung cancer induced by B[a]P, which was one of the main carcinogens in cigarette smoke [32], [33]. In the present study, we found that E2, by itself, did not induce lung tumor. However, E2 promoted B[a]P that in turn induced lung cancer in female mice; TAM inhibited the effects of E2 that promoted B[a]P-induced carcinogenesis. These findings indicated that estrogen might be a carcinoma
Financial disclosure
This research received no external funding.
Conflict of interest
The authors have declared that no competing interests exist.
Acknowledgments
We thank Jian Tao and Yufei Zheng for their assistance in performing some experiments. We also thank Zhuge Xi, Qiang Ma, Jinpeng Guo, Zuguo Zhao, Xiaoying Zhang, Danfeng Yang, Jing Yin for reagents and experimental assistance.
References (68)
- et al.
A prospective study of a total material of lung cancer from a county in Sweden 1997–1999: gender, symptoms, type, stage, and smoking habits
Lung Cancer
(2002) - et al.
The critical DNA damage by benzo(a)pyrene in lung tissues of smokers and approaches to preventing its formation
Toxicol. Lett.
(2010) - et al.
Dose-response study of myo-inositol as an inhibitor of lung tumorigenesis induced in A/J mice by benzo[a]pyrene and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone
Cancer Lett.
(2001) - et al.
In vivo effect of piperine on serum and tissue glycoprotein levels in benzo(a)pyrene induced lung carcinogenesis in Swiss albino mice
Pulm. Pharmacol. Ther.
(2006) - et al.
Lack of contribution of covalent benzo[a]pyrene-7,8-quinone-DNA adducts in benzo[a]pyrene-induced mouse lung tumorigenesis
Chem. Biol. Interact.
(2010) - et al.
It’s all about sex: gender, lung development and lung disease
Trends Endocrinol. Metab.
(2007) - et al.
Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method
Methods
(2001) - et al.
Promotive effect of diethylstilbestrol on urethan-induced mouse lung tumorigenesis
Chemosphere
(2000) - et al.
Gender-related differences in susceptibility of A/J mouse to benzo[a]pyrene-induced pulmonary and forestomach tumorigenesis
Cancer Lett.
(1998) - et al.
Oxidative stress to DNA, protein, and antioxidant enzymes (superoxide dismutase and catalase) in rats treated with benzo(a)pyrene
Cancer Lett.
(1997)
Direct antioxidant and protective effect of estradiol on isolated mitochondria
Biochim. Biophys. Acta
Inhibition of benzopyrene-diol-epoxide (BPDE)-induced bax and caspase-9 by cadmium: role of mitogen activated protein kinase
Mutat. Res.
Cytochrome c and dATP-dependent formation of Apaf-1/caspase-9 complex initiates an apoptotic protease cascade
Cell
Crotonaldehyde induces oxidative stress and caspase-dependent apoptosis in human bronchial epithelial cells
Toxicol. Lett.
Benzo(a)pyrene-induced apoptotic death of mouse hepatoma Hepa1c1c7 cells via activation of intrinsic caspase cascade and mitochondrial dysfunction
Toxicology
Activation of a caspase-dependent oxidative damage response mediates TGFbeta1 apoptosis in rat hepatocytes
Exp. Mol. Pathol.
Oxidative stress and apoptosis in metal ion-induced carcinogenesis
Free Radic. Biol. Med.
Environmental toxicity, oxidative stress and apoptosis: ménage à trois
Mutat. Res.
Coordination of ER and oxidative stress signaling: the PERK/Nrf2 signaling pathway
Int. J. Biochem. Cell Biol.
8-Hydroxyguanine, an abundant form of oxidative DNA damage, causes G–T and A–C substitutions
J. Biol. Chem.
Oxidative stress, inflammation, and cancer: how are they linked?
Free Radic. Biol. Med.
Catechin prevents tamoxifen-induced oxidative stress and biochemical perturbations in mice
Toxicology
Annual report to the nation on the status of cancer, 1975–2002. Featuring population-based trends in cancer treatment
J. Natl. Cancer Inst.
Cancer statistics, 2006. CA.
Cancer J. Clin.
Mortality time trends and the incidence and mortality estimation and projection for lung cancer in China
Zhongguo Fei Ai Za Zhi
Women’s susceptibility to tobacco carcinogens and survival after diagnosis of lung cancer
JAMA
The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today
J. Natl. Cancer Inst.
Smoking in relation to the death rates of one million men and women
Natl. Cancer Inst. Monogr.
Differences in lung cancer risk between men and women: examination of the evidence
J. Natl. Cancer Inst.
Lung cancer mortality trends in 36 European countries: secular trends and birth cohort patterns by sex and region 1970–2007
Int. J. Cancer
Gender differences in lung cancer risk by smoking: a multicentre case-control study in Germany and Italy
Brit. J. Cancer
Tobacco use and cancer: an epidemiologic perspective for geneticists
Oncogene
Antioxidant intervention of smoking-induced lung tumor in mice by vitamin E and quercetin
BMC Cancer
Hormonal factors and risk of lung cancer among women?
Int. J. Epidemiol.
Cited by (38)
The smoking estrogens – a potential synergy between estradiol and benzo(a)pyrene
2021, Biomedicine and PharmacotherapyCitation Excerpt :It is also worth noting that catechol derivatives can be oxidized intracellularly by any oxidizing enzyme. This synthesis results in the production of strongly electrophilic quinones and semiquinones, which can further metabolize to form reactive oxygen species (ROS), including the free hydroxyl radical, the most reactive ROS, considered as the most harmful oxidizing agent [8,77–80]. The presence of these molecules inside the cell can lead to organelle and protein damage, as well as DNA oxidation followed by the formation of adducts, especially 8-OH-deoxyguanosine, the most frequently occurring DNA damage [77,81,82].
PM2.5 organic extract mediates inflammation through the ERβ pathway to contribute to lung carcinogenesis in vitro and vivo
2021, ChemosphereCitation Excerpt :Consistently, in vitro research has shown that estrogen stimulates NSCLC cells proliferation through ER-mediated signaling (Hershberger et al., 2005; Tang et al., 2014). Some studies have confirmed that ER not only promotes the malignant transformation of target organs such as breast and uterus, but also has significant effects on nontarget organs such as lung (Niikawa et al., 2008; Chen et al., 2011). Furthermore, ERs play an important role in the development of lung cancer (Stabile et al., 2002), and ERβ, a kind of ER subtype, is involved in the occurrence and development of NSCLC (Marquez-Garban et al., 2007).
Protective effect of hawthorn extract against genotoxicity induced by benzo(<alpha>)pyrene in C57BL/6 mice
2020, Ecotoxicology and Environmental SafetyCitation Excerpt :Current studies have confirmed that exposure to high levels of environmental B(<alpha>)P was associated with elevated rates of cancer (Zhu et al., 2019). Animal experiments revealed that B(<alpha>)P can cause advanced fibrosis in liver specimens, tumor nodules in lung and reduction of spleen cells (Chen et al., 2011). Encouragingly, radioprotective and cardioprotective effect of HE has been found (Hosseinimehr et al., 2007; Swaminathan et al., 2010), and several studies have shown protective effects of HE against atherosclerosis and hypertension (Zhang et al., 2014; Zheng et al., 2019), which indicated that HE may act as a natural protective agent resist to environmental toxic exposure.
Immunization against environmental chemical carcinogens: Pro and contra
2019, Medical HypothesesImmunomodulation of carcinogens-induced steroids-dependent human diseases
2019, Saudi Journal of Biological SciencesCitation Excerpt :Another Cg, heterocyclic amines, bind to the ER and activate or inhibit estrogenic response in human cells (Bennion et al., 2005). On the other hand, estrogens promote Bp-induced carcinogenesis (Chen et al., 2011; Lin et al., 2012) and act as a mitogens for cell in vitro and in vivo (Kreuzer et al., 2003). One of the possible ways of interaction between exogenous Cg and S is induction of steroid receptors mutation as it was revealed for ER mutation in breast cancer (Toy et al., 2013; Alluri et al., 2014).
Bioactivity-guided isolation of β-Carboline alkaloids with potential anti-hepatoma effect from Picrasma quassioides (D. Don) Benn
2018, FitoterapiaCitation Excerpt :The results supported the SAR discovered in MTT assay, and revealed that compounds 12, 29 and 36 mediated their activity toward HepG2 cells probably through cell apoptosis induction. Caspase-3 is an essential apoptotic enzyme that mediates the cleavage of apoptosis-related proteins and the degradation of chromosomal DNA [27]. In Fig. 6, caspase-3 activities in the groups treated with 12, 29 and 36 were 2.67-, 2.64-, and 1.87- fold higher than those in the control group.
- 1
These authors contributed equally to this work and are considered co-first authors.