The sesquiterpene lactone eupatolide induces apoptosis in non-small cell lung cancer cells by suppressing STAT3 signaling
Introduction
Lung cancer, with a high incidence and mortality rate in China, is the most common malignant tumor in the world (Jiang et al., 2017). According to different histological behaviors and pathological manifestations, primary lung cancer is mainly divided into small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC) (Osmani et al., 2018). Among them, NSCLC accounts for about 85 % of lung cancer cases, which is a disease characterized by molecular subtypes of genetic mutations (Wang et al., 2016). Cisplatin and 5-Fluorouracil (5-FU) are the most commonly used drugs in current combination chemotherapy. With the in-depth study of the molecular mechanism of lung cancer, targeted therapy has become a hot spot in NSCLC treatment (Langhammer and Scheerer, 2017). Exploring novel tumor-associated genes and possible molecular pathways to understand their impact on the occurrence and development of lung cancer are in urgent need for finding new effective drugs.
Signal transducer and activator of transcription 3 (STAT3) is a signal transduction protein involved in a large number of cytokine and growth factor responses in cells, which is responsible for regulating several important physiological processes including cell differentiation, growth, proliferation, and apoptosis (Hillmer et al., 2016). Numerous studies have confirmed that tumor occurrence, development, and prognosis have strong correlations with STAT3 (Yu et al., 2014). Upon activation, STAT3 directly induces the expression of target factors Bcl-xL, Bcl-2, Mcl-1 and survivin, thereby blocking the process of tumor cell apoptosis. Studies have shown that Bcl-2 could inhibit the synthesis and activation of caspase-3, which participates in the cleavage of various substrates in the cell, leading to cell apoptosis. Poly ADP-ribose polymerase (PARP) is an enzyme that is located in the nucleus and is closely related to DNA repair under stress conditions. PARP cleavage is considered to be an important indicator of cell apoptosis, and is generally considered to be an indicator of caspase-3 activation.
The sesquiterpene lactone eupatolide is a novel terpenoid, which could be isolated from Inula helenium and Inula japonica (Boldbaatar et al., 2017). Currently, a variety of sesquiterpene lactones are confirmed to play several different biological functions such as anti-inflammation, anti-tumor, de-worming, anti-bacterial, and hypoglycemic and analgesic activities (Adekenov, 2017). However, current studies on eupatolide are very limited. Lee et al. reported that eupatolide sensitized human breast cancer cells to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis (Lee et al., 2010). Furthermore, eupatolide inhibits the TGF-β1-induced migration of breast cancer cells via downregulation of SMAD3 phosphorylation and transcriptional repression of ALK5 (Boldbaatar et al., 2017). These previous studies suggest that eupatolide might play a role in promoting apoptosis in tumors. Therefore, our study aimed to evaluate the role of eupatolide in NSCLC progression when treated with cisplatin or 5-FU and further explore its underlying mechanism in regulating the activation of STAT3.
Section snippets
Plasmids and reagents
The empty vector (#37,632) or constitutively active STAT3 (#24,983) were purchased from Addgene (Shanghai, China). The shNC, shSTAT3#1 and shSTAT3#2 plasmids were purchased from Sigma-Aldrich (St. Louis, MO, USA). Eupatolide was purchased from Shanghai YuanYe Biotechnology (Shanghai, China). Cisplatin and 5-FU were purchased from Selleck Chemicals (Shanghai, China). Human epidermal growth factor (EGF) was purchased from Macgene (Shanghai, China).
Cell culture
Human lung adenocarcinoma cell lines (A549, H1975
Eupatolide inhibited cell survival in NSCLC cell lines
To investigate whether eupatolide could exert anti-tumor effects in NSCLC, we first-tested the effects of eupatolide treatment at different concentrations and times on the cell survival of NSCLC cell lines. Fig. 1A showed the eupatolide chemical structure. We found that eupatolide suppressed the cell survival of A549, H460, H1299 and H1975 cells in a dose-dependent manner (Fig. 1B). As shown in Fig. 1B, the IC50 values of eupatolide in A549, H460, H1299 and H1975 were about 10 μM, 18 μM, 16 μM
Discussion
Lung cancers are the most common malignant cancer type with the highest mortality rate in the world (Brody, 2014). Among them, NSCLC accounts for 80 %–85 % of all lung cancer cases (Pastorkova et al., 2016). As a broad-spectrum anti-tumor drug, cisplatin mainly plays a role in inhibiting DNA replication of cancer cells, and has the characteristics of exact curative effect, wide anti-tumor spectrum and high anti-cancer activity (Xiao et al., 2017). In NSCLC, cisplatin is a first-line treatment
Funding
The Study was supported by the Joint construction project of Henan Province medical science and technology research plan (SB201901036); Key scientific research project plan of Henan Provincial Department of Education (19A320015).
Declaration of Competing Interest
The authors declare that they have no conflict of interest.
Acknowledgments
None.
References (30)
Sesquiterpene lactones with unusual structure. Their biogenesis and biological activity
Fitoterapia
(2017)- et al.
Two decades of research in discovery of anticancer drugs targeting STAT3, how close are we?
Pharmacol. Ther.
(2018) - et al.
The clinical relevance of the miR-197/CKS1B/STAT3-mediated PD-L1 network in chemoresistant non-small-cell lung cancer
Mol. Ther.
(2015) - et al.
STAT3 signaling in immunity
Cytokine Growth Factor Rev.
(2016) - et al.
The changing diagnostic pathway for lung cancer patients in Shanghai
China. Eur J Cancer
(2017) - et al.
Current WHO guidelines and the critical role of immunohistochemical markers in the subclassification of non-small cell lung carcinoma (NSCLC): moving from targeted therapy to immunotherapy
Semin. Cancer Biol.
(2018) - et al.
Targeting the STAT3 signaling pathway in cancer: role of synthetic and natural inhibitors
Biochim. Biophys. Acta
(2014) - et al.
Constitutive activation of STAT3 in breast cancer cells: a review
Int. J. Cancer
(2016) - et al.
Eupatolide inhibits the TGF-beta1-induced migration of breast cancer cells via downregulation of SMAD3 phosphorylation and transcriptional repression of ALK5
Oncol. Lett.
(2017) Lung cancer
Nature
(2014)
Apoptosis: a review of programmed cell death
Toxicol. Pathol.
Apoptosis-based drug screening and detection of selective toxicity to cancer cells
Anticancer Drugs
Role of chemotherapy and targeted therapy in early-stage non-small cell lung Cancer
Am. Soc. Clin. Oncol. Educ. Book
Subcellular redistribution of BAX during apoptosis induced by anticancer drugs
Anticancer Drugs
Par-4 inhibits Akt and suppresses Ras-induced lung tumorigenesis
EMBO J.
Cited by (9)
Etiology of lung carcinoma and treatment through medicinal plants, marine plants and green synthesized nanoparticles: A comprehensive review
2024, Biomedicine and PharmacotherapyLung cancer treatment potential and limits associated with the STAT family of transcription factors
2023, Cellular SignallingResearch progress on antitumor mechanisms and molecular targets of Inula sesquiterpene lactones
2023, Chinese Medicine (United Kingdom)A simple method for distinguishing Dendrobium devonianum and Dendrobium officinale by ultra performance liquid chromatography-photo diode array detector
2023, Food Science and Technology (Brazil)
- 1
These authors contributed equally to this work.