Cigarette smoke extract reduces FOXO3a promoting tumor progression and cell migration in lung cancer
Serena Di Vincenzo1, Claudia Sangiorgi1, Maria Ferraro1
1Institute for Biomedical Research and Innovation (IRIB), National Research Council of Italy (CNR), Palermo, Italy.
Abstract:
Lung cancer is the leading cause of cancer death worldwide, and the carcinogens in tobacco smoke play a role in its progression and metastasis. The related molecular events are largely unknown. FOXO3a is a transcription factor considered a tumor suppressor. Its inhibition leads to cell transformation, tumor progression and metastasis. The aim of this study was to investigate, in different types of lung cancer cell lines (A549, COLO 699 N, SK-MES-1), the effects of cigarette smoke on mitochondrial status and cell metabolism and on key pathways involved in tumor progression and cell migration, looking at the role of FOXO3a in these mechanisms. The different lung cancer cells were exposed to cigarette smoke extract (CSE) and TGF-β1. Reactive oxygen species (ROS), mitochondrial superoxide, intracellular ATP, extracellular lactate, FOXO3a, p21, survivin, epithelial-to-mesenchymal transition (EMT) markers (E-cadherin, SNAIL1), MMP-9 and cellular migration were assessed by flow-cytometry, fluorimetry, western blot analysis, Real-Time PCR and scratch test. Our results showed that exposure to CSE: (i) increased ROS, mitochondrial superoxide, lactate release while reducing intracellular ATP; (ii) decreased FOXO3a and increased survivin and p21 in the cytoplasm; (iii) decreased E-cadherin, increased SNAIL1 and MMP-9 and promoted cell migration like TGF-β1 did. These effects could be partly explained by downregulation of FOXO3a, as demonstrated by silencing experiments. These data suggest that cigarette smoke induces oxidative stress and mitochondrial damage leading to metabolic reprogramming associated with increased glycolytic flux. This is accompanied with a downregulation of FOXO3a contributing to EMT processes and cell migration therefore promoting tumor progression.
Insights
Cigarette smoke harms lung cancer cells by increasing oxidative stress and damaging mitochondria, leading to tumor progression and metastasis. This occurs partly due to reduced levels of the tumor suppressor FOXO3a.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Lung cancer is a leading cause of cancer death globally.
- Carcinogens in tobacco smoke contribute to lung cancer progression and metastasis.
- Molecular mechanisms underlying these effects are not fully understood.
Purpose of the Study:
- To investigate the impact of cigarette smoke on lung cancer cell metabolism and mitochondrial function.
- To examine the role of the transcription factor FOXO3a in cigarette smoke-induced tumor progression and cell migration.
- To analyze key molecular pathways, including epithelial-to-mesenchymal transition (EMT), affected by cigarette smoke.
Main Methods:
- Exposure of lung cancer cell lines (A549, COLO 699 N, SK-MES-1) to cigarette smoke extract (CSE) and TGF-β1.
- Assessment of reactive oxygen species (ROS), mitochondrial superoxide, ATP, lactate, FOXO3a, p21, survivin, EMT markers (E-cadherin, SNAIL1), MMP-9, and cell migration.
- Utilized techniques: flow cytometry, fluorimetry, western blot, Real-Time PCR, and scratch test.
Main Results:
- CSE exposure increased ROS, mitochondrial superoxide, and lactate release, while decreasing intracellular ATP.
- CSE reduced FOXO3a levels and increased survivin and p21 in the cytoplasm.
- CSE induced EMT markers (decreased E-cadherin, increased SNAIL1, MMP-9) and promoted cell migration, similar to TGF-β1 effects.
Conclusions:
- Cigarette smoke induces oxidative stress and mitochondrial damage, leading to metabolic reprogramming and increased glycolysis.
- Downregulation of the tumor suppressor FOXO3a by cigarette smoke contributes to EMT and enhanced cell migration.
- These molecular events promoted by cigarette smoke drive lung cancer progression and metastasis.
