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α-Lipoic acid inhibits human lung cancer cell proliferation through Grb2-mediated EGFR downregulation
Lan Yang1, Ya Wen2, Guoqing Lv3
1Shenzhen Tumor Immuno-gene Therapy Clinical Application Engineering Lab, Biobank of Shenzhen Second People's Hospital, The First Affiliated Hospital of Shenzhen University, Shenzhen 518035, PR China; Institute of Immunology of Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510060, Guangdong, PR China.
Background:
Alpha lipoic acid (α -LA) is a naturally occurring antioxidant and metabolic enzyme co-factor. Recently, α -LA has been reported to inhibit the growth of various cancer cells, but the precise signaling pathways that mediate the effects of α -LA on non-small cell lung cancer (NSCLC) development remain unclear.
Methods:
The CCK-8 assay was used to assess cell proliferation in NSCLC cell lines after α -LA treatment. The expression of growth factor receptor-bound protein 2 (Grb2), cyclin-dependent kinase (CDK)-2, CDK4, CDK6, Cyclin D3, Cyclin E1, Ras, c-Raf, epidermal growth factor receptor (EGFR), ERK1/2 and activated EGFR and ERK1/2 was evaluated by western blotting. Grb2 levels were restored in α-LA-treated cells by transfection of a plasmid carrying Grb2 and were reduced in NSCLC cells via specific siRNA-mediated knockdown.
Results:
α -LA dramatically decreased NSCLC cell proliferation by downregulating Grb2; in contrast, Grb2 overexpression significantly prevented α-LA-induced decrease in cell growth in vitro. Western blot analysis indicated that α-LA decreased the levels of phospho-EGFR, CDK2/4/6, Cyclins D3 and E1, which are associated with the inhibition of G1/S-phase transition. Additional experiments indicated that Grb2 inhibition partially abolished EGF-induced phospho-EGFR and phospho-ERK1/2 activity. In addition, α-LA exerted greater inhibitory effects than gefitinib on NSCLC cells by preventing EGF-induced EGFR activation.
Conclusion:
For the first time, these findings provide the first evidence that α-LA inhibits cell proliferation through Grb2 by suppressing EGFR phosphorylation and that MAPK/ERK is involved in this pathway.
Insights
Alpha lipoic acid (α-LA) inhibits non-small cell lung cancer (NSCLC) cell growth by downregulating Grb2. This antioxidant suppresses EGFR phosphorylation and involves the MAPK/ERK pathway, offering a potential therapeutic strategy for NSCLC.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Alpha lipoic acid (α-LA) is a natural antioxidant with potential anti-cancer properties.
- The precise mechanisms by which α-LA affects non-small cell lung cancer (NSCLC) remain largely unknown.
- Understanding these pathways is crucial for developing novel NSCLC therapies.
Purpose of the Study:
- To elucidate the signaling pathways involved in α-LA's inhibitory effects on NSCLC.
- To investigate the role of growth factor receptor-bound protein 2 (Grb2) in α-LA-mediated NSCLC growth inhibition.
- To explore the involvement of the epidermal growth factor receptor (EGFR) and MAPK/ERK pathways.
Main Methods:
- Cell proliferation was assessed using the CCK-8 assay in NSCLC cell lines.
- Protein expression levels of key signaling molecules (Grb2, CDKs, Cyclins, EGFR, ERK1/2) were analyzed via western blotting.
- Gene manipulation techniques, including Grb2 overexpression and siRNA knockdown, were employed.
Main Results:
- α-LA significantly reduced NSCLC cell proliferation, primarily by downregulating Grb2.
- Overexpression of Grb2 counteracted the anti-proliferative effects of α-LA.
- α-LA decreased the phosphorylation of EGFR and ERK1/2, inhibiting G1/S-phase transition and showing greater efficacy than gefitinib.
Conclusions:
- α-LA inhibits NSCLC cell proliferation by suppressing EGFR phosphorylation through a Grb2-dependent mechanism.
- The MAPK/ERK pathway is implicated in the anti-cancer effects of α-LA in NSCLC.
- These findings highlight α-LA as a potential therapeutic agent for NSCLC, targeting the Grb2/EGFR/ERK pathway.