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MO04 - Lung Cancer Biology I (ID 86)
- Event: WCLC 2013
- Type: Mini Oral Abstract Session
- Track: Biology
- Presentations: 1
MO04.01 - Molecular mechanisms of cigarette smoke induced hyper-proliferation of human lung cells and its prevention. (ID 2636)
16:15 - 17:45 | Author(s): I.B. Chatterjee
Lung cancer is the leading cause of cancer-deaths throughout the World. Cigarette smoke (CS) is the strongest risk factor of lung cancer. Cigarette smoking and exposure to environmental tobacco smoke account for 90% of lung cancer cases, and smokers have a 20-fold increased risk of death from lung cancer compared to non-smokers. Unregulated cell proliferation together with suppressed apoptosis is a contributory factor for lung-carcinogenesis. However, the carcinogenic mechanism of cigarette smoking is not well understood. This is particularly because CS is a complex mixture of about 4000 compounds. We consider that identifying the risk factor(s) in CS and its prevention might be a novel way to prevent lung cancer.
Cytotoxicity was evaluated by the MTT assay. Cell cycle analysis was performed by propidium iodide (PI) staining followed by flow-cytometry. Apoptosis was assessed by AnnexinV- PI staining followed by flow-cytometry, phosphorylation of p53 and activation (cleavage) of caspase 3. Reactive Oxygen Species (ROS) production was detected by 2’, 7’-dichlorodihydrofluorescein diacetate (H~2~DCFDA) using confocal microscope. Cell proliferation was assessed using “In Situ Cell Proliferation Kit, FLUOS” (Roche Applied Science, Germany). DNA double-strand break was detected using “OxiSelect DNA Double Strand Break (DSB) Staining Kit” (CELL BIOLABS, INC.).
We have identified p-benzoquinone (p-BQ) as a major risk factor that is derived from CS. p-BQ has a biphasic-nature as evidenced by MTT assay, AnnexinV-PI staining, cell cycle analysis and BrdU-incorporation assay. Low concentrations of p-BQ mimicked CS-induced proliferation of cultured lung adenocarcinoma cells (A549) as well as normal human primary small airway cells (ATCC[®] PCS-301-010[™]). On the contrary, high concentrations of CS/p-BQ resulted in cell death caused by oxidative stress and apoptosis. No such cell death was observed with low concentrations of CS/p-BQ. Coimmunoprecipitation and immunoblot experiments indicated that p-BQ-induced proliferation was mediated via aberrant phosphorylation of EGFR that lacked c-Cbl mediated ubiquitination and degradation. This resulted in prolonged EGFR signaling leading to persistent activation of Ras (a potent oncoprotein), the downstream survival and proliferative signaling molecules Akt and ERK1/2, as well as the transcription factors c-Myc and c-Fos. It is known that patients with lung cancer generally have a smoking history of more than 30-40 years. We therefore exposed A549 cells repeatedly to CS/p-BQ for 2 months. Repeated exposure of AECS/p-BQ generated high levels of DNA double-strand breaks in A549 cells that might lead to genomic instability as well as mutation of different proto-oncogenes and tumor suppressor genes – the hallmark events in cancer. In addition, CS/p-BQ altered the acetylation pattern of different histone epigenetic marks, thereby regulating the transcription of several candidate genes responsible for proliferation and apoptosis. Both anti-p-BQ antibody and vitamin C (a strong reductant of p-BQ) prevented CS/p-BQ-induced proliferation of lung cells.
Despite major advances in the treatment and management of lung cancer, most patients eventually die. Consequently, newer approaches such as chemoprevention(s) are necessary. We consider that prevention of CS-induced proliferation of lung cells by vitamin C and/or anti-p-BQ antibody may provide a novel intervention for preventing initiation of CS-induced lung cancer.
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