The effect of nicotine on the expressions of the α7 nicotinic receptor gene and Bax and Bcl-2 proteins in the mammary gland epithelial-7 breast cancer cell line and its relationship to drug resistance

Abstract

The binding of nicotine with nicotinic acetylcholine receptors (nAChRs) stimulates cell division and increases drug resistance in cancer. Experiments with specific inhibitors such as RNAi, hexamethonium, and α-bungarotoxin showed that α7 nicotinic receptor plays a key role in the pro-proliferation activity of nicotine. However, the mechanism of nicotine in the progress of breast cancer, the commonest malignancy in women, remains unknown. This study focuses on the effect of nicotine on the expressions of the α7 nicotinic receptor gene and Bax and Bcl-2 proteins in mammary gland epithelial-7 (MCF-7) breast cancer cells and its relationship to drug resistance. To evaluate the effect on drug resistance, human mammary gland epithelial adenocarcinomas from the MCF-7 line were exposed to 100 μl of nicotine at a concentration of 9.2 mg/ml for varying periods of time. Then, the cells were treated with 1, 2, 3 or 5 μl/ml of doxorubicin, either with or without the continued presence of nicotine. Cell viability was determined using the MTT assay. The biochemical parameters of apoptosis, including the expressions of Bax, Bcl-2 and α7 nicotinic receptor proteins were determined via western blotting, and the α7 nicotinic receptor gene expression level was assessed via real-time qPCR using the 2(-ΔΔCt) method. Differences in the target gene expression levels were evaluated with ANOVA with p ≤ 0.05 considered significant. We found a novel and effective signaling pathway of nicotine in the MCF-7 breast cancer cell line. The levels of α7 nicotinic receptor and Bcl-2 protein increased but the Bax protein levels decreased, while the α7 nicotinic receptor gene expression level was not significantly different compared with the control.

Nicotine-Mediated Regulation of Nicotinic Acetylcholine Receptors in Non-Small Cell Lung Adenocarcinoma by E2F1 and STAT1 Transcription Factors

“…Our lab and others have previously reported that nicotine, which is the addictive component of tobacco smoke, while not thought to initiate tumors itself can enhance a number of tumor promoting properties including proliferation, migration, invasion, epithelial-to-mesenchymal transition (EMT), and angiogenesis [ 11 , 21 , 35 , 48 , 49 ]. Further, nicotine is known to mediate therapeutic resistance, survival/resistance to apoptosis, self-renewal of cancer stem-like cells, as well as modulate a number of immune properties in cancer [ 12 , 50 – 52 ]. These tumor promoting effects have been shown to occur primarily through the binding to and activation of nAChRs; and proliferation, migration, invasion, and EMT have been shown to occur through the α7 nAChR subunit in specific, implicating it in tumor progression.…”

miR-155 mediates arsenic trioxide resistance by activating Nrf2 and suppressing apoptosis in lung cancer cells

“…This indicated that miR-155 efficiently downregulated apoptosis. Since a low ratio of Bax/Bcl-2 can mediate anti-cancer drug resistance by preventing the initiation of apoptosis 25 , we then asked if up- or downregulation of miR-155 could up- or downregulate apoptosis by modulating the ratio of Bax/Bcl-2. To address this, we examined the expression level of Bax and Bcl-2 proteins in A549R cells transfected with the miR-155 mimic or the miR-155 inhibitor.…”

Not Only Immune Escape—The Confusing Role of the TRP Metabolic Pathway in Carcinogenesis

“…Moreover, in gastric cancer, cholangiocarcinoma, this receptor inhibition was connected with reduced expression of EMT markers [158]. Scientific reports also indicated increased apoptosis of breast cancer and cholangiocarcinoma cells after a7nAChR silencing [159]. KYNA is also considered a tumor suppressor due to the inhibition of fibroblast growth factor-1 (FGF-1) release [160], which is involved in MMPs activation, angiogenesis, tumor progression, promotion of cancer cells stemness and is associated with worst patients' prognosis [161][162][163][164][165][166].…”