Silencing A7-nAChR levels increases the sensitivity of gastric cancer cells to ixabepilone treatment

Abstract

Gastric cancer is an important health issue worldwide. Currently, improving the therapeutic efficacy of chemotherapy drugs is an important goal of cancer research. Alpha-7 nicotine acetylcholine receptor (A7-nAChR) is the key molecule that mediates gastric cancer progression, metastasis, and therapy responses; however, the role of A7-nAChR in the therapeutic efficacy of ixabepilone remains unclear. A7-nAChR expression was silenced by small interfering RNA (siRNA) technology. The cytotoxicity of ixabepilone was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and ixabepilone-induced apoptosis was analyzed by flow cytometry and annexin V/propidium iodide (PI) apoptotic assay. The expression patterns of anti-apoptotic proteins (AKT, phospho-AKT, Mcl-1, and Bcl-2) and pro-apoptotic proteins (Bad and Bax) were determined by western blot. Our study found that A7-nAChR knockdown (A7-nAChR-KD) AGS cells were more sensitive to ixabepilone administration than scrambled control AGS cells. We found that A7-nAChR knockdown enhanced ixabepilone-induced cell death as evidenced by the increased number of annexin V-positive (apoptotic) cells. After scrambled control and A7-nAChR-KD cells were treated with ixabepilone, we found that pAKT and AKT levels were significantly reduced in both groups of cells. The levels of Bcl-2 and the anti-apoptotic Mcl-1 isoform increased dramatically after ixabepilone treatment in scrambled control cells but not in A7-nAChR-KD cells. Bad and Bax levels did not change between the treatment group and vehicle group in both A7-nAChR-KD and scrambled control cells, whereas cleaved PARP levels dramatically increased in ixabepilone-treated A7-nAChR-KD cells. Our results demonstrated that knockdown of A7-nAChR enhanced the sensitivity of gastric cancer cells to ixabepilone administration. Thus, the A7-nAChR expression level in patients with gastric cancer may be a good indicator of ixabepilone sensitivity.

α-Conotoxins Enhance both the In Vivo Suppression of Ehrlich carcinoma Growth and In Vitro Reduction in Cell Viability Elicited by Cyclooxygenase and Lipoxygenase Inhibitors

“…The reduced sensitivity of gastric cancer to cisplatin under the influence of nicotine was largely blocked by siRNA targeting the CHRNA5 gene, which encodes α5 subunit of nAChR [12]. Knockdown of α7 nAChR increased the sensitivity of gastric cancer cells to taxan and ixabepilone [13]. Nicotine contributed to the survival of pancreatic cancer cells, leading to protein kinase B (AKT) phosphorylation and activation of atypical protein kinase C, while mecamilamine, a non-specific nAChR blocker, reduced this effect [14].…”

Contribution of Mitochondrial Ion Channels to Chemo-Resistance in Cancer Cells

“…Interestingly, the homo-pentameric α7 nAChRs belong to the most ancient branch of this receptor family and are expressed in neurons and non-excitable cells, where they mediate pro-proliferative and anti-inflammatory signaling. Gastric cancer cells, where α7 nAChR expression was knocked-down, showed resistance to 5-fluorouracil (5-FU), a clinically used chemotherapeutic agent [84] but were reportedly more sensitive to docetaxel, paclitaxel and ixabepilone treatment [85,86]. The specific role of mitochondrial nAChRs versus the plasma membrane-located channel was not addressed in these studies.…”

LaSota Strain Expressing The Rabies Virus Glycoprotein (rL-RVG) Suppresses Gastric Cancer by Inhibiting the Alpha 7 Nicotinic Acetylcholine Receptor (α7 nAChR)/Phosphoinositide 3-Kinase (PI3K)/AKT Pathway

“…α7-nAChR pathway activation promotes tumor cell proliferation and inhibits apoptosis via PI3K/AKT signaling pathways [27]. Recent studies suggest that some chemotherapeutic drugs, including 5-Fluorouracil and Ixabepilone, can downregulated α7-nAChR and promote gastric cancer cell apoptosis through the AKT pathway [28,29]. The rabies virus glycoprotein has nicotine receptor blocking function similar to that of coral snake venom [10].…”

“…NDV has been explored as an oncolytic agent [7,8]. Acetylcholine receptors (AChR) are highly expressed in non-small cell lung cancer, gastric cancer, bladder cancer, and colorectal cancer [9]. Many studies have found that α7-nAChR affects expression and activation of cancer cell proliferation, invasion, metastasis, angiogenesis, and the inflammatory response [10–12].…”