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

Alpha7 nicotinic acetylcholine receptor expression in Sorafenib-resistant Hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC), the most prevalent kind of liver cancer, remains one of the world's main causes of death. The alpha7 nicotinic acetylcholine receptor (α7nAchR) has been recognized to be overexpressed in malignancies and chemoresistance. Since little is known about the role of α7nAchR expression in drug-resistant cells, this study was designed to investigate the effect of α7nAchR suppression in combination with Sorafenib (SOR) on SOR-resistant HCC cells. First, SOR-resistant HCC cells were generated. To suppress the expression of α7nAchR, cells were treated with SOR following siRNA transfection. qRT-PCR was used to examine the expression of α7nAchR and apoptotic genes by evaluating the IC50 of SOR and the combination of α7nAchR siRNA and SOR on the survival of resistant cells. Moreover, apoptosis, autophagy, and cell cycle analysis for resistant HCC cells were performed using flow cytometry. Cell migration and colony formation assays were also used for further confirmation. Our results suggest that inhibiting α7nAchR can lead resistant HCC cells to become sensitive. Furthermore, when siRNA and SOR were treated together, HCC-resistant cells showed a considerable reduction in α7nAchR mRNA gene expression. In addition, when α7nAchR was downregulated in combination with SOR, migration and colony formation were inhibited. Apoptosis was triggered by modulating the expression of apoptotic target genes, and cell cycle arrest was observed in the G2-M and subG1 phases. Overexpression of α7nAchR in SOR-resistant HCC cells suggests that it might be a therapeutic target for HCC cell resistance therapy.

Inflammatory reflex disruption in COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified in Wuhan, China, in late 2019 and caused coronavirus disease 2019 (COVID-19), which is still a global pandemic. In most infected people, SARS-CoV-2 can only cause moderate symptoms, while in other patients, it leads to severe illness and eventually death. Although the main clinical manifestation of COVID-19 is often seen in the lungs, this disease affects almost all body organs. The excessive and prolonged release of inflammatory cytokines that may occur in COVID-19 patients, known as cytokine storms, stimulates undesired immune responses and can cause various tissues damage. In the current review article, we focus on the potential advantages of the intrinsic cholinergic anti-inflammatory pathway (CAP) as the efferent arm of inflammatory reflex in COVID-19 management. Considering this endogenous protective mechanism against chronic inflammation, we focused on the effects of SARS-CoV-2 in the destruction of this anti-inflammatory system. Several studies indicated the interaction of SARS-CoV-2 with the alpha7 subtype of the nicotinic acetylcholine receptor as the effector molecule of the inflammatory reflex. On the other hand, neurological manifestations have increasingly been identified as significant extrapulmonary manifestations of COVID-19. The rational connection between these findings and COVID-19 pathogenesis may be an important issue in both our understanding and dealing with this disease. COVID-19 is deeply rooted in our daily life and requires an urgent need for the establishment of effective therapeutic options, and all the possible treatments must be considered for the control of such inflammatory conditions.

The Natural Compound Dehydrocrenatidine Attenuates Nicotine-Induced Stemness and Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma by Regulating a7nAChR-Jak2 Signaling Pathways

Background

Exposure to nicotine has been observed associated with tumor progression, metastasis, and therapy resistance of many cancers. Hepatocellular carcinoma (HCC) is one major cancer related to the liver and the most difficult to treat malignancies worldwide. The underlying mechanism of nicotine in the stimulation of HCC tumorigenesis is still not studied well.

Methods

Classically, nicotine binds to nicotinic acetylcholine receptors (nAChRs) and induces many downstream cancer-associated signaling pathways. Big data analysis is used to explore the importance of a7nAChR-Jak2 axis in the progression of hepatocellular carcinoma. Bioinformatic analysis was performed to determine gene associated with a7nAChR-Jak2 axis of HCC patients. Biological importance of a7nAChR-Jak2 axis was investigated in vitro (Hun7 and HepG2 cell lines), and athymic nude mouse models bearing HepG2-HCC cells xenografts were established in vivo.

Result

We found that nicotine exposure stimulated the HCC tumorigenicity by inducing the expression of one of the key nAChRs subunit that is α7nAChR as well as the expression of Janus kinase (JAK)-2. In both the in vitro and in vivo studies, the reduced overexpression of α7nAChR and increased sensitization of HCC towards treatment is observed with dehydrocrenatidine (DHCT), a novel and potent JAK family kinase inhibitor. Interestingly, DHCT treatment results in the reduction of the epithelial-mesenchymal transition process which leads to a significant reduction of clonogenicity, migratory, and invasive ability of HCC cells. Moreover, DHCT treatment also inhibits the cancer stem cell phenotype by inhibiting the tumor-sphere formation and reducing the number of ALDH1+ cells population in nicotine-stimulated HCC cells.

Conclusions

Taken together, the presented results indicate the positive effect of inhibition of nicotine induced overexpression of α7nAChR and JAK2, unique to HCC. Thus, these findings suggest the nicotine effect on HCC progression via α7nAChR-mediated JAK2 signaling pathways, and DHCT treatment enhances the therapeutic potential of HCC patients via overcoming/reversing the effect of nicotine in HCC patients.

Nicotinic acetylcholine receptors in chemotherapeutic drugs resistance: An emerging targeting candidate

There is no definitive cure for cancer, and most of the current chemotherapy drugs have limited effects due to the development of drug resistance and toxicity at high doses. Therefore, there is an ongoing need for identifying the causes of chemotherapeutic resistance, and it will be possible to develop innovative treatment approaches based on these novel targeting candidates. Cigarette smoking is known to be one of the main causes of resistance to chemotherapeutic agents. Nicotine as a component of cigarette smoke is an exogenous activator of nicotinic acetylcholine receptors (nAChRs). It can inhibit apoptosis, increase cell proliferation and cell survival, reducing the cytotoxic effects of chemotherapy drugs and cause a reduced therapeutic response. Recent studies have demonstrated that nAChRs and their downstream signaling pathways have considerable implications in different cancer's initiation, progression, and chemoresistance. In some previous studies, nAChRs have been targeted to obtain better efficacies for chemotherapeutics. Besides, nAChRs-based therapies have been used in combination with chemotherapy drugs to reduce the side effects. This strategy requires lower doses of chemotherapy drugs compared to the conditions that must be used alone. Here, we discussed the experimental and clinical studies that show the nAChRs involvement in response to chemotherapy agents. Also, controversies relating to the effects of nAChR on chemotherapy-induced apoptosis are in our focus in this review article. Delineating the complex influences of nAChRs would be of great interest in establishing new effective chemotherapy regimens.

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

Several biochemical mechanisms, including the arachidonic acid cascade and activation of nicotinic acetylcholine receptors (nAChRs), are involved in increased tumor survival. Combined application of inhibitors acting on these two pathways may result in a more pronounced antitumor effect. Here, we show that baicalein (selective 12-lipoxygenase inhibitor), nordihydroguaiaretic acid (non-selective lipoxygenase inhibitor), and indomethacin (non-selective cyclooxygenase inhibitor) are cytotoxic to Ehrlich carcinoma cells in vitro. Marine snail α-conotoxins PnIA, RgIA and ArIB11L16D, blockers of α3β2/α6β2, α9α10 and α7 nAChR subtypes, respectively, as well as α-cobratoxin, a blocker of α7 and muscle subtype nAChRs, exhibit low cytotoxicity, but enhance the antitumor effect of baicalein 1.4-fold after 24 h and that of nordihydroguaiaretic acid 1.8-3.9-fold after 48 h of cell cultivation. α-Conotoxin MII, a blocker of α6-containing and α3β2 nAChR subtypes, increases the cytotoxic effect of indomethacin 1.9-fold after 48 h of cultivation. In vivo, baicalein, α-conotoxins MII and PnIA inhibit Ehrlich carcinoma growth and increase mouse survival; these effects are greatly enhanced by the combined application of α-conotoxin MII with indomethacin or conotoxin PnIA with baicalein. Thus, we show, for the first time, antitumor synergism of α-conotoxins and arachidonic acid cascade inhibitors.

Kynurenic acid and cancer: facts and controversies

Kynurenic acid (KYNA) is an endogenous tryptophan metabolite exerting neuroprotective and anticonvulsant properties in the brain. However, its importance on the periphery is still not fully elucidated. KYNA is produced endogenously in various types of peripheral cells, tissues and by gastrointestinal microbiota. Furthermore, it was found in several products of daily human diet and its absorption in the digestive tract was evidenced. More recent studies were focused on the potential role of KYNA in carcinogenesis and cancer therapy; however, the results were ambiguous and the biological activity of KYNA in these processes has not been unequivocally established. This review aims to summarize the current views on the relationship between KYNA and cancer. The differences in KYNA concentration between physiological conditions and cancer, as well as KYNA production by both normal and cancer cells, will be discussed. The review also describes the effect of KYNA on cancer cell proliferation and the known potential molecular mechanisms of this activity.

The dual role of alpha7 nicotinic acetylcholine receptor in inflammation-associated gastrointestinal cancers

Alpha7 nicotinic acetylcholine receptor (α7nAChR) is one of the main subtypes of nAChRs that modulates various cancer-related properties including proliferative, anti-apoptotic, pro-angiogenic and pro-metastatic activities in most of the cancers. It also plays a crucial role in inflammation control through the cholinergic anti-inflammatory pathway in numerous pathophysiological contexts. Such diverse physiological and pathological functions that initiate from this receptor may have significant impacts in determining the outcome of different cancers. Various tissues of gastrointestinal (GI) cancers such as gastric, colorectal, pancreatic and liver cancers have shown the up-regulated expression of α7nAChR as compared to normal adjacent tissues. According to the well-established connection between inflammation and tumorigenesis in the digestive system, there are mounting studies demonstrated either stimulatory or inhibitory effects of α7nAChR signaling in the development of GI cancers. To date, the precise underlying mechanisms related to this receptor in patients with GI cancers have not been fully elucidated. Regarding the paradoxical modulatory effects of this receptor in carcinogenesis, in this review, we aim to summarize the accumulated evidence about the involvement of α7nAChR in inflammation-associated GI cancers. It seems that the complex influences of α7nAChR may be a promising target in designing novel strategies in the treatment of such pathologic conditions.

Small interfering RNA targeting alpha7 nicotinic acetylcholine receptor sensitizes hepatocellular carcinoma cells to sorafenib

AIMS

It has been demonstrated that reduced expression of alpha7 nicotinic acetylcholine receptor (α7nAChR) led to reduced chemotherapeutic drugs resistance in various cancer cells. However, whether small interfering RNA (siRNA) mediated knockdown of α7nAChR can reduce sorafenib (SOR) resistance in HCC cells remains to be determined.

MATERIALS AND METHODS

The effects of α7nAChR-siRNA in combination with SOR treatment was analyzed in human (HepG2) and mouse (Hepa 1-6) HCC cell lines. The MTT, DAPI staining and flow cytometry assays were applied to measure the cell viability, apoptosis and cell cycle progression of the cells. Also, the changes in the mRNA and protein levels of the α7nAChR were measured by quantitative real-time PCR and western blot analysis, respectively.

KEY FINDINGS

The results revealed that SOR increased both mRNA and protein levels of α7nAChR in HCC cells. Treatment with α7nAChR-siRNA abolished these effects. Also, SOR treatment in combination with α7nAChR-siRNA significantly sensitizes HCC cells to SOR cytotoxicity. This combination therapy significantly induced HCC cells apoptosis compared to SOR alone.

SIGNIFICANCE

These experimental results indicate that knockdown of α7nAChR by siRNA increased the SOR antitumor activity of HCC cells and suggests that this additive combination is a promising drug candidate for HCC therapy.

Nervous system and gastric cancer

The nervous system has been recently shown to exert impact on gastric cancer directly and indirectly. Gastric cancer cells invade nerve fibers to induce outgrowth and branching of neural cells, and nerve fibers in turn infiltrate into tumor microenvironment to promote progression of gastric cancer. Additionally, the neuro-immune interaction also plays an important role in gastric cancer development. The interplay of nerves and gastric cancer is mediated by many nervous system-associated factors, which can not only be synthesized and released by both cancer cells and nerve terminals, but also participate in regulation of many aspects of gastric cancer such as cell proliferation, angiogenesis, metastasis and recurrence. Furthermore, clinical researches indicate that some of these factors are significant diagnosis and prognosis biomarkers for gastric cancer. Herein, we reviewed recent advances and future prospects of the interaction between nervous system and gastric cancer.

Identification of nicotinic acetylcholine receptor subunits in different lung cancer cell lines and the inhibitory effect of alpha-conotoxin TxID on lung cancer cell growth

Lung cancer is an aggressive tumor with high incidence and mortality rate. There was growing evidence supporting that nicotinic acetylcholine receptors (nAChRs) play vital role inlung cancer development. In this study, the expression of α3, α4, α5, α6, α7, α9, α10, β2, β3, β4 nAChR subunits on protein and mRNA level were studied in A549, NCI-H1299, NCI-H1688, DMS114 and normal human embryonic lung fibroblast (HEL) cell lines by real-time quantitative PCR (qPCR) and Western blot assay respectively. The results indicated that most of these nAChR subunits were expressed in these five cell lines. Compared with normal cells, the expression of α3 and β4 nAChR subunits were upregulated in A549 and NCI-H1299. Thus, we treated A549 and NCI-H1299 with an antagonist α-conotoxin TxID which potently and selectively blocks α3β4 nAChRs. TxID treatment could inhibit A549 and NCI-H1299 cell growth and enhance the inhibitory effect of adriamycin when treated simultaneously. To sum up, our study identified the expression of nAChR subunits in different lung cells and the anti-tumor effect of α-conotoxin TxID, which may provide novel strategies for lung cancer therapy.

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

BACKGROUND The recombinant avirulent Newcastle disease virus (NDV) LaSota strain expressing the rabies virus glycoprotein (rL-RVG) can induce much greater apoptosis than can NDV in gastric carcinoma cells, but the mechanisms involved remains unclear. MATERIAL AND METHODS The 2 gastric carcinoma cell lines were divided into the rL-RVG group, the NDV group, and the PBS group. MTT assay was used to detect and analyze cell viability. siRNA for alpha7-nAChR, alpha7-nAChR antagonist, or alpha7-nAChR agonist, AKT antagonist, and p-AKT agonist were used for pretreatment. The protein expressions of RVG, NDV, alpha7-nAChR, cleaved caspase-3, p-AKT, PI3K, Bcl-2, and Bax proteins were detected by Western blot assay. Immunofluorescence was used to detect expressions of alpha7-nAChR proteins. Light microscopy, flow cytometry, and TUNEL assay were used to assess apoptosis. RESULTS The results showed that 2 virus concentrations over 10³ dilution caused greater cell proliferation inhibition. rL-RVG treatment increased the expression of alpha7-nAChR, cleaved caspase-3, and Bax protein but decreased the expression of p-AKT, PI3K, and Bcl-2 protein. When the groups were pretreated with alpha7-nAChR antagonist, the alpha7-nAChR, cleaved caspase-3, and Bax protein expression increased, but the expression of p-AKT, PI3K, and Bcl-2 protein was clearly decreased. However, the results in the alpha7-nAChR agonist group were the opposite. When treated with the AKT antagonist, the result was the same as in the rL-RVG treatment group. The result in the AKT agonist group was the opposite of that in the AKT antagonist group. Compared with the NDV group, the results of light microscopy, FCM, and TUNEL assay showed that alpha7-nAChR antagonist significantly affected the apoptosis of gastric cancer cells in the rL-RVG group. CONCLUSIONS rL-RVG leads to much greater apoptosis through the alpha7-nAChR/PI3K/AKT pathway.

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

Mitochondrial ion channels are emerging oncological targets, as modulation of these ion-transporting proteins may impact on mitochondrial membrane potential, efficiency of oxidative phosphorylation and reactive oxygen production. In turn, these factors affect the release of cytochrome c, which is the point of no return during mitochondrial apoptosis. Many of the currently used chemotherapeutics induce programmed cell death causing damage to DNA and subsequent activation of p53-dependent pathways that finally leads to cytochrome c release from the mitochondrial inter-membrane space. The view is emerging, as summarized in the present review, that ion channels located in this organelle may account in several cases for the resistance that cancer cells can develop against classical chemotherapeutics, by preventing drug-induced apoptosis. Thus, pharmacological modulation of these channel activities might be beneficial to fight chemo-resistance of different types of cancer cells.