The function of IGF-IR in NNK-mediated lung tumorigenesis

p27 specifically decreases in squamous carcinoma, and mediates NNK-induced transformation of human bronchial epithelial cells

Lung cancer remains the leading cause of cancer-related deaths, with cigarette smoking being the most critical factor, linked to nearly 90% of lung cancer cases. NNK, a highly carcinogenic nitrosamine found in tobacco, is implicated in the lung cancer-causing effects of cigarette smoke. Although NNK is known to mutate or activate certain oncogenes, its potential interaction with p27 in modulating these carcinogenic effects is currently unexplored. Recent studies have identified specific downregulation of p27 in human squamous cell carcinoma, in contrast to adenocarcinoma. Additionally, exposure to NNK significantly suppresses p27 expression in human bronchial epithelial cells. Subsequent studies indicates that the downregulation of p27 is pivotal in NNK-induced cell transformation. Mechanistic investigations have shown that reduced p27 expression leads to increased level of ITCH, which facilitates the degradation of Jun B protein. This degradation in turn, augments miR-494 expression and its direct regulation of JAK1 mRNA stability and protein expression, ultimately activating STAT3 and driving cell transformation. In summary, our findings reveal that: (1) the downregulation of p27 increases Jun B expression by upregulating Jun B E3 ligase ITCH, which then boosts miR-494 transcription; (2) Elevated miR-494 directly binds to 3'-UTR of JAK1 mRNA, enhancing its stability and protein expression; and (3) The JAK1/STAT3 pathway is a downstream effector of p27, mediating the oncogenic effect of NNK in lung cancer. These findings provide significant insight into understanding the participation of mechanisms underlying p27 inhibition of NNK induced lung squamous cell carcinogenic effect.

Proteome derangement in malignant epithelial cells and its stroma following exposure to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone

Discovering novel changes in the proteome of malignant lung epithelial cells and/or the tumor-microenvironment is paramount for diagnostic, prognostic, and/or therapy development. A time-dependent 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced mouse lung tumor model was used to screen the proteome of lung tumors. NNK-transformed human lung epithelial BEAS-2B cells were then established to evaluate the epithelial cell-specific protein changes. A duration-dependent increase of tumor burden was observed in NNK-treated mice, 2/12 (17%), 8/12 (67%), 9/12 (75%), and 10/10 (100%) at weeks 8, 12, 16, and 20 after the NNK exposure, respectively. A total of 25 differentially expressed proteins (≥ twofold change), predominantly structural, signaling, and metabolic proteins, were detected by two-dimensional difference gel electrophoresis and identified by mass spectrometry. Calregulin, ezrin, histamine releasing factor (HRF), and inorganic pyrophosphatase 1 (PPA1) exhibited changes and were further confirmed via immunoblotting. In addition, immunohistochemistry (IHC) analysis indicated upregulated E-cadherin and decreased vimentin expression in epithelial cells of tumor tissues. Acquisition of a neoplastic phenotype in NNK-transformed BEAS-2B cells was demonstrated by enhanced wound closure and increased anchorage independent colony formation. In transformed BEAS-2B cells, protein expression of E-cadherin, ezrin, and PPA1 (but not calregulin and HRF) was upregulated, as was observed in tumor tissues IHC staining using mouse lung tumor tissues further revealed that HRF upregulation was not lung epithelial cell specific. Altogether, tumorigenesis after NNK exposure may be initiated by protein dysregulation in lung epithelial cells together with proteome derangement derived from other cell types existing in the tumor-microenvironment.

Effect of Soybean Isoflavones on Proliferation and Related Gene Expression of Sow Mammary Gland Cells In Vitro

The present study was conducted to investigate the effects of synthetic soybean isoflavones (ISO) on the proliferation and related gene expression of sow mammary gland cells. Cells were cultured with 0 (control), 10, 20, or 30 μM of ISO under incubation conditions. After a 48 h incubation, these ISO-incubated cells proliferated more (p < 0.05) than the control cells. Cyclin E expression was higher (p < 0.05) in the 10 μM ISO and 20 μM ISO treatment groups than in the control group. Cyclin D1 and p21 expressions decreased (p < 0.05) with the 10 μM ISO treatment for 48 h. The relative mRNA abundances of the cells’ IG-1R (Insulin-like growth factor-1R), EGFR (Epidermal growth factor receptor), STAT3 (Signal transducer and activator of transcription 3) and AKT (protein kinase B) were enhanced (p < 0.05) by the 20 μM ISO treatment for 24 h and 48 h in the medium. The relative mRNA abundances of κ-casein at 48 h of incubation and β-casein at 24 h and 48 h of incubation were increased (p < 0.05) by 10 μM of ISO supplementation. It was concluded that ISO improved the proliferation of sow mammary gland cells, possibly by regulating cyclins and function genes expression in the cell proliferation signaling pathway.

Involvement of twist in NNK exposure-promoted lung cancer cell migration and invasion

Nicotine-derived nitrosamine ketone (NNK), one of the potent carcinogens in cigarette smoke, has been reported to facilitate lung cancer cell migration and invasion. Twist plays an important role in regulating migration and invasion of lung cancer cells. However, it is unclear whether Twist is implicated in NNK-induced migration and invasion of lung cancer cells. Lung cancer cells were exposed to various doses of NNK for four weeks. The expression levels of protein and mRNA were detected by western blot and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Small interfering RNA (siRNA) was applied to knock down the expression of Twist. The ability of cell migration and invasion was evaluated by wound-healing assay and Transwell invasion assay. NNK exposure increased the levels of Twist protein and mRNA expression in lung cancer cells compared to solvent control. Lung cancer cells exposed to NNK exhibited higher ability of migration and invasion than those with solvent control did. Twist silencing could block NNK-promoted migration and invasion of lung cancer cells. NNK exposure increased the expression levels of N-cadherin mRNA and decreased the expression levels of E-cadherin mRNA in lung cancer cells, which could be modulated by Twist silencing. In conclusion, Twist was involved in NNK-induced migration and invasion of lung cancer cells.

Unique roles of Akt1 and Akt2 in IGF-IR mediated lung tumorigenesis

AKT is a serine-threonine kinase that becomes hyperactivated in a number of cancers including lung cancer. Based on AKT's association with malignancy, molecules targeting AKT have entered clinical trials for solid tumors including lung cancer. However, the AKT inhibitors being evaluated in clinical trials indiscriminately inhibit all three AKT isoforms (AKT1-3) and it remains unclear whether AKT isoforms have overlapping or divergent functions. Using a transgenic mouse model where IGF-IR overexpression drives lung tumorigenesis, we found that loss of Akt1 inhibited while loss of Akt2 enhanced lung tumor development. Lung tumors that developed in the absence of Akt2 were less likely to appear as discrete nodules and more frequently displayed a dispersed growth pattern. RNA sequencing revealed a number of genes differentially expressed in lung tumors lacking Akt2 and five of these genes, Actc1, Bpifa1, Mmp2, Ntrk2, and Scgb3a2 have been implicated in human lung cancer. Using 2 human lung cancer cell lines, we observed that a selective AKT1 inhibitor, A-674563, was a more potent regulator of cell survival than the pan-AKT inhibitor, MK-2206. This study suggests that compounds selectively targeting AKT1 may prove more effective than compounds that inhibit all three AKT isoforms at least in the treatment of lung adenocarcinoma.

Insulin-like growth factor (IGF) axis in cancerogenesis

Determination of the role of insulin-like growth factor (IGF) family components in carcinogenesis of several human tumors is based on numerous epidemiological and pre-clinical studies, experiments in vivo and in vitro and on attempts at application of drugs affecting the IGF axis. Investigative hypotheses in original studies were based on biological functions manifested by the entire family of IGF (ligands, receptors, linking proteins, adaptor molecules). In the context of carcinogenesis the most important functions of IGF family involve intensification of proliferation and inhibition of cell apoptosis and effect on cell transformation through synthesis of several regulatory proteins. IGF axis controls survival and influences on metastases of cells. Interactions of IGF axis components may be of a direct or indirect nature. The direct effects are linked to activation of PI3K/Akt signaling pathway, in which the initiating role is first of all played by IGF-1 and IGF-1R. Activity of this signaling pathway leads to an increased mitogenesis, cell cycle progression, and protection against different apoptotic stresses. Indirect effects of the axis depend on interactions between IGF and other molecules important for cancer etiology (e.g. sex hormones, products of suppressor genes, viruses, and other GFs) and the style of life (nutrition, physical activity). From the clinical point of view, components of IGF system are first of all considered as diagnostic serous and/or tissue biomarkers of a given cancer, prognostic factors and attractive target of modern anti-tumor therapies. Several mechanisms in which IGF system components act in the process of carcinogenesis need to be clarified, mainly due to multifactorial etiology of the neoplasms. Pin-pointing of the role played in carcinogenesis by any single signaling pathway remains particularly difficult. The aim of this review is to summarize the current data of several epidemiological studies, experiments in vitro and on animal models, to increase our understanding of the complex role of IGF family components in the most common human cancers.

Tobacco nitrosamines as culprits in disease: mechanisms reviewed

The link between tobacco abuse and cancer is well-established. However, emerging data indicate that toxins in tobacco smoke cause cellular injury due to enhanced toxic/metabolic effects of metabolites, disruption of intracellular signaling mechanisms, and formation of DNA, protein, and lipid adducts that impair function and promote oxidative stress and inflammation. These effects of smoking, which are largely non-carcinogenic, can be produced by tobacco-specific nitrosamines and their metabolites. These factors could account for the increased rates of neurodegeneration and insulin resistance diseases among smokers. Herein, we review nicotine and tobacco-specific nitrosamine metabolism, mechanisms of adduct formation, DNA damage, mutagenesis, and potential mechanisms of disease.

The peroxisome proliferator-activated receptor (PPAR) α agonist fenofibrate suppresses chemically induced lung alveolar proliferative lesions in male obese hyperlipidemic mice

Activation of peroxisome proliferator-activated receptor (PPAR) α disrupts growth-related activities in a variety of human cancers. This study was designed to determine whether fenofibrate, a PPARα agonist, can suppress 4-nitroquinoline 1-oxide (4-NQO)-induced proliferative lesions in the lung of obese hyperlipidemic mice. Male Tsumura Suzuki Obese Diabetic mice were subcutaneously injected with 4-NQO to induce lung proliferative lesions, including adenocarcinomas. They were then fed a diet containing 0.01% or 0.05% fenofibrate for 29 weeks, starting 1 week after 4-NQO administration. At week 30, the incidence and multiplicity (number of lesions/mouse) of pulmonary proliferative lesions were lower in mice treated with 4-NQO and both doses of fenofibrate compared with those in mice treated with 4-NQO alone. The incidence and multiplicity of lesions were significantly lower in mice treated with 4-NQO and 0.05% fenofibrate compared with those in mice treated with 4-NQO alone (p<0.05). Both doses of fenofibrate significantly reduced the proliferative activity of the lesions in 4-NQO-treated mice (p<0.05). Fenofibrate also significantly reduced the serum insulin and insulin-like growth factor (IGF)-1 levels, and decreased the immunohistochemical expression of IGF-1 receptor (IGF-1R), phosphorylated Akt, and phosphorylated Erk1/2 in lung adenocarcinomas. Our results indicate that fenofibrate can prevent the development of 4-NQO-induced proliferative lesions in the lung by modulating the insulin-IGF axis.

NNK-Induced Lung Tumors: A Review of Animal Model

The incidence of lung adenocarcinoma has been remarkably increasing in recent years due to the introduction of filter cigarettes and secondary-hand smoking because the people are more exposed to higher amounts of nitrogen oxides, especially 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone(NNK), which is widely applied in animal model of lung tumors. In NNK-induced lung tumors, genetic mutation, chromosome instability, gene methylation, and activation of oncogenes have been found so as to disrupt the expression profiles of some proteins or enzymes in various cellular signal pathways. Transgenic animal with specific alteration of lung cancer-related molecules have also been introduced to clarify the molecular mechanisms of NNK in the pathogenesis and development of lung tumors. Based on these animal models, many antioxidant ingredients and antitumor chemotherapeutic agents have been proved to suppress the NNK-induced lung carcinogenesis. In the future, it is necessary to delineate the most potent biomarkers of NNK-induced lung tumorigenesis, and to develop efficient methods to fight against NNK-associated lung cancer using animal models.

Epigenetic effects and molecular mechanisms of tumorigenesis induced by cigarette smoke: an overview

Cigarette smoking is one of the major causes of carcinogenesis. Direct genotoxicity induced by cigarette smoke leads to initiation of carcinogenesis. Nongenotoxic (epigenetic) effects of cigarette smoke also act as modulators altering cellular functions. These two effects underlie the mechanisms of tumor promotion and progression. While there is no lack of general reviews on the genotoxic and carcinogenic potentials of cigarette smoke in lung carcinogenesis, updated review on the epigenetic effects and molecular mechanisms of cigarette smoke and carcinogenesis, not limited to lung, is lacking. We are presenting a comprehensive review of recent investigations on cigarette smoke, with special attentions to nicotine, NNK, and PAHs. The current understanding on their molecular mechanisms include (1) receptors, (2) cell cycle regulators, (3) signaling pathways, (4) apoptosis mediators, (5) angiogenic factors, and (6) invasive and metastasis mediators. This review highlighted the complexity biological responses to cigarette smoke components and their involvements in tumorigenesis.