Knockdown of PKM2 induces apoptosis and autophagy in human A549 alveolar adenocarcinoma cells

The M2 isoform of pyruvate kinase (PKM2), which has been identified as the predominant cause of the Warburg effect in cancer cells, is essential in tumor metabolism and growth. However, the role of PKM2 in autophagy remains to be elucidated. The present study investigated the effect of PKM2 knockdown on autophagy and apoptotic cell death in human A549 alveolar adenocarcinoma cells. Two short hairpin (sh)RNAs targeting human PKM2 mRNA were designed and lentiviral vectors were constructed. The A549 cells were infected with lentiviruses, containing shRNAs against PKM2, and the expression of PKM2 was examined by reverse transcription-quantitative polymerase chain reaction (RT‑qPCR) and immonoblotting analysis. A lactose dehydrogenase (LDH)‑coupled enzyme assay was used to detect the pyruvate kinase activity. RT‑qPCR was used to detect the mRNA expression level of glycolysis‑associated enzymes. The quantification of cells with punctate LC3 and expression of LC3II were examined to demonstrate autophagy. An MTT assay was used to detect cell viability and flow cytometry was used to determine cell apoptosis. The activity of caspase 3/7 and the expression of Bcl‑2 were also detected in A549 cells with PKM2 knockdown. The present study demonstrated that the two shRNAs efficiently downregulated the mRNA and protein expression levels of PKM2 in A549 cells. The knockdown of PKM2 decreased pyruvate kinase activity and glycolysis. Autophagy was induced in A549 cells with PKM2 knockdown. Inhibition of autophagy accelerated apoptotic death in PKM2‑knockdown cells and this was dependent on increased caspase 3/7 activity and decreased expression of Bcl‑2. In conclusion, the downregulation of PKM2 induced apoptosis and autophagy in A549 cells and this autophagy protected the cells from apoptotic cell death.

Emodin induces a reactive oxygen species-dependent and ATM-p53-Bax mediated cytotoxicity in lung cancer cells

Emodin (1,3,8-trihydroxy-6-methyl-anthraquinone), a natural anthraquinone compound isolated from the rhizome of rhubarb, has been reported to suppress tumor growth in many clinical situations. Here, we demonstrate that emodin induces apoptosis in human lung adenocarcinoma A549 cells by activating a reactive oxygen species-elicited ATM-p53-Bax signaling pathway. In response to emodin treatment, p53 protein increases in A549 cells, which in turn up-regulates Bax expression. Co-treating cells with either a p53 inhibitor or respectively knocking down the expression of p53 and Bax by shRNA extensively diminished emodin-induced cell viability, caspase 3 activation and the release of cytochrome c from the mitochondria, indicating the crucial role for p53/Bax in emodin-mediated cytotoxicity. Pre-treating cells with the antioxidant ascorbic acid not only prohibited the induction of reactive oxygen species by emodin, but also inhibited the up-regulation of p53. Upon emodin treatment, p53 is phosphorylated at Ser(15), which is accompanied by the ATM phosphorylation at Ser(1981). Both of these events could also be blocked by the presence of ascorbic acid. Moreover, knockdown of ATM by siRNA significantly reduced p53 phosphorylation and stabilization, indicating the upstream role of emodin-induced reactive oxygen species generation in ATM activation and following p53 phosphorylation and stabilization. Taken together, our results demonstrate that emodin-induced reactive oxygen species generation activates an ATM-p53-Bax-dependent signaling pathway, which consequently leads to mitochondria-dependent apoptotic cell death in human lung adenocarcinoma A549 cells.

Mineral fiber-mediated activation of phosphoinositide-specific phospholipase c in human bronchoalveolar carcinoma-derived alveolar epithelial A549 cells

Given the role of phosphoinositide-specific phospholipase C (PLC) isozymes in the control of cell growth and differentiation we were prompted to analyze the expression of some of these PLC in human bronchoalveolar carcinoma-derived alveolar epithelial A549 cells. The effects of several fluoro-edenite fibers were compared with those of tremolite, a member of the calcic amphibole group of asbestos that originates from Calabria (Italy), and crocidolite, that, due to its high toxicity, is one of the most studied asbestos amphiboles. Our data show an increased expression of both PLC beta1 and PLC gamma1 in A549 cells treated with asbestos-like fibers, hinting at a role of PLC signalling in those cancerous cells.

Mutations in BRAF and KRAS converge on activation of the mitogen-activated protein kinase pathway in lung cancer mouse models

Mutations in the BRAF and KRAS genes occur in approximately 1% to 2% and 20% to 30% of non-small-cell lung cancer patients, respectively, suggesting that the mitogen-activated protein kinase (MAPK) pathway is preferentially activated in lung cancers. Here, we show that lung-specific expression of the BRAF V600E mutant induces the activation of extracellular signal-regulated kinase (ERK)-1/2 (MAPK) pathway and the development of lung adenocarcinoma with bronchioloalveolar carcinoma features in vivo. Deinduction of transgene expression led to dramatic tumor regression, paralleled by dramatic dephosphorylation of ERK1/2, implying a dependency of BRAF-mutant lung tumors on the MAPK pathway. Accordingly, in vivo pharmacologic inhibition of MAPK/ERK kinase (MEK; MAPKK) using a specific MEK inhibitor, CI-1040, induced tumor regression associated with inhibition of cell proliferation and induction of apoptosis in these de novo lung tumors. CI-1040 treatment also led to dramatic tumor shrinkage in murine lung tumors driven by a mutant KRas allele. Thus, somatic mutations in different signaling intermediates of the same pathway induce exquisite dependency on a shared downstream effector. These results unveil a potential common vulnerability of BRAF and KRas mutant lung tumors that potentially affects rational deployment of MEK targeted therapies to non-small-cell lung cancer patients.

Cathepsin K is selectively expressed in the stroma of lung adenocarcinoma but not in bronchioloalveolar carcinoma. A useful marker of invasive growth

Lung bronchioalveolar carcinomas (BACs) are noninvasive tumors showing lepidic growth and excellent prognosis, whereas all the other variants of adenocarcinoma are invasive tumors with a worse prognosis. The identification of minimal invasive foci in adenocarcinoma, therefore, is of prognostic relevance. A series of 68 pulmonary tumors, including 40 acinar/papillary adenocarcinomas, 18 adenocarcinomas of the mixed subtype, and 10 BACs was tested by immunohistochemical analysis for cathepsin K expression, a proteinase involved in bone and extracellular matrix remodeling. Cathepsin K was produced by epithelial tumor cells in most invasive adenocarcinomas and, interestingly, by macrophages and fibroblasts in the stroma of invasive adenocarcinomas but not of BACs (P < .001). Our findings suggest pathogenetic implications of cathepsin K in the mechanisms of tumor invasiveness in lung carcinoma; in addition, cathepsin K immunodetection may be a valuable adjunct in the correct classification of pulmonary adenocarcinomas, especially in small sclerosing BACs and mixed adenocarcinoma subtypes with minimal infiltrative growth.

Inhibition of Mammalian Thioredoxin Reductase by Some Flavonoids: Implications for Myricetin and Quercetin Anticancer Activity

The thioredoxin system, composed of thioredoxin reductase (TrxR), thioredoxin (Trx), and NADPH, exerts a wide range of activities in cellular redox control, antioxidant function, cell viability, and proliferation. Recently, the selenocysteine (Sec)-containing mammalian TrxR has emerged as a new target for anticancer drug development because TrxR and Trx are overexpressed in many aggressive tumors and the tumor cells seem to be more dependent on Trx system than normal cells. Here we have investigated the inhibition of mammalian TrxR by flavonoids which have been presumed to be cancer chemoprevention agents because of their antioxidant activities. Myricetin and quercetin were found to have strong inhibitory effects on mammalian TrxRs with IC50 values of 0.62 and 0.97 micromol/L, respectively. The inhibition was shown to be concentration, NADPH, and time dependent and involved an attack on the reduced COOH-terminal -Cys-Sec-Gly active site of TrxR. Oxygen-derived superoxide anions enhanced the inhibitory effect whereas anaerobic conditions attenuated inhibition. Spectral analysis suggested that the flavonols might perform their inhibitory effects via semiquinone radicals. Additionally, the flavonols had the potential to inhibit the growth of A549 cells with the same potency as inhibition of TrxR. TrxR activity in the cell lysates was reduced on treatment with myricetin >50 micromol/L, which coincided with the oxidization of Trx. The cell cycle was arrested in S phase by quercetin and an accumulation of cells in sub-G1 was observed in response to myricetin. Thus, the anticancer activity of quercetin and myricetin may be due to inhibition of TrxR, consequently inducing cell death.

Expression of double-stranded RNA-activated protein kinase in small-size peripheral adenocarcinoma of the lung

The authors investigated the protein expression of double-stranded RNA-activated protein kinase (PKR), which was identified by using a previous cDNA microarray study, to discover PKR's correlations with several pathological parameters and to elucidate its role in neoplastic transformation and progression of lung adenocarcinomas. Immunohistochemistry for PKR was performed and a semiquantitative scoring method was calculated based on staining intensity and percentage of immunoreactive tumor cells (high vs low) for one bronchioloalveolar carcinoma (BAC), 16 adenocarcinomas consisting of BAC and invasive carcinoma (mixed) and 21 invasive adenocarcinomas without BAC (invasive). The BAC had high-grade expression and the mixed type tended to more frequently show high-grade expression than the invasive type (P = 0.028). There were no significant associations with age, tumor size, lymph node metastasis, lymphovascular invasion or the pathological stage. The Kaplan-Meier survival curves demonstrated that the patients with high-grade PKR expression had significantly shorter survival periods than those patients with low-grade PKR expression (P = 0.018). These results do not support the concept of PKR as a tumor suppressor in small-size peripheral adenocarcinomas of the lung.

A novel human tRNA-dihydrouridine synthase involved in pulmonary carcinogenesis

An increased level of dihydrouridine in tRNA(Phe) was found in human malignant tissues nearly three decades ago, but its biological significance in carcinogenesis has remained unclear. Through analysis of genome-wide gene-expression profiles among non-small cell lung carcinomas (NSCLC), we identified overexpression of a novel human gene, termed hDUS2, encoding a protein that shared structural features with tRNA-dihydrouridine synthases (DUS). The deduced 493-amino-acid sequence showed 39% homology to the dihydrouridine synthase 2 enzyme (Dus2) of Saccharomyces cerevisiae and contained a conserved double-strand RNA-binding motif (DSRM). We found that hDUS2 protein had tRNA-DUS activity and that it physically interacted with EPRS, a glutamyl-prolyl tRNA synthetase, and was likely to enhance translational efficiencies. A small interfering RNA against hDUS2 transfected into NSCLC cells suppressed expression of the gene, reduced the amount of dihydrouridine in tRNA molecules, and suppressed growth. Immunohistochemical analysis showed significant association between higher levels of hDUS2 in tumors and poorer prognosis of lung cancer patients. Our data imply that up-regulation of hDUS2 is a relatively common feature of pulmonary carcinogenesis and that selective suppression of hDUS2 enzyme activity and/or inhibition of formation of the hDUS2-tRNA synthetase complex could be a promising therapeutic strategy for treatment of many lung cancers.

Dietary lipids modulate eicosanoid release and apoptosis of cells of a murine lung alveolar carcinoma

Dietary arachidonic acid (AA) and eicosanoids influence neoplastic cell (NC) growth, differentiation and apoptosis. Plasma membrane fatty acid and cyclooxygenase (COX) and lipoxygenase (LOX) products were investigated in lung alveolar carcinoma cells from mice fed on different diets. Two groups were fed on a basic diet plus 6% of: corn oil (rich in 18:2n-6; CO) and on olein oil (rich in 18:1n-9; O), respectively. Control group (C) received commercial diet. NC fatty acids were analyzed by GLC, and apoptosis by flow cytometry and microscopy. In NC from CO group AA levels and LOX metabolites were increased, whereas COX metabolites decreased. NC from CO compared to O group diet showed a higher count of apoptosis and increased LOX:COX ratio. High levels of AA and decreased COX eicosanoids has been involved in anti-tumoral mechanisms by increasing tumor cell apoptosis. Present data emphasizes the implications of the dietary fatty acids on the neoplastic process in this tumoral model.

Tumor metastasis and the reciprocal regulation of prometastatic and antimetastatic factors by nuclear factor kappaB

To investigate the role of the transcription factor nuclear factor kappaB (NFkappaB) in tumor metastasis, we generated a murine lung alveolar carcinoma cell line (Line 1) defective in NFkappaB-signaling by retroviral delivery of a dominant negative inhibitor of NFkappaB. The NFkappaB signal blockade resulted in the down-regulation of prometastatic matrix metalloproteinase 9, a urokinase-like plasminogen activator, and heparanase and reciprocal up-regulation of antimetastatic tissue inhibitors of matrix metalloproteinases 1 and 2 and plasminogen activator inhibitor 2. NFkappaB signal blockade did not affect tumor cell proliferation in vitro or in vivo but prevented intravasation of tumor cells in an in vivo chick chorioallantoic membrane model of metastasis as well as spontaneous metastasis in a murine model. These findings suggest that NFkappaB plays a central and specific role in the regulation of tumor metastasis and may be an important therapeutic target for development of antimetastatic cancer treatments.

Induction of cytochrome P-450 1A1 in human hepatoma HepG2 and lung carcinoma NCI-H322 cells by motorcycle exhaust particulate

The effects of motorcycle exhaust particulate (MEP) on human cytochrome P-450 (P-450)-dependent monooxygenases were determined using human hepatoma cell line HepG2 and lung carcinoma cell line NCI-H322 treated with organic extracts of MEP from a two-stroke engine. Gas chromatography and mass spectrometry analysis of MEP extract revealed the presence of carcinogens benzo[a]pyrene, benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, chrysene, and indeno[1,2,3-c,d]pyrene in the chemical mixture. Treatment with MEP extract produced concentration- and time-dependent increases of monooxygenase activity in HepG2 cells. Treatment of the cells with 100 microg/ ml MEP extract for 24 h markedly increased benzo[a]pyrene hydroxylation, 7-ethoxycoumarin, and 7-ethoxyresorufin O-deethylation activities in microsomes. Immunoblot analysis of microsomal proteins using mouse monoclonal antibody 1-12-3 against P-450 1A1 revealed that MEP extract induced a P-450-immunorelated protein in the hepatoma cells. RNA blot analysis of cellular total RNA using a human P-450 1A1 3'-end cDNA probe showed that MEP extract increased the level of a hybridizable P-450 mRNA. These P-450 1A1 inductive effects of MEP extract were similar to those from treatment with 10 microM benzo[a]pyrene or 3-methylcholanthrene (3-MC) in HepG2 cells. Treatment of lung carcinoma NCI-H322 cells with 100 microg/ml MEP extract, 10 microM benzo[a]pyrene, or 3-MC resulted in induction of monooxygenase activity, protein, and mRNA of P-450 1A1, similar to the induction observed with the hepatoma cells. The present study demonstrates that MEP extract has the ability to induce human hepatic and pulmonary P-450 1A1 in the liver- and lung-derived cell lines, and the induction involves a pretranslational mechanism. Induction of the human hepatic and pulmonary P-450 1A1 in vitro may provide important information in the assessment of MEP metabolism and toxicity in humans.

Increased expression of cyclooxygenase-2 protein in rat lung tumors induced by N-nitrosobis(2-hydroxypropyl)amine

Expression of cyclooxygenase (COX)-2 protein in preneoplastic and neoplastic lung lesions induced by the administration of 2000 ppm of N-nitrosobis(2-hydroxypropyl)amine (BHP) in the drinking water to Wistar male rats, was examined immunohistochemically. The majority of alveolar/bronchiolar adenomas (ADs) and all adenocarcinomas (ADCs) examined, stained positive or strongly positive for COX-2. In contrast, only a minority of alveolar/bronchiolar hyperplasias demonstrated immunoreactivity and half of the squamous cell carcinomas examined, were only weakly positive. Western blotting analysis also revealed expression of COX-2 protein in the resected ADs and ADCs. These results clearly indicate up-regulated expression of COX-2 in lung neoplastic lesions, particularly ADs and ADCs, induced by BHP in rats.

Telomerase activity as a prognostic indicator in stage I non-small cell lung cancer

Patients with stage I non-small cell lung cancer (NSCLC) are typically treated with surgical resection alone. However, about one-third of such patients develop disease recurrence and die within 5 years after complete resection. The ability to predict recurrence could represent an important contribution to treatment planning. This study evaluates the presence of telomerase activity in tumor cells as a predictor of disease recurrence and cancer-related death after operation for stage I NSCLC patients. The activity of the telomerase enzyme was investigated by telomeric repeat amplification protocol (TRAP) in tumors and matching normal lung tissue samples obtained from 107 consecutive operable patients with pathological stage I NSCLC. Telomerase activity was detected in 66 (62%) of the 107 tumors examined and in none of the corresponding adjacent noncancerous lung tissue samples. Correlation with pathological parameters showed that telomerase activity was associated with histopathological grade (P = 0.0135) but not with tumor size or histological type. Univariate survival curves, estimated using the method of Kaplan and Meier, defined a significant association between telomerase activity and both disease-free survival (P = 0.0115) and overall survival (P = 0.0129). In multivariate analyses, performed by Cox's proportional hazards regression models, the presence of telomerase activity was the only strong predictor of disease-free survival (P = 0.0173) and overall survival (P = 0.0187). Our data indicate that telomerase activity can be an important prognostic factor that should be considered in future prospective trials of adjuvant therapy for high-risk stage I NSCLC patients.

Prognostic significance of polo-like kinase (PLK) expression in non-small cell lung cancer

Our previous data indicate that the expression of the PLK gene which codes for a serine/threonine kinase is restricted to proliferating cells. In Northern blot experiments PLK mRNA expression was at the limit of detection in normal lung tissue but elevated in most samples of non-small cell lung cancer (NSCLC). A very low frequency of PLK transcripts was only found in bronchiolo-alveolar carcinomas. NSCLC patients whose tumors showed moderate PLK expression survived significantly longer (5 year survival rate=51.8%) than those with high levels of PLK transcripts (24.2%, P=0.001). No statistically significant correlation was found between PLK mRNA expression and age, sex, TNM status, histological type or degree of differentiation. Interestingly, the prognosis of patients in post-surgical stages I and II was correlated with PLK expression (5 year survival rates in stage I: 69.1% (moderate PLK) - 43.5% (high PLK), P=0.03 or in stage II: 51.9% (moderate PLK) - 9.9% (high PLK), P=0.006). These results suggest that PLK mRNA expression provides a new independent prognostic indicator for patients with NSCLC.

An immunohistochemical analysis of antioxidant and glutathione S-transferase enzyme levels in normal and neoplastic human lung

Samples of normal human lung and six major types of human lung carcinomas were immunostained for antioxidant enzymes (manganese and copper, zinc superoxide dismutases, catalase, and glutathione peroxidase) and six isoenzymes of glutathione S-transferase staining was generally low in tumor cells compared with the high level of staining noted in respiratory epithelium. A notable exception was heterogeneity in immunostaining for manganese superoxide dismutase in lung adenocarcinoma, which showed both positive and negative cells in the same tumor. Tumor stromal cells (fibroblast-appearing cells) often showed strong immunostaining for manganese superoxide dismutase, while stromal cells were negative for other antioxidant and glutathione S-transferase enzymes. None of the carcinomas studied had significant levels of catalase or glutathione peroxidase; this finding has potential clinical relevance since it indicates that these tumors cannot detoxify hydrogen peroxide. The low levels of antioxidant and glutathione S-transferase enzymes in tumor cells is consistent with the hypothesis that these enzymes are markers of cell differentiation.

[Enzyme cytochemistry and morphometric study of the effects of macrophages on A549 pulmonary alveolar cell carcinoma cell line]

In order to study the mechanism of the effects of M phi on tumor cells, enzyme cytochemistry and morphometry were used to investigate the activities of cytochrome oxidase (CO), succinate dehydrogenase (SD), lactate dehydrogenase (LDH) and acid phosphatase (ACP) in A549 pulmonary alveolar cell carcinoma cells which had been interacted with normal and CP-activated macrophages respectively. It was found that when E/T = 10:1, the enzyme activity of the cancer cell mitochondria, CO, SD, LDH were decreased, and when E/T = 20:1, the activity of the lysosomal enzyme ACP was increased. These results indicate that when the E/T ratio was appropriate, activated M phi may injure the mitochondria and lysosomes and affect the aerobic respiration and oxidative phosphorylation of cancer cells. This may be one of the cytostatic and cytotoxic mechanisms of activated M phi on tumor cells.

Xenobiotic-metabolizing enzyme activity in human non-small-cell derived lung cancer cell lines

Human lung cancer cell lines in culture were investigated for the expression of monooxygenase and other xenobiotic-metabolizing enzyme activities. Two bronchiolo-alveolar carcinoma derived cell lines (NCI-H322 and NCI-H358) and two small-cell carcinoma derived cell lines (NCI-H128 and NCI-H69) were used. Previous work has shown that NCI-H322 has ultrastructural features of Clara cells while NCI-H358 shows characteristics of alveolar type II cells [Schuller et al., Proc. Am. Ass. Cancer Res. 26, 27 (1985)]. NCI-H128 and NCI-H69 show very poor differentiation of cytoplasmic organelles. Cytochrome P-450 levels were spectroscopically detectable only in NCI-H322. Both NCI-H322 and NCI-H358, but not NCI-H69 and NCI-H128, exhibited aryl hydrocarbon hydroxylase (using benzo[a] pyrene as substrate) and ethoxycoumarin O-deethylase activities. These activities were highly inducible following pretreatment with the polycyclic aromatic hydrocarbons (PAH) beta-naphthoflavone or benzo[a] anthracene. The PAH produced a 2-fold increase in spectroscopically detectable cytochrome P-450 levels in NCI-H322. Following induction, cytochrome P-450 was also spectroscopically detectable in NCI-H358. No aldrin epoxidase activity was present in either untreated or pretreated cell lines. Pretreatment with phenobarbitone or dexamethasone did not induce the aryl hydrocarbon hydroxylase activity in either NCI-H322 or NCI-H358. The ethoxycoumarin O-deethylase activity in beta-naphthoflavone-pretreated NCI-H322 and NCI-H358 was inhibited in a concentration-dependent manner by ellipticine, alpha-naphthoflavone, cimetidine or metyrapone. Untreated NCI-H322 and NCI-H358 also contained cytochrome b5, NADPH cytochrome c reductase and epoxide hydrolase activities. None of these enzyme activities measured was detectable in the untreated or pretreated small-cell derived cancer cell lines (NCI-H128 and NCI-H69). These data show that the two bronchiolo-alveolar carcinoma derived cell lines (NCI-H322 and NCI-H358) exhibit cytochrome P-448-dependent monooxygenase activity and may thus prove useful to study the processes of xenobiotic activation in human lung.

Dehydrogenase activity and loss of formazan from tissue sections

Formazans can be lost from tissue sections when the incubation medium is removed at the end of a dehydrogenase reaction. The loss is not uniform and will clearly affect the interpretation of results. This suggests that both the qualitative evaluation of the reaction and the measurement of enzyme activity should be made at the time of incubation.

Aryl hydrocarbon hydroxylase in persons with lung or laryngeal cancer

To test whether the distribution of AHH inducibility is shifted toward the high end of the range in patients who had lung and laryngeal cancer, we measured this trait in 59 patients (32 lung and 27 laryngeal) who had resectable tumors and had been disease-free for a period of time. The advantage of selecting patients who were free of clinical disease was that measurement of their AHH inducibility should not have been affected by the disease state. Patient and control populations showed no difference in basal and induced AHH activity of AHH inducibility. The mean AHH inducibility in patients who had lung cancer was 3.20 +/- 0.20; in patients who had laryngeal cancer 2.96 +/- 0.18, and for all controls 3.29 +/- 0.04 (no significant difference at p = 0 05). Further analysis of the distribution of AHH inducibility in the patient group compared to controls showed no suggestion of a shift toward the higher end of the range in patients who had lung and laryngeal cancer.

Salt-wasting bronchorrhea and its mechanisms

A 56-year old woman, with the diffuse form of bronchioloalveolar cell carcinoma, developed massive bronchorrhea, resulting in severe fluid and electrolyte depletion when her oral intake was compromised. Chemical analysis of the bronchial secretions and the ultrastructural features of the tumor cells support the concept of an active secretory process. The lactic dehydrogenase (LDH) isoenzyme pattern of the fluid is similar to that found in fetal cells. The neoplastic cells may acquire a more primitive LDH pattern.