Four human carcinoma cell lines with novel mutations in position 12 of c-K-ras oncogene

Intestinal transit-amplifying cells require METTL3 for growth factor signaling and cell survival

Intestinal epithelial transit-amplifying cells are essential stem progenitors required for intestinal homeostasis, but their rapid proliferation renders them vulnerable to DNA damage from radiation and chemotherapy. Despite these cells' critical roles in intestinal homeostasis and disease, few studies have described genes that are essential to transit-amplifying cell function. We report that RNA methyltransferase-like 3 (METTL3) is required for survival of transit-amplifying cells in the murine small intestine. Transit-amplifying cell death after METTL3 deletion was associated with crypt and villus atrophy, loss of absorptive enterocytes, and uniform wasting and death in METTL3-depleted mice. Sequencing of polysome-bound and methylated RNAs in enteroids and in vivo demonstrated decreased translation of hundreds of methylated transcripts after METTL3 deletion, particularly transcripts involved in growth factor signal transduction such as Kras. Further investigation verified a relationship between METTL3 and Kras methylation and protein levels in vivo. Our study identifies METTL3 as an essential factor supporting the homeostasis of small intestinal tissue via direct maintenance of transit-amplifying cell survival. We highlight the crucial role of RNA modifications in regulating growth factor signaling in the intestine with important implications for both homeostatic tissue renewal and epithelial regeneration.

MicroRNA-16 Restores Sensitivity to Tyrosine Kinase Inhibitors and Outperforms MEK Inhibitors in KRAS-Mutated Non-Small Cell Lung Cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) is the leading cause of cancer death worldwide. Chemotherapy, the treatment of choice in non-operable cases, achieves a dismal success rate, raising the need for new therapeutic options. In about 25% of NSCLC, the activating mutations of the KRAS oncogene define a subclass that cannot benefit from tyrosine kinase inhibitors (TKIs). The tumor suppressor miR-16 is downregulated in many human cancers, including NSCLC. The main objectives of this study were to evaluate miR-16 treatment to restore the TKI sensitivity and compare its efficacy to MEK inhibitors in KRAS-mutated NSCLC.

METHODS

We performed in vitro and in vivo studies to investigate whether miR-16 could be exploited to overcome TKI resistance in KRAS-mutated NSCLC. We had three goals: first, to identify the KRAS downstream effectors targeted by mir-16, second, to study the effects of miR-16 restoration on TKI resistance in KRAS-mutated NSCLC both in vitro and in vivo, and finally, to compare miR-16 and the MEK inhibitor selumetinib in reducing KRAS-mutated NSCLC growth in vitro and in vivo.

RESULTS

We demonstrated that miR-16 directly targets the three KRAS downstream effectors MAPK3, MAP2K1, and CRAF in NSCLC, restoring the sensitivity to erlotinib in KRAS-mutated NSCLC both in vitro and in vivo. We also provided evidence that the miR-16-erlotinib regimen is more effective than the selumetinib-erlotinib combination in KRAS-mutated NSCLC.

CONCLUSIONS

Our findings support the biological preclinical rationale for using miR-16 in combination with erlotinib in the treatment of NSCLC with KRAS-activating mutations.

Differential Action of Silver Nanoparticles on ABCB1 (MDR1) and ABCC1 (MRP1) Activity in Mammalian Cell Lines

Silver nanoparticles (AgNPs), due to their unique properties have been receiving immense attention in recent years. In addition to their antibacterial and antifungal activities, AgNPs also cause apoptosis, mitochondria disfunction, nucleic acid damage and show potent anticancer properties in both multidrug resistance (MDR) and sensitive tumors. The MDR phenomenon, caused by the presence of ATP-binding cassette (ABC) proteins, is responsible for the failure of chemotherapy. Thus, investigating the influence of widely used AgNPs on ABC transporters is crucial. In the present study, we have examined the cytotoxicity of silver nanoparticles of a nominal size of 20 nm (Ag20) on the cell lines of different tissue origins. In addition, we have checked the ATP-binding cassette transporters’ activity and expression under AgNP exposure. The results indicate that Ag20 shows a toxic effect on tested cells, as well as modulating the expression and transport activity of ABC proteins.

No erythropoietin-induced growth is observed in non-small cell lung cancer cells

Lung cancer patients have the highest incidence of anemia among patients with solid tumors. The use of recombinant human erythropoietin (Epo) has consistently been shown to reduce the need for blood transfusions and to increase hemoglobin levels in lung cancer patients with chemotherapy-induced anemia. However, clinical and preclinical studies have prompted concerns that Epo and the presence of its receptor, EpoR, in tumor cells may be responsible for adverse effects and, eventually, death. The question has been raised whether Epo promotes tumor growth and inhibits the death of cancer cells. In this study, we investigated the presence and functionality of EpoR, as well as the implications of Epo upon the proliferation and survival of lung cancer cells. Since the protein expression of both Epo and EpoR is induced by hypoxia, which is frequently present in lung cancer, the cells were treated with Epo under both normoxic and hypoxic conditions (1% O2). By using quantitative (real-time) PCR, western blot analysis, and immunocytochemical staining, three non-small cell lung cancer (NSCLC) cell lines (A427, A549 and NCI-H358) were analyzed for the expression of EpoR and its specific downstream signaling pathways [Janus kinase 2 (Jak2)-signal transducer and activator of transcription 5 (STAT5), phosphatidylinositol-3-kinase (PI3K)-Akt, mitogen-activated protein (MAP) kinase]. The effects of 100 U/ml Epo on cell proliferation and cisplatin-induced apoptosis were assessed. All NSCLC cell lines expressed EpoR mRNA and protein, while these levels differed considerably between the cell lines. We found the constitutive phosphorylation of EpoR and most of its downstream signaling pathways (STAT5, Akt and ERK1/2) independently of Epo administration. While Epo markedly enhanced the proliferation and reduced apoptosis of Epo-dependent UT-7/Epo leukemia cells, it did not affect tumor cell proliferation or the cisplatin-induced apoptosis of NSCLC cells. Thus, this in vitro study suggests that there are no tumor-promoting effects of Epo in the NSCLC cell lines studied, neither under normoxic nor under hypoxic conditions.

Differential Regulation of Gene Expression of Alveolar Epithelial Cell Markers in Human Lung Adenocarcinoma-Derived A549 Clones

Stem cell therapy appears to be promising for restoring damaged or irreparable lung tissue. However, establishing a simple and reproducible protocol for preparing lung progenitor populations is difficult because the molecular basis for alveolar epithelial cell differentiation is not fully understood. We investigated an in vitro system to analyze the regulatory mechanisms of alveolus-specific gene expression using a human alveolar epithelial type II (ATII) cell line, A549. After cloning A549 subpopulations, each clone was classified into five groups according to cell morphology and marker gene expression. Two clones (B7 and H12) were further analyzed. Under serum-free culture conditions, surfactant protein C (SPC), an ATII marker, was upregulated in both H12 and B7. Aquaporin 5 (AQP5), an ATI marker, was upregulated in H12 and significantly induced in B7. When the RAS/MAPK pathway was inhibited, SPC and thyroid transcription factor-1 (TTF-1) expression levels were enhanced. After treatment with dexamethasone (DEX), 8-bromoadenosine 3′5′-cyclic monophosphate (8-Br-cAMP), 3-isobutyl-1-methylxanthine (IBMX), and keratinocyte growth factor (KGF), surfactant protein B and TTF-1 expression levels were enhanced. We found that A549-derived clones have plasticity in gene expression of alveolar epithelial differentiation markers and could be useful in studying ATII maintenance and differentiation.

Adaptation of HepG2 cells to silver nanoparticles-induced stress is based on the pro-proliferative and anti-apoptotic changes in gene expression

Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials due to their antibacterial properties. Owing to the recent boost in the usage of AgNPs-containing products, human exposure to AgNPs is increasing, highlighting the need for careful evaluation of AgNPs toxicity in humans. We used two cellular models, hepatic HepG2 and epithelial A549 cell lines, to study the mechanism of AgNPs-induced toxicity at the cellular level. These two cell lines differ significantly in their response to AgNPs treatment. In the case of A549 cells, a minor decrease in viability and increase in the extent of DNA breakage were observed. A markedly different response to AgNPs was observed in HepG2 cells. In short term, a massive induction of DNA breakage was observed, suggesting that the basal activity of antioxidant defence in these cells was not sufficient to effectively protect them from the nanoparticle-induced oxidative stress. After prolonged exposure, the extent of DNA breakage decreased to the level observed in the control cells proving that a successful adaptation to the new conditions had taken place. The cells that were unable to adapt must have died, as revealed by the Neutral Red assay that indicated less than half viable cells after 24-h treatment with 100 µg/ml of 20nm AgNPs. The gene expression analysis revealed that the observed adaptation was underlain by a pro-proliferative, anti-apoptotic signal leading to up-regulation of the genes promoting proliferation and inflammatory response (EGR1, FOS, JUN, HK2, IL4, MMP10, VEGFA, WISP1, CEBPB, IL8, SELPLG), genes coding the anti-apoptotic proteins (BCL2A1, CCL2) and factors involved in the response to stress (HSPB1, GADD45A). Such a selection of highly resistant population of cells should be taken into account in the case of medical applications of nanoparticles since the sustained proliferative signalling and resistance to cell death are hallmarks of cancer, acquired by the cells in the process of carcinogenesis.

Redox processes inform multivariate transdifferentiation trajectories associated with TGFβ-induced epithelial-mesenchymal transition

Phenotype reprogramming during transforming growth factor β (TGFβ)-induced epithelial-mesenchymal transition (EMT) is an extensive and dynamic process, orchestrated by the integration of biological signaling across multiple time scales. As part of the numerous transcriptional changes necessary for EMT, TGFβ-initiated Smad3 signaling results in remodeling of the redox environment and decreased nucleophilic tone. Because Smad3 itself is susceptible to attenuated activity through antioxidants, the possibility of a positive feedback loop exists, albeit the time scales on which these mechanisms operate are quite different. We hypothesized that the decreased nucleophilic tone acquired during EMT promotes Smad3 signaling, enhancing acquisition and stabilization of the mesenchymal phenotype. Previous findings supporting such a mechanism were characterized independent of each other; we sought to investigate these relationships within a singular experimental context. In this study, we characterized multivariate representations of phenotype as they evolved over time, specifically measuring expression of epithelial/mesenchymal differentiation, redox regulators, and Smad transcription factors. In-cell Western (ICW) assays were developed to evaluate multivariate phenotype states as they developed during EMT. Principal component analysis (PCA) extracted anticorrelations between phospho-Smad3 (pSmad3) and Smad2/Smad4, which reflected a compensatory up-regulation of Smad2 and Smad4 following cessation of TGFβ signaling. Measuring transcript expression following EMT, we identified down-regulation of numerous antioxidant genes concomitant with up-regulation of NADPH oxidase 4 (NOX4) and multiple mesenchymal phenotype markers. TGFβ treatment increased CM-H2DCF-DA oxidation, decreased H2O2 degradation rates, and increased glutathione redox potential. Our findings suggest that the decreased nucleophilic tone during EMT coincides with the acquisition of a mesenchymal phenotype over too long a time scale to enable enhanced Smad3 phosphorylation during initiation of EMT. We further challenged the mesenchymal phenotype following EMT through antioxidant and TGFβ inhibitor treatments, which failed to induce a mesenchymal-epithelial transition (MET). Our characterization of multivariate phenotype dynamics during EMT indicates that the decrease in nucleophilic tone occurs alongside EMT; however, maintenance of the mesenchymal phenotype following EMT is independent of both the nascent redox state and the continuous TGFβ signaling.

E-cadherin-downregulation and RECK-upregulation are coupled in the non-malignant epithelial cell line MCF10A but not in multiple carcinoma-derived cell lines

Expression of a mesenchymal phenotype is often associated with invasive/metastatic behaviors of carcinoma cells. Acquisition of a mesenchymal phenotype by a carcinoma cell is known as epithelial-mesenchymal transition (EMT). The membrane-anchored matrix metalloproteinase-regulator RECK is abundant in normal mesenchymal cells. In aggressive carcinomas, however, RECK expression is often downregulated. This apparent paradox prompted us to clarify the relationship between EMT and RECK. We found that TGFβ-induced E-cadherin downregulation, a hallmark of EMT, is accompanied by RECK-upregulation in a non-tumorigenic epithelial cell line (MCF10A). In contrast, the loss of E-cadherin expression is uncoupled from RECK-upregulation in carcinoma-derived cell lines (MCF7, MDA-MB-231, and A549). When RECK was artificially expressed in A549 cells, it showed little effect on EMT but elevated the level of integrin α5 and attenuated cell proliferation and migration. These findings implicate RECK in the regulation of proliferation and migration of normal epithelial cells after EMT and suggest how the uncoupling between EMT and RECK-upregulation impacts on the fates and behaviors of carcinoma cells.

Silver nanoparticles induced changes in the expression of NF-κB related genes are cell type specific and related to the basal activity of NF-κB

Silver nanoparticles (AgNPs) are widely used in industry and medicine but the recent evidence for their cytotoxicity rise a concern about the safety of their use. We have previously shown that human A549 cells are resistant to AgNPs cytotoxicity, as compared with similarly treated HepG2 cells. In order to check for the role of the NF-κB signaling pathway in response of A549 and HepG2 cell lines to the treatment with 20 nm and 200 nm AgNps, we analyzed the expression of 84 key genes related to the functionality of the NF-κB signaling pathway. We observed considerable alternations in gene expression in HepG2 cells treated with 20 nm AgNPs, and minor changes when exposed to 200 nm AgNPs. Surprisingly, no changes in gene expression were observed in A549 cells treated with both size AgNPs. Using the NF-κB luciferase reporter system, we further tested the basal activity and inducibility of the NF-κB pathway in both cell lines and found that the inducibility of NF-κB signaling in A549 cells is approximately 5 times lower than this of HepG2 cells, but the basal activity is approximately 3.5 times higher. In accordance, the NF-κB activation after AgNPs treatment was observed in HepG2 but not in A549. Altogether indicate that NF-kB mediated cellular response to AgNPs is cell type specific and related to the basal activity of NF-κB.

The proto-oncogene KRAS is targeted by miR-200c

The GTPase K-ras is involved in a variety of cellular processes such as differentiation, proliferation and survival. However, activating mutations, which frequently occur in many types of cancer, turn KRAS into one of the most prominent oncogenes. Likewise, miR-200c is a key player in tumorigenesis functioning as a molecular switch between an epithelial, non-migratory, chemosensitive and a mesenchymal, migratory, chemoresistant state. While it has been reported that KRAS is modulated by several tumor suppressor miRNAs, this is the first report on the regulation of KRAS by miR-200c, both playing a pivotal role in oncogenesis. We show that KRAS is a predicted target of miR-200c and that the protein expression of KRAS inversely correlates with the miR-200c expression in a panel of human breast cancer cell lines. KRAS was experimentally validated as a target of miR-200c by Western blot analyses and luciferase reporter assays. Furthermore, the inhibitory effect of miR-200c-dependent KRAS silencing on proliferation and cell cycle was demonstrated in different breast and lung cancer cell lines. Thereby, the particular role of KRAS was dissected from the role of all the other miR-200c targets by specific knockdown experiments using siRNA against KRAS. Cell lines harboring an activating KRAS mutation were similarly affected by miR-200c as well as by the siRNA against KRAS. However, in a cell line with wild-type KRAS only miR-200c was able to change proliferation and cell cycle. Our findings suggest that miR-200c is a potent inhibitor of tumor progression and therapy resistance, by regulating a multitude of oncogenic pathways including the RAS pathway. Thus, miR-200c may cause stronger anti-tumor effects than a specific siRNA against KRAS, emphasizing the potential role of miR-200c as tumor suppressive miRNA.

Oncolytic bluetongue viruses: promise, progress, and perspectives

Humans are sero-negative toward bluetongue viruses (BTVs) since BTVs do not infect normal human cells. Infection and selective degradation of several human cancer cell lines but not normal ones by five US BTV serotypes have been investigated. We determined the susceptibilities of many normal and human cancer cells to BTV infections and made comparative kinetic analyses of their cytopathic effects, survival rates, ultra-structural changes, cellular apoptosis and necrosis, cell cycle arrest, cytokine profiles, viral genome, mRNAs, and progeny titers. The wild-type US BTVs, without any genetic modifications, could preferentially infect and degrade several types of human cancer cells but not normal cells. Their selective and preferential BTV-degradation of human cancer cells is viral dose–dependent, leading to effective viral replication, and induced apoptosis. Xenograft tumors in mice were substantially reduced by a single intratumoral BTV injection in initial in vivo experiments. Thus, wild-type BTVs, without genetic modifications, have oncolytic potentials. They represent an attractive, next generation of oncolytic viral approach for potential human cancer therapy combined with current anti-cancer agents and irradiation.

Liposomal delivery of MicroRNA-7-expressing plasmid overcomes epidermal growth factor receptor tyrosine kinase inhibitor-resistance in lung cancer cells

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) have been strikingly effective in lung cancers harboring activating EGFR mutations. Unfortunately, the cancer cells eventually acquire resistance to EGFR-TKI. Approximately 50% of the acquired resistance involves a secondary T790M mutation. To overcome the resistance, we focused on EGFR suppression using microRNA-7 (miR-7), targeting multiple sites in the 3'-untranslated region of EGFR mRNA. Two EGFR-TKI-sensitive cell lines (PC-9 and H3255) and two EGFR-TKI-resistant cell lines harboring T790M (RPC-9 and H1975) were used. We constructed miR-7-2 containing miR-7-expressing plasmid. After transfection of the miR-7-expressing plasmid, using cationic liposomes, a quantitative PCR and dual luciferase assay were conducted to examine the efficacy. The antiproliferative effect was evaluated using a cell count assay and xenograft model. Protein expression was examined by Western blotting. The miR-7 expression level of the transfectants was approximately 30-fold higher, and the luciferase activity was ablated by 92%. miR-7 significantly inhibited cell growth not only in PC-9 and H3255 but also in RPC-9 and H1975. Expression of insulin receptor substrate-1 (IRS-1), RAF-1, and EGFR was suppressed in the four cell lines. Injection of the miR-7-expressing plasmid revealed marked tumor regression in a mouse xenograft model using RPC-9 and H1975. EGFR, RAF-1, and IRS-1 were suppressed in the residual tumors. These findings indicate promising therapeutic applications of miR-7-expressing plasmids against EGFR oncogene-addicted lung cancers including T790M resistance by liposomal delivery.

Lovastatin sensitizes lung cancer cells to ionizing radiation: modulation of molecular pathways of radioresistance and tumor suppression

INTRODUCTION

In this study, we investigated the effect of the 3-hydroxy-3-methylgutaryl-CoA reductase inhibitor lovastatin, as a sensitizer of lung cancer cells to ionizing radiation (IR).

METHODS

A549 lung adenocarcinoma cells were treated with 0 to 50 μM lovastatin alone or in combination with 0 to 8 Gy IR and subjected to clonogenic survival and proliferation assays. To assess the mechanism of drug action, we examined the effects of lovastatin and IR on the epidermal growth factor (EGF) receptor and AMP-activated kinase (AMPK) pathways and on apoptotic markers and the cell cycle.

RESULTS

Lovastatin inhibited basal clonogenic survival and proliferation of A549 cells and sensitized them to IR. This was reversed by mevalonate, the product of 3-hydroxy-3-methylgutaryl-CoA reductase. Lovastatin attenuated selectively EGF-induced phosphorylation of EGF receptor and Akt, and IR-induced Akt phosphorylation, in a mevalonate-sensitive fashion, without inhibition on extracellular signal-regulated kinase 1/2 phosphorylation by either stimulus. IR phosphorylated and activated the metabolic sensor and tumor suppressor AMPK, but lovastatin enhanced basal and IR-induced AMPK phosphorylation. The drug inhibited IR-induced expression of p53 and the cyclin-dependent kinase inhibitors p21(cip1) and p27(kip1), but caused a redistribution of cells from G1-S phase (control and radiated cells) and G2-M phase (radiated cells) of cell cycle into apoptosis. The latter was also evident by induction of nuclear fragmentation and cleavage of caspase 3 by lovastatin in both control and radiated cells.

CONCLUSIONS

We suggest that lovastatin inhibits survival and induces radiosensitization of lung cancer cells through induction of apoptosis, which may be mediated by a simultaneous inhibition of the Akt and activation of the AMPK signaling pathways.

Acute high-dose X-radiation-induced genomic changes in A549 cells

Accidents with ionizing radiation often involve single, acute high-dose exposures that can lead to acute radiation syndrome and late effects such as carcinogenesis. To study such effects at the cellular level, we investigated acute ionizing radiation-induced chromosomal aberrations in A549 adenocarcinoma cells at the genome-wide level by exposing the cells to an acute dose of 6 Gy 240 kV X rays. One sham-irradiated clone and four surviving irradiated clones were recovered by minimal dilution and further expanded and analyzed by chromosome painting and tiling-path array CGH, with the nonirradiated clone 0 serving as the control. Acute X-ray exposure induced specific translocations and changes in modal chromosome number in the four irradiated clones. Array CGH disclosed unique and recurrent genomic changes, predominantly losses, and revealed that the fragile sites FRA3B and FRA16D were preferential regions of genomic alterations in all irradiated clones, which is likely related to radioresistant S-phase progression and genomic stress. Furthermore, clone 4 displayed an increased radiosensitivity at doses >5 Gy. Pairwise comparisons of the gene expression patterns of all irradiated clones to the sham-irradiated clone 0 revealed an enrichment of the Gene Ontology term "M Phase" (P = 6.2 × 10(-7)) in the set of differentially expressed genes of clone 4 but not in those of clones 1-3. Ionizing radiation-induced genomic changes and fragile site expression highlight the capacity of a single acute radiation exposure to affect the genome of exposed cells by inflicting genomic stress.

Hypoxia in models of lung cancer: implications for targeted therapeutics

PURPOSE

To efficiently translate experimental methods from bench to bedside, it is imperative that laboratory models of cancer mimic human disease as closely as possible. In this study, we sought to compare patterns of hypoxia in several standard and emerging mouse models of lung cancer to establish the appropriateness of each for evaluating the role of oxygen in lung cancer progression and therapeutic response.

EXPERIMENTAL DESIGN

Subcutaneous and orthotopic human A549 lung carcinomas growing in nude mice as well as spontaneous K-ras or Myc-induced lung tumors grown in situ or subcutaneously were studied using fluorodeoxyglucose and fluoroazomycin arabinoside positron emission tomography, and postmortem by immunohistochemical observation of the hypoxia marker pimonidazole. The response of these models to the hypoxia-activated cytotoxin PR-104 was also quantified by the formation of γH2AX foci in vitro and in vivo. Finally, our findings were compared with oxygen electrode measurements of human lung cancers.

RESULTS

Minimal fluoroazomycin arabinoside and pimonidazole accumulation was seen in tumors growing within the lungs, whereas subcutaneous tumors showed substantial trapping of both hypoxia probes. These observations correlated with the response of these tumors to PR-104, and with the reduced incidence of hypoxia in human lung cancers relative to other solid tumor types.

CONCLUSIONS

These findings suggest that in situ models of lung cancer in mice may be more reflective of the human disease, and encourage judicious selection of preclinical tumor models for the study of hypoxia imaging and antihypoxic cell therapies.

Increased cell migration and plasticity in Nrf2-deficient cancer cell lines

Nuclear Factor (erythroid-derived 2)-like 2 (Nrf2) expression is deregulated in many cancers. Genetic and biochemical approaches coupled with functional assays in cultured cells were used to explore the consequence of Nrf2 repression. Nrf2 suppression by Keap1-directed ubiquitylation or expression of independent shRNA/siRNA sequences enhanced cellular ROS, Smad-dependent tumor cell motility, and growth in soft agar. Loss of Nrf2 was accompanied by concomitant Smad linker region/C-terminus phosphorylation, induction of the E-Cadherin transcriptional repressor Slug, and suppression of the cell-cell adhesion protein E-Cadherin. Ectopic expression of wildtype Nrf2, but not dominant negative Nrf2, suppressed the activity of a synthetic TGF-β1 responsive CAGA-directed luciferase reporter. shRNA knock-down of Nrf2 enhanced the activity of the synthetic CAGA-reporter, as well as the expression of the endogenous Smad target gene plasminogen activator inhibitor-1. Finally, we found that Nrf2/Smad3/Smad4 formed an immunoprecipitable nuclear complex. Thus, loss of Nrf2 increased R-Smad phosphorylation and R-Smad signaling, supporting the hypothesis that loss of Nrf2 in an oncogenic context-dependent manner can enhance cellular plasticity and motility, in part by using TGF-β/Smad signaling.

The CRAL/TRIO and GOLD domain protein TAP-1 regulates RAF-1 activation

The activation of the protein kinase Raf at the cell membrane is a critical step in cell signaling during development, but the mechanisms that regulate Raf activity remain incompletely defined. We previously demonstrated that the C. elegans cgr-1 gene encodes a CRAL/TRIO domain-containing protein that is a critical modulator of Ras-dependent cell fate specification during C. elegans development. Here we identify the mammalian alpha-tocopherol associated protein-1 (TAP-1) as a functional ortholog of cgr-1. TAP-1 mRNA was expressed in many tissues, and TAP-1 protein colocalized with Ras and Raf at the cell membrane. Reducing TAP-1 expression by RNA interference increased Ras/ERK signaling in multiple cell types. These functional studies demonstrate that CRAL/TRIO domain proteins play a conserved role in regulating Ras signaling. Biochemical analyses indicated that TAP-1 operates at the level of Raf, since TAP-1 function negatively regulated the amount of Raf-1 recruited to GTP-bound Ras at the cell membrane. TAP-1 plays a significant physiological role in controlling cell division, since reducing TAP-1 expression increased the oncogenic capacity of Ras transformed human cancer cell lines. These studies identify TAP-1 as a critical modulator of Ras-mediated cellular signaling.

Human cancers converge at the HIF-2alpha oncogenic axis

Cancer development is a multistep process, driven by a series of genetic and environmental alterations, that endows cells with a set of hallmark traits required for tumorigenesis. It is broadly accepted that growth signal autonomy, the first hallmark of malignancies, can be acquired through multiple genetic mutations that activate an array of complex, cancer-specific growth circuits [Hanahan D, Weinberg RA (2000) The hallmarks of cancer. Cell 100:57-70; Vogelstein B, Kinzler KW (2004) Cancer genes and the pathways they control. Nat Med 10:789-799]. The superfluous nature of these pathways is thought to severely limit therapeutic approaches targeting tumor proliferation, and it has been suggested that this strategy be abandoned in favor of inhibiting more systemic hallmarks, including angiogenesis (Ellis LM, Hicklin DJ (2008) VEGF-targeted therapy: Mechanisms of anti-tumor activity. Nat Rev Cancer 8:579-591; Stommel JM, et al. (2007) Coactivation of receptor tyrosine kinases affects the response of tumor cells to targeted therapies. Science 318:287-290; Kerbel R, Folkman J (2002) Clinical translation of angiogenesis inhibitors. Nat Rev Cancer 2:727-739; Kaiser J (2008) Cancer genetics: A detailed genetic portrait of the deadliest human cancers. Science 321:1280-1281]. Here, we report the unexpected observation that genetically diverse cancers converge at a common and obligatory growth axis instigated by HIF-2alpha, an element of the oxygen-sensing machinery. Inhibition of HIF-2alpha prevents the in vivo growth and tumorigenesis of highly aggressive glioblastoma, colorectal, and non-small-cell lung carcinomas and the in vitro autonomous proliferation of several others, regardless of their mutational status and tissue of origin. The concomitant deactivation of select receptor tyrosine kinases, including the EGFR and IGF1R, as well as downstream ERK/Akt signaling, suggests that HIF-2alpha exerts its proliferative effects by endorsing these major pathways. Consistently, silencing these receptors phenocopies the loss of HIF-2alpha oncogenic activity, abrogating the serum-independent growth of human cancer cells in culture. Based on these data, we propose an alternative to the predominant view that cancers exploit independent autonomous growth pathways and reveal HIF-2alpha as a potentially universal culprit in promoting the persistent proliferation of neoplastic cells.

Up-regulation of integrin expression in lung adenocarcinoma cells caused by bacterial infection: in vitro study

Integrins are a large family of adhesion receptors that are known to be key signaling molecules in both physiological and pathological processes. Previous studies have demonstrated that the expression of integrin receptors in the pulmonary epithelium can change under various pathological conditions, such as injury, inflammation, or malignant transformation. We hypothesize that integrin expression can be altered by stimulation of lung epithelial cells with an opportunistic bacterial pathogen Pseudomonas aeruginosa. Using the A549 adenocarcinoma cell line that expressed a low level of several integrin subunits we have demonstrated that P. aeruginosa infection in vitro caused a rapid up-regulation of α5, αv, β1, and β4 integrins at both the mRNA and protein level. Neither heat-killed P. aeruginosa strain PAK nor its live isogenic mutants lacking pili or lipopolysaccharide (LPS) core oligosaccharide showed any effect on integrin expression in A549 cells as compared to the use of the wild-type PAK strain. These results establish that up-regulation of integrin expression is dependent on the internalization of live bacteria possessing intact pili and LPS. Gene silencing of integrin-linked kinase in A549 cells caused a significant decrease in the release of proinflammatory cytokines in response to P. aeruginosa stimulation. Although further studies are warranted towards understanding the precise role of integrin receptors in prominent inflammation caused by P. aeruginosa, our findings suggest a possibility of using specific integrin inhibitors for therapy of pulmonary inflammatory conditions caused by pathogenic micro-organisms.

Selective in vitro cytotoxic effect of human cancer cells by bluetongue virus-10

Bluetongue viruses (BTVs) infect primarily domestic cattle and wild ruminants but have never been shown to infect normal human cells. Thus, humans are sero-negative towards BTVs. The selective and differential effects of BTV serotype 10 (BTV-10) infection were investigated with five cell lines including primary human embryo lung fibroblast (HEL) and primary murine embryos fibroblast(MEF), human hepatic carcinoma 3B cell line (Hep-3B), human lung carcinoma cell line (A549) and mouse fibroblast cell line (NIH 3T3). In this study, comparative analyses of differential cytopathic effects (CPEs), survival rates using different Multiplicities of Infection (MOI), ultra-structural changes by transmission electron microscopy, and the preferential cell cycle changes of infected cells by flow cytometry were made among these cells. Detection of the presence of BTV genome and kinetic analysis of virus titers in TCID50 were also made. We provided the first analytical demonstration and evidence that BTV-10 could selectively infect and degrade human cancer cells but not cultured primary normal cells. No CPE or viral mRNAs could be detected within these normal cells, while various degrees of CPE could be found in Hep-3B and A549, as well as in NIH 3T3 under similar conditions. Before death, BTV-infected human cancer cells were directly arrested in the sub-G1 phase and the diversity of BTV infection as shown by the MTT method had significant difference (F = 95.635, p < 0.01). Above results suggested that this viral dose-dependent cytotoxic effect is caused by both effective virion amplification and induced apoptosis. Cellular distinctive transformation status may contribute to the selectivity. Thus, selective degradation of human cancer cells but not normal diploid cells by the newly discovered oncolytic potential of BTV would provide a very attractive approach for cancer therapy in the future.

Absence of GAPDH regulation in tumor-cells of different origin under hypoxic conditions in - vitro

Background

Gene expression studies related to cancer diagnosis and treatment are important. In order to conduct such experiment accurately, absolutely reliable housekeeping genes are essential to normalize cancer related gene expression. The most important characteristics of such genes are their presence in all cells and their expression levels remain relatively constant under different experimental conditions. However, no single gene of this group of genes manifests always stable expression levels under all experimental conditions. Incorrect choice of housekeeping genes leads to interpretation errors of experimental results including evaluation and quantification of pathological gene expression. Here, we examined (a) the degree of GAPDH expression regulation in Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines as well as in human lung adenocarcinoma epithelial cell line (A-549) in addition to both HT-29, and HCT-116 colon cancer cell lines, under hypoxic conditions in vitro in comparison to other housekeeping genes like β-actin, serving as experimental loading controls, (b) the potential use of GAPDH as a target for tumor therapeutic approaches was comparatively examined in vitro on both protein and mRNA level, by western blot and semi quantitative RT-PCR, respectively.

Findings

No hypoxia-induced regulatory effect on GAPDH expression was observed in the cell lines studied in vitro that were; Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines, Human lung adenocarcinoma epithelial cell line (A-549), both colon cancer cell lines HT-29, and HCT-116.

Conclusion

As it is the case for human hepatocellular carcinoma, mouse hepatoma, human colon cancer, and human lung adenocarcinoma, GAPDH represents an optimal choice of a housekeeping gene and/(or) loading control to determine the expression of hypoxia induced genes in tumors of different origin. The results confirm our previous findings in human glioblastoma that this gene is not an attractive target for tumor therapeutic approaches because of the lack of GAPDH regulation under hypoxia.

BRAF V600E disrupts AZD6244-induced abrogation of negative feedback pathways between extracellular signal-regulated kinase and Raf proteins

AZD6244 (ARRY 142886) is a potent and selective mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor currently in early clinical trials. We examined the activity of AZD6244 in a panel of non-small cell lung cancer and a panel of cell lines representing many cancer types using in vitro growth assays. AZD6244 induced G(0)-G(1) cell cycle arrest in sensitive cell lines that primarily included cells containing the BRAF V600E mutation. In these cells, G(0)-G(1) arrest is accompanied by the up-regulation of the cell cycle inhibitors p21(WAF1) and p27(Kip1) and down-regulation of cyclin D1. In the majority of cell lines tested, including those with K-ras or non-V600E BRAF mutations, AZD6244 induced the accumulation of phospho-MEK, an effect not observed in the most sensitive BRAF V600E-containing cells. Accumulation of phospho-MEK in non-V600E-containing cell lines is due to abrogation of negative feedback pathways. BRAF V600E disrupts negative feedback signaling, which results in enhanced baseline phospho-MEK expression. Exogenous expression of BRAF V600E disrupts feedback inhibition but does not sensitize cells to AZD6244. Specific suppression of endogenous BRAF V600E does not confer resistance to AZD6244 but enhances sensitivity to AZD6244. Thus, our findings show that BRAF V600E marks cells with an in vitro requirement for MAPK signaling to support proliferation. These cells are exquisitely sensitive to AZD6244 (IC(50), <100 nmol/L), have high baseline levels of phospho-MEK, and lack feedback inhibition between ERK and Raf. These data suggest an approach to identifying cells that may be sensitive to AZD6244 and other MEK inhibitors.

K-ras mutations in sinonasal cancers in relation to wood dust exposure

Background

Cancer in the sinonasal tract is rare, but persons who have been occupationally exposed to wood dust have a substantially increased risk. It has been estimated that approximately 3.6 million workers are exposed to inhalable wood dust in EU. In previous small studies of this cancer, ras mutations were suggested to be related to wood dust exposure, but these studies were too limited to detect statistically significant associations.

Methods

We examined 174 cases of sinonasal cancer diagnosed in Denmark in the period from 1991 to 2001. To ensure uniformity, all histological diagnoses were carefully reviewed pathologically before inclusion. Paraffin embedded tumour samples from 58 adenocarcinomas, 109 squamous cell carcinomas and 7 other carcinomas were analysed for K-ras codon 12, 13 and 61 point mutations by restriction fragment length polymorphisms and direct sequencing. Information on occupational exposure to wood dust and to potential confounders was obtained from telephone interviews and from registry data.

Results

Among the patients in this study, exposure to wood dust was associated with a 21-fold increased risk of having an adenocarcinoma than a squamous cell carcinoma compared to unexposed [OR = 21.0, CI = 8.0–55.0]. K-ras was mutated in 13% of the adenocarcinomas (seven patients) and in 1% of squamous cell carcinomas (one patient). Of these eight mutations, five mutations were located in the codon 12. The exact sequence change of remaining three could not be identified unambiguously. Among the five identified mutations, the G→A transition was the most common, and it was present in tumour tissue from two wood dust exposed adenocarcinoma patients and one patient with unknown exposure. Previously published studies of sinonasal cancer also identify the GGT → GAT transition as the most common and often related to wood dust exposure.

Conclusion

Patients exposed to wood dust seemed more likely to develop adenocarcinoma compared to squamous cell carcinomas. K-ras mutations were detected in 13% of adenocarcinomas. In this study and previously published studies of sinonasal cancer the found K-ras mutations, were almost exclusively G → A transitions. In conclusion, our study, based on a large representative collection of human SNC tumours, indicates that K-ras mutations are relatively infrequent, and most commonly occur in adenocarcinomas. Wood dust exposure alone was not found to be explanatory for the G→A mutations, but combination of exposure to tobacco, wood dust, and possibly other occupational agents may be a more likely explanation. Overall, the study suggests a limited role for K-ras mutations in development of sinonasal cancer.

MicroRNAs as potential agents to alter resistance to cytotoxic anticancer therapy

Tumor cells use preexisting prosurvival signaling pathways to evade the damaging and cytotoxic effects of anticancer agents. Radiation therapy is a primary form of cytotoxic anticancer treatment, but agents that successfully modify the radiation response in vivo are lacking. MicroRNAs (miRNA) are global gene regulators that play critical roles in oncogenesis and have been found to regulate prosurvival pathways. However, there is little understanding of how cellular miRNA expression affects the response of a cancer to cytotoxic therapy and ultimately outcome. The let-7 family of miRNAs regulates expression of oncogenes, such as RAS, and is specifically down-regulated in many cancer subtypes. In fact, low levels of let-7 predict a poor outcome in lung cancer. Here, we report that the let-7 family of miRNAs is overrepresented in a class of miRNAs exhibiting altered expression in response to radiation. More strikingly, we also can create a radiosensitive state when the select let-7 family of miRNAs is overexpressed in vitro in lung cancer cells and in vivo in a Caenorhabditis elegans model of radiation-induced cell death, whereas decreasing their levels causes radioresistance. In C. elegans, we show that this is partly through control of the proto-oncogene homologue let-60/RAS and genes in the DNA damage response pathway. These findings are the first direct evidence that miRNAs can suppress resistance to anticancer cytotoxic therapy, a common feature of cancer cells, and suggest that miRNAs may be a viable tool to augment current cancer therapies.

Expression profiling of genes regulated by TGF-beta: differential regulation in normal and tumour cells

Background

TGF-beta is one of the key cytokines implicated in various disease processes including cancer. TGF-beta inhibits growth and promotes apoptosis in normal epithelial cells and in contrast, acts as a pro-tumour cytokine by promoting tumour angiogenesis, immune-escape and metastasis. It is not clear if various actions of TGF-beta on normal and tumour cells are due to differential gene regulations. Hence we studied the regulation of gene expression by TGF-beta in normal and cancer cells.

Results

Using human 19 K cDNA microarrays, we show that 1757 genes are exclusively regulated by TGF-beta in A549 cells in contrast to 733 genes exclusively regulated in HPL1D cells. In addition, 267 genes are commonly regulated in both the cell-lines. Semi-quantitative and real-time qRT-PCR analysis of some genes agrees with the microarray data. In order to identify the signalling pathways that influence TGF-beta mediated gene regulation, we used specific inhibitors of p38 MAP kinase, ERK kinase, JNK kinase and integrin signalling pathways. The data suggest that regulation of majority of the selected genes is dependent on at least one of these pathways and this dependence is cell-type specific. Interestingly, an integrin pathway inhibitor, RGD peptide, significantly affected TGF-beta regulation of Thrombospondin 1 in A549 cells.

Conclusion

These data suggest major differences with respect to TGF-beta mediated gene regulation in normal and transformed cells and significant role of non-canonical TGF-beta pathways in the regulation of many genes by TGF-beta.

Targeting ADAM-mediated ligand cleavage to inhibit HER3 and EGFR pathways in non-small cell lung cancer

We describe here the existence of a heregulin-HER3 autocrine loop, and the contribution of heregulin-dependent, HER2-mediated HER3 activation to gefitinib insensitivity in non-small cell lung cancer (NSCLC). ADAM17 protein, a major ErbB ligand sheddase, is upregulated in NSCLC and is required not only for heregulin-dependent HER3 signaling, but also for EGFR ligand-dependent signaling in NSCLC cell lines. A selective ADAM inhibitor, INCB3619, prevents the processing and activation of multiple ErbB ligands, including heregulin. In addition, INCB3619 inhibits gefitinib-resistant HER3 signaling and enhances gefitinib inhibition of EGFR signaling in NSCLC. These results show that ADAM inhibition affects multiple ErbB pathways in NSCLC and thus offers an excellent opportunity for pharmacological intervention, either alone or in combination with other drugs.

Ras transformation requires metabolic control by 6-phosphofructo-2-kinase

Neoplastic cells transport large amounts of glucose in order to produce anabolic precursors and energy within the inhospitable environment of a tumor. The ras signaling pathway is activated in several cancers and has been found to stimulate glycolytic flux to lactate. Glycolysis is regulated by ras via the activity of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatases (PFK2/FBPase), which modulate the intracellular concentration of the allosteric glycolytic activator, fructose-2,6-bisphosphate (F2,6BP). We report herein that sequential immortalization and ras-transformation of mouse fibroblasts or human bronchial epithelial cells paradoxically decreases the intracellular concentration of F2,6BP. This marked reduction in the intracellular concentration of F2,6BP sensitizes transformed cells to the antimetabolic effects of PFK2/FBPase inhibition. Moreover, despite co-expression of all four mRNA species (PFKFB1-4), heterozygotic genomic deletion of the inducible PFKFB3 gene in ras-transformed mouse lung fibroblasts suppresses F2,6BP production, glycolytic flux to lactate, and growth as soft agar colonies or tumors in athymic mice. These data indicate that the PFKFB3 protein product may serve as an essential downstream metabolic mediator of oncogenic ras, and we propose that pharmacologic inhibition of this enzyme should selectively suppress the high rate of glycolysis and growth by cancer cells.

Targeted covalent inactivation of protein kinases by resorcylic acid lactone polyketides

Resorcylic acid lactones containing a cis-enone are susceptible to Michael addition reactions and are potent inhibitors of several protein kinases. A structural-bioinformatics analysis identified a conserved Cys residue in the ATP-binding site of the kinases reported to be inhibited by cis-enone resorcylic acid lactones but absent in those that are not. Mining of the kinome database revealed that a subset of some 46 kinases contained this Cys residue. Screening a panel of 124 kinases with the resorcylic acid lactone hypothemycin showed that 18 of 19 targets containing the conserved Cys were inhibited. Kinetic analyses showed time-dependent inhibition, a hallmark of covalent inactivation, and biochemical studies of the interaction of extracellular signal-regulated kinase (ERK)2 with hypothemycin confirmed covalent adduct formation. Resorcylic acid lactones are unique among kinase inhibitors in that they target mitogen-activated protein (MAP) kinase pathways at four levels: mitogen receptors, MAP kinase kinase (MEK)1/2 and ERK1/2, and certain downstream ERK substrates. Cell lines dependent on the activation of Tyr kinase mitogen receptor targets of the resorcylic acid lactones were unusually sensitive toward hypothemycin and showed the expected inhibition of kinase phosphorylation due to inhibition of the mitogen receptors and/or MEK1/2 and ERK1/2. Among cells without mitogen receptor targets, those harboring an ERK pathway-activating B-RAF V600E mutation were selectively and potently inhibited by hypothemycin. Hypothemycin also prevented stimulated activation of the p38 cascade through inhibition of the Cys-containing targets MEK3/6 and TGF-beta-activated kinase 1 and of the JNK/SAPK (c-Jun N-terminal kinase/stress-activated protein kinase) cascade through inhibition of MEK4/7.

Allelic effects of mouse Pas1 candidate genes in human lung cancer cell lines

Four of the six genes constituting the mouse Pulmonary adenoma susceptibility 1 (Pas1) locus haplotype carry amino acid variants: Lrmp, Casc1, Ghiso, and Lmna-rs1. In vitro colony formation assay of human lung cancer cell lines A549 and NCI-H520 transfected with the allelic variants of the four genes revealed allele-specific modulations of colony numbers by Lmna-rs1 and Casc1, but not by Lrmp or Ghiso. In A549 and NCI-H520 cells, the A/J allele of Lmna-rs1 produced approximately 4- and approximately 2-fold, respectively, more transfectants than did the C57BL/6J allele, whereas the A/J allele of Casc1 produced approximately 6- and approximately 5-fold fewer transfectants, respectively, as compared to the C57BL/6J allele. Inhibition of clonogenicity by allelic forms of Pas1 candidate genes was not mediated by induction of apoptosis. These findings provide evidence that allelic variants of mouse Pas1 candidate genes differentially modulate growth of human cancer cells.

The growth and tumor suppressor NORE1A is a cytoskeletal protein that suppresses growth by inhibition of the ERK pathway

NORE1A is a growth and tumor suppressor that is inactivated in a variety of cancers. NORE1A has been shown to bind to the active Ras oncogene product. However, the mechanism of NORE1A-induced growth arrest and tumor suppression remains unknown. Using anchorage-independent growth assays, we mapped the NORE1A effector domain (the minimal region of the protein responsible for its growth-suppressive effects) to the fragment containing the central and Ras association domains of NORE1A (amino acids 191-363). Expression of the NORE1A effector domain in A549 lung adenocarcinoma cells resulted in the selective inhibition of signal transduction through the ERK pathway. The full-length NORE1A (416 amino acids) and its fragments capable of growth suppression were localized to centrosomes and microtubules in normal and transformed human cells in a Ras-independent manner. A mutant that was deficient in binding to centrosomes and microtubules was also deficient in inducing cell cycle arrest. This suggests that cytoskeletal localization is required for growth-suppressive effects of NORE1A. Ras binding function was required for growth-suppressive effects of the full-length NORE1A but not for the growth-suppressive effects of the effector domain. Our studies suggest that association of NORE1A with cytoskeletal elements is essential for NORE1A-induced growth suppression and that the ERK pathway is a target for NORE1A growth-suppressive activities.

Laminin 5 expression protects against anoikis at aerogenous spread and lepidic growth of human lung adenocarcinoma

Adenocarcinoma of the lung is characterized by frequent aerogenous spread (AE) and advancement along the alveolar wall (BAC growth). To elucidate the mechanism of AE metastasis and BAC growth in human lung adenocarcinoma, we established an in vivo orthotopic animal model and an in vitro culture. Investigation of expression levels of integrins, laminins and Type IV collagens, which are the major regulating molecules for cell attachment and anoikis was carried out and a clear correlation between the expression level of laminin 5 (LN5) and the BAC growth was observed using an orthotopic animal model. Introduction of LN5 cDNA to A549 cells increased anoikis resistance in an expression dependent manner. Cells with LN5 overexpression resisted with anoikis after treatment with PI3K-Akt and ERK inhibitors. The amount of phosphorylated focal adhesion kinase (FAK) was also higher in LN5 overexpressing cells. Major tyrosine residues of the EGF receptor at 1068, 1086 and 1173, except at 1148, remained phosphorylated only in the LN5 overexpressing cells even without EGF stimulation, that indicates the ligand independent activation of EGF receptor. BAC growth ratio and AE was confirmed to be significantly correlated with LN5 expression in surgically resected human lung adenocarcinomas by immunohistochemistry. Our results indicate that the activation of the EGF receptor by overexpressing LN5-integrin-FAK signaling pathway may play a crucial role in BAC growth and AE metastasis in human lung adenocarcinoma.

Fluoride-induced apoptosis in human epithelial lung cells (A549 cells): role of different G protein-linked signal systems

In the present study, possible mechanisms involved in fluoride-induced apoptosis in a human epithelial lung cell line (A549) were examined. Sodium fluoride (NaF) induced apoptosis in the A549 cells, with a maximum at 5-7.5 mM after 20 hours of exposure. The number of cells with plasma membrane damage (PI-positive cells) increased moderately up to 5 mM, but markedly at 7.5 mM. Deferoxamine (an Al3+ chelator) almost completely prevented these NaF-induced responses, which may suggest a role for G protein activation. The apoptotic effect was partially reduced by the PKA inhibitor H89. NaF induced a weak but sustained increase in PKC activity, whereas the PKC activator TPA induced a transient effect. TPA, which enhanced the NaF-induced PKC activity, was not apoptotic when added alone, but facilitated the NaF-induced apoptosis and the increase in PI-positive cells. PKC downregulation induced by TPA pretreatment almost completely prevented the NaF-induced apoptosis and the increase in PI-positive cells. Pretreatment with the PKC inhibitor GF109203X, which abolished the PKC activity after 3 hours, enhanced the NaF-induced apoptosis. KN93 (a CaM kinase II inhibitor) and W7 (a calmodulin inhibitor) seem to reduce the apoptotic effect of NaF, whereas BAPTA-AM (a Ca2+ chelator) was without effect. The tyrosine kinase inhibitor genistein also markedly reduced the NaF-induced apoptosis, whereas the PI-3 kinase inhibitor wortmannin augmented the response. In conclusion, the present results suggest that NaF induces an apoptotic effect and an increase in PI-positive A549 cells via similar mechanisms, involving PKC, PKA, tyrosine kinase and Ca2+-linked enzymes, whereas PI-3 kinase seems to exert a counteracting effect.

Specific T-cell immunity against Ki-ras peptides in patients with pancreatic and colorectal cancers

Mutations of codon 12 in the Ki-ras gene are frequently found in pancreatic and colorectal cancers. It has been demonstrated that human T-cells have the potential to recognise tumours expressing mutated ras-derived peptides. However, it remains unclear whether T-cells from a given individual can recognise the mutant peptides, which are expressed in that individual's tumour tissues. Mutations of the Ki-ras oncogene were analysed by the mutant-allele-specific amplification (MASA) method in pancreatic and colorectal tumour tissues, and T-cell responses against mutated Ki-ras-derived peptides were measured by [(3)H]thymidine incorporation and IFN-gamma production assays. Specific T-cell responses against Ki-ras-products were found in cancer patients, whereas no immune response was observed in normal individuals (P<0.01). Six of the eight pancreatic cancer patients (75%) and nine of 26 colorectal cancer patients (35%) had T-cell responses to mutated Ki-ras-derived-peptides. T-cell response in a given individual cannot recognise the same mutated ras peptide, which is expressed in that individual's tumour tissues. However, pancreatic and colorectal cancer patients have T-cell immunity against Ki-ras-peptides, and this provides potential target for cancer immunotherapy.

K-RAS mutation in transitional cell carcinoma of urinary bladder

In the present study it was aimed to investigate the frequency of K-RAS mutation in the human bladder transitional cell carcinoma. For this purpose, tissue specimens obtained from the patients with bladder tumors. Genomic DNAs were isolated and then PCR-SSCP analysis of K-RAS gene were performed. A heterozygous deleted mutation was detected in K-RAS oncogene (exon 2) in agarose gel electrophoresis in one patient and point or substitution mutations are detected using single strand conformational polymorphism (SSCP) in other different patients with bladder cancer (4/14). In conclusion, the frequency of K-RAS mutation is not rare and the role of this mutation in oncogenesis and in infiltration of the urinary bladder wall needs to be confirmed in a larger study.

K-RAS mutation in transitional cell carcinoma of urinary bladder

In the present study it was aimed to investigate the frequency of K-RAS mutation in the human bladder transitional cell carcinoma. For this purpose, tissue specimens obtained from the patients with bladder tumors. Genomic DNAs were isolated and then PCR-SSCP analysis of K-RAS gene were performed. A heterozygous deleted mutation was detected in K-RAS oncogene (exon 2) in agarose gel electrophoresis in one patient and point or substitution mutations are detected using single strand conformational polymorphism (SSCP) in other different patients with bladder cancer (4/14). In conclusion, the frequency of K-RAS mutation is not rare and the role of this mutation in oncogenesis and in infiltration of the urinary bladder wall needs to be confirmed in a larger study.

Glucocorticoids inhibit lung cancer cell growth through both the extracellular signal-related kinase pathway and cell cycle regulators

Glucocorticoids inhibit the proliferation of various cell types, but the mechanism of this inhibition remains unclear. We investigated the effect of dexamethasone on non-small cell lung cancer cell growth and cell cycle progression. We showed that dexamethasone suppresses the proliferation of A549 and Calu-1 cells, with accumulation of cells in G1/G0 stage of the cell cycle, as determined by fluorescence-activated cell sorter analysis. Western blot analysis confirmed that this is associated with hypophosphorylation of retinoblastoma protein. Using Western blot analysis and in vitro kinase assays, we found that dexamethasone results in decreased activity of CDK2 and 4, decreased levels of cyclin D, E2F, and Myc, and increased levels of the CDK inhibitor p21(Cip1). In addition, we found that dexamethasone decreases activity of extracellular signal-related kinase (ERK)/mitogen-activated protein kinase (MAPK). The kinetics of all these changes indicate that inhibition of the ERK/MAPK pathway precedes the cell cycle effects, suggesting that regulation of this MAPK-signaling pathway may be an alternative mechanism for glucocorticoid-induced cell cycle arrest and growth inhibition.

The farnesyl transferase inhibitor RPR-130401 does not alter radiation susceptibility in human tumor cells with a K-Ras mutation in spite of large changes in ploidy and lamin B distribution

BACKGROUND

Growth inhibition by RPR-130401, a non-peptidomimetic farnesyltransferase inhibitor, was investigated without or with combined exposure to ionizing radiation in three human tumor cell lines (HCT-116, MiAPaCa-2 and A-549) bearing a point mutation in the K-Ras gene.

RESULTS

RPR-130401 inhibited cell growth with an IC50 of 50 nM (HCT-116), 120 nM (MiAPaCa-2) and 710 nM (A-549), with a poor incidence of apoptosis. The drug brought about G1 and S phase depletion together with arrest of cells in G2 phase and induced a significant accumulation of hyperploid cells showing active S phase DNA synthesis, with HCT-116 and A-549 cells being the most and least responsive, respectively. The drug also produced dramatic changes of the nuclear lamin B pattern, without lamin B cleavage and perturbation of the actin cytoskeleton. On the other hand, RPR-130401 elicited strictly additive interaction in combined treatment with ionizing radiation with regard to cell kill, altered cell cycle progression and induced hyperploidy.

CONCLUSIONS

The data suggest that disruption of orderly progression through mitosis and cytokinesis, is a major outcome of drug action and that this effect proceeds from inhibition of lamin B farnesylation. It is anticipated from the strict additivity of RPR-130401 and radiation that neither induced radiation resistance nor acute or late complications of radiotherapy, should occur in combined treatment with RPR-130401.

Establishment of cell lines with high and low metastatic potential from A549 human lung adenocarcinoma

This article reports the establishment of variant cell lines with high and low metastatic potential by the dilution plating technique. Two clones with high metastatic potential, 2S Lu-4 and 11S Lu-1 and two clones with low metastatic potential, 8S and 16S were established from A549 human lung adenocarcinoma. The high-metastatic cell lines produced enhanced lung metastases, but the low-metastatic cell lines did not produce lung metastasis after injection into the tail vein of 5-week-old BALB / c nude mice. The primary tumors produced by the two high-metastatic cells grew fast and showed enhanced angiogenesis. The high-metastatic cells were small and flat-shaped, while the low-metastatic cells were large and flat-shaped. When the four variant cell lines and original A549 cells were embedded in collagen gels, the colonies of 2S Lu-4, 11S Lu-1 and A549 grew actively, whereas almost of all the colonies of 8S and 16S did not survive after 35 days in culture. These four cloned cell lines originated from heterogeneous populations of the parental A549 cells should be an excellent tool for studying the process of metastasis of lung cancer.

Methylation of O(6)-methylguanine-DNA methyltransferase gene is associated significantly with K-ras mutation, lymph node invasion, tumor staging, and disease free survival in patients with gastric carcinoma

BACKGROUND

O(6)-methylguanine-DNA methyltransferase (MGMT) can remove O(6)alkylG DNA adducts. If they are not removed, then the adducts mispair with T during DNA replication, resulting in G-to-A mutation. Interrelations between MGMT gene inactivation by promoter methylation, K-ras mutation, and clinicopathologic features in patients with gastric carcinoma were studied.

METHODS

Surgically removed tumor tissues from 79 patients were analyzed with MGMT methylation by genomic DNA modification and methylation specific polymerase chain reaction analysis, K-ras mutation by mutant allele specific amplification, TNM classification according to the International Union Against Cancer system, and MGMT protein expression by immunohistochemistry.

RESULTS

MGMT-promoter methylation was found in 18 of 79 tumors. Among those 18 tumors, K-ras mutations were found in 33% and 11% of tumors at codons 12 and 13, respectively, corresponding to 20 times and 7 times greater rates of mutation compared with unmethylated tumors. MGMT methylation was associated significantly with lymph node invasion (P < 0.01), tumor stage (P < 0.03) and 5-year disease free survival (P < 0.02). MGMT protein expression was detected in intestinal metaplasia and adenocarcinoma samples, whereas no expression was detected in normal foveolar cells.

CONCLUSIONS

MGMT-promoter methylation in patients with gastric carcinoma was associated significantly with point mutations of K-ras at codons 12 and 13, lymph node invasion, tumor stage, and disease free survival. These associations indicate a significant role of MGMT methylation during gastric carcinogenesis.

Mutation of cell cycle regulators and their impact on superficial bladder cancer

Early cytogenetic studies in bladder cancer identify regions of chromosomal gain or loss that can be candidate loci for oncogenes and tumor suppressor genes. Oncogenes with potential prognostic significance identified in bladder cancer the RAS family, epidermal growth factor receptor, ERBB-2, MDM2, and cyclin D1. The TP53 gene has been the most thoroughly characterized tumor suppressor gene in bladder cancer, with correlation of TP53 alterations with type of carcinogenic exposure, tumor stage and grade, as well as prognosis. Studies evaluating alterations of the retinoblastoma pathway have identified the retinoblastoma gene, RB, p161NK4A/CDKN2, and E2F-1 as tumor suppressor genes with potential prognostic significance in patients with bladder cancer. Better understanding of the genetic mechanisms underlying bladder tumor development and progression will allow better prevention, diagnosis, and treatment strategies.

Non-radioactive detection of K-ras mutations by nested allele specific PCR and oligonucleotide hybridization

The development of methods to detect point mutations has been rapid over the recent years. In human colon tumours, a significant percentage of mutations are found in the K-ras gene. Faster and more sensitive methods for detection of these mutations are important for patient management and treatment. The author has extended the specificity of allele amplification of point mutations by using mismatch oligonucleotide primers in a polymerase chain reaction (PCR). It is shown that in colon tumours, the sensitivity of detecting a mutation is significantly higher when K-ras exon 1 is amplified prior to PCR with allele specific primers (mismatch PCR). It is shown that allele specific oligonucleotide probes which are non-radioactively labelled could be used to detect these point mutations. By utilizing this two-step PCR, K-ras codon 12 mutations were studied in 10 colon carcinoma cell lines and 25 colon tumours. By combining the two-step PCR together with non-radioactively labelled oligonucleotide probes, the detection of point mutations is both accurate and rapid.

Validation of the Point-EXACCT method in non-small cell lung carcinomas

K-ras point mutations are often detected in part of the lung carcinomas. For the validation of a highly sensitive and rapid assay for known point mutations, Point-EXACCT (Biochim Biophys Acta 1998; 1379:42–52), we analyzed 89 non-small cell lung carcinomas and compared the results with two sequencing methods. No point mutations were found with double-stranded sequencing. Single-stranded sequencing detected six patients positive for K-ras codon 12. When Point-EXACCT was used, K-ras codon 12 mutations were detected in 8 of 52 patients with squamous cell carcinomas, 10 of 29 patients with adenocarcinomas, and 3 of 8 patients with large cell carcinomas. The finding of K-ras mutations in squamous cell carcinomas is explained by the high sensitivity of the method. Therefore, Point-EXACCT may be applicable to detection of those alterations occurring at a low frequency among an excess of cells with wild-type DNA.

Accumulation of genetic alterations and their significance in each primary human cancer and cell line

Analyses of multiple genetic alterations accumulated in each cancer cell is expected to provide useful information to elucidate the molecular mechanisms involved in tumorigenesis. Here, we summarized the results of studies on aberrations of oncogenes and tumor suppressor genes by ourselves and other groups. DNAs analyzed were from particular sets of surgical specimens from human tumors and cancer cell lines derived from non-small cell lung cancers, pancreatic cancers, hepatocellular carcinomas and gliomas. Tumors could be grouped into two types based on the genetic alterations detected. Tumors in group 1 had mutations in genes encoding proteins involved in a limited number of signal transduction cascades such as p16-cyclin D1/CDK4-RB or MDM2-p53-p21, where the aberration of one component seems to be sufficient to cause dysfunction of the cascade. Group 2 contained a subset of tumors in which no alteration was detected in the genes analyzed, even in the advanced stage or established cancer cells, indicating the involvement of completely different oncogenic pathways.

Antitumor activity of a phosphorothioate antisense oligodeoxynucleotide targeted against C-raf kinase

Substantial evidence exists supporting a direct role for raf kinases in the development and maintenance of certain human malignancies. Here we test the potential of phosphorothioate antisense oligodeoxynucleotides targeted against human C-raf-1 kinase to specifically inhibit C-raf-1 kinase gene expression and tumor progression in cell culture and in vivo, using human tumor xenograft mouse models. Treatment of human tumor cells with appropriate phosphorothioate antisense oligodeoxynucleotides led to specific inhibition of C-raf kinase gene expression in cell culture and in vivo at well-tolerated doses. Moreover, oligodeoxynucleotide treatment resulted in potent antiproliferative effects in cell culture and potent antitumor effects in vivo against a variety of tumor types that were highly consistent with an antisense mechanism of action for these compounds. These studies strongly suggest that antisense inhibitors targeted against C-raf-1 kinase may be of considerable value as antineoplastic agents that display activity against a wide spectrum of tumor types at well-tolerated doses.

Point mutations in the Ki-ras2 gene of codon 12 in the Dunning R-3327 Prostatic Adenocarcinoma system

Detection of point mutations in the Dunning System with the Ki-ras2 gene in the first and second positions of codon 12 exon I, has been performed using allele-specific oligonucleotide (ASO) primers. PCR generated 94bp templates and genomic DNA extracted from the Dunning cell lines AT-1, AT-3, Mat-Lu, and Mat-Lylu were tested. Our investigation revealed that the first and second positions of codon 12 have undergone either transitions or transversions from the wild type sequence (GG). Dorsal prostate (DP) solid tissues used as controls revealed the wild type configuration as well as transversions at both positions, in addition to a transition in the first position for Mat-Lu. The most aberrant of the Dunning lines (AT-3 and Mat-LyLu) collectively displayed sequence changes (transitions and transversions) with no evidence of the wild type configuration. These findings are supportive of biometric studies (area, shape factor, and motility) along with adhesion and invasion assays done in our laboratory in correlating genotypic and phenotypic properties to metastatic potential.

K-ras codon 12 mutations in biliary tract tumors detected by polymerase chain reaction denaturing gradient gel electrophoresis

BACKGROUND

Although the prevalence of K-ras codon 12 mutations in biliary tract (BT) tumors has been addressed in previous studies, the results have shown large discrepancies in mutation frequency.

METHODS

K-ras codon 12 mutations were investigated by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE), a sensitive method for detecting DNA base changes, in a large series of BT tumors.

RESULTS

In A-549 cells, which are known to contain a G to A change at the first base of K-ras codon 12, the mutation could be detected by DGGE even after 1:16 dilution with normal DNA. Tumor samples were microdissected from paraffin embedded tissue sections to ensure the presence of the tumor cells. K-ras mutations were detected in 13 of 23 bile duct tumors (56.5%) and in 9 of 23 gallbladder tumors (39.1%) by DGGE. However, no mutations were detected in normal, hyperplastic, and dysplastic BT epithelium or in tumorlike lesions, such as adenomyomatous hyperplasia, cholesterol polyps, and cystitis glandularis proliferans. The samples exhibiting abnormalities on DGGE showed a base change at K-ras codon 12 when examined by oligonucleotide hybridization.

CONCLUSIONS

K-ras codon 12 mutations are seen often in BT tumors, and a combination of microdissection and PCR-DGGE is an effective approach for their detection.

Lower incidence of K-ras codon 12 mutation in flat colorectal adenomas than in polypoid adenomas

In order to clarify genetic changes in flat adenomas, K-ras codon 12 point mutations were examined in 56 flat adenomas, 81 polypoid adenomas and 42 cancers of colon and rectum. The mutation frequency in flat adenomas was 23% (13/56), significantly lower than that in polypoid adenomas (67%: 54/81) and cancers (76%: 32/42). Even mildly dysplastic adenomas or small (less than 5 mm) adenomas showed higher mutation incidence in polypoid type (62%, 57%) than in flat type (23%, 19%). Among flat adenomas, flat elevated lesions exhibited relatively higher mutation frequency than completely flat or depressed ones. As for cancers, 14 tumors (33%) contained mutations only in a minor tumor cell population, indicating that these mutations occur at a late stage of tumorigenesis. These results suggest that the adenoma-carcinoma sequence through flat adenomas may be different from that through polypoid adenomas, and genetic changes may be heterogeneous in colorectal carcinogenesis.

Nonrandom chromosomal rearrangements in pancreatic carcinomas

Short-term cultures were initiated from 20 carcinomas of the pancreas, 17 of which could be successfully cytogenetically analyzed. In eight carcinomas, only normal karyotypes were detected, probably representing dividing stromal cells. Three cases had -Y as the sole anomaly, which also may have occurred in cells that do not belong to the tumor parenchyma. Massively rearranged karyotypes with modal chromosome numbers in the triploid (five cases) and diploid-triploid (one case) ranges were found in the remaining six carcinomas. Structural rearrangements, including deletions and unbalanced translocations, of the long arm of chromosome 6, involving bands q13 and q15 twice and q11 and q16 once, occurred in four tumors. All of these aberrations led to loss of chromosome material from 6q, always involving 6q15. Deletions and unbalanced translocations of the short arm of chromosome 1 also were found in four cases, affecting band p32 in three of them. In all four cases, the abnormalities resulted in loss of genetic material distal to 1p32. Chromosome 17 was involved in structural aberrations in three cases, twice as unbalanced translocations leading to loss of 17p material. Deletions of the short arms of chromosomes 3 and 8 were detected in two carcinomas. The most consistent numerical abnormalities were +2, +10, +11, +14, and tetrasomy 20, which were seen in all six cases. The findings suggest that structural rearrangements, or loss, of genes located on 1p, 3p, 6q, 8p, and 17p are of pathogenetic importance in pancreatic carcinogenesis.