Abstract 5027: SU11274 induced apoptosis through accumulated p53-mediated pathway in NSCLC cells and xenograft model

Recent advances in molecular understanding of pathogenesis of non-small cell lung cancer (NSCLC) at molecular level improved treatment outcome. However, the overall 5 year survival rate of individuals with lung cancer remains at < 15%. Therefore, novel therapeutic strategies are still needed to improve the survival rate of lung cancer patients. MET, the tyrosine kinase receptor for hepatocyte growth factor (HGF), is involved in mediating tumorigenesis, cell motility, invasion and metastasis and is frequently deregulated in various human cancers including NSCLC. The MET receptor is an attractive potential target for novel therapeutic inhibition in human cancer. Recently, the MET tyrosine kinase inhibitors (TKIs), such as PHA-665752 and SU11274, have been most extensively evaluated in preclinical model, and have been known to be effective in growth inhibition of various malignancies. However, the mechanisms of MET TKIs on the growth-inhibitory effect on cancers are not clear. There have been a few reports that MET-induced oncogensis was accelerated by the loss of wild-type p53. In this study, we investigated the role of p53 in growth-inhibitory effects of MET TKI (SU11274) in the NSCLC cells. We used A549 cells (p53 wild-type) and Calu-1 cells (p53 null-type) and these cells were known to have wild-type MET. SU11274 showed more profound growth inhibition and apoptosis in A549 cells than in Calu-1 cells. The expression of p53 protein by modulation of p53 transitional level was observed by SU11274 treatment in A549 cells. Accumulated p53 protein after SU11274 treatment induced up-regulation of Bax, PUMA proteins and down-regulation of Bcl-2 protein and subsequently the activation of caspase 3 in p53 wild type A549 cells only. Inhibition of p53 expression using siRNA technology in A549 cells caused significant decrease of apoptosis by SU11274 and inactivation of p53-mediated apoptosis. The introduction of p53 into Calu-1 effectively leaded to SU11274-induced apoptosis through p53-mediated pathway. As same as in A549 cells to confirm the anti-tumor effect of SU11274 in vivo, A549 xenograft model was used and SU11274 effectively shrunk the tumor volume and also induced apoptosis via the increases of p53 protein. Taken together, SU11274 significantly induced apoptosis in wild-type p53 NSCLC cells through the increased expression p53-mediated apoptotic pathway but not in the p53-null NSCLC cells. These results suggest that p53 play an important role in SU11274-induced apoptosis and p53 status might be related with the sensitivity of SU11274 in NSCLC.

* This study was supported by a grant of the Korea Health 21 R&D project, the Ministry of Health & Welfare, Republic of Korea. (A010250)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5027.

Synergistic tumoricidal effect of combined hMUC1 vaccination and hNIS radioiodine gene therapy

We examined the merits of combinatorial hMUC1 vaccination and hNIS radioiodine gene therapy and evaluated its tumoricidal effects in an animal tumor model. CMNF (CT26 expressing hMUC1, hNIS, and firefly luciferase) cells were transplanted into 28 mice, and 4 and 11 days after tumor challenge, tumor-bearing mice were immunized i.m. with pcDNA3.1 or pcDNA-hMUC1 vaccine and subsequently administered PBS or (131)I i.p. [four groups (7 mice per group): pcDNA3.1 + PBS, phMUC1 + PBS, pcDNA3.1 + (131)I, and phMUC1 + (131)I groups]. Thirty-two days after tumor challenge, we rechallenged mice in the pcDNA3.1 + (131)I and phMUC1 + (131)I groups with CMNF cells. Tumor progression and tumor-free mice (%) were monitored by bioluminescence. We investigated hMUC1-associated immune response generated by combination therapy. Marked tumor growth inhibition was observed in the phMUC1 + (131)I group by bioluminescence at 32 days after tumor challenge. Mice in phMUC1 + (131)I group showed complete hMUC1-expressing tumor suppression after tumor rechallenge, whereas mice in the pcDNA3.1 + (131)I group did not. The tumor-free mice (%) were much higher in the phMUC1 + (131)I group than in the other three groups. Levels of hMUC1-associated CD8(+)IFN-gamma(+) T cells were higher in the phMUC1 + (131)I group than in the other three groups. hMUC1-loaded CD11(+) cells in the phMUC1 + (131)I group were found to be most effective at generating hMUC1-associated CD8(+)IFN-gamma(+) T cells. The activities of hMUC1-associated cytotoxic T cells in the phMUC1 + (131)I group were higher than in the other three groups. Our data suggest that phMUC1 + (131)I combination therapy synergistically generates marked tumoricidal effects against established hMUC1-expressing cancers.

Abnormal fragile histidine triad (Fhit) expression in invasive cervical adenocarcinoma: association with tumor aggressiveness

The fragile histidine triad (FHIT) gene is a candidate tumor suppressor gene. Aberrant expression of the encoded protein and inactivation of FHIT correlate with several clinicopathological parameters in various tumor types, including cervical cancer, but Fhit expression has rarely been studied in cervical adenocarcinoma. We assessed Fhit protein expression in 35 surgical specimens of invasive adenocarcinomas of the uterine cervix and investigated whether expression alteration on immunohistochemistry staining is associated with important clinicopathological features. Considerably reduced or absent Fhit staining was observed in 11 cancers (31.4%). By univariate analysis, Fhit protein expression was significantly associated with nodal status (P = .002), histologic grade (P = .000), and International Federation of Gynecology and Obstetrics stage (P = .032). Depth of invasion, tumor size, or parametrial invasion did not show important association with Fhit. Lymph node status, International Federation of Gynecology and Obstetrics stage, and histologic grade are known prognostic factors of cervical adenocarcinoma, and Fhit status on immunohistochemistry staining demonstrated significant association with tumor aggressiveness. Staining of biopsy specimens for Fhit is worthy of study as a prognostic tool.

ZBP-89-induced apoptosis is p53-independent and requires JNK

ZBP-89 induces apoptosis in human gastrointestinal cancer cells through a p53-independent mechanism. To understand the apoptotic pathway regulated by ZBP-89, we identified downstream signal transduction targets. Ectopic expression of ZBP-89 induced apoptosis through the mitochondrial pathway and was accompanied by activation of all three MAP kinase subfamilies: JNK1/2, ERK1/2 and p38 MAP kinase. ZBP-89-induced apoptosis was markedly enhanced by ERK inhibition with U0126. In contrast, inhibiting JNK with a JNK1-specific peptide inhibitor or dominant-negative JNK2 expression abrogated ZBP-89-mediated apoptosis. The p38 inhibitor SB202190 had no effect on ZBP-89-induced cell death. Protein dephosphorylation assays revealed that ZBP-89 activates JNK via repression of JNK dephosphorylation. Oligonucleotide microarray analyses revealed that ectopic expression of ZBP-89 downregulated expression of the dual-specificity phosphatase MKP6. Overexpression of MKP6 blocked ZBP-89-induced JNK phosphorylation and PARP cleavage. In addition, ectopic expression of ZBP-89 repressed Bcl-xL and Mcl-1 expression, but had no effect on Bcl-2. Silencing ZBP-89 with small interfering RNA enhanced both Bcl-xL and Mcl-1 expression. Taken together, ZBP-89-mediated apoptosis occurs via a p53-independent mechanism that requires JNK activation.

Secreted proNGF is a pathophysiological death-inducing ligand after adult CNS injury

The unprocessed precursor of the neurotrophin nerve growth factor (NGF), proNGF, has been suggested to be a death-inducing ligand for the neurotrophin receptor p75. Whether proNGF is a true pathophysiological ligand that is secreted, binds p75, and activates cell death in vivo, however, has remained unknown. Here, we report that after brain injury, proNGF was induced and secreted in an active form capable of triggering apoptosis in culture. We further demonstrate that proNGF binds p75 in vivo and that disruption of this binding results in complete rescue of injured adult corticospinal neurons. These data together suggest that proNGF binding to p75 is responsible for the death of adult corticospinal neurons after lesion, and they help to establish proNGF as the pathophysiological ligand that activates the cell-death program by means of p75 after brain injury. Interference in the binding of proNGF to p75 may provide a therapeutic approach for the treatment of disorders involving neuronal loss.

Akt/PKB promotes cancer cell invasion via increased motility and metalloproteinase production

The Akt/protein kinase B (PKB) serine/threonine kinase is well known as an important mediator of many cell survival signaling pathways. Here, we demonstrate for the first time a major role of Akt/PKB in the cell invasion properties of the highly metastatic cell line HT1080. Using confocal microscopic analyses of live samples, we found Akt/PKB to be localized in the leading edge membrane area of migrating HT1080 cells. This localization was dependent on phosphoinositide 3-kinase and required the lipid binding ability of the phosphoinositide binding pleckstrin homology domain of Akt/PKB. We examined the possible function of Akt/PKB in HT1080 invasion. Surprisingly, Akt/PKB potently promoted HT1080 invasion, by increasing cell motility and matrix metalloproteinase-9 (MMP-9) production, in a manner highly dependent on its kinase activity and membrane-translocating ability. The increase in MMP-9 production was mediated by activation of nuclear factor-kappaB transcriptional activity by Akt/PKB. However, Akt/PKB did not affect the cell-cell or cell-matrix adhesion properties of HT1080. Our findings thus establish Akt/PKB as a major factor in the invasive abilities of cancer cells.

Effects of priming a bipolar attribute concept on dimension versus concept-specific accessibility of semantic memory

In Experiment 1, participants received behavioral information about a person that could be interpreted as either honest or unkind. Priming a concept along 1 dimension (e.g., honesty) increased the likelihood of spontaneously describing the target along this dimension (i.e., as honest), regardless of whether the primed concept was directly applicable for interpreting the target's behavior ("honest") or was its bipolar opposite ("dishonest"). Experiment 2 replicated this finding in a different, product domain. It further demonstrated that when information is ambiguous, primed concepts can influence not only the dimension along which the target is described but also the value it is assigned along this dimension. The effect of priming in both experiments was reflected in participants' overall evaluations of the targets as well as in their spontaneous descriptions of it. Results were consistent with the assumption that bipolar attributes are associatively linked in memory but are stored as separate concepts rather than as values along a bipolar continuum.

Se-methylselenocysteine induces apoptosis mediated by reactive oxygen species in HL-60 cells

Recent studies have implicated apoptosis as one of the most plausible mechanisms of the chemopreventive effects of selenium compounds, and reactive oxygen species (ROS) as important mediators in apoptosis induced by various stimuli. In the present study, we demonstrate that Se-methylselenocysteine (MSC), one of the most effective selenium compounds at chemoprevention, induced apoptosis in HL-60 cells and that ROS plays a crucial role in MSC-induced apoptosis. The uptake of MSC by HL-60 cells occurred quite early, reaching the maximum within 1 h. The dose-dependent decrease in cell viability was observed by MSC treatment and was coincident with increased DNA fragmentation and sub-G(1) population. 50 microM of MSC was able to induce apoptosis in 48% of cell population at a 24 h time point. Moreover, the release of cytochrome c from mitochondria and the activation of caspase-3 and caspase-9 were also observed. The measurement of ROS by dichlorofluorescein fluorescence revealed that dose- and time-dependent increase in ROS was induced by MSC. N-acetylcysteine, glutathione, and deferoxamine blocked cell death, DNA fragmentation, and ROS generation induced by MSC. Moreover, N-acetylcysteine effectively blocked caspase-3 activation and the increase of the sub-G(1) population induced by MSC. These results imply that ROS is a critical mediator of the MSC-induced apoptosis in HL-60 cells.

Inhibitory effect of selenite on invasion of HT1080 tumor cells

Selenium, an essential biological trace element, has been shown to reduce and prevent the incidence of cancer. Our previous studies have shown that selenite is involved in the chemoprevention of cancer and induction of apoptosis of cancer cells. In this study, we demonstrate that selenite also inhibits the invasion of tumor cells. Cancer cell invasion requires coordinated processes, such as changes in cell-cell and cell-matrix adhesion, degradation of the extracellular matrix, and cell migration. We found that selenite inhibited invasion of HT1080 human fibrosarcoma cells. Adhesion of HT1080 cells to the collagen matrix was also inhibited by treatment with selenite, but cell-cell interaction and cell motility were not affected by selenite. Moreover, selenite reduced expression of matrix metalloproteinase-2 and -9 and urokinase-type plasminogen activator, which are involved in matrix degradation, but increased a tissue inhibitor of metalloproteinase-1. This inhibitory effect of selenite on the protease expressions was mediated by the suppression of transcription factors, NF-kappaB and AP-1. However, selenate showed no remarkable effect on all the steps of cancer cell invasion.

Polyamine synthesis in plants: isolation and characterization of spermidine synthase from soybean (Glycine max) axes

Spermidine synthase (EC 2.5.1.16) was purified to homogeneity for the cytosol of soybean (Glycine max) axes using ammonium sulfate fractionation and chromatography on DEAE-Sephacel, Sephacryl S-300, omega-aminooctyl-Sepharose and ATPA-Sepharose. The molecular mass of the enzyme estimated by gel filtration and SDS-PAGE is 74 kDa. Cadaverin and 1,6-diaminohexane could not replace putrescine as the aminopropyl acceptor. Kinetic behaviors of the substrate are consistent with a ping pong mechanism. The kinetic mechanism is further supported by direct evidence confirming the presence of an aminopropylated enzyme and identification of product, 5'-deoxy-5'-methylthioadenosine, prior to adding putrescine. The Km values for decarboxylated S-adenosylmethionine and putrescine are 0.43 microM and 32.45 microM, respectively. Optimum pH and temperature for the enzyme reaction are 8.5 and 37 degrees C, respectively. The enzyme activity is inhibited by N-ethylmaleimide and DTNB, but stimulated by Co2+, Cu2+ and Ca2+ significantly, suggesting that these metal ions could be the cellular regulators in polyamine biosynthesis.

Neurotrophin receptors: mediators of life and death

The mechanism of action of NGF has continued to provide a challenging and formidable problem in signal transduction. NGF can bind independently to two different receptors, the trkA tyrosine kinase receptor and the p75 neurotrophin receptor, which are involved in many different signaling events. In addition to promoting cell differentiation survival, NGF can paradoxically be an inducer of cell death. Several receptor mediated mechanisms are proposed to explain how NGF might act as a trophic factor and as a cell killer. The survival and cell death properties of the receptors are dependent upon the relative ratio of receptors and the persistent nature of the signaling events.

Competitive signaling between TrkA and p75 nerve growth factor receptors determines cell survival

In addition to its role as a survival factor, nerve growth factor (NGF) has been implicated in initiating apoptosis in restricted cell types both during development and after terminal cell differentiation. NGF binds to the TrkA tyrosine kinase and the p75 neurotrophin receptor, a member of the tumor necrosis factor cytokine family. To understand the mechanisms underlying survival versus death decisions, the TrkA receptor was introduced into oligodendrocyte cell cultures that undergo apoptosis in a p75-dependent manner. Here we report that activation of the TrkA NGF receptor in oligodendrocytes negates cell death by the p75 receptor. TrkA-mediated rescue from apoptosis correlated with mitogen-activated protein kinase activation. Concurrently, activation of TrkA in oligodendrocytes resulted in suppression of c-jun kinase activity initiated by p75, whereas induction of NFkappaB activity by p75 was unaffected. These results indicate that TrkA-mediated rescue involves not only activation of survival signals but also simultaneous suppression of a death signal by p75. The selective interplay between tyrosine kinase and cytokine receptors provides a novel mechanism that achieves alternative cellular responses by merging signals from different ligand-receptor systems.

A dominant role of the juxtamembrane region of the TrkA nerve growth factor receptor during neuronal cell differentiation

All receptor tyrosine kinases share a common intracellular signaling machinery, including ras activation, whereas cellular responses vary from mitogenesis to cell differentiation. To investigate the structural basis for receptor tyrosine kinase action for nerve growth factor, the juxtamembrane region of TrkA was transferred to a corresponding region of the epidermal growth factor (EGF) receptor. The resulting chimeric receptor contains an additional Shc site, Tyr490, in the juxtamembrane region. In transfected PC12 cell lines, neuronal differentiation was observed with EGF treatment, as evidenced by increased neurite extension. The action of the chimeric receptor was correlated with prolonged activation of MAP kinases and a 3-4-fold increase in phosphatidylinositol 3-kinase activity. The effect of the juxtamembrane chimera was dependent upon the Shc site at Tyr490, because expression of a chimeric receptor containing a Y490F mutation resulted in a complete loss of neuritogenesis by EGF treatment. These findings indicate that the juxtamembrane region of the TrkA receptor serves as a key functional domain that can confer a dominant effect upon neuronal differentiation.

A novel basal promoter element is required for expression of the rat tyrosine hydroxylase gene

Transcription of the rat tyrosine hydroxylase (TH) gene is controlled by enhancer sequences in its 5' flanking region; these enhancers include the AP1, dyad, and cAMP response element (CRE) motifs. We show that a novel basal promoter element (-17 GCCTGCCTGGCGA -5) positioned between the TATA box and +1 works in conjunction with the upstream AP1-dyad and CRE enhancers but cannot support transcription by itself. A mutation of this element, termed partial dyad, reduces basal expression of a reporter gene in TH-positive cell lines and TH-negative lines but has no effect on cAMP- or KCl-induced expression. A double mutant at positions -17 and -11 of the partial dyad reduces transcriptional activation by 80%. Conversely, insertion of this element into a heterologous promoter restores basal expression to levels mediated by the native TH promoter. The partial dyad is a novel activational element that is required for full expression of the TH gene and may assist in the function of the AP1, dyad, and CRE motifs and also other enhancers further upstream. Hence, the rat TH gene is unusual in that its enhancers will not function with a heterologous promoter but require a specific TH promoter sequence for full activation.

Adenovirus-mediated gene delivery into neuronal precursors of the adult mouse brain

Precursor cells found in the subventricular zone (SVZ) of the adult brain can undergo cell division and migrate long distances before differentiating into mature neurons. We have investigated the possibility of introducing genes stably into this population of cells. Replication-defective adenoviruses were injected into the SVZ of the lateral ventricle of adult mice. The adenoviruses carried a cDNA for the LacZ reporter or the human p75 neurotrophin receptor, for which species-specific antibodies are available. Injection of the viruses into the SVZ led to efficient labeling of neuronal precursors. Two months after viral injection, infected cells were detected in the olfactory bulb, a significant distance from the site of injection. Labeled periglomerular and granular neurons with extensive dendritic arborization were found in the olfactory bulb. These results demonstrate that foreign genes can be efficiently introduced into neuronal precursor cells. Furthermore, adenovirus-directed infection can lead to long-term stable gene expression in progenitor cells found in the adult central nervous system.

The cyclic AMP response element directs tyrosine hydroxylase expression in catecholaminergic central and peripheral nervous system cell lines from transgenic mice

Enhancer elements regulating the neuronal gene, tyrosine hydroxylase (TH), were identified in TH-expressing peripheral nervous system PATH and central nervous system CATH cell lines. Mutational analysis in which rat TH 5'-flanking sequences directed chloramphenicol acetyltransferase (CAT) reporter gene expression demonstrated that mutating the cyclic AMP response element (CRE) at -45 base pair reduced expression by 80-90%. A CRE linked to an enhancerless TH promoter fully supported expression. Cotransfection of a dominant-negative CREB protein reduced expression 50-60%, suggesting that the CRE is bound by CREB or a CREB dimerization partner. Although mutating the AP1/dyad (AD) element at -205 base pair only modestly reduced CAT levels, AD minimal enhancer constructs gave 45-80% of wild type expression when positioned at -91 or -95. However, in its native context at -205, the AD could not support expression. In contrast, a CRE, moved from its normal position at -45 to -206, gave full activity. These results indicate that the CRE is critical for TH transcription in central nervous system CATH and peripheral nervous system PATH cells, whereas the AD is less important and its enhancer activity is context-and/or position-dependent. These results represent the first attempts to map regulatory elements directing TH expression in central nervous system cell lines.

Isolation of two E-box binding factors that interact with the rat tyrosine hydroxylase enhancer

The enhancer of the rat tyrosine hydroxylase gene (TH) in PC8b cells is composed of the AP1 motif (TCATTCA, -205 to -199) and an overlapping 20-base pair dyad symmetry element (TCAGAGGCAGGTGCCTGTGA, -201 to -182) whose core is an E-box. We have isolated two partial cDNA clones that encode factors which bind the TH-dyad. One is rITF2 with a basic helix-loop-helix motif and the other is CDP2 with a homeodomain. rITF2 is a rat homolog of human ITF2 (or E2-2), and CDP2 is a member of a new family of homeoproteins defined by histidine as the 9th residue of the recognition helix and by unique 64 amino acid repeats related to those of the Drosophila cut gene. The binding affinity of CDP2 alone is relatively weak, but it enhances the binding of rITF2 to the TH-dyad. In transfected F9 cells, activation of a TH-driven reporter requires both rITF2 and CDP2, suggesting that the proteins may functionally interact. However, rITF2 and CDP2 are not restricted to TH-expressing tissues; hence they may not be involved in the tissue-specific expression of TH. In addition, CDP2 is phosphorylated in vitro and in vivo.

The Oct-2 transcription factor represses tyrosine hydroxylase expression via a heptamer TAATGARAT-like motif in the gene promoter

The tyrosine hydroxylase (TH) gene promoter contains adjacent octamer and heptamer motifs which act as target sites for octamer binding transcription factors. Mutation of the heptamer motif but not the octamer motif enhances TH promoter activity in neuronal cells expressing Oct-2 but not in non-expressing fibroblasts. Similarly addition of the heptamer motif to a minimal TH promoter represses gene expression in neuronal cells but not in fibroblasts. These effects can be reproduced by the artificial expression of neuronal isoforms of Oct-2 in fibroblasts which results in the repression of transfected TH promoters containing an intact heptamer motif but not those in which this motif has been mutated or deleted. The TH promoter thus represents the first example of a cellular promoter which is repressed by Oct-2. The significance of this effect is discussed in terms of the cell type specificity of the TH promoter and its induction by different physiological stimuli.

Tissue-specific transcription of the rat tyrosine hydroxylase gene requires synergy between an AP-1 motif and an overlapping E box-containing dyad

Transcription of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis, is regulated in a tissue-specific manner. We have identified sequences from -205 to -182 as the minimal enhancer for TH in pheochromocytoma cells using site-directed mutagenesis. This segment (TGATTCAGAGGCAGGTGCCTGTGA) is composed of an AP-1 motif (TGATTCA) and an overlapping 20 bp dyad whose core resembles an E box site (CANNTG). Interaction between the two elements is necessary both in vivo and in vitro: mutation of either element caused a 65%-95% reduction in transcription, and the combination of the two elements conferred cell-specific activation on a heterologous promoter; separation of the two elements by an additional helical turn not only disrupted a DNA-protein complex unique to the two elements, but also abolished expression in vivo. Therefore, we conclude that the interaction between the AP-1 and the E box dyad motifs is responsible for cell-specific TH expression.

Sequences that direct rat tyrosine hydroxylase gene expression

Investigation of neuroendocrine genes has revealed that transcription is regulated via multiple DNA binding sites, including the cyclic AMP response element (CRE). We show here that for the neuronal and chromaffin-specific gene tyrosine hydroxylase (TH), a 70-bp region (-229 to -160) lacking the CRE is sufficient, in either orientation, to confer levels of chloramphenicol acetyltransferase reporter expression equivalent to or greater than that conferred by 4.8 kb of the rat TH enhancer/promoter region. The 70-bp region contains potential binding sites for AP2, AP1, E2A/MyoD, and POU transcription factors, and functions when linked to the TH promoter, but not when joined to a heterologous RSV promoter. This demonstrates that promoter as well as enhancer elements are important for TH expression. In gel-shift assays, the 70-bp fragment forms a cell type-specific complex with nuclear extracts from TH-expressing cells. which is effectively competed by an oligonucleotide containing AP2, AP1, and E2A/MyoD (E box) sites, but not by one containing the POU site. These data suggest that the AP2, AP1, and/or E box sites may be involved in forming the cell-specific complex. Although it lacks an authentic CRE, the 70-bp region also mediated a twofold transcriptional response to forskolin, equivalent to that found with the endogenous gene. A different region (-60 to -29) bearing a consensus CRE mediated a sixfold increase in transcription in response to forskolin, but only minimally activated basal transcription from the TH promoter in the absence of forskolin.