bluuebunny/crossref_metadata_2025 huggingface dataset:
Deglycosylation of the β1-subunit of the BK channel changes its biophysical properties
Authors: Hagen Brian M. , Sanders Kenton M.
Published: June 2006

Large-conductance Ca2+-activated potassium (BK) channels are composed of pore-forming α-subunits and auxiliary β-subunits. The α-subunits are widely expressed in many cell types, whereas the β-subunits are more tissue specific and influence diverse aspects of channel function. In the current study, we identified the presence of the smooth muscle-specific β1-subunit in murine colonic tissue using Western blotting. The native β1-subunits migrated in SDS-PAGE as two molecular mass bands. Enzymatic removal of N-linked glycosylations from the β1-subunit resulted in a single band that migrated at a lower molecular mass than the native β1-subunit bands, suggesting that the native β1-subunit exists in either a core glycosylated or highly glycosylated form. We investigated the functional consequence of deglycosylating the β1-subunit during inside-out single-channel recordings. During inside-out single-channel recordings, with N-glycosidase F in the pipette solution, the open probability ( Po) and mean open time of BK channels increased in a time-dependent manner. Deglycosylation of BK channels did not affect the conductance but shifted the steady-state voltage of activation toward more positive potentials without affecting slope when Ca2+ concentration was <1 μM. Treatment of myocytes lacking the β1-subunits of the BK channel with N-glycosidase F had no effect. These data suggest that glycosylations on the β1-subunit in smooth muscle cells can modify the biophysical properties of BK channels.
“Clock-scan” protocol for image analysis
Authors: Dobretsov Maxim , Romanovsky Dmitry
Published: June 2006

Comparative analysis of extra- and intracellular distributions of protein markers in immunohistochemical and immunofluorescent studies relies on techniques of image analysis. Line or region of interest pixel intensity scans are methods routinely used. However, although having good spatial resolution, linear pixel intensity scans fail to produce integral image of the cellular distribution of the label. On the other hand, the regions of interest scans have good integrative capacity but low spatial resolution. In this work, we describe a “clock-scan” protocol that, when applied to convex objects (such as neuronal cell bodies and the majority of cells in culture), combines advantages and circumnavigates limitations of the above-mentioned techniques. The protocol 1) collects multiple radial pixel intensity profiles scanned from the cell center to the periphery, 2) scales these profiles according to the cell radius measured in the direction of the scan, and finally, 3) averages these individual profiles into one integral radial pixel intensity profile. Because of scaling, the mean pixel intensity profiles produced by the clock-scan protocol depend on neither the cell size nor, within reasonable limits, the cell shape. This allows direct comparison or, if required, averaging or subtraction of profiles of different cells. We have successfully tested the clock-scan protocol in experiments with immunostained dorsal root ganglion neurons. In addition, the protocol seems to be equally applicable for studies in a variety of other preparations.
DPP10 is an inactivation modulatory protein of Kv4.3 and Kv1.4
Authors: Li Hong-Ling , Qu Yu-Jie , Lu Yi Chun , Bondarenko Vladimir E. , Wang Shimin , Skerrett I. Martha , Morales Michael J.
Published: June 2006

Voltage-gated K+ channels exist in vivo as multiprotein complexes made up of pore-forming and ancillary subunits. To further our understanding of the role of a dipeptidyl peptidase-related ancillary subunit, DPP10, we expressed it with Kv4.3 and Kv1.4, two channels responsible for fast-inactivating K+ currents. Previously, DPP10 has been shown to effect Kv4 channels. However, Kv1.4, when expressed with DPP10, showed many of the same effects as Kv4.3, such as faster time to peak current and negative shifts in the half-inactivation potential of steady-state activation and inactivation. The exception was recovery from inactivation, which is slowed by DPP10. DPP10 expressed with Kv4.3 caused negative shifts in both steady-state activation and inactivation of Kv4.3, but no significant shifts were detected when DPP10 was expressed with Kv4.3 + KChIP2b (Kv channel interacting protein). DPP10 and KChIP2b had different effects on closed-state inactivation. At −60 mV, KChIP2b nearly abolishes closed-state inactivation in Kv4.3, whereas it developed to a much greater extent in the presence of DPP10. Finally, expression of a DPP10 mutant consisting of its transmembrane and cytoplasmic 58 amino acids resulted in effects on Kv4.3 gating that were nearly identical to those of wild-type DPP10. These data show that DPP10 and KChIP2b both modulate Kv4.3 inactivation but that their primary effects are on different inactivation states. Thus DPP10 may be a general modulator of voltage-gated K+ channel inactivation; understanding its mechanism of action may lead to deeper understanding of the inactivation of a broad range of K+ channels.
Peptides based on αV-binding domains of erythrocyte ICAM-4 inhibit sickle red cell-endothelial interactions and vaso-occlusion in the microcirculation
Authors: Kaul Dhananjay K. , Liu Xiao-du , Zhang Xiaoqin , Mankelow Tosti , Parsons Stephen , Spring Frances , An Xiuli , Mohandas Narla , Anstee David , Chasis Joel Anne
Published: June 2006

Growing evidence shows that adhesion molecules on sickle erythrocytes interact with vascular endothelium leading to vaso-occlusion. Erythrocyte intercellular adhesion molecule-4 (ICAM-4) binds αV-integrins, including αVβ3 on endothelial cells. To explore the contribution of ICAM-4 to vascular pathology of sickle cell disease, we tested the effects of synthetic peptides, V(16)PFWVRMS (FWV) and T(91)RWATSRI (ATSR), based on αV-binding domains of ICAM-4 and capable of inhibiting ICAM-4 and αV-binding in vitro. For these studies, we utilized an established ex vivo microvascular model system that enables intravital microscopy and quantitation of adhesion under shear flow. In this model, the use of platelet-activating factor, which causes endothelial oxidant generation and endothelial activation, mimicked physiological states known to occur in sickle cell disease. Infusion of sickle erythrocytes into platelet-activating factor-treated ex vivo rat mesocecum vasculature produced pronounced adhesion of erythrocytes; small-diameter venules were sites of maximal adhesion and frequent blockage. Both FWV and ATSR peptides markedly decreased adhesion, and no vessel blockage was observed with either of the peptides, resulting in improved hemodynamics. ATSR also inhibited adhesion in unactivated microvasculature. Although infused fluoresceinated ATSR colocalized with vascular endothelium, pretreatment with function-blocking antibody to αVβ3-integrin markedly inhibited this interaction. Our data strengthen the thesis that ICAM-4 on sickle erythrocytes binds endothelium via αVβ3 and that this interaction contributes to vaso-occlusion. Thus peptides or small molecule mimetics of ICAM-4 may have therapeutic potential.
Nitric Oxide Signals ThatAplysiaHave Attempted to Eat, a Necessary Component of Memory Formation After Learning That Food Is Inedible
Authors: Katzoff Ayelet , Ben-Gedalya Tziona , Hurwitz Itay , Miller Nimrod , Susswein Yehoshua Z. , Susswein Abraham J.
Published: June 2006

Inhibiting nitric oxide (NO) synthesis during learning that food is inedible in Aplysia blocks subsequent memory formation. To gain insight into the function of NO transmission during learning we tested whether blocking NO synthesis affects aspects of feeding that are expressed both in a nonlearning context and during learning. Inhibiting NO synthesis with L-NAME and blocking guanylyl cyclase with methylene blue decreased the efficacy of ad libitum feeding. D-NAME had no effect. L-NAME also decreased rejection responses frequency, but did not affect rejection amplitude. The effect of L-NAME was explained by a decreased signaling that efforts to swallow are not successful, leading to a decreased rejection rate, and a decreased ability to reposition and subsequently consume food in ad libitum feeding. Signaling that animals have made an effort to swallow is a critical component of learning that food is inedible. Stimulation of the lips with food alone did not produce memory, but stimulation combined with the NO donor SNAP did produce memory. Exogenous NO at a concentration causing memory also excited a key neuron responding to NO, the MCC. Block of the cGMP second-messenger cascade during training by methylene blue also blocked memory formation after learning. Our data indicate that memory arises from the contingency of three events during learning that food is inedible. One of the events is efforts to swallow, which are signaled by NO by cGMP.
Intracellular Calcium Is Regulated by Different Pathways in Horizontal Cells of the Mouse Retina
Authors: Schubert Timm , Weiler Reto , Feigenspan Andreas
Published: June 2006

Horizontal cells modulate the output of the photoreceptor to bipolar cell synapse, thereby providing the first level of lateral information processing in the vertebrate retina. Because horizontal cells do not generate sodium-based action potentials, calcium is likely to play an important role for graded potential changes as well as for intracellular events involved in the modulatory role of horizontal cells within the retinal network. Therefore we wanted to determine how the activation of glutamate receptors, voltage-gated calcium channels, and release of calcium from internal stores shape the calcium signal in horizontal cells. All horizontal cells responded to depolarizing voltage steps with sustained inward currents, which activated at around –20 mV, reached a peak amplitude of –79.1 pA at 5 mV, and reversed sign at around 66 mV. The current was insensitive to tetrodotoxin, and it was partially blocked by the L-type channel antagonists verapamil and nifedipine. The N-type channel blocker ω-conotoxin GVIA induced an additional reduction of current amplitudes. Calcium influx through ionotropic glutamate receptors was mediated by both AMPA and kainate but not by N-methyl-d-aspartate receptors. Two agonists at group I metabotropic glutamate receptor, trans-1-amino-1,3-cyclopentanedicarboxylic acid and quisqualate, had no effect. However, intracellular calcium was increased by caffeine, indicating release of calcium from internal stores via ryanodine receptors. These data show that intracellular calcium in horizontal cells is regulated by voltage-dependent L- and N-type calcium channels, ionotropic AMPA and kainate receptors, and release of calcium from internal stores after activation of ryanodine receptors.
Mechanism of Increased Open Probability by a Mutation of the BK Channel
Authors: Díez-Sampedro Ana , Silverman William R. , Bautista Jocelyn F. , Richerson George B.
Published: June 2006

A missense mutation (D434G) has recently been identified in the α subunit of the human large-conductance calcium-activated potassium (BK) channel. Interestingly, although the mutation causes an increase in open probability, individuals that carry the mutation have epilepsy and/or paroxysmal dyskinesia, disorders of increased brain excitability. To define the mechanisms of the mutation, we have used recordings from single channels and measurement of macroscopic conductances to examine the gating of the α subunit, modulation by the regulatory β4 subunit, and the effect of Mg2+on channel properties. Although there was relatively little difference in open dwell times for the mutant and wild-type α subunits, the mutant channel spent less time in a long-lived closed state. Co-expression of the β4 subunit caused the wild-type channel to be less sensitive to calcium at low Ca2+concentrations but had little effect on the mutant channel, further accentuating the difference between the wild-type and the mutant channels. In the absence of Ca2+, there was no difference in Mg2+or voltage sensitivity of the mutant and wild-type channels, whereas in 2 mM Ca2+, the mutant channel had greater open probability at every Mg2+concentration tested. We conclude that the D434G mutation modifies Ca2+-dependent activation, but we find no evidence of a direct effect on activation by Mg2+or voltage. The resulting enhancement of BK channel function leads to an increase in brain excitability, possibly due to more rapid repolarization of action potentials.
Triple Dissociation in the Medial Temporal Lobes: Recollection, Familiarity, and Novelty
Authors: Daselaar S. M. , Fleck M. S. , Cabeza R.
Published: June 2006

Memory for past events may be based on retrieval accompanied by specific contextual details (recollection) or on the feeling that an item is old (familiarity) or new (novelty) in the absence of contextual details. There are indications that recollection, familiarity, and novelty involve different medial temporal lobe subregions, but available evidence is scarce and inconclusive. Using functional magnetic resonance imaging (MRI), we isolated retrieval-related activity associated with recollection, familiarity, and novelty by distinguishing between linear and nonlinear oldness functions derived from recognition confidence levels. Within the medial temporal lobes (MTLs), we found a triple dissociation among the posterior half of the hippocampus, which was associated with recollection, the posterior parahippocampal gyrus, which was associated with familiarity, and anterior half of the hippocampus and rhinal regions, which were associated with novelty. Furthermore, multiple regression analyses based on individual trial activity showed that all three memory signals, i.e., recollection, familiarity, and novelty, make significant and independent contributions to recognition memory performance. Finally, functional dissociations among recollection, familiarity, and novelty were also found in posterior midline, left parietal cortex, and prefrontal cortex regions. This is the first study to reveal a triple dissociation within the MTL associated with distinct retrieval processes. This finding has direct implications for current memory models.
Mnt-Deficient Mammary Glands Exhibit Impaired Involution and Tumors with Characteristics of Myc Overexpression
Authors: Toyo-oka Kazuhito , Bowen Timothy J. , Hirotsune Shinji , Li Zirong , Jain Sonia , Ota Sara , Lozach Laure Escoubet , Bassett Ivan Garcia , Lozach Jean , Rosenfeld Michael G. , Glass Christopher K. , Eisenman Robert , Ren Bing , Hurlin Peter , Wynshaw-Boris Anthony
Published: June 2006

The proto-oncogene c-Myc plays a central role in cell growth and the development of human tumors. c-Myc interacts with Max and Myc-Max complexes bind to E-box and related sequences to activate transcription. Max also interacts with Mnt but Mnt-Max complexes repress transcription when bound to these sequences. MNT maps to human chromosome 17p13.3, a region frequently deleted in various human tumors, including mammary gland tumors. Consistent with the possibility that Mnt functions as a Myc antagonist, Mnt-deficient fibroblasts exhibit many of the hallmark characteristics of cells that overexpress Myc, and conditional (Cre/Lox) inactivation of Mnt in mammary gland epithelium leads to adenocarcinomas. Here, we further characterize mammary gland tissue following conditional deletion of Mnt in the mammary gland. We show that loss of Mnt severely disrupts mammary gland involution and leads to hyperplastic ducts associated with reduced numbers of apoptotic cells. These findings suggest that loss of Mnt in mammary tissue has similarities to Myc overexpression. We tested this directly by using promoter array analysis and mRNA expression analysis by oligonucleotide arrays. We found that Mnt and c-Myc bound to similar promoters in tumors from MMTV-c-Myc transgenic mice, and mRNA expression patterns were similar between mammary tumors from MMTV-Cre/MntKO/CKO and MMTV-c-Myc transgenic mice. These results reveal an important role for Mnt in pregnancy-associated mammary gland development and suggest that mammary gland tumorigenesis in the absence of Mnt is analogous to that caused by Myc deregulation. (Cancer Res 2006; 66(11): 5565-73)
Role of ETS Transcription Factors in the Hypoxia-Inducible Factor-2 Target Gene Selection
Authors: Aprelikova Olga , Wood Matthew , Tackett Sean , Chandramouli Gadisetti V.R. , Barrett J. Carl
Published: June 2006

Tumor hypoxia often directly correlates with aggressive phenotype, metastasis progression, and resistance to chemotherapy. Two transcription factors [hypoxia-inducible factor-1α (HIF-1α) and HIF-2α] are dramatically induced in hypoxic areas and regulate the expression of genes necessary for tumor adaptation to the conditions of low oxygen; however, the relative contribution of these factors is controversial. We used RNA interference–mediated inactivation of HIF-1α or HIF-2α followed by microarray analysis to identify genes specifically regulated by either HIF-1 or HIF-2 in hypoxia. We found that, in the MCF7 cell line, the vast majority of hypoxia-responsive genes (>80%) were dependent on the presence of HIF-1α. However, a small group of genes were preferentially regulated by HIF-2α. Promoter analysis for this group of genes revealed that all of them have putative binding sites for ETS family transcription factors, and 10 of 11 HIF-2α-dependent genes had at least one potential hypoxia-responsive element (HRE) in proximity to an ETS transcription factor binding site. Knockdown of ELK-1, the most often represented member of ETS family, significantly reduced hypoxic induction of the HIF-2α-dependent genes. Physical and functional interaction between ELK-1 and HIF-2α were supported by coimmunoprecipitation of these two proteins, luciferase reporter assay using CITED2 promoter, and binding of ELK-1 protein to the promoters of CITED2 and WISP2 genes in proximity to a HRE. These data suggest that the choice of the target genes by HIF-1 or HIF-2 depends on availability and cooperation of HIFs with other factors recognizing their cognate elements in the promoters. (Cancer Res 2006; 66(11): 5641-7)
Role of Src Kinases in Neu-Induced Tumorigenesis: Challenging the Paradigm Using Csk Homologous Kinase Transgenic Mice
Authors: Kaminski Rafal , Zagozdzon Radoslaw , Fu Yigong , Mroz Pawel , Fu Wei , Seng Seyha , Avraham Shalom , Avraham Hava Karsenty
Published: June 2006

Amplification of the HER-2/neu (ErbB2) gene is observed in ∼30% of human breast cancers, correlating with a poor clinical prognosis. Src kinases are also involved in the etiology of breast cancer, and their activation was suggested to be necessary for Neu-induced oncogenesis. To address whether Src activity is essential for Neu-mediated tumorigenesis, we used a physiologic inhibitor of Src kinase activity, the Csk homologous kinase (CHK), expressed as a mammary tissue-specific transgene. Our data, using a physiologic inhibitor of Src activity (CHK), showed that blocking of Neu-induced Src activity without altering Src expression levels had no significant effects on Neu-mediated mammary tumorigenesis in vivo. This contradicts the current paradigm that activation of Src kinases is essential for Neu-induced oncogenesis. This study is the first to distinguish between the kinase-dependent and kinase-independent actions of Src and shows that its kinase-dependent properties are not requisite for Neu-induced tumorigenesis. (Cancer Res 2006; 66(11): 5757-62)
Dissociation of Angiogenesis and Tumorigenesis in Follistatin- and Activin-Expressing Tumors
Authors: Krneta Jelena , Kroll Jens , Alves Frauke , Prahst Claudia , Sananbenesi Farahnaz , Dullin Christian , Kimmina Sarah , Phillips David J. , Augustin Hellmut G.
Published: June 2006

The transforming growth factor-β superfamily member activin and its antagonist, follistatin, act as a pleiotropic growth factor system that controls cell proliferation, differentiation, and apoptosis. Activin inhibits fibroblast growth factor 2–induced sprouting angiogenesis in vitro (spheroidal angiogenesis assay) and in vivo (Matrigel assay). To further study the role of the activin/follistatin system during angiogenesis and tumor progression, activin- and follistatin-expressing R30C mammary carcinoma cells were studied in mouse tumor experiments. Surprisingly, activin-expressing tumors grew much faster than follistatin-expressing tumors although they failed to induce increased angiogenesis (as evidenced by low microvessel density counts). Conversely, follistatin-expressing tumors were much smaller but had a dense network of small-diameter capillaries. Qualitative angioarchitectural analyses (mural cell recruitment, perfusion) revealed no major functional differences of the tumor neovasculature. Analysis of activin- and follistatin-expressing R30C cells identified a cell autonomous role of this system in controlling tumor cell growth. Whereas proliferation of R30C cells was not altered, follistatin-expressing R30C cells had an enhanced susceptibility to undergo apoptosis. These findings in experimental tumors are complemented by an intriguing case report of a human renal cell carcinoma that similarly shows a dissociation of angiogenesis and tumorigenesis during tumor progression. Collectively, the data shed further light into the dichotomous stimulating and inhibiting roles that the activin/follistatin system can exert during angiogenesis and tumor progression. Furthermore, the experiments provide a critical proof-of-principle example for the dissociation of angiogenesis and tumorigenesis, supporting the concept that tumor growth may not be dependent on increased angiogenesis as long as a minimal intratumoral microvessel density is maintained. (Cancer Res 2006; 66(11): 5686-95)
Synergistic Induction of Folate Receptor β by All-Trans Retinoic Acid and Histone Deacetylase Inhibitors in Acute Myelogenous Leukemia Cells: Mechanism and Utility in Enhancing Selective Growth Inhibition by Antifolates
Authors: Qi Huiling , Ratnam Manohar
Published: June 2006

The folate receptor (FR) type β is a promising target for therapeutic intervention in acute myelogenous leukemia (AML), owing particularly to its selective up-regulation in the leukemic cells by all-trans retinoic acid (ATRA). Here we show, using KG-1 and MV4-11 AML cells and recombinant 293 cells, that the histone deacetylase (HDAC) inhibitors trichostatin A (TSA), valproic acid (VPA), and FK228 potentiated ATRA induction of FR-β gene transcription and FR-β mRNA/protein expression. ATRA and/or TSA did not induce de novo FR synthesis in any of a variety of FR-negative cell lines tested. TSA did not alter the effect of ATRA on the expression of retinoic acid receptor (RAR) α, β, or γ. Chromatin immunoprecipitation assays indicate that HDAC inhibitors act on the FR-β gene by enhancing RAR-associated histone acetylation to increase the association of Sp1 with the basal FR-β promoter. Under these conditions, the expression level of Sp1 is unaltered. A decreased availability of putative repressor AP-1 proteins may also indirectly contribute to the effect of HDAC inhibitors. Finally, FR-β selectively mediated growth inhibition by (6S) dideazatetrahydrofolate in a manner that was greatly potentiated in AML cells by ATRA and HDAC inhibition. Therefore, the combination of ATRA and innocuous HDAC inhibitors may be expected to facilitate selective FR-β–targeted therapies in AML. (Cancer Res 2006; 66(11): 5875-82)
The Histone Deacetylase Inhibitor LBH589 Is a Potent Antimyeloma Agent that Overcomes Drug Resistance
Authors: Maiso Patricia , Carvajal-Vergara Xonia , Ocio Enrique M. , López-Pérez Ricardo , Mateo Gema , Gutiérrez Norma , Atadja Peter , Pandiella Atanasio , San Miguel Jesús F.
Published: June 2006

Multiple myeloma represents an incurable disease, for which development of new therapies is required. Here, we report the effect on myeloma cells of LBH589, a new hydroxamic acid–derived histone deacetylase inhibitor. LBH589 was a potent antimyeloma agent (IC50 < 40 nmol/L) on both cell lines and fresh cells from multiple myeloma patients, including cells resistant to conventional chemotherapeutic agents. In addition, LBH589 potentiated the action of drugs, such as bortezomib, dexamethasone, or melphalan. Using gene array, quantitative PCR, and Western analyses, we observed that LBH589 affected a large number of genes involved in cell cycle and cell death pathways. LBH589 blocked cell cycle progression, and this was accompanied by p21, p53, and p57 up-regulation. LBH589 induced cell death through an increase in the mitochondrial outer membrane permeability. LBH589 favored apoptosome formation by inducing cytochrome c release, Apaf-1 up-regulation, and caspase-9 cleavage. In addition, LBH589 stimulated a caspase-independent pathway through the release of AIF from the mitochondria. LBH589 down-regulated Bcl-2 and particularly Bcl-X. Moreover, overexpression of Bcl-X in multiple myeloma cells prevented LBH589-induced cell death. All these data indicate that LBH589 could be a useful drug for the treatment of multiple myeloma patients. (Cancer Res 2006; 66(11): 5781-9)
Recombinant Baculovirus Containing the Diphtheria Toxin A Gene for Malignant Glioma Therapy
Authors: Wang Chao-Yang , Li Feng , Yang Yi , Guo Hai-Yan , Wu Chun-Xiao , Wang Shu
Published: June 2006

Insect baculoviruses are capable of infecting mammalian glial cells in the central nervous system. We investigated in the current study the feasibility of using the viruses as toxin gene vectors to eliminate malignant glioma cells in the brain. We first confirmed that glioma cells were permissive to baculovirus infection, with variable transduction efficiencies at 100 viral particles per cell and ranging between 35% and 70% in seven human and rat glioma cell lines. We then developed a recombinant baculovirus vector accommodating the promoter of glial fibrillary acidic protein (GFAP) to minimize possible side effects caused by overexpression of a therapeutic gene in sensitive neurons. We placed the GFAP promoter into a baculovirus expression cassette, in which the enhancer of human cytomegalovirus immediate-early gene and the inverted terminal repeats of adeno-associated virus were employed to improve the relatively low transcriptional activity of the cellular promoter. This recombinant baculovirus significantly improved transduction in glioma cells, providing the efficiency in C6 rat glioma cells up to 96%. When used to produce the A-chain of diphtheria toxin intracellularly in a rat C6 glioma xenograft model, the baculovirus effectively suppressed tumor development. The new baculovirus vector circumvents some of the inherent problems associated with mammalian viral vectors and provides an additional option for cancer gene therapy. (Cancer Res 2006; 66(11): 5798-806)
CD4+ T-Cell Response to MitochondrialCytochrome bin Human Melanoma
Authors: Voo Kui Shin , Zeng Gang , Mu Jian-Bing , Zhou Juhua , Su Xin-Zhuan , Wang Rong-Fu
Published: June 2006

Mitochondrial DNA (mtDNA) is highly susceptible to mutations due to the low level of DNA repair and the presence of a high level of reactive oxygen species in the organelle. Although mtDNA mutations have been implicated in degenerating diseases, aging, and cancer, very little is known about the role of T cells in immunosurveillance for mtDNA aberrations. Here, we describe T-cell recognition of a peptide translated from an alternative open reading frame of the mitochondrial cytochrome b (cyt b) gene in melanoma cells established from a patient. To understand how the cyt b gene is transcribed and translated in tumor cells, we found that cyt b–specific CD4+ T cells only recognized protein fractions derived from cytoplasm and not from mitochondria. However, T-cell recognition of tumor cells could be inhibited by treatment of tumor cells with rhodamine 6G inhibitor, which depletes mitochondria. These findings suggest that cyt b mRNA is leaked out of the mitochondria and then translated in the cytoplasm for presentation to CD4+ T cells. The cyt b cDNAs from this patient contain highly heteroplasmic transition mutations compared with control cell lines, suggesting a compromise of mitochondrial integrity that may have contributed to melanoma induction or progression. These findings provide the first example of a mitochondrial immune target for CD4+ T cells and therefore have implications for the immunosurveillance of mitochondrial aberrations in cancer patients. (Cancer Res 2006; 66(11): 5919-26)
Grape Seed Extract Is an Aromatase Inhibitor and a Suppressor of Aromatase Expression
Authors: Kijima Ikuko , Phung Sheryl , Hur Gene , Kwok Sum-Ling , Chen Shiuan
Published: June 2006

Aromatase is the enzyme that converts androgen to estrogen. It is expressed at higher levels in breast cancer tissues than normal breast tissues. Grape seed extract (GSE) contains high levels of procyanidin dimers that have been shown in our laboratory to be potent inhibitors of aromatase. In this study, GSE was found to inhibit aromatase activity in a dose-dependent manner and reduce androgen-dependent tumor growth in an aromatase-transfected MCF-7 (MCF-7aro) breast cancer xenograft model, agreeing with our previous findings.

We have also examined the effect of GSE on aromatase expression. Reverse transcription-PCR experiments showed that treatment with 60 μg/mL of GSE suppressed the levels of exon I.3–, exon PII–, and exon I.6–containing aromatase mRNAs in MCF-7 and SK-BR-3 cells. The levels of exon I.1–containing mRNA, however, did not change with GSE treatment. Transient transfection experiments with luciferase-aromatase promoter I.3/II or I.4 reporter vectors showed the suppression of the promoter activity in a dose-dependent manner. The GSE treatment also led to the down-regulation of two transcription factors, cyclic AMP-responsive element binding protein-1 (CREB-1) and glucocorticoid receptor (GR). CREB-1 and GR are known to up-regulate aromatase gene expression through promoters I.3/II and I.4, respectively. We believe that these results are exciting in that they show GSE to be potentially useful in the prevention/treatment of hormone-dependent breast cancer through the inhibition of aromatase activity as well as its expression. (Cancer Res 2006; 66(11): 5960-7)
Connective Tissue Growth Factor–Specific Monoclonal Antibody Therapy Inhibits Pancreatic Tumor Growth and Metastasis
Authors: Dornhöfer Nadja , Spong Suzanne , Bennewith Kevin , Salim Ali , Klaus Stephen , Kambham Neeraja , Wong Carol , Kaper Fiona , Sutphin Patrick , Nacalumi Rendall , Höckel Michael , Le Quynh , Longaker Michael , Yang George , Koong Albert , Giaccia Amato
Published: June 2006

Pancreatic cancer is highly aggressive and refractory to most existing therapies. Past studies have shown that connective tissue growth factor (CTGF) expression is elevated in human pancreatic adenocarcinomas and some pancreatic cancer cell lines. To address whether and how CTGF influences tumor growth, we generated pancreatic tumor cell lines that overexpress different levels of human CTGF. The effect of CTGF overexpression on cell proliferation was measured in vitro in monolayer culture, suspension culture, or soft agar, and in vivo in tumor xenografts. Although there was no effect of CTGF expression on proliferation in two-dimensional cultures, anchorage-independent growth (AIG) was enhanced. The capacity of CTGF to enhance AIG in vitro was linked to enhanced pancreatic tumor growth in vivo when these cells were implanted s.c. in nude mice. Administration of a neutralizing CTGF-specific monoclonal antibody, FG-3019, had no effect on monolayer cell proliferation, but blocked AIG in soft agar. Consistent with this observation, anti-CTGF treatment of mice bearing established CTGF-expressing tumors abrogated CTGF-dependent tumor growth and inhibited lymph node metastases without any toxicity observed in normal tissue. Together, these studies implicate CTGF as a new target in pancreatic cancer and suggest that inhibition of CTGF with a human monoclonal antibody may control primary and metastatic tumor growth. (Cancer Res 2006; 66(11): 5816-27)
Down-regulation of Polo-like Kinase 1 Elevates Drug Sensitivity of Breast Cancer CellsIn vitroandIn vivo
Authors: Spänkuch Birgit , Heim Sandra , Kurunci-Csacsko Elisabeth , Lindenau Christine , Yuan Juping , Kaufmann Manfred , Strebhardt Klaus
Published: June 2006

Human polo-like kinase 1 (Plk1) is a key player in different stages of mitosis and modulates the spindle checkpoint at the metaphase-anaphase transition. Overexpression of Plk1 is observed in various human tumors and it is a negative prognostic factor in patients suffering from diverse cancers. We used phosphorothioate antisense oligonucleotides (ASO) targeted against Plk1, together with paclitaxel, carboplatin, and Herceptin, for the treatment of breast cancer cells to identify conditions for enhanced drug sensitivity. After transfection of the breast cancer cell lines BT-474, MCF-7, and MDA-MB-435 with Plk1-specific ASOs, paclitaxel, carboplatin, or Herceptin was added and cell proliferation, cell cycle distribution, and apoptosis were measured. Whereas the dual treatment of breast cancer cells with Plk1-specific ASOs with carboplatin or Herceptin caused only a limited antiproliferative effect in breast cancer cells, we observed synergistic effects after combination of low doses of Plk1-specific ASOs with paclitaxel, which is used in a variety of clinical anticancer regimens. Plk1-specific ASOs also acted synergistically with paclitaxel in the arrest of the cell cycle at the G2-M phase and in the induction of apoptosis. Interestingly, in a human xenograft experiment using MDA-MB-435 cells, the combination of Plk1 ASOs with paclitaxel led to synergistic reduction of tumor growth after 3 weeks of treatment compared with either agent alone. This study suggests that antisense inhibitors against Plk1 at well-tolerated doses may be considered as highly efficient promoters for the antineoplastic potential of taxanes, such as paclitaxel, causing synergistic effects in breast cancer cells. (Cancer Res 2006; 66(11): 5836-46)
AKT Activation in Human Glioblastomas Enhances Proliferation via TSC2 and S6 Kinase Signaling
Authors: Riemenschneider Markus J. , Betensky Rebecca A. , Pasedag Saskia M. , Louis David N.
Published: June 2006

Aberrant AKT (protein kinase B) signaling is common in many cancers, including glioblastoma. Current models suggest that AKT acts directly, or indirectly via the TSC complex, to activate the mammalian target of rapamycin (mTOR) as the main downstream mediator of AKT signaling. mTOR activation results in subsequent activation of S6K and STAT3, as well as suppression (i.e., phosphorylation) of 4E-BP1, leading to cell cycle progression and inhibition of apoptosis. Most studies of this pathway have used in vitro systems or tumor lysate–based approaches. We aimed to delineate these pathways in a primarily in situ manner using immunohistochemistry in a panel of 29 glioblastomas, emphasizing the histologic distribution of molecular changes. Within individual tumors, increased expression levels of p-TSC2, p-mTOR, p-4E-BP1, p-S6K, p-S6, and p-STAT3 were found in regions defined by elevated AKT activation. However, only TSC2, S6K, and S6 activation levels correlated significantly with AKT activation and clustered together in multidimensional scaling analyses. Ki-67 proliferation indices were significantly elevated in p-AKT-overexpressing regions, whereas expression of the apoptosis marker cleaved caspase 3 was generally low and not significantly different between the regions. These findings provide the first in vivo evidence for a close correlation between AKT and TSC2 phosphorylation levels in glioblastoma. Moreover, they suggest that downstream p-AKT effects are primarily mediated by S6 kinase signaling, thus enhancing proliferation rather than inhibiting apoptosis. (Cancer Res 2006; 66(11): 5618-23)
A Systems Approach to Model Metastatic Progression
Authors: Taylor Barry S. , Varambally Sooryanarayana , Chinnaiyan Arul M.
Published: June 2006

Proteomic profiling of human disease has seen much early activity with the accessibility of the newest generation of high-throughput platforms and technologies. Nevertheless, the nature of the dynamic physiologic milieu and high dimensionality of the data has complicated major diagnostic and prognostic breakthroughs. Our recent article in Cancer Cell delineates an integrative model for culling a molecular signature of metastatic progression in prostate cancer from proteomic and transcriptomic analyses and shows its facility as a predictor of prognosis. The study leveraged direct proteomic analysis of tumor tissue extracts, differential feature selection characterizing the proteomic alterations of prostate cancer subclasses, and integration with public and study-derived genomic data to construct a multiplex gene signature representing progression of indolent cancer to aggressive disease. This further predicted clinical outcome in a variety of solid tumors. This review describes the context of the work, the framework for the analysis itself, and a look forward to the promise of this systems approach to human disease. (Cancer Res 2006; 66(11): 5537-9)
Human Papillomavirus Type 16 E7 Up-regulates AKT Activity through the Retinoblastoma Protein
Authors: Menges Craig W. , Baglia Laurel A. , Lapoint Randi , McCance Dennis J.
Published: June 2006

Human papillomaviruses (HPV) are small DNA tumor viruses causally associated with cervical cancer. The early gene product E7 from high-risk HPV is considered the major transforming protein expressed by the virus. Although many functions have been described for E7 in disrupting normal cellular processes, we describe in this study a new cellular target in primary human foreskin keratinocytes (HFK), the serine/threonine kinase AKT. Expression of HPV type 16 E7 in HFK caused inhibition of differentiation, hyperproliferation, and up-regulation of AKT activity in organotypic raft cultures. The ability of E7 to up-regulate AKT activity is dependent on its ability to bind to and inactivate the retinoblastoma (Rb) gene product family of proteins. Furthermore, we show that knocking down Rb alone, with short hairpin RNAs, was sufficient to up-regulate AKT activity in differentiated keratinocytes. Up-regulation of AKT activity and loss of Rb was also observed in HPV-positive cervical high-grade squamous intraepithelial lesions when compared with normal cervical tissue. Together, these data provide evidence linking inactivation of Rb by E7 in the up-regulation of AKT activity during cervical cancer progression. (Cancer Res 2006; 66(11): 5555-9)
A Modular Analysis of Breast Cancer Reveals a Novel Low-Grade Molecular Signature in Estrogen Receptor–Positive Tumors
Authors: Yu Kun , Ganesan Kumaresan , Miller Lance D. , Tan Patrick
Published: June 2006

Purpose: Previous reports using genome-wide gene expression data to classify breast tumors have typically used standard unsupervised or supervised techniques, both of which have known limitations. We hypothesized that novel clinically relevant information could be revealed in these data sets by an alternative analytic approach. Using a recently described algorithm, signature analysis (SA), we identified “modules,” comprising groups of tightly coexpressed genes that are conditionally linked to particular tumors, in a series of breast tumor gene expression profiles.

Experimental Design and Results: The SA successfully identified multiple breast cancer modules specifically linked to distinct biological functions. We identified a novel module, TuM1, whose presence was not readily discernible by conventional clustering techniques. The TuM1 module is expressed in a subset of estrogen receptor (ER)–positive tumors and is significantly enriched with genes involved in apoptosis and cell death. Clinically, TuM1-expressing tumors are associated with low histopathologic grade, and this association is independent of the inherent ER status of a tumor. We confirmed the robustness and general applicability of TuM1 module by demonstrating its association with low tumor grade in multiple independent breast cancer data sets generated using different array technologies. In vitro, the TuM1 module is down-regulated in ER+ MCF7 cells upon treatment with tamoxifen, suggesting that TuM1 expression may be dependent on active signaling by ER. Initial data is also suggestive that TuM1 expression may be clinically associated with a patient's response to antihormonal therapy.

Conclusion: Our results suggest that modular-based approaches toward gene expression data can prove useful in identifying novel, robust, and biologically relevant signatures even from data sets that have been the subject of substantial prior analysis.
Overexpression of Focal Adhesion Kinase in Head and Neck Squamous Cell Carcinoma Is Independent of fak Gene Copy Number
Authors: Canel Marta , Secades Pablo , Rodrigo Juan-Pablo , Cabanillas Rubén , Herrero Agustín , Suarez Carlos , Chiara María-Dolores
Published: June 2006

The development of human malignancies can involve the aberrant regulation of intracellular signal transduction pathways that regulate cell-extracellular matrix interactions.

Purpose: In the current study, we aimed to evaluate focal adhesion kinase (FAK) at both genetic and protein expression levels in head and neck squamous cell carcinomas (HNSCC) and to explore the prognostic significance of FAK.

Experimental Design: A total of 211 tissue specimens, including 147 primary tumors, 56 lymph node metastases, 3 benign hyperplasias, and 5 dysplasias, were analyzed using immunohistochemistry. The fak gene dosage was determined in 33 tumors. Correlations among DNA, protein, and clinicopathologic variables were analyzed.

Results: FAK protein was overexpressed in HNSCCs compared with corresponding normal mucosa. High expression levels were found in 62% of the samples. Positive immunostaining was also detected in benign hyperplasias and preinvasive dysplastic lesions. All lymph node metastases examined showed FAK overexpression, with significant correlation with the expression in matched primary tumor. DNA copy number ratios for fak were higher in 39% of the tumors compared with normal mucosa. However, elevated FAK expression did not correlate with gains on DNA level, and not all cases with an amplification of the fak gene displayed protein overexpression. Similar data were obtained in five HNSCC-derived cell lines, in which FAK mRNA levels were precisely correlated with FAK protein levels. FAK protein overexpression in tumors correlated with nodal metastases.

Conclusions: These findings suggest an involvement of FAK in the onset and progression of HNSCC and provide an insight into a mechanism of FAK activation alternative to gene amplification.
The Coincidence of Chromosome 15 Aberrations and β2-Microglobulin Gene Mutations Is Causative for the Total Loss of Human Leukocyte Antigen Class I Expression in Melanoma
Authors: Paschen Annette , Arens Norbert , Sucker Antje , Greulich-Bode Karin M. , Fonsatti Ester , Gloghini Annunziata , Striegel Sandra , Schwinn Nicole , Carbone Antonino , Hildenbrand Ralf , Cerwenka Adelheid , Maio Michele , Schadendorf Dirk
Published: June 2006

Purpose: Total loss of surface presentation of human leukocyte antigen (HLA) class I molecules, protecting tumor cells from the recognition by cytotoxic host CD8+ T cells, is known to be caused by mutations in the β2-microglobulin (β2m) gene. We asked whether abnormalities of chromosome 15, harboring the β2m gene on 15q21, in addition to β2m gene mutations, are causative for the HLA class I–negative phenotype of melanoma cells.

Experimental Design: To answer this, we established primary cell lines from the β2m-negative metastatic melanoma tissues of four different patients and analyzed them for β2m gene mutations and chromosome 15 aberrations, the latter by loss of heterozygosity analysis, fluorescence in situ hybridization (FISH), and multicolor FISH.

Results: Mutations at the β2m gene level were detected in all cell lines. The loss of heterozygosity analysis of microsatellite markers located on chromosome 15 in three of the four cell lines pointed to an extensive loss of chromosome 15 material. Subsequent molecular cytogenetic analysis revealed the coexistence of apparently normal and rearranged versions of chromosome 15 in three cell lines whereas the fourth cell line solely showed rearranged versions. Two of the four cell lines exhibited a special type of intrachromosomal rearrangement characterized by FISH signals specific for the subtelomeric region of 15q at both ends of the chromosome and one centromeric signal in between.

Conclusions: Our data indicate that the complete loss of HLA class I expression in melanoma cells is due to the coincidence of the following mutational events: (a) chromosome 15 instability associated with an extensive loss of genetic material and (b) β2m gene mutations.
Loss of β4 Integrin Subunit Reduces the Tumorigenicity of MCF7 Mammary Cells and Causes Apoptosis upon Hormone Deprivation
Authors: Bon Giulia , Folgiero Valentina , Bossi Gianluca , Felicioni Laura , Marchetti Antonio , Sacchi Ada , Falcioni Rita
Published: June 2006

Purpose: The α6β4 integrin, a laminin receptor, has been implicated from many studies in tumor progression and invasion. We showed that the β4 integrin subunit associates with the ErbB-2 tyrosine kinase in human mammary carcinoma cell lines and that its overexpression in NIH3T3/ErbB-2–transformed cells causes a constitutive activation of phosphatidylinositol 3-kinase (PI3K), inducing a strong increase of their invasive capacity. In this study, we investigated the biological consequences of interference with the endogenous β4 integrin subunit expression.

Experimental Design: In vitro and in vivo tumor growth and the biochemical consequences of β4 integrin inactivation were studied in mammary tumor cells by using short hairpin RNA approach.

Results: Our data show that tumor growth of mammary tumor cells strictly depends on β4 expression, confirming the relevance of β4 protein in these cells. Moreover, interference with β4 expression significantly reduces endogenous PI3K activity and AKT and mammalian target of rapamycin phosphorylation. Accordingly, with these results and considering that PI3K activity in mammary tumor plays a relevant role in hormone resistance, we asked whether β4 expression might be relevant for hormone responsiveness in these cells. Data reported indicate that the interference with endogenous β4 expression, upon hormone deprivation, induces caspase-9 and cytochrome c–mediated apoptosis, which is enhanced upon tamoxifen treatment. On the other hand, the expression of myr-AKT in MCF7 β4–short hairpin RNA cells rescues the cells from apoptosis in the absence of hormones and upon tamoxifen treatment.

Conclusions: Overall, these results confirm the relevance of β4 expression in mammary tumors and indicate this integrin as a relevant target for tumor therapy.