A graphene mesh as a hybrid electrode for foldable devices

A graphene mesh with arrays of micro-holes was fabricated on a polymer substrate using photolithography for use as an electrode in flexible devices. The optimal mesh structure with high optical transmittance and electrical conductivity was designed using a finite element method, in which the conductivity of the mesh was simulated as a function of structure, size, and periodicity of the hole array. The sheet resistance of the graphene mesh was lowered to that of a graphene monolayer by chemical doping and found to be 330 Ω Sq^-1 at 98.5% transparency. The figure of merit of the doped graphene mesh was calculated to be 106 at 98% transmittance, a value that has not yet been reported for any conventional transparent electrode material. Due to strong bonding between the polymer and substrate, the hybrid electrode composed of a silver nanowire (AgNW)/graphene mesh coated with an over-coating layer exhibited more stable electrical characteristics during mechanical fatigue deformation compared to a hybrid film composed of a AgNW/graphene sheet. The AgNW/graphene sheet underwent breakdown at less than 20 000 cycles in cyclic bending tests with 6.5% strain, but the AgNW/graphene mesh showed a 38% increase in resistance at 20 000 cycles and no breakdown even at 100 000 cycles. Therefore, in this study, we propose a hybrid structure composed of a AgNW/graphene mesh, which is optically and mechanically superior to AgNW/graphene sheets, and therefore suitable for application as a transparent electrode in foldable devices with long-term stability.

Five-year decreased incidence of surgical site infections following gastrectomy and prosthetic joint replacement surgery through active surveillance by the Korean Nosocomial Infection Surveillance System

BACKGROUND

Surveillance of healthcare-associated infection has been associated with a reduction in surgical site infection (SSI).

AIM

To evaluate the Korean Nosocomial Infection Surveillance System (KONIS) in order to assess its effects on SSI since it was introduced.

METHODS

SSI data after gastrectomy, total hip arthroplasty (THA), and total knee arthroplasty (TKA) between 2008 and 2012 were analysed. The pooled incidence of SSI was calculated for each year; the same analyses were also conducted from hospitals that had participated in KONIS for at least three consecutive years. Standardized SSI rates for each year were calculated by adjusting for SSI risk factors. SSI trends were analysed using the Cochran-Armitage test.

FINDINGS

The SSI rate following gastrectomy was 3.12% (522/16,918). There was a significant trend of decreased crude SSI rates over five years. This trend was also evident in analysis of hospitals that had participated for more than three years. The SSI rate for THA was 2.05% (157/7656), which decreased significantly from 2008 to 2012. The risk factors for SSI after THA included the National Nosocomial Infections Surveillance risk index, trauma, reoperation, and age (60-69 years). The SSI rate for TKA was 1.90% (152/7648), which also decreased significantly during a period of five years. However, the risk-adjusted analysis of SSI did not show a significant decrease for all surgical procedures.

CONCLUSION

The SSI incidence of gastrectomy and prosthetic joint replacement declined over five years as a result of active surveillance by KONIS.

Loss of PTEN induces microtentacles through PI3K-independent activation of cofilin

Loss of PTEN tumor suppressor enhances metastatic risk in breast cancer, although the underlying mechanisms are poorly defined. We report that homozygous deletion of PTEN in mammary epithelial cells induces tubulin-based microtentacles (McTNs) that facilitate cell reattachment and homotypic aggregation. Treatment with contractility-modulating drugs showed that McTNs in PTEN(-/-) cells are suppressible by controlling the actin cytoskeleton. Because outward microtubule extension is counteracted by actin cortical contraction, increased activity of actin-severing proteins could release constraints on McTN formation in PTEN(-/-) cells. One such actin-severing protein, cofilin, is activated in detached PTEN(-/-) cells that could weaken the actin cortex to promote McTNs. Expression of wild-type cofilin, an activated mutant (S3A), and an inactive mutant (S3E) demonstrated that altering cofilin phosphorylation directly affects McTNs formation. Chemical inhibition of PI3K did not reduce McTNs or inactivate cofilin in PTEN(-/-) cells. Additionally, knock-in expression of the two most common PI3K-activating mutations observed in human cancer patients did not increase McTNs or activate cofilin. PTEN loss and PI3K activation also caused differential activation of the cofilin regulators, LIM-kinase1 (LIMK) and Slingshot-1L (SSH). Furthermore, McTNs were suppressed and cofilin was inactivated by restoration of PTEN in the PTEN(-/-) cells, indicating that both the elevation of McTNs and the activation of cofilin are specific results arising from PTEN loss. These data identify a novel mechanism by which PTEN loss could remodel the cortical actin network to facilitate McTNs that promote tumor cell reattachment and aggregation. Using isogenic MCF-10A PTEN(-/-) and PIK3CA mutants, we have further demonstrated that there are clear differences in activation of cofilin, LIMK and SSH between PTEN loss and PI3K activation, providing a new evidence that these mutations yield distinct cytoskeletal phenotypes, which could have an impact on tumor biology.

Abstract 3630: Non-enrichment based method for analysis of androgen receptor expression in circulating tumor cells (CTCs) in patients with metastatic castrate resistant prostate cancer

Background: We have established a fluid phase biopsy approach that identifies CTCs which preserves cytologic features in high-definition (HD) for diagnostic pathology without using immune or surface receptor-based enrichment. HD-CTCs identified with this approach can be used for enumeration and molecular characterization. Methods: Blood was collected from metastatic prostate cancer patients and normal donors in Cyto-Chex® tubes (Streck, Omaha, NE) as part of IRB approved protocols at each site. Following erythrocyte lysis, 3 million nucleated cells were deposited on a glass slide. Samples were incubated with a pan-cytokeratin (CK), CD45, and androgen receptor (AR) antibodies and counter-stained with DAPI. LNCaP cells were spiked into normal blood. Images were obtained with a fluorescent scanning microscope and analyzed with a computer algorithm. Candidate HD-CTCs were subsequently verified by expert readers. Slides were re-imaged for quantitative analysis using at a fixed exposure and gain. Results: A total of 227 CTCs from ten patients were compared to 20 LNCaP cells. The median (range) HD-CTCs in this cohort was: 9 (1-62) cells/ml. The mean ± standard deviation measurements in HD-CTCs were observed: CK intensity 60.4±154; total cell area 89.0 ± 53.8 μm2; nuclear area 61.1 ± 36.0 μm2. LNCaP cells spiked into normal blood gave the following values: CK intensity 1166+/−306; total cell area 143 ± 48.1 μm2; nuclear area 63.1 ± 18.6 μm2. CTCs were additionally classified as either AR positive (AR+) or AR negative (AR-). 37 of the 227 (16.3%) HD-CTCs were AR+. The average CK intensity was significantly higher in AR+ versus AR- cells at 174.23 and 39.86, respectively (p<0.001). The AR expression intensity in AR+ HD-CTCs and LNCaP cells was comparable at 979.4 and 902.2, respectively (p=0.824). Conclusions: We find a positive association between AR and CK expression on a per cell basis. Further, we find AR is expressed at comparable levels in CTCs from patients and human prostate cancer cells in culture. The HD-CTC based approach may be used for enumeration and molecular interrogation of CTCs in patients with prostate cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3630. doi:1538-7445.AM2012-3630

Non-enrichment-based method for analysis of androgen receptor expression in circulating tumor cells (CTCs) in patients with metastatic castrate-resistant prostate cancer

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Background: We have established a fluid phase biopsy approach that identifies CTCs which preserves cytologic features in high-definition (HD) for diagnostic pathology without using immune or surface receptor-based enrichment. HD-CTCs identified with this approach can be used for enumeration and molecular characterization.

Methods: Blood was collected from metastatic prostate cancer patients and normal donors in Cyto-Chex tubes (Streck, Omaha, NE) as part of IRB approved protocols at each site. Following erythrocyte lysis, 3 million nucleated cells were deposited on a glass slide. Samples were incubated with a pan-cytokeratin (CK), CD45, and androgen receptor (AR) antibodies and counter-stained with DAPI. LNCaP cells were spiked into normal blood. Images were obtained with a fluorescent scanning microscope and analyzed with a computer algorithm. Candidate HD-CTCs were subsequently verified by expert readers. Slides were re-imaged for quantitative analysis using at a fixed exposure and gain.

Results: A total of 227 CTCs from ten patients were compared to 20 LNCaP cells. The median (range) HD-CTCs in this cohort was: 9 (1-62) cells/ml. The mean ± standard deviation measurements in HD-CTCs were observed: CK intensity 60.4±154; total cell area 89.0 ± 53.8 µm2; nuclear area 61.1 ± 36.0 µm2. LNCaP cells spiked into normal blood gave the following values: CK intensity 1166+/−306; total cell area 143 ± 48.1 µm2; nuclear area 63.1 ± 18.6 µm2. CTCs were additionally classified as either AR positive (AR+) or AR negative (AR−). 37 of the 227 (16.3%) HD-CTCs were AR+. The average CK intensity was significantly higher in AR+ versus AR− cells at 174.23 and 39.86, respectively (p<0.001). The AR expression intensity in AR+ HD-CTCs and LNCaP cells was comparable at 979.4 and 902.2, respectively (p=0.824).

Conclusions: We find a positive association between AR and CK expression on a per cell basis. Further, we find AR is expressed at comparable levels in CTCs from patients and human prostate cancer cells in culture. The HD-CTC based approach may be used for enumeration and molecular interrogation of CTCs in patients with prostate cancer.

Cytometric comparisons between circulating tumor cells from prostate cancer patients and the prostate-tumor-derived LNCaP cell line

Many important experiments in cancer research are initiated with cell line data analysis due to the ease of accessibility and utilization. Recently, the ability to capture and characterize circulating tumor cells (CTCs) has become more prevalent in the research setting. This ability to detect, isolate and analyze CTCs allows us to directly compare specific protein expression levels found in patient CTCs to cell lines. In this study, we use immunocytochemistry to compare the protein expression levels of total cytokeratin (CK) and androgen receptor (AR) in CTCs and cell lines from patients with prostate cancer to determine what translational insights might be gained through the use of cell line data. A non-enrichment CTC detection assay enables us to compare cytometric features and relative expression levels of CK and AR by indirect immunofluorescence from prostate cancer patients against the prostate cancer cell line LNCaP. We measured physical characteristics of these two groups and observed significant differences in cell size, fluorescence intensity and nuclear to cytoplasmic ratio. We hope that these experiments will initiate a foundation to allow cell line data to be compared against characteristics of primary cells from patients.

Characterization of circulating tumor cell aggregates identified in patients with epithelial tumors

Circulating tumor cells (CTCs) have been implicated as a population of cells that may seed metastasis and venous thromboembolism (VTE), two major causes of mortality in cancer patients. Thus far, existing CTC detection technologies have been unable to reproducibly detect CTC aggregates in order to address what contribution CTC aggregates may make to metastasis or VTE. We report here an enrichment-free immunofluorescence detection method that can reproducibly detect and enumerate homotypic CTC aggregates in patient samples. We identified CTC aggregates in 43% of 86 patient samples. The fraction of CTC aggregation was investigated in blood draws from 24 breast, 14 non-small cell lung, 18 pancreatic, 15 prostate stage IV cancer patients and 15 normal blood donors. Both single CTCs and CTC aggregates were measured to determine whether differences exist in the physical characteristics of these two populations. Cells contained in CTC aggregates had less area and length, on average, than single CTCs. Nuclear to cytoplasmic ratios between single CTCs and CTC aggregates were similar. This detection method may assist future studies in determining which population of cells is more physically likely to contribute to metastasis and VTE.

Fluid biopsy for circulating tumor cell identification in patients with early-and late-stage non-small cell lung cancer: a glimpse into lung cancer biology

Circulating tumor cell (CTC) counts are an established prognostic marker in metastatic prostate, breast and colorectal cancer, and recent data suggest a similar role in late stage non-small cell lung cancer (NSCLC). However, due to sensitivity constraints in current enrichment-based CTC detection technologies, there are few published data about CTC prevalence rates and morphologic heterogeneity in early-stage NSCLC, or the correlation of CTCs with disease progression and their usability for clinical staging. We investigated CTC counts, morphology and aggregation in early stage, locally advanced and metastatic NSCLC patients by using a fluid-phase biopsy approach that identifies CTCs without relying on surface-receptor-based enrichment and presents them in sufficiently high definition (HD) to satisfy diagnostic pathology image quality requirements. HD-CTCs were analyzed in blood samples from 78 chemotherapy-naïve NSCLC patients. 73% of the total population had a positive HD-CTC count (>0 CTC in 1 mL of blood) with a median of 4.4 HD-CTCs mL⁻¹ (range 0-515.6) and a mean of 44.7 (±95.2) HD-CTCs mL⁻¹. No significant difference in the medians of HD-CTC counts was detected between stage IV (n = 31, range 0-178.2), stage III (n = 34, range 0-515.6) and stages I/II (n = 13, range 0-442.3). Furthermore, HD-CTCs exhibited a uniformity in terms of molecular and physical characteristics such as fluorescent cytokeratin intensity, nuclear size, frequency of apoptosis and aggregate formation across the spectrum of staging. Our results demonstrate that despite stringent morphologic inclusion criteria for the definition of HD-CTCs, the HD-CTC assay shows high sensitivity in the detection and characterization of both early- and late-stage lung cancer CTCs. Extensive studies are warranted to investigate the prognostic value of CTC profiling in early-stage lung cancer. This finding has implications for the design of extensive studies examining screening, therapy and surveillance in lung cancer patients.

Abstract 4151: High definition circulating tumor cells in patients with non-small cell lung cancer

Circulating tumor cell (CTC) counts are an established prognostic marker in metastatic prostate, breast, and colorectal cancer. However, there is little knowledge about CTC incidence rates and morphologic heterogeneity in non-small cell lung cancer (NSCLC) and their correlation to disease progression and usability for clinical staging. Here, we present a fluid phase biopsy approach that identifies CTCs without surface receptor-based enrichment, and presents them in sufficiently high definition (HD) to satisfy diagnostic pathology image quality requirements. The HD-CTC assay will be used to monitor HD-CTC counts and morphology in early stage, locally advanced, and metastatic NSCLC patient over time. 150 newly diagnosed NSCLC patients are being enrolled for this project. At the time of diagnosis 50 of the patients will have early stage cancers (stage I-II); 50 patients will have locally advanced (stage III) cancers, and 50 will be patients presenting with metastatic (stage IV) disease. Blood samples from each patient will be obtained at the time of diagnosis and 6 months later. We present here an interim data set that shows an incidence rate of 78% at baseline with a median CTC count of 19.5/ml of blood (range 0-441.6). Our preliminary data demonstrates that, despite stringent morphologic inclusion criteria for the definition of HD-CTCs, our HD-CTC assay shows high sensitivity in the detection of lung cancer CTCs.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4151. doi:10.1158/1538-7445.AM2011-4151

Abstract 5225: Quantification of circulating tumor cell aggregates in breast cancer patient blood using an enrichment-free detection method

Circulating tumor cells (CTCs) have been implicated as a potential population of cells that may seed metastasis in cancer patients. In order to characterize and understand this population of cells, an enrichment-free immunofluorescence detection method was developed by our lab. This method take whole patient blood and classifies cells based on cytokeratin (CTCs) and CD45 (WBCs) antibody staining. Using this CTC detection method, a population of cells residing in tumor cell aggregates was observed in blood draws from Stage IV breast cancer patients. It was previously observed in ex vivo mouse experiments that homotypic aggregate formation of tumor cells may increase metastatic efficiency (Glinsky, et al., Cancer Research, 2003). In this work, we seek to determine if a significant proportion of CTCs reside in homotypic aggregates in patient blood by enumerating CTC aggregates from the blood draws of 23 Stage IV breast cancer patients and 16 healthy donor patients. Preliminary analysis measuring associations of CTCs with other nucleated cells found in patient blood draws revealed that ∼43% of cytokeratin-positive (CK+) cells found in breast cancer patient samples localize with either other CK+ or white blood cells (WBCs) versus 14% in healthy donor patient samples. Furthermore, ∼19% of WBCs were found to be associated with either CK+ or other WBCs in breast cancer patient samples versus ∼7% in healthy donor patient samples. Pathological review confirming CK+ cells as CTCs revealed that of the CTCs detected in patient blood after pathological review, ∼2% of CTCs were found as homotypic aggregates versus ∼0.07% in healthy donor samples (p=0.0005). Four breast cancer patients were found to have no CTC aggregates. Two breast cancer patients had significantly higher than average CTC aggregate percentages (∼6% and ∼7%). Patients will continue to be monitored to measure any differences in disease outcome of patients with high incidence of CTC aggregates versus patients with low incidence of CTC aggregates and healthy donors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5225. doi:10.1158/1538-7445.AM2011-5225

Local anesthetics inhibit kinesin motility and microtentacle protrusions in human epithelial and breast tumor cells

Detached breast tumor cells produce dynamic microtubule protrusions that promote reattachment of cells and are termed tubulin microtentacles (McTNs) due to their mechanistic distinctions from actin-based filopodia/invadopodia and tubulin-based cilia. McTNs are enriched with vimentin and detyrosinated α-tubulin, (Glu-tubulin). Evidence suggests that vimentin and Glu-tubulin are cross-linked by kinesin motor proteins. Using known kinesin inhibitors, Lidocaine and Tetracaine, the roles of kinesins in McTN formation and function were tested. Live-cell McTN counts, adhesion assays, immunofluorescence, and video microscopy were performed to visualize inhibitor effects on McTNs. Viability and apoptosis assays were used to confirm the non-toxicity of the inhibitors. Treatments of human non-tumorigenic mammary epithelial and breast tumor cells with Lidocaine or Tetracaine caused rapid collapse of vimentin filaments. Live-cell video microscopy demonstrated that Tetracaine reduces motility of intracellular GFP-kinesin and causes centripetal collapse of McTNs. Treatment with Tetracaine inhibited the extension of McTNs and their ability to promote tumor cell aggregation and reattachment. Lidocaine showed similar effects but to a lesser degree. Our current data support a model in which the inhibition of kinesin motor proteins by Tetracaine leads to the reductions in McTNs, and provides a novel mechanism for the ability of this anesthetic to decrease metastatic progression.

Epithelial-to-mesenchymal transition promotes tubulin detyrosination and microtentacles that enhance endothelial engagement

Epithelial-to-mesenchymal transition (EMT) is associated with increased breast tumor metastasis; however, the specific mechanisms by which EMT promotes metastasis remain somewhat unclear. Despite the importance of cytoskeletal dynamics during both EMT and metastasis, very few current studies examine the cytoskeleton of detached and circulating tumor cells. Specific posttranslational α-tubulin modifications are critical for adherent cell motility and implicated in numerous pathologies, but also remain understudied in detached cells. We report here that EMT induced through ectopic expression of Twist or Snail promotes α-tubulin detyrosination and the formation of tubulin-based microtentacles in detached HMLEs. Mechanistically, EMT downregulates the tubulin tyrosine ligase enzyme, resulting in an accumulation of detyrosinated α-tubulin (Glu-tubulin), and increases microtentacles that penetrate endothelial layers to facilitate tumor cell reattachment. Confocal microscopy shows that microtentacles are capable of penetrating the junctions between endothelial cells. Suppression of endogenous Twist in metastatic human breast tumor cells is capable of reducing both tubulin detyrosination and microtentacles. Clinical breast tumor samples display high concordance between Glu-tubulin and Twist expression levels, emphasizing the coupling between EMT and tubulin detyrosination in vivo. Coordinated elevation of Twist and Glu-tubulin at invasive tumor fronts, particularly within ductal carcinoma in situ samples, establishes that EMT-induced tubulin detyrosination occurs at the earliest stages of tumor invasion. These data support a novel model where the EMT that occurs during tumor invasion downregulates tubulin tyrosine ligase, increasing α-tubulin detyrosination and promoting microtentacles that could enhance the reattachment of circulating tumor cells to the vascular endothelium during metastasis.

Abstract 1464: EMT-induced tubulin detyrosination can be inhibited with parthenolide, reducing microtentacles and the lung retention of circulating breast tumor cells

Epithelial-to-mesenchymal transition (EMT) is associated with increased breast tumor metastasis, although the specific mechanism by which EMT increases metastasis remains somewhat unclear. We have previously demonstrated that detached human breast tumor cells generate unique microtentacle (McTN) extensions of their plasma membrane that are supported by coordinated vimentin intermediate filaments and detyrosinated microtubules. Microtentacles are specifically induced by EMT and promote the reattachment of tumor cells to each other and endothelial cell layers. We report here that immunohistochemical staining of tumor sections from patients with ductal carcinoma in situ and invasive ductal carcinoma indicates that detyrosination of α-tubulin occurs at invasive fronts where tumor cells are moving through the stromal microenvironment. Costaining with the EMT marker, Twist, demonstrates that tubulin detyrosination occurs specifically within cells that are undergoing EMT. Exogenous expression of either Twist or Snail in immortalized human mammary epithelial cells leads to a downregulation of the tubulin tyrosine ligase (TTL) enzyme that catalyzes the readdition of tyrosine to α-tubulin. This provides a novel molecular mechanism for the increase in detyrosinated microtubules observed in cells undergoing EMT. Addition of the sesquiterpene lactone, Parthenolide, to breast tumor cells reversed this EMT-induced increase in detyrosinated tubulin. Treatment of either breast tumor cells or nontumorigenic MCF10A mammary epithelial cells with 10μM Parthenolide also led to reductions in microtentacles, without affecting cell viability. Given the role of microtentacles in adhesion to endothelial layers, whole-animal bioluminescence imaging was used to track circulating tumor cells following tail vein injection. Pretreating metastatic MDA-MB-231 cells with Parthenolide prior to tail vein injection caused up to a 75% decrease in the lung retention of circulating tumor cells. These data support a model where the tubulin detyrosination that supports microtentacles promotes the ability of circulating tumor cells to reattach in distant capillary beds. Furthermore, the tubulin detyrosination that occurs in cells undergoing EMT at invasive tumor fronts could prime these cells for metastatic success once entering the circulation. These findings provide a possible explanation for why increased levels of detyrosinated tubulin are associated with poor patient survival in breast cancer and a new potential mechanism for how EMT could promote tumor metastasis.

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 1464.

Abstract 5133: Microtentacles and invadopodia: Functionally distinct plasma membrane protrusions of metastatic breast tumor cells separated mechanistically by c-Src

During metastasis, invading cells produce various actin-based membrane protrusions that promote directional migration and proteolysis of extracellular matrix (ECM). Our recent discovery of a filamentous actin (F-actin) component within thin tubulin-based microtentacle (McTN) protrusions in suspended MDA-MB-231 tumor cells prompted an investigation of whether these extensions are structural or functional analogs of invadopodia. We show here that MDA-MB-231s are capable of producing invadopodia and McTNs, both of which contain F-actin. Invadopodium formation was enhanced by expression of a constitutively-active c-Src kinase, and repressed by expression of dominant negative, catalytically inactive form of c-Src. In contrast expression of inactive c-Src significantly increased the McTN formation. Additionally, direct inhibition of c-Src with the SU6656 inhibitor compound significantly enhanced McTN formation, suppressed the appearance of F-actin cores and phospho-cortactin foci, and completely blocked focal degradation of extracellular matrix. These results identify McTNs and invadopodia as separate structures that provide unique and sequential contributions to metastatic progression, namely endothelial attachment and invasion, respectively.

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 5133.

Abstract 1123: PTEN loss increases efficiency of breast tumor metastasis

Breast cancer is the most frequent malignancy in women, and although many breast cancers are curable via surgery, approximately one quarter maintain a latent and insidious characteristic of slow growth with early metastasis. The loss of the tumor suppressor PTEN has been associated with breast cancer stage, lymph node status, and disease-related death, and the high rate of loss in primary tumors suggests a potential role in initiation and/or progression of the disease. However, specific cellular alterations in human breast epithelium controlled by PTEN inactivation, which lead to an increased metastatic phenotype, remain poorly defined. We have determined that heterozygous and homozygous loss of PTEN in non-tumorigenic mammary epithelial cells (MECs) was insufficient to promote anchorage-independent growth. However, MECs with PTEN loss maintained elevated activation of the PI3K/Akt and MAPK pathways and apoptotic resistance to cell rounding and matrix detatchment. We have also recently determined that PTEN expression loss leads to the production of long, dynamic, tubulin-based membrane protrusions upon detachment, which are increased in frequency, number and length per cell as compared to their isogenic, PTEN-expressing parental counterparts. These novel structures, termed microtentacles (McTNs), are structurally distinct from classical actin-based extensions of adherent cells, persist for days in breast tumor lines that are resistant to anoikis, and aid in the reattachment to matrix or cell monolayers. Therefore, the combination of apoptotic resistance and enhanced McTN formation due to PTEN loss may have important consequences for facilitating tumor cell extravasation and efficient adherence in metastatic sites.

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 1123.

Metastatic breast tumors express increased tau, which promotes microtentacle formation and the reattachment of detached breast tumor cells

The cytoskeletal organization of detached and circulating tumor cells (CTCs) is currently not well defined and may provide potential targets for new therapies to limit metastatic tumor spread. In vivo, CTCs reattach in distant tissues by a mechanism that is tubulin-dependent and suppressed by polymerized actin. The cytoskeletal mechanisms that promote reattachment of CTCs match exactly with the mechanisms supporting tubulin microtentacles (McTN), which we have recently identified in detached breast tumor cells. In this study, we aimed to investigate how McTN formation is affected by the microtubule-associated protein, tau, which is expressed in a subset of chemotherapy-resistant breast cancers. We demonstrate that endogenous tau protein localizes to McTNs and is both necessary and sufficient to promote McTN extension in detached breast tumor cells. Tau-induced McTNs increase reattachment of suspended cells and retention of CTCs in lung capillaries. Analysis of patient-matched primary and metastatic tumors reveals that 52% possess tau expression in metastases and 26% display significantly increased tau expression over disease progression. Tau enrichment in metastatic tumors and the ability of tau to promote tumor cell reattachment through McTN formation support a model in which tau-induced microtubule stabilization provides a selective advantage during tumor metastasis.

Delocalization of gamma-tubulin due to increased solubility in human breast cancer cell lines

The centrosome is the major organelle responsible for the nucleation and organization of microtubules into arrays. Recent studies demonstrate that microtubules can nucleate outside the centrosome. The molecular mechanisms controlling acentrosomal microtubule nucleation are currently poorly defined, and the function of this type of microtubule regulation in tumor cell biology is particularly unclear. Since microtubule nucleation is initiated by the gamma-tubulin protein, we examined the regulation of gamma-tubulin in a panel of human breast tumor cell lines, ranging from non-tumorigenic to highly aggressive. We have identified a more dispersive subcellular localization of gamma-tubulin in aggressive breast cancer cell lines, while gamma-tubulin localization remains largely centrosomal in non-aggressive cell lines. Delocalization of gamma-tubulin occurs independently from changes in protein expression and is therefore regulated at the post-translational level. Subcellular fractionation revealed that tumor cell lines show an aberrantly increased release of gamma-tubulin into a soluble cytoplasmic fraction, with the most dramatic changes observed in tumor cell lines of greater aggressiveness. Extraction of soluble gamma-tubulin revealed acentrosomal incorporation of gamma-tubulin in cytoplasmic microtubules and along cell junctions. Moreover, acentrosomal delocalization of gamma-tubulin yielded resistance to colchicine-mediated microtubule collapse. These findings support a model where the solubility of gamma-tubulin can be altered through post-translational modification and provides a new mechanism for microtubule dysregulation in breast cancer. Gamma-tubulin that is delocalized from the centrosome can still clearly be incorporated into filaments, and defines a novel mechanism for tumor cells to develop resistance to microtubule-targeted chemotherapies.

Targeting novel microtentacles to reduce the adhesion of circulating tumor cells to blood vessel walls

Abstract #2044

Detached human breast tumor cell lines produce novel protrusions of the plasma membrane that promote reattachment of tumor cells to each other and extracellular matrix. We have termed these protrusions “microtentacles” due to clear mechanistic distinctions from either actin-based filopodia/invadopodia or tubulin-based cilia.&#x2028; &#x2028; Compelling in vivo studies show that a mechanism consistent with microtentacles is responsible for the attachment of circulating tumor cells to blood vessel walls. Human breast tumor cell lines that display a disorganized actin cortex and hallmarks of epithelial-to-mesenchymal transition produce higher frequencies and greater extension of microtentacles. Conversely, some current and proposed tumor drugs that target the cytoskeleton actually increase microtentacles. While many cancer therapies are directed against the process of cell division, it remains important to consider the effects of these drugs on the invasive characteristics of tumor cells. Our current research has determined that microtentacles are composed of coordinated filaments of vimentin and detyrosinated tubulin. Previous studies indicate that elevated levels of vimentin and detyrosinated tubulin in tumors predict poor patient outcome, although the specific mechanisms remain unclear. Time-lapse video microscopy also indicates that the rapid extension and dynamic motion of microtentacles relies on kinesin activation. Again, our results suggest that the kinesin responsible is a conventional kinesin, rather than the mitotic kinesins commonly targeted by cancer therapies. We propose that the independent roles of vimentin, detyrosinated tubulin and kinesin in tumor metastasis could result from their interdependent contributions to microtentacle formation. Since large epithelial tumor cells are often fragmented in narrow capillaries, we are targeting microtentacles to promote the fragmentation of circulating tumor cells in the capillaries of the lung. We are currently using time-lapse confocal microscopy of tumor cells circulating in intact blood vessels and whole-animal optical imaging to define therapies that reduce microtentacle-dependent adhesion of circulating breast tumor cells during metastasis.&#x2028; &#x2028; This image shows circulating tumor cells (red) adhering to the walls of an intact blood vessel (green).

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2044.

Inhibition of metastatic outgrowth from single dormant tumor cells by targeting the cytoskeleton

Metastatic breast cancer may emerge from latent tumor cells that remain dormant at disseminated sites for many years. Identifying mechanisms regulating the switch from dormancy to proliferative metastatic growth has been elusive due to the lack of experimental models of tumor cell dormancy. We characterized the in vitro growth characteristics of cells that exhibit either dormant (D2.0R, MCF-7, and K7M2AS1.46) or proliferative (D2A1, MDA-MB-231, and K7M2) metastatic behavior in vivo. Although these cells proliferate readily in two-dimensional culture, we show that when grown in three-dimensional matrix, distinct growth properties of the cells were revealed that correlate to their dormant or proliferative behavior at metastatic sites in vivo. In three-dimensional culture, cells with dormant behavior in vivo remained cell cycle arrested with elevated nuclear expression of p16 and p27. The transition from quiescence to proliferation of D2A1 cells was dependent on fibronectin production and signaling through integrin beta1, leading to cytoskeletal reorganization with filamentous actin (F-actin) stress fiber formation. We show that phosphorylation of myosin light chain (MLC) by MLC kinase (MLCK) through integrin beta1 is required for actin stress fiber formation and proliferative growth. Inhibition of integrin beta1 or MLCK prevents transition from a quiescent to proliferative state in vitro. Inhibition of MLCK significantly reduces metastatic outgrowth in vivo. These studies show that the switch from dormancy to metastatic growth may be regulated, in part, through epigenetic signaling from the microenvironment, leading to changes in the cytoskeletal architecture of dormant cells. Targeting this process may provide therapeutic strategies for inhibition of the dormant-to-proliferative metastatic switch.

Vimentin filaments support extension of tubulin-based microtentacles in detached breast tumor cells

Solid tumor metastasis often involves detachment of epithelial carcinoma cells into the vasculature or lymphatics. However, most studies of cytoskeletal rearrangement in solid tumors focus on attached cells. In this study, we report for the first time that human breast tumor cells produce unique tubulin-based protrusions when detached from extracellular matrix. Tumor cell lines of high metastatic potential show significantly increased extension and frequency of microtubule protrusions, which we have termed tubulin microtentacles. Our previous studies in nontumorigenic mammary epithelial cells showed that such detachment-induced microtentacles are enriched in detyrosinated alpha-tubulin. However, amounts of detyrosinated tubulin were similar in breast tumor cell lines despite varying microtentacle levels. Because detyrosinated alpha-tubulin associates strongly with intermediate filament proteins, we examined the contribution of cytokeratin and vimentin filaments to tumor cell microtentacles. Increased microtentacle frequency and extension correlated strongly with loss of cytokeratin expression and up-regulation of vimentin, as is often observed during tumor progression. Moreover, vimentin filaments coaligned with microtentacles, whereas cytokeratin did not. Disruption of vimentin with PP1/PP2A-specific inhibitors significantly reduced microtentacles and inhibited cell reattachment to extracellular matrix. Furthermore, expression of a dominant-negative vimentin mutant disrupted endogenous vimentin filaments and significantly reduced microtentacles, providing specific genetic evidence that vimentin supports microtentacles. Our results define a novel model in which coordination of vimentin and detyrosinated microtubules provides structural support for the extensive microtentacles observed in detached tumor cells and a possible mechanism to promote successful metastatic spread.

Interleukin 10 and TNFalpha synergistically enhance the expression of the G protein-coupled formylpeptide receptor 2 in microglia

Microglia are important participants in inflammatory responses in the central nervous system. We previously observed that tumor necrosis factor alpha (TNFalpha) induces the expression of the formylpeptide receptor mFPR2 on microglial cells. This chemoattractant receptor mediates microglial cell chemotaxis in response to a variety of peptides, including amyloid beta peptide (Abeta(42)), a major pathogenic factor in Alzheimer's disease (AD). In search for agents that regulate microglial activation, we unexpectedly found that IL-10 enhanced the expression of mFPR2 on TNFalpha-activated microglia. This was associated with a markedly increased microglial chemotaxis to Abeta(42) and its endocytosis via mFPR2. Mechanistic studies revealed that the synergistic effect of IL-10 on TNFalpha-induction of mFPR2 in microglia was dependent on activation of p38 MAPK. Our results suggest that IL-10 may affect the pathogenic process of AD by up-regulating mFPR2 and thus favoring the recognition and internalization of Abeta(42) by activated microglial cells.

Induction of the formyl peptide receptor 2 in microglia by IFN-gamma and synergy with CD40 ligand

Human formyl peptide receptor (FPR)-like 1 (FPRL1) and its mouse homologue mFPR2 are functional receptors for a variety of exogenous and host-derived chemotactic peptides, including amyloid beta 1-42 (Abeta(42)), a pathogenic factor in Alzheimer's disease. Because mFPR2 in microglial cells is regulated by proinflammatory stimulants including TLR agonists, in this study we investigated the capacity of IFN-gamma and the CD40 ligand (CD40L) to affect the expression and function of mFPR2. We found that IFN-gamma, when used alone, induced mFPR2 mRNA expression in a mouse microglial cell line and primary microglial cells in association with increased cell migration in response to mFPR2 agonists, including Abeta(42). IFN-gamma also increased the endocytosis of Abeta(42) by microglial cells via mFPR2. The effect of IFN-gamma on mFPR2 expression in microglial cells was dependent on activation of MAPK and IkappaB-alpha. IFN-gamma additionally increased the expression of CD40 by microglial cells and soluble CD40L significantly promoted cell responses to IFN-gamma during a 6-h incubation period by enhancing the activation of MAPK and IkappaB-alpha signaling pathways. We additionally found that the effect of IFN-gamma and its synergy with CD40L on mFPR2 expression in microglia was mediated in part by TNF-alpha. Our results suggest that IFN-gamma and CD40L, two host-derived factors with increased concentrations in inflammatory central nervous system diseases, may profoundly affect microglial cell responses in the pathogenic process in which mFPR2 agonist peptides are elevated.

Sphingomyelinase restricts the lateral diffusion of CD4 and inhibits human immunodeficiency virus fusion

Previously, we reported that treatment of cells with sphingomyelinase inhibits human immunodeficiency virus type 1 (HIV-1) entry. Here, we determined by measuring fluorescence recovery after photobleaching that the lateral diffusion of CD4 decreased 4-fold following sphingomyelinase treatment, while the effective diffusion rate of CCR5 remained unchanged. Notably, sphingomyelinase treatment of cells did not influence gp120 binding, HIV-1 attachment, or fluid-phase and receptor-mediated endocytosis. Furthermore, sphingomyelinase treatment did not affect the membrane disposition of the HIV receptor proteins CD4, CXCR4, and CCR5, as determined by Triton X-100 extraction. Restriction of CD4 diffusion by antibody cross-linking also inhibited HIV infection. We therefore interpret the decrease in CD4 lateral mobility following sphingomyelinase treatment in terms of clustering of CD4 molecules. Examination of fusion intermediates indicated that sphingomyelinase treatment inhibited HIV at a step in the fusion process after CD4 engagement. Maximal inhibition of fusion was observed following short coculture times and with target cells that express low levels of CD4. As HIV entry into cells requires the sequential engagement of viral envelope protein with CD4 and coreceptor, we propose that sphingomyelinase inhibits HIV infection by inducing CD4 clustering that prevents coreceptor engagement and HIV fusion.

Calibration and standardization of the emission light path of confocal microscopes

Recently, there has been a large expansion in the usage of optical microscopes for obtaining quantitative information from biological samples in order to determine fundamental biological information such as molecular kinetics and interaction, and heterogeneity within cell populations. Consequently, we built a highly stable, uniform, isotropically emitting and convenient-to-use light source, and designed image analysis procedures for calibrating the emission light path of optical microscopes. We used the source and procedures to analyse the quantitative imaging properties of a widely used model of laser scanning confocal microscope. Results showed that the overall performance was as high as could be expected given the inherent limitations of the optical components and photomultiplier tubes. We observed that the photon detection efficiency did not vary with photomultiplier tube gain and that the highest dynamic range was achieved with relatively low gain and 12-bit digitization. Practical applications of the light source for checking the transmission of optical components in the emission light path are presented.

Activation of Toll-like Receptor 2 on Microglia Promotes Cell Uptake of Alzheimer Disease-associated Amyloid β Peptide

The human G-protein-coupled formyl peptide receptor-like 1 (FPRL1) and its mouse homologue mFPR2 mediate the chemotactic activity of a variety of polypeptides associated with inflammation and bacterial infection, including the 42-amino acid form of amyloid beta peptide (Abeta42), a pathogenic factor in Alzheimer disease. Because mFPR2 was inducible in mouse microglial cells by proinflammatory stimulants, such as bacterial lipopolysaccharide, a ligand for the Toll-like receptor 4 (TLR4), we investigated the role of TLR2 in the regulation of mFPR2. We found that a TLR2 agonist, peptidoglycan (PGN) derived from Gram-positive bacterium Staphylococcus aureus, induced considerable mFpr2 mRNA expression in a mouse microglial cell line and primary microglial cells. This was associated with a markedly increased chemotaxis of the cells in response to mFPR2 agonist peptides. In addition, activation of TLR2 markedly enhanced mFPR2-mediated uptake of Abeta42 by microglia. Studies of the mechanistic basis showed that PGN activates MAPK and IkappaBalpha, and the effect of PGN on induction of mFPR2 was dependent on signaling pathways via ERK1/2 and p38 MAPKs. The use of TLR2 on microglial cells by PGN was supported by the fact that N9 cells transfected with short interfering RNA targeting mouse TLR2 failed to show increased expression of functional mFPR2 after stimulation with PGN. Our results demonstrated a potentially important role for TLR2 in microglial cells of promoting cell responses to chemoattractants produced in lesions of inflammatory and neurodegenerative diseases in the brain.

CpG-containing oligodeoxynucleotide promotes microglial cell uptake of amyloid beta 1-42 peptide by up-regulating the expression of the G-protein- coupled receptor mFPR2

Human G protein-coupled formyl peptide receptor like 1 (FPRL1) and its mouse homologue murine formyl peptide receptor 2 (mFPR2) mediate the chemotactic activity of amyloid beta 1-42 (Abeta42), a key pathogenic peptide in Alzheimer's disease (AD). Since mFPR2 is up-regulated in mouse microglia by lipopolysaccharide (LPS), a Toll-like receptor 4 ligand, we investigated the capacity of CpG-containing oligodeoxynucleotide (ODN), a Toll-like receptor (TLR) 9 ligand, to regulate the expression of mFPR2 in mouse microglia. CpG ODN markedly enhanced the expression and function of mFPR2 in microglial cells, which exhibited increased chemotactic responses to mFPR2 agonists, including Abeta42. The effect of CpG ODN is dependent on activation of p38 MAPK. Further studies showed that CpG ODN-treated microglia increased their capacity to endocytose Abeta42 through mFPR2, as this process was abrogated by pertussis toxin, a Gi protein inhibitor, and W peptide, another potent mFPR2 agonist. Our results suggest that TLR9 may play an important role in promoting microglial recognition of Abeta42, thus affecting the pathogenic process of AD.

In Vivo HIV-1 Rev Multimerization in the Nucleolus and Cytoplasm Identified by Fluorescence Resonance Energy Transfer

Nuclear export of intron-containing human immunodeficiency virus type 1 RNA is mediated by the viral Rev protein. Rev is a nucleocytoplasmic transport protein that directly binds to its cis-acting Rev-responsive element RNA. Rev function depends on its ability to multimerize. The in vivo dynamics and the subcellular dependence of this process are still largely unexplored. To visualize and quantitatively analyze the mechanism of Rev multimeric assembly in live cells, we used high resolution in vivo fluorescence resonance energy transfer (FRET) and fluorescence recovery after photobleaching. By using two different dynamic FRET approaches (acceptor photobleaching and donor bleaching time measurements), we observed a strong Rev-Rev interaction in the nucleoli of living cells. Most interestingly, we could also detect Rev multimerization in the cytoplasm; however, FRET efficiency in the cytoplasm was significantly lower than in the nucleolus. By using fluorescence recovery after photobleaching, we investigated the mobility of Rev within the nucleolus. Mathematical modeling of the fluorescence recovery after photobleaching recoveries enabled us to extract relative association and dissociation constants and the diffusion coefficient of Rev in the nucleolus. Our results show that Rev multimerizes in the nucleolus of living cells, suggesting an important role of the nucleolus in nucleocytoplasmic transport.

Identification of probabilistic transcriptional switches in the Ly49 gene cluster: a eukaryotic mechanism for selective gene activation

Murine natural killer cells selectively express members of the Ly49 family of class I MHC receptors; however, the molecular mechanism controlling probabilistic expression of Ly49 proteins has not been defined. A pair of overlapping, divergent promoters discovered in the Ly49g gene functions as a molecular switch that can produce a forward transcript containing the coding region of the gene (on position) or a noncoding transcript in the opposite direction (off position), and this element maintains transcription in the chosen direction. Competition of C/EBP and TBP transcription factors for overlapping binding sites determines the relative strength of the competing promoters and the probability of transcription in a given direction. Similar elements precede all Ly49 family members, and the relative strength of the forward promoter in each inhibitory Ly49 gene correlates with the percentage of natural killer cells that express a given receptor, supporting a promoter competition model of selective gene activation.

Identification of neutrophil granule protein cathepsin G as a novel chemotactic agonist for the G protein-coupled formyl peptide receptor

The antimicrobial and proinflammatory neutrophil granule protein cathepsin G (CaG) has been reported as a chemoattractant for human phagocytic leukocytes by using a putative G protein coupled receptor. In an effort to identify potential CaG receptor(s), we found that CaG-induced phagocyte migration was specifically attenuated by the bacterial chemotactic peptide fMLP, suggesting these two chemoattractants might share a receptor. In fact, CaG chemoattracts rat basophilic leukemia cells (RBL cells) expressing the high affinity human fMLP receptor FPR, but not parental RBL cells or cells transfected with other chemoattractant receptors. In addition, a specific FPR Ab and a defined FPR antagonist, cyclosporin H, abolished the chemotactic response of phagocytes and FPR-transfected cells to CaG. Furthermore, CaG down-regulated the cell surface expression of FPR in association with receptor internalization. Unlike fMLP, CaG did not induce potent Ca(2+) flux and was a relatively weaker activator of MAPKs through FPR. Yet CaG activated an atypical protein kinase C isozyme, protein kinase Czeta, which was essential for FPR to mediate the chemotactic activity of CaG. Thus, our studies identify CaG as a novel, host-derived chemotactic agonist for FPR and expand the functional scope of this receptor in inflammatory and immune responses.

A TREM family member, TLT-1, is found exclusively in the α-granules of megakaryocytes and platelets

The triggering receptors expressed on myeloid cells (TREMs) have drawn considerable attention due to their ability to activate multiple cell types within the innate immune system, including neutrophils, monocyte/macrophages, and dendritic cells, via their association with DAP12. TLT-1 (TREM-like transcript-1) lies within the TREM gene cluster and contains the characteristic single V-set immunoglobulin (Ig) domain of the family, but its longer cytoplasmic tail is composed of both a proline-rich region and an immune receptor tyrosine-based inhibitory motif, the latter known to be used for interactions with protein tyrosine phosphatases. Here we report that TLT-1 is expressed exclusively in platelets and megakaryocytes (MKs) and that TLT-1 expression is up-regulated dramatically upon platelet activation. Consistent with this observation, confocal microscopy demonstrates that TLT-1 is prepackaged, along with CD62P, into both MK and platelet α-granules. Differences in thrombin-induced redistribution of CD62P and TLT-1 indicate that TLT-1 is not simply cargo of α-granules but may instead regulate granule construction or dispersal. Together these data show that that TLT-1 does not function to inhibit members of the TREM family but instead may play a role in maintaining vascular hemostasis and regulating coagulation and inflammation at sites of injury.

Automatic and quantitative measurement of protein-protein colocalization in live cells

We introduce a novel statistical approach that quantifies, for the first time, the amount of colocalization of two fluorescent-labeled proteins in an image automatically, removing the bias of visual interpretation. This is done by estimating simultaneously the maximum threshold of intensity for each color below which pixels do not show any statistical correlation. The sensitivity of the method was illustrated on simulated data by statistically confirming the existence of true colocalization in images with as little as 3% colocalization. This method was then tested on a large three-dimensional set of fixed cells cotransfected with CFP/YFP pairs of proteins that either co-compartmentalized, interacted, or were just randomly localized in the nucleolus. In this test, the algorithm successfully distinguished random color overlap from colocalization due to either co-compartmentalization or interaction, and results were verified by fluorescence resonance energy transfer. The accuracy and consistency of our algorithm was further illustrated by measuring, for the first time in live cells, the dissociation rate (k(d)) of the HIV-1 Rev/CRM1 export complex induced by the cytotoxin leptomycin B. Rev/CRM1 colocalization in nucleoli dropped exponentially after addition of leptomycin B at a rate of 1.25 x 10(-3) s(-1). More generally, this algorithm can be used to answer a variety of biological questions involving protein-protein interactions or co-compartmentalization and can be generalized to colocalization of more than two colors.

Effects of ADP on different inhibitory properties of brain glutamate dehydrogenase isoproteins by perphenazine

Incubation of glutamate dehydrogenase isoproteins (GDH I and GDH II) from bovine brains with perphenazine resulted in a time-dependent loss of enzyme activity. 2-Oxoglutarate and NADH, separately or together, gave partial but not complete protection against the inhibition. Although there were no detectable differences between GDH I and GDH II in inhibition by perphenazine in the absence of ADP, the sensitivities to the inhibition by the drug were significantly distinct for the two isoproteins in the presence of ADP. Low concentrations of ADP (0.05-0.20 mM) did not interfere with the inhibition of GDH I and GDH II by perphenazine. However, in the presence of high concentrations of ADP (0.5-1.0 mM), inhibitory effects of perphenazine on GDH isoproteins were significantly diminished as determined by enzyme kinetics and quantitative affinity chromatography on perphenazine-Sepharose. GDH I was more sensitively reacted with ADP than GDH II on the inhibition by perphenazine. Since physiological ADP levels can vary from 0.05 to > 1.0 mM depending on the rate of oxidative phosphorylation, our results suggest a possibility that two types of GDHs are differently regulated by the antipsychotic actions of perphenazine depending on the physiological concentrations of ADP. GTP and L-leucine, other well-known allosteric regulators, did not affect the inhibitory actions of perphenazine on bovine brain GDH isoproteins.

An essential histidine residue in GTP binding domain of bovine brain glutamate dehydrogenase isoproteins

Greater than 90% of the original activity of the enzymes remained after modification of histidine residues of glutamate dehydrogenase (GDH) isoproteins from bovine brains with diethyl pyrocarbonate (DEPC). This suggests that the DEPC modified histidine residues are not critically involved in the catalysis of the GDH isoproteins. The influence of DEPC modified histidine residue(s) on binding of GTP to GDH isoproteins was investigated by protection studies. These studies showed that inhibition of GDH isoproteins by GTP was protected by preincubation of GDH isoproteins with DEPC. The amount of protection was dependent on the concentration of DEPC. The GTP inhibition was fully protected by preincubation of GDH isoproteins with DEPC at saturating concentrations. These results indicate that the histidine residues may play an important role in the GTP binding on GDH isoproteins. Spectrophotometric studies showed that three histidine residues per enzyme subunit were able to react with DEPC in the absence of GTP, whereas two histidine residues per enzyme subunit interacted with DEPC when the enzymes were preincubated with GTP. These results indicate that one of the histidine residues is involved in the GTP binding domain of GDH isoproteins. The quantitative affinity chromatographic studies showed that the influence of GTP on the binding of GDH isoproteins to DEPC-Sepharose was significantly distinct for the two GDH isoproteins. GDH I was more sensitively affected by GTP than GDH II in the binding affinity for DEPC-Sepharose. ADP, another well-known allosteric regulator, showed no significant changes in the interaction of DEPC with GDH isoproteins.

A case of nodular scleritis in association with Behcet's disease

Approximately 50% of patients with scleritis are known to be associated with systemic connective tissue diseases or vasculitic diseases such as rheumatoid arthritis (RA), Wegener's granulomatosis, relapsing polychondritis, and systemic lupus erythematosus. The patients with scleritis in association with Behcet's disease (BD) have been rarely described in the literature. We report a 46-year-old female patient with BD who developed the nodular scleritis.

SJ-3366, a unique and highly potent nonnucleoside reverse transcriptase inhibitor of human immunodeficiency virus type 1 (HIV-1) that also inhibits HIV-2

We have identified and characterized a potent new nonnucleoside reverse transcriptase (RT) inhibitor (NNRTI) of human immunodeficiency virus type 1 (HIV-1) that also is active against HIV-2 and which interferes with virus replication by two distinct mechanisms. 1-(3-Cyclopenten-1-yl)methyl-6-(3,5-dimethylbenzoyl)-5-ethyl-2,4-pyrimidinedione (SJ-3366) inhibits HIV-1 replication at concentrations of approximately 1 nM, with a therapeutic index of greater than 4 x 10(6). The efficacy and toxicity of SJ-3366 are consistent when evaluated with established or fresh human cells, and the compound is equipotent against all strains of HIV-1 evaluated, including syncytium-inducing, non-syncytium-inducing, monocyte/macrophage-tropic, and subtype virus strains. Distinct from other members of the pharmacologic class of NNRTIs, SJ-3366 inhibited laboratory and clinical strains of HIV-2 at a concentration of approximately 150 nM, yielding a therapeutic index of approximately 20,000. Like most NNRTIs, the compound was less active when challenged with HIV-1 strains possessing the Y181C, K103N, and Y188C amino acid changes in the RT and selected for a virus with a Y181C amino acid change in the RT after five tissue culture passages in the presence of the compound. In combination anti-HIV assays with nucleoside and nonnucleoside RT and protease inhibitors, additive interactions occurred with all compounds tested with the exception of dideoxyinosine, with which a synergistic interaction was found. Biochemically, SJ-3366 exhibited a K(i) value of 3.2 nM, with a mixed mechanism of inhibition against HIV-1 RT, but it did not inhibit HIV-2 RT. SJ-3366 also inhibited the entry of both HIV-1 and HIV-2 into target cells. On the basis of its therapeutic index and multiple mechanisms of anti-HIV action, SJ-3366 represents an exciting new compound for use in HIV-infected individuals.

Characterization of bacteriophage lambda excisionase mutants defective in DNA binding

The bacteriophage lambda excisionase (Xis) is a sequence-specific DNA binding protein required for excisive recombination. Xis binds cooperatively to two DNA sites arranged as direct repeats on the phage DNA. Efficient excision is achieved through a cooperative interaction between Xis and the host-encoded factor for inversion stimulation as well as a cooperative interaction between Xis and integrase. The secondary structure of the Xis protein was predicted to contain a typical amphipathic helix that spans residues 18 to 28. Several mutants, defective in promoting excision in vivo, were isolated with mutations at positions encoding polar amino acids in the putative helix (T. E. Numrych, R. I. Gumport, and J. F. Gardner, EMBO J. 11:3797-3806, 1992). We substituted alanines for the polar amino acids in this region. Mutant proteins with substitutions for polar amino acids in the amino-terminal region of the putative helix exhibited decreased excision in vivo and were defective in DNA binding. In addition, an alanine substitution at glutamic acid 40 also resulted in altered DNA binding. This indicates that the hydrophilic face of the alpha-helix and the region containing glutamic acid 40 may form the DNA binding surfaces of the Xis protein.

Detection of cryptic Y chromosome mosaicism by coamplification PCR with archived cytogenetic slides of suspected Turner syndrome

Turner syndrome is one of the most common cytogenetic abnormalities. It is known that the Y chromosome or Y derived material is present in 6-9% of TS patient and it may develop a high risk of gonadoblastoma in 15-25%. So it is crucial to carry out cyto genetic analysis and Y-specific probe studies for all persons with gonadal dysgenesis to rule out mosaicism with Y-bearing cell line; eg 45,X/46,XY. In this study, 26 archival slides previously analyzed cytogenetically as 45,X, 45,X/46,X,i(X), 45,X/46,X,r(X), and 45,X/46,XX were examined. Coamplification PCR, having the advantage of providing rapid result and confirming PCR failure, was performed with the slide samples in the regions of dystrophin gene in Xp21and DYZ3 in the Y centromeric region. All of archived slides were positive for X-specific gene and one slide of 45,X was found to have the cryptic Y chromosome material. Our result suggests that the archived cytogenetic slides could be applied for the detection of Y chromosome rapidly and efficiently in TS patients.

A case of coexisting Behçet's disease and ankylosing spondylitis

Behçet's disease (BD) is a chronic inflammatory condition involving several organs, such as skin, mucous membrane, eye, joint, intestine, lung and central nervous system. Ankylosing spondylitis (AS) is a prototype of seronegative spondyloarthropathy, and a chronic systemic inflammatory disorder of the axial skeleton, mainly affecting the sacroiliac joint and spine. In the latter, systemic complications may develop in addition to joint involvement. The coexistence of BD and AS has been rarely reported in the literature. The inclusion of BD among seronegative spondyloarthritides and whether sacroiliitis (SI) develops in BD are still being debated. We describe a 28-year-old man who has fulfilled the diagnostic criteria for BD and AS as well.

Site-specific recombination of bacteriophage P22 does not require integration host factor

Site-specific recombination by phages lambda and P22 is carried out by multiprotein-DNA complexes. Integration host factor (IHF) facilitates lambda site-specific recombination by inducing DNA bends necessary to form an active recombinogenic complex. Mutants lacking IHF are over 1,000-fold less proficient in supporting lambda site-specific recombination than wild-type cells. Although the attP region of P22 contains strong IHF binding sites, in vivo measurements of integration and excision frequencies showed that infecting P22 phages can perform site-specific recombination to its maximum efficiency in the absence of IHF. In addition, a plasmid integration assay showed that integrative recombination occurs equally well in wild-type and ihfA mutant cells. P22 integrative recombination is also efficient in Escherichia coli in the absence of functional IHF. These results suggest that nucleoprotein structures proficient for recombination can form in the absence of IHF or that another factor(s) can substitute for IHF in the formation of complexes.

An unusual type of cancer-associated retinopathy in a patient with ovarian cancer

We studied a case of unusual retinopathy in a 35-year-old woman who presented with bilateral visual deterioration due to retinal pigmentary mottling and serous elevation in the posterior pole. Two years before, she had undergone hysterectomy and bilateral salphingo-oophorectomy for ovarian cancer. Her electroretinogram became subnormal, and her fluorescein angiogram exhibited multiple deep retinal pigment epithelial leakages and subretinal dye pooling in both eyes. Corticosteroid therapy failed to prevent visual loss. She was found to possess antibodies against retinal 45 kd protein. This led to a diagnosis of cancer-associated retinopathy with atypical protein profile. We report a rare variety of cancer-associated retinopathy in a patient with-ovarian cancer.

Reactive cysteine residue of bovine brain glutamate dehydrogenase isoproteins

Protein chemical studies of glutamate dehydrogenase isoproteins (GDH I and GDH II) from bovine brain reveal that one cystein residue is accessible for reaction with thiol-modifying reagent. Reaction of the two types of GDH isoproteins with p-chloromercuribenzoic acid resulted in a time-dependent loss of enzyme activity. The inactivation followed pseudo first-order kinetics with the second-order rate constant of 83 M(-1) s(-1) and 75 M(-1) s(-1) for GDH I and GDH II, respectively. The inactivation was partially prevented by preincubation of the glutamate dehydrogenase isoproteins with NADH. A combination of 10 mM 2-oxoglutarate with 2 mM NADH gave complete protection against the inactivation. There were no significant differences between the two glutamate dehydrogenase isoproteins in their sensitivities to inactivation by p-chloromercuribenzoic indicating that the microenvironmental structures of the GDH isoproteins are very similar to each other. Allosteric effectors such as ADP and GTP had no effects on the inactivation of glutamate dehydrogenase isoproteins by thiol-modifying reagents. By a combination of peptide mapping analysis and labeling with [14C] p-chloromercuribenzoic acid, a reactive cystein residue was identified as Cys323 in the overall sequence. The cysteine residue was clearly identical to sequences of other GDH species known.

In vivo assay of protein-protein interactions in Hin-mediated DNA inversion

In order to form the catalytic nucleoprotein complex called the invertasome in the Hin-mediated DNA inversion reaction, interactions of the DNA-binding proteins Hin and Fis are required. Assays for these protein-protein interactions have been exploited with protein cross-linkers in vitro. In this study, an in vivo assay system that probes protein-protein interactions was developed. The formation of a DNA loop generated by protein interactions resulted in transcriptional repression of an artificially designed operon, which in turn increased the chance of survival of Escherichia coli host cells in a streptomycin-containing medium. Using this system, we were able to assay the Hin-Hin interaction that results in the pairing of the two recombination sites and protein interactions that result in the formation of the invertasome. This assay system also led us to find that an individual Hin dimer bound on a recombination site can form a stable complex with Fis bound on the recombinational enhancer; this finding has never been observed in in vitro studies. Possible pathways toward the formation of the invertasome are discussed based on the assay results for a previously reported Hin mutant.

Activation of two types of brain glutamate dehydrogenase isoproteins by gabapentin

The stimulatory effects of gabapentin on the activities of two types of glutamate dehydrogenase (GDH) isoproteins homogeneously purified from bovine brain have been studied at various conditions. When the effects of different gabapentin concentrations on GDH activities were studied in the direction of reductive amination of 2-oxoglutarate with NADPH as a coenzyme, a marked activation was observed for both isoproteins, whereas both isoproteins showed activation to a lesser extent with NADH as a coenzyme. Stimulatory effects of gabapentin on GDH activities in the direction of the oxidative deamination of glutamate were also observed, but to a much lesser extent than reductive amination. There were big differences between the two GDH isoproteins in their sensitivity to the action of gabapentin. The largest activation was observed with GDH II when NADPH was used as a coenzyme. Half-maximal stimulation was reached at around 1.5 mM. Gabapentin relieved the inhibition of GDH isoproteins by GTP and this resulted in an increase in the apparent activation by gabapentin in the presence of GTP. 2-Oxoglutarate was found to give rise to high substrate inhibition and gabapentin reduced the substrate inhibition in the presence of 0.2 mM NADH. Since there are neurodegenerative disorders in which GDH activity is decreased, the therapeutic modulation of the activity of this enzyme may be clinically useful.

Cloning and nucleotide sequence of the DNA gyrase gyrA gene from Serratia marcescens and characterization of mutations in gyrA of quinolone-resistant clinical isolates

The sequence of the DNA gyrase gyrA gene of Serratia marcescens ATCC 14756 was determined. An open reading frame of 2,640 nucleotides coding for a polypeptide with a calculated molecular mass of 97,460 was found, and its sequence complemented the sequence of an Escherichia coli gyrA temperature-sensitive mutation. Analysis of the PCR products of the quinolone resistance-determining regions of gyrA genes from six quinolone-resistant clinical isolates revealed a single amino acid substitution, Ser-83 to Arg or Asp-87 to Tyr, in all six mutants, suggesting that a mutational alteration in gyrA is a common mechanism of quinolone resistance in S. marcescens.

Ginsenosides activate DNA polymerase delta from bovine placenta

The activation of a DNA polymerase delta (pol delta) purified from bovine placenta by ginsenosides from Panax Ginseng C. A. Meyer has been studied. Preincubation of the enzyme with ginsenosides increased the polymerase activity 2.2-fold in a dose-dependent manner. There was a reproducible decrease in Km, in addition to a substantial increase in Vmax, in response to increasing concentrations of ginsenosides. Ginsenosides also activated the proofreading ability of 3'- to 5'-exonuclease activity associated with DNA pol delta. The coordinated activation of both polymerase and exonuclease activities of DNA pol delta by ginsenosides is consistent with the view that its polymerase and its exonuclease activities residue on the same protein molecule. UV/Vis difference spectroscopic studies suggested that the activation of DNA pol delta by ginsenosides might be due to the conformational change induced by ginsenosides binding.