The Caenorhabditis elegans anchor cell transcriptome: ribosome biogenesis drives cell invasion through basement membrane

Cell invasion through basement membrane (BM) barriers is important in development, immune function and cancer progression. As invasion through BM is often stochastic, capturing gene expression profiles of actively invading cells in vivo remains elusive. Using the stereotyped timing of Caenorhabditis elegans anchor cell (AC) invasion, we generated an AC transcriptome during BM breaching. Through a focused RNAi screen of transcriptionally enriched genes, we identified new invasion regulators, including translationally controlled tumor protein (TCTP). We also discovered gene enrichment of ribosomal proteins. AC-specific RNAi, endogenous ribosome labeling and ribosome biogenesis analysis revealed that a burst of ribosome production occurs shortly after AC specification, which drives the translation of proteins mediating BM removal. Ribosomes also enrich near the AC endoplasmic reticulum (ER) Sec61 translocon and the endomembrane system expands before invasion. We show that AC invasion is sensitive to ER stress, indicating a heightened requirement for translation of ER-trafficked proteins. These studies reveal key roles for ribosome biogenesis and endomembrane expansion in cell invasion through BM and establish the AC transcriptome as a resource to identify mechanisms underlying BM transmigration.

Localized glucose import, glycolytic processing, and mitochondria generate a focused ATP burst to power basement-membrane invasion

Invasive cells use transient, energy-consuming protrusions to breach basement membrane (BM) barriers. Using the ATP sensor PercevalHR during anchor cell (AC) invasion in Caenorhabditis elegans, we show that BM invasion is accompanied by an ATP burst from mitochondria at the invasive front. RNAi screening and visualization of a glucose biosensor identified two glucose transporters, FGT-1 and FGT-2, which bathe invasive front mitochondria with glucose and facilitate the ATP burst to form protrusions. FGT-1 localizes at high levels along the invasive membrane, while FGT-2 is adaptive, enriching most strongly during BM breaching and when FGT-1 is absent. Cytosolic glycolytic enzymes that process glucose for mitochondrial ATP production cluster with invasive front mitochondria and promote higher mitochondrial membrane potential and ATP levels. Finally, we show that UNC-6 (netrin), which polarizes invasive protrusions, also orients FGT-1. These studies reveal a robust and integrated energy acquisition, processing, and delivery network that powers BM breaching.

Comprehensive Endogenous Tagging of Basement Membrane Components Reveals Dynamic Movement within the Matrix Scaffolding

Basement membranes (BMs) are supramolecular matrices built on laminin and type IV collagen networks that provide structural and signaling support to tissues. BM complexity, however, has hindered an understanding of its formation, dynamics, and regulation. Using genome editing, we tagged 29 BM matrix components and receptors in C. elegans with mNeonGreen. Here, we report a common template that initiates BM formation, which rapidly diversifies during tissue differentiation. Through photobleaching studies, we show that BMs are not static-surprisingly, many matrix proteins move within the laminin and collagen scaffoldings. Finally, quantitative imaging, conditional knockdown, and optical highlighting indicate that papilin, a poorly studied glycoprotein, is the most abundant component in the gonadal BM, where it facilitates type IV collagen removal during BM expansion and tissue growth. Together, this work introduces methods for holistic investigation of BM regulation and reveals that BMs are highly dynamic and capable of rapid change to support tissues.

α-Integrins dictate distinct modes of type IV collagen recruitment to basement membranes

Basement membranes (BMs) are cell-associated extracellular matrices that support tissue integrity, signaling, and barrier properties. Type IV collagen is critical for BM function, yet how it is directed into BMs in vivo is unclear. Through live-cell imaging of endogenous localization, conditional knockdown, and misexpression experiments, we uncovered distinct mechanisms of integrin-mediated collagen recruitment to Caenorhabditis elegans postembryonic gonadal and pharyngeal BMs. The putative laminin-binding αINA-1/βPAT-3 integrin was selectively activated in the gonad and recruited laminin, which directed moderate collagen incorporation. In contrast, the putative Arg-Gly-Asp (RGD)-binding αPAT-2/βPAT-3 integrin was activated in the pharynx and recruited high levels of collagen in an apparently laminin-independent manner. Through an RNAi screen, we further identified the small GTPase RAP-3 (Rap1) as a pharyngeal-specific PAT-2/PAT-3 activator that modulates collagen levels. Together, these studies demonstrate that tissues can use distinct mechanisms to direct collagen incorporation into BMs to precisely control collagen levels and construct diverse BMs.

Adaptive F-Actin Polymerization and Localized ATP Production Drive Basement Membrane Invasion in the Absence of MMPs

Matrix metalloproteinases (MMPs) are associated with decreased patient prognosis but have failed as anti-invasive drug targets despite promoting cancer cell invasion. Through time-lapse imaging, optical highlighting, and combined genetic removal of the five MMPs expressed during anchor cell (AC) invasion in C. elegans, we find that MMPs hasten invasion by degrading basement membrane (BM). Though irregular and delayed, AC invasion persists in MMP- animals via adaptive enrichment of the Arp2/3 complex at the invasive cell membrane, which drives formation of an F-actin-rich protrusion that physically breaches and displaces BM. Using a large-scale RNAi synergistic screen and a genetically encoded ATP FRET sensor, we discover that mitochondria enrich within the protrusion and provide localized ATP that fuels F-actin network growth. Thus, without MMPs, an invasive cell can alter its BM-breaching tactics, suggesting that targeting adaptive mechanisms will be necessary to mitigate BM invasion in human pathologies.

Forces drive basement membrane invasion in Caenorhabditis elegans

During invasion, cells breach basement membrane (BM) barriers with actin-rich protrusions. It remains unclear, however, whether actin polymerization applies pushing forces to help break through BM, or whether actin filaments play a passive role as scaffolding for targeting invasive machinery. Here, using the developmental event of anchor cell (AC) invasion in Caenorhabditis elegans, we observe that the AC deforms the BM and underlying tissue just before invasion, exerting forces in the tens of nanonewtons range. Deformation is driven by actin polymerization nucleated by the Arp2/3 complex and its activators, whereas formins and cross-linkers are dispensable. Delays in invasion upon actin regulator loss are not caused by defects in AC polarity, trafficking, or secretion, as appropriate markers are correctly localized in the AC even when actin is reduced and invasion is disrupted. Overall force production emerges from this study as one of the main tools that invading cells use to promote BM disruption in C. elegans.

Cell Invasion In Vivo via Rapid Exocytosis of a Transient Lysosome-Derived Membrane Domain

Invasive cells use small invadopodia to breach basement membrane (BM), a dense matrix that encases tissues. Following the breach, a large protrusion forms to clear a path for tissue entry by poorly understood mechanisms. Using RNAi screening for defects in Caenorhabditis elegans anchor cell (AC) invasion, we found that UNC-6(netrin)/UNC-40(DCC) signaling at the BM breach site directs exocytosis of lysosomes using the exocyst and SNARE SNAP-29 to form a large protrusion that invades vulval tissue. Live-cell imaging revealed that the protrusion is enriched in the matrix metalloprotease ZMP-1 and transiently expands AC volume by more than 20%, displacing surrounding BM and vulval epithelium. Photobleaching and genetic perturbations showed that the BM receptor dystroglycan forms a membrane diffusion barrier at the neck of the protrusion, which enables protrusion growth. Together these studies define a netrin-dependent pathway that builds an invasive protrusion, an isolated lysosome-derived membrane structure specialized to breach tissue barriers.

Dual Targeting of Mesenchymal and Amoeboid Motility Hinders Metastatic Behavior

Commonly upregulated in human cancers, the scaffolding protein NEDD9/HEF1 is a known regulator of mesenchymal migration and cancer cell plasticity. However, the functional role of NEDD9 as a regulator of different migration/invasion modes in the context of breast cancer metastasis is currently unknown. Here, it is reported that NEDD9 is necessary for both mesenchymal and amoeboid individual cell migration/invasion in triple-negative breast cancer (TNBC). NEDD9 deficiency results in acquisition of the amoeboid morphology, but severely limits all types of cell motility. Mechanistically, NEDD9 promotes mesenchymal migration via VAV2-dependent Rac1 activation, and depletion of VAV2 impairs the ability of NEDD9 to activate Rac1. In addition, NEDD9 supports a mesenchymal phenotype through stimulating polymerization of actin via promoting CTTN phosphorylation in an AURKA-dependent manner. Interestingly, an increase in RhoA activity in NEDD9-depleted cells does not facilitate a switch to functional amoeboid motility, indicating a role of NEDD9 in the regulation of downstream RhoA signaling effectors. Simultaneous depletion of NEDD9 or inhibition of AURKA in combination with inhibition of the amoeboid driver ROCK results in an additional decrease in cancer cell migration/invasion. Finally, we confirmed that a dual targeting strategy is a viable and efficient therapeutic approach to hinder the metastasis of breast cancer in xenograft models, showcasing the important need for further clinical evaluation of this regimen to impede the spread of disease and improve patient survival.Implications: This study provides new insight into the therapeutic benefit of combining NEDD9 depletion with ROCK inhibition to reduce tumor cell dissemination and discovers a new regulatory role of NEDD9 in the modulation of VAV2-dependent activation of Rac1 and actin polymerization. Mol Cancer Res; 15(6); 670-82. ©2017 AACR.

Invasive Cell Fate Requires G1 Cell-Cycle Arrest and Histone Deacetylase-Mediated Changes in Gene Expression

Despite critical roles in development and cancer, the mechanisms that specify invasive cellular behavior are poorly understood. Through a screen of transcription factors in Caenorhabditis elegans, we identified G1 cell-cycle arrest as a precisely regulated requirement of the anchor cell (AC) invasion program. We show that the nuclear receptor nhr-67/tlx directs the AC into G1 arrest in part through regulation of the cyclin-dependent kinase inhibitor cki-1. Loss of nhr-67 resulted in non-invasive, mitotic ACs that failed to express matrix metalloproteinases or actin regulators and lack invadopodia, F-actin-rich membrane protrusions that facilitate invasion. We further show that G1 arrest is necessary for the histone deacetylase HDA-1, a key regulator of differentiation, to promote pro-invasive gene expression and invadopodia formation. Together, these results suggest that invasive cell fate requires G1 arrest and that strategies targeting both G1-arrested and actively cycling cells may be needed to halt metastatic cancer.

Invadopodia and basement membrane invasion in vivo

Over 20 years ago, protrusive, F-actin-based membrane structures, termed invadopodia, were identified in highly metastatic cancer cell lines. Invadopodia penetrate artificial or explanted extracellular matrices in 2D culture conditions and have been hypothesized to facilitate the migration of cancer cells through basement membrane, a thin, dense, barrier-like matrix surrounding most tissues. Despite intensive study, the identification of invadopodia in vivo has remained elusive and until now their possible roles during invasion or even existence have remained unclear. Studies in remarkably different cellular contexts-mouse tumor models, zebrafish intestinal epithelia, and C. elegans organogenesis-have recently identified invadopodia structures associated with basement membrane invasion. These studies are providing the first in vivo insight into the regulation, function, and role of these fascinating subcellular devices with critical importance to both development and human disease.

Further insights into cortactin conformational regulation

The actin regulatory protein cortactin is involved in multiple signaling pathways impinging on the cortical actin cytoskeleton. Cortactin is phosphorylated by ERK1/2 and Src family tyrosine kinases, resulting in neuronal Wiskott Aldrich Syndrome protein (N-WASp) activation and enhanced actin related protein (Arp)2/3-mediated actin nucleation. Cortactin migrates as an 80/85 kDa doublet when analyzed by SDS-PAGE. Phosphorylation by ERK1/2 is associated with conversion of the 80 kDa to the 85 kDa form, postulated to occur by inducing a conformational alteration that releases the carboxyl-terminal SH3 domain from autoinhibition. Our recent analysis of the 80-85 kDa cortactin "shift" in tumor cells indicates that while ERK1/2 phosphorylation is associated with the 85 kDa shift, this phosphorylation event is not required for the shift to occur, nor does ERK1/2 phosphorylation appreciably alter global cortactin confirmation. These data indicate that additional factors besides ERK1/2 phosphorylation contribute to generating and/or maintaining the activated 85 kDa cortactin form in stimulated cells.

Traversing the basement membrane in vivo: a diversity of strategies

The basement membrane is a dense, highly cross-linked, sheet-like extracellular matrix that underlies all epithelia and endothelia in multicellular animals. During development, leukocyte trafficking, and metastatic disease, cells cross the basement membrane to disperse and enter new tissues. Based largely on in vitro studies, cells have been thought to use proteases to dissolve and traverse this formidable obstacle. Surprisingly, recent in vivo studies have uncovered a remarkably diverse range of cellular- and tissue-level strategies beyond proteolysis that cells use to navigate through the basement membrane. These fascinating and unexpected mechanisms have increased our understanding of how cells cross this matrix barrier in physiological and disease settings.

ADF/cofilin promotes invadopodial membrane recycling during cell invasion in vivo

Localized F-actin disassembly by ADF/cofilin drives invadopodial membrane recycling through endolysosomes, which promotes efficient cell transmigration through the basement membrane.

Invadopodia are protrusive, F-actin–driven membrane structures that are thought to mediate basement membrane transmigration during development and tumor dissemination. An understanding of the mechanisms regulating invadopodia has been hindered by the difficulty of examining these dynamic structures in native environments. Using an RNAi screen and live-cell imaging of anchor cell (AC) invasion in Caenorhabditis elegans, we have identified UNC-60A (ADF/cofilin) as an essential regulator of invadopodia. UNC-60A localizes to AC invadopodia, and its loss resulted in a dramatic slowing of F-actin dynamics and an inability to breach basement membrane. Optical highlighting indicated that UNC-60A disassembles actin filaments at invadopodia. Surprisingly, loss of unc-60a led to the accumulation of invadopodial membrane and associated components within the endolysosomal compartment. Photobleaching experiments revealed that during normal invasion the invadopodial membrane undergoes rapid recycling through the endolysosome. Together, these results identify the invadopodial membrane as a specialized compartment whose recycling to form dynamic, functional invadopodia is dependent on localized F-actin disassembly by ADF/cofilin.

NEDD9 regulates actin dynamics through cortactin deacetylation in an AURKA/HDAC6-dependent manner

The prometastatic protein NEDD9 (neural precursor cell expressed, developmentally downregulated 9) is highly expressed in many cancers and is required for mesenchymal individual cell migration and progression to the invasive stage. Nevertheless, the molecular mechanisms of NEDD9-driven migration and the downstream targets effecting metastasis are not well defined. In the current study, knockdown of NEDD9 in highly metastatic tumor cells drastically reduces their migratory capacity due to disruption of actin dynamics at the leading edge. Specifically, NEDD9 deficiency leads to a decrease in the persistence and stability of lamellipodial protrusions similar to knockdown of cortactin (CTTN). Mechanistically, it was shown that NEDD9 binds to and regulates acetylation of CTTN in an Aurora A kinase (AURKA)/HDAC6-dependent manner. The knockdown of NEDD9 or AURKA results in an increase in the amount of acetylated CTTN and a decrease in the binding of CTTN to F-actin. Overexpression of the deacetylation mimicking (9KR) mutant of CTTN is sufficient to restore actin dynamics at the leading edge and migration proficiency of the tumor cells. Inhibition of AURKA and HDAC6 activity by alisertib and Tubastatin A in xenograft models of breast cancer leads to a decrease in the number of pulmonary metastases. Collectively, these findings identify CTTN as the key downstream component of NEDD9-driven migration and metastatic phenotypes.

IMPLICATIONS

This study provides a mechanistic platform for therapeutic interventions based on AURKA and HDAC6 inhibition for patients with metastatic breast cancer to prevent and/or eradicate metastases.

Ableson kinases negatively regulate invadopodia function and invasion in head and neck squamous cell carcinoma by inhibiting an HB-EGF autocrine loop

Head and neck squamous cell carcinoma (HNSCC) has a proclivity for locoregional invasion. HNSCC mediates invasion in part through invadopodia-based proteolysis of the extracellular matrix (ECM). Activation of Src, Erk1/2, Abl and Arg downstream of epidermal growth factor receptor (EGFR) modulates invadopodia activity through phosphorylation of the actin regulatory protein cortactin. In MDA-MB-231 breast cancer cells, Abl and Arg function downstream of Src to phosphorylate cortactin, promoting invadopodia ECM degradation activity and thus assigning a pro-invasive role for Ableson kinases. We report that Abl kinases have an opposite, negative regulatory role in HNSCC where they suppress invadopodia and tumor invasion. Impairment of Abl expression or Abl kinase activity with imatinib mesylate enhanced HNSCC matrix degradation and 3D collagen invasion, functions that were impaired in MDA-MB-231. HNSCC lines with elevated EGFR and Src activation did not contain increased Abl or Arg kinase activity, suggesting that Src could bypass Abl/Arg to phosphorylate cortactin and promote invadopodia ECM degradation. Src-transformed Abl(-/-)/Arg(-/-) fibroblasts produced ECM degrading invadopodia containing pY421 cortactin, indicating that Abl/Arg are dispensable for invadopodia function in this system. Imatinib-treated HNSCC cells had increased EGFR, Erk1/2 and Src activation, enhancing cortactin pY421 and pS405/418 required for invadopodia function. Imatinib stimulated shedding of the EGFR ligand heparin-binding EGF-like growth factor (HB-EGF) from HNSCC cells, where soluble HB-EGF enhanced invadopodia ECM degradation in HNSCC but not in MDA-MB-231. HNSCC cells treated with inhibitors of the EGFR-invadopodia pathway indicated that EGFR and Src are required for invadopodia function. Collectively, our results indicate that Abl kinases negatively regulate HNSCC invasive processes through suppression of an HB-EGF autocrine loop responsible for activating a EGFR-Src-cortactin cascade, in contrast to the invasion promoting functions of Abl kinases in breast and other cancer types. Our results provide mechanistic support for recent failed HNSCC clinical trials utilizing imatinib.

Abstract 4936: Ableson kinases negatively regulate invadopodia function and invasion in head and neck squamous cell carcinoma by inhibiting an HB-EGF autocrine loop

Head and neck squamous cell carcinoma (HNSCC) has a proclivity for locoregional invasion. HNSCC mediates invasion in part through invadopodia-based proteolysis of the extracellular matrix (ECM). Activation of Src, Erk1/2, Abl and Arg downstream of epidermal growth factor receptor (EGFR) modulates invadopodia activity through phosphorylation of the actin regulatory protein cortactin. In MDA-MB-231 breast cancer cells, Abl and Arg function downstream of Src to phosphorylate cortactin, promoting invadopodia ECM degradation activity and thus assigning a pro-invasive role for Ableson kinases. We report that Abl kinases have an opposite, negative regulatory role in HNSCC where they suppress invadopodia and tumor invasion. Impairment of Abl expression or Abl kinase activity with imatinib mesylate enhanced HNSCC matrix degradation and 3D collagen invasion, functions that were impaired in MDA-MB-231. HNSCC lines with elevated EGFR and Src activation did not contain increased Abl or Arg kinase activity, suggesting Src could bypass Abl/Arg to phosphorylate cortactin and promote invadopodia ECM degradation. Src transformed Abl-/-/Arg-/- fibroblasts produced ECM degrading invadopodia containing pY421 cortactin, indicating that Abl/Arg are dispensable for invadopodia function in this system. Imatinib treated HNSCC cells had increased EGFR, Erk1/2 and Src activation, enhancing cortactin pY421 and pS405/418 required for invadopodia function. Imatinib stimulated shedding of the EGFR ligand heparin-binding EGF-like growth factor (HB-EGF) from HNSCC cells, where soluble HB-EGF enhanced invadopodia ECM degradation in HNSCC but not in MDA-MB-231. HNSCC cells treated with therapeutic inhibitors of the EGFR invadopodia pathway indicated that EGFR and Src are required for invadopodia function. Collectively our results indicate that Abl kinases negatively regulate HNSCC invasive processes through suppression of an HB-EGF autocrine loop responsible for activating an EGFR-Src-cortactin cascade, in contrast to the invasion promoting functions of Abl kinases in breast and other cancer types. Our results provide mechanistic support for recent failed HNSCC clinical trials utilizing imatinib.

Citation Format: Karen E. Hayes, Elyse L. Walk, Amanda G. Ammer, Laura C. Kelley, Karen H. Martin, Scott A. Weed. Ableson kinases negatively regulate invadopodia function and invasion in head and neck squamous cell carcinoma by inhibiting an HB-EGF autocrine loop. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4936. doi:10.1158/1538-7445.AM2013-4936

Cortactin is a substrate of activated Cdc42-associated kinase 1 (ACK1) during ligand-induced epidermal growth factor receptor downregulation

Background

Epidermal growth factor receptor (EGFR) internalization following ligand binding controls EGFR downstream pathway signaling activity. Internalized EGFR is poly-ubiquitinated by Cbl to promote lysosome-mediated degradation and signal downregulation. ACK1 is a non-receptor tyrosine kinase that interacts with ubiquitinated EGFR to facilitate EGFR degradation. Dynamic reorganization of the cortical actin cytoskeleton controlled by the actin related protein (Arp)2/3 complex is important in regulating EGFR endocytosis and vesicle trafficking. How ACK1-mediated EGFR internalization cooperates with Arp2/3-based actin dynamics during EGFR downregulation is unclear.

Methodology/Principal Findings

Here we show that ACK1 directly binds and phosphorylates the Arp2/3 regulatory protein cortactin, potentially providing a direct link to Arp2/3-based actin dynamics during EGFR degradation. Co-immunoprecipitation analysis indicates that the cortactin SH3 domain is responsible for binding to ACK1. In vitro kinase assays demonstrate that ACK1 phosphorylates cortactin on key tyrosine residues that create docking sites for adaptor proteins responsible for enhancing Arp2/3 nucleation. Analysis with phosphorylation-specific antibodies determined that EGFR-induced cortactin tyrosine phosphorylation is diminished coincident with EGFR degradation, whereas ERK1/2 cortactin phosphorylation utilized in promoting activation of the Arp2/3 regulator N-WASp is sustained during EGFR downregulation. Cortactin and ACK1 localize to internalized vesicles containing EGF bound to EGFR visualized by confocal microscopy. RNA interference and rescue studies indicate that ACK1 and the cortactin SH3 domain are essential for ligand-mediated EGFR internalization.

Conclusions/Significance

Cortactin is a direct binding partner and novel substrate of ACK1. Tyrosine phosphorylation of cortactin by ACK1 creates an additional means to amplify Arp2/3 dynamics through N-WASp activation, potentially contributing to the overall necessary tensile and/or propulsive forces utilized during EGFR endocytic internalization and trafficking involved in receptor degradation.

Revisiting the ERK/Src cortactin switch

The filamentous (F)-actin regulatory protein cortactin plays an important role in tumor cell movement and invasion by promoting and stabilizing actin related protein (Arp)2/3-mediated actin networks necessary for plasma membrane protrusion. Cortactin is a substrate for ERK1/2 and Src family kinases, with previous in vitro findings demonstrating ERK1/2 phosphorylation of cortactin as a positive and Src phosphorylation as a negative regulatory event in promoting Arp2/3 activation through neuronal Wiskott Aldrich Syndrome protein (N-WASp). Evidence for this regulatory cortactin "switch" in cells has been hampered due to the lack of phosphorylation-specific antibodies that recognize ERK1/2-phosphorylated cortactin. Our findings with phosphorylation-specific antibodies against these ERK1/2 sites (pS405 and pS418) indicate that cortactin can be co-phosphorylated at 405/418 and tyrosine residues targeted by Src family tyrosine kinases. These results indicate that the ERK/Src cortactin switch is not the sole mechanism by which ERK1/2 and tyrosine phosphorylation events regulate cortactin function in cell systems.

Cortactin phosphorylated by ERK1/2 localizes to sites of dynamic actin regulation and is required for carcinoma lamellipodia persistence

Background

Tumor cell motility and invasion is governed by dynamic regulation of the cortical actin cytoskeleton. The actin-binding protein cortactin is commonly upregulated in multiple cancer types and is associated with increased cell migration. Cortactin regulates actin nucleation through the actin related protein (Arp)2/3 complex and stabilizes the cortical actin cytoskeleton. Cortactin is regulated by multiple phosphorylation events, including phosphorylation of S405 and S418 by extracellular regulated kinases (ERK)1/2. ERK1/2 phosphorylation of cortactin has emerged as an important positive regulatory modification, enabling cortactin to bind and activate the Arp2/3 regulator neuronal Wiskott-Aldrich syndrome protein (N-WASp), promoting actin polymerization and enhancing tumor cell movement.

Methodology/Principal Findings

In this report we have developed phosphorylation-specific antibodies against phosphorylated cortactin S405 and S418 to analyze the subcellular localization of this cortactin form in tumor cells and patient samples by microscopy. We evaluated the interplay between cortactin S405 and S418 phosphorylation with cortactin tyrosine phosphorylation in regulating cortactin conformational forms by Western blotting. Cortactin is simultaneously phosphorylated at S405/418 and Y421 in tumor cells, and through the use of point mutant constructs we determined that serine and tyrosine phosphorylation events lack any co-dependency. Expression of S405/418 phosphorylation-null constructs impaired carcinoma motility and adhesion, and also inhibited lamellipodia persistence monitored by live cell imaging.

Conclusions/Significance

Cortactin phosphorylated at S405/418 is localized to sites of dynamic actin assembly in tumor cells. Concurrent phosphorylation of cortactin by ERK1/2 and tyrosine kinases enables cells with the ability to regulate actin dynamics through N-WASp and other effector proteins by synchronizing upstream regulatory pathways, confirming cortactin as an important integration point in actin-based signal transduction. Reduced lamellipodia persistence in cells with S405/418A expression identifies an essential motility-based process reliant on ERK1/2 signaling, providing additional understanding as to how this pathway impacts tumor cell migration.

Oncogenic Src requires a wild-type counterpart to regulate invadopodia maturation

The proto-oncogene Src tyrosine kinase (Src) is overexpressed in human cancers and is currently a target of anti-invasive therapies. Activation of Src is an essential catalyst of invadopodia production. Invadopodia are cellular structures that mediate extracellular matrix (ECM) proteolysis, allowing invasive cell types to breach confining tissue barriers. Invadopodia assembly and maturation is a multistep process, first requiring the targeting of actin-associated proteins to form pre-invadopodia, which subsequently mature by recruitment and activation of matrix metalloproteases (MMPs) that facilitate ECM degradation. We demonstrate that active, oncogenic Src alleles require the presence of a wild-type counterpart to induce ECM degradation at invadopodia sites. In addition, we identify the phosphorylation of the invadopodia regulatory protein cortactin as an important mediator of invadopodia maturation downstream of wild-type Src. Distinct phosphotyrosine-based protein-binding profiles in cells forming pre-invadopodia and mature invadopodia were identified by SH2-domain array analysis. These results indicate that although elevated Src kinase activity is required to target actin-associated proteins to pre-invadopodia, regulated Src activity is required for invadopodia maturation and matrix degradation activity. Our findings describe a previously unappreciated role for proto-oncogenic Src in enabling the invasive activity of constitutively active Src alleles.

Saracatinib Impairs Head and Neck Squamous Cell Carcinoma Invasion by Disrupting Invadopodia Function

Elevated Src kinase activity is linked to the progression of solid tumors, including head and neck squamous cell carcinoma (HNSCC). Src regulates HNSCC proliferation and tumor invasion, with the Src-targeted small molecule inhibitor saracatinib displaying potent anti-invasive effects in preclinical studies. However, the pro-invasive cellular mechanism(s) perturbed by saracatinib are unclear. The anti-proliferative and anti-invasive effects of saracatinib on HNSCC cell lines were therefore investigated in pre-clinical cell and mouse model systems. Saracatinib treatment inhibited growth, cell cycle progression and transwell Matrigel invasion in HNSCC cell lines. Dose-dependent decreases in Src activation and phosphorylation of the invasion-associated substrates focal adhesion kinase, p130 CAS and cortactin were also observed. While saracatinib did not significantly impact HNSCC tumor growth in a mouse orthotopic model of tongue squamous cell carcinoma, impaired perineural invasion and cervical lymph node metastasis was observed. Accordingly, saracatinib treatment displayed a dose-dependent inhibitory effect on invadopodia formation, extracellular matrix degradation and matrix metalloprotease 9 activation. These results suggest that inhibition of Src kinase by saracatinib impairs the pro-invasive activity of HNSCC by inhibiting Src substrate phosphorylation important for invadopodia formation and associated matrix metalloprotease activity.

Cortactin overexpression regulates actin-related protein 2/3 complex activity, motility, and invasion in carcinomas with chromosome 11q13 amplification

Carcinoma cell motility and invasion are prerequisites for tumor cell metastasis, which requires regulation of the actin cytoskeleton. Cortactin is an actin-related protein 2/3 (Arp2/3) complex-activating and filamentous (F)-actin-binding protein that is implicated in tumor cell motility and metastasis, partially by its ability to become tyrosine phosphorylated. Cortactin is encoded by the CTTN gene and maps to chromosome 11q13, a region amplified in many carcinomas, including head and neck squamous cell carcinoma (HNSCC). CTTN gene amplification is associated with lymph node metastasis and poor patient outcome, and cortactin overexpression enhances motility in tumor cells lacking 11q13 amplification. However, a direct link between increased motility and invasion has not been reported in tumor cells with chromosome 11q13 amplification and cortactin overexpression. In this study, we have examined the relationship between CTTN amplification and tumor cell motility in HNSCC. In 11 of 39 (28%) HNSCC cases, cortactin overexpression determined by immunohistochemistry correlates with lymph node metastasis and CTTN gene amplification. HNSCC cells containing cortactin gene amplification and protein overexpression display increased binding and activation of Arp2/3 complex, and were more motile and invasive than HNSCC cells lacking CTTN amplification. Down-regulation of cortactin expression in CTTN-amplified HNSCC cells by small interfering RNA impairs HNSCC motility and invasion. Treatment of HNSCC cells with the epidermal growth factor receptor inhibitor gefitinib inhibits HNSCC motility and down-regulates cortactin tyrosine phosphorylation. These data suggest that cortactin may be a valid prognostic and therapeutic marker for invasive and metastatic HNSCC and other carcinomas with 11q13 amplification.

PI3K activation is required for PMA-directed activation of cSrc by AFAP-110

Activation of PKCalpha will induce the cSrc binding partner AFAP-110 to colocalize with and activate cSrc. The ability of AFAP-110 to colocalize with cSrc is contingent on the integrity of the amino-terminal pleckstrin homology (PH1) domain, while the ability to activate cSrc is dependent on the integrity of its SH3 binding motif, which engages the cSrc SH3 domain. The outcome of AFAP-110-directed cSrc activation is a change in actin filament integrity and the formation of podosomes. Here, we address what cellular signals promote AFAP-110 to colocalize with and activate cSrc, in response to PKCalpha activation or PMA treatment. Because PH domain integrity in AFAP-110 is required for colocalization, and PH domains are known to interact with both protein and lipid binding partners, we sought to determine whether phosphatidylinositol 3-kinase (PI3K) activation played a role in PMA-induced colocalization between AFAP-110 and cSrc. We show that PMA treatment is able to direct activation of PI3K. Treatment of mouse embryo fibroblast with PI3K inhibitors blocked PMA-directed colocalization between AFAP-110 and cSrc and subsequent cSrc activation. PMA also was unable to induce colocalization or cSrc activation in cells that lacked the p85alpha and -beta regulatory subunits of PI3K. This signaling pathway was required for migration in a wound healing assay. Cells that were null for cSrc or the p85 regulatory subunits or expressed a dominant-negative AFAP-110 also displayed a reduction in migration. Thus PI3K activity is required for PMA-induced colocalization between AFAP-110 and cSrc and subsequent cSrc activation, and this signaling pathway promotes cell migration.

The cyclin-dependent kinases cdk2 and cdk5 act by a random, anticooperative kinetic mechanism

cdk2.cyclin E and cdk5.p25 are two members of the cyclin-dependent kinase family that are potential therapeutic targets for oncology and Alzheimer's disease, respectively. In this study we have investigated the mechanism for these enzymes. Kinases catalyze the transfer of phosphate from ATP to a protein acceptor, thus utilizing two substrates, ATP and the target protein. For a two-substrate reaction, possible kinetic mechanisms include: ping-pong, sequential random, or sequential ordered. To determine the kinetic mechanism of cdk2.GST-cyclin E and cdk5.GST-p25, kinase activity was measured in experiments in which concentrations of peptide and ATP substrates were varied in the presence of dead-end inhibitors. A peptide identical to the peptide substrate, but with a substitution of valine for the phosphoacceptor threonine, competed with substrate with a K(i) value of 0.6 mm. An aminopyrimidine, PNU 112455A, was identified in a screen for inhibitors of cdk2. Nonlinear least squares and Lineweaver-Burk analyses demonstrated that the inhibitor PNU 112455A was competitive with ATP with a K(i) value of 2 microm. In addition, a co-crystal of PNU 112455A with cdk2 showed that the inhibitor binds in the ATP binding pocket of the enzyme. Analysis of the inhibitor data demonstrated that both kinases use a sequential random mechanism, in which either ATP or peptide may bind first to the enzyme active site. For both kinases, the binding of the second substrate was shown to be anticooperative, in that the binding of the first substrate decreases the affinity of the second substrate. For cdk2.GST-cyclin E the kinetic parameters were determined to be K(m, ATP) = 3.6 +/- 1.0 microm, K(m, peptide) = 4.6 +/- 1.4 microm, and the anticooperativity factor, alpha = 130 +/- 44. For cdk5.GST-p25, the K(m, ATP) = 3.2 +/- 0.7 microm, K(m, peptide) = 1.6 +/- 0.3 microm, and alpha = 7.2 +/- 1.8.

Immunohistochemistry of ultimobranchial thyroid carcinomas in seven slaughtered cows and one bull

Eight thyroid gland epithelial tumors were found in 7 cows and 1 bull in a retrospective study of thyroid gland lesions in slaughtered cattle. All tumors were classified as ultimobranchial thyroid carcinomas based on morphology and immunohistochemistry. All tumors consisted of solid sheets and nests of polygonal to oval epithelial cells, with more sparsely dispersed colloid-filled follicles. Connective tissue separating nests of epithelial cells varied from delicate fibrovascular stroma to dense collagenous stroma. Fusiform epithelial cells with rare neural fibers and ganglion cells were present in 1 tumor. Cells within solid areas of these tumors were immunoreactive for calcitonin, calcitonin gene-related peptide, neuron-specific enolase, and synaptophysin. Colloid and follicle cells were immunoreactive for thyroglobulin. Few follicle cells also were reactive for calcitonin gene-related peptide. Neoplastic cells invaded the fibrous capsules in all 8 cattle. These tumors represented proliferation of a mixed population of undifferentiated cells, C cells, and thyroid follicular epithelial cells, presumably derived from the thyroid ultimobranchial bodies. These ultimobranchial carcinomas in slaughtered cattle are comparable to ultimobranchial tumors described in dairy bulls and the intermediate type of thyroid gland carcinomas (mixed thyroid medullary carcinomas) described in human beings.

A rapid DNA isolation procedure for the identification of Campylobacter jejuni by the polymerase chain reaction

We have developed an efficient process for rapidly isolating campylobacter DNA using mechanical disruption combined with the guanidine-based reagent DNAzol. Template DNA was isolated by this method from cultures of Campylobacter jejuni resistant to lysis by boiling or enzymes and identified following polymerase chain reaction (PCR) amplification using primers specific for the hippuricase gene. Direct detection of campylobacters in poultry-processing samples by PCR is demonstrated in chicken carcass rinses spiked with lysis-resistant C. jejuni. Our results indicate that this method of DNA isolation may be ideal for direct PCR detection of pathogenic bacteria in complex samples of widely varied origin, especially when the target organisms are difficult to lyse by other means.

An evaluation of methods for the detection of spinal cord in product derived from advanced meat recovery systems

This study investigated the usefulness of immunohistochemistry, histochemistry, and polarization microscopy in documenting the presence of spinal cord in ground product produced by advanced meat recovery systems (AMRS). A battery of diagnostic stains proved most helpful for definitive documentation of spinal cord in the AMRS product. Antibodies to neurofilament and glial fibrillary acidic proteins were useful for highlighting the presence of neural tissue in comminuted product but when used alone did not definitively differentiate central nervous system tissue from peripheral nerve. Polariscopy, trichrome staining, and immunostaining for synaptophysin were very useful for differentiating spinal cord from peripheral nerve. Spinal cord was found in 2 of 196 AMRS samples when only hematoxylin and eosin staining was used. In a later immunohistochemical subset of the survey study, spinal cord was found in 7 of 17 AMRS samples. More recently, spinal cord tissue has been found in 3 of 26 regulatory samples using hematoxylin and eosin stains combined with immunohistochemical techniques.

Detection of multidrug-resistant Salmonella enterica serotype typhimurium DT104 based on a gene which confers cross-resistance to florfenicol and chloramphenicol

Salmonella enterica serotype typhimurium (S. typhimurium) DT104 (DT104) first emerged as a major pathogen in Europe and is characterized by its pentadrug-resistant pattern. It has also been associated with outbreaks in the United States. The organism typically carries resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. The mechanism of chloramphenicol resistance in DT104 was determined by producing antibiotic-resistant Escherichia coli host strain clones from DT104 DNA. DNA from chloramphenicol-resistant clones was sequenced, and probes specific for the genes floS. typhimurium (floSt), int, invA, and spvC were produced for colony blot hybridizations. One hundred nine Salmonella isolates, including 44 multidrug-resistant DT104 isolates, were tested to evaluate the specificities of the probes. The gene floSt, reported in this study, confers chloramphenicol and florfenicol resistance on S. typhimurium DT104. Florfenicol resistance is unique to S. typhimurium DT104 and multidrug-resistant S. typhimurium isolates with the same drug resistance profile among all isolates evaluated. Of 44 DT104 isolates tested, 98% were detected based on phenotypic florfenicol resistance and 100% had the floSt-positive genotype. Resistances to florfenicol and chloramphenicol are conferred by the gene floSt, described in this paper. Presumptive identification of S. typhimurium DT104 can be made rapidly based on the presence of the floSt gene or its resulting phenotype.

Pulmonary sarcomas in a young chicken

Both lungs of a 5-wk-old broiler chicken contained miliary, round, white tumors. Microscopically, these masses were composed of compactly arranged cells with round to oval nuclei and indistinct cytoplasmic borders. Immunohistochemically, tumor cells were positive for vimentin but negative for cytokeratin, S-100 protein, neuron-specific enolase, smooth muscle actin, and muscle-specific actin. Ultrastructurally, tumor cells were separated by collagen bands and some contained collagen fibrils. These results suggest that the primitive mesenchymal cells composing these sarcomas may have originated from precursors of interstitial cells or fibroblasts of the interparabronchial or interatrial septa. DNA was extracted from paraffin-embedded tissues and probed for sequences specific for Marek's disease virus, reticuloendotheliosis viruses, exogenous avian leukosis viruses, and subgroup J avian leukosis viruses. Only sequences specific for subgroup J avian leukosis viruses were identified in the DNA extracted from tumors and surrounding lung.

Equine malignant lymphomas: morphologic and immunohistochemical classification

Gross lesions, microscopic appearance, and immunophenotyping are reported in a retrospective study of 31 cases of equine malignant lymphoma. Immunohistochemical studies were performed on archived formalin-fixed, paraffin-embedded tissues. Monoclonal antibodies to surface glycoprotein BLA.36 and intracytoplasmic domains of mb-1 and B29 were used to document the presence of B lymphocytes in the equine tumors. Polyclonal antibody to CD3 and monoclonal antibodies to T-lymphocyte markers CD3 and CD5 revealed the presence of variable numbers of T cells within the equine lymphomas. The neoplastic component of the equine lymphomas was determined through morphologic evaluation, immunophenotyping, and the use of proliferation markers Ki-67 and proliferating cell nuclear antigen. Equine malignant lymphomas were composed of a heterogeneous cell population. Most tumors contained B and T lymphocytes. Twenty-four horses had diffuse lymphomas derived from B lymphocytes. Thirteen of these lymphomas contained primarily neoplastic B lymphocytes. Eleven additional cases of diffuse large B-cell lymphoma contained from 40% to 80% nonneoplastic T lymphocytes and were classified as T-cell-rich, large B-cell lymphomas. This is the first description of T-cell-rich, B-cell lymphoma in the horse. Six tumors with a diffuse architecture were derived from T lymphocytes. Four T-cell tumors were large-cell tumors, 1 was a small-cell tumor, and in 1 tumor the size of the cells could not be determined accurately because of autolytic change in the tissues. One diffuse large-cell lymphoma did not react with either B- or T-cell markers.

Regression of subcutaneous lymphoma following removal of an ovarian granulosatheca cell tumor in a horse

A 9-year-old Arabian mare was admitted for evaluation of multiple subcutaneous nodules and infertility. Fine-needle aspiration of one of the subcutaneous nodules resulted in a cytologic diagnosis of histiolymphocytic lymphoma. Palpation per rectum and transrectal ultrasonography revealed a mass associated with the left ovary. Excision of the ovarian tumor was performed, and a histopathologic diagnosis of granulosa-theca cell tumor was made. After removal of the granulosa-theca cell tumor, subcutaneous nodules regressed. The referring veterinarian reported that the nodules had also disappeared and then recurred after administration of a synthetic progestin. To further characterize the lymphoma and investigate this possible hormonal relationship, immunophenotyping and estrogen and progesterone receptor assays were performed. The subcutaneous lymphoma was classified as a T-cell rich B-cell lymphoma, results of estrogen receptor assays were negative, and results of progesterone receptor assays were positive. Clinical observations of subcutaneous lymphoma in horses indicate that the waxing and waning nature of these tumors may be associated with the estrous cycle, pregnancy, foaling, and lactation. Clinical observations and identification of progesterone receptors suggest that a relationship between serum steroid hormone concentrations, such as estrogen and progesterone, and subcutaneous lymphoma may exists.

Detection of equine and bovine T- and B-lymphocytes in formalin-fixed paraffin-embedded tissues

Formalin-fixed paraffin-embedded sections of equine and bovine lymph nodes, spleen, thymus, and Peyer's patches were incubated with monoclonal antibodies to B-lymphocyte markers BLA.36, B29, and mb-1 and T-lymphocyte markers CD3 and CD5. The monoclonal antibody BLA.36 reacted with 80-90% of lymphocytes in the germinal centers and mantle zones of follicles in lymph nodes, spleen, and Peyer's patches. In addition, 90% of lymphocytes in the marginal zone of the spleen, and variable numbers of lymphocytes within lymph node medullary cords were immunopositive for BLA.36. Antibodies to B29 and mb-1 produced similar staining patterns as BLA.36 with fewer positive cells in the germinal centers and medullary cords. BLA.36, B29, and mb-1 reacted with 30-50% of lymphocytes in the medulla of the thymus and with 5-10% of lymphocytes in the cortex. CD3 and CD5 reacted with 90% of lymphocytes in the paracortex and parafollicular zones of lymph nodes, spleen, and Peyer's patches; 40-50% of lymphocytes in the medullary cords of lymph nodes, and scattered positive cells within follicles. Anti-CD3 antibody reacted with 95% of lymphocytes in the splenic red pulp, but antibodies directed against CD5 reacted only faintly with approximately 5-10% of lymphocytes in the red pulp. CD3 and CD5 reacted with 50-60% of cells in the medulla of the thymus and with 40-80% of lymphocytes in the thymic cortex. The biochemical characterization of the antibodies by Western blotting against lysates of equine and bovine peripheral blood mononuclear cells confirmed that antibodies to BLA.36, mb-1, B29, CD3, and CD5 detected molecules of the same approximate molecular mass as found on lymphoid cells of human beings and rats.

A retrospective study of pancreatic tumors in slaughter cattle

Sixteen primary pancreatic tumors were found in a retrospective study of bovine pancreatic lesions detected in slaughtered cattle. Eleven islet cell tumors and three pancreatic exocrine carcinomas were identified based on light microscopy and immunohistochemistry. Nine of 11 islet cell tumors were classified as malignant. Metastatic sites included iliac, mediastinal, hepatic, and mesenteric lymph nodes, peritoneum, mesentery, and liver. Six cows with multiple islet cell tumors also had pheochromocytomas. All 11 islet cell tumors had positive immunoreactivity to insulin and somatostatin. Three tumors also contained cells immunoreactive for glucagon and two tumors contained pancreatic polypeptide immunoreactive cells. Immunoreactivity of tumor cells in metastatic sites was similar to their respective primary tumors. All exocrine pancreatic carcinomas metastasized widely and were immunonegative for insulin, somatostatin, glucagon, and pancreatic polypeptide. No mixed endocrine-exocrine tumors were identified. None of the endocrine or exocrine tumors contained amyloid. Additional primary tumors of the bovine pancreas included one neurofibroma and one neurofibrosarcoma. Additional cases with lesions of the bovine pancreas included nodular hyperplasia in 15 cows, exocrine acinar atrophy and fibrosis in four cows (two of which also had pancreatic lithiasis), pancreatitis in one cow, peripancreatic fibrosis in two cows, pancreatic steatosis in one animal, and pancreatic hemorrhages in one cow.

A retrospective study of multicentric bovine renal cell tumors

Tissues from twenty mature cows with primary renal cell tumors were submitted over an 11-year period because of gross lesions detected during routine slaughter and inspection. Tumors visualized grossly were multiple and bilateral in seven cattle, multiple within one kidney in four cattle, and solitary in nine cattle. The tumors were primarily cortical, yellow-orange to tan, proliferative, well circumscribed, and extended above the capsular surface of the kidney. Tumors were microscopically multiple even when grossly described as solitary lesions, except in one cow. Twelve tumors (60%) were microscopically multiple in one kidney, seven tumors (35%) were multiple and bilateral, and only one cow (5%) exhibited extrarenal metastasis. Tumors from nineteen cows were composed of eosinophilic granular epithelial cells; tumors from one cow were clear cell type. Each tumor contained several histologic patterns. Corpora amylacea, proteinaceous secretions, and hemosiderin were characteristic findings in bovine renal cell carcinoma. All 20 cows with renal cell tumors exhibited positive immunoreactivity to uromodulin (Tamm-Horsfall protein).

Multicentric histiocytosis in young chickens. Gross and light microscopic pathology

During 1991-94, tissue specimens from 262 young chicken carcasses condemned at slaughter contained novel multicentric proliferations of histiocytelike cells. These tissues had been submitted to the USDA FSIS Eastern Laboratory because of grossly enlarged spleens, livers, or kidneys. The spleens were two to three times normal diameter and contained miliary white or yellow 1-3-mm foci. Similar miliary foci were present throughout the enlarged livers and kidneys. Microscopic examination of these tissues revealed discrete circular nodules expanding splenic periarteriolar lymphoid sheaths, hepatic periportal nodules, and discrete perivascular and more diffuse interstitial nodules replacing renal tubules. Nodules also were present in the pancreas, bone marrow, proventriculus, and lung, with more diffuse infiltrates in intestinal lamina propria. The cells composing these nodules contained irregularly oval, folded, or pleomorphic nuclei and relatively abundant eosinophilic cytoplasm. Mitotic figures and pyknotic nuclei were common. These cells were interpreted to be histiocytes (tissue macrophages or dendritic cells) and did not resemble lymphocytes. These proliferating cells also did not resemble the cell population of commonly diagnosed lymphoid neoplasms of young chickens. No intralesional organisms were detected and polymerase chain reaction analysis failed to detect Marek's herpesvirus DNA or leukosis/sarcoma and reticuloendotheliosis proviral DNA.

Icterus in bob veal calves and its association with lack of colostrum intake and high serum creatine kinase activity

Icterus condemnations compose a substantial proportion (41%) of total condemnations of bob veal, the class of veal composed of calves < 3 weeks old and weighing up to 68 kg. At postmortem examination, bob veal condemned because of icterus have generalized yellow discoloration of tissues, which is commonly associated with large, yellow liver (fatty liver), and a paucity of other gross pathologic changes. To establish that the generalized yellow discoloration was attributable to high tissue bilirubin concentrations and to examine the underlying mechanism(s) that might be responsible, blood samples and tissue specimens were obtained from clinically normal and icteric bob veal calves at slaughter. For comparison, blood samples were collected from clinically normal, 1- to 5-day-old Holstein calves being raised on local dairy farms. Hematologic and serum biochemical analyses were obtained for the 3 groups of calves (normal local, normal slaughter, and icteric slaughter), and tissues of slaughter calves were examined for histologic evidence of inflammatory or degenerative changes. Mean +/- SD total bilirubin concentration and creatine kinase (CK) activity in icteric bob veal (3.3 +/- 0.8 mg/dl; 869 +/- 788 U/L), normal bob veal (1.4 +/- 0.7 mg/dl; 486 +/- 890 U/L), and normal local calves (0.5 +/- 0.2 mg/dl; 156 +/- 158 U/L) were significantly different. When data for both normal and icteric bob veal calf groups were combined for analysis, total bilirubin concentration regressed significantly on hepatic lipid scores (P = 0.00003) and CK activity (P = 0.00049). Colostrum consumption was determined by measuring serum total protein concentration and serum gamma-glutamyltransferase activity. Bob veal calves that had not consumed colostrum had significantly higher total bilirubin (P = 0.00005) and CK (P = 0.0008) values. It was concluded that normal and icteric bob veal calves have significant increase in total bilirubin concentration, and icterus of bob veal calves is secondary to unconjugated hyperbilirubinemia. Lack of colostrum consumption was strongly correlated with icterus in bob veal calves.

Cutaneous Mycobacterium chelonei presenting in an immunocompetent host: case report and review of the literature

Mycobacterium chelonei is in the family of fast-growing atypical mycobacteria. Clinical infection can have varying presentations. We present a case of a nonhealing thigh abscess that grew Mycobacterium chelonei on culture. The clinical presentations and causes of Mycobacterium chelonei infections are reviewed, along with current treatment options.

Malignant melanocytic neural crest tumor in a young chicken (Gallus domesticus)

A malignant melanocytic tumor was found in an 8-week-old chicken. The tumor, which was composed of melanocytes, ganglion cells, nerves, and primitive pressure receptors, was examined by light microscopy, transmission electron microscopy, and immunohistochemistry. Antibodies to neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP), and S-100 protein variably stained nerves, but melanocytes were only rarely immunolabelled by NSE antibodies and there was no specific staining of these cells for S-100 or GFAP. Ultrastructurally, neoplastic melanocytes contained melanin within melanosomes and premelanosomes and did not resemble Schwann cells.

Alternate routes of invasion may affect pathogenesis of Salmonella typhimurium in swine

Transmission of Salmonella typhimurium in swine is traditionally believed to occur by the fecal-oral route, with invasion through the intestinal wall and Peyer's patches. However, involvement of the upper respiratory tract may be equally important. An esophagotomy was performed on 6- to 8-week-old pigs. Esophagotomized pigs were challenged intranasally with 10(9) CFU of S. typhimurium cells and necropsied at 3, 6, 12, and 18 h postinoculation (p.i.). By 3 h p.i., S. typhimurium was recovered from cecum, colon, head, and thoracic tissues and from the middle ileum involving a large number of Peyer's patches. The ileocolic lymph nodes and ileocolic junction were not positive for S. typhimurium until 6 and 12 h p.i., respectively. Additional pigs were inoculated transthoracically with 10(9) CFU of S. typhimurium and necropsied at 3 and 18 h p.i. By 3 h p.i., all tissues were positive for S. typhimurium. Tonsil explants seeded with 10(9) CFU of S. typhimurium indicated that within 6 h p.i., S. typhimurium was located within the tonsilar crypts. These data show that after intranasal inoculation, S. typhimurium rapidly appears in the gut tissues and suggest that the tonsils and lung may be important sites for invasion and dissemination of Salmonella species.

Spontaneous equine pulmonary granular cell tumors: morphologic, histochemical, and immunohistochemical characterization

Spontaneous equine pulmonary granular cell tumors were diagnosed in six mature horses at slaughter. These tumors were grossly recognized as multiple (5/6) or single (1/6) creamy white, firm nodules. The tumors, located adjacent to bronchi and bronchioles, often invaded airways, resulting in partial to complete occlusion of the lumina. Neoplastic cells were rounded to polyhedral with numerous eosinophilic cytoplasmic granules that reacted uniformly positive with S-100 and neuron-specific enolase antibodies and multifocally with glial fibrillary acidic protein antibodies. These cells were negative for muscle-specific actin, lysozyme, cytokeratin, chromogranin A, and myelin basic protein antigens and did not stain with silver by the Grimelius technique. Uniformly blue-green and scattered pink intracytoplasmic granules were evident with luxol fast blue and periodic acid-Schiff counterstain for myelin and myelin breakdown products. Histochemical and immunohistochemical staining results of these tumors suggest that they are composed primarily of myelinating Schwann cells with lesser numbers of scattered nonmyelinating Schwann cells. The morphologic features of the equine pulmonary granular cell tumors are strikingly similar to those of endobronchial granular cell tumors of human beings.

Bovine pulmonary blastomas: histomorphologic description and immunohistochemistry

Three adult female dairy cattle with pulmonary blastomas were evaluated. The gross lesions at postmortem were described as multiple white circumscribed masses throughout the lungs, with pleural involvement in one cow and lymph node metastasis in the other two cows. Histologically, the tumors contained a dual population of mesenchymal and epithelial neoplastic cells. Epithelial cells formed nests, tubules, and formations resembling bronchioles of normal lung. Mesenchymal cells were spindle shaped with oval nuclei and fibrillar eosinophilic cytoplasm, were large rounded cells with multiple round nuclei and granular eosinophilic cytoplasm, or appeared blast-like, with large hyperchromatic nuclei and amphophilic cytoplasm. The tumors varied greatly in appearance from one field to another within the same tumor. Epithelial cells stained positively with anticytokeratin antibodies. Some spindle-shaped mesenchymal cells exhibited smooth muscle cell differentiation with positive staining with anti-vimentin, anti-muscle-specific actin, and anti-smooth muscle actin antibodies, whereas other rounded mesenchymal cells expressed striated muscle cell differentiation with multiple nuclei and positivity to anti-neuron-specific enolase and anti-muscle-specific actin antibodies. The variable expression of the intermediate filaments and cytoplasmic enzymes indicates multiple pathways of differentiation in the pulmonary blastomas.

Hepatic protoporphyrin accumulation in a broiler chicken

Hepatocellular accumulation and biliary excretion of protoporphyrin in a 6-week-old chicken are described. The affected liver was grossly dark gray to black. Histologically, hepatocytes, bile canaliculi, and bile-duct lumina contained dark-brown granules. These protoporphyrin pigment accumulations were brightly birefringent under polarized light. The ultrastructural appearance of granules revealed hair-like crystals in a radial arrangement. Extracted levels of protoporphyrin in the affected liver were determined to be 630 micrograms per gram of wet (frozen) liver. Spectrofluorometric scans of liver extracts and sedimented crystals were characteristic of protoporphyrin.

Visceral granulomas in chickens infected with a filamentous bacteria

Visceral granulomas containing gram-positive filamentous bacteria were diagnosed in eight chickens collected from processing plants over a period of 4 years. Formalin-fixed tissues were submitted from the chickens after slaughter, but no specimens suitable for bacterial culture were received. The bacteria lacked similar tinctorial, morphologic, and ultrastructural features of other gram-positive bacteria that have been identified in chickens. The bacteria were visible with hematoxylin and eosin and faintly visible with Gomori methenamine-silver, but negative with periodic acid-Schiff and Fite-Faraco acid-fast stains. Granulomas were found in the liver, spleen, and peritoneum.

Comparative study of colonizing and noncolonizing Campylobacter jejuni

Campylobacter jejuni A74/O and A74/C are congenic strains. An oral dose of 10(5) organisms of strain A74/C colonizes chicken intestines. Strain A74/O, from which A74/C is derived, does not colonize the chicken intestines with an oral dose of 10(5) organisms. In this study, the congenic bacteria were compared to identify possible colonization mechanisms. Differences were not observed in plasmid content or by HindIII, Pst I, Acc I, HincII, Ava I, Ava II, Xba I, and BamHI restriction enzyme digestion of total DNA. Transmission electron microscopy of negatively stained samples revealed no differences between the strains. Sections of cecal tissue from nonfed day-of-hatch chicks were cultured with each strain for 2 hours and then examined by light and electron microscopy. Both strains caused necrosis of villus epithelial cells. Immunofluorescent or silver staining revealed strain A74/C located deep in numerous epithelial crypts, but strain A74/O only was present in one sample mixed with sloughed necrotic cells. Similarly, organisms were detected by transmission electron microscopy deep in crypts in tissues cultured with A74/C, but not A74/O. Cells of A74/C detected in crypts did not appear to associate with epithelial cells. The strains did not differ in chemotactic behavior to mucin or fucose.