Overexpression of phosphoinositide-specific phospholipase Cgamma in NIH 3T3 cells promotes transformation and tumorigenicity

Phosphoinositide-specific phospholipase Cgamma (PLCgamma) is a key regulatory enzyme that binds to the phosphoryl-tyrosine residues in the cytoplasmic domain of certain activated receptors and catalyses the hydrolysis of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] forming IP3 and diacylglycerol (DAG) in response to several mitogenic factors. Previously, we determined that microinjected PLCgamma induces DNA synthesis in G0-arrested NIH 3T3 cells, suggesting the possibility that PLCgamma may have an oncogenic potential. In this report, we demonstrate that overexpression of PLCgamma in NIH 3T3 cells results in altered growth properties and cellular transformation. The PLCgamma/3T3 transfectants do not require serum growth factors to proliferate, display anchorage-independent growth in soft agar and induce tumors when transplanted into nude mice. These findings suggest that overexpression of PLCgamma facilitates the transformation of NIH 3T3 cells. Furthermore, PLCgamma expression and activity have been shown to be elevated in many human tumors. Thus, PLCgamma signaling may contribute to the promotion and/or progression of human cancers.

Necrotizing enteritis as a cause of mortality in Laysan albatross, Diomedea immutabilis, chicks on Midway Atoll, Hawaii

A necropsy survey of Laysan albatross, Diomedea immutabilis, chicks on Midway Atoll in June 1993, 1994, and 1995 revealed 54% (21/39), 67% (49/71), and 93% (15/16), respectively, to have enteritis as the most severe pathologic finding. The lesion was limited to the ileum, ceca, and large intestine. We were unable to attribute a single infectious etiology to this lesion. Many birds with enteritis also exhibited renal lesions similar to those encountered in chickens experimentally deprived of water. We propose that enteritis is a significant cause of mortality in Laysan albatross chicks on Midway and that it may be a sequela to dehydration. It is likely that the pathology of dehydration in Laysan albatross differs from that in chickens largely because of diet.

Interaction between the sodium channel inactivation linker and domain III S4-S5

The III-IV linker (L(III-IV)) of the rat brain sodium channel is critical for fast inactivation, possibly forming a fast inactivation particle. Inactivation can be disrupted by mutation of a conserved alanine at position 1329 in the S4-S5 loop of domain III. Combination of a charged mutation at 1329 with a compensatory (opposite) charge mutation at position 1489 in L(III-IV) partially restores inactivation of the channel. The compensatory charge mutant channel has a single-channel mean open time that is similar to that of the wild-type channel and is approximately 50 times shorter than that of the L(III-IV) mutant channel. The results of thermodynamic cycle analysis indicate that the mutations in domain III S4-S5 and L(III-IV) have a coupling energy of 2.8 kcal/mol, indicating that the two mutations act interdependently. These data suggest that L(III-IV) interacts directly with A1329, which may form part of the docking site if L(III-IV) is a fast inactivation particle.

TIMP-3 induces cell death by stabilizing TNF-alpha receptors on the surface of human colon carcinoma cells

Matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) regulate the structural integrity of the extracellular matrix (ECM). Constitutive expression of human TIMP-3 in human DLD colon carcinoma cells renewed serum-responses and inhibited tumour formation in nude mice. To elucidate the mechanism of TIMP-3-mediated tumour suppression, we compared parental DLD and TIMP-3 expressing DLD cells (TIMP-3/DLD), finding them to be significantly different. TIMP-3/DLD cultures have fewer mitotic cells, are delayed in G1, and die after serum starvation. TIMP-3/DLD conditioned media activates cell death on fibroblast cells. The cell death induced by serum starvation and conditioned media was inhibited by 70%, in the presence of neutralizing tumour necrosis factor alpha (TNF-alpha) antibody. TIMP-3/DLD whole cell lysate contained p55 TNF-alpha receptor, while vector/DLD lysate had p55 TNF-alpha receptor and p46 soluble TNF-alpha inhibitor. Vector/DLD conditioned media had p46, while no soluble TNF-alpha receptor was detected in TIMP-3/DLD conditioned media. In addition, FACS analysis revealed that TIMP-3/DLD cells have more TNF-alpha surface binding sites, suggesting a direct correlation between TIMP-3 expression and surface receptors. The mechanism of tumorigenic reversion induced by TIMP-3 in DLD cells may involve protection of receptors from the proteolytic activity of MMPs. Putative TIMP-3-mediated inhibition of MMPs restores the TNF-alpha p55 signalling pathway and the carcinoma cell is killed by autocrine TNF-alpha. Thus, DLD cells have specific ECM MMPs that cleave cytokines and cytokine receptors. TIMP-3 specifically inhibits MMPs involved in receptor shedding.

IL-7 activates alpha4beta1 integrin in murine thymocytes

IL-7, a cytokine produced by thymic epithelium, was shown to induce adhesion of murine thymocytes to gelatin-coated membranes. A major binding component of gelatin was identified as fibronectin. IL-7-induced adhesion was observed for all of the major thymocyte subsets, including double-negative, double-positive, and single-positive cells, and specific IL-7R were verified on each subset. Fibronectin binding was mediated via alpha4beta1 integrin (VLA-4), which is expressed at high levels on thymocytes. VLA-4 surface expression was not increased following IL-7 treatment, but was shown to undergo rapid tyrosine phosphorylation on the beta1 subunit. This tyrosine phosphorylation was blocked by genistein, which also blocked IL-7-induced adhesion. IL-7 was detected on the extracellular matrix of the thymus, suggesting that it could promote matrix association through an integrin pathway.

Genetic determinant of rapid-onset B-cell lymphoma by avian leukosis virus

Infection of 10 day-old chicken embryos with the recombinant avian leukosis virus (ALV) EU-8 induces a high incidence of rapid-onset B-cell lymphoma by insertional activation of the c-myb gene. LR-9, a related ALV with differences from EU-8 in the gag and pol genes, induces rapid-onset lymphoma at only a low incidence. To localize the viral determinant(s) responsible for this biologic difference, we constructed and tested a series of reciprocal chimeras between EU-8 and LR-9 ALVs. The ability to induce rapid-onset lymphoma efficiently was localized to a 925-nucleotide (nt) region of the EU-8 gag gene. Sequence analysis of the region revealed a 42-nt deletion in EU-8 relative to LR-9, as well as some single-nucleotide changes. A mutant virus, delta LR-9, constructed by deleting these 42 nt from LR-9, also induced rapid-onset lymphoma at a high frequency, confirming the biologic significance of this deletion. This deletion removed nt 735 to 776, which lies within a cis-acting RNA element that negatively regulates splicing (NRS). The deletion was shown to cause an increase in splicing efficiency, which may lead to increased production of a truncated myb gene product from an ALV-myb readthrough RNA.

IL-7 activates alpha4beta1 integrin in murine thymocytes

IL-7, a cytokine produced by thymic epithelium, was shown to induce adhesion of murine thymocytes to gelatin-coated membranes. A major binding component of gelatin was identified as fibronectin. IL-7-induced adhesion was observed for all of the major thymocyte subsets, including double-negative, double-positive, and single-positive cells, and specific IL-7R were verified on each subset. Fibronectin binding was mediated via alpha4beta1 integrin (VLA-4), which is expressed at high levels on thymocytes. VLA-4 surface expression was not increased following IL-7 treatment, but was shown to undergo rapid tyrosine phosphorylation on the beta1 subunit. This tyrosine phosphorylation was blocked by genistein, which also blocked IL-7-induced adhesion. IL-7 was detected on the extracellular matrix of the thymus, suggesting that it could promote matrix association through an integrin pathway.

The value of transformed lymphocyte count in subclassification of non-Hodgkin's lymphoma by fine-needle aspiration

No established criteria exist for predicting lymphoma grade or transformation in cytologic material. We counted transformed lymphocytes in fine-needle aspiration (FNA) biopsy specimens to determine whether the percentage of these cells in the smear could predict the histologic grade, the biologic behavior, or both. The percentage of transformed lymphocytes out of total lymphoid cells was determined on Papanicolaou-stained smears. Afterward, a cytodiagnosis was based on clinical information available at the time of the FNA, cytomorphologic data, and flow cytometry data. Results were correlated with results of examination of the surgical biopsy specimen, clinical behavior of the lymphoma, or both. The percentage of transformed lymphocytes was 10% or less in all low-grade or indolent lymphomas. Aspirates with transformed lymphocyte counts of 20% or greater were aggressive lymphomas. We also report our experience in the diagnosis of non-Hodgkin's lymphoma by FNA using cytomorphologic examination and immunophenotyping by flow cytometry at a cancer referral hospital. This is a preliminary study, and larger series may help establish the ranges of transformed lymphocyte counts that correlate with the lymphoma subtype.

Colposacropexy: an alternative technique

Colposacropexy procedures restore anatomically correct apical vaginal support on the levator plate at the ischial spine level. Venous hemorrhage resulting from laceration of presacral veins during suture fixation is the major hazard of this procedure. Titanium orthopedic bone anchor fixation minimizes this risk through precision placement of the bone anchor-suture unit.

Microinjected cDNA encoding JAK2 protein-tyrosine kinase induces DNA synthesis in NIH 3T3 cells

Microinjection of expression plasmids encoding either JAK2 or hyperactive (Ndelta661)rJAK2 into serum-starved NIH 3T3 cells resulted in 20-30-fold induction of DNA synthesis. Control microinjections of buffer or parental pcDNA3 vector resulted in only 3-5-fold induction of DNA synthesis. Induction of DNA synthesis was blocked when plasmid encoding JAK2 was microinjected in the presence of the JAK2-selective inhibitor AG-490, whereas AG-490 did not block DNA synthesis induced by microinjected plasmid encoding (Ndelta661)rJAK2. The ability of JAK2 to initiate the G(o)/S cell cycle transition is comparable to that of other proto-oncogenes, and supports a mechanistic role for overexpressed Janus kinases in carcinogenesis.

Malignant transformation of mammalian cells initiated by constitutive expression of the polo-like kinase

Polo-like kinase (Plk) is the mammalian homologue of the Drosophila polo and Saccharomyces cerevisiae CDC5 genes, which are thought to be involved in regulating chromosomal segregation. Previously, we showed that transient ectopic expression of Plk could induce DNA synthesis in quiescent NIH 3T3 cells, suggesting that Plk might also have a function during G1 or S phase. Here we report that microinjection of Plk mRNA is sufficient to drive quiescent cells into mitosis and that constitutive expression of Plk in NIH 3T3 cells causes oncogenic focus formation. These transformed cells grow in soft agar and form tumors in nude mice. Because Plk expression has been shown to be high in various human tumors, we suggest that Plk may contribute to the promotion and/or progression of human cancers.

Rapid induction of B-cell lymphomas by avian leukosis virus

Avian leukosis viruses (ALVs) that induce rapid B-cell lymphomas integrate into the c-myb gene and produce an ALV-myb read-through RNA, which is spliced to produce a truncated Myb protein. The genetic determinants of such recombinant ALVs have been mapped to a 42-nt deletion within the gag gene. This deletion increases splicing efficiency since it is located within a negative regulator of splicing. We propose that the deletion leads to increased production of Myb protein by increasing splicing of an ALV-myb pre-mRNA.

Leuconostoc mesenteroides B-1355 Mutants Producing Alternansucrases Exhibiting Decreases in Apparent Molecular Mass

Mutants of Leuconostoc mesenteroides B-1355 exhibiting decreases in the apparent molecular mass of alternansucrase on sodium dodecyl sulfate (SDS)-polyacrylamide gels stained for enzyme activity were isolated after mutagenizing strain R15 with N-methyl-N(prm1)-nitro-N-nitrosoguanidine. Strain R15 was a UV mutant of strain B-1355 which was enriched for production of alternansucrase. All strains produced principal and minor alternansucrase bands on SDS gels when cultures were subjected to SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The patterns of the principal and minor activity bands on our SDS gels did not result from dextran-enzyme complexes, because mutants constitutive for synthesis of glucosyltransferases (GTFs) on sugars other than sucrose produced activity bands after growth in glucose medium that were the same as those produced after growth in sucrose medium. Dextransucrase, which had been inactivated by heating at 45(deg)C, was reactivated when subjected to SDS-PAGE, showing that our SDS-PAGE conditions were reversibly denaturing. Thermal denaturation at 45(deg)C did not involve a dispersal of GTFs into subunits. Densitometry measurements showed a roughly linear relationship between enzyme activity and band intensity over a loading range of 0.2 to 0.8 mU per sample well. We concluded that SDS-PAGE followed by activity staining was a reliable method for estimating numbers and ratios of GTFs produced by Leuconostoc sp. in media containing sucrose.

[Superior vena cava and right atrium thrombosis successfully treated with streptokinase]

The case of a 56 year-old male with acute lymphoid leukemia and no signs of activity for the last four months is reported. He presented with superior vena cava thrombosis caused by a Hickman catheter, and had positive blood cultures for Candida albicans and Staphylococcus epidermidis. Despite adequate antimicrobial therapy, the fever persisted, and the patient was submitted to surgical thrombectomy. One week following the procedure, the fever returned, and thrombosis of the superior vena cava extending to the right atrium was identified by transesophageal echocardiography (TEE). The patient underwent thrombolytic therapy with streptokinase, and no thrombus could be identified in the control TEE. No hemorrhagic or thromboembolic complication occurred. The patient was discharged with oral anticoagulation.

The efficacy of protoporphyrin as a predictive biomarker for lead exposure in canvasback ducks: Effect of sample storage time

We used 363 blood samples collected from wild canvasback dueks (Aythya valisineria) at Catahoula Lake, Louisiana, U.S.A. to evaluate the effect of sample storage time on the efficacy of erythrocytic protoporphyrin as an indicator of lead exposure. The protoporphyrin concentration of each sample was determined by hematofluorometry within 5 min of blood collection and after refrigeration at 4 °C for 24 and 48 h. All samples were analyzed for lead by atomic absorption spectrophotometry. Based on a blood lead concentration of ≥0.2 ppm wet weight as positive evidence for lead exposure, the protoporphyrin technique resulted in overall error rates of 29%, 20%, and 19% and false negative error rates of 47%, 29% and 25% when hematofluorometric determinations were made on blood at 5 min, 24 h, and 48 h, respectively. False positive error rates were less than 10% for all three measurement times. The accuracy of the 24-h erythrocytic protoporphyrin classification of blood samples as positive or negative for lead exposure was significantly greater than the 5-min classification, but no improvement in accuracy was gained when samples were tested at 48 h. The false negative errors were probably due, at least in part, to the lag time between lead exposure and the increase of blood protoporphyrin concentrations. False negatives resulted in an underestimation of the true number of canvasbacks exposed to lead, indicating that hematofluorometry provides a conservative estimate of lead exposure.

A missense mutation in the sodium channel Scn8a is responsible for cerebellar ataxia in the mouse mutant jolting

The voltage-gated sodium channel Scn8a is broadly distributed in brain and spinal cord. We have identified a missense mutation in Scn8a that is associated with cerebellar ataxia in the jolting mutant, a mild allele of the "motor endplate disease" locus. The jolting mutation results in substitution of Thr for an evolutionarily conserved Ala residue in the cytoplasmic S4-S5 linker of domain III. Introduction of the corresponding mutation into the rat brain IIA sodium channel shifted the voltage dependence of activation by 14 mV in the depolarizing direction, without affecting the kinetics of fast inactivation or recovery from inactivation. A shift in the threshold of the Scn8a channel could account for the reduced spontaneous activity of Purkinje cells, reduced inhibitory output from the cerebellum, and loss of motor control observed in jolting mice.

Suppression of in vivo tumor growth and induction of suspension cell death by tissue inhibitor of metalloproteinases (TIMP)-3

Tissue inhibitor of metalloproteinases-3(TIMP-3), a novel member of TIMP family genes, has been recently cloned and shown to be expressed in preneoplastic but not in neoplastic mouse JB6 epidermal cells (Sun et al. 1994 Cancer Res., 54, 11139). This down regulation of the gene appears to be attributable at least in part to alteration of gene methylation (Sun et al. 1995 J. Biol. Chem., 270, 19312). Little is known, however, about the role of TIMP-3 in human cancers. We screened several human tumor cell lines for TIMP-3 expression and found that a colon carcinoma line, DLD-1, did not express TIMP-3. If down regulation of TIMP-3 is causally related to carcinogenesis, re-expression by transfection may reverse the tumor cell phenotype. We therefore overexpressed human TIMP-3 in DLD-1 cells. TIMP-3 transfectants showed a serum-dependent growth inhibition in monolayer culture and a decreased growth potential in nude mice in a manner dependent on the level of TIMP-3 expression. A transfectant expressing a high level of active hTIMP-3 completely lost the ability to form tumors following s.c. injection into nude mice. We also tested TIMP-3 expressing cells and neocontrol TIMP-3 negative cells for their ability to grow in liquid suspension culture, since both cells grew in semi-solid soft agar. As compared to neocontrol cells, TIMP-3 overexpressors formed large aggregates, followed by cell death. This effect was not mimicked by BB94, a broad MMP inhibitor. We conclude from this study that (i) TIMP-3 overexpression in human colon carcinoma cells induces growth arrest in low serum conditions and inhibits in vivo tumor growth and (ii) the TIMP-3-induced large aggregate formation and subsequent cell death under suspension growth cannot be explained by its MMP inhibitory activity.

Mammalian evolution and the interphotoreceptor retinoid binding protein (IRBP) gene: convincing evidence for several superordinal clades

Phylogenetic relationships of 25 mammalian species representing 17 of the 18 eutherian orders were examined using DNA sequences from a 1.2-kb region of the 5' end of exon 1 of the single-copy nuclear gene known as interphotoreceptor retinoid binding protein (IRBP). A wide variety of methods of analysis of the DNA sequence, and of the translated products, all supported a five-order clade consisting of elephant shrew (Macroscelidea)/aardvark (Tubulidentata)/and the paenungulates (hyracoids, sirenians, and elephants), with bootstrap support in all cases of 100%. The Paenungulata was also strongly supported by these IRBP data. In the majority of analyses this monophyletic five-order grouping was the first branch off the tree after the Edentata. These results are highly congruent with two other recent sources of molecular data. Another superordinal grouping, with similar 100% bootstrap support in all of the same wide-ranging types of analyses, was Artiodactyla/Cetacea. Other superordinal affinities, suggested by the analyses, but with less convincing support, included a Perissodactyla/Artiodactyla/Cetacea clade, an Insectivora/Chiroptera clade, and Glires (an association of rodents and lagomorphs).

A bacterial invasin induces macrophage apoptosis by binding directly to ICE

Shigella, the etiological agent of dysentery, kills macrophages by inducing apoptosis. Deletion mutants in the invasion invasion plasmid antigen B (ipaB) of Shigella flexneri are not cytotoxic. Here, we localized IpaB to the cytoplasm of macrophages infected with S. flexneri. Purified IpaB induced apoptosis when microinjected into macrophages, indicating that IpaB is sufficient to induce apoptosis. Using a GST-IpaB fusion protein as a ligand in affinity purification, we isolated four IpaB binding proteins from macrophages which were identified as the precursor and the mature polypeptides of interleukin-1beta converting enzyme (ICE) or a highly homologous protease. We found that IpaB binds directly to ICE and this enzyme is activated during S. flexneri infection. Furthermore, specific inhibitors of ICE prevented Shigella-induced apoptosis.

Lead exposure in Laysan albatross adults and chicks in Hawaii: prevalence, risk factors, and biochemical effects

Prevalence of lead exposure and elevated tissue lead was determined in Laysan albatross (Diomedea immutabilis) in Hawaii. The relationship between lead exposure and proximity to buildings, between elevated blood lead and droopwing status, and elevated liver lead and presence of lead-containing paint chips in the proventriculus in albatross chicks was also examined. Finally, the effects of lead on the enzyme delta-aminolevulinic acid dehydratase (ALAD) was determined. There was a significant association between lead exposure or elevated tissue lead and proximity to buildings in albatross chicks and presence of lead paint chips in the proventriculus and elevated liver lead in carcasses. Although there was a significant association between elevated blood lead and droopwing chicks, there were notable exceptions. Prevalence of elevated tissue lead in albatross chicks was highest on Sand Island Midway and much less so on Kauai and virtually nonexistent in other areas. Prevalence of lead exposure decreased as numbers of buildings to which chicks were exposed on a given island decreased. Laysan albatross adults had minimal to no lead exposure. There was a significant negative correlation between blood lead concentration and ALAD activity in chicks. Based on ALAD activity, 0.03-0.05 microg/ml was the no effect range for blood lead in albatross chicks.

PLC gamma 1 Src homology domain induces mitogenesis in quiescent NIH 3T3 fibroblasts

Previously, we demonstrated that microinjection of phosphoinositide-specific phospholipase C gamma 1 (PLC gamma 1) and lipase-defective mutants of PLC gamma 1 induced G(0) growth arrested NIH 3T3 fibroblasts to enter S phase of the cell cycle. These experiments suggested that regions other than the catalytic domain of PLC gamma 1 may be responsible for inducing mitogenesis. To test other regions of PLC gamma 1 for DNA synthesis inducing activity, cDNA fragments encoding Src homology (SH) and pleckstrin homology (PH) domains were subcloned into the bacterial expression plasmid pGEX-2TK, and the GST fusion proteins were purified. The complete PLC gamma l SH domain peptide was found to induce DNA synthesis after microinjection into growth arrested fibroblasts. Peptides containing a single SH3 domain or two SH2 domains induced a partial response that was restored to full activity if they were co-injected. The PH domain peptide did not induce DNA synthesis. Thus, both SH3 and SH2 activity combine to give maximum DNA synthesis induction, demonstrating that non-catalytic structural domains of PLC gamma 1 have pronounced effects on mitogenic signaling pathways.

Thymosin alpha 1 does not promote growth or oncogenic transformation

Thymosin alpha 1 (T alpha 1) is an immune modulatory peptide which has been evaluated in a variety of clinical trials. Although no in vivo adverse effects, including enhancement of tumor growth, have been noted, in vitro studies suggesting a role for T alpha 1 in cell growth have been reported. The studies presented in this report evaluated both exogenously added T alpha 1 and endogenously expressed T alpha 1 as factors which could either promote growth of tumor cells or induce transformation. No effect of exogenous T alpha 1 on cell growth was found. NIH-3T3 cells transfected with cDNA for the precursor ProThymosin alpha (Pro T alpha) expressed elevated levels of authentic T alpha 1 but did not demonstrate either enhanced proliferation in liquid culture or transformation as defined by the loss of contact inhibition or anchorage independent growth in soft agar. Thus these studies argue against the hypothesis that T alpha 1 is either an intracellular or extracellular growth promoter.

Hematology for primary care physicians

Many hematologic disorders present minimal physical signs and symptoms in the early state. For example, chronic myelogenous leukemia may not manifest splenomegaly or any obvious physical signs, yet the laboratory report may demonstrate leukocytosis, eosinophilia, basophilia, and thrombocytosis. Although the anemic condition of a patient with a hemoglobin level of 7 gm/dl may be readily apparent to the clinician, a hemoglobin level of 10.5 gm/dl may be difficult to discern during a brief visit that is focused on another organ system. The same laboratory report, however, may contain valuable clues about unsuspected anemia related to mean corpuscular volume or morphology. Information from supporting chemistry studies often may be helpful in interpretation of the diagnosis. An elevated uric acid level, for example, may indicate hyperkinetic cytogenesis related to myeloproliferative or lymphoproliferative neoplastic disorders. This monograph is designed to be useful to busy physicians who want to use basic hematologic studies in a cost-effective manner. Hematology is viewed in a problem-oriented way; the laboratory report is used as the problem generator.

Clonal evolution of chronic lymphocytic leukemia to acute lymphoblastic leukemia

A 38-year-old white man was diagnosed with B-cell chronic lymphocytic/prolymphocytic leukemia (CLL/PLL). The disease was unresponsive to a variety of chemotherapeutic regimes. One year after diagnosis, L3 blasts appeared in peripheral blood associated with more aggressive course. There was no change in the B-cell phenotype at that time, but cytogenetic analysis revealed the appearance of t(8;22)(q24;q11) and -21 superimposed on the original karyotype: 46,XY,+3,der(3)t(3;17)(p11;q12), t(11;14)(q13;q32),-17. These results indicate that the lymphoblastic transformation in our case emerged from the pre-existing B-lymphocytic clone.