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Grb2-associated binder 1 polymorphism was associated with the risk of Helicobactor pylori infection and gastric atrophy.

BACKGROUND: Various single nucleotide polymorphisms (SNPs) have explained the association between Helicobacter pylori (H. pylori) and gastric atrophy and cancer. This study investigated the associations of Grb2 associated binder 1 (Gab1) polymorphism and the combination of PTPN11 gene encoding src homology 2 domain-containing protein tyrosine phosphatase-2 (SHP2) and Gab1 gene with gastric cancer and gastric atrophy among H. pylori seropositive subjects. METHODS: A single nucleotide polymorphism at intron 2 of Gab1 (JST164345) was examined for 454 Japanese health checkup examinees (126 males and 328 females) aged 35 to 85 without a history of gastric cancer and 202 gastric cancer patients (134 males and 68 females) aged 33 to 94 with pathologically confirmed diagnosis of gastric adenocarcinoma. RESULTS: The decreased OR of the Gab1 A/A for H. pylori seropositivity was 0.25 (95% confidence interval (CI): 0.08-0.71). Among seropositive healthy controls, the OR of the Gab1 G/A+A/A for gastric atrophy was significant (OR=1.95, 95% CI: 1.12 -3.40). Seropositive individuals with PTPN11 G/G and Gab1 G/A+A/A demonstrated the highest risk of gastric atrophy with significance (OR=3.49, 95% CI: 1.54-7.90) relative to PTPN11 G/A+A/A and Gab1 G/G, the lowest risk combination, as a reference. However, the gene-gene interaction between PTPN11 and Gab1 was not observed (OR=1.39, 95% CI: 0.41-4.66). Compared to gastric cancer case, the Gab1 did not influence the step of atrophy/metaplasia-gastric cancer sequence. CONCLUSIONS: This study represents that the Gab1 polymorphism was associated with the low risk of H. pylori infection and the high risk of gastric atrophy among seropositive healthy controls, and that seropositive individuals with PTPN11 G/G and Gab1 G/A+G/G were associated with the greatest risk of gastric atrophy. These findings require confirmation in much larger studies.

Adaptor Proteins, Signal Transducing↗

Reactivation of host-dependent src kinase activity by co-expression with a heterologous tyrosine kinase.

XD4 is a host range deletion mutant (delta 77-225) of the v-src transforming gene. This mutant transforms chicken embryo fibroblasts (CEF) but not Rat-2 cells. It encodes a product (XD4-src) that is phosphorylated at tyrosine and active as a tyrosine kinase in CEF, but is neither phosphorylated at tyrosine nor active as a kinase in Rat-2 cells. We report here that the XD4-src kinase activity in Rat-2 cells can be restored by co-expression with the tyrosine kinase encoded by v-fps, but not by co-expression with activated Ha-ras. Mutation of the major tyrosine autophosphorylation site (Y416) in XD4-src reduced but did not abolish the reactivation of XD4 tyrosine phosphorylation and kinase activity by v-fps. These results suggest that deletion of the SH2 and SH3 domains renders v-src kinase activity dependent on tyrosine phosphorylation at Y416 and other sites. The reactivation of XD4-src may result either from direct phosphorylation by the v-fps gene product or may be an indirect consequence of v-fps expression.

Animals↗

Absence of the steroid receptor coactivator-3 induces B-cell lymphoma.

Steroid receptor coactivator 3 (SRC-3/ACTR/AIB-1/pCIP/RAC3/TRAM-1) is a member of the p160 family of nuclear receptor coactivators that plays an important role in mammary gland growth, development, and tumorigenesis. We show that deletion of SRC-3 gene decreases platelet and increases lymphocytes numbers, leading to the development of malignant B-cell lymphomas upon aging. The expansion of the lymphoid lineage in SRC-3(-/-) mice is cell autonomous, correlates with an induction of proliferative and antiapoptotic genes secondary to constitutive NF-kappaB activation, and can be reversed by restoration of SRC-3 expression. NF-kappaB activation is explained by the degradation of IkappaB, consequent to increases in free IkappaB kinase, which is no longer inhibited by SRC-3. These results demonstrate that SRC-3 regulates lymphopoiesis and in combination with previous studies indicate that SRC-3 has vastly diverging effects on cell proliferation depending on the cellular context, ranging from proliferative and tumorigenic (breast) to antiproliferative (lymphoid cells) effects.

Animals↗

Expression of v-src and chicken c-src in rat cells demonstrates qualitative differences between pp60v-src and pp60c-src.

The retroviral oncogene v-src arose by transduction of the cellular gene c-src. The similarity between these genes raised the possibility that c-src might be able to elicit neoplastic growth. We explored this by constructing a chimeric plasmid that allows the expression of chicken c-src. A rat cell line containing ten times the normal intracellular level of pp60c -src was isolated after transfecting rat-2 cells with the chimeric DNA. These cells produce the protein encoded by c-src ( pp60c -src) in quantities at least three times greater than required to achieve transformation by the product of v-src ( pp60v -src). The cells remain phenotypically normal, contain actin cables, and do not grow in soft agar. However, transfection of the cell line containing elevated cells of pp60c -src or Rat-2 cells with a molecular clone of v-src produces cells that exhibit properties of biologically transformed cells: round morphology, disrupted actin cables, and ability to grow in soft agar.

Actins↗

Transduction of a cellular oncogene: the genesis of Rous sarcoma virus.

The oncogene of Rous sarcoma virus (v-src) arose by transduction of a cellular gene (c-src). In an effort to explore the mechanism of transduction, we have identified the splice acceptor site used in the genesis of mRNA for v-src, shown that an equivalent site is used in the splicing of mRNA for c-src, and determined the nucleotide sequence from the boundaries of homology between v-src and c-src. Our data indicate that (i) only a portion of c-src is represented within v-src, (ii) the leftward recombination between the genome of the transducing virus and c-src occurred in an intron of the cellular gene, (iii) v-src is in part a spliced version of the corresponding portion of c-src, and (iv) nucleotide sequences represented once in the genome of the transducing virus become duplicated to flank v-src. These findings indicate that the first step in transduction is probably recombination between DNA forms of the transducing viral genome and c-src and otherwise support the prevailing model for transduction by retroviruses. The carboxyl termini of the proteins encoded by v-src and c-src differ appreciably. An unidentified domain of 127 or 128 nucleotides is located at different positions in the genomes of two strains of RSV and gives evidence of being a foreign element that entered the viral genomes by genetic transposition independent of the transduction of src.

Amino Acid Sequence↗

Myeloproliferative disease induced by TEL-PDGFRB displays dynamic range sensitivity to Stat5 gene dosage.

Expression of the constitutively activated TEL/PDGFbetaR fusion protein is associated with the t(5;12)(q33;p13) chromosomal translocation found in a subset of patients with chronic myelomonocytic leukemia. TEL/PDGFbetaR activates multiple signal transduction pathways in cell-culture systems, and expression of the TEL-PDGFRB fusion gene induces myeloproliferative disease (MPD) in mice. We used gene-targeted mice to characterize the contribution of signal transducer and activator of transcription (Stat) and Src family genes to TEL-PDGFRB-mediated transformation in methylcellulose colony and murine bone marrow transduction/transplantation assays. Fetal liver hematopoietic stem and progenitor cells harboring targeted deletion of both Stat5a and Stat5b (Stat5ab(null/null)) genes were refractory to transformation by TEL-PDGFRB in methylcellulose colony assays. Notably, these cell populations were maintained in Stat5ab(null/null) fetal livers and succumbed to transformation by c-Myc. Surprisingly, targeted disruption of either Stat5a or Stat5b alone also impaired TEL-PDGFRB-mediated transformation. Survival of TPiGFP-->Stat5a(-/-) and TPiGFP-->Stat5a(+/-) mice was significantly prolonged, demonstrating significant sensitivity of TEL-PDGFRB-induced MPD to the dosage of Stat5a. TEL-PDGFRB-mediated MPD was incompletely penetrant in TPiGFP-->Stat5b(-/-) mice. In contrast, Src family kinases Lyn, Hck, and Fgr and the Stat family member Stat1 were dispensable for TEL-PDGFRB disease. Together, these data demonstrate that Stat5a and Stat5b are dose-limiting mediators of TEL-PDGFRB-induced myeloproliferation.

Animals↗

Oncogenes as inducers of tumor angiogenesis.

Dominantly acting transforming oncogenes are generally considered to contribute to tumor development and progression by their direct effects on tumor cell proliferation and differentiation. However, the growth of solid tumors beyond 1-2 mm in diameter requires the induction and maintenance of a tumor blood vessel supply, which is attributed in large part to the production of angiogenesis promoting growth factors by tumor cells. The mechanisms which govern the expression of angiogenesis growth factors in tumor cells are largely unknown, but dominantly acting oncogenes may have a much greater impact than hitherto realized. An example of this is the induction of expression of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) by mutant H- or K-ras oncogenes, as well as v-src and v-raf, in transformed fibroblasts or epithelial cells. Besides VEGF/VPF, mutant ras genes are known to upregulate the expression of a variety of other growth factors thought to have direct or indirect stimulating effects on angiogenesis, e.g. TGF-beta and TGF-alpha. This effect may be mediated through the ras-raf-MAP kinase signal transduction pathway, resulting in activation of transcription factors such as AP1, which can then bind to relevant sites in the promoter regions of genes encoding angiogenesis growth factors. In principle, similar events could take place after activation or overexpression of many other oncogenes, especially those which can mediate their function through ras-dependent signal transduction pathways. The regulatory effect of oncogenes on mediators of angiogenesis has some potentially important therapeutic consequences. For example, it strengthens the rationale of pharmacologically targeting oncogene products, such as mutant RAS proteins, as an anti-tumor therapeutic strategy. Such drugs may attack the source of one or more angiogenic growth factors and by doing so, function, at least in part, as anti-angiogenic agents in vivo.

Genes, Tumor Suppressor↗

Cloning of FRK, a novel human intracellular SRC-like tyrosine kinase-encoding gene.

We report the cloning of a novel tyrosine kinase (TyK)-encoding gene (TYK) from the human hepatoma cell line Hep3B. Using the polymerase chain reaction (PCR) and oligodeoxyribonucleotide primers based on conserved TYK motifs, a 180-bp fragment was cloned and used to obtain full-length cDNA clones of 2.9 kb, with an open reading frame of 505 amino acids (aa). Restricted expression was detected by Northern blotting or reverse-transcribed PCR in a broad range of cell lines. The predicted aa sequence contains characteristic TyK motifs without a transmembrane region, suggesting an intracellular localization. There was 49% aa sequence identity with human FYN product and 47% with human SRC product; however, several structural differences distinguish this clone from other SRC subfamily members. This clone, FYN-related kinase or FRK, is a novel member of the intracellular TYK gene family.

Amino Acid Sequence↗

[Molecular analysis of relationship between oncogene (N-myc and c-src) expression and major histocompatibility complex antigen gene expression in mouse neuroblastoma lines].

The authors have investigated the relationship between oncogene (N-myc and c-src) expression and major histocompatibility complex (H-2 in the mouse) antigen gene expression at the molecular levels, by using mouse neuroblastoma sublines (NB-1 and NB-V). Fluorescence-activated cell sorter analysis showed that NB-1 cells exhibited positive expression to H-2 Kk, H-2 Dd, and beta-2-microglobulin, while NB-V cells were negative to all three antigens. It was found that dimethyl sulfoxide (DMSO) had a capacity to increase an H-2 class I antigen expression on NB-1 cells, whereas no change was observed on NB-V cells after DMSO treatment. Molecular analysis with deoxyribonucleic and ribonucleic acid (RNA) blot hybridization and immunoprecipitation revealed that the enhancement of H-2 antigen expression on NB-1 cells was modulated at the transcriptional control of the H-2 gene. In contrast, negative H-2 antigen expression on NB-V cells was caused by block at the level of glycosylation of the H-2 heavy chain, although an increase in messenger RNA of the H-2 gene was induced after DMSO treatment. There was neither amplification nor rearrangement of N-myc and c-src oncogenes in either neuroblastoma subline. Nuclear run-on transcription assay revealed that the N-myc gene was post-transcriptionally down-modulated by DMSO, whereas the c-src gene was transcriptionally up-regulated. It was thus suspected that N-myc and c-src might be directly associated with cellular proliferation and differentiation in neuronal tumors and that in vivo tumorigenicity could be regulated by the control mechanism of oncogene expression in relation to H-2 gene expression on tumor cells.

Animals↗

SH2-containing phosphotyrosine phosphatase as a target of protein-tyrosine kinases.

A mouse phosphotyrosine phosphatase containing two Src homology 2 (SH2) domains, Syp, was identified. Syp bound to autophosphorylated epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) receptors through its SH2 domains and was rapidly phosphorylated on tyrosine in PDGF- and EGF-stimulated cells. Furthermore, Syp was constitutively phosphorylated on tyrosine in cells transformed by v-src. This mammalian phosphatase is most closely related, especially in its SH2 domains, to the corkscrew (csw) gene product of Drosophila, which is required for signal transduction downstream of the Torso receptor tyrosine kinase. The Syp gene is widely expressed throughout embryonic mouse development and in adult tissues. Thus, Syp may function in mammalian embryonic development and as a common target of both receptor and nonreceptor tyrosine kinases.

Amino Acid Sequence↗

A branched signaling pathway for nerve growth factor is revealed by Src-, Ras-, and Raf-mediated gene inductions.

A myriad of gene induction events underlie nerve growth factor (NGF)-induced differentiation of PC12 cells. To dissect the signal transduction pathways which lead to NGF actions, we have assessed the relative roles of NGF receptor, Src, Ras, and Raf activities in mediating specific gene inductions. We have used the PC12 cell line as well as sublines which inducibly express activated forms of either Src, Ras, or Raf or a dominant inhibitory form of Ras (p21N17 Ras) to study the expression of multiple NGF-inducible mRNAs. The NGF induction of NGFI-A, transin, and VGF mRNAs was mimicked by activated forms of Src, Ras, or Raf and was blocked by p21N17 Ras. The NGF induction of SCG10 mRNA was mimicked only by activated Src and Ras and was blocked by p21N17 Ras, while the induction of Thy-1 mRNA was mimicked only by activated Src and was not blocked by p21N17 Ras. The NGF induction of mRNAs for two sodium channel types was neither mimicked by any activated oncoprotein nor blocked by p21N17 Ras. From these and previous results, we suggest a model in which a linear order of NGF receptor, Src, Ras, and Raf activities is used by NGF to elicit gene inductions. These signaling components define branchpoints in the pathway to specific gene induction events, providing a mechanism for generating a host of diverse NGF actions.

Animals↗

Cells in vivo and in vitro from osteopetrotic mice homozygous for c-src disruption show suppression of synthesis of osteopontin, a multifunctional extracellular matrix protein.

Mice carrying homozygous disruption of the c-src proto-oncogene (Src-/-) develop osteopetrosis due to an impaired ability of osteoclasts to adhere to the bone surface and/or to form bone-resorbing ruffled border. It has also been reported that osteopontin (OPN), a secreted phosphoprotein, mediates osteoclast adherence to the bone matrix. We report here that cells from Src-/- mice, both in vitro and in vivo, express OPN mRNA and protein at a significantly reduced level as compared to cells from Src+/- and +/+ animals, suggesting a potential role for the proto-oncogene c-src in the regulation of OPN gene expression. Our data also show that OPN gene expression can be induced by treatment of SR-/- cells with epidermal growth factor (EGF) and 12-O-tetradecanoyl phorbol-13-acetate (TPA). Results obtained from studies using inhibitors of receptor tyrosine kinases (RTKs) and protein kinase C (PKC) suggest that PKC and RTK are positioned in a pathway with PKC as the downstream effector for the EGF-induced OPN gene expression in SRC-/- cells, and that pp60c-src and EGF may regulate OPN gene expression through a common signalling pathway. Furthermore, contrary to published reports, our study shows that EGF-mediated cell signalling does not require functional interaction between the EGF-receptor and pp60c-src.

3T3 Cells↗

A rapid and cost-effective screening method for identification of targeted embryonic stem cells.

Generation and characterization of knockout mice from targeted embryonic stem (ES) cells have become one of the most powerful approaches to study gene function in vivo. However, experiments to identify targeted ES clones can be both labor-intensive and expensive when the targeting efficiency is low. Using the steroid receptor coactivator-3 (SRC-3) gene as a model, we have developed a rapid and cost-effective method for identification of targeted ES clones. Specifically, a promoterless LacZ sequence was fused to the 5'-coding sequence of SRC-3 in the targeting vector. After homologous recombination in ES cells, LacZ expression was regulated by the endogenous gene promoter. In cases of random insertions the beta-galactosidase would more likely not be produced due to lacking promoter or missing amino acid-reading frame. Accordingly, targeted ES clones were enriched more than 30 times in the population of blue clones positive to X-gal staining. Therefore, targeted ES clones can be selected quickly and economically by X-gal staining in large scale followed by Southern blot analysis on small number of blue clones if the gene of interest is expressed in ES cells. This strategy is particularly useful when the targeting efficiency is low and a reporter such as LacZ or GFP for mouse gene expression is desired.

Animals↗

Generation and characterization of a constitutively active Stat3 protein.

Stats are latent transcription factors involved in normal cellular signaling in response to cytokine or growth factor stimulation. Constitutive activation of Stats (primarily Stat3 and Stat5) has been implicated in growth dysregulation and oncogenesis. Furthermore, increased activation of Stats has been observed in several human tumors and tumor-derived cell lines. To assess the contribution of aberrant Stat activation in oncogenesis, we have created a chimeric molecule between Stat3beta and a portion of the Herpes simplex virus VP16 activation domain. The resulting protein, Stat3beta-VAD (VP16 activation domain), is tyrosine phosphorylated on Y705 and can bind DNA in the absence of upstream activation by c-Src or epidermal growth factor (EGF). Unlike Stat3alpha and Stat3beta, Stat3beta-VAD robustly activates transcription of several reporter genes without cytokine or growth factor stimulation. In addition, we show marked upregulation of the endogenous c-myc and c-fos genes upon inducible expression of Stat3beta-VAD in COS-7 cells. Our protein displays the constitutive transcriptional activation of Stat3alpha seen in human tumors and will be a valuable tool in screens for Stat3-regulated genes. In response to the established Stat3 involvement in human cancers, Stat3beta-VAD will also facilitate assessing the contribution of other cancer signaling cascades in the context of aberrant Stat3alpha activity in cancer development and progression.

Animals↗

Increased frequency of P-glycoprotein gene amplification in colchicine-resistant Rat-1 clones transformed by v-src.

A rat fibroblast cell line (Rat-1) carrying a temperature-sensitive mutation of v-src was used to determine whether inducible cellular transformation altered the ability of cells to amplify the p-glycoprotein gene in response to colchicine selection. Transformed and nontransformed Rat-1 fibroblasts selected under 4 times the LD50 generated the same number of colchicine-resistant colonies. We next examined colchicine-resistant colonies derived from transformed cells and compared them to colchicine-resistant colonies derived from nontransformed cells. When Rat-1 cells were selected at 35 degrees C (transforming temperature), 7 out of 7 clones exhibited a 3- to 5-fold p-glycoprotein gene amplification. These results contrasted to those found at the nontransforming temperature (40 degrees C); none of the 8 colchicine-resistant clones examined had amplified the p-glycoprotein gene. Thus in Rat-1 cells carrying a temperature-sensitive v-src gene, p-glycoprotein gene amplification was observed at a high frequency only in transformed clones selected at the temperature permissive for v-src activity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

[Identification and the origin of oncogenes, with special reference to sarcoma virus Y73].

A new sarcomagenic transforming gene, yes, was identified in an avian sarcoma virus Y73. The gene product is a gag-fused polyprotein p90yes and have protein kinase activity phosphorylating tyrosine residues in proteins. Vertebrates from fish to human were shown to contain DNA sequence (c-yes) homologous with viral yes. Total nucleotide sequence of Y73 genome was determined and the predicted amino acid sequence of p90yes was found to be highly homologous with p60src, a gene product of src in Rous sarcoma virus. These findings suggest that transforming gene yes and src are diverged from a common prototype onc gene at very early stage of vertebrate development or before that and conserved during the development since it plays an essential role.

Amino Acid Sequence↗