Transducer Of ERBB2 Research Articles

MicroRNA-25 promotes gastric cancer migration, invasion and proliferation by directly targeting transducer of ERBB2, 1 and correlates with poor survival.

Gastric cancer (GC) is one of the most common tumors and the molecular mechanism underlying its metastasis is still largely unclear. Here, we show that miR-25 was overexpressed in plasma and primary tumor tissues of GC patients with tumor node metastasis stage (III or IV) or lymph node metastasis. MiR-25 inhibition significantly decreased the metastasis, invasion and proliferation of GC cells in vitro, and reduced their capacity to develop distal pulmonary metastases and peritoneal dissemination in vivo. Furthermore, miR-25 repressed transducer of ERBB2, 1 (TOB1) expression by directly binding to TOB1-3'-UTR, and the inverse correlation was observed between the expressions of miR-25 and TOB1 mRNA in primary GC tissues. Moreover, the loss of TOB1 increased the metastasis, invasion and proliferation of GC cells, and the restoration of TOB1 led to suppressed metastasis, invasion and proliferation. The receiver operating characteristics analysis yielded an area under the curve value of 0.7325 in distinguishing the GC patients with death from those with survival. The analysis of optimal cutoff value revealed poor survival in GC patients with high plasma concentrations of miR-25 (>0.2333 amol/μl). Taken together, miR-25 promotes GC progression by directly downregulating TOB1 expression, and may be a noninvasive biomarker for the prognosis of GC patients.

The role of antiproliferative gene Tob1 in the immune system.

Tob1 (transducer of ERBB2-1, TOB1 is humans) is a member of the antiproliferative (APRO) family of proteins that controls cell cycle progression in several cell types. In addition, Tob1 has been implicated in diverse cellular mechanisms such as embryonic dorsal development, and T helper 17 (Th17) cell function. More recently, evidence linking Tob1 function to experimental and human immune related disorders has mounted, thus underscoring the potential of this molecule as a biomarker and as a therapeutic target. This article reviews these functions with an emphasis on their implications for human autoimmune diseases such as multiple sclerosis.

MicroRNA-25 promotes gastric cancer migration, invasion and proliferation by directly targeting transducer of ERBB2, 1, and predicts poor patient survival (TUM2P.882)

Abstract Gastric cancer (GC) is the most common tumors and the molecular mechanism underlying tumor metastasis is still largely unclear. Here, we show that miR-25 was overexpressed in plasma and primary tumor tissues of GC patients with TNM stage (III or IV) or lymph node metastasis. MiR-25 inhibition significantly decreased the metastasis, invasion and proliferation potential of GC cells in vitro, and reduced their capacity to develop distal pulmonary metastases and peritoneal dissemination in vivo. Furthermore, miR-25 repressed transducer of ERBB2, 1 (TOB1) expression by directly binding to the 3’-UTR, and the inverse correlation was observed between the expressions of miR-25 and TOB1 mRNA in primary GC tissues. Moreover, the loss of TOB1 increased the metastasis, invasion and proliferation of GC cells, and the restoration of TOB1 led to the metastasis, invasion and proliferation suppression. The receiver operating characteristics (ROC) analysis yielded an area under the curve (AUC) value of 0.7325 in distinguishing the GC patients with death from those with living. The analysis of optimal cutoff value revealed significant difference of patients’ survival between GC patients with high plasma concentrations of miR-25 (> 0.2333 amol/μL) and those with low (< 0.2333 amol/μL). Taken together, miR-25 promotes GC progress by directly down-regulating TOB1 expression, and the high concentrations of miR-25 in plasma of GC patients predict poor patient survival.

Transducer of ErbB2.1 enhances radiosensitivity of human lung cancer A549 cells

Objective To evaluate the effect of transducer of ErbB2.1 (TOB1) on radiosensitivity of human lung cancer cell line A549 and investigate the related mechanisms.Methods The lipofectamine mediated TOB1 recombinant plasmid transfection and selective G418 cell culture were performed to obtain lung cancer cell line A549 with over-expressed TOB1.The effects on lung cancer cell radiosensitivity in vitro were evaluated by clonogenic survival analysis,and comet DNA damage assay was used to understand the molecular mechanisms of radiosensitization of TOB1 and investigate its effects on the initial DNA damage response to irradiation.Western blotting analysis was performed to determine the related mechanisms.Results Using Lipofectamine and G418-mediated plasmid stable transfection,multiple clones stably transfected with TOB1 were selected.As compared with parental and mock transfected cells,enhanced radiosensitivity was detected in A549/TOB1 cells and the sensitizing enhancement ratio was 1.63.Comet DNA damage assay revealed that the tail moment of A549/TOB1 cells were (25.71 ± 4.32) ％,which was significantly higher than that of A549 cells.Western blotting analysis revealed that TOB1 could down-regulate the expression of ATM,MGMT,DNA-PKcs,Ku70,Ku80 and XRCC4 as compared with parental cells.Conclusion Overexpression of TOB1 enhanced the radiosensitivity of A549 cells in vitro,at least by its potential function as an expression regulator of DNA damage repair related proteins,as well as its regulation on DNA damage repair. Key words: Transducer of ErbB-2.1 ; Lung cancer; Radiosensitivity

Contribution of Orb2A Stability in Regulated Amyloid-Like Oligomerization of Drosophila Orb2

How learned experiences persist as memory for a long time is an important question. In Drosophila the persistence of memory is dependent upon amyloid-like oligomers of the Orb2 protein. However, it is not clear how the conversion of Orb2 to the amyloid-like oligomeric state is regulated. The Orb2 has two protein isoforms, and the rare Orb2A isoform is critical for oligomerization of the ubiquitous Orb2B isoform. Here, we report the discovery of a protein network comprised of protein phosphatase 2A (PP2A), Transducer of Erb-B2 (Tob), and Lim Kinase (LimK) that controls the abundance of Orb2A. PP2A maintains Orb2A in an unphosphorylated and unstable state, whereas Tob-LimK phosphorylates and stabilizes Orb2A. Mutation of LimK abolishes activity-dependent Orb2 oligomerization in the adult brain. Moreover, Tob-Orb2 association is modulated by neuronal activity and Tob activity in the mushroom body is required for stable memory formation. These observations suggest that the interplay between PP2A and Tob-LimK activity may dynamically regulate Orb2 amyloid-like oligomer formation and the stabilization of memories.

MicroRNA-378 functions as an onco-miR in nasopharyngeal carcinoma by repressing TOB2 expression

Increasing evidence indicates that microRNAs (miRNAs) has been implicated in the progression and metastasis of numerous cancers. In particular, abnormal expression of miR-378 has been observed in various cancers and is associated with cell survival, migration, invasion, angio-genesis and tumor growth. Our previous studies have shown that miR-378 was decreased in nasopharyngeal carcinoma (NPC) plasma and was negatively correlated with NPC progression. However, the tissue expression of miR-378 and its biological function remained unknown in NPC. In this study, we report for the first time that expression level of miR-378 was commonly upregulated in both NPC tissues and NPC cell lines compared to normal healthy nasopharyngeal epithelial samples and human nasopharyngeal epithelial cell lines (NP69), respectively, and was opposite to the reported results in plasma. Functional studies showed that upregulation of miR-378 dramatically promoted cell proliferation, colony formation, migration and invasion in vitro, as well as tumor growth in vivo. Bioinformatics analyses were performed to predict the target genes of miR-378, and the following mechanistic investigations revealed that miR-378 overexpression was able to downregulate the expression of transducer of ERBB2 (TOB2), a potential tumor suppressor, and miR-378 silencing enhanced TOB2 expression. In clinical specimens, TOB2 was widely repressed in tumor tissues accompanied by miR-378 overexpression. Taken together, this study indicates that miR-378 regulates TOB2 and may function as an onco-miR in NPC progression, providing a potential target for gene therapy of NPC.

Overexpression of TOB1 confers radioprotection to bronchial epithelial cells through the MAPK/ERK pathway

The aim of this study was to investigate the effects and mechanisms of antiproliferative transducer of erbB2, 1 (TOB1) on the radiosensitivity of the normal human bronchial epithelial cell line HBE. After exposure to different doses of irradiation or a certain dose for different time intervals, the expression of TOB1 mRNA and protein in HBE cells was determined by semi-quantitative RT-PCR and western blot analysis. Liposome-induced recombinant plasmid transfection and G418 selection were performed to establish a stably transfected TOB1-overexpressing HBE cell line. A clonogenic assay was used to determine the radiosensitivity of the HBE cells with different TOB1 expression statuses. The cell cycle distribution was detected by flow cytometry. The ionizing radiation (IR)-induced γ-H2AX foci formation was detected by immunofluorescence assay. The related mechanism was explored by western blot analysis. TOB1 expression in the HBE cells was not induced by IR, neither dose-dependently nor time-dependently. Compared to the parental or 'mock' transfected HBE cells, the radiosensitivity of HBE cells overexpressing TOB1 was significantly decreased (P<0.05). Exogenous TOB1 prevented HBE cells from apoptosis after IR, in contrast to the control cells (P<0.05), and significantly decreased the IR-induced γ-H2AX foci formation. After IR, the expression of DNA damage repair proteins such as XRCC1, MRE11, FEN1 and ATM was increased in the TOB1‑overexpressing HBE cells when compared with the expression levels in the control cells. HBE/TOB1 cells presented a much higher phosphorylated ERK1/2 and phosphorylated p53 when compared with the levels in the control cell lines when receiving 6 Gy of X-rays. Notably, the increased expression of phosphorylated p53 in HBE/TOB1 cells after IR was sufficiently blocked by U0126, a specific inhibitor of MEK1/2. Different from its functions in several lung cancer cell lines, TOB1 demonstrated a radioprotective function in the immortalized normal human bronchial epithelial cell line HBE via the MAPK/ERK signaling pathway.

Abstract 2042: TOB1 promotes cell survival in estrogen-independent estrogen receptor-positive breast cancer.

Abstract Antiestrogens are the most widely administered endocrine agents for the treatment of estrogen receptor (ER)-expressing breast cancers, such as tamoxifen, fulvestrant and aromatase inhibitor. However, most initially responsive breast tumors acquire resistance and become estrogen-independent. To find potential therapeutic target(s) against drug resistance, we performed siRNA library screening studies to identify cell survival determinants in estrogen independent cell lines from 631 ER network related genes. LCC1 and LCC9 cells, derivatives of MCF-7, are estrogen-independent. LCC1 cells are sensitive to fulvestrant and tamoxifen. LCC9 cells are resistant to fulvestrant and cross-resistant to tamoxifen. A number of genes selectively support the survival of estrogen-independent tumor cells, including TOB1 (Transducer of ErbB2). TOB1 gene knockdown significantly inhibited (&amp;gt;50%) estrogen-independent cell growth in LCC1 and LCC9 cells, but had much less effect on the survival of MCF-7 cells (10%). These cell lines have similar levels of Tob1 protein. TOB1 knockdown did not cause apoptosis or autophagy. DNA replication was reduced and G1 to S phase transition was blocked by TOB1 knockdown in the estrogen-independent cell lines. Next, we studied cell-signaling pathways that regulate cell cycle transition. Cyclin D1 was upregulated and activated by TOB1 knockdown in estrogen-independent cells, but not in MCF-7 cells. Therefore, cyclin D1 might be involved in G1/S transition blockage induced by Tob1 inhibition. TOB1 knockdown also activated cell cycle checkpoint kinase 2 (Chk2) and induced DNA damage. Our data demonstrated that Tob1 promotes cell survival after ER+ breast cancer cells acquire estrogen-independence, which might be mediated by cyclin D1. Citation Format: Yong-Wei Zhang, Rochelle Nasto, Robert Clarke, Louis M. Weiner. TOB1 promotes cell survival in estrogen-independent estrogen receptor-positive breast cancer. [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 2042. doi:10.1158/1538-7445.AM2013-2042

Enhanced radiosensitivity of NSCLC cells by transducer of erbB2.1 (TOB1) through modulation of the MAPK/ERK pathway

Transducer of erbB2.1 (TOB1) is a member of the B-cell translocation gene (BTG)/transducer of erbB2 (TOB) anti‑proliferative protein family. Previous studies have demonstrated that overexpression of TOB1 significantly enhances the radiosensitivity of breast and cervical cancer cells. However, the potential mechanisms of TOB1 are still debated. In the present study, we evaluated the effects of infrared (IR) radiation on TOB1 expression in the human lung cancer cell lines NCI-H1975 and A549 via western blot analysis. NCI-H1975 cells were transfected with TOB1 recombinant plasmid, and A549 cells were treated with TOB1-small interfering RNA(siRNA) to establish gain-of-function and loss-of‑function cell models. The effects of radiation and TOB1 overexpression and silencing on clonogenic survival, cell cycle distribution and DNA repair were assessed. Western blot analysis was performed to determine the related mechanisms. The expression levels of TOB1 were significantly induced by IR radiation. Overexpression of TOB1 abrogated radiation-induced G2/M arrest, reduced clonogenic cell survival and enhanced γ-H2AX foci in NCI-H1975 cells exposed to irradiation. TOB1-siRNA demonstrated opposite effects in A549 cells. TOB1 regulated the activation of mitogen-activated protein kinase (MAPK) and modulated the phosphorylation of p53 via activation of the MAPK/extracellular signal-regulated kinase (ERK) pathway. The findings suggest that TOB1 may be a novel molecular target of irradiation. TOB1 modulated the radiosensitivity of lung cancer cells via the MAPK/ERK signaling pathway.

Transducer of erbB2.1 is a potential cellular target of gefitinib in lung cancer therapy

Gefitinib, the specific inhibitor of the epidermal growth factor receptor (EGFR), may cause growth delay in cancer cell lines. Thorough understanding of the downstream cellular signaling of gefitinib will facilitate the discovery of biomarkers for predicting outcomes and monitoring anti-EGFR therapies, and provide information for key targets for therapeutic intervention. In this study, we investigated the role of transducer of erbB2.1 (TOB1) in gefitinib therapy. Using the lung carcinoma cell lines A549 and NCI-H1975, the results suggested that gefitinib might mediate cell cycle arrest in lung cancer cells at least by targeting TOB1 expression. Gefitinib treatment caused cell cycle arrest predominantly at the G1 phase, which is associated with TOB1 nuclear translocation and its interaction with cyclin D1. We also showed that knockdown of TOB1 expression by RNAi rescued lung cancer cells from gefitinib-induced cell-proliferative arrest. These results suggest that TOB1 interaction with cyclin D1 and nuclear translocation is directly involved in the gefitinib-induced anti-proliferative cell cycle arrest.

Molecular cloning, characterization and expression analysis of B cell translocation gene 1 in grass carp Ctenopharyngodon idella

An expressed sequence tag (EST) of B cell translocation gene (BTG) 1 (gcbtg1) was obtained from a grass carp Ctenopharyngodon idellus intestinal complementary (c)DNA library and the full-length cDNA sequence was acquired by rapid amplification of cDNA ends (RACE) technology. The predicted Gcbtg1 protein contains the box A and box B motifs which characterized the BTG and transducer of ERBB2 (TOB) family. Multiple alignment analysis reveals that Gcbtg1 shares an overall identity of 65-94% with Gcbtg1s of other vertebrates. Real-time quantitative PCR analysis reveals that the highest expression level of gcbtg1 was detected in liver and the lowest in muscle. Western blotting analysis indicates that the immunological cross-reactivity occurs between C. idella and human Homo sapiens BTG1 protein. A 1008 bp 5'-flanking region sequence was cloned and analysed.

Suppression of human lung cancer cell proliferation and metastasis in vitro by the transducer of ErbB-2.1 (TOB1)

To investigate the effects of the transducer of ErbB-2.1 (TOB1) on the proliferation, migration and invasion of human lung cancer cells in vitro. Human lung cancer cell lines (95-D, A549, NCI-H1299, NCI-H1975, NCI-H661, NCI-H446, NCI-H1395, and Calu-3) and the normal human bronchial epithelial (HBE) cell line were tested. The expression levels of TOB1 in the cells were determined with Western blot and RT-PCR analyses. TOB1-overexpressing cell line 95-D/TOB1 was constructed using lipofectamine-induced TOB1 recombinant plasmid transfection and selective G418 cell culture. The A549 cells were transcend-transfected with TOB1-siRNA. MTT assay, flow cytometry and Western blot analysis were used to examine the effects of TOB1 on cancer cell proliferation and wound healing. Transwell invasive assay was performed to evaluate the effects of TOB1 on cancer cell migration and invasion. The activity of MMP2 and MMP9 was measured using gelatin zymography assay. The expression levels of TOB1 in the 8 human lung cancer cell lines were significantly lower than that in HBE cells. TOB1 overexpression inhibited the proliferation of 95-D cells, whereas TOB1 knockdown with TOB1-siRNA promoted the growth of A549 cells. Decreased cell migration and invasion were detected in 95-D/TOB1 cells, and the suppression of TOB1 enhanced the metastasis in A549 cells. TOB1 overexpression not only increased the expression of the phosphatase and tensin homolog (PTEN), an important tumor suppressor, but also regulated the downstream effectors in the PI3K/PTEN signaling pathway, including Akt, ERK1/2, etc. In contrast, decreased expression of TOB1 oppositely regulated the expression of these factors. TOB1 also regulates the gelatinase activity of MMP2 and MMP9 in lung cancer cells. The results demonstrate that the PI3K/PTEN pathway, which is essential for carcinogenesis, angiogenesis, and metastasis, may be one of the possible signaling pathways for regulation of proliferation and metastasis of human lung cancer cells by TOB1 in vitro.

Transducer of ERBB2 1 (TOB1)

Transducer of ERBB2 1 (TOB1)

TOB suppresses breast cancer tumorigenesis

Transducer of ErbB-2 (TOB) is a member of the TOB/Btg gene family. A role for TOB in the suppression of human tumorigenesis has been proposed, based on the observations that TOB-knockout mice spontaneously form tumors and TOB expression is lost in human lung and thyroid cancers. However, the role of TOB in human breast cancer remains unknown. To evaluate the this role, we screened a panel of breast cancer cell lines for TOB expression levels and found that they are inversely correlated with the tumorigenicity and metastatic potential of the cell lines. In addition, we demonstrated for the first time that TOB expression is inversely correlated with breast cancer progression in clinical specimens. These results strongly indicate that the loss of TOB expression plays a role in breast cancer progression. We have also provided the first evidence that TOB functions as a tumor suppressor in breast cancer MCF-7 cells, using gain-of-function and loss-of-function approaches to manipulate TOB expression. Cell-cycle analysis further revealed that TOB can prolong the G1-S phase transition by inducing arrest at G1-S phase. Moreover, upregulation of the cyclin-dependent kinase inhibitor p27 and downregulation of the antiapoptotic proteins Bcl-2 and Bcl-XL were observed in MCF7/TOB transfectants. Conversely, opposite results were observed in shRNA-TOB transfectants. Furthermore, decreased activity of Erk2, AKT, CrkL, PDK1, and Smads were observed in TOB-overexpressing cells. Taken together, these data provide evidence that TOB can function as a tumor suppressor in breast cancer through modulation and regulation of multiple signaling pathways.

Tumor growth suppression by adenovirus-mediated introduction of a cell growth suppressing gene tob in a pancreatic cancer model

TOB (transducer of ErbB-2) is a tumor suppressor that interacts with protein-tyrosine kinase receptors, including ErbB-2. Introduction of the tob gene into NIH3T3 cells results in cell growth suppression. In this study, we evaluated the effect of tob expression in pancreatic cell lines (AsPC-1, BxPC-3, SOJ) and discuss the tumor-suppressing effects of adenoviral vector expressing tob cDNA. We first measured the levels of endogenous tob mRNA being expressed in all pancreatic cancer cell lines. Then, we examined the effect of adenoviral vector containing tob cDNA (Ad- tob vector) on cancer cell lines. The viral vector was expanded with transfection in 293 cells. The titer of the vector was 350 × 10 6 pfu/ml. These cancer cells were able to be transfected with MOI 20 without adenoviral toxicity. The transfection of Ad- tob vector results in growth suppression of SOJ and AsPC-1 cell lines. The magnitude of the expression of the Ad- tob gene in cancer is correlated to tumor suppressive activity. We prepared pancreatic cancer peritonitis models using a peritoneal injection of AsPC-1 cells. In this model, bloody ascites and multiple tumor nodules were seen at the mesentery after 16 days. AdCA tob (50 × 10 6 pfu/day) was administered from day 5 to day 9 after 4 days of peritoneal injection of 2 × 10 6 AsPC-1 cells. Tumor growth suppression occurred 10 days after peritoneal injection of AdCA tob compared with the control group. There were no tumor nodules in the abdomen and no bloody ascites. These results suggest that the peritoneal injection of AdCA tob has potential to suppress the formation of pancreatic cancer peritonitis, and can be applied for chemotherapy-resistant cancer peritonitis.

Rapid Suppression of Cytokine Transcription in Human CD4+CD25− T Cells by CD4+Foxp3+ Regulatory T Cells: Independence of IL-2 Consumption, TGF-β, and Various Inhibitors of TCR Signaling

CD4+CD25(high) forkhead box P3+ regulatory T cells (Treg) are critical mediators of peripheral self-tolerance and immune homeostasis. Treg suppress proliferation and cytokine production of conventional T cells (Tcon). The exact mechanism of suppression, however, is still unknown. To gain a better understanding of Treg function, we investigated the kinetics of cytokine suppression in Tcon reisolated from cocultures with preactivated human Treg. Treg inhibited induction of Th1 cytokine mRNA as early as 1 h after stimulation, whereas induction/suppression of Th2 cytokines was delayed to 10-15 h. We show that immediate cytokine mRNA suppression in Tcon was neither dependent on TGF-beta/IL-10 or IL-2 consumption, nor on induction of the transcriptional-repressor forkhead box P3 or other anergy-related genes (e.g., gene related to anergy, transducer of ErbB-2, forkhead homolog-4, repressor of GATA, inducible cAMP early repressor). In contrast, lymphocyte activation gene 3, suppressor of cytokine signaling 1, and suppressor of cytokine signaling 3 mRNA were strongly up-regulated in Tcon in the presence of Treg. However, protein analysis did not confirm a role for these proteins in early suppression. Thus, the identification of a fast inhibitory mechanism in Tcon induced by Treg constitutes an important step for future efforts to unravel the entire elusive suppressive mechanism.

Tob1 Controls Dorsal Development of Zebrafish Embryos by Antagonizing Maternal β-Catenin Transcriptional Activity

Maternal beta-catenin and Nodal signals are essential for the formation of the dorsal organizer, which, in turn, induces neural and other dorsal tissue development in vertebrate embryos. Tob (Transducer of ErbB2) proteins possess antiproliferative properties and are known to influence BMP signaling, but their relationship to other signaling pathways and to embryonic patterning in general was unclear. In this study, we demonstrate that zebrafish tob1a is required for correct dorsoventral patterning. Mechanistically, Tob1a inhibits beta-catenin transcriptional activity by physically associating with beta-catenin and preventing the formation of beta-catenin/LEF1 complexes. Although Tob1a can also inhibit the transcriptional activity of the Nodal effector Smad3, its role in limiting dorsal development is executed primarily by antagonizing the beta-catenin signal. We further demonstrate that Tob family members across species share similar biochemical properties and biological activities.

The negative cell cycle regulator, Tob (transducer of ErbB-2), is involved in motor skill learning

Tob (transducer of ErbB-2) is a negative cell cycle regulator with anti-proliferative activity in peripheral tissues. Our previous study identified Tob as a protein involved in hippocampus-dependent memory consolidation (M.L. Jin, X.M. Wang, Y.Y. Tu, X.H. Zhang, X. Gao, N. Guo, Z.Q. Xie, G.P. Zhao, N.H. Jing, B.M. Li, Y.Yu, The negative cell cycle regulator, Tob (Transducer of ErbB-2), is a multifunctional protein involved in hippocampus-dependent learning and memory, Neuroscience 131 (2005) 647–659). Here, we provide evidence that Tob in the central nervous system is engaged in acquisition of motor skill. Tob has a relatively high expression in the cerebellum. Tob expression is up-regulated in the cerebellum after rats receive training on a rotarod-running task. Rats infused with Tob antisense oligonucleotides into the 4th ventricle exhibit a severe deficit in running on a rotating rod or walking across a horizontally elevated beam.

Profile of differentially expressed genes after transfer of chromosome 17 into the breast cancer cell line CAl51

Previous studies have shown that transfer of chromosome 17 suppresses the tumorigenic phenotype of the breast cancer cell line CAL51, suggesting the presence of putative tumor suppressor genes on this chromosome. Suppression subtractive hybridization and oligonucleotide microarray analyses were performed to identify differentially expressed genes in nontumorigenic microcell hybrids, CAL/17-1 and CAL/17-3, when compared with CAL51 cells. In total, 263 differentially expressed transcripts were associated with these phenotypes. Of these, a high percentage is involved in various biological processes associated with tumorigenesis, including DNA-dependent regulation of transcription, regulation of cell cycle, signal transduction, and cell proliferation. Microarray analysis of selected chromosome 17 genes in a series of 25 human primary breast tumors showed associations with clinicopathologic parameters of the tumors. Of these genes, TOB1 (transducer of ERBB2) was selected for further expression analysis. Using RT-PCR and immunohistochemical staining of tissue microarrays, we could reveal a differential mRNA and protein expression of TOB1 in the majority of breast tumors and lymph node metastases compared with normal breast tissues, indicating a potential role of this protein in breast tumorigenesis.

The negative cell cycle regulator, Tob (transducer of ErbB-2), is a multifunctional protein involved in hippocampus-dependent learning and memory

Tob (transducer of ErbB2) is a negative cell cycle regulator with anti-proliferative activity in the periphery. Using a behavioral screening paradigm to look for novel gene functions in the brain, we identified Tob as a brain-expressed protein involved in learning and memory. Behavioral training of fear-conditioning triggered a transient elevation of Tob protein, which preceded the formation of long-term memory. Functional perturbation of Tob by intra-CA1 infusion of antisense oligonucleotides in rats impaired spatial learning and memory in the Morris water maze and long-term memory for contextual fear conditioning, two behavioral paradigms that require the hippocampus. Furthermore, long-term potentiation was suppressed by Tob antisense infusion into the CA1 region. Together, these results indicate that the negative cell cycle regulator Tob is a multifunctional protein involved in hippocampus-dependent learning and memory.