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The Tumor Suppressive Effects of HPP1 Are Mediated Through JAK-STAT-Interferon Signaling Pathways.

ABSTRACT: HPP1, a novel tumor suppressive epidermal growth factor (EGF)-like ligand, mediates its effects through signal transducer and activators of transcription (STAT) activation. We previously demonstrated the importance of STAT1 activation for HPP1 function; however the contribution of STAT2 remains unclear. We sought to delineate the components of JAK-STAT-interferon (IFN) signaling specifically associated with HPP1s biological effects. Using stable HPP1-HCT116 transfectants, expression analyses were performed by polymerase chain reaction (PCR)/western blotting while expression knockdowns were achieved using siRNA. Growth parameters evaluated included proliferation, cell cycle distribution, and anchorage-independent growth. STAT dimerization, translocation, and DNA binding were examined by reporter assays, fluorescent microscopy, and chromatin immunoprecipitation (ChIP), respectively. Forced expression of HPP1 in colon cancer cell lines results in the upregulation of total and activated levels of STAT2. We have also determined that JAK1 and JAK2 are activated in response to HPP1 overexpression, and are necessary for subsequent STAT activation. Overexpression of HPP1 was associated with significant increases in STAT1:STAT1 (p=0.007) and STAT1:STAT2 (p=0.036) dimer formation, as well as subsequent nuclear translocation. By ChIP, binding of activated STAT1 and STAT2 to the interferon-signaling regulatory element promoter sites of the selected genes, protein kinase RNA-activated (PKR), IFI44, and OAS1 was demonstrated. STAT2 knockdown resulted in partial abrogation of HPP1s growth suppressive activity with increased proliferation (p<0.0001), reduced G1/G0 phase cell cycle fraction, and a restoration of growth potential in soft agar (p<0.01). Presumably as a consequence of upregulation of IFN signaling elements, HPP1 overexpression resulted in an acquisition of exogenous IFN sensitivity. Physiologic doses of IFN-? resulted in a significant reduction in proliferation (p<0.001) and increase in G1/G0 cell cycle arrest in HPP1 transfectants. STAT2 is necessary for HPP1-associated growth suppression, and mediates these effects through activation of IFN-? pathways. Given the interest in therapeutic targeting of oncogenic erbB proteins, further understanding of HPP1s role as a tumor suppressive EGF-like ligand is warranted.

SUBMITTER: Hernandez JM

PROVIDER: S-EPMC4523047 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

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The Tumor Suppressive Effects of HPP1 Are Mediated Through JAK-STAT-Interferon Signaling Pathways.

Hernandez Jonathan M JM Elahi Abul A Clark Whalen W Humphries Leigh Ann LA Wang Jian J Achille Alex A Seto Ed E Shibata David D

DNA and cell biology 20150519 8

HPP1, a novel tumor suppressive epidermal growth factor (EGF)-like ligand, mediates its effects through signal transducer and activators of transcription (STAT) activation. We previously demonstrated the importance of STAT1 activation for HPP1 function; however the contribution of STAT2 remains unclear. We sought to delineate the components of JAK-STAT-interferon (IFN) signaling specifically associated with HPP1s biological effects. Using stable HPP1-HCT116 transfectants, expression analyses wer ...[more]

PMID: 26061044

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Project description:Background: Esophagus cancer is a malignant tumor with a high incidence rate, and radiation is an important modality for esophageal cancer therapy. However, therapeutic failure in the treatment of ESCC is often attributed to an inherent radio-resistance of the tumor cells. This study discusses effect and mechanism of carbon ion exerts tumor-inhibiting proliferation via down-regulation of LIF in esophageal squamous cell carcinoma. Methods: Colony formation, CCK8 and EdU assays were used to detect cell survival and proliferation after 0 and 2Gy carbon ion irradiation of ECA109 cells. Proteomics changes were probed in response to carbon ion irradiation using quantitative proteomics approach incorporating TMT isotope tags. Then, candidate genes were identified via bioinformatics analysis methods and microarray results were verified by real-time qPCR. Paired ESCC tumor tissues and adjacent non-tumor samples from 17 patients were collected and used for detecting expression by immunohistochemistry. Furthermore, small interfering RNA (siRNA) was transfected into ECA109 and KYSE150 cells and cell proliferation was analyzed by EdU assay. Flow cytometry and Western blot were performed to measure the and apoptosis and JAK-STAT3 protein expression level of ECA109 and KYSE150 cells combined drugs after siLIF transfection. Results: When compared with the control (0Gy), Inhibition of ECA109 cell proliferation and clonogenic survival by 2 Gy carbon ions, radiation group screened 360 differentially expressed proteins, 156 of which were up-regulated and 144 were down-regulated. Downregulation of LIF expression by siRNA enhances apoptotic in the ECA109 and KYSE150 cells, significantly inhibited esophageal squamous cell carcinoma cells proliferation. In ESCC cells, the JAK/STAT3 signaling pathway is inhibited in a LIF-dependent manner, resulting in the expression of STAT3 downstream target genes. Carbon ions combined with siLIF inhibited cell proliferation more significantly. The inhibitory cell proliferation effect was more pronounced by the combined intervention of carbon ion irradiation with siLIF. LIF expression was 18.51±9.84 and 5.82±4.50 in 17 paired ESCC tissues and adjacent non-cancerous tissues, respectively. LIF protein expression was lower in ESCC than in the adjacent normal tissue. Conclusion: The findings of this study reveal that Carbon ion knockdown was shown to downregulate LIF in ESCC cells. LIF is involved in ESCC proliferation and inhibited the ESCC cell proliferation by activating the STAT3 signaling pathways.

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The Tumor Suppressive Effects of HPP1 Are Mediated Through JAK-STAT-Interferon Signaling Pathways.

Publications

The Tumor Suppressive Effects of HPP1 Are Mediated Through JAK-STAT-Interferon Signaling Pathways.

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