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- Title
- MECHANISM OF ACTION AND REGULATION OF MEMBRANE SERINE PROTEASE PROSTASIN IN THE PROSTATE AND PROSTATE CANCER.
- Creator
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Chen, Mengqian, Chai, Karl, University of Central Florida
- Abstract / Description
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The glycosylphosphatidylinositol (GPI)-anchored serine protease prostasin (PRSS8) is expressed at the apical membrane surface of epithelial cells and acts as a suppressor of tumor invasion when re-expressed in highly invasive human prostate and breast cancer cell lines. To better understand the molecular mechanisms underlying the anti-invasion phenotype associated with prostasin re-expression in prostate cancer cells, we expressed wild-type human prostasin or a serine active-site mutant...
Show moreThe glycosylphosphatidylinositol (GPI)-anchored serine protease prostasin (PRSS8) is expressed at the apical membrane surface of epithelial cells and acts as a suppressor of tumor invasion when re-expressed in highly invasive human prostate and breast cancer cell lines. To better understand the molecular mechanisms underlying the anti-invasion phenotype associated with prostasin re-expression in prostate cancer cells, we expressed wild-type human prostasin or a serine active-site mutant prostasin in the PC-3 human prostate carcinoma cells. Molecular changes were measured at the mRNA and the protein levels. The expression of several invasion-promoting molecules is regulated by prostasin re-expression, mediated by a protein-level down-regulation of the epidermal growth factor receptor (EGFR). As a result, the cellular response to EGF was reduced as shown by the down-regulation of EGF-stimulated Erk1/2 phosphorylation. The expression of Slug, urokinase-type plasminogen activator (uPA), urokinase-type plasminogen activator receptor (uPAR), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and granulocyte-macrophage colony stimulating factor (GM-CSF) was also down-regulated by prostasin re-expression in the PC-3 cells. Co-expression of prostasin and its activating protease matriptase with EGFR in FT-293 cells induces an apparent proteolytic cleavage of the EGFR in the extracellular domain at two specific sites, generating two N-terminally truncated EGFR fragments, named EGFR135 and EGFR110. The EGFR110 is constitutively tyrosine-phosphorylated, and in its presence the phosphorylation of downstream signaling molecules including Erk1/2 and Akt is increased under serum-free conditions. Neither EGFR135 nor EGFR110 is responsive to EGF stimulation. Deletions of the EGFR extracellular domain (ECD) were generated to map the matriptase-prostasin cleavage sites. Two candidate sites were localized to regions AA1-273 and AA273-410. These data support a mechanism of action for the matriptase-prostasin epithelial extracellular serine protease activation cascade by proteolytically modulating the EGF-EGFR signaling. Prostasin gene expression is down-regulated in high-grade and hormone-refractory prostate cancers. We investigated the mechanisms by which androgens regulate prostasin expression in the prostate and prostate cancer. We treated the LNCaP human prostate cancer cells with dihydrotestosterone (DHT) and measured the mRNA expression of prostasin and potential transcription regulators of prostasin predicted by interrogation of the prostasin gene promoter sequence. Prostasin mRNA expression in the LNCaP cells was not responsive to DHT treatment. DHT marginally up-regulated mRNA expression of SREBP-1c, SREBP-2, and SNAIL, but not SREBP-1a, while dramatically increased SLUG mRNA expression, in a dose-dependent manner. Co-transfection of a prostasin promoter-reporter and SREBP cDNA in HEK-293 cells resulted in stimulation of the promoter activity at ~2 fold by SREBP-1c, and up to 6 fold by SREBP-2; while co-transfection with SNAIL or SLUG cDNA resulted in repression of the promoter activity to 43% or 59%, respectively. Co-transfection of the SLUG cDNA negated SREBP-2 s stimulation of the prostasin promoter in a dose-dependent manner. Transfection of an SREBP-2 cDNA in HEK-293 and DU-145 cells resulted in up-regulation of the endogenously expressed prostasin while transfection of a SLUG cDNA in the LNCaP cells repressed prostasin expression. Multiple SREBP-2 binding sites, known as sterol regulatory elements (SRE s), were identified at positions -897, -538, +8, +71, and +98 (named SRE-897, SRE-538, SRE+8, SRE+71, and SRE+98) in the human prostasin gene promoter. Mutagenesis of the five SRE s was carried out to evaluate their roles in SREBP-2 up-regulation of prostasin. SRE+98, a novel functional sterol regulatory element was found to be the major site for the stimulatory response of prostasin gene expression to SREBP-2. CONCLUSIONS: Prostasin regulates the expression of several invasion-promoting molecules in prostate cancer cells by down-modulating the EGF-EGFR signaling pathway. Active prostasin induces proteolytic cleavage in the EGFR ECD at two specific sites. One of the N-terminally truncated EGFR, the EGFR110 is auto-phosphorylated along with increased phosphorylation of downstream signaling molecules. The effect of the androgen DHT on prostasin expression in prostate cells is mediated via SREBP s, which stimulate the promoter, and Slug, which represses the promoter. Slug is up-regulated by DHT and EGF, providing a molecular mechanism by which epithelial cell-specific genes are silenced during prostate cancer development and progression.
Show less - Date Issued
- 2007
- Identifier
- CFE0001782, ucf:47257
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001782
- Title
- IDENTIFICATION OF EPITHELIAL STROMAL INTERACTION 1 AND EPIDERMAL GROWTH FACTOR RECEPTOR AS NOVEL KR(&)#220;PPEL-LIKE FACTOR 8 TARGETS IN PROMOTING BREAST CANCER PROGRESSION.
- Creator
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Li, Tianshu, Zhao, Jihe, Khaled, Annette, Altomare, Deborah, Lambert, Stephen, University of Central Florida
- Abstract / Description
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Breast cancer is the major cause of cancer death among women worldwide. Understanding the mechanisms underlying breast cancer progression remains urgent for developing effective treatment strategies to eliminate breast cancer mortality. Our recent studies have demonstrated that Kr(&)#252;ppel-like transcriptional factor 8 (KLF8) plays a critical role for breast cancer progression. Other studies have shown that Epithelial stromal interaction 1 (EPSTI1), a recently identified stromal fibroblast...
Show moreBreast cancer is the major cause of cancer death among women worldwide. Understanding the mechanisms underlying breast cancer progression remains urgent for developing effective treatment strategies to eliminate breast cancer mortality. Our recent studies have demonstrated that Kr(&)#252;ppel-like transcriptional factor 8 (KLF8) plays a critical role for breast cancer progression. Other studies have shown that Epithelial stromal interaction 1 (EPSTI1), a recently identified stromal fibroblast-induced gene in non-invasive breast cancer cells and epidermal growth factor receptor (EGFR) are highly overexpressed in aggressively invasive breast carcinomas including triple negative breast cancers. In this thesis project, we demonstrate high co-overexpression of KLF8 with EPSTI1 as well as EGFR in invasive breast cancer cells and patient tumors. We also show that KLF8 upregulates the expression of EPSTI1 by directly binding and activating the EPSTI1 gene promoter, and KLF8 upregulates the expression of EGFR not only by directly activating the EGFR gene promoter but also by preventing EGFR translation from microRNA141-dependent inhibition. Genetic, signaling and animal cancer model analyses indicate that downstream of KLF8, EPSTI1 promotes the tumor invasion and metastasis by activating NF-?B through binding valosin containing protein (VCP) and subsequent degradation of I?B?, whereas EGFR promotes tumor growth and metastasis via activation of ERK. Taken together, these data identify EPSTI1 and EGFR as novel KLF8 targets in breast cancer and suggest that KLF8 may be targeted for new effective treatment of breast cancer.
Show less - Date Issued
- 2013
- Identifier
- CFE0005366, ucf:50474
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005366
