Elevated urokinase-specific surface receptor expression is maintained through its interaction with urokinase plasminogen activator

Ulinastatin inhibits the metastasis of nasopharyngeal carcinoma by involving uPA/uPAR signaling

Distant metastasis is the primary reason for treatment failure in patients with nasopharyngeal carcinoma (NPC). In this study, we investigated the effect of ulinastatin (UTI) on NPC metastasis and its underlying mechanism. Highly-metastatic NPC cell lines S18 and 58F were treated with UTI and the effect on cell proliferation, migration, and invasion were determined by MTS and Transwell assays. S18 cells with luciferase-expressing (S18-1C3) were injected into the left hind footpad of nude mice to establish a model of spontaneous metastasis from the footpad to popliteal lymph node (LN). The luciferase messenger RNA (mRNA) was measured by quantitative polymerase chain reaction (qPCR), and the metastasis inhibition rate was calculated. Key molecular members of the UTI-related uPA, uPAR, and JAT/STAT3 signaling pathways were detected by qPCR and immunoblotting. UTI suppressed the migration and infiltration of S18 and 5-8F cells and suppressed the metastasis of S18 cells in vivo without affecting cell proliferation. uPAR expression decreased from 24 to 48 h after UTI treatment. The antimetastatic effect of UTI is partly due to the suppression of uPA and uPAR. UTI partially suppresses NPC metastasis by downregulating the expression of uPA and uPAR.

The impact of COX-2 on invasion of osteosarcoma cell and its mechanism of regulation

Background

Recently, cyclooxygenase-2 (COX-2) has become an important new target in the field of tumor metastasis. However, the relationship between COX-2 gene expression and the behavior of osteosarcoma metastasis is largely unknown. The study is to investigate how antisense oligonucleotides (ODNs) of COX-2 inhibit the invasion of human osteosarcoma cell line OS-732 and their mechanism of regulation.

Methods

A COX-2 antisense oligonucleotide was designed, synthesized, and transfected into OS-732 human osteosarcoma cells. RT-PCR and western blotting were performed to determine the transfection efficiency. A modified Boyden-transwell assay was used to measure the inhibition rate of tumor cell invasion. In OS-732 cells transfected with COX-2 antisense ODNs, RT-PCR was used to examine the mRNA expression of urokinase-type plasminogen activator (uPA) and that of its receptor, uPAR.

Results

Both the mRNA and protein expression levels of COX-2 were significantly reduced when cells were transfected with COX-2 antisense ODNs, which significantly reduced the invasive ability of OS-732 cells in a dose-dependent manner. The expression levels of uPA and uPAR were also significantly reduced (p < 0.01).

Conclusion

COX-2 antisense ODNs significantly inhibited the invasion of OS-732 cells, primarily by decreasing the mRNA expression of uPA and uPAR.

Identification of a specific haptoglobin C-terminal fragment in arthritic synovial fluid and its effect on interleukin-6 expression

Haptoglobin (Hp), a major acute-phase plasma protein, has been found in arthritic synovial fluid (SF). However, the function and structural modifications of Hp in arthritic SF are unknown. To investigate in vivo generation of modified Hp associated with inflammatory disease, we examined a new Hp isoform in SF from patients with rheumatoid arthritis (RA). Specific Hp fragments of 28 000 and 15 000 molecular weight were identified in SF of patients with RA, and the two polypeptides were presumed to be fragments of the Hp β-chain (43 000 MW) produced by cleavage with plasmin. The 15 000 MW fragment, which is a C-terminal region of Hp, was observed at higher frequency and levels in RA than in osteoarthritis. Plasmin activity was also higher in SF of RA patients. A recombinant 15 000 MW Hp fragment up-regulated interlukin-6 expression in monocytic cells. These findings indicate that the C-terminal Hp fragment is generated by plasmin in local inflammatory environments and acts as an inflammatory mediator. They further suggest that a specific Hp fragment might be applied as a novel biomarker for the diagnosis and prognosis of inflammatory diseases such as RA.

Interleukin enhancer-binding factor 3 promotes breast tumor progression by regulating sustained urokinase-type plasminogen activator expression

Sustained urokinase-type plasminogen activator (uPA) expression is detected in aggressive breast tumors. Although uPA can be transiently upregulated by diverse extracellular stimuli, sustained, but not transiently upregulated uPA expression contributes to breast cancer invasion/metastasis. Unfortunately, how sustained uPA expression is achieved in invasive/metastatic breast cancer cells is unknown. Here, we show that sustained and transiently upregulated uPA expression are regulated by distinct mechanisms. Using a collection of transcription factor-targeted small-interfering RNAs, we discovered that interleukin enhancer-binding factor 3 (ILF3) is required for sustained uPA expression. Two discrete mechanisms mediate ILF3 action. The first is that ILF3 activates uPA transcription by binding to the CTGTT sequence in the nucleotides -1004∼-1000 of the uPA promoter; the second is that ILF3 inhibits the processing of uPA mRNA-targeting primary microRNAs (pri-miRNAs). Knockdown of ILF3 led to significant reduction in in vitro cell growth/migration/invasion and in vivo breast tumor development. Importantly, immunohistochemistry (IHC) showed that nuclear ILF3, but not cytoplasmic ILF3 staining correlates with elevated uPA level and higher grades of human breast tumor specimens. Nuclear localization of ILF3 highlights the role of ILF3 in sustained uPA expression as a transcription activator and pri-miRNA processing blocker. In conclusion, this study shows that ILF3 promotes breast tumorigenicity by regulating sustained uPA expression.

Impaired MicroRNA Processing Facilitates Breast Cancer Cell Invasion by Upregulating Urokinase-Type Plasminogen Activator Expression

Global mature microRNA (miRNA) expression is downregulated in cancers, and impaired miRNA processing enhances cancer cell proliferation. These findings indicate that the miRNA system generally serves as a negative regulator during cancer progression. In this study, we investigated the role of the miRNA system in cancer cell invasion by determining the effect of damaging miRNA processing on invasion-essential urokinase-type plasminogen activator (uPA) expression in breast cancer cells. Short hairpin RNAs specific for Drosha, DGCR8, and Dicer, key components of miRNA processing machinery, were introduced into 2 breast cancer cell lines with high uPA expression and 2 lines with poor uPA expression. Knockdown of Drosha, DGCR8, or Dicer led to even higher uPA expression in cells with high uPA expression, while it was unable to increase uPA level in cells with poor uPA expression, suggesting that the miRNA system most likely impacts uPA expression as a facilitator. In cells with high uPA expression, knockdown of Drosha, DGCR8, or Dicer substantially increased in vitro invasion, and depleting uPA abrogated enhanced invasion. These results thus link the augmented invasion conferred by impaired miRNA processing to upregulated uPA expression. uPA mRNA was a direct target of miR-193a/b and miR-181a, and a higher uPA level in cells with impaired miRNA processing resulted from less mature miR-193a/b and miR-181a processed from their respective primary miRNAs. Importantly, the levels of mature miR-193a, miR-193b, and miR-181a, but not their respective primary miRNAs, were lower in high uPA-expressing cells compared to cells with low uPA expression, and this apparently attributed to lower Drosha/DGCR8 expression in high uPA-expressing cells. This study suggests that less efficient miRNA processing can be a mechanism responsible for reduced levels of mature forms of tumor-suppressive miRNAs frequently detected in cancers.

Effects of ulinastatin and docetaxel on breast cancer invasion and expression of uPA, uPAR and ERK

Objective

To investigate the effects of ulinastatin and docetaxel on invasion of breast cancer cells and expression of uPA, uPAR and ERK, breast cancer MDA-MB-231 and MCF-7 cells.

Methods

The nude mice were treated with PBS, ulinastatin, docetaxel, and ulinastatin plus docetaxel, respectively. Their effects on 1) cell invasion ability was assayed using Transwell; 2) expression of uPA, uPAR and ERK was detected by real time PCR and Western blot; 3) uPA, uPAR and p-ERK protein level in nude mice was quantified by immunohistochemistry.

Results

1) Treatment with ulinastatin, docetaxel, and ulinastatin plus docetaxel, respectively, significantly inhibited MDA-MB-231 and MCF-7 cell invasion; 2) mRNA and protein levels of uPA, uPAR and ERK1/2 were inhibited by ulinastatin, but enhanced by docetaxel.

Conclusion

Ulinastatin can enhance the effects of docetaxel on invasion of breast cancer cells. And that uPA, uPAR and p-ERK expression is obviously inhibited by ulinastatin.

Discrimination of different forms of the murine urokinase plasminogen activator receptor on the cell surface using monoclonal antibodies

The urokinase plasminogen activator receptor (uPAR) is a versatile three-domain GPI-anchored protein, which binds urokinase plasminogen activator (uPA) and thereby focalises plasminogen activation on the cell surface. Generation of a proteolytic potential is essential in both normal physiological and pathological extracellular tissue remodelling processes. uPA can also cleave uPAR, resulting in liberation of the amino-terminal domain I, which encompasses binding sites for both uPA and the adhesion molecule, vitronectin. In order to localise the different uPAR forms on the plasma membrane of murine monocyte macrophage-like P388D.1 cells, we have now generated and characterised two high-affinity murine mAbs, mR3 and mR4, raised against murine uPAR. mR3 was found to recognise an epitope located in domain I of uPAR. Surface plasmon resonance analyses and cell binding studies revealed that this mAb was able to bind preformed complexes of murine pro-uPA and murine uPAR. In contrast, mR4 recognises domains II-III in uPAR and does not bind preformed pro-uPA-uPAR complexes in similar analyses. Immunofluorescence microscopy of P388D.1 cells revealed that mR3 stained the cells equally well in the presence or absence of saturation with the amino-terminal fragment of uPA, ATF. However, the signal intensity obtained using another uPAR domain I specific mAb, mR1, was significantly reduced upon ATF saturation. Furthermore, when adding ATF, mR4 selectively stained the cleaved receptor. Applying these newly generated mAbs, we additionally demonstrated that cleaved and intact uPAR was evenly distributed on the surface of these cells.

Prostate cancer cell-derived urokinase-type plasminogen activator contributes to intraosseous tumor growth and bone turnover

A variety of proteases have been implicated in prostate cancer (PC) bone metastasis, but the individual contributions of these enzymes remain unclear. Urokinase-type plasminogen activator (uPA), a serine protease, can activate plasminogen and stimulate signaling events on binding its receptor uPAR. In the present study, we investigated the functional role of PC cell-associated uPA in intraosseous tumor growth and bone matrix degradation. Using a severe combined immunodeficient-human mouse model, we found that PC3 cells were the major source of uPA in the experimental bone tumor. Injection of uPA-silenced PC3 cells in bone xenografts resulted in significant reduction of bone tumor burdens and protection of trabecular bones from destruction. The suppressed tumor growth was associated with the level of uPA expression but not with its activity. An increase in the expression of PAI-1, the endogenous uPA inhibitor, was found during in vitro tumor-stromal interactions. Up-regulation of PAI-1 in bone stromal cells and preosteoclasts/osteoblasts was due to soluble factor(s) released by PC cells, and the enhanced PAI-1 expression in turn stimulated PC cell migration. Our results indicate that both tumor-derived uPA and tumor-stroma-induced PAI-1 play important roles in intraosseous metastatic PC growth through regulation of a uPA-uPAR-PAI-1 axis by autocrine/paracrine mechanisms.