The plasminogen activator inhibitor "paradox" in cancer

Proteolysis in general and specifically the plasminogen activating system regulated by urokinase (uPA) its specific receptor, the GPI membrane anchored urokinase receptor (uPAR) and the specific plasminogen activator inhibitor 1 (PAI-1) plays a major role in tumorigenesis, tumor progression, tumor invasion and metastasis formation. This is exemplified by a body of published work showing a positive correlation between the expression of uPA or uPAR in several tumors and their malignancy. It is generally assumed that such a "pro-malignant" effect of the uPA-uPAR system is mediated by increased local proteolysis thus favoring tumor invasion, by a pro-angiogenic effect of this system and also by uPA-uPAR signaling towards the tumor thereby shifting the tumor phenotype to a more "malignant" one. However, when tumor patients are analyzed for long term survival, those with high levels of the inhibitor of the system, PAI-1 have a much worse prognosis than those with lower PAI-1 levels. This indicates that increased overall proteolysis alone cannot be made responsible for the adverse effects of the plasminogen activating system in tumors. Moreover, it becomes increasingly evident that components of the fibrinolytic system secreted by the tumor cells themselves are not solely responsible for a correlation between the plasminogen activating system and tumor malignancy; components of the plasminogen activating system secreted by stroma cells or cells of the immune system such as macrophages contribute also to the impact of fibrinolysis on malignancy. This review summarizes the evidence for the role of plasminogen activator inhibitor-1 in mediating the malignant phenotype and possible mechanism thereby trying to explain the "PAI-1 paradox in cancer" on a molecular level.     

Detection of mRNAs for urokinase-type plasminogen activator, its receptor, and type 1 inhibitor in giant cell tumors of bone with in situ hybridization.

Although giant cell tumor of bone (GCT) is generally considered to be an uncommon benign neoplasm, it can pursue an aggressive course with local recurrence and metastasis. Attempts to predict the biological behavior of GCT with histopathological parameters, however, have not been successful. The urokinase-type plasminogen activation system has been implicated in tumor invasion and metastasis and abnormalities of the components of this system have been found in several malignancies. In this study we postulated that the urokinase-type plasminogen activation system associated with bone destruction and local invasion is present in GCT. We therefore evaluated the mRNA levels for urokinase-type plasminogen activator (u-PA), urokinase-type plasminogen activator receptor (u-PAR), and plasminogen activator inhibitor type 1 (PAI-1) by using Northern blot analysis and in situ hybridization in four cases of GCT and spindle-shaped mononuclear cells at the 35th passage from a GCT. Our results showed that giant cell tumors of bone contained variable levels of u-PA, u-PAR, and PAI-1 mRNA, respectively, 2.3, 1.4, and 3.2 kb in size. In situ hybridization showed that u-PA, u-PAR, and PAI-1 mRNA were expressed in both the mononuclear cells and the osteoclast-like giant cells; the signal for u-PA mRNA in the spindle-shaped mononuclear cells was more intense than that in the osteoclast-like multinuclear giant cells. Some spherical mononuclear cells (macrophage-like cells) expressed high levels of PAI-1 mRNA in comparison with the spindle-shaped mononuclear cells. In addition, the 35th passaged spindle-shaped mononuclear cells were used to study the gene expression of u-PA during cell proliferation. The results showed that the level of u-PA mRNA increases after adding 10% fetal calf serum to quiescent cells. The induction was maximal at 16 hours and remained high during 48 hours of treatment. In conclusion, even though osteoclast-like cells are ultimately responsible for the bone resorption of GCT, the mononuclear neoplastic cells of GCT may also be involved in degradation of the extracellular matrix during invasive growth by facilitating the urokinase plasminogen activation system. In addition, our observation of upregulation of u-PA mRNA in spindle-shaped mononuclear cells after serum stimulation indicated that u-PA production may be linked to tumor growth.     

Upregulation of tissue inhibitor of metalloproteinases (TIMP)-2 promotes matrix metalloproteinase (MMP)-2 activation and cell invasion in a human glioblastoma cell line

Local invasiveness is a characteristic feature of glioblastoma that makes surgical resection nearly impossible and accounts in large part for its poor prognosis. To identify mechanisms underlying glioblastoma invasion and motility, we used Transwell invasion chambers to select for a more potently invasive subpopulation of U87MG human glioblastoma cells. The stable population of tumor cells (U87-C1) obtained through this in vitro selection process were three times more invasive than parental U87MG cells and demonstrated faster monolayer wound healing and enhanced radial motility from cell spheroids. This enhanced invasiveness was associated with an 80% increase in matrix metalloproteinase 2 (MMP-2) activation. No differences in expression levels of pro-MMP-2, membrane-type matrix metalloproteinase I (MT1-MMP), or integrin alphavbeta3 (mediators of MMP-2 activation) were detected. However, U87-C1 cells exhibited two-fold elevation of tissue inhibitor of metalloproteinases (TIMP)-2 mRNA and protein relative to parental cells. Exogenous addition of comparable levels of purified TIMP-2 to parental U87MG cells increased MMP-2 activation and invasion. Similarly, U87MG cells engineered to overexpress TIMP-2 at the same levels as U87-C1 cells also demonstrated increased MMP-2 activation, indicating that an increase in physiological levels of TIMP-2 can promote MMP-2 activation and invasion in glioblastoma cells. However, exogenous administration or recombinant overexpression of higher amounts of TIMP-2 in U87MG cells resulted in inhibition of MMP-2 activation. These results demonstrate that the complex balance between TIMP-2 and MMP-2 is a critical determinant of glioblastoma invasion, and indicate that increasing TIMP-2 in glioblastoma patients may potentially cause adverse effects, particularly in tumors containing high levels of MT1-MMP and MMP-2.     

去铁胺诱导的自噬增加线粒体内铁的含量并促进三阴性乳腺癌细胞 MDA-MB-231 的迁移

癌细胞转移是乳腺癌患者死亡的主要原因,铁代谢异常造成的铁超载能促进乳腺癌细胞的增殖和迁移。去铁胺（DFO）是被广泛使用的铁螯合剂,能抑制多种肿瘤细胞的增殖,降低雌激素受体（ER）阳性人类乳腺癌细胞中的铁含量,但增加了三阴性乳腺癌（TNBC）细胞中的铁含量。此外,DFO 可以增加线粒体内铁的含量,然而线粒体内铁的来源尚不清楚。该研究通过免疫荧光、蛋白质印迹及电感耦合等离子质谱,分析侵袭性乳腺癌 MDA-MB-231 和非侵袭性乳腺癌 MCF-7中的铁代谢和自噬相关蛋白,利用自噬抑制剂探究线粒体铁增多的机制。该研究发现,DFO 能通过诱导铁蛋白自噬促进线粒体内铁积累增加,从而促进 TNBC 细胞的上皮-间质转化与迁移。经过 DFO 处理,线粒体钙离子单向转运蛋白（MCU）和线粒体铁转运蛋白 1（Mfrn1）可能参与了铁从细胞质向线粒体的转运。该研究为临床中探寻新的靶向铁代谢治疗三阴性乳腺癌的方式提供了研究基础。     

Mycoplasma fermentans binds to and invades HeLa cells: involvement of plasminogen and urokinase

Adherence of Mycoplasma fermentans to HeLa cells followed saturation kinetics, required a divalent cation, and was enhanced by preincubation of the organism at 37 degrees C for 1 h in a low-osmolarity solution. Proteolytic digestion, choline phosphate, or anti-choline phosphate antibodies partially inhibited the adherence, supporting the notion that M. fermentans utilizes at least two surface components for adhesion, a protease-sensitive surface protein and a phosphocholine-containing glycolipid. Plasminogen binding to M. fermentans greatly increased the maximal adherence of the organism to HeLa cells. Anti-plasminogen antibodies and free plasminogen inhibited this increase. These observations suggest that in the presence of plasminogen the organism adheres to novel sites on the HeLa cell surface, which are apparently plasminogen receptors. Plasminogen-bound M. fermentans was detected exclusively on the cell surface of the infected HeLa cells. Nevertheless, plasminogen binding in the presence of the urokinase-type plasminogen activator (uPA) promoted the invasion of HeLa cells by M. fermentans. The latter finding indicates that the invasiveness of M. fermentans does not result from binding plasminogen but from activation of the bound plasminogen to plasmin. Cholesterol depletion and sequestration with beta-cyclodextrin and filipin, respectively, did not affect the capacity of M. fermentans to adhere, but invasion of HeLa cells by uPA-activated plasminogen-bound M. fermentans was impaired, suggesting that lipid rafts are implicated in M. fermentans entry.     

The invasive behaviour of prostatic cancer cells is suppressed by inhibitors of tyrosine kinase

Proteolytic enzymes, and especially urokinase plasminogen activator (uPA), play an important role in tumour invasion and metastasis. Previously we demonstrated that the production of urokinase plasminogen activator (uPA) was decreased by several tyrosine kinase inhibitors (TKI) in two prostatic carcinoma cell lines. The effect of the two TKI genistein and tyrphostin AG-1478 was investigated in the prostate carcinoma cell lines PC-3 and DU-145. A reconstituted basal lamina (Matrigel) was used as a migration barrier. The production of matrix metalloproteinases (MMP) was also measured. Roles of plasminogen and uPA were examined. Cell invasion was increased by plasminogen, but this enhanced cell migration was counteracted by TKI treatment. The increased cell invasion induced by plasminogen was decreased by at least 60% in both cell lines when alpha-2 anti-plasmin was added to the assay. Cells in the absence of plasminogen were not affected by TKI. External uPA failed to regenerate the decreased cell invasion caused by TKI. The production of MMP was inhibited by both TKI. Our results indicate a possible role of TKI as inhibitors of cancer cell invasion by inhibiting uPA and MMP production.     

Urokinase plasminogen activator and urokinase plasminogen activator receptor mediate human stem cell tropism to malignant solid tumors

Human neural and mesenchymal stem cells have been identified for cell-based therapies in regenerative medicine and as vehicles for delivering therapeutic agents to areas of injury and tumors. However, the signals required for homing and recruitment of stem cells to these sites are not well understood. Urokinase plasminogen activator (uPA) and urokinase plasminogen activator receptor (uPAR) are involved in chemotaxis and cell guidance during normal development and are upregulated in invasive tumors. Here we provided evidence that activation of uPA and uPAR in malignant solid tumors (brain, lung, prostate, and breast) augments neural and mesenchymal stem cell tropism. Expression levels of uPAR on human solid tumor cell lines correlated with levels of uPA and soluble uPAR in tumor cell-conditioned media. Cytokine expression profiles of these tumor-conditioned media were determined by protein arrays. Among 79 cytokines investigated, interleukin (IL)-6, IL-8, and monocyte chemoattractant protein-1 were the most highly expressed cytokines in uPAR-positive tumors. We provided evidence that human recombinant uPA induced stem cell migration, whereas depletion of uPA from PC-3 prostate cancer cell-conditioned medium blocked stem cell migration. Furthermore, retrovirus-mediated overexpression of uPA and uPAR in neuroblastoma (NB1691) cells induced robust migration of stem cells toward NB1691 cell-conditioned media, compared with media derived from wild-type NB1691 cells. We conclude that expression of uPA and uPAR in cancer cells underlies a novel mechanism of stem cell tropism to malignant solid tumors, which may be important for development of optimal stem cell-based therapies. Disclosure of potential conflicts of interest is found at the end of this article.     

Calcitonin receptor-stimulated migration of prostate cancer cells is mediated by urokinase receptor-integrin signaling

Abundance of calcitonin (CT) and calcitonin receptor (CTR) mRNA in primary prostate tumors positively correlates with tumor grade, and exogenously added CT increases the invasion of prostate cancer cell lines. We examined acute and chronic actions of CT on migration of highly metastatic PC-3M cells and poorly invasive LNCaP cells on several extracellular matrices in a spheroid disaggregation/migration assay. While PC-3M spheroids displayed maximum disaggregation/migration on vitronectin (VN), LNCaP spheroids preferred collagen but also migrated significantly on VN. Up-regulation of CT significantly enhanced disaggregation/migration of PC-3M spheroids on VN, but not on fibronectin. In contrast, down-regulation of CT, CTR, protein kinase A or urokinase-type plasminogen activator receptor (uPAR) led to amelioration of PC-3M spheroid disaggregation/migration. CT selectively increased surface activity of αvβ3 or α6β5 integrins in PC-3M and LNCaP cell lines, respectively, and uPAR-integrin association. Finally, either CT or urokinase could completely restore migration of CT-knock-down PC-3M spheroids. But, only forced expression of urokinase receptor coupled with exogenous addition of urokinase restored migration of CTR-knock-down spheroids. These results support our hypothesis that up-regulation of CT biosynthesis and activation of CT–CTR axis in primary prostate tumors may have direct relevance in their progression to the metastatic phenotype.     

Gossypol inhibits growth, invasiveness, and angiogenesis in human prostate cancer cells by modulating NF-κB/AP-1 dependent- and independent-signaling

Although previous studies demonstrated anticancer activities of gossypol through the induction of apoptosis, the molecular mechanism(s) responsible for the inhibitory effects of gossypol on the metastatic behavior of cancer cells remain to be elucidated. Here, we show that gossypol inhibits growth of human prostate cancer cells through the modulation of cell cycle regulatory proteins. We also demonstrate that gossypol inhibits invasive behaviors (adhesion, migration, and invasion) and angiogenesis. These effects are mediated by the suppression of AP-1 and NF-κB activity, resulting in the inhibition of secretion of urokinase plasminogen activator and vascular endothelial growth factor, and the down-regulation of expression of chemokine receptor 4 in PC3 cells. In summary, our data suggest that gossypol could have potential therapeutic effect for the treatment of invasive prostate cancer.     

uPA系统与神经胶质瘤局部侵袭

uPA系统包括尿激酶型纤溶酶原激活物（urokinase plasminogen activator, uPA）、 尿激酶型纤溶酶原激活物受体（urokinase plasminogen activation receptor, uPAR）和纤溶酶原激活物抑制剂(plasminogen activator inhibitor, PAI),它们参与了多种人类恶性肿瘤的局部侵袭和转移,是目前肿瘤治疗重要的分子靶点。uPA能激活纤溶酶原降解细胞外基质与基底膜,uPAR则能显著提升uPA的激活纤溶酶原的功能,两者结合能够增强肿瘤的侵袭性与转移能力。PAI主要通过促进血管内皮生长因子（vascular endothelial growth factor,VEGF）的表达,促进新生血管的形成,从而促进肿瘤的局部侵袭,但PAI又可通过抑制uPA-uPAR复合体的生物学活性来抑制肿瘤的局部侵袭。神经胶质瘤是最常见的颅内肿瘤,很少转移到颅外,局部侵袭是其预后不良的主要原因。近年来发现uPA系统的表达水平与神经胶质瘤的恶性程度呈正相关。本文综述了uPA系统对神经胶质瘤局部侵袭的影响及其在治疗中的意义。     

Up-regulation of urokinase and urokinase receptor genes in malignant astrocytoma.

To understand the role of urokinase (u-PA) and the urokinase receptor (u-PAR) in malignant astrocytoma cell invasion of normal brain, astrocytic expression of u-PAR and u-PA mRNAs were analyzed by riboprobe in situ hybridization in astrocytoma and non-neoplastic brain biopsies. In eight of eight malignant astrocytomas (glioblastomas), u-PAR and u-PA mRNA expression was demonstrated, whereas in seven non-neoplastic brain biopsies, u-PAR and u-PA mRNAs were not expressed. In one of four low grade and all anaplastic astrocytomas u-PAR mRNA was expressed, although u-PA mRNA was undetectable. Consistent with the mRNA detection, u-PAR and u-PA proteins were expressed by malignant astrocytes in five of five glioblastoma biopsies. To study the tumor margin, U-251MG glioblastoma cells were propagated intracerebrally in a severe combined immunodeficient mouse xenograft (28 days), and u-PA mRNA was found to localize predominantly to the leading tumor edge, whereas u-PAR mRNA was expressed throughout the tumor. Furthermore, adherent human U-251MG glioblastoma cells in vitro expressed u-PAR and u-PA proteins, which localized to sites of integrin alpha nu beta 3 cell-matrix contacts. These data indicate that co-expression of u-PAR and u-PA mRNAs and proteins marks the malignant astrocyte phenotype and that u-PA bound to u-PAR may play a role in glioblastoma cell invasion of normal brain by virtue of its expression at the leading tumor edge.     

整合素β1及纤连蛋白、层粘连蛋白对胶质瘤细胞浸润性的影响

目的 探讨整合素β1和纤连蛋白（FN）、层粘连蛋白（LN）对人胶质瘤浸润性的影响和作用机制。方法 以U251人胶质母细胞瘤（U251MG）细胞为研究对象,通过细胞黏附实验、迁移实验和体外侵袭实验,检测整合素β1及LN、FN对人恶性胶质瘤细胞黏附、迁移和转移能力的影响。通过荧光染色结合激光扫描共聚焦显微镜观察和扫描电镜方法,观察细胞微丝数量、分布和细胞表面伪足情况,比较整合素β1及FN、LN对微丝骨架的影响。结果 （1）FN对U251MG细胞黏附能力无明显影响,但抗整合素β1抗体可减少U251MG细胞的黏附数量（P〈0．01）;LN增加U251MG细胞黏附能力（P〈0．01）,抗整合素β1抗体对此作用影响较小。（2）抗整合素β1抗体减弱U251MG细胞在FN的运动、迁移能力（P〈0．05）。（3）U251MG细胞内可见清晰的微丝结构,FN、LN使细胞内纤维型肌动蛋白（F-actin）形成束状纤维,粗壮而密集;抗整合素B1抗体处理的细胞内,难以见到清晰的细胞微丝骨架,并常见大量絮团状的F-actin。（4）扫描电镜观察显示,FN、LN使细胞表面的伪足数量明显增加,而抗整合素β1抗体使细胞伪足数量明显减少,甚至消失。（5）FN和抗整合素β1抗体对U251MG细胞的体外侵袭能力无明显影响;LN可促进U251MG细胞的体外侵袭能力,抗整合素β1抗体可抑制这种作用（P〈0．01）。结论 （1）U251MG细胞通过整合素β1和FN相互作用,改变细胞微丝骨架、伪足结构和数量而促进U251MG细胞的运动、迁移能力。（2）整合素β1参与了LN介导的U251MG细胞体外侵袭作用。     

Vascular endothelial growth factor, epidermal growth factor and fibroblast growth factor-4 and -10 stimulate trophoblast plasminogen activator system and metalloproteinase-9

Trophoblast invasion, accompanied by degradation of extracellular matrix, is crucial to normal pregnancy development, whereas shallow placental invasion and implantation likely plays a role in the subsequent development of pre-eclampsia. The growth factors vascular endothelial growth factor (VEGF), epidermal growth factor (EGF) and fibroblast growth factor (FGF) are placental growth factors that activate degradation of extracellular matrix. We determined the effect of VEGF, EGF, FGF-2, FGF-4 and FGF-10 on the plasminogen activator system of first trimester cytotrophoblasts cultured in vitro. We studied the activity of urokinase plasminogen activator (uPA), its inhibitor plasminogen activator inhibitor-1 (PAI-1), and 92 kDa gelatinase-B (matrix metalloproteinase-9, MMP-9), using protein gel and reversed gel zymography. The expression pattern of FGF-4 and FGF-10 in human placental sections was determined by immunohistochemistry. FGF-4 was expressed in first trimester villi stroma, primarily in endothelial cells. FGF-10 expression was localized to first trimester extravillous trophoblasts. VEGF, EGF, FGF-4 and FGF-10, but not FGF-2, stimulate the activity of trophoblast uPA, PAI-1 and MMP-9. These results support the hypothesis that specific growth factors modulate the invasive potential of trophoblasts, and therefore may play an important role in early placental development. Our findings may contribute to the understanding of the pathophysiology of diseases associated with shallow placentation, such as pre-eclampsia.     

Expression of urokinase-type plasminogen activator receptor (uPAR) in primary central nervous system neoplasms.

The cellular receptor for urokinase-type plasminogen activator receptor (uPAR) is a member of the glycosylphosphatidylinositol (GPI) anchored protein family. It is a specific cell surface receptor for its ligand, urokinase-type plasminogen activator, which catalyzes the formation of plasmin from plasminogen to generate the proteolytic cascade and leads to the breakdown of the extracellular matrix. uPAR has been shown to correlate with a propensity to tumor invasion and metastasis in several types of non-central nervous system tumors. In this study, the authors examined the immunohistochemical expression of uPAR in 65 primary brain tumors (5 pilocytic astrocytomas, 5 diffuse astrocytomas, 6 anaplastic astrocytomas, 8 glioblastomas, 5 oligodendrogliomas, 4 oligoastrocytomas, 6 anaplastic oligoastrocytomas, 4 gangliogliomas, 4 ependymomas, 5 medulloblastomas, 6 schwannomas, 5 meningiomas, 2 atypical meningiomas). The specimens were evaluated for intensity of immunostaining (0-3 scale), cellular localization of staining, and specific or unique patterns of staining. Some degree of uPAR expression was observed in all tumors. A significant positive correlation (P = 0.0006) between tumor grade and staining intensity was identified within the astrocytoma/glioblastoma subgroup, suggesting a possible correlation with anaplastic change and propensity to tumor invasion. Expression of uPAR in nonmalignant, noninvasive tumors such as schwannoma and meningioma suggests that uPAR may have other biologic functions in addition to promotion of tumor invasion.     

Transforming growth factor-beta 1 is a potent inducer of plasminogen activator inhibitor type-1 in human glioblastoma and carcinoma cell lines

Transforming growth factor-beta 1 has been shown to suppress the urokinase activity in the glioblastoma cell line T-MG1 and the carcinoma cell line T-CAR1. The molecular mechanisms behind the decrease in the proteolyic activity is shown to be at least partly due to increased synthesis of plasminogen activator inhibitor type-1 and not by decreased synthesis of urokinase.     

Role of hepatocyte growth factor/c-Met signaling in regulating urokinase plasminogen activator on invasiveness in human hepatocellular carcinoma: a potential therapeutic target

Hepatocyte growth factor (HGF), its transmembrane tyrosine kinase receptor (c-Met), and urokinase type plasminogen activator (uPA) is a key protein in the plasminogen activation system, which plays a proteolytically important role in the invasion and metastasis of various types of cancers. However, the mechanisms by which HGF/c-Met signaling mediates cancer progression and metastasis are unclear. This study was designed to investigate the roles of HGF/c-Met in tumor progression and metastasis in HepG2 and Hep3B hepatoma cell lines. Treatment with HGF increased c-Met phosphorylation in a dose-dependent manner. Activity of c-Met phosphorylation peaked 1–3 min after HGF treatment and then declined. HGF enhanced the protein level and the activity of uPA in HepG2 and Hep3B cells, and the uPAR protein level also increased in a HGF dose-dependent manner. HGF increased cell invasion through the Matrigel. A monoclonal antibody against human uPA receptor, mAb 3936, inhibited HGF-mediated tumor cell invasion in a dose-dependent manner. Down-regulation of uPA using uPA-shRNA induced a decrease in in vitro cell invasion. These results suggest that hepatoma cells express functional c-Met, which may provide a target for a therapeutic basis to interfere with metastases of cancer cells by inhibiting uPA system-mediated proteolysis.     

Angiogenesis-associated protein annexin II in breast cancer: selective expression in invasive breast cancer and contribution to tumor invasion and progression

Many advanced human tumors including breast cancer overproduce plasmin that is known to promote angiogenesis and metastasis. The mechanism of this effect is poorly understood. Here we report that annexin II, an endothelial co-receptor for tPA (tissue-type plasminogen activator) and plasminogen, was undetectable in normal and hyperplastic ductal epithelial cells and ductal complexes. By contrast, it was consistently expressed in invasive breast cancer and ductal carcinoma in situ (DCIS) indicating its involvement in breast cancer. Using the well established invasive/metastatic MDA-MB231 cell line and the noninvasive/nonmetastatic MCF-7 human breast cancer cell line, we investigated the mechanism by which annexin II regulates breast cancer progression and metastasis. Western and Northern blot analyses demonstrate selective expression of annexin II in MDA-MB231 cells but not in poorly invasive MCF-7 cells suggesting its participation in invasive breast cancer. Since annexin II is a receptor for plasminogen, we tested whether MDA-MB231 cells are capable of producing plasmin in vitro. MDA-MB231 cell membranes induced plasmin generation in a time-dependent manner while those from MCF-7 cells failed to convert plasminogen to plasmin. The generated plasmin is capable of degrading ECM consequently facilitating cell invasion and migration, biological functions required for angiogenesis and metastasis. Plasmin generation and its dependent invasion and migration can be blocked by a monoclonal antibody to annexin II or angiostatin, potent inhibitors of angiogenesis, breast cancer, and metastasis. Our findings indicate that annexin II-dependent localized plasmin generation by human breast cancer cells could contribute to angiogenesis and metastasis. These results suggest that annexin II may be an attractive target for new anti-angiogenic and anti-breast cancer therapies.     

Immunohistochemical expression of uPA, uPAR, and PAI-1 in breast carcinoma. Fibroblastic expression has strong associations with tumor pathology

The urokinase-type plasminogen activator (uPA) system has been implicated in tumor spread. We have used immunohistochemistry to examine three components of this system, ie, uPA, uPA receptor (uPAR), and plasminogen activator inhibitor-1 (PAI-1), in a pilot study on 142 cases of breast carcinoma. We wished to determine whether there were any relationships between expression of the proteins in either tumor cells or fibroblasts and clinical and pathological features. Strong uPA expression in each cell type was significantly related to high tumor grade (P = 0.013 and 0.008, respectively), and was more common in invasive than in in situ carcinomas (P < 0.0001). Fibroblastic expression of uPAR was only related to the presence of invasion (P < 0.0001). Strong PAI-1 expression in both cell types was seen in high-grade tumors (tumor cells, P = 0.012; fibroblasts, P < 0.001), but only fibroblastic expression was related to the presence of invasion (P = 0.042). Fibroblastic expression of both uPA and uPAR were positively correlated with tumor size. Although patients with strong fibroblastic expression of uPA showed a tendency toward a shorter time to relapse, none of the plasminogen activator proteins were significantly associated with relapse-free survival. These results suggest that strong expression of uPA, uPAR, and PAI-1 in fibroblasts rather than in tumor cells have the most impact on the clinical behavior of breast cancer. Larger prospective studies are needed to confirm these findings.     

uPAR与肿瘤的研究新进展

尿激酶型纤溶酶原激活物受体(urokinase plasminogen activator receptor,uPAR)是一个糖基磷脂酰肌醇锚定的蛋白质,高亲和力结合并激活尿激酶型纤溶酶原激活物(urokinase plasminogen activator,uPA),由此调节细胞表面蛋白水解活性。uPAR在几乎所有人类肿瘤中高表达,其高表达与增强肿瘤增殖、迁移、侵袭有关。本文对uPAR增强肿瘤趋向性、诱导上皮-间质转变与促进胞葬作用等新功能以及靶向uPAR治疗进展进行综述。     

Urokinase and Tissue Plasminogen Activators and Their Inhibitor PAI-1 in Human Tumors

The content of urokinase and tissue plasminogen activators and their inhibitor PAI-1 in tumors and histologically intact tissues from patients with breast, ovarian, and non-small-cell lung cancer was measured by enzyme immunoassay. The content of urokinase plasminogen activator and PAI-1 considerably increased in all malignant tumors, however the correlation between the expression of components of the plasminogen activation system and clinical morphological feature and prognosis of the disease depends on the type of tumor.