A Kunitz-type protease inhibitor,bikunin, inhibits ovarian cancer cell invasion by blocking the calcium-dependent transforming growth factor-beta 1 signaling cascade

Bikunin is a Kunitz-type protease inhibitor, acting at the level of tumor invasion and metastasis. The goal of this study was to investigate the effect of bikunin-dependent signal transduction involved in the expression of a plasminogen activator (PA) system and invasion. We report here the following. 1) The human ovarian cancer cell line HRA produced secreted and cell-associated urokinase-type PA (uPA) and PA inhibitor type 1 (PAI-1). The plasma membrane of the cells showed enzymatically active uPA even in the presence of high level of PAI-1, as measured by zymography, Western blot, chromogenic assay, enzyme-linked immunosorbent assay, and Northern blot. 2) HRA cells leading to invasion are induced through up-regulation of uPA expression. 3) HRA cells specifically released transforming growth factor-beta type 1 (TGF-beta1) participating in an autocrine/paracrine regulation of cell invasion. 4) Elimination of endogenous TGF-beta1 could induce change in uPA/PAI-1 expression, which could in turn modify the invasive behavior of the cells. 5) The constitutive expression of TGF-beta1 as well as up-regulation of the PA system observed in HRA cells was inhibited by preinoculation of the cells with bikunin or calcium channel blocker SK&F 96365 but not with nifedipine or verapamil, with an IC(50) of approximately 100 nm for bikunin or approximately 30 microm for SK&F 96365, respectively, as measured by enzyme-linked immunosorbent assay. Bikunin showed no additive effect on SK&F 96365-mediated suppression of TGF-beta1 expression. 6) The ability of TGF-beta1 to elevate free intracellular Ca(2+), followed by activation of Src and ERK, was reduced by preincubation of the cells with bikunin. In conclusion, bikunin could inhibit the constitutive expression of TGF-beta1 and TGF-beta1-mediated, Src- and ERK-dependent, PA system signaling cascade, at least in part, through inhibition of a non-voltage-sensitive calcium channel.     

Genetic down-regulation of phosphoinositide 3-kinase by bikunin correlates with suppression of invasion and metastasis in human ovarian cancer HRA cells

Using a cDNA microarray analysis, we previously found that exposure of a highly invasive ovarian cancer cell line HRA with bikunin, a Kunitz-type protease inhibitor, or bikunin gene overexpression markedly reduced phosphoinositide kinase (PI3K) p85 gene expression, demonstrating that PI3K may be a candidate bikunin target gene. To clarify how reduced levels of PI3K may confer repressed invasiveness, we transfected HRA cells with PI3K p85 antisense-oligodeoxynucleotide (AS-ODN) and compared the properties of the transfected cells with those of parental cells and sense (S)-ODN cells. We have also demonstrated previously that transforming growth factor-beta1 (TGF-beta1) stimulates urokinase-type plasminogen activator (uPA)-dependent invasion and metastasis of HRA cells. Here, we show that 1) TGF-beta1 induced a rapid increase of the PI3K activity that was accompanied by increased expression (5-fold) of the uPA mRNA; 2) pharmacological inhibition of PI3K or AS-PI3K ODN transfection inhibited TGF-beta1-stimulated Akt phosphorylation; 3) both PI3K pharmacological inhibitors and forced expression of AS-PI3K ODN reduced TGF-beta1-stimulated uPA mRNA and protein expression by approximately 70% compared with controls; 4) concentrations of PI3K inhibitors, sufficient to inhibit uPA up-regulation, inhibited TGF-beta1-dependent HRA cell invasion; 5) the AS-PI3K ODN cells had a decreased ability to invade the extracellular matrix layer as compared with controls; and 6) when the AS-PI3K ODN cells were injected intraperitoneally into nude mice, the mice developed smaller intraperitoneal tumors and showed longer survival. We conclude that PI3K plays an essential role in promoting uPA-mediated invasive phenotype in HRA cells. Our data identify a novel role for PI3K as a bikunin target gene on uPA up-regulation and invasion.     

Inhibition of tumor invasion by genomic down-regulation of matriptase through suppression of activation of receptor-bound pro-urokinase

Urokinase-type plasminogen activator (uPA) degrades the extracellular matrix and plays critical roles in tumor invasion and metastasis. Matriptase, a membrane-bound serine protease, was shown to activate uPA in a uPA receptor-free, solution-based study. We now investigate whether matriptase affects activation of receptor-bound uPA and contributes to the invasiveness of HRA human ovarian cancer cells in vitro and tumor behavior in nude mice. Here we show the following. 1) uPA expression was effectively stimulated by TGF-beta1 in HRA cells. 2) Antisense (AS)-matriptase transfection achieved a marked inhibition of receptor-bound pro-uPA activation without altering expression of uPA and uPA receptor mRNA and proteins, irrespective of whether cells were stimulated with TGF-beta1. 3) Tumor cell receptor-bound pro-uPA could be efficiently cleaved by matriptase to generate enzymatically active two-chain uPA. Thus, matriptase can substitute for plasmin in the proteolytic activation of pro-uPA to enzymatically active uPA. 4) The AS-matriptase-treated cells had a decreased ability to invade an extracellular matrix layer, as compared with control cells. 5) When the AS-matriptase-treated cells were injected intraperitoneally into nude mice, the mice developed smaller tumors. Our data identify a novel role for matriptase for activation of receptor-bound uPA.     

Suppression of urokinase receptor expression by bikunin is associated with inhibition of upstream targets of extracellular signal-regulated kinase-dependent cascade.

Our laboratory showed that bikunin, a Kunitz-type protease inhibitor, suppresses 4beta-phorbol 12-myristate 13-acetate (PMA)- or tumor necrosis factor-alpha (TNFalpha)-induced urokinase-type plasminogen activator (uPA) expression in different cell types. In addition to its effects on protease inhibition, bikunin could be modulating other cellular events associated with the metastatic cascade. To test this hypothesis, we examined whether bikunin was able to suppress the expression of uPA receptor (uPAR) mRNA and protein in a human chondrosarcoma cell line, HCS-2/8, and two human ovarian cancer cell lines, HOC-I and HRA. The present study showed that (a) bikunin suppresses the expression of constitutive and PMA-induced uPAR mRNA and protein in a variety of cell types; (b) an extracellular signal-regulated kinase (ERK) activation system is necessary for the PMA-induced increase in uPAR expression, as PD098059 and U0126, which prevent the activation of MEK1, reduce the uPAR expression; (c) bikunin markedly suppresses PMA-induced phosphorylation of ERK1/2 at the concentration that prevents uPAR expression, but does not reduce total ERK1/2 antigen level; (d) bikunin has no ability to inhibit overexpression of uPAR in cells treated with sodium vanadate; and (e) we further studied the inhibition of uPAR expression by stable transfection of HRA cells with bikunin gene, demonstrating that bikunin secretion is necessary for inhibition of uPAR expression. We conclude that bikunin downregulates constitutive and PMA-stimulated uPAR mRNA and protein possibly through suppression of upstream targets of the ERK-dependent cascade, independent of whether cells were treated with exogenous bikunin or transfected with bikunin gene.     

Suppression of urokinase-type plasminogen activator expression from human ovarian cancer cells by urinary trypsin inhibitor

Urinary trypsin inhibitor (UTI), a Kunitz-type protease inhibitor, efficiently inhibits tumor cell invasion and metastasis. We examined the effect of UTI on urokinase-type plasminogen activator (uPA) expression in ovarian cancer cell lines, HOC-I and HRA. By Northern blot, Western blot, ELISA, and zymographic analyses, we demonstrated that UTI inhibited the expression of uPA mRNA and protein in these cells in a time- and dose-dependent manner, independent of whether induction was triggered by phorbol ester. Monoclonal antibody 4G12, which inhibits UTI binding to the cells, produced a dose-dependent abrogation in UTI-mediated down-regulation of uPA expression. These data suggest that UTI significantly down-regulates tumor cell uPA mRNA expression and protein secretion, and that UTI binding to the cells is necessary to exert the UTI's action.     

The protease inhibitor bikunin,a novel anti-metastatic agent

Bikunin is a Kunitz-type protease inhibitor predominantly found in human amniotic fluid. In cancers, administration of bikunin may block tumor cell invasion by a direct inhibition of tumor cell-associated plasmin activity as well as by inhibiting urokinase-type plasminogen activator (uPA) expression at the gene and protein levels, possibly through suppression of CD44 dimerization and/or the MAP kinase signaling cascade. Treatment of cancer patients with bikunin may be beneficial in the adjuvant setting to delay the onset of metastasis development and/or in combination with cytotoxic agents to improve treatment efficacy in patients with advanced ovarian cancer.     

Systematic analysis of genes involved in oral cancer metastasis to lymph nodes

Oral cancer remains a deadly disease worldwide. Lymph node metastasis and invasion is one of the causes of death from oral cancer. Elucidating the mechanism of oral cancer lymph node metastasis and identifying critical regulatory genes are important for the treatment of this disease. This study aimed to identify differentially expressed genes (gene signature) and pathways that contribute to oral cancer metastasis to lymph nodes. The GSE70604-associated study compared gene profiles in lymph nodes with metastasis of oral cancer to those of normal lymph nodes. The GSE2280-associated study compared gene profiles in primary tumor of oral cancer with lymph node metastasis to those in tumors without lymph node metastasis. There are 28 common differentially expressed genes (DEGs) showing consistent changes in both datasets in overlapping analysis. GO biological process and KEGG pathway analysis of these 28 DEGs identified the gene signature CCND1, JUN and SPP1, which are categorized as key regulatory genes involved in the focal adhesion pathway. Silencing expression of CCND1, JUN and SPP1 in the human oral cancer cell line OECM-1 confirmed that those genes play essential roles in oral cancer cell invasion. Analysis of clinical samples of oral cancer found a strong correlation of these genes with short survival, especially JUN expression associated with metastasis. Our study identified a unique gene signature – CCND1, JUN and SPP1 – which may be involved in oral cancer lymph node metastasis.     

Transforming growth factor-beta1 produced by ovarian cancer cell line HRA stimulates attachment and invasion through an up-regulation of plasminogen activator inhibitor type-1 in human peritoneal mesothelial cells

The processes of ovarian cancer dissemination are characterized by altered local proteolysis, cellular proliferation, cell attachment, and invasion, suggesting that the urokinase-type plasminogen activator (uPA) and its specific inhibitor (plasminogen activator inhibitor type-1 (PAI-1)) could be involved in the pathogenesis of peritoneal dissemination. We showed previously that expression of uPA and PAI-1 in the human ovarian cancer cell line HRA can be down-regulated by exogenous bikunin (bik), a Kunitz-type protease inhibitor, via suppression of transforming growth factor-beta1 (TGF-beta1) up-regulation and that overexpression of the bik gene can specifically suppress the in vivo growth and peritoneal dissemination of HRA cells in an animal model. We hypothesize that the plasminogen activator system in mesothelial cells can be modulated by HRA cells. To test this hypothesis, we used complementary techniques in mesothelial cells to determine whether uPA and PAI-1 expression are altered by exposure to culture media conditioned by HRA cells. Here we show the following: 1) that expression of PAI-1, but not uPA, was markedly induced by culture media conditioned by wild-type HRA cells but not by bik transfected clones; 2) that by antibody neutralization the effect appeared to be mediated by HRA cell-derived TGF-beta1; 3) that exogenous TGF-beta1 specifically enhanced PAI-1 up-regulation at the mRNA and protein level in mesothelial cells in a time- and concentration-dependent manner, mainly through MAPK-dependent activation mechanism; and 4) that mesothelial cell-derived PAI-1 may promote tumor invasion possibly by enhancing cell-cell interaction. This represents a novel pathway by which tumor cells can regulate the plasminogen activator system-dependent cellular responses in mesothelial cells that may contribute to formation of peritoneal dissemination of ovarian cancer.     

Suppression of urokinase expression and tumor metastasis by bikunin overexpression [mini-review].

Bikunin (bik, also known as urinary trypsin inhibitor [UTI]), a Kunitz-type protease inhibitor, interacts with cells as a negative modulator of the invasive cells. Human ovarian cancer cell line, HRA, was treated with phorbol ester (PMA) in order to evaluate the effect on expression of urokinase-type plasminogen activator (uPA). Preincubation of the cells with bik reduced the ability of PMA to trigger the uPA expression at the gene level and at the protein level. We next asked whether the mechanism of inhibition of uPA expression by bik is due to interference with MAP kinase, since PMA could also activate a signaling pathway involving MEK/ERK/c-Jun-dependent uPA expression. When cells were preincubated with bik, we could detect suppression of phosphorylation of these proteins, demonstrating that bik markedly suppresses the cell motility possibly through negative regulation of MEK/ERK/c-Jun-dependent mechanisms, and that these changes in behavior are correlated with a coordinated down-regulation of uPA which is likely to contribute to the cell invasion processes. To clarify the role of bik on tumor metastasis, HRA cells were transfected with an expression vector harboring a cDNA encoding for human bik. Transfection of HRA with the bik cDNA resulted in five variants stably expressing functional bik and significantly reduced invasion, but not proliferation, adhesion, or migration relative to the parental cells. Animals with bik* transfectants induced reduced peritoneal dissemination and long term survival. These results suggest that transfection with the bik gene induces the suppression of tumor cell invasion and peritoneal dissemination, and can prolong survival. This pre-clinical animal model offers the possibility to explore gene therapy as a new treatment modality for ovarian cancer.     

TIS11D is a Candidate Pro-Apoptotic p53 Target Gene

A number of target genes for the tumor suppressor, p53, have been identified, however, the mechanisms that contribute to p53-dependent apoptosis remain to be fully elucidated. In a comprehensive screen for p53 target genes by differential display, we have identified TIS11D as a p53-inducible gene. Induction of TIS11D mRNA was confirmed by Northern Blot in response to p53 expression. Inducible expression of TIS11D resulted in inhibition of cell proliferation and apoptosis. These data suggest TIS11D as a candidate p53 target gene that may be part of the network of genes responsible for p53-dependent apoptosis.     

应用基因表达谱芯片从不同转移能力的 乳腺癌细胞中筛选转移相关基因

人乳腺癌细胞系 MCF-7 及其转移亚克隆 LM-MCF-7 为肿瘤转移分子机制的研究提供了细胞模型 . 应用基因芯片技术比较两种具有不同转移能力细胞系基因表达谱的差异,寻找乳腺癌转移相关基因 . 提取两种细胞总 RNA ,分别用 Cy5-dCTP 、 Cy3-dCTP 标记 LM-MCF-7 和 MCF-7 的 cDNA ,并与含有 21 329 个基因的芯片进行杂交并扫描,利用 GenePix Pro 4.0 图像分析软件处理数据判断基因是否在两个细胞中存在表达差异 . 经互换荧光标记物重复两次实验,共筛选出差异表达基因 67 个,其中 41 个在 LM-MCF-7 细胞中表达上调, 26 个在 LM-MCF-7 细胞中表达下调 . 应用实时定量 RT-PCR 对 7 个表达差异明显的基因进行了验证 . 生物信息学分析结果提示,上述发现的差异基因编码产物与细胞内信号转导、转录调节、应激反应、新陈代谢、发育、细胞运动、细胞凋亡和细胞粘连等功能有关 . 据文献报道,这些差异表达的基因中有 35 个与肿瘤有关,其中 9 个与乳腺癌转移有关, 6 个可能参与肿瘤浸润和转移过程 . 根据基因芯片检测的结果,从功能上对 LM-MCF-7 细胞和 MCF-7 细胞与细胞凋亡的关系进行了研究,发现具有高转移倾向的 LM-MCF-7 细胞与 MCF-7 细胞相比,抗凋亡能力较强 . 上述与肿瘤转移相关基因在肿瘤转移中的作用及其分子机理有待深入研究 .     

Protein and mRNA characterization in high and low metastasis adenoid cystic carcinoma cell lines

Metastasis and invasion, the important characteristics of malignant tumors, are closely associated with a series of changes in the expression of genes and proteins. In this study, we compare mRNA and protein expression in high and low metastasis adenoid cystic carcinoma cell lines by mRNA suppression subtractive hybridization and two-dimensional electrophoresis combined with peptide mass fingerprint analysis. 34 differentially expressed genes were obtained using suppression subtractive hybridization experiments including 6 highly expressed gene sequences in the high metastasis cell line, and 28 in the low metastasis cell line. RNA dot blot hybridization further confirmed the results after excluding false positives. For protein analysis, ten significantly different protein spots were detected using two-dimensional gel electrophoresis technique combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI- TOF-MS). The results then compare with the SWISS PROT database. These results suggest that high tumor metastasis of adenoid cystic carcinoma is associated with multiple genes whose function include angiogenesis, protein synthesis, signal transduction, modulation of cell cycle, molecular chaperones, and immune co-stimulating molecule. Moreover, the results of the phenotypic function-related expression mapping analysis at the mRNA and protein level revealed obvious complementarities, providing important clues for further study of the molecular mechanism of metastasis, metastasis control and possible targets for cancer gene therapy.     

Protein and mRNA characterization in high and low metastasis adenoid cystic carcinoma cell lines

Metastasis and invasion, the important characteristics of malignant tumors, are closely associated with a series of changes in the expression of genes and proteins. In this study, we compare mRNA and protein expression in high and low metastasis adenoid cystic carcinoma cell lines by mRNA suppression subtractive hybridization and two-dimensional electrophoresis combined with peptide mass fingerprint analysis. 34 differentially expressed genes were obtained using suppression subtractive hybridization experiments including 6 highly expressed gene sequences in the high metastasis cell line, and 28 in the low metastasis cell line. RNA dot blot hybridization further confirmed the results after excluding false positives. For protein analysis, ten significantly different protein spots were detected using two-dimensional gel electrophoresis technique combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI- TOF-MS). The results then compare with the SWISS PROT database. These results suggest that high tumor metastasis of adenoid cystic carcinoma is associated with multiple genes whose function include angiogenesis, protein synthesis, signal transduction, modulation of cell cycle, molecular chaperones, and immune co-stimulating molecule. Moreover, the results of the phenotypic function-related expression mapping analysis at the mRNA and protein level revealed obvious complementarities, providing important clues for further study of the molecular mechanism of metastasis, metastasis control and possible targets for cancer gene therapy.     

rab5a基因在肿瘤转移中的作用研究

为研究rab5a基因在肿瘤转移机制中的作用,将该基因稳定转染至低转移肺腺癌细胞系AGZY83-a中,采用Superarray肿瘤转移相关基因微芯片分析rab5a对肿瘤转移相关基因的表达影响,共获得了5个差异表达基因,rab5a基因促进s100a4的表达,同时抑制了nm23a、rac1、cst3、col4a2等基因的表达,并分别在RNA及蛋白水平进行验证,确认rab5a基因影响了肿瘤转移的多个途径,促进了肿瘤细胞转移能力增强。     

Serological cloning of PARIS-1: a new TBC domain-containing, immunogenic tumor antigen from a prostate cancer cell line.

Identifying immunogenic tumor antigens plays a critical role in developing efficient diagnostic and therapeutic strategies for treatment of cancer. Using a recently developed technology, serological identification of antigens by recombinant expression cloning (SEREX), we identified a total of 8 genes whose expression elicited antibody responses in prostate cancer patients. Of the 8 genes, 5 represented known genes in the GenBank database, 2 were previously uncharacterized genes, and 1 showed sequence homology to a mouse gene. The sequence feature and the expression of one of the novel genes, prostate antigen recognized and identified by SEREX (PARIS-1), are determined in this study. The PARIS-1 cDNA is 3257 bp in length and contains a complete open reading frame of 2751 bp encoding for a primary translation product of 917 amino acids. Using Northern blot hybridization assay, we detected a single species of approximately 3.3 kb PARIS-1 mRNA that is differentially expressed in prostate normal and cancer cells. Western blot analysis confirmed the expression of the PARIS-1 protein in these cells. Structure analysis revealed that PARIS-1 protein contains a TBC domain that is conserved in the family of cell cycle-regulatory and Rab GTPase-activating proteins (Rab-GAP). Thus, the PARIS-1 protein may play a role in regulation of cell differentiation and growth or represent a new member of the Rab-GAP family.     

Endothelial-specific intron-derived miR-126 is down-regulated in human breast cancer and targets both VEGFA and PIK3R2

Endothelial cells are the key components of vascular intima and play pivotal roles in vasculogenesis, angiogenesis, and tumor growth. Using Northern blot and real-time PCR, we confirmed that miR-126 and its host gene EGF-like domain 7 (EGFL7) were widely expressed in rat tissues but strictly expressed in endothelial cells. In mammals, miR-126 gene is embedded in intron7 of EGFL7. To explore the biogenesis of miR-126, plasmid EGFL7(126)-pEGFPc1 containing segment of exon7-intron7-exon8 of EGFL7 was constructed and expressed in 293T. Expression of spliced exon7-8 and excised mature miR-126 was detected by PCR and Northern blot. Knocking-down of endothelial endogenous miR-126 did not affect EGFL7 expression at mRNA or protein level. To investigate the possible roles of miR-126, PicTar, miRBase, miRanda, Bibiserv, and Targetscan were used to screen the targets. VEGFA and PIK3R2 were confirmed as the targets of miR-126 by luciferase reporter assay and Western blot. Interestingly, Northern blot and western blot showed that miR-126 was down-regulated in breast tumors where the VEGF/PI3K/AKT signaling pathway was activated. Introduction of miR-126 mimics into MCF-7 could effectively decrease VEGF/PI3K/AKT signaling activity. In summary, miR-126 was strictly expressed in endothelial cells and excised from EGFL7 pre-mRNA without affecting splicing and expression of its host gene. In addition, miR-126 could target both VEGFA and PIK3R2, and its expression was decreased in human breast cancer, implying that miR-126 may play a role in tumor genesis and growth by regulating the VEGF/PI3K/AKT signaling pathway.