Molecular cloning, expression and purification of truncated midkine and its growth stimulatory activity on Wilms' tumor (G401) cells

Midkine (MK) is a heparin binding growth factor identified as a product of a retinoic acid-responsive gene; it is frequently expressed at high levels in many human carcinomas. Although the expression of the mRNA encoding truncated MK (tMK) in unique human cancer cells has been reported, the tMK polypeptide itself has not yet been identified. In order to clarify the biological role of tMK, recombinant tMK was expressed in Escherichia coli and purified. Recombinant tMK was purified as a single band in SDS-PAGE under reducing conditions showing an apparent molecular mass of 10 kDa. Purified recombinant tMK showed the same extent of proliferative activity towards Wilms' tumor (G401) cells as full length human MK. These results suggest that the structure of this recombinant tMK is same as the native polypeptide.     

Abnormal expression, highly efficient detection and novel truncations of midkine in human tumors, cancers and cell lines

We detected aberrant Midkine (MK) expressions in human insulinoma and pancreatic cancer tissues by immunohistochemistry, revealing its potential role in tumorigenesis/carcinogenesis. With a nested-touchdown PCR program we were able to detect the tMK in all human tumor/cancer tissues and cancer/tumor cell lines. Detection of MK in the peripheral cells and precancerous lesions implies its potential for early cancer/tumor diagnosis. Furthermore, we have discovered two novel truncations of the MK, tMKB and tMKC, respectively, in the disease specimens. Our data not only provide an efficient methodology potentially for clinical application but also shed light on the molecular mechanism underlying the role for MK in tumorigenesis/carcinogenesis.     

Stimulation of anchorage-independent growth of human tumor cells by interleukin 1

Human peripheral blood monocytes and tumor-associated macrophages release a factor that enhances the clonal growth of a human epithelial tumor cell line (SW-13) in soft agar. We now demonstrate that purified interleukin 1 (IL-1) may account for part of this colony-stimulating activity. Purified IL-1 (0.5 to 8 units/ml) was added to SW-13 cells cultured in soft agar. IL-1 increased colony growth in a dose-dependent manner and did not inhibit colony formation at the highest doses tested. Other purified human monocyte products (alpha-interferon, tumor necrosis factor, transforming growth factor beta, fibronectin) did not stimulate colony growth. Antibody to IL-1 only partially inhibited the ability of monocyte-conditioned medium to stimulate SW-13 colony growth. This antibody did, however, completely inhibit the ability of purified IL-1 to support the growth of SW-13 colonies in soft agar. IL-1 increased growth of quiescent SW-13 cells cultured in monolayers as assessed by tritiated thymidine incorporation assays. The results of this study indicate that IL-1 can enhance clonogenic growth of an epithelial cell line in soft agar. However, other uncharacterized activities in monocyte conditioned medium also promote colony growth. These studies add to an increasing body of evidence indicating that inflammatory products play a role in maintaining the transformed phenotype.     

Potent inhibitory effect of the cyclolignan picropodophyllin (PPP) on human adrenocortical carcinoma cells proliferation

Adrenocortical carcinoma (ACC) is a very aggressive tumor with a poor prognosis. Available treatments for this type of cancer are far from being satisfactory. The IGF signalling pathway represents an important mechanism for ACT growth and constitutes a relevant therapeutic target. We investigated the effect of picropodophyllin (PPP), a member of the cyclolignan family and a new inhibitor of IGF-1R, on proliferation of human adrenocortical cell lines H295R and SW-13. PPP inhibits proliferation and induces an important accumulation in G2/M phase and apoptosis of H295R and SW-13 cells. Our data suggest that PPP may be a promising candidate for drug development for adrenocortical carcinoma.     

Antagonists of bombesin/gastrin-releasing peptide inhibit growth of SW-1990 human pancreatic adenocarcinoma and production of cyclic AMP

We investigated the effects of bombesin/GRP antagonists RC-3095 and RC-3940-II on the growth of SW-1990 human pancreatic adenocarcinoma cells xenografted into nude mice or cultured in vitro. Nude mice implanted with SW-1990 tumors received s.c. injections of RC-3095 and RC-3940-II or the vehicle (control) for 28 days. Chronic administration of RC-3940-II inhibited the growth of SW-1990 tumors, as shown by a reduction in tumor volume during the treatment and a significant increase in tumor doubling time. RC-3940-II decreased final tumor volume by 57.7% and tumor growth rate by 65%. Final tumor weights in mice treated with RC-3940-II were 75% lower than in controls. Treatment with RC-3095 induced smaller, and not significant, decreases in tumor volume and weight. In cell cultures, both RC-3095 and RC-3940-II effectively inhibited the proliferation of SW-1990 cells, inducing a dose- and time-dependent decrease in the number of cells. RC-3940-II again suppressed in vitro growth of SW-1990 cells more effectively than RC-3095. After 72 hr of culture, RC-3940-II and RC-3095 at I μM concentrations decreased cell numbers by 45.7% and 27.7%, respectively. The estimated EC₅₀ value for RC-3940-II was I nM. When SW-1990 cells were cultured in the presence of I nM and 10 nM RC-3095 for 72 hr, cAMP levels in the incubation medium were decreased to 77.3% and 26.9% of the control value. Our results indicate that bombesin/GRP antagonist RC-3940-II can inhibit the proliferation of SW-1990 human pancreatic adenocarcinoma cells in vivo and in vitro. Our findings also suggest that this effect may involve the intracellular cAMP pathway.     

Progranulin (PC-cell-derived growth factor/acrogranin) regulates invasion and cell survival

Progranulin (pgrn; PC-cell-derived growth factor, epithelin precursor, or acrogranin) has been identified recently as an autocrine regulator of tumorigenesis in several cancer cells including SW-13 adrenal carcinomas and some breast cancers, but how pgrn promotes tumor progression is not well understood. SW-13 cells do not form tumors in nude mice but become highly tumorigenic when their pgrn expression is elevated, and this provides a useful model in which to investigate the role of pgrn in tumorigenesis. Here we show that, in SW-13 cells, the level of pgrn expression is a major determinant of the intrinsic activity of the mitogen-activated protein kinase, phosphatidylinositol 3'-kinase, and focal adhesion kinase signaling pathways. Pgrn stimulates the invasion of SW-13 cells across Matrigel-coated filters, increases the expression of matrix metalloproteinase 13 and 17, protects against anoikis, and overcomes the inhibition of cell growth imposed on SW-13 cells by interstitial type-I collagen. Inhibition of the mitogen-activated protein kinase and phosphatidylinositol 3'-kinase signaling pathways impairs each of the pgrn-dependent biological responses tested, but to different extents. The ability of pgrn to stimulate cell division, invasion, and survival demonstrates that pgrn regulates multiple steps in carcinomal progression, and suggests that the pgrn system may be a possible future therapeutic target.     

Introduction of midkine gene into human bladder cancer cells enhances their malignant phenotype but increases their sensitivity to antiangiogenic therapy.

PURPOSE: Midkine (MK) is a member of a family of heparin-binding growth factors, which was reported to have an important role in angiogenesis. Although MK was reported to be associated with bladder cancer progression, the functional significance of MK expression in bladder cancer progression has not been elucidated. The objectives of this study were to determine whether overexpression of MK in bladder cancer cells enhances their malignant potential and to evaluate the inhibitory effect of the antiangiogenic agent TNP-470 on the growth of MK-overexpressing bladder cancer cells in vivo. EXPERIMENTAL DESIGN: We introduced the MK gene into human bladder cancer UM-UC-3 cells that do not secrete a detectable level of MK protein and generated the MK-overexpressing cell line UM-UC-3/MK. The biological activity of secreted MK was evaluated using a human umbilical vein endothelial cell proliferation assay. To investigate the in vivo effects of MK overexpression on tumor growth, each cell line was injected s.c. and orthotopically into nude mice. To evaluate the therapeutic effects of the antiangiogenic agent, mice were given TNP-470 after s.c. injection of each cell line. The microvessel density of tumors was quantitated by immunohistochemistry of CD31. RESULTS: The heparin affinity-purified conditioned media of UM-UC-3/MK cells significantly enhanced human umbilical vein endothelial cell proliferation. MK expression had no effect on in vitro growth but conferred a growth advantage on both s.c. and orthotopic tumors in vivo. Furthermore, enhanced tumor growth was closely associated with increased microvessel density. Significant inhibition of tumor growth by TNP-470 treatment was observed only in UM-UC-3/MK tumors and not in control tumors. CONCLUSIONS: We demonstrated that overexpression of the MK gene causes an increase in the angiogenic activity of cells through vascular endothelial cell growth, resulting in enhanced malignant potential of human bladder cancer cells. Moreover, the present findings suggest that TNP-470 could be used as a novel therapeutic adjunct to conventional agents for patients with advanced bladder cancer overexpressing MK.     

Tumor growth dependent on Kaposi's sarcoma-derived fibroblast growth factor inhibited by pentosan polysulfate.

A neoangiogenic response is critical for the unrestricted growth of solid tumors beyond a few millimeters in diameter. Release of adequate growth-stimulating activity from tumor cells is obviously required for the stimulation of blood vessel growth, and blockade of such stimulatory activity should repress tumor growth at the microscopic level. To test this hypothesis and to study appropriate inhibitors, we used a human adrenal cancer cell line (SW-13/K-fgf) engineered to secrete Kaposi's sarcoma-derived fibroblast growth factor (K-FGF), which we previously showed to induce growth of highly vascularized subcutaneous tumors in animals by autocrine and paracrine stimuli. In the present study, we tested different polysulfates for their selective inhibition of proliferation induced by K-FGF versus proliferation independent of K-FGF. Suramin and dextran sulfate showed slight selective inhibition of K-FGF-induced proliferation, ie, inhibition three- and five-fold greater, respectively, than the inhibition of proliferation independent of K-FGF. In contrast, heparin was inactive. The heparin analogue pentosan polysulfate (PPS), however, showed selective inhibition that was more than 2000-fold greater. The inhibitory effects of PPS on growth of SW-13/K-fgf cells, as well as endothelial cells, were fully reversible by an excess of added FGF. Daily intraperitoneal injections of PPS were tolerated well by athymic nude mice and prevented growth of subcutaneous SW-13/K-fgf tumor xenografts. PPS will be a useful tool to elucidate the effects of FGFs in vitro and in vivo and appears to be a prototype for the development of tumoricidal therapy based on targeting of growth factors.     

Antisense oligodeoxynucleotide targeted to Midkine, a heparin-binding growth factor, suppresses tumorigenicity of mouse rectal carcinoma cells.

Midkine (MK), a heparin-binding growth factor, is overexpressed in a wide range of human carcinomas and is believed to contribute to tumorigenesis and tumor progression. To develop an antitumor reagent, we designed a phosphorothioate antisense oligodeoxynucleotide molecule based on the secondary structure of MK mRNA. The antisense MK at the dosage of 5 microM suppressed MK production by CMT-93 mouse rectal carcinoma cells after cationic liposome-mediated transfection, to 13% of that in control cultures. The growth of CMT-93 cells and their colony formation in soft agar were inhibited by the addition of the antisense MK, whereas the control reagent, the sense MK, showed no effects. On s.c. injection into nude mice, CMT-93 cells transfected with the antisense MK formed tumors much smaller than those by control cells. Finally, untreated CMT-93 cells were inoculated to nude mice, and 7 days later the antisense MK (50 microM) with atelocollagen was directly injected into the preformed tumor region to evaluate the curative effect; the injection was repeated at the interval of 2 weeks. During the period of 10-41 days after initiation of therapy, the rate of increase of tumor volume treated with the antisense MK was found to be about 4.2-fold lower than that seen after treatment with the sense MK. On this occasion, proliferation of tumor cells as estimated by 5-bromodeoxyuridine incorporation was strongly inhibited, whereas angiogenesis was less affected. These findings strongly suggested the usefulness of MK antisense oligodeoxynucleotide as a new reagent for cancer therapy.     

An in vitro and in vivo study of antitumor effects of gossypol on human SW-13 adrenocortical carcinoma

The present study investigated the in vitro and in vivo antitumor effects of gossypol on human SW-13 adrenocortical carcinoma cells. In vitro gossypol concentrations greater than or equal to 0.5 microM reduced the growth rate of the SW-13 cells. Membrane microviscosity was determined by fluorescence polarization of diphenylhexatriene. The membranes of viable SW-13 cells exposed to gossypol became more rigid after a 1-day exposure to gossypol, the polarization constant, P, increasing from 0.229 to 0.352. Gossypol also increased the microviscosities of isolated mitochondrial and microsomal enriched membrane preparations. Tumor was also transplanted into nude mice by s.c. injection of SW-13 cells. A 1-week pretreatment period followed by daily administration of gossypol in which 30 mg gossypol/kg body weight/day was administered via orogastric tube delayed the onset of visible tumor in the subsequent weeks. Five weeks after transplantation, tumor prevalence rate was 95.8% in the control group and 54.5% in the gossypol-treated group. A second experiment, consisting of 12 weeks of gossypol treatment, reduced a preexisting 71% tumor prevalence to 54% while the tumor prevalence increased to 83% in the control group. This was accompanied by a 41.6% mortality in the control group versus 8.3% in the gossypol-treated group. These data suggest that gossypol may provide a beneficial effect in patients with adrenocortical carcinoma.     

Midkine induces the transformation of NIH3T3 cells.

Midkine (MK) is a heparin-binding growth factor and is frequently expressed at high levels in many human carcinomas. To investigate further the roles of MK in the regulation of cell growth, we introduced MK expression in NIH3T3 cells. A mixture of transfectants of an MK expression vector, but not a control vector, formed colonies in soft agar, showed an elevated cell number at confluence, and formed tumours in nude mice. An interesting characteristic of the transformed cells was that they became spontaneously detached from the culture dish substratum. In the transformed cells, MK was not only secreted, but also localized, in the perinuclear region as spots. The present data indicate that MK has the potential to transform NIH3T3 cells and suggest that overexpression of the MK gene may promote unregulated cell growth in vivo.     

间隙连接基因Cx43表达对肺癌细胞体内成瘤生长的抑制

目的探讨间隙连接基因表达和细胞通讯功能对肿瘤生长的抑制作用。方法以高转移性人肺癌ＰＧ细胞为材料,该细胞的间隙连接基因Ｃｘ４３表达抑制,细胞通讯功能缺陷。用Ｃｘ４３ｃＤＮＡ转染ＰＧ细胞,分离转染子克隆,与只转染空载体ｃＤＮＡ的对照组ＰＧ进行比较。用Ｎｏｒｔｈｅｒｎ分子杂交和染料传输方法检查间隙连接表达情况,并观察细胞在体外和裸鼠体内生长。结果空载体对照组与未转染组ＰＧ相似,Ｃｘ４３ｍＲＮＡ无表达,通讯功能缺陷,细胞生长快,在软琼脂内集落形成率高（１１．６％）,植入裸鼠体内２８天,平均瘤重３．４７ｇ。转染组细胞Ｃｘ４３ｍＲＮＡ表达升高,通讯功能增强,细胞生长慢,在软琼脂内集落形成率和在裸鼠体内生长速度明显低于对照组,抑制率分别为９０％和７５％。结论间隙连接基因Ｃｘ４３表达对肺癌细胞有抑瘤作用。     

Inhibitory effect of soluble platelet-derived growth factor receptor β on intraosseous growth of breast cancer cells in nude mice

Bone metastasis is a frequent complication of advanced breast cancer. On the basis of functional and molecular evidence, signaling mediated by the binding of platelet-derived growth factor (PDGF)-BB and -DD to PDGF receptor β (PDGFRβ) is critical for the survival and growth of metastatic breast cancer cells within the bone microenvironment. In this study, we propose a new approach to blocking PDGFRβ signaling using soluble PDGFRβ (sPDGFRβ) as a decoy receptor for PDGF-BB and -DD secreted from tumor cells and bone marrow stromal cells. A bone-seeking TNBCT/Bo cell line was established by in vivo selection from TNBCT human breast cancer cells, which are negative for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 protein expression. The TNBCT/Bo cells were transfected with a mammalian expression vector encoding the extracellular domain of PDGFRβ. A stable transfectant (TNBCT/Bo-sPDGFRβ) grew at a similar rate to that of control cells under normal culture conditions, although growth stimulation of human fibroblasts with PDGF-BB was neutralized by the culture medium from TNBCT/Bo-sPDGFRβ cells. Intratibial injection of TNBCT/Bo-sPDGFRβ cells into athymic nude mice resulted in a significant decrease in tumor incidence compared with control mice (P < 0.01). This attenuated growth correlated with decreased cancer cell proliferation, angiogenesis, and recruitment of stromal cells, and with an increase in the number of apoptotic cells. These findings suggest that sPDGFRβ is useful for the treatment of breast cancer bone metastasis.     

Production and characterization of a bacterial single-chain Fv fragment specific to human truncated midkine

The production (and characterization) of a monoclonal antibody against human truncated midkine (tMK), and the detection of tMK in G401 cells, a Wilms' tumor cell line, as well as in Wilms' tumor patient specimens, have been reported (Paul et al., Cancer Lett. 163 (2001) 245-251). Here we report the molecular cloning and expression of this monoclonal antibody as a single-chain Fv fragment (scFv) in Escherichia coli. The scFv protein, purified by immobilized metal affinity chromatography, showed a specific affinity to recombinant tMK and native tMK in G401 cells as detected by enzyme-linked immunosorbent assay and immunofluorescence microscopy, respectively. The binding of this protein to recombinant tMK was competitive with the parental monoclonal antibody. These results suggest that this scFv can also be used for Wilms' tumor detection.     

5-脂氧合酶活化蛋白抑制剂MK886治疗裸鼠人结肠癌移植瘤的实验

 目的观察5-脂氧合酶活化蛋白(FLAP)抑制剂MK886对裸鼠人结肠癌移植瘤的治疗作用,并探讨其抗肿瘤的可能机制。方法以HT-29人结肠癌细胞制备裸鼠人结肠癌移植瘤模型,15只荷瘤裸鼠随机分为三组,治疗组以MK886溶解在二甲基亚砜中投药,两对照组分别给以二甲基亚砜及不作任何治疗。治疗期间观察肿瘤生长情况,治疗结束后处死裸鼠并取瘤,测量肿瘤体积重量,用免疫组化方法检测肿瘤微血管密度,用TUNEL法检测肿瘤细胞凋亡情况。结果15只裸鼠全部成瘤,且实验过程中无一裸鼠死亡;通过测量瘤体积、瘤重结果显示,MK886可抑制人结肠癌裸鼠皮下移植瘤的生长;实验还证实MK886对人结肠癌裸鼠皮下移植瘤具有诱导肿瘤细胞凋亡及抗血管生成作用。结论MK886对于裸鼠人结肠癌移植瘤具有明显的治疗效果,MK886可能通过诱导肿瘤细胞凋亡、抑制肿瘤微血管形成等机制控制人结肠癌的生长。     

Escape from microenvironmental control and progression of intraepithelial neoplasia

We previously reported that normal human keratinocytes controlled neoplastic progression of tumor cells at an early stage of transformation in stratified squamous epithelium. We now studied if cells at a more advanced stage of transformation were also subject to such microenvironmental control. To accomplish this, 3D human tissues that mimic intraepithelial neoplasia were fabricated by mixing genetically marked (beta-gal), early-stage (II-4 cells) or advanced-stage (SCC13) transformed keratinocytes with normal keratinocytes, and tumor cell fate and phenotype were monitored in organotypic culture and after surface transplantation to nude mice. In vivo, SCC13 cells evaded local growth suppression to undergo connective tissue invasion at significantly lower tumor cell volumes (12:1, 50:1 normal:tumor cells) than II-4 cells. This behavior was explained by the growth suppression of II-4 cells, while advanced-stage tumor cells escaped this control and continued to undergo clonal expansion in mixed cultures to form large, intraepithelial tumor clusters. These communities of tumor cells underwent autonomous growth that was associated with altered expression of markers of differentiation (keratin 1) and cell-cell communication (connexin-43). Furthermore, significantly greater numbers of SCC13 cells expanded into a basal position after low-calcium stripping of suprabasal cells of mixed cultures compared to II-4 cells, suggesting that expansion of these cells enabled tumor cell invasion after transplantation. These findings demonstrated that early tumor development in human stratified squamous epithelium required escape from microenvironmental growth control that was dependent on the transformation stage of intraepithelial tumor cells during the premalignant stage of cancer progression.     

Matriptase activates stromelysin (MMP-3) and promotes tumor growth and angiogenesis

Matriptase/MT-SP1, a type II membrane serine protease widely expressed in normal epithelial cells and human carcinoma cells, is thought to be involved in cancer progression. To clarify this possibility, we overexpressed exogenous matriptase in the human stomach cancer cell line AZ521. In vitro, the matriptase transfectant (Mat-AZ521) and the control transfectant (Mock-AZ521) showed a similar growth rate, although the saturation cell density was significantly higher with the Mat-AZ521. When implanted into nude mice subcutaneously or intraperitoneally, Mat-AZ521 cells grew faster and produced much larger solid tumors than Mock-AZ521 cells. The overexpression of matriptase in AZ521 cells shortened the survival time of tumor-bearing mice. Histological analysis showed that both the number and the size of blood vessels in tumor tissues were significantly higher in the Mat-AZ521 tumors than the Mock-AZ521 ones. Moreover, it was found that purified matriptase activated one of the important matrix metalloproteinases, stromelysin (MMP-3). These results suggest the possibility that the matriptase-dependent activation of MMP-3, as well as the direct activity of matriptase, promotes tumor growth and angiogenesis by enhancing extracellular matrix degradation in tumor cell microenvironments.     

Carcinogen-induced phenotypic alterations in mammary epithelial cells accompanying the development of neoplastic transformation

Epithelial cells isolated from the mammary glands of virgin Sprague-Dawley rats and treated with 7,12-dimethylbenz[a] anthracene (DMBA) acquire an indefinite life span and anchorage-independent (AI) growth and form carcinomas in athymic nu/nu mice. Epithelial cells separated from fibroblasts and lipocytes by density-gradient centrifugation after collagenase digestion of the fat pads are grown in a hormone-supplemented medium. Control mammary epithelial cells survived approximately 30 days. After 2 days in culture, the mammary epithelial cells were treated with DMBA (1 microM) for 24 hr allowing for maximum oxidative metabolism of the hydrocarbon. DMBA-treated cells acquired an extended life span and grew in AI medium; however, in most cases, they were nontumorigenic and eventually ceased dividing. A pool of mammary epithelial cells, ME 10CL1, treated with DMBA has grown indefinitely, exhibited AI growth, and after 195 days in culture formed adenocarcinomas when 5 X 10(6) cells were injected into athymic nu/nu mice. When the tumor promoter, 12-O-tetra-decanoylphorbol-13-acetate (100 ng/ml), was added to another pool (ME 11CL2) of DMBA-treated mammary epithelial cells which had been in culture for 110 days, an irreversible increase in cell growth rate and a significant morphological alteration resulted. The 12-O-tetradecanoylphorbol-13-acetate-treated cells also formed colonies in AI medium after 140 days and poorly differentiated carcinomas in athymic nu/nu mice. Inhibition of tumor cell proliferation by tamoxifen is consistent with the mammary origin of the epithelial cells and suggests the presence of a viable estrogen receptor. The results demonstrate in vitro neoplastic transformation of rat mammary epithelial cells by DMBA or promotion of DMBA-initiated cells by 12-O-tetradecanoylphorbol-13-acetate resulting in two different epithelial tumor cell lines.