[Show abstract][Hide abstract] ABSTRACT: Previous work showed that the adapter protein SH2B adapter protein 1beta (SH2B1) (SH2-B) binds to the activated form of the nerve growth factor (NGF) receptor TrkA and is critical for both NGF-dependent neurite outgrowth and maintenance. To identify SH2B1beta-regulated genes critical for neurite outgrowth, we performed microarray analysis of control PC12 cells and PC12 cells stably overexpressing SH2B1beta (PC12-SH2B1beta) or the dominant-negative SH2B1beta(R555E) [PC12-SH2B1beta(R555E)]. NGF-induced microarray expression of Plaur and Mmp10 genes was greatly enhanced in PC12-SH2B1beta cells, whereas NGF-induced Plaur and Mmp3 expression was substantially depressed in PC12-SH2B1beta(R555E) cells. Plaur, Mmp3, and Mmp10 are among the 12 genes most highly up-regulated after 6 h of NGF. Their protein products [urokinase plasminogen activator receptor (uPAR), matrix metalloproteinase 3 (MMP3), and MMP10] lie in the same pathway of extracellular matrix degradation; uPAR has been shown previously to be critical for NGF-induced neurite outgrowth. Quantitative real-time PCR analysis revealed SH2B1beta enhancement of NGF induction of all three genes and the suppression of NGF induction of all three when endogenous SH2B1 was reduced using short hairpin RNA against SH2B1 and in PC12-SH2B1beta(R555E) cells. NGF-induced levels of uPAR and MMP3/10 and neurite outgrowth through Matrigel (MMP3-dependent) were also increased in PC12-SH2B1beta cells. These results suggest that SH2B1beta stimulates NGF-induced neuronal differentiation at least in part by enhancing expression of a specific subset of NGF-sensitive genes, including Plaur, Mmp3, and/or Mmp10, required for neurite outgrowth.
[Show abstract][Hide abstract] ABSTRACT: We evaluated the capacity of estradiol (E(2)) to regulate PTHrP production, cell growth, tumor growth, and metastasis to the skeleton in breast cancer. In estrogen receptor (ER)-negative human breast cancer cells, MDA-MB-231, and cells transfected with full-length cDNA encoding ER (S-30), E(2) caused a marked decrease in cell growth and PTHrP production, effects that were abrogated by anti-E(2) tamoxifen. E(2) also inhibited PTHrP promoter activity in S-30 cells. For in vivo studies, MDA-MB-231 and S-30 cells were inoculated into the mammary fat pad of female BALB/c nu.nu mice. Animals receiving S-30 cells developed tumors of significantly smaller volume compared with MDA-MB-231 tumor-bearing animals. This change in tumor volume was reversed when S-30 cells were inoculated into ovariectomized (OVX) hosts. Inoculation of MDA-MB-231 cells into the left ventricle resulted in the development of lesions in femora and tibia as determined by x-ray analysis. In contrast, these lesions were significantly smaller in volume and number in animals inoculated with S-30, and this lower incidence was reversed in OVX animals. Bone histological analysis showed that the tumor volume to tissue volume ratio was comparable with that seen by x-ray. Immunohistochemical analysis showed that PTHrP production was inhibited in S-30 group and restored to levels comparable to that seen in MDA-MB-231 tumor-bearing animals when S-30 cells were inoculated in OVX animals. Collectively these studies show that E(2) production is inversely correlated with PTHrP production and that the growth-promoting effect of PTHrP has a direct impact on tumor growth at both nonskeletal and skeletal sites.
[Show abstract][Hide abstract] ABSTRACT: Hypercalcemia of malignancy (HCM) is the most common cause of elevated serum calcium in hospitalized patients and is found with varying frequency in patients with various types of cancer. Calcium homeostasis is finely regulated with day-to-day variations of less than 2%, and the development of HCM stems from various anomalies in homeostatic mechanisms. Hypercalcemia often produces a number of clinical symptoms, including alterations in central nervous system function, symptoms of dehydration and renal dysfunction. Whenever possible and appropriate, the goals of treatment of HCM should therefore be to return the patient to a euvolemic state, to normalize serum calcium and to treat the underlying cause. Almost invariably, however, HCM is a particularly adverse complication for patients with cancer and is almost always associated with a dismal prognosis. Older treatments like mithramycin and calcitonin have recently been replaced with newer management strategies, mostly involving bisphosphonates. These agents are potent inhibitors of osteoclasts which have been found to normalize serum calcium levels in a high proportion of patients with HCM. Emerging therapeutic approaches include monoclonal antibodies to parathyroid hormone related peptide (PTHrP), inhibition of RANK ligand through the use of a soluble form of its receptor osteoprotegerin, analogues of Vitamin D and selective inhibiton of the Ras-Raf-MAPK-ERK signalling pathway. In this article, we review the pathophysiology of tumour osteolysis leading to hypercalcemia of malignancy, and we discuss the physiological basis for the clinical symptoms of hypercalcemia. Past, current and future therapeutic approaches are also reviewed.
[Show abstract][Hide abstract] ABSTRACT: Parathyroid hormone (PTH)-related peptide (PTHrP) can modulate the proliferation and differentiation of a number of cell types including osteoblasts. PTHrP can activate a G protein-coupled PTH/PTHrP receptor, which can interface with several second-messenger systems. In the current study, we have examined the signaling pathways involved in stimulated type I collagen and alkaline phosphatase expression in the human osteoblast-derived osteosarcoma cells, MG-63. By use of Northern blotting and histochemical analysis, maximum induction of these two markers of osteoblast differentiation occurred after 8 h of treatment with 100 nM PTHrP-(1-34). Chemical inhibitors of adenylate cyclase (H-89) or of protein kinase C (chelerythrine chloride) each diminished PTHrP-mediated type I collagen and alkaline phosphatase stimulation in a dose-dependent manner. These effects of PTHrP could also be blocked by inhibiting the Ras-mitogen-activated protein kinase (MAPK) pathway with a Ras farnesylation inhibitor, B1086, or with a MAPK inhibitor, PD-98059. Transient transfection of MG-63 cells with a mutant form of Galpha, which can sequester betagamma-subunits, showed significant downregulation of PTHrP-stimulated type I collagen expression, as did inhibition of phosphatidylinositol 3-kinase (PI 3-kinase) by wortmannin. Consequently, the betagamma-PI 3-kinase pathway may be involved in PTHrP stimulation of Ras. Collectively, these results demonstrate that, acting via its G protein-coupled receptor, PTHrP can induce indexes of osteoblast differentiation by utilizing multiple, perhaps parallel, signaling pathways.
AJP Endocrinology and Metabolism 10/2001; 281(3):E489-99. · 4.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vitronectin (VN) and pro-urokinase (pro-uPA) stimulated migration of rat smooth muscle cells in a dose-dependent and additive way, and induced motile-type changes in cell morphology together with a complete reorganization of the actin filaments and of the microtubules. All these effects were inhibited by pertussis toxin, or by antibodies directed against the urokinase receptor (uPAR) or against the VN receptor alpha(v)beta(3) suggesting that an association between the two receptors is required to mediate both signals. Investigation of the signaling pathways showed that increasing the intracellular cAMP resulted in a selective inhibition of VN-induced cell migration. On the other hand, PD 98059, an inhibitor of MEK, differentially inhibited the pro-uPA- but not the VN-induced cell migration. Phosphorylation and nuclear translocation of Erk by pro-uPA was directly observed. We conclude that the signaling pathways of pro-uPA and VN must be at least in part different.
[Show abstract][Hide abstract] ABSTRACT: The urokinase plasminogen activator system (uPA) has been demonstrated to be required for the movement of cells through a matrix. These observations have been extended to the migration of endothelial cells during the process of angiogenesis, and recent data suggest that the uPA system is central to this process. uPA is a serine protease that is capable of initiating an extracellular cascade of proteolysis that involves the activation of plasminogen and matrix metalloproteases. These proteolytic cascades remodel extracellular matrix (ECM) and basement membrane (BM), allowing for the movement of cells across and through these barriers. In addition, these proteolytic cascades process and release various growth and differentiation factors that are sequestered on the cell surface or within the ECM, which contribute to the evolution of a migratory or invasive cell phenotype. uPA is also able to modulate signaling and cell adhesion through its specific cell surface receptor, uPAR. Recent data suggest that the nonproteolytic activities of the uPA system are coupled to adhesion, migration and signaling through various integrins. This article reviews the evidence for the role of this system in tumor angiogenesis and metastasis, which suggests that the uPA system initiates multiple cascades that contribute to these processes.
Surgical Oncology Clinics of North America 05/2001; 10(2):393-415, x. · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We previously identified the urokinase plasminogen activator receptor (UPAR) as a gene induced by nerve growth factor (NGF), but not by epidermal growth factor (EGF), in PC12 cells (Farias-Eisner et al.  J. Neurosci. 20:230-239). Antisense oligonucleotides for the UPAR mRNA or an antibody directed against UPAR protein, added simultaneously with NGF, block NGF-induced morphological and biochemical differentiation of PC12 cells. In this report, we show that anti-UPAR antibody blocks morphological differentiation and the expression of two NGF-specific secondary response genes, collagenase-1 and transin, in PC12 cells only during the first 2 hr following NGF exposure. These data suggest that induced UPAR expression is required only over a short period of time following exposure to NGF for the differentiation program in PC12 cells to proceed. For two models of "primed" PC12 cells, we found that UPAR expression and function are not required for NGF-induced differentiation. UPAR and the secondary response genes collagenase-1 and transin are not induced in "primed" PC12 cells in response to NGF, and anti-UPAR antibody does not block morphological differentiation in these cells. Our data suggests that UPAR is required only transiently during the "priming" of PC12 cells in NGF-induced PC12 cell differentiation.
Journal of Neuroscience Research 03/2001; 63(4):341-6. · 2.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Urokinase plasminogen activator (uPA) plays an important role in the progression of several malignancies including breast cancer. We have identified a noncompetitive antagonist of the uPA-uPAR interaction derived from a nonreceptor binding region of uPA (amino acids 136-143). This 8-mer capped peptide (A6) inhibited breast cancer cell invasion and endothelial cell migration in a dose-dependent manner in vitro without altering cell doubling time. Intraperitoneal administration of A6 resulted in a significant inhibition of tumor growth and suppressed the development of lymph node metastases in several models of breast cancer cell growth and metastasis. Large areas of tumor necrosis and extensive positive staining by TUNEL were observed on histological and immunohistochemical analysis of experimental tumor sections from A6-treated animals. A6 treatment also resulted in a decrease in factor VIII-positive tumor microvessel hot-spots. These results identify a new epitope in uPA that is involved in the uPA-uPAR interaction and indicate that an antagonist based on this epitope is able to inhibit tumor progression by modulating the tumor microenvironment in the absence of direct cytotoxic effects in vivo.
The FASEB Journal 08/2000; 14(10):1400-10. · 5.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Neoplasia may produce a spectrum of dysregulatory effects on bone and mineral metabolism. The range of these effects and the known molecular mechanisms causing them are reviewed.
The current review is mainly based on previously published scientific reports from North America, Europe, and Japan that were identified from references in the literature.
Osteolysis is the most common skeletal manifestation of neoplasia and may be focal or generalized. When tumors release abundant parathyroid hormone-related peptide (PTHrP) into the circulation, this may act as an endocrine substance to produce generalized osteopenia and, ultimately, hypercalcemia. PTHrP also may act in a paracrine manner to enhance focal osteolysis associated with metastasis and to generate hypercalcemia. The increased circulating PTHrP in tumor states also can augment serum calcium by renal mechanisms. PTHrP may contribute to focal osteolysis by tumor metastases, even in the absence of hypercalcemia. Strategies to reduce PTHrP production or PTHrP signaling, therefore, may be useful to treat the tumor-induced bone resorption induced both in hypercalcemic and nonhypercalcemic states. The most commonly used intervention, bisphosphonates, targets the osteoclast directly. Although osteolytic lesions generally occur with some degree of reactive new bone formation, osteoblastic lesions may be particularly abundant in association with certain tumors, such as prostate carcinoma. The mechanisms underlying these lesions remain unknown; however, a variety of osteoblast growth factors may contribute. These include the urokinase system, which may have growth factor activity as well as enzymatic activity. Finally, osteomalacia may be a manifestation of tumors either through accelerated bone formation with insufficient mineralization or through the production of a phosphaturic substance.
Elucidation of the mechanisms underlying the spectrum of skeletal manifestations of neoplasia is yielding important insights into both tumor diagnosis and patient management.
Cancer 07/2000; 88(12 Suppl):2903-8. · 5.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tumor production of parathyroid hormone-related protein (PTHRP) is responsible for most cases of hypercalcemia of malignancy. The transplantable rat Leydig tumor H-500 is known to cause hypercalcemia in rats by the release of abundant PTHRP and to closely reproduce the human syndrome. We have demonstrated recently that Ras oncogene can stimulate PTHRP gene expression in Fr3T3 fibroblasts in vitro and cause hypercalcemia in vivo. Using rat Leydig tumor H-500 cells, we have investigated the role of effector pathways downstream of Ras in serum-induced PTHRP expression. The Ras inhibitors B-1086 and Lovastatin decreased PTHRP mRNA expression. i.p. administration of B-1086 (50-100 mg/kg/day) into H-500 tumor-bearing male Fischer rats resulted in a dose-dependent reduction in tumor volume, serum calcium, plasma PTHRP, and tumoral PTHRP mRNA expression. Transient transfection of dominant-negative Ras (Ras N17) and Raf (Raf C4B) reduced, whereas activated Raf-1 (Raf BXB) increased, basal expression of PTHRP in H-500 cells. A similar decrease in PTHRP production was seen with a mitogen-activated protein kinase kinase (MEK) inhibitor (PD 098059), implicating the involvement of Ras/Raf/MEK/extracellular signal-regulated kinase (ERK) pathway. In addition, stimulation with UV light, which can activate c-Jun NH2-terminal kinase (JNK), or expression of an activated form of Rac (Rac V12) was sufficient to increase PTHRP mRNA. Moreover, a dominant-negative Rac (Rac N17) blocked serum-induced PTHRP gene expression. Collectively, these results demonstrate that PTHRP is induced via both Raf-ERK and Rac-JNK mediated pathways, effects which can be blocked by chemical inhibitors and dominant-negative mutants of these pathways in vitro and in vivo. Availability of selective inhibitors of Ras signaling molecules may therefore add to our existing armamentarium to control hypercalcemia of malignancy.
Cancer Research 04/2000; 60(6):1753-60. · 8.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nerve growth factor (NGF)-driven differentiation of PC12 pheochromocytoma cells is a well studied model used both to identify molecular, biochemical, and physiological correlates of neurotrophin-driven neuronal differentiation and to determine the causal nature of specific events in this differentiation process. Although epidermal growth factor (EGF) elicits many of the same early biochemical and molecular changes in PC12 cells observed in response to NGF, EGF does not induce molecular or morphological differentiation of PC12 cells. The identification of genes whose expression is differentially regulated by NGF versus EGF in PC12 cells has, therefore, been considered a source of potential insight into the molecular specificity of neurotrophin-driven neuronal differentiation. A "second generation" representational difference analysis procedure now identifies the urokinase plasminogen activator receptor (UPAR) as a gene that is much more extensively induced by NGF than by EGF in PC12 cells. Both an antisense oligonucleotide for the UPAR mRNA and an antibody directed against UPAR protein block NGF-induced morphological and biochemical differentiation of PC12 cells; NGF-induced UPAR expression is required for subsequent NGF-driven differentiation.
Journal of Neuroscience 02/2000; 20(1):230-9. · 6.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: During the complex multistep process of tumor progression, prostate cancer is initiated as an androgen-sensitive, nonmetastatic cancer, followed by a gradual transition into a highly metastatic and androgen-insensitive variety that lacks the expression of functional androgen receptors (AR). Urokinase (uPA), a member of the serine protease family, has been implicated in the progression of various human malignancies, including prostate cancer. Although uPA production is regulated by various growth factors and cytokines, the role of sex steroids (androgens) in regulating uPA gene expression in prostate cancer is poorly understood. In the current study, we have examined the role of androgens in regulating uPA production and the invasive capacity of the androgen insensitive PC-3 cells transfected with the full-length human AR complementary DNA (PC-3T). Restoration of androgen responsiveness in PC-3T cells caused a marked decrease in cell doubling time. Treatment of PC-3T cells with dihydroxytestosterone (DHT) caused a dose-dependent decrease in uPA messenger RNA and protein production, resulting in their decreased ability to invade through the Matrigel. Nuclear runoff assays revealed that these effects were attributable to the ability of DHT to inhibit uPA gene transcription. AR antagonist flutamide (Flu) reversed the effect of DHT on proliferation and invasion of PC-3T cells. Both control (PC-3) and experimental (PC-3T) cells were injected into the right flank of male BALB/c nu/nu mice. Control animals developed palpable tumors and microscopic tumor metastases at lymph nodes, lungs, and liver at 6-week posttumor cell inoculation. In contrast to this, because of androgen sensitivity of PC-3T cells, palpable tumors were observed only at week 12, with occasional tumor metastases in lungs. Furthermore, inoculation of PC-3T cells into surgically castrated host animals resulted in the development of tumors at a much earlier time (week 10) and a high incidence of metastases, compared with regular animals receiving PC-3T cells. Collectively, these results demonstrate the ability of androgen to regulate uPA production, which may directly effect prostate cancer growth, invasion, and metastasis in vitro and in vivo.
[Show abstract][Hide abstract] ABSTRACT: The catalytically inactive precursor of urokinase-type plasminogen activator (pro-u-PA) induced a chemotactic response in rat smooth muscle cells (RSMC) through binding to the membrane receptor of urokinase (u-PA receptor [u-PAR]). A soluble form of u-PAR activated by chymotrypsin cleavage as well as a peptide located between domain 1 and 2 of u-PAR reproduced the effect of pro-u-PA on cell migration. The chemotactic pro-u-PA effect correlates with a dramatic reorganization of actin cytoskeleton, of adhesion plaques, and with major cell shape changes in RSMC. Pro-u-PA induced a decrease in stress fiber content, membrane ruffling, actin ring formation, and disruption leading to the characteristic elongated cell shape of motile cells with an actin semi-ring located close to the leading edge of cells. u-PAR effects on both chemotaxis and cytoskeleton were sensitive to pertussis toxin and, hence, possibly require G proteins. u-PAR effects are accompanied by a relocation of u-PAR, vitronectin receptor (VNR) alphavbeta3, beta1 integrin subunit, and Src tyrosine kinase to the leading membrane of migrating cells. In conclusion, our data show that pro-u-PA, via binding to u-PAR, controls a signaling pathway, regulated by tyrosine kinases and possibly G proteins, leading to cell cytoskeleton reorganization and cell migration.
[Show abstract][Hide abstract] ABSTRACT: Prostate carcinoma is a common malignancy among males that results in high morbidity and mortality. Here, we have evaluated the capacity of nucleoside analogue BCH-4556 [beta-L-(-)-dioxolane-cytidine] to control prostate cancer progression in our syngeneic model of rat prostate cancer using the rat prostate cancer cell line Dunning R3227 Mat Ly Lu. Different concentrations (50 microM-1 mM) of BCH-4556 resulted in a marked decrease and, eventually, a complete arrest of Mat Ly Lu cell growth in vitro. Cells were inoculated via intracardiac (i.c.) route into the left ventricle or by s.c. injection into the right flank of male Copenhagen rats. Following i.c. inoculation, experimental animals were treated with 75 mg/kg BCH-4556 twice a day or with vehicle alone for 6 consecutive days, starting from day 1 or day 3 post-tumor cell inoculation. Control and experimental animals were monitored for the development of tumor metastases. Treatment with BCH-4556 did not significantly change the development of skeletal metastases and, hence, the time of development of hind limb paralysis. Experimental animals, however, did show a marked reduction in the incidence and size of tumor metastases at the adrenal glands. Following the development of palpable tumors after s.c. injection of Mat Ly Lu cells on day 8 post tumor cell inoculation, animals were treated i.p. with 25-75 mg/kg BCH-4556 twice a day or with vehicle alone for 6 consecutive days. Control animals developed large primary tumors and macroscopic metastasis to lungs, lymph nodes, kidneys, and spleen. In contrast, experimental animals receiving BCH-4556 showed a marked decrease in tumor volume and metastases after the last injection of BCH-4556. The maximum dose of BCH-4556 (75 mg/kg twice a day) caused a complete arrest in tumor growth that was maintained for up to 4-6 days without any evidence of cytotoxicity. These antitumor effects of BCH-4556 were more marked than those of doxorubicin in blocking tumor growth in this model of prostate cancer, and it continued to be effective following three cycles of treatment, without manifesting any signs of drug resistance.
Cancer Research 09/1998; 58(15):3461-5. · 8.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite our recent advances in characterizing the molecular basis of breast and prostate cancer and their early detection with the aid of new imaging and diagnostic techniques, these cancers continue to be the leading causes of cancer-related deaths. This limited success in achieving our ultimate goal of cancer control is due to our inability to block the production of various factors produced in the later stages of these cancers that cause this high rate of mortality. A key requirement in the complex process of tumor invasion is the ability of tumor cells to produce and recruit growth factors and proteolytic enzymes within the tumor cell environment to promote neovascularization, tumor growth and promote extracellular matrix (ECM) degradation to facilitate tumor metastasis. One such protease, urokinase (uPA), has been strongly implicated in the progression of several malignancies including breast and prostate cancer. Along with uPA, its cell surface receptor (uPAR) is also believed to be involved due to its ability to recruit uPA within the tumor cell environment. In recent years, novel in vivo models of breast and prostate cancer have been developed which have clearly demonstrated the significance of uPA and uPAR in the invasion and metastases of these hormone-dependent cancers. The availability of these in vivo models has now permitted us to evaluate the molecular, chemical and immunotherapeutic strategies targeted against the uPA/uPAR system. This review describes the mechanism of uPA actions in tumor progression and analyses the usefulness of these in vivo models to authenticate uPA/uPAR as a therapeutic target and evaluates the benefits of blocking uPA/uPAR interactions alone or in combination with currently available treatment modalities against this cancer. Based on these results, there is an urgent need to develop and optimize strategies which will ultimately allow us to control the progression of these malignancies and enhance our ability to effectively manage these patients.
International Journal of Oncology 04/1998; 12(4):911-20. · 2.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Parathyroid hormone related peptide (PTHRP) is the major causal agent in the syndrome of malignancy-associated hypercalcemia (MAH). Several studies have shown that PTHRP production is increased in response to growth factors and oncogenes, such as Tpr-Met, that are associated with the tyrosine kinase signaling pathway. Using site-directed mutagenesis of Tpr-Met and chemical inhibitors of phosphotidylinositol-3 kinase and Ras isoprenylation, we demonstrated previously that induction of PTHRP is mediated via the Ras signaling pathway. In the present study, we have directly investigated the role of the Ras oncogene in MAH. As a model system, we used Fisher rat 3T3 fibroblasts stably transfected with a Ras oncogene (Ras-3T3). Ras transfection enhanced PTHRP production 5-10-fold in these cells, and inoculation of this cell line into nude mice led to the development of hypercalcemia within 2 weeks. We used this system to evaluate the effect of a potent inhibitor of Ras processing, B-1086, on cell growth, PTHRP production, plasma calcium, and tumor growth. Treatment of Ras-3T3 cells in vitro with B-1086 at 0.1-10 microg/ml produced a significant reduction in PTHRP mRNA expression and PTHRP secretion and a significant decrease in cell proliferation. Treatment in vivo of BALB/c/nu/nu mice bearing Ras-3T3 tumors with B-1086 resulted in a significant inhibition in tumor growth. In addition, this treatment produced near normalization of serum Ca2+, a significant decrease in plasma PTHRP, and a reduction in tumoral PTHRP mRNA levels. These results show that the Ras pathway is involved in PTHRP production by tumors, identifies Ras as a potential target for treatment of MAH, and demonstrates Ras processing inhibitors as candidate therapeutic agents against this syndrome.
Cancer Research 11/1997; 57(20):4517-22. · 8.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Urokinase (urokinase plasminogen activator, uPA) and its cell surface receptor (uPA receptor, uPAR) play an important role in a variety of physiological and pathological processes requiring cell migration and tissue remodeling. Using our syngeneic model of uPAR overexpression by the rat breast cancer cell line Mat B-III, we have examined the ability of the nonsteroidal antiestrogen, tamoxifen (TAM), and of a selective synthetic inhibitor of uPA, 4-iodo benzo[b]thiophene-2-carboxamidine (B-428), to inhibit expression of uPA and uPAR as well as cell growth, invasion, and metastasis of wild-type Mat B-III cells and of cells overexpressing uPAR (Mat B-III-uPAR). Both TAM and B-428 inhibited uPAR gene transcription, mRNA expression, protein production and also decreased the proliferative and invasive capacity of Mat B-III and Mat B-III-uPAR. The effects of TAM and B-428 were more pronounced when these agents were tested in combination. Both control and experimental cells (1 x 10(6) cells) were inoculated orthotopically into the mammary fat pad of syngeneic female Fisher rats, and animals were infused i.p. with either TAM and B-428 alone or in combination for 2 weeks. Control animals receiving vehicle alone developed large tumors and macroscopic metastases to lungs, liver, and lymph nodes. In contrast to this, experimental animals receiving TAM and B-428 showed a significant decrease in primary tumor volume and metastases. Combination therapy had especially marked effects in blocking progression of the primary tumor in experimental animals inoculated with highly aggressive Mat B-III-uPAR cells. These results underscore the utility of anti-proteolytic agents (B-428) in addition to standard hormone therapy (TAM) in advanced breast cancer patients where the uPA/uPAR system plays a key role in tumor progression.
Cancer Research 09/1997; 57(16):3585-93. · 8.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Previous studies have demonstrated that overexpression of urinary plasminogen activator (uPA) in rat prostate cancer cells results in increased skeletal metastases, which are primarily of the osteoblastic variety. The osseous activation induced by the metastases appears to be mediated through the amino terminal fragment (ATF) of uPA, which lacks the catalytic domain and can act as a growth factor for osteoblasts. To explore further the mechanism of action of uPA in bone cells, we evaluated the effects of ATF on modulating the expression of various proto-oncogenes. Human-osteoblast-derived osteosarcoma cells, SaOS2, were treated with graded doses of ATF for 10-120 min, and effects on early response proto-oncogenes were monitored. ATF increased c-myc, c-jun, and c-fos gene expression in a time-dependent manner for up to 60 min, after which mRNA levels fell. The maximum induction was seen in c-fos gene expression, which was found to be dose dependent. This effect of ATF was localized to its growth-factorlike domain. Examination of the half life of these transcripts in the presence of the transcriptional inhibitor actinomycin D demonstrated that ATF does not alter the stability of c-fos mRNA in these bone cells. Nuclear run-off assays indicated that ATF effects were due to stimulation of c-fos gene transcription. An increase in c-fos protein levels was correlated with the augmentation of its mRNA in ATF-treated SaOS2 cells. Pretreatment of SaOS2 cells with the protein tyrosine kinase inhibitor herbimycin and recombinant soluble uPA receptor (uPAR) caused a significant reduction in the ability of ATF to induce c-fos expression. These results demonstrate a novel role for uPA in activating early response proto-oncogenes, in particular c-fos, which plays an important role in bone cell growth and differentiation and may be a key factor in the signal transduction pathway of ATF.
Journal of Cellular Physiology 09/1997; 172(2):137-45. · 4.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have synthesized and purified recombinant parathyroid hormone related peptide (PTHrP (1-141)) and PTHrP (38-141) using an E. coli system that requires minimal purification. The cDNAs encoding PTHrP (1-141) and PTHrP (35-141) respectively were inserted into the multiple cloning site of the pTrcHis-B bacterial expression plasmid. The PTHrP encoded sequences were thereby fused at their NH2-termini to six histidine residues within the fusion protein. The recombinant plasmids were transfected into E. coli cells and PTHrP synthesis was induced by addition of 1 mM isopropyl-beta-D-thiogalactopyranoside (IPTG) at 37 degrees C. The recombinant fusion proteins were purified by binding of the histidine residues to a nickel column followed by gradient elusion and dialysis. PTHrP (1-141) was released from its fusion protein by cyanogen bromide cleavage, whereas PTHrP (38-141) was released by enzymatic digestion with enterokinase. This rapid isolation method resulted in pure PTHrP (1-141) and (38-141) as judged by SDS-polyacrylamide gel electrophoresis and NH2-terminal sequence analysis. PTHrP (1-141) stimulated cAMP accumulation and mobilized intracellular calcium ([Ca2+]i) in UMR106 osteoblast-like cells, and stimulated phosphate transport in OK/E renal cells, whereas PTHrP (38-141) was inert in these bioassays. Availability of PTHrP and its NH2-terminally truncated analogue, which lacks the sequence necessary for its hypercalcemic actions, will enable their biological activities to be examined in greater detail.
Molecular and Cellular Endocrinology 07/1997; 130(1-2):13-21. · 4.04 Impact Factor