Adenovirus-mediated interferon-beta gene therapy suppresses growth and metastasis of human prostate cancer in nude mice

The purpose of this study was to determine the effects of interferon-beta (IFN-beta) gene transfer on the growth of PC3MM2 human prostate cancer cells in nude mice. Intralesional delivery of an adenoviral vector encoding murine IFN-beta (AdIFN-beta), but not a vector encoding bacterial beta-galactosidase (AdLacZ), suppressed PC3MM2 tumors in a dose-dependent manner. At the highest dose (2x10(9) plaque-forming units, PFU), a single injection of AdIFN-beta (but not AdLacZ) suppressed orthotopic PC3MM2 tumors and development of metastasis by 80%, and eradicated the tumors in 20% of mice. Immunohistochemical staining showed that AdIFN-beta-treated tumors contained fewer microvessels, fewer proliferating cells, and more apoptotic cells than did the control tumors. Compared with controls, tumors injected with AdIFN-beta expressed higher levels of IFN-beta and inducible nitric oxide synthase (iNOS) and lower levels of basic fibroblast growth factor (bFGF) and transforming growth factor beta1 (TGF-beta1). In vitro analysis indicated that expression of bFGF and TGF-beta1 in PC3MM2 cells could be suppressed by the nitric oxide donor sodium nitroprusside. These data suggest that intratumoral delivery of the IFN-beta gene with adenoviral vectors could be an effective therapy for prostate cancer and that tumor suppression by AdIFN-beta correlated with up-regulation of iNOS and down-regulation of angiogenesis.     

Concurrent chemoradiotherapy with low-dose docetaxel inhibits the growth of DU-145 prostate cancer xenografts

Introduction

Concurrent chemoradiotherapy (CCRT) has been widely used during the past decades in clinical trials and has now become a common treatment option in many clinical settings. The present study was designed to evaluate the efficacy of combining radiation with low-dose docetaxel in DU-145 prostate cancer xenograft models.

Methods

Male BALB/c nude mice bearing human DU-145 prostate tumors were assigned to four treatment groups: (1) control, (2) docetaxel (10 mg/kg/week, i.v., ×3 weeks), (3) radiation (2 Gy, q.d. ×5, ×3 weeks), (4) CCRT (the combination of docetaxel and radiation). Treatment efficacy was determined by tumor volume and tumor regression measurements. The extent of apoptosis in tumors in response to treatments was assessed via terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) assay. In addition, immunohistochemical staining of CD34 was done to quantify microvessel density in the tumors.

Results

Our in vivo studies using DU-145 xenograft models in nude mice showed that CCRT compared to either alone significantly inhibited tumor growth, and the percentages of tumor regression were 32.6, 44.2, and 68.6 % for docetaxel, radiation, and CCRT, respectively. Moreover, CCRT did not significantly affected mice weight as compared to docetaxel or radiation alone. TUNEL assays showed that significantly more apoptotic cells were induced in the tumors treated with CCRT than either treatment alone. Anti-CD34 immunohistochemical staining indicated that CCRT significantly inhibited tumor angiogenesis.

Conclusion

These findings suggest that CCRT with low-dose docetaxel inhibits the growth of DU-145 prostate cancer xenografts, by enhancing apoptosis and suppressing angiogenesis. Based on these preclinical findings, we suggest that CCRT for the treatment of prostate cancer deserves further development.     

Inhibition of growth and metastasis of orthotopic human prostate cancer in athymic mice by combination therapy with pegylated interferon-alpha-2b and docetaxel

We evaluated whether treatment of orthotopic human prostate cancer in nude mice with pegylated IFN-alpha-2b (PEG-IFN-alpha-2b) and docetaxel could represent a two-compartment targeting of primary tumor (tumor cells and tumor-associated endothelial cells) and inhibition of regional lymph node metastasis. The antiangiogenic properties of IFN were combined with the cytotoxic properties of docetaxel, resulting in apoptosis of both tumor cells and endothelium and hence significant inhibition of primary tumor growth. We first determined the optimal biological dose of PEG-IFN-alpha-2b (70,000 IU/week) necessary to down-regulate the expression of basic fibroblast growth factor, matrix metalloprotease-9, and matrix metalloprotease-2. The therapeutic dose of docetaxel (10 mg/kg/week) was determined by efficacy and minimal body weight loss. Therapy beginning 3 days after orthotopic implantation of PC3-MM2 prostate cancer cells reduced tumor weight by 37% in mice treated with PEG-IFN-alpha-2b, by 60% in mice treated with docetaxel, and by 83% in those given both drugs. PEG-IFN-alpha-2b also induced apoptosis of tumor-associated endothelial cells and hence a significant decrease in microvessel density. Our data indicate that the combination of PEG-IFN-alpha and docetaxel inhibits neoplastic angiogenesis by inducing a decrease in the local production of proangiogenic molecules by tumor cells, resulting in increased apoptosis of tumor-associated endothelial cells.     

Non-viral delivery of the connexin 43 gene with histone deacetylase inhibitor to human nasopharyngeal tumor cells enhances gene expression and inhibits in vivo tumor growth

Dysregulation of connexin expression is believed to have a role in carcinogenesis, because levels of connexin are reduced in various tumors. We examined the role of connexin 43 (Cx43) alone and combined with a histone deactylase (HDAC) inhibitor in tumor growth inhibition. The transfection of Cx43 plasmid DNA (pCMV-Cx43) into human nasopharyngeal cancer KB cells using folate-linked nanoparticles induced inhibition of cell growth. Cx43 induced a tumor suppressive effect via a gap junctional intercellular communication-independent mechanism. The transfection of pCMV- Cx43 along with an HDAC inhibitor, 4-phenylbutyrate (4-PB), enhanced Cx43 expression greatly in vitro, and inhibited significantly the tumor growth of KB cells and xenografts compared with that of pCMV-Cx43 alone. 4-PB induced increased expression of genes of DNA damage checkpoints and of apoptosis via the down-regulation of anti-apoptotic bcl-2 mRNA expression and up-regulation of the activity of the apoptosis-associated enzyme caspase-3/7. Thus, the amplified Cx43 expression by an antitumor agent, an HDAC inhibitor, may have great potential as a growth inhibitor for nasopharyngeal tumors.     

Dietary genistein inhibits metastasis of human prostate cancer in mice

Dietary genistein has been linked to lower prostate cancer (PCa) mortality. Metastasis is the ultimate cause of death from PCa. Cell detachment and invasion represent early steps in the metastatic cascade. We had shown that genistein inhibits PCa cell detachment and cell invasion in vitro. Genistein-mediated inhibition of activation of focal adhesion kinase (FAK) and of the p38 mitogen-activated protein kinase (MAPK)-heat shock protein 27 (HSP27) pathway has been shown by us to regulate PCa cell detachment and invasion effects, respectively. To evaluate the antimetastatic potential of genistein, we developed an animal model suited to evaluating antimetastatic drug efficacy. Orthotopically implanted human PC3-M PCa cells formed lung micrometastasis by 4 weeks in >80% of inbred athymic mice. Feeding mice dietary genistein before implantation led to blood concentrations similar to those measured in genistein-consuming men. Genistein decreased metastases by 96%, induced nuclear morphometric changes in PC3-M cells indicative of increased adhesion (i.e., decreased detachment) but did not alter tumor growth. Genistein increased tumor levels of FAK, p38 MAPK, and HSP27 "promotility" proteins. However, the ratio of phosphorylated to total protein trended downward, indicating a failure to increase relative amounts of activated protein. This study describes a murine model of human PCa metastasis well suited for testing antimetastatic drugs. It shows for the first time that dietary concentrations of genistein can inhibit PCa cell metastasis. Increases in promotility proteins support the notion of cellular compensatory responses to antimotility effects induced by therapy. Studies of antimetastatic efficacy in man are warranted and are under way.     

VSV-MP gene therapy strategy inhibits tumor growth in nude mice model of human lung adenocarcinoma

Vesicular stomatitis virus (VSV) matrix protein (MP) can induce in vitro apoptosis of tumor cells in the absence of other viral components. Here, the antitumor activity of VSV-MP against lung adenocarcinoma was investigated in vivo. A pVAX-plasmid DNA encoding VSV-MP and control empty vectors (pVAX) were constructed and wrapped-up with liposome. A549 and Spc-A1 human lung adenocarcinoma cells were transfected with liposomal-VSV-MP (Lip-MP) or Lip-pVAX and then examined for cell viability or apoptosis using Hoechst/propidium iodide staining by flow cytometry, and further demonstrated by caspase/poly ADP-ribose polymerase (PARP) cleavage analysis. For the in vivo study, A549 and Spc-A1 lung carcinoma models in nude mice were established and randomly assigned into three groups to receive eight 2-weekly intravenous administrations of medium alone as control, Lip-pVAX or Lip-MP, respectively. Subsequently, Lip-MP significantly reduced tumor growth and prolonged the survival of tumor-bearing mice compared with Lip-pVAX and control agents (P<0.05), with much higher apoptosis index of both in vivo and in vitro tumor cells, respectively (P<0.05). In addition, in vivo antitumoral effect was associated with natural killer-(NK) cell congregation without evidence of toxicity. These observations suggest that systemically delivering Lip-MP has a specific dual antitumor activity in human lung adenocarcinoma by inducing apoptosis and possibly stimulating NK-cell responses, it may provide a clue for developing new therapeutic approaches against human lung adenocarcinoma.     

Hydrazinobenzoylcurcumin inhibits androgen receptor activity and growth of castration-resistant prostate cancer in mice

There is a critical need for therapeutic agents that can target the amino-terminal domain (NTD) of androgen receptor (AR) for the treatment of castration-resistant prostate cancer (CRPC). Calmodulin (CaM) binds to the AR NTD and regulates AR activity. We discovered that Hydrazinobenzoylcurcumin (HBC), which binds exclusively to CaM, inhibited AR activity. HBC abrogated AR interaction with CaM, suppressed phosphorylation of AR Serine81, and blocked the binding of AR to androgen-response elements. RNA-Seq analysis identified 57 androgen-regulated genes whose expression was significantly (p ≤ 0.002) altered in HBC treated cells as compared to controls. Oncomine analysis revealed that genes repressed by HBC are those that are usually overexpressed in prostate cancer (PCa) and genes stimulated by HBC are those that are often down-regulated in PCa, suggesting a reversing effect of HBC on androgen-regulated gene expression associated with PCa. Ingenuity Pathway Analysis revealed a role of HBC affected genes in cellular functions associated with proliferation and survival. HBC was readily absorbed into the systemic circulation and inhibited the growth of xenografted CRPC tumors in nude mice. These observations demonstrate that HBC inhibits AR activity by targeting the AR NTD and suggest potential usefulness of HBC for effective treatment of CRPC.     

Isosilibinin inhibits advanced human prostate cancer growth in athymic nude mice: comparison with silymarin and silibinin

Earlier studies have shown the cancer chemopreventive efficacy of silymarin and its semi-purified constituent silibinin against prostate cancer (PCa), but the efficacy of other constituents of silymarin is largely unknown. In the present study, we assessed the in vivo growth inhibitory efficacy of one such constituent isosilibinin (a 50:50 mixture of isosilybin A and isosilybin B) in comparison with silymarin and silibinin in human PCa DU145 xenograft in athymic nude mice. Isosilibinin feeding (200 mg/kg body weight per day) significantly inhibited the growth of xenograft after 53 days of treatment (p < or = 0.005), which was equally or slightly better effective than silymarin and silibinin, respectively. Treatment with isosilibinin, silymarin and silibinin was stopped after 53 days and tumor volume was measured till 77 days. After 24 days of treatments withdrawal, tumor volume remain decreased, however, it was statistically significant only with isosilibinin (p < or = 0.05), suggesting its prolonged effect. Biomarker analysis showed that isosilibinin, silymarin and silibinin treatment for 53 days significantly inhibited the immunoreactivity for proliferating cell nuclear antigen (PCNA), microvessel density (CD31) and vascular endothelial growth factor along with significant increase in apoptotic cell population. The PCNA levels in tumors remained significantly low even after 24 days of treatments withdrawal. Western blot analysis of tumor tissue suggested that these flavonolignan formulations differentially alter the expression of cell cycle regulatory molecules, cyclins and Cdks. Overall, the results of present study suggest that isosilibinin has comparatively better efficacy against PCa and should be further analyzed for its clinical utility.     

Tumor-infiltrating macrophages are involved in suppressing growth and metastasis of human prostate cancer cells by INF-beta gene therapy in nude mice.

PURPOSE: This study was to determine the role of tumor-infiltrating macrophages in IFN-beta-induced host defense against prostate cancer. EXPERIMENTAL DESIGN: Efficacy of adenovirus-mediated IFN-beta gene therapy against orthotopic xenografts of human prostate cancer was tested in macrophage-compromised nude mice. Immunohistochemistry and Northern blotting were used to elucidate mechanisms responsible for the IFN-beta gene therapy. RESULTS: PC-3MM2 human prostate cancer cells were inoculated into the prostates of nude mice. Intralesional injection of an adenoviral vector-encoding murine IFN-beta (AdmIFN-beta) but not control vector AdE/1 suppressed growth of PC-3MM2 tumors in a dose-dependent manner, with a maximal reduction of tumor weight by approximately 85% at 2 x 10(9) plaque-forming units. The therapy prevented metastasis, eradicated established metastases in some mice, and prolonged the survival of tumor-bearing mice. The efficacy of AdmIFN-beta therapy was reduced significantly in mice treated with macrophage-selective anti-Mac-1 and anti-Mac-2 antibodies. Moreover, the i.p. injection of the antibodies restored the tumorigenicity of PC-3MM2 cells stably engineered with murine IFN-beta gene. Tumor-infiltrating macrophages, significantly increased in AdmIFN-beta-injected lesions, were depleted by the antibodies. The therapy stimulated expression of the inducible nitric oxide synthase, down-regulated transforming growth factor-beta1 and interleukin-8, reduced microvessel density, and resulted in apoptosis of endothelial cells in the lesions. These effects of AdmIFN-beta were partially diminished in mice treated with the antibodies. CONCLUSIONS: These data suggest that macrophages play an important role in IFN-beta gene therapy and that intralesional delivery of the IFN-beta gene could be an effective therapy for clinically localized human prostate cancer.     

Cotargeting tumor and tumor endothelium effectively inhibits the growth of human prostate cancer in adenovirus-mediated antiangiogenesis and oncolysis combination therapy

Tumor-endothelial interaction contributes to local prostate tumor growth and distant metastasis. In this communication, we designed a novel approach to target both cancer cells and their "crosstalk" with surrounding microvascular endothelium in an experimental hormone refractory human prostate cancer model. We evaluated the in vitro and in vivo synergistic and/or additive effects of a combination of conditional oncolytic adenovirus plus an adenoviral-mediated antiangiogenic therapy. In the in vitro study, we demonstrated that human umbilical vein endothelial cells (HUVEC) and human C4-2 androgen-independent (AI) prostate cancer cells, when infected with an antiangiogenic adenoviral (Ad)-Flk1-Fc vector secreting a soluble form of Flk1, showed dramatically inhibited proliferation, migration and tubular formation of HUVEC endothelial cells. C4-2 cells showed maximal growth inhibition when coinfected with Ad-Flk1-Fc and Ad-hOC-E1, a conditional replication-competent Ad vector with viral replication driven by a human osteocalcin (hOC) promoter targeting both prostate cancer epithelial and stromal cells. Using a three-dimensional (3D) coculture model, we found that targeting C4-2 cells with Ad-hOC-E1 markedly decreased tubular formation in HUVEC, as visualized by confocal microscopy. In a subcutaneous C4-2 tumor xenograft model, tumor volume was decreased by 40-60% in animals treated with Ad-Flk1-Fc or Ad-hOC-E1 plus vitamin D3 alone and by 90% in a combined treatment group, compared to untreated animals in an 8-week treatment period. Moreover, three of 10 (30%) pre-established tumors completely regressed when animals received combination therapy. Cotargeting tumor and tumor endothelium could be a promising gene therapy strategy for the treatment of both localized and metastatic human prostate cancer.     

ProstaCaid inhibits tumor growth in a xenograft model of human prostate cancer

We have recently demonstrated that the dietary supplement ProstaCaid (PC) inhibits growth and invasive behavior of PC-3 human prostate cancer cells in vitro. In the present study, we evaluated toxicity and whether PC suppresses growth of prostate cancer in a xenograft model of human prostate cancer cells implanted in mice. Here, we show that an oral administration of PC (100, 200 and 400 mg/kg) did not affect body weight or activity of liver enzymes (ALT, AST) and did not show any sign of toxicity in liver, spleen, kidney, lung and heart tissues in mice. In addition, PC treatment resulted in the inhibition of tumor volumes (1024.6 ± 378.6 vs. 749.3 ± 234.3, P<0.001) in a xenograft model of prostate cancer with human hormone refractory (independent) PC-3 prostate cancer cells. Moreover, qRT-PCR analysis demonstrated significant upregulation of expression of CDKN1A (p21) and inhibition of expression of IGF2, NR2F2 and PLAU (uPA) genes by an oral administration of PC in prostate cancer xenografts. Our study demonstrates that the concentrations of the dietary supplement ProstaCaid tested did not show signs of toxicity, and its oral application has significant anticancer activity in vivo and can be considered as an alternative treatment for prostate cancer patients.     

全反式维甲酸对激素非依赖性前列腺癌连接蛋白43表达的影响

目的:探讨全反式维甲酸(all-trans retinoic acid,ATRA)对激素非依赖性前列腺癌连接蛋白43(Cx43)表达的影响及其临床价值。方法:应用激素非依赖性前列腺癌细胞PC-3细胞建立荷前列腺癌裸鼠模型,分为ATRA治疗组(n=9)和对照组(n=9),半定量逆转录聚合酶链式反应(RT-PCR)和免疫组织化学法分别检测肿瘤组织中Cx43的表达,并动态观察肿瘤生长抑制情况。结果:与对照组比较,ATRA可以显著抑制肿瘤生长(P＜0．05)。RT-PCR检测结果提示,治疗组中Cx43 mRNA表达量为2．03±0．85,明显高于对照组的0．99±0．23(P＜0．05)。免疫组织化学法显示对照组肿瘤组织中Cx43蛋白表达微弱;而治疗组中表达量明显升高,以细胞膜上表达为主。结论:激素非依赖性前列腺癌组织中Cx43表达低下,ATRA可以提高其表达而抑制肿瘤的生长。     

KG-135, enriched with selected ginsenosides,inhibits the proliferation of human prostate cancer cells in culture and inhibits xenograft growth in athymic mice

Sun ginseng (SG) was recently developed as a heat-processed form of ginseng. The Rg3, Rk1, and Rg5 ginsenosides are its main ginsenoside components. SG has been reported to have more potent pharmacological activities than red ginseng (RG), where these pharmacological activities include vasodilatory, anti-oxidant and anti-tumorigenic effects. In the present study, we investigated KG-135, the ginsenoside-rich fraction of SG and demonstrated that this fraction inhibits proliferation of human prostate cancer cells both in vitro and in vivo. KG-135 caused a significant growth inhibition of DU145 and PC-3 human prostate cancer cells. KG-135 induced cell cycle arrest in the G1 phase and caused an associated increase in the p21^Cip1 protein levels. When KG-135 was fed to mice that had been xenografted with DU145 tumors, a time-dependent inhibition of tumor growth was noted without any observed toxicity. Immunohistochemical analysis of the tumor tissues showed that KG-135 led to a decrease in the expression of proliferating cell nuclear antigen (PCNA). Microarray analysis of the tumors revealed that KG-135 inhibited tumor growth and also caused changes in the expression levels of multiple cancer-related genes. These data suggest that KG-135 effectively inhibits prostate cancer cell proliferation. Its mechanism of action likely involves cyclin inhibition and regulation of the expression of the TNFRSF25 and ADRA2A genes.     

Genistein and quercetin increase connexin43 and suppress growth of breast cancer cells

Connexin proteins form gap junctions, which permit direct exchange of cytoplasmic contents between neighboring cells. Evidence indicates that gap junctional intercellular communication (GJIC) is important for maintaining homeostasis and preventing cell transformation. Furthermore, connexins may have independent functions including tumor growth suppression. Most tumors express less connexins, have reduced GJIC and have increased growth rates compared with non-tumorigenic cells. The purpose of this study was to determine whether common flavonoids, genistein and quercetin, increase connexin43 (Cx43) levels, improve GJIC and suppress growth of a metastatic human breast tumor cell line (MDA-MB-231). Quercetin (2.5, 5 microg/ml) and genistein (0.5, 2.5, 15 microg/ml) upregulated Cx43 but failed to increase GJIC. Cx43 localized to the plasma membrane following genistein treatment (2.5, 15 mug/ml). In contrast, Cx43 aggregated in the perinuclear region following quercetin treatment (0.5, 2.5, 5, 15 microg/ml). Both genistein (15 microg/ml) and quercetin (2.5, 5, 15 microg/ml) significantly reduced MDA-MB-231 cell proliferation. In summary, genistein and quercetin increase Cx43 and suppress MDA-MB-231 cell proliferation at physiologically relevant concentrations. These results demonstrate that genistein and quercetin are potential anti-breast cancer agents.     

Paclitaxel and docetaxel in prostate cancer

Although their ultimate value in prostate cancer therapy remains to be defined in randomized trials, docetaxel and paclitaxel are active agents in HRPC. Combination therapies using either of these taxanes plus oral EMP show reproducible antitumor activity that appears to be greater and more durable than that of single-agent treatment. Although the optimal combination and schedule have not been determined, weekly paclitaxel and EMP and docetaxel given every 3 weeks or by weekly infusion with EMP are useful treatment options for patients with progressive HRPC. The gastrointestinal toxicity of EMP has been reduced by intermittent rather than continuous administration, and other toxicities may be reduced further by use of intravenous EMP. Although there has been progress, the median time to progression of 5 to 6 months for current taxane-based therapies suggests that they will not have major impact on overall survival for patients with HRPC. Greater benefit may be possible earlier in the course of prostate cancer, and the activity of the taxane-EMP combinations is sufficient to justify clinical trials of adjuvant or neoadjuvant chemotherapy for selected groups of patients with locally advanced and poor-prognosis tumors. Armed with many new molecularly targeted agents that may interact favorably with taxanes, it should be possible to build on current antimicrotubule regimens to improve activity in HRPC. Taxane-EMP combinations provide a platform on which to test additional agents that may enhance the apoptotic response or circumvent cellular stress adaptations that confer drug resistance. Further elucidation of signaling pathways that regulate microtubule dynamics and programmed cell death after exposure to microtubule inhibitors would provide a more rational guide for integrating specific inhibitors of signal transduction with current taxane-based therapies. Pharmacokinetic and pharmacodynamic studies will play a key role in the development of future taxane-based therapies for prostate cancer.     

Survivin基因沉默抑制结肠癌生长的动物实验研究

目的 探究survivin基因沉默对人结肠癌Lovo细胞裸鼠移植瘤生长的抑制作用.方法 构建靶向survivin的shRNA载体SUR和阴性对照质粒Neg,并将其转染人结肠癌Lovo细胞,分别种植到裸鼠皮下建立人结肠癌裸鼠移植瘤模型.随后观察各组裸鼠移植瘤生长情况,免疫组化方法检测移植瘤survivin蛋白的表达,TUNEL法检测肿瘤细胞的凋亡情况.结果 移植转染细胞8周,与空白对照组比较,SUR组移植瘤的体积和质量均有显著缩小(P<0.05),体积和质量抑瘤率分别为48.9%和51.2%.与空白对照组比较,SUR组移植瘤survivin表达显著下调,表达指数为31.9%;SUR组肿瘤细胞凋亡显著增加,凋亡指数18.47%(P<0.05).阴性对照Neg组的上述指标与空白对照组比较,差异均无统计学意义.结论 Survivin基因沉默能够抑制人结肠癌Lovo细胞裸鼠移植瘤的生长.     

The urokinase inhibitor p-aminobenzamidine inhibits growth of a human prostate tumor in scid mice

Malignant cells possess a high degree of proteolytic activity in which the plasminogen activator system plays an important role. An increased expression of urokinase type plasminogen activator (uPA) is of significance for degradation of the extracellular tumor matrix, facilitating invasiveness and growth. Inhibition of the active site of uPA makes it possible to evaluate the significance of uPA in tumor growth. We report here experiments on a uPA-producing human prostate xenograft (DU 145) using a competitive inhibitor of uPA, p-aminobenzamidine. In vitro experiments with DU 145 cells showed that p-aminobenzamidine caused a dose-dependent inhibition of uPA activity. DU 145 cells were inoculated s.c. in SCID mice and, once tumors were established, treatment with p-aminobenzamidine added to drinking water was started and lasted for 23 days. Mice receiving 250 mg/kg/day of p-aminobenzamidine showed a clear decrease in tumor-growth rate compared to the nontreated mice, resulting in 64% lower final tumor weight. In addition, uPA-antigen levels in the membrane fractions of DU 145 tumors from p-aminobenzamidine-treated mice were found to be decreased by 59%. We also show that p-aminobenzamidine has an anti-proliferative effect in cell culture at low cell number, correlating with a dose-dependent decrease in uPA production. In conclusion, we show that a low-molecular-weight uPA-inhibttor, p-aminobenzamidine, has a growth-inhibitory effect on a solid uPA-producing tumor. © 1995 Wiley-Liss, Inc.