Hormone-independent Prostate Cancer Research Articles

Potentiation of antitumour activity of docetaxel by combination with trastuzumab in a human prostate cancer xenograft model and underlying mechanisms

Antitumour activity of docetaxel (Taxotere®) in hormone-dependent (HD) and hormone-independent (HID) prostate cancer PAC120 xenograft model was previously reported, and its level was associated with HER2 protein expression. In the present study, we evaluate the antitumour effects of docetaxel combined with trastuzumab (Herceptin®), an anti-HER2 antibody. Although trastuzumab alone had no effect on tumour growth, it potentiated the antitumour activity of docetaxel in HD tumours and more strongly in HID variants. Using the HID28 variant, we show that docetaxel treatment of tumour-bearing mice induces an increased HER2 mRNA expression of the tyrosine kinase receptor of 25-fold 24 h after docetaxel treatment, while HER2 protein and p-AKT decreased. This was followed by an increase of HER2 protein 3 days (two-fold) after docetaxel treatment and by a strong HER2 release in the serum of treated mice; expression of phospho-ERK, p27, BCL2 and HSP70 concomitantly increased. Similar molecular alterations were induced by docetaxel plus trastuzumab combination, except for that there was a transient and complete disappearance of AR and HSP90 proteins 24 h after treatment. We show that in addition to its known effects on tubulin and mitotic spindles, docetaxel induces complex signalisation pathway mechanisms in surviving cells, including HER2, which can be pharmacologically targeted. This study suggests that the docetaxel/trastuzumab combination may prove an effective therapeutic approach for HER2-expressing hormone-refractory prostate cancer.

Elevated E2F1 Inhibits Transcription of the Androgen Receptor in Metastatic Hormone-Resistant Prostate Cancer

Activation of E2F transcription factors, through disruption of the retinoblastoma (Rb) tumor-suppressor gene, is a key event in the development of many human cancers. Previously, we showed that homozygous deletion of Rb in a prostate tissue recombination model exhibits increased E2F activity, activation of E2F-target genes, and increased susceptibility to hormonal carcinogenesis. In this study, we examined the expression of E2F1 in 667 prostate tissue cores and compared it with the expression of the androgen receptor (AR), a marker of prostate epithelial differentiation, using tissue microarray analysis. We show that E2F1 expression is low in benign and localized prostate cancer, modestly elevated in metastatic lymph nodes from hormone-naïve patients, and significantly elevated in metastatic tissues from hormone-resistant prostate cancer patients (P = 0.0006). In contrast, strong AR expression was detected in benign prostate (83%), localized prostate cancer (100%), and lymph node metastasis (80%), but decreased to 40% in metastatic hormone-resistant prostate cancer (P = 0.004). Semiquantitative reverse transcription-PCR analysis showed elevated E2F1 mRNA levels and increased levels of the E2F-target genes dihyrofolate reductase and proliferating cell nuclear antigen in metastatic hormone-independent prostate cancer cases compared with benign tissues. To identify a role of E2F1 in hormone-independent prostate cancer, we examined whether E2F1 can regulate AR expression. We show that exogenous expression of E2F1 significantly inhibited AR mRNA and AR protein levels in prostate epithelial cells. E2F1 also inhibited an AR promoter-luciferase construct that was dependent on the transactivation domain of E2F1. Furthermore, using chromatin immunoprecipitation assays, we show that E2F1 and the pocket protein family members p107 and p130 bind to the AR promoter in vivo. Taken together, these results show that elevated E2F1, through its ability to repress AR transcription, may contribute to the progression of hormone-independent prostate cancer.

Interleukin 6, a Nuclear Factor-κB Target, Predicts Resistance to Docetaxel in Hormone-Independent Prostate Cancer and Nuclear Factor-κB Inhibition by PS-1145 Enhances Docetaxel Antitumor Activity

To investigate whether nuclear factor kappaB (NF-kappaB)/interleukin 6 (IL-6) was linked to docetaxel response in human prostate cancer cell lines, and whether inhibition of NF-kappaB sensitized tumor cells to docetaxel. We also aimed to correlate IL-6 (as a surrogate marker of NF-kappaB) and docetaxel response in hormone-independent prostate cancer (HIPC) patients. Hormone-dependent (LNCaP) and hormone-independent (PC-3 and DU-145) prostate cancer cell lines were exposed to docetaxel alone or combined with the NF-kappaB inhibitor PS-1145 (an inhibitor of IkappaB kinase-2). Effects of dose, exposure time, and schedule dependence were assessed. Activation of NF-kappaB was assayed by electrophoresis mobility shift assay and luciferase reporter assay, IL-6 levels by ELISA, and cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell cycle and apoptosis were assessed by fluorescence-activated cell sorting analysis. Apoptosis was also measured by detection of cleavage of poly(ADP-ribose) polymerase. In patients with metastatic HIPC receiving docetaxel-based chemotherapy, IL-6 serum levels were assayed before chemotherapy and every 3 to 4 weeks thereafter. PC-3 and DU-145 cells had higher NF-kappaB activity, secreted more IL-6, and were more resistant to docetaxel than LNCaP cells. NF-kappaB activity was induced by docetaxel. Cotreatment with docetaxel and PS-1145 prevented docetaxel-induced NF-kappaB activation, reduced IL-6 production, and increased docetaxel effects on cell viability in PC-3 and DU-145 cells but not in LNCaP. Synergism with docetaxel and PS-1145, as assayed by median-effect principle, was observed in DU-145 and PC-3. In HIPC patients, pretreatment IL-6 serum levels correlated to prostate-specific antigen (PSA) response: median IL-6 level was 10.8+/-9.5 pg/mL in PSA responders versus 36.7+/-20.8 pg/mL (P=0.006) in nonresponders. A PSA response was also linked to a decline in IL-6 levels during treatment. Median overall survival was 6.8 months in patients with high IL-6 versus 16.6 months in those with low IL-6 (P=0.0007). On multivariate analysis, pretreatment IL-6 (P=0.05) was an independent prognostic factor for time to disease progression and survival. Inhibition of NF-kappaB emerges as an attractive strategy to enhance docetaxel response in prostate cancer. The interest of this view is further supported by a significant association between high IL-6 in sera of HIPC patients and decreased response to docetaxel.

Serum c-erbB-2 ectodomain (ECD) correlates with immunohistochemical c-erbB-2 expression and predicts an aggressive clinical outcome in hormone-independent prostate cancer (HIPC) patients (pts) treated with docetaxel (D)

4632 Background: The overexpression of c-erbB-2 has been described as a common event associated to the hormone-independent progression in prostate cancer. The clinical implications of c-erbB-2 expression in HIPC pts are not fully established. In this study we investigated the clinical significance of c-erbB-2 serum levels in HIPC pts treated with D and the correlation between serum c-erbB-2 ECD and c-erbB-2 tissue expression. Methods: Pts with HIPC treated with D were tested for serum c-erbB-2 ECD levels by immunoassay before chemotherapy. In pts with available biopsy specimens of hormone-independent tumor, c-erbB-2expression was determined by immunohistochemistry in paraffin-embedded tissue sections. PSA response to D, time to PSA progression and survival were analyzed. Results: Forty-one pts were included in the study. Median follow-up time was 23.3 (3.7–43.1) months. Median time to D progression was 4.1 (0,4–15.1) months and median survival was 11.3 (1,6–43.1). Serum c-erbB-2 correlated with PSA (r=0.351, p=0.025), inversely with time to PSA progression (r = −0.338, p = 0.033) and inversely with survival (r = −0.305, p = 0.05). Median time to PSA progression in pts with high serum c-erbB-2 (≥15 ng/ml) was 1.5 months compared to 4.6 months in pts with low levels (p = 0.0003). Survival in pts with high c-erbB-2 was 11 months and in pts with low c-erbB-2 was 15 months (p = 0.053). HIPC tissue samples from 10 pts were assessed for c-erbB-2 expression. Immunohistochemical c-erbB-2 positive staining (score +2 and +3) was detected in 4 (40%). C-erbB-2 staining showed correlation with serum c-erbB2 levels. Pts with positive staining had 19.1 ± 1.78 ng/ml and negative pts 8.8 ± 2.6 ng/ml (p = 0.001).The 4 pts with tissue c-erbB-2 overexpression had serum c-erbB-2 levels >15 ng/ml, while pts with no c-erbB-2 overexpression in tissue had also low c-erbB-2 levels in serum. Conclusions: High c-erbB-2 ECD in serum is associated with a worse clinical outcome of HIPC. Our data suggest that the determination of c-erbB-2 ECD in serum translates the c-erbB-2 status in the hormone-independent tumor and may be useful to select pts for c-erbB-2-targeted therapy. No significant financial relationships to disclose.

A Series of Unconjugated Ferrocenyl Phenols: Prospects as Anticancer Agents

We recently reported that a ferrocenyl diphenol butene derivative showed a very strong cytotoxic effect on both hormone-dependent and -independent breast cancer cell lines. In order to obtain more information about the structure-activity relationship in the cytotoxicity of small ferrocene compounds, we have prepared a series of simple unconjugated ferrocenyl diphenol complexes (ortho,para; meta,para; para,para). These compounds retain a reasonable to good affinity for both estrogen receptor types, with higher values for the beta form, and superior binding for the para,para diphenol complex (RBA=28%). In vitro these complexes exhibit significant cytotoxic effects on hormone-independent prostate (PC3) and breast cancer cell lines (MDA-MB231), with IC50 values between 2.5 and 4.1 microM. This effect is more marked with PC3, the ortho,para diphenol complex proving the most effective. On the hormone-dependent MCF7 breast cancer cell line, the observed effect seems to be the result of two components, one cytotoxic (antiproliferative), the other estrogenic (proliferative). Electrochemical studies show that the cytotoxic effect of the complexes correlates with the ease of oxidation of the ferrocene group. All these complexes are much less cytotoxic than the ferrocenyl diphenol butene derivative.

432: Proteasome Inhibitor MG132 Induces Death Receptor 5 (DR5) Through CCAAT/Enhancer-Binding Protein Homologous Protein (CHOP) and Enhances Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL/AP02L)-Induced Apoptosis in DU145, Human Hormone-Independent Prostate Cancer Cells

You have accessJournal of UrologyDiscussed Poster, Sunday, May 21, 2006, 1:00 - 4:00 pm1 Apr 2006432: Proteasome Inhibitor MG132 Induces Death Receptor 5 (DR5) Through CCAAT/Enhancer-Binding Protein Homologous Protein (CHOP) and Enhances Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL/AP02L)-Induced Apoptosis in DU145, Human Hormone-Independent Prostate Cancer Cells Takumi Shiraishi, Tatsushi Yoshida, Yoichi Mizutani, Takashi Yasuda, Terukazu Nakamura, Takeshi Nomoto, Akihiro Kawauchi, Susumu Nakata, Mana Horinaka, Toshiyuki Sakai, and Tsuneharu Miki Takumi ShiraishiTakumi Shiraishi More articles by this author , Tatsushi YoshidaTatsushi Yoshida More articles by this author , Yoichi MizutaniYoichi Mizutani More articles by this author , Takashi YasudaTakashi Yasuda More articles by this author , Terukazu NakamuraTerukazu Nakamura More articles by this author , Takeshi NomotoTakeshi Nomoto More articles by this author , Akihiro KawauchiAkihiro Kawauchi More articles by this author , Susumu NakataSusumu Nakata More articles by this author , Mana HorinakaMana Horinaka More articles by this author , Toshiyuki SakaiToshiyuki Sakai More articles by this author , and Tsuneharu MikiTsuneharu Miki More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(18)32688-0AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "432: Proteasome Inhibitor MG132 Induces Death Receptor 5 (DR5) Through CCAAT/Enhancer-Binding Protein Homologous Protein (CHOP) and Enhances Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL/AP02L)-Induced Apoptosis in DU145, Human Hormone-Independent Prostate Cancer Cells." The Journal of Urology, 175(4S), p. 140 © 2016 by American Urological AssociationFiguresReferencesRelatedDetails Volume 175Issue 4SApril 2006Page: 140 Advertisement Copyright & Permissions© 2016 by American Urological AssociationMetricsAuthor Information Takumi Shiraishi More articles by this author Tatsushi Yoshida More articles by this author Yoichi Mizutani More articles by this author Takashi Yasuda More articles by this author Terukazu Nakamura More articles by this author Takeshi Nomoto More articles by this author Akihiro Kawauchi More articles by this author Susumu Nakata More articles by this author Mana Horinaka More articles by this author Toshiyuki Sakai More articles by this author Tsuneharu Miki More articles by this author Expand All Advertisement PDF DownloadLoading ...

New perspective in the management of neuroendocrine differentiation in prostate adenocarcinoma

In this review, we will present some of the information that is known about neuroendocrine (NE) cells and differentiation in the prostate. We will then speculate on the potential role that NE differentiation in prostate carcinoma may play and how this differentiation may be clinically analysed and treated. The androgen-independent growth of prostate cancer can be caused by different mechanisms; one of these is receptor-specific paracrine or autocrine growth modulation of human prostatic cancer cells by neuropeptides secreted by NE cells. Our results affirm that different methods of androgen deprivation can influence the serum chromogranin A (CgA) levels to different extents in prostate cancer. In particular, bicalutamide produces a significantly lower increase in serum CgA compared with castration therapy. In the light of other evidence that supports a significant relationship between serum CgA levels, tissue CgA expression and NE activity, we hypothesise that bicalutamide may reduce the risk of NE cell hyperactivation in prostate cancer. It is important to determine whether increases in CgA levels and NE cell activation are associated with progression towards hormone-independent prostate cancer. We recently proposed as therapy of NE activation in hormone-independent prostate cancer, a combination of oestrogens and somatostatin analogues. The combination of ethinyl estradiol and lanreotide had a favourable toxicity profile, offered objective and symptomatic responses in patients with limited treatment options and refractoriness to conventional hormonal therapy strategies and, in particular, offered a median overall survival that was superior to the 10-month median survival in patients with hormone refractory disease. This combination therapy also sustains the novel concept in cancer treatment in which therapies may target not only cancer cells but also its microenvironment in combination, which can confer protection from apoptosis.

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MODULATION OF MDR-1 GENE BY MIF AND GSTpi WITH DRUG RESISTANCE GENERATION IN HORMONE INDEPENDENT PROSTATE CANCER

The expression of MIF and GSTpi were upregulated in prostate cancer cells with mulitdrug resistant phenotype. The aim of this study is to determine the relationship between these genes and multidrug resistance (mdr-1) gene in acquired multidrug resistance of prostate cancer. The expression of MIF, GSTpi and gp-170 in multidrug resistant (MDR) subline or native cells were determined using flow cytometry and western blotting. The mRNA level of various genes was analyzed with RT-PCR method. The chemosensitivity of tumor cells and stable transfectants to paclitaxel was measured using MTT (tetrazolium bromide) assay. The protein levels of MIF, GSTpi and gp-170 increased in MDR sublines of prostate cancer when compared with their parental cells. The MIF and GSTpi stable transfectants expressed higher MIF and GSTpi protein levels than their parental cells in western blotting analysis, respectively. The expression of mdr-1 gene and the production of pg-170 were also increased in either MIF or GSTpi stable transfectants when compared with vector control by using RT-PCR and flow cytometric analysis. The MTT results demonstrated that the increased chemoresistance was correlated with the increased production of gp-170 protein in either MIF or GSTpi transfectants. The upregulation of MIF and GSTpi during the development of acquired drug resistance of hormone independent prostate cancer may simultaneously and partially modulate the activation of gp-170.

Tocopherols and Saponins Derived from Argania spinosa Exert, an Antiproliferative Effect on Human Prostate Cancer

The aim of our study is to evaluate the antiproliferative effect of tocopherols obtained from alimentary virgin argan oil extracted from the endemic argan tree of Morocco and of saponins extracted from argan press cake on three human prostatic cell lines (DU145, LNCaP, and PC3). The results were compared to 2-methoxyestradiol as antiproliferative drug candidates. Cytotoxicity and antiproliferative effects were investigated after cells' treatment with tocopherols and saponins compared to 2-Methoxyoestradiol as the positive control. Tocopherols and saponins extracted from argan tree and 2-methoxyestradiol exhibit a dose-response cytotoxic effect and an antiproliferative action on the tested cell lines. The best antiproliferative effect of tocopherols is obtained with DU145 and LNCaP cell lines (28 μg/ml and 32 μg/ml, respectively, as GI50). The saponins fraction displayed the best antiproliferative effect on the PC3 cell line with 18 μg/ml as GI50. Our results confirm the antiproliferative effect of 2-methoxyestradiol and show for the first time the antiproliferative effect of tocopherols and saponins extracted from the argan tree on hormone-dependent and hormone-independent prostate cancer cell lines. These data suggest that argan oil is of potential interest in developing new strategies for prostate cancer prevention.

Prostate Cancer in the Elderly

Prostate cancer is the second leading cause of cancer deaths among men. Despite earlier diagnosis due to prostate specific antigen (PSA) screening, it is still a disease of the elderly. Diagnosis is based on digital rectal examination (DRE) and PSA assessment. Refinements in PSA testing (age-specific reference ranges, free PSA, PSA density and velocity) increased specificity and limited unnecessary prostate biopsies. Diagnosis in earlier stages (T1 and T2) commonly leads to cure with current treatment modalities. These include radical prostatectomy, external beam radiotherapy and brachytherapy. Other treatment options under development include cryotherapy and high-intensity focused ultrasound. Metastatic prostate cancer is incurable and treatment is based on hormonal therapy. Cytotoxic chemotherapy has only limited role in hormone-independent prostate cancer. Radioisotopes and biphosphonates may alleviate bone pain and prevent osteoporosis and pathological fractures. Follow-up is based on PSA. Prognostic factors for recurrence include stage, Gleason score, pre- and posttreatment PSA. Quality of life issues play an important role in selecting treatment, especially in the elderly due to comorbidities that may negatively affect the overall quality of life. A holistic approach is recommended addressing all quality of life issues without focus only in cancer control.

An oncolytic conditionally replicating adenovirus for hormone-dependent and hormone-independent prostate cancer

The use of conditionally replicating adenoviruses offers an attractive complementary treatment strategy for localized prostate cancer. We have produced a replicating adenovirus, Ad[I/PPT-E1A], where E1A gene expression is controlled by a recombinant regulatory sequence designated PPT. The PPT sequence comprises a PSA enhancer, a PSMA enhancer and a T-cell receptor gamma-chain alternate reading frame protein promoter, and it is shielded from transcriptional interference from adenoviral backbone sequences by an H19 insulator. Ad[I/PPT-E1A] yields prostate-specific E1A protein expression, viral replication and cytolysis in vitro. Furthermore, Ad[I/PPT-E1A] considerably regresses the growth of subcutaneous LNCaP prostate cancer tumors in nude mice. Importantly, the viral replication and cytolytic effect of Ad[I/PPT-E1A] are independent of the testosterone levels in the prostate cancer cells. This may be beneficial in a clinical setting since many prostate cancer patients are treated with androgen withdrawal. In conclusion, Ad[I/PPT-E1A] may prove to be useful in the treatment of localized prostate cancer.

Nuclear Factor-κB(NF-κB)/Interleukin-6 (IL-6) pathway activation confers resistance to docetaxel (D) in hormone-independent prostate cancer (HIPC)

9630 Background: The activation of the NF-κB/IL-6 pathway is associated with androgen-independent progression of prostate cancer (PC) and may be implicated in resistance to chemotherapy. We investigated the role of NF-κB/IL-6 in the response to D in human PC cell lines and in HIPC pts, and the inhibition of NF-κB as a strategy to increase chemosensitivity in PC cells. Methods: The hormone-dependent (LNCaP) and hormone-independent (PC-3, DU-145) PC cells were treated with D+/- PS-1145 (specific IκB kinase 2 inhibitor). Cells were tested for activated p65/ NF-κB (western blot using anti-p65NLS antibody), IL-6 in culture medium (ELISA) and cell viability (MTT). Pts with metastatic HIPC receiving D were tested for plasma IL-6 (ELISA) before the start and every 3–4 weeks until the end of D. Results: In vitro sensitivity towards D was lower for p65NLS expressing and IL-6 producing cells (PC3, DU145) versus LNCaP, with lower p65NLS and no IL-6 production. Media IL-6 increased in both PC-3 and DU-145 after D trea...

The association of Id-1, MIF and GSTpi with acquired drug resistance in hormone independent prostate cancer cells

Most patients with prostate cancer respond to androgen ablation therapy, but the tumor eventually progresses to an androgen-independent stage with multiple anti-cancer drug resistance. Novel therapeutic strategies for hormone independent prostate cancer need to be developed. The genes for Id-1, MIF and GSTpi were up-regulated in drug resistant cells of hormone independent prostate cancer cells using cDNA microarray gene expression analysis. In this study we aimed to investigate whether constitutive overexpression of these candidate genes in cells can affect cellular resistance to chemotherapeutic agents. The mRNA expression was determined by reverse transcriptase-polymerase chain reaction, and the Id-1, MIF and GSTpi protein contents in these cell lines were measured by Western blotting. Susceptibility of the cells to chemotherapeutic agents including doxorubicin, paclitaxel and cyclophosphamide was determined by microculture tetrazolium bromide assay. The analysis of apoptosis was assessed by annexin V assay. The cytotoxity assay results demonstrated that cells overexpressing the Id-1 gene increased in their resistance to doxorubicin, paclitaxel and cyclophosphamide. MIF expression can drive cells to increase in their resistance to paclitaxel, and GSTpi expression confers drug resistance to doxorubicin and cyclophosphamide. The induction of mdr1 gene expression was noted in up-regulation of MIF and GSTpi. Our findings suggest that overproduction of the Id-1, MIF and GSTpi proteins and coinduction of mdr-1 play an important role in the development of acquired drug resistance to various drugs of prostate cancer cells.

Signal transduction in prostate cancer progression

Prostate cancer is the most frequently diagnosed cancer among men and the second leading cause of male cancer deaths in the United States. When prostate cancer initially presents in the clinic, the tumour is dependent on androgen for growth and, therefore, responsive to the surgical or pharmacological ablation of circulating androgens. However, there is a high rate of treatment failure because the disease often recurs as androgen-independent metastases. Surprisingly, this late-stage androgen-independent prostate cancer almost always retains expression of the AR (androgen receptor), despite the near absence of circulating androgens. Although late-stage prostate cancer is androgen-independent, the AR still seems to play a role in cancer cell growth at this stage of disease. Therefore a key to understanding hormone-independent prostate cancer is to determine the mechanism(s) by which the AR can function even in the absence of physiological levels of circulating androgen. This review will focus on the role of growth factor signalling in prostate cancer progression to androgen independence and thus outline potential molecular areas of intervention to treat prostate cancer progression.

Receptor for advanced glycation end products (RAGE) and its ligand, amphoterin are overexpressed and associated with prostate cancer development

Advanced glycation end products (AGE) are produced with normal aging. Recently, some reports indicated that the interaction between AGE and the cognate receptor (RAGE) has a role in cancer dependent. We investigated RAGE and amphoterin mRNA expression in prostate cancer cell lines (DU145, PC-3, and LNCaP cells), hormone-refractory prostate cancer tissues, and paired untreated primary prostate cancer and normal prostate (including benign prostatic hypertrophy (BPH)) tissues using real-time quantitative PCR. Moreover, to confirm the AGE-RAGE interaction in prostate cancer, DU145 cells stimulated with AGE-bovine serum albumin (AGE-BSA) were examined by in vitro matrigel assay, cell viability assay, MTT assay, reverse transcription-polymerase chain reaction (RT-PCR), and Western blot. DU145 cells, a hormone-independent prostate cancer cell line, showed the highest RAGE mRNA expression. Amphoterin mRNA was expressed in all three cell lines. In prostate tissues, untreated prostate cancer tissue and hormone-refractory prostate cancer tissue showed higher RAGE and amphoterin mRNA expression than normal prostate tissue. The AGE-RAGE interaction induced the invasion and growth in DU145 cells stimulated with AGE-BSA. The AGE-RAGE interaction is important in prostate cancer development, and inhibition of this interaction has potential as a new molecular target for cancer therapy or prevention.

Targeting Prostate Cancer with Conditionally Replicative Adenovirus Using PSMA Enhancer

Prostate cancer is the second most commonly diagnosed cancer in men and accounts for significant mortality and morbidity in the United States. Initially androgen-dependent, prostate cancer ultimately becomes androgen-independent, which makes the disease extremely difficult to cure. In this study, we examined the use of conditionally replication-competent adenovirus for the treatment of hormone-independent prostate cancer. We utilized PSME, an enhancer element for prostate-specific PSMA expression, to control viral E1A protein expression and achieve exclusive virus replication in prostate. Western blotting confirmed that PSME mediated high E1A protein expression in PSMA-positive, androgen-independent prostate cancer cells (C4-2 and CWR22rv), but was much less active in PSMA-negative cancer cells (PC-3 and A549). Consistent with E1A protein expression, the recombinant adenovirus Ad5-PSME-E1a replicated in C4-2 and CWR22rv almost as efficiently as wild type with low levels of androgen, but its replication was significantly attenuated in PSMA-negative cells. In the in vitro killing assay, Ad5-PSME-E1a lysed all C4-2 and CWR22rv cells 5 days after infection, with minimal effect on PSMA-negative cells. In addition, injections of 1.7 x 10(8) plaque-forming units in a CWR22rv xenograft model in nude mice induced significant tumor growth delay, with a substantial necrotic area. These studies suggest that PSME-driven replication-competent adenovirus may be a new therapeutic modality for prostate cancer patients after hormone ablation therapy.

P42/p44 Mitogen‐Activated Protein Kinase Signal Transduction Pathway: A Novel Target for the Treatment of Hormone‐Resistant Prostate Cancer?

Prostate cancer is the second leading cause of cancer deaths in men. Conventional therapies produce a high rate of cure for patients with localized prostate cancer, but there is no cure once the disease has spread beyond the prostate. Androgen withdrawal remains the only treatment for these men with clinically advanced disease; however, most of these men, who initially respond to hormone ablation therapy, fail and the disease progresses. There is at present no effective treatment for hormone-independent prostate cancer. Several lines of evidence suggest a role of p42/p44 mitogen-activated protein kinase (p42/p44 MAP kinase) signal transduction pathways in prostate cancer. At the molecular level, a variety of genetic alterations lead to an epigenetic mechanism by which a feedback autocrine loop between membrane receptors and associated ligands serves as an essential component of the growth, proliferation, and metastasis of prostate cancer at an advanced and androgen-independent stage. Peptide growth factors are known to exert their effects by a complex array of mechanisms primarily mediated by the p42/p44 MAP kinase signal transduction pathway. Thus, we hypothesized that MAP kinase signal transduction pathways could serve as new and novel targets in prostate cancer therapy. In this article we provide an overview of the role played by MAP kinase signal transduction in the prostate.

Analysis of Wnt Gene Expression in Prostate Cancer

The Wnt signaling pathway is aberrantly activated in many tumor types, including those of the prostate, in which beta-catenin accumulates in cell nuclei and acts as a transcriptional coregulator for the androgen receptor. Because activating mutations in the beta-catenin gene are rare in prostate cancer, we have looked for altered expression of other components of the Wnt signaling pathway in prostate cancer cells. Here we determined the expression levels of Wnt family genes in cultured human prostate cells and prostate cancer cell lines. We found that WNT11 expression is elevated in hormone-independent prostate cancer cell lines. Additional analysis indicated that WNT11 expression is also elevated in high-grade prostatic tumors and in hormone-independent xenografts. Growth of hormone-dependent LNCaP cells in hormone-depleted media led to increased WNT11 expression, which was repressed by the synthetic androgen R1881. This repression was inhibited by the antiandrogen bicalutamide, suggesting that androgens negatively regulate WNT11 expression through the androgen receptor. Expression of WNT11 inhibited androgen receptor transcriptional activity and cell growth in androgen-dependent cells but not in androgen-independent cells. WNT11 inhibited activation of the canonical Wnt pathway by WNT3A in HEK 293 cells and inhibited basal beta-catenin/Tcf transcriptional activity in LNCaP cells. However, expression of stabilized beta-catenin did not prevent the inhibition of androgen receptor transcriptional activity by WNT11. Our observations are consistent with a model in which androgen depletion activates WNT11-dependent signals that inhibit androgen-dependent but not androgen-independent cell growth.

674. Improved Therapy of Prostate Carcinoma with TRAIL Gene Delivery Using Flt-1 Promoter Element in Combination with Ionizing Radiation

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL/Apo2L) is of particular interest in the development of prostate carcinoma therapeutics as it preferentially induces apoptosis of tumor cells. Several potential problems for recombinant TRAIL, including requirements of large amounts for treatment, short circulating half-life, and cytotoxicity against normal human hepatocytes, could limit the effectiveness of this anti-cancer agent. One way to overcome these limitations is to employ adenoviral vectors for high-efficiency and specific TRAIL gene transfer into cancer cells. The vascular endothelial growth factor (VEGF) and its cognate receptors Flt-1 and Flk-1 are involved in regulation of angiogenesis and tumor growth, invasion and metastasis of prostate carcinoma. VEGF receptor Flt-1 expression is observed in both tumor endothelial cells and prostate cancer cells. We hypothesized that selective transcriptional targeting of TRAIL gene expression under control of the Flt-1 promoter would increase specificity and efficiency of prostate cancer therapy in combination with ionizing radiation. We developed an adenoviral vector encoding the TRAIL gene under control of the Flt-1 promoter element (AdFlt-TRAIL), which produced prostate cancer cell death as well as endothelial cell death. Our results reveal that prostate cancer cells were relatively resistant to soluble TRAIL protein. Cell viability of DU145 and PC-3 cells was 75% and 77% following incubation for 96 h with soluble TRAIL at 400 ng/ml, respectively. Although hormone-responsive LNCaP prostate cancer cells demonstrated a lower level of Flt-1 promoter activity in comparison with hormone-independent (DU145 and PC-3) human prostate cancer cells, AdFlt-TRAIL produced increased cytotoxicity to LNCaP (p53-wildtype) and DU145 (p53-mutant) cells in comparison with PC-3 (p53-negative). Ionizing radiation at 3 Gy increased LacZ expression driven by the Flt-1 promoter by 61 % in DU145 human prostate cancer cells and 48 % in SVEC 4-10 murine endothelial cells. The combination of radiation treatment and AdFlt-TRAIL transduced overexpression of TRAIL overcame TRAIL resistance of human prostate cancer cells in vitro. Relative cell viability of DU145 cells was 90% at 72 h after radiation treatment (2 Gy) alone, 46% at 96 h after AdFlt-TRAIL infection (100 MOI) alone, and 15% for their combination. AdFlt-TRAIL-mediated apoptosis involved cleavage of caspase-3, and PARP, and required caspase-8 and -9 activity. Furthermore, in vivo administration of AdFlt-TRAIL at the site of tumor growth in combination with radiation treatment produced significant suppression of the growth of DU145 human prostate tumor xenografts in athymic nude mice. Our results suggest that specific TRAIL delivery employing the Flt-1 promoter can effectively inhibit tumor growth and demonstrate the advantage of combination radiotherapy and gene therapy for the treatment of prostate cancer.