Novel strategies and therapeutics for the treatment of prostate carcinoma

VIP induces NF-κB1-nuclear localisation through different signalling pathways in human tumour and non-tumour prostate cells

The nuclear factor κB (NF-κB) is a powerful activator of angiogenesis, invasion and metastasis. Transactivation and nuclear localisation of NF-κB is an index of recurrence in prostate cancer. Vasoactive intestinal peptide (VIP) exerts similar effects in prostate cancer models involving increased expression of vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2) which are related to NF-κB transactivation. Here we studied differential mechanisms of VIP-induced NF-κB transactivation in non-tumour RWPE-1 and tumour LNCaP and PC3 human prostate epithelial cells. Immunofluorescence studies showed that VIP increases translocation of the p50 subunit of NF-κB1 to the nucleus, an effect that was inhibited by curcumin. The signalling transduction pathways involved are different depending on cell transformation degree. In control cells (RWPE1), the effect is mediated by protein kinase A (PKA) activation and does not implicate extracellular signal-regulated kinase (ERK) or phosphoinositide 3-kinase (PI3-K) pathways whereas the opposite is true in tumour LNCaP and PC3 cells. Exchange protein directly activated by cAMP (EPAC) pathway is involved in transformed cells but not in control cells. Curcumin blocks the activating effect of VIP on COX-2 promoter/prostaglandin E2 (PGE2) production and VEGF expression and secretion. The study incorporates direct observation on COX-2 promoter and suggests that VIP effect on VEGF may be indirectly mediated by PGE2 after being synthesised by COX-2, thus amplifying the initial signal. We show that the signalling involved in VIP effects on VEGF is cAMP/PKA in non-tumour cells and cAMP/EPAC/ERK/PI3K in tumour cells which coincides with pathways mediating p50 nuclear translocation. Thus, VIP appears to use different pathways for NF-κB1 (p50) transactivation in prostate epithelial cells depending on whether they are transformed or not. Transformed cells depend on pro-survival and pro-proliferative signalling pathways involving ERK, PI3-K and cAMP/EPAC which supports the potential therapeutic value of these targets in prostate cancer.

Antineoplastic effect of beta-elemene on prostate cancer cells and other types of solid tumour cells

OBJECTIVES

beta-Elemene, a natural compound extracted from over 50 different Chinese medicinal herbs and plants, has been effective in the treatment of hyperplastic and proliferative disorders such as prostatic hypertrophy, hysteromyoma and neoplasms. Our previous studies have demonstrated that beta-elemene exhibits strong inhibitory activity in ovarian cancer cells. The aim of the present study was to assess the effect of beta-elemene on prostate cancer cells as well as other types of tumour cells and to determine whether the effect of beta-elemene on prostate cancer cell death was mediated through the induction of apoptosis.

METHODS

The MTT assay was used to evaluate the ability of beta-elemene to inhibit cellular proliferation in cancer cells. Cellular apoptosis was assessed by annexin V binding, TUNEL and ELISA-based assays. Caspase activity was measured using a caspases assay kit. The protein levels of Bcl-2, caspases, cytochrome c and poly(ADP-ribose) polymerase (PARP) were analysed by Western blotting.

KEY FINDINGS

Here, we showed that beta-elemene had an antiproliferative effect on androgen-insensitive prostate carcinoma DU145 and PC-3 cells. Treatment with beta-elemene also inhibited the growth of brain, breast, cervical, colon and lung carcinoma cells. The effect of beta-elemene on cancer cells was dose dependent, with IC50 values ranging from 47 to 95 microg/ml (230-465 microm). TUNEL assay and flow cytometric analysis using annxin V/propidium iodide staining revealed that the percentage of apoptotic prostate cancer cells was increased by beta-elemene in a dose- and time-dependent manner. Moreover, beta-elemene exposure resulted in a decreased Bcl-2 protein level, increased cytochrome c release, and activated PARP and caspase-3, -7, -9, and -10 in prostate cancer cells.

CONCLUSIONS

Overall, these findings suggest that beta-elemene exerts broad-spectrum antitumour activity against many types of solid carcinoma and supports a proposal of beta-elemene as a new potentially therapeutic drug for castration-resistant prostate cancer and other solid tumours.

Antiprostasome antibodies are not an appropriate prognostic marker for prostate cancer

OBJECTIVE

Antiprostasome antibodies (APAs) have been identified in serum of patients with prostate cancer and have been proposed as a new marker for metastatic disease. This study reassesses the role of APAs as a prognostic indicator for prostate cancer.

MATERIAL AND METHODS

Serum samples from healthy controls (n=7) and patients with prostate cancer (n=22) were assayed for APAs using an enzyme-linked immunosorbent assay.

RESULTS

APAs in varying amounts were present in healthy individuals as well as in men with prostate cancer. Higher levels were inversely and significantly associated with prostate-specific antigen (PSA). No significant relationships were noted between APA levels and other parameters such as age, time since diagnosis, metastatic status, Gleason histological score and hormonal treatment.

CONCLUSIONS

The presence of serum APA is unlikely to be a strong prognostic indictor for prostate cancer on an individual basis as false positives will occur. However, such immune reactions which may be associated with PSA in cancer patients are in any case of interest in both the biology of prostate cancer and male fertility. The source of prostasomal antigen may be of critical importance to the outcome of the assay. However, immune reactions to prostasomes may be of considerable interest and warrant continued investigation.

NF-κB2 processing and p52 nuclear accumulation after androgenic stimulation of LNCaP prostate cancer cells

Several reports suggest that androgen signalling interferes with canonical RelA-p50 activity in androgen-sensitive cells. Whether this also occurs with non-canonical NF-kappaB subunits has not been studied. Here we report that androgenic stimulation of LNCaP cells with the androgen analogue R1881 appears to positively regulate the non-canonical NF-kappaB pathway as p52 accumulates both in the cytoplasm and nucleus after 48-72 h of stimulation. In contrast to TNF-alpha stimulation, androgen stimulation fails to induce RelB expression and is absent from nucleus of R1881-treated LNCaP cells. Electromobility shift assays reveal a time-dependent change in the nature of NF-kappaB complexes actively bound to DNA after 72 h of androgenic stimulation concomitant with the appearance of p52-containing complexes. Co-immunoprecipitation studies indicate that newly produced p52 can exist as a heterodimer with RelA or p50, but may be mainly present as a homodimer. RNAi experiments targeting IKK-alpha and IKK-beta show that the R1881-induced nuclear accumulation of p52 is IKK-alpha-dependent. These results point to a novel mechanism by which androgens regulate NF-kappaB and provide a rationale for further studies into the biological significance of non-canonical NF-kappaB signalling in prostate cancer.

Regulation of IkappaB kinase epsilon expression by the androgen receptor and the nuclear factor-kappaB transcription factor in prostate cancer

Although several genes have been associated with prostate cancer progression, it is clear that we are far from understanding all the molecular events implicated in the initiation and progression of the disease to a hormone-refractory state. The androgen receptor is a central player in the initiation and proliferation of prostate cancer and its response to hormone therapy. Nuclear factor-kappaB has important proliferative and antiapoptotic activities that could contribute to the development and progression of cancer cells as well as resistance to therapy. In this study, we report that IkappaB kinase epsilon (IKKepsilon), which is controlled by nuclear factor-kappaB in human chondrocytes, is expressed in human prostate cancer cells. We show that IKKepsilon gene expression is stimulated by tumor necrosis factor-alpha treatment in LNCaP cells and is inhibited by transfection of a dominant-negative form of IkappaBalpha, which prevents the nuclear translocation of p65. Furthermore, we found that tumor necrosis factor-alpha-induced IKKepsilon expression is inhibited by an androgen analogue (R1881) in androgen-sensitive prostate cancer cells and that this inhibition correlates with the modulation of IkappaBalpha expression by R1881. We also noted constitutive IKKepsilon expression in androgen-independent PC-3 and DU145 cells. To our knowledge, this is the first report of an IkappaB kinase family member whose expression is modulated by androgen and deregulated in androgen receptor-negative cells.

Type II combi-molecules: design and binary targeting properties of the novel triazolinium-containing molecules JDD36 and JDE05

We recently designed molecules termed "type II combi-molecules" to block the epidermal growth factor receptor and to damage DNA without the requirement for hydrolytic cleavage. Here, we studied two such combi-molecules (JDD36 and JDE05), containing a novel quinazoline-linked chloroethyltriazolinium system. The epidermal growth factor receptor-targeting potential of these novel structures was studied by ELISA for isolated epidermal growth factor receptor and by Western blotting for whole-cell assays. DNA damage was analyzed using the single-cell microelectrophoresis comet assay. Antiproliferative effects were determined by the sulforhodamine B assay. JDD36 showed an IC50 of 0.6 micromol/l in the ELISA for epidermal growth factor receptor tyrosine kinase, a dose-dependent inhibition of epidermal growth factor receptor phosphorylation and significant levels of DNA damage in the human DU145 prostate cancer cell line. JDD36 was an overall 2- to 15-fold stronger antiproliferative agent than JDE05 that showed potent epidermal growth factor receptor inhibitory activity (IC50 epidermal growth factor receptor, 0.035 micromol/l) but weak DNA-damaging potential. In a panel of LNCaP erbB transfectants, in contrast to JDE05, JDD36 showed remarkable and selective potency against the LNCaPerbB2 transfectant. The results in toto suggest that the overall superior potency of JDD36 when compared with JDE05 may be imputed to its balanced binary epidermal growth factor receptor-DNA-targeting properties that may induce a tandem blockade of epidermal growth factor receptor-mediated mitogenic signaling while depleting alternative survival mechanism by damaging DNA.

Suberoylanilide hydroxamic acid (vorinostat) represses androgen receptor expression and acts synergistically with an androgen receptor antagonist to inhibit prostate cancer cell proliferation

Growth of prostate cancer cells is initially dependent on androgens, and androgen ablation therapy is used to control tumor growth. Unfortunately, resistance to androgen ablation therapy inevitably occurs, and there is an urgent need for better treatments for advanced prostate cancer. Histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid (SAHA; vorinostat), are promising agents for the treatment of a range of malignancies, including prostate cancer. SAHA inhibited growth of the androgen-responsive LNCaP prostate cancer cell line at low micromolar concentrations and induced caspase-dependent apoptosis associated with chromatin condensation, DNA fragmentation, and mitochondrial membrane depolarization at higher concentrations (>/=5 mumol/L). Gene profiling and immunoblot analyses showed a decrease in androgen receptor (AR) mRNA and protein in LNCaP cells cultured with SAHA compared with control cells, with a corresponding decrease in levels of the AR-regulated gene, prostate-specific antigen. Culture of LNCaP cells in steroid-free medium markedly sensitized the cells to SAHA. Moreover, a combination of low, subeffective doses of SAHA and the AR antagonist bicalutamide resulted in a synergistic reduction in cell proliferation and increase in caspase-dependent cell death. Addition of exogenous androgen prevented the induction of cell death, indicating that suppression of androgen signaling was required for synergy. At the subeffective concentrations, these agents had no effect, alone or in combination, on proliferation or death of AR-negative PC-3 prostate cancer cells. Our findings indicate that SAHA is effective in targeting the AR signaling axis and that androgen deprivation sensitizes prostate cancer cells to SAHA. Consequently, combinatorial treatments that target different components of the AR pathway may afford a more effective strategy to control the growth of prostate cancer cells.

The Combi-Targeting Concept: In vitro and In vivo Fragmentation of a Stable Combi-Nitrosourea Engineered to Interact with the Epidermal Growth Factor Receptor while Remaining DNA Reactive

PURPOSE

JDA58 (NSC 741282), a "combi-molecule" optimized in the context of the "combi-targeting concept," is a nitrosourea moiety tethered to an anilinoquinazoline. Here, we sought to show its binary epidermal growth factor receptor (EGFR)/DNA targeting property and to study its fragmentation in vitro and in vivo.

EXPERIMENTAL DESIGN

The fragmentation of JDA58 was detected in cells in vitro and in vivo by fluorescence microscopy and tandem mass spectrometry. EGFR phosphorylation and DNA damage were determined by Western blotting and comet assay, respectively. Tumor data were examined for statistical significance using the Student's t test.

RESULTS

JDA58 inhibited EGFR tyrosine kinase (IC(50), 0.2 micromol/L) and blocked EGFR phosphorylation in human DU145 prostate cancer cells. It induced significant levels of DNA damage in DU145 cells in vitro or in vivo and showed potent antiproliferative activity both in vitro and in a DU145 xenograft model. In cell-free medium, JDA58 was hydrolyzed to JDA35, a fluorescent amine that could be observed in tumor cells both in vitro and in vivo. In tumor cells in vitro or in vivo, or in plasma collected from mice, the denitrosated species JDA41 was the predominant metabolite. However, mass spectrometric analysis revealed detectable levels of the hydrolytic product JDA35 in tumor cells both in vitro and in vivo.

CONCLUSIONS

The results in toto suggest that growth inhibition in vitro and in vivo may be sustained by the intact combi-molecule plus JDA35 plus JDA41, three inhibitors of EGFR, and the concomitantly released DNA-damaging species. This leads to a model wherein a single molecule carries a complex multitargeted-multidrug combination.

Flap endonuclease 1 is overexpressed in prostate cancer and is associated with a high Gleason score

OBJECTIVE

To investigate the expression and potential clinical usefulness of structure-specific flap endonuclease 1 (FEN-1) in human primary prostate cancer using tissue microarray technology, as FEN-1 was recently identified to be overexpressed in CL1.1, the most aggressive clone generated from the hormone-refractory prostate cancer cell line CL1.

MATERIALS AND METHODS

Immunohistochemistry was performed on tissue microarrays constructed from paraffin-embedded specimens of primary prostate cancer from 246 patients who had had a radical prostatectomy. Prostatic intraepithelial neoplasia (PIN), benign prostatic hyperplasia (BPH) and normal prostate epithelium were represented on the array. FEN-1 nuclear expression was scored based on the percentage of target cells staining positively, and correlated with Gleason score, preoperative prostate-specific antigen (PSA) level and pathological stage. The time to PSA recurrence was also analysed.

RESULTS

The mean expression of FEN-1 was significantly higher in cancer (36.7%) than in normal (13.2%), BPH (4.5%) and PIN (15.4%) specimens (P < 0.001). FEN-1 expression was significantly correlated with Gleason score (ó = 0.23, P = 0.002). A higher preoperative serum PSA level (P = 0.015), Gleason score > or = 7 (P < 0.001), seminal vesicle invasion (P < 0.001) and capsular involvement (P = 0.004) were associated with PSA recurrence, whereas FEN-1 expression was not. In a multivariate analysis, only Gleason score > or = 7 (P < 0.001), seminal vesicle invasion (P = 0.005) and capsular involvement (P = 0.009) were retained as independent predictors for PSA recurrence.

CONCLUSIONS

FEN-1 is overexpressed in prostate cancer compared with matched normal prostate, and its expression increases with tumour dedifferentiation, as shown by increasing Gleason score. These results suggest that FEN-1 might be a potential marker for selecting patients at high risk, and a potential target for prostate cancer diagnosis and therapy.

Inhibition of human experimental prostate cancers by a targeted cytotoxic luteinizing hormone-releasing hormone analog AN-207

BACKGROUND

Receptors for luteinizing hormone-releasing hormone (LHRH) on human prostate cancers can be used for targeted chemotherapy with cytotoxic analogs of LHRH, such as AN-207, which consists of superactive doxorubicin derivative 2-pyrrolino doxorubicin (AN-201) linked to carrier [D-Lys6] LHRH.

METHODS

The effects of AN-207 and AN-201 were investigated in DU-145 androgen independent and LuCaP-35 androgen sensitive human prostate cancers xenografted into nude mice. Toxicity was evaluated by survival rates, changes in body weights, and leukocyte counts. LHRH receptors on DU-145 and LuCaP-35 tumors were evaluated by radioreceptor assays and RT-PCR. The effects on apoptosis and cell proliferation were investigated by histology and evaluation of apoptotic oncogenes Bcl-2 and Bax by Western Blot analysis.

RESULTS

AN-207 inhibited growth of DU-145 tumors significantly by 75% (P < 0.01) and LuCaP-35 human prostate cancers by 80% (P < 0.01), and was less toxic than AN-201. Receptors for LHRH were expressed on DU-145 and LuCaP-35 tumors. Blockade of LHRH receptors with LHRH agonist Triptorelin nullified the effects of AN-207. Treatment with AN-207, but not with AN-201, decreased Bcl-2/Bax ratio in DU-145 tumors and Bcl-2 in LuCaP-35 tumors indicating an increase in apoptotic activity. AN-207, but not AN-201, decreased cell proliferation in both models.

CONCLUSIONS

Targeted chemotherapy with AN-207 could be considered for treatment of advanced prostate cancer.

Prostate stem cell antigen is overexpressed in prostate cancer metastases

PURPOSE

Prostate stem cell antigen (PSCA) is expressed by a majority of prostate cancers and is a promising therapeutic target. PSCA protein and mRNA expression was examined in prostate cancer bone, lymph node, and visceral metastases to assess the potential of PSCA as an immunotherapeutic target in advanced prostate cancer.

EXPERIMENTAL DESIGN

Immunohistochemical analysis of PSCA protein expression and quantitative mRNA expression analysis of PSCA was done on clinical specimens of prostate cancer bone, lymph node, and visceral metastases. PSCA protein and mRNA expression levels were quantified and compared between available matched pairs of bone and lymph node or visceral metastases.

RESULTS

Bone metastases stained with higher intensity of PSCA compared with lymph node or liver metastases in seven of eight (87.5%) matched pairs (P = 0.035). PSCA mRNA expression was equal or greater than that of LAPC-9, a PSCA expressing xenograft, in 12 of 24 (50%) cases of prostate cancer metastases and was significantly correlated with PSCA protein expression (sigma = 0.84, P = 0.0019). Overall, PSCA protein expression was detected in 41 of 47 (87.2%), four of six (66.7%), and two of three (66.7%) cases of bone, lymph node, and liver metastases, respectively. Mean PSCA staining intensity was significantly higher in prostate cancer bone metastases compared with lymph node metastases (2.0 +/- 0.02 versus 0.83 +/- 0.31, P = 0.014).

CONCLUSIONS

Prostate cancer metastases express PSCA. However, greater PSCA staining intensity and level of PSCA mRNA expression was associated with bone metastases compared with lymph node metastases. This study suggests that PSCA is a promising tumor marker and potential therapeutic target for patients with metastatic prostate cancer.

Antisense therapy: recent advances and relevance to prostate cancer

Currently employed treatment options for patients with advanced and metastatic cancer such as surgery, radiation, hormone therapy, and chemotherapy are limited. In particular, the well known limitations of chemotherapy are at least in part due to a lack of specificity. The activation of dominant oncogenes and inactivation of tumor suppressor genes may represent novel targets for cancer therapy. Antisense therapy has been widely used to specifically and selectively inhibit the expression of selected genes at the messenger RNA level. Combinations of antisense oligonucleotides with chemotherapeutic agents may offer important advantages in cancer treatment. Several antisense drugs, especially oblimersen (G3139), have shown interesting results in experiments in animals, and have entered clinical trials. However, control oligonucleotides must be carefully chosen to separate antisense effects from the many potential nonspecific effects of oligonucleotides. This review summarizes the advantages and limitations of antisense therapy and its use in the treatment of androgen-independent prostate cancer.

National Cancer Institute intramural approach to advanced prostate cancer

Adenocarcinoma of the prostate is the most common cancer diagnosed in men in the United States, with approximately 189,000 new cases estimated to be diagnosed in 2002. It is believed that men with this disease pass through a series of clinical states. In the intramural program of the National Cancer Institute, we have designed clinical trials that have addressed each disease state. In addition to clinical endpoints, each trial also encompasses molecular or immunologic endpoints in an attempt to determine if our therapy is acting on its presumed target. In patients with localized disease, we are evaluating cancer vaccines in combination with radiation therapy as well as comparing this vaccine against second-line hormonal therapy in patients with rising serum prostate-specific antigen (PSA) but no radiographically measurable disease. We are also evaluating the ability of the antiangiogenesis agent thalidomide to prolong the rest period in patients with a biochemical recurrence (stage D0) that are receiving intermittent hormonal therapy. In patients with metastatic prostate cancer, we are evaluating the addition of the bisphosphonate alendronate when added to ketoconazole for impact on matrix metalloproteinase (MMP)-2 and MMP-9 as well as traditional clinical endpoints. In addition, we have 3 ongoing trials involving the chemotherapeutic agent docetaxel. One trial is examining the combination of thalidomide with docetaxel. The other 2 trials are exploring the PSA vaccine with docetaxel and the combination of docetaxel with ketoconazole. As we obtain information from these ongoing studies, we will be able to take this information and integrate it in the development of newer and more successful treatment regimens as well as look for novel agents that may help in the fight against this disease.

Inhibition of cell signaling by the combi-nitrosourea FD137 in the androgen independent DU145 prostate cancer cell line

BACKGROUND

FD137, a nitrosourea appended to a quinazoline ring, was designed to simultaneously block epidermal growth factor receptor (EGFR)-mediated signaling and damage genomic DNA in refractory EGF-dependent prostate tumors.

METHODS

The mixed inhibition of cell signaling and DNA damage by FD137 were determined by Western blotting, RT-PCR, flow cytometry, sulforhodamine B (SRB), and comet assay.

RESULTS

FD137 and its metabolite FD110 induced a dose-dependent increase in inhibition of EGF-stimulated EGFR autophosphorylation and this translated into blockade of c-fos gene expression in DU145 cells. FD137 induced significant levels of DNA damage and showed 150-fold greater anti-proliferative activity than BCNU, a classical nitrosourea. In contrast to BCNU, complete inhibition of EGF-induced cell transition to S-phase was observed at concentrations of FD137 as low as 3 microM.

CONCLUSION

FD137 could not only damage DNA, but also significantly block downstream EGFR-mediated signaling. The superior activity of FD137 may be imputable to the combined effect of its mixed EGFR/DNA targeting properties. This novel strategy may well represent a new approach to target nitrosoureas to EGFR-overexpressing carcinomas of the prostate.

Aryl hydrocarbon receptor-mediated inhibition of LNCaP prostate cancer cell growth and hormone-induced transactivation

LNCaP prostate cancer cells express the aryl hydrocarbon receptor (AhR), and treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces CYP1A1 protein and an Ah-responsive reporter gene. Similar results were obtained with the selective AhR modulator 6-methyl-1,3,8-trichlorodibenzofuran (6-MCDF); however, TCDD but not 6-MCDF induced degradation of the AhR protein. TCDD and 6-MCDF inhibited growth of LNCaP cells, and inhibitory AhR-androgen receptor (AR) crosstalk was investigated in cells transfected with constructs containing the androgen-responsive probasin promoter (-288 to +28) (pPB) or three copies of the -244 to -96 region of this promoter (pARR(3)). Ten nanomolar dihydrotestosterone (DHT) and 17 beta-estradiol (E2) induced transactivation in LNCaP cells transfected with pPB or pARR(3); however, inhibitory AhR-AR crosstalk was observed only with the latter construct. 6-MCDF and TCDD did not inhibit DHT- or E2-induced transactivation in ZR-75 human breast cancer cells, indicating that these interactions were promoter and cell context-dependent. Both E2 and DHT stabilized AR protein in LNCaP cells; however, cotreatment with TCDD or 6-MCDF decreased AR protein levels. These results indicate that inhibitory AhR-AR crosstalk in prostate cancer cells is complex and for some responses, AR protein stability may play a role.

Prostate cancer: a dynamic illness with shifting targets

Despite high response rates and palliative clinical benefits, androgen ablation does not cure advanced prostate cancer because of the inevitable emergence of resistant cells. Many new therapies under development for prostate cancer target pathways and molecules that contribute to the growth and survival of these cells. The rational and effective use of targeted therapies to eradicate resistant populations of tumour cells should be grounded on the premise that prostate cancer is a dynamic disease that evolves as it progresses, and that specific molecular determinants mediating sensitivity and resistance may be relevant only during specific states of the disease. Directed approaches must account for this changing dynamic so that clinical outcomes may be improved.

Suppression of LNCaP prostate cancer xenograft tumors by a prostate-specific protein tyrosine phosphatase, prostatic acid phosphatase

BACKGROUND

Although the molecular mechanism of androgen-independent prostate cancer growth and progression has been gradually elucidated, there is limited effective treatment for this prevalent disease. Human prostatic acid phosphatase (PAcP), a major protein tyrosine phosphatase in prostate epithelium, plays a critical role in regulating the growth of prostate cancer cells. In prostate carcinomas, the expression of cellular PAcP decreases. To explore directly the possible therapeutic potential of cellular PAcP, we investigated the suppression effect of PAcP by utilizing cDNA direct intratumoral administration in androgen-independent LNCaP xenograft tumors.

METHODS

An androgen-independent LNCaP cell model (C-33 and C-81 cells) and stable subclones of PAcP cDNA-transfected C-81 cells (LNCaP-23 and LNCaP-34 cells) were used for the experiments. We examined the growth property and expression of PAcP and c-ErbB-2 of these different LNCaP cells in vitro and in vivo. We subsequently investigated the growth suppression effect of PAcP cDNA intratumoral injection in pre-established C-81 xenograft tumors, and analyzed the expression of PAcP, prostate-specific antigen (PSA), proliferating cell nuclear antigen (PCNA), and c-ErbB-2 in the tumors by immunohistochemistry and Western blotting.

RESULTS

The different LNCaP cells exhibited different growth property and tumorigenicity, both in cell culture and xenograft. Biochemical characterizations revealed that the level of cellular PAcP correlated negatively with the growth property of different LNCaP cells, while the level of tyrophosphorylated c-ErbB-2 had an inverse correlation with cellular PAcP. The single intratumoral administration of the wild type PAcP cDNA showed a significant suppression effect on C-81 xenograft tumor growth, compared to vector alone-injected control (P<0.05). In the tumors injected with this PAcP cDNA, the PAcP expression was detected 1 week (wk) after injection, but was undetectable at 6 wk, which inversely correlated with the level of tyrophosphorylated c-ErbB-2 and the degree of cell proliferation indicated by PCNA staining.

CONCLUSIONS

Our results clearly demonstrated that cellular PAcP has a suppression effect on the growth of androgen-independent LNCaP xenograft tumors. This effect occurs at least partly through the dephosphorylation of c-ErbB-2 by PAcP, the prostate-specific protein tyrosine phosphatase. The data indicates that human PAcP could be utilized in the corrective gene therapy for a subgroup of androgen-independent human prostate cancer cells that lack cellular PAcP expression.

Nonviral genetic transfer of Fas ligand induced significant growth suppression and apoptotic tumor cell death in prostate cancer in vivo

To accomplish efficient nonviral gene therapy against prostate cancer (PC), Epstein-Barr virus (EBV)-based plasmid vectors containing EBNA1 gene and oriP were employed and combined with a cationic polymer or cationic lipid. When EBV-plasmid/poly-amidoamine dendrimer complex was injected into PC-3-derived tumors established in severe combined immunodeficiency mice, a considerable expression of marker gene was obtained in the tumors, and the expression level was more than eight-fold higher than that achieved by conventional plasmid vector/dendrimer. Since most PC cells express the apoptotic signal molecule Fas (Apo-1/CD95) on their surface, Fas ligand (FasL) gene was transferred into PC cells to kill the tumor cells. In vitro transfection with pGEG.FasL (an EBV-plasmid with the FasL gene) significantly reduced the viability of PC cells, which subsequently underwent apoptosis. Intratumoral injections of pGEG.FasL into PC induced significant growth suppression of the xenograft tumors, in which typical characteristics of apoptosis were demonstrated by TUNEL staining and electron microscopic observations. When pGEG.FasL transfer was accompanied by systemic administrations of cisplatin, the tumors were inhibited even more remarkably, leading to prolonged survival of the animals. FasL gene transfection by means of EBV-based plasmid/cationic macromolecule complexes may provide a practical therapeutic strategy against PC.

Prostate carcinoma: defining therapeutic objectives and improving overall outcomes

The development and progression of a prostate carcinoma from prediagnosis to death can be characterized as a series of clinical states. The states are milestones that can be used to assess prognosis, define therapeutic objectives, and assess outcomes. The antitumor effects of hormone therapies and cytotoxic agents in patients with prostate carcinoma are placed in context along with the bidrectional tumor-host interactions that contribute to the growth and resistance of osseous lesions. Identifying the factors that contribute to the growth of the disease at different points in the illness has lead to novel, systemic approaches. Proving the benefit of these approaches requires a series of unique trials with unique endpoints relevant to the clinical state of the patients and the specific therapy under evaluation.

Monoclonal antibody therapy for genitourinary oncology: promise for the future

PURPOSE

Metastatic or recurrent cancer continues to be the bane of the urological oncologist. Despite recent improvements in therapeutic strategies and outcomes for clinically localized disease overall survival in patients with the majority of metastatic and recurrent genitourinary malignancies remains relatively unchanged. Modern advances in the field of immunotherapy hold the promise of providing the clinical urologist/oncologist with new tools to fight urological cancer. In this review we discuss the various mAb based strategies currently under investigation for urological oncology as well as the lessons learned from similar approaches in other fields.

MATERIALS AND METHODS

We reviewed the literature on mAb based immunotherapy with a particular emphasis on target antigens, mAb design and potential applications in the field of urology.

RESULTS

Early trials with mAb therapy for solid tumor oncology met with limited success due to difficulty with mAb design and production, the development of host immunological responses against murine monoclonal antibodies (that is human anti-mouse antibodies), suboptimal target antigen selection, and poor monoclonal antibody pharmacokinetics and tumor tissue penetration. Recent advances in the fields of immunology and oncology have sought to circumvent these obstacles. Today several preliminary studies have shown the effectiveness and usefulness of mAb based strategies for urological oncology.

CONCLUSIONS

The field of mAb based immunotherapy continues to evolve. New discoveries in this burgeoning area of cancer therapy show promise for the future.

Nomogram for overall survival of patients with progressive metastatic prostate cancer after castration

PURPOSE

To develop a pretreatment prognostic model for survival of patients with progressive metastatic prostate cancer after castration using parameters that are measured during routine clinical management.

PATIENTS AND METHODS

Pretreatment clinical and biochemical determinants from 409 patients enrolled onto 19 consecutive therapeutic protocols from June 1989 through January 2000 were evaluated. The factors selected were age, Karnofsky performance status (KPS), hemoglobin (HGB), prostate-specific antigen (PSA), lactate dehydrogenase (LDH), alkaline phosphatase (ALK), and albumin. These factors were combined in an accelerated failure time regression model to produce a nomogram to predict median, 1-year, and 2-year survival. The nomogram was validated internally and externally using data from a multicenter randomized trial of suramin plus hydrocortisone versus hydrocortisone alone.

RESULTS

The median survival of the entire group was 15.8 months (range, 0.9 to 77.8 months); 87% have died. In multivariable analysis, KPS, HGB, ALK, albumin, and LDH were significantly associated with survival (P <.05), whereas age and PSA were not. All seven factors were included in the nomogram. When applied to the external validation data set, the nomogram achieved a concordance index of 0.67. Calibration plots suggested that the nomogram was well calibrated for all predictions.

CONCLUSION

A nomogram derived from pretreatment parameters that are measured on a routine basis was constructed. It can be used to predict the median, 1-year, and 2-year survival of patients with progressive castrate metastatic disease with reasonable accuracy. The information is useful to assess prognosis, guide treatment selection, and design clinical trials.

Apoptosis resistance of neuroendocrine phenotypes in prostatic adenocarcinoma

BACKGROUND

Neuroendocrine (NE) differentiation has been implicated in prostate cancer progression and hormone therapy failure. It has been shown that prostate cancer cells with NE features lack proliferation activity in vitro and in vivo. The current study reports on the apoptotic status of NE phenotypes in human prostate cancer.

METHODS

Double-label techniques were used for simultaneous demonstration of the endocrine marker chromogranin A (ChrA) and DNA fragmentation assessed by the terminal transferase-mediated biotinylated 16-desoxy-uridine-tri-phosphate (bio-16-dUTP) nick-end-labeling (TUNEL) assay. The material included primary prostatic adenocarcinoma (n = 18), lymph node metastases (n = 5), bone metastases (n = 2), and recurrent lesions (n = 10) showing NE differentiation at the immunohistochemical level.

RESULTS

Irrespective of grades, stages, and the degree of NE differentiation, DNA fragmentation was restricted to exocrine (ChrA-negative) tumor cells and was undetectable in most of NE tumor cells expressing ChrA. At least 0.16% of ChrA-positive tumor cells revealed DNA fragmentation assessed by the TUNEL assay.

CONCLUSION

The present data suggest that the vast majority of prostate cancer cells with NE features escapes programmed cell death. This escape may contribute significantly to their drug resistance and their malignant potential.

Role of prostate stem cell antigen in prostate cancer research

PURPOSE OF REVIEW

The identification of cell surface antigens is critical to the development of future prognostic and therapeutic modalities for the treatment of prostate cancer. Several prostate-specific proteins have been identified and are under investigation. This review reports on prostate stem cell antigen (PSCA), a protein with restricted expression that may have prognostic and therapeutic utility.

RECENT FINDINGS

PSCA is a glycosylphosphatidylinositol-anchored cell-surface protein belonging to the Ly-6/Thy-1 family of cell surface antigens, and a murine homologue has been described. It is expressed in the normal human prostate and overexpressed in human prostate cancers. Its overexpression has been correlated with increased Gleason score, advanced stage and bone metastasis. PSCA is co-amplified with MYC, an independent predictor of progression and death. PSCA may therefore be a useful predictor of tumor biology and a useful target of immunotherapy against prostate cancer. Evidence suggests a potential role in strategies employing cytotoxic T cell lymphocytes. Anti-tumor activity has been demonstrated with monoclonal antibodies in tumor take and established tumor xenograft models. Conjugated antibody has recently been reported to have anti-tumor activity in preclinical models.

SUMMARY

PSCA may serve as a tool in refining the prognosis of an individual cancer and may be a useful therapeutic target for immunotherapy. Future studies will be required to confirm its clinical utility as a prognostic factor. Future animal and clinical studies will be required to test various immunotherapy strategies for safety and efficacy. The study of PSCA regulation and expression may provide information on normal prostate development and prostate carcinogenesis.

Prostatic adenocarcinoma metastases mimicking small cell carcinoma on fine-needle aspiration

Prostate adenocarcinoma (PA) is known to metastasize widely to bone, lung, lymph nodes, and other sites. We have observed a rare, although distinctive, neuroendocrine (NE) cytomorphology of metastatic PA on fine-needle aspiration (FNA) that mimics small cell carcinoma (SCC). From a total of 117 cases, eight cases of metastatic PA diagnosed on FNA showed cytomorphologic features indistinguishable from SCC. All specimens were reviewed, along with immunoperoxidase (IPOX) studies using prostate specific (PSA, PSAP) and NE markers (synaptophysin, chromogranin, etc.). The patients ranged in age from 51-68 (mean age = 63). The PSA levels at the time of FNA ranged from <0.1 to 2,892 ng/ml (normal postprostatectomy <0.2 ng/ml). Sites of FNA included liver (two), soft tissue (five), and lymph node (one). FNA was performed from 11 mo to 6 yr after the initial diagnosis of the primary tumor. All primary PA were of high Gleason grade ranging from 7-9. None of the primary PA showed neuroendocrine morphology. Cytomorphologic characteristics observed on FNA included predominantly single cells with occasional sheets or loose cell aggregates. A predominant NE nuclear morphology was evident (i.e., hyperchromasia, fine dusty chromatin, inconspicuous nucleoli, nuclear molding, chromatinic crush artifact, karyorrhexis, mitoses, etc.), with none of the tumors displaying glandular formation. Taken together, these features gave these metastases a cytomorphology indistinguishable from SCC. IPOX studies revealed PSA-positivity (5/7), PSAP-positivity (4/7), and only focal NE markers positivity (3/6). Metastatic prostate carcinoma may rarely mimic a SCC (6.8% in this study). This often necessitates further patient workup to identify the primary source for the patient's metastasis, particularly if the patient has multiple lesions. An accurate diagnosis of these lesions as PA metastases is essential for effective, timely treatment and therapeutic design.

Vitamin D3 analogue inhibits keratinocyte growth factor signaling and induces apoptosis in human prostate cancer cells

BACKGROUND

Prostate cancer is a worldwide significant health care problem, due to its high incidence and mortality. In particular, androgen-independent tumors have the worst prognosis, because they are refractory to almost all kinds of available therapy. Hence, there is the need of new treatment opportunities targeting androgen-independent, growth factor-mediated, tumor signaling. One of these new promising opportunities is vitamin D3 and its related analogues.

METHODS

We investigated the effect of a vitamin D3 analogue, analogue (V), on proliferation of several human prostate cancer cells in basal condition and after treatment with KGF, one of the intraprostatic growth factors that might participate in the progression of prostate cancer. In addition, in the androgen-independent cell line DU 145, we also studied the effect of analogue (V), KGF, and their mutual interaction on protein tyrosine phosphorylation, bcl-2 expression and apoptosis.

RESULTS

Overall, we found that analogue (V) dose-dependently decreased basal and KGF-induced prostate cancer cell growth, although to a different extent. Maximal effect was obtained in DU 145 cells. In these cells, KGF stimulated tyrosine phosphorylation of a protein corresponding to its receptor, induced bcl-2 expression, and prolonged cell survival. Analogue (V) not only counteracted all these KGF-mediated events, but also decreased basal bcl-2 expression, therefore, allowing DU 145 cells to undergo an apoptotic program.

CONCLUSIONS

Our results indicated that in prostate cancer cells analogue (V) decreased basal and KGF-induced cell proliferation. This effect, at least in DU 145 cells, is in part mediated by negative interactions with cell survival and KGF signaling.

The development of androgen-independent prostate cancer

The normal prostate and early-stage prostate cancers depend on androgens for growth and survival, and androgen ablation therapy causes them to regress. Cancers that are not cured by surgery eventually become androgen independent, rendering anti-androgen therapy ineffective. But how does androgen independence arise? We predict that understanding the pathways that lead to the development of androgen-independent prostate cancer will pave the way to effective therapies for these, at present, untreatable cancers.

Autoantibodies to prostasomes as new markers for prostate cancer

Prostate cancer is one of the leading causes of cancer-related death among men. Given the varying clinical course and the long natural history of the disease, it is important to have good diagnostic and prognostic markers. Prostate specific antigen (PSA) is currently the best marker for the detection of prostate cancer, but in many cases it does not reveal whether metastases have appeared. Since metastases of prostate cancer release prostasomes, which are immunogenic secretory granules of both normal and neoplastic prostate cells, we checked whether anti-prostasome antibodies will appear when the cancer is metastasing. In a pilot study, all 13 patients with serum PSA between 50-500 microg/L had anti-prostasome antibodies, while 39 healthy controls with low PSA values showed background values. There was no overlapping, i.e. the upper range value of controls did not reach the lower range value of patients.