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At least 793 records · Page 44Linked to original sources
PubMed2000

Rational basis for Trk inhibition therapy for prostate cancer.

BACKGROUND: Prostatic cancer cells are lethal because they acquire the ability to activate survival pathways that do not require androgenic stimulation. As a rational approach to developing effective therapy for these devastating cells, specific signal transduction pathways uniquely required for the survival of these nonandrogen-dependent prostate cancer cells must be identified. Previous studies suggested that the neurotrophin/trk signal transduction axis may regulate such unique survival pathways. In the present study, the changes in expression of the neurotrophins (NGF, BDNF, and NT-3) and their cognate receptors (i.e., trk and p75NTR) during the progression of normal prostatic epithelial cells to malignancy were documented. Additionally, the consequences of inhibiting these trk signaling pathways on the in vitro survival of prostate cancer cells was tested. METHODS: Immmunocytochemistry, RT-PCR, and ELISA assays were used to characterize the changes in the neurotrophin ligands (i.e., NGF, BDNF, and NT-3) and their cognate high-affinity (i.e., trk A, B, and C) and low-affinity neurotrophin (i.e., p75 NTR) receptors in normal vs. malignant human prostatic tissues. CEP-751 is an indolocarbazole compound specifically designed to inhibit the initiation of these neurotrophin/trk signal transductions. The consequence of CEP-751 inhibition of trk signaling for in vitro clonogenic survival of a series of human prostatic cancer lines was also tested. RESULTS: These studies demonstrated that normal prostatic tissue from patients without prostate cancer contains substantial levels of nerve growth factor (NGF), which is produced in a paracrine manner by stromal cells. These stromal cells lack both trk and p75NTR receptors. In contrast, normal prostatic epithelial cells from patients without prostate cancer do not secrete detectable levels of neurotrophins, but do express trk A and p75 NTR. While the NGF/trkA/p75 NTR axis is present in the normal prostate, normal prostatic epithelial cells do not depend on this axis for their survival. In contrast, malignant prostate epithelial cells directly secrete a series of neurotrophins (i.e., NGF, BDNF, and/or NT-3) and express at least one if not more of the trk receptor proteins (i.e., trk A, B, and/or C), while no longer expressing the p75NTR receptors. In addition, inhibition of autocrine trk signaling via CEP-751 treatment induces the apoptotic death of these malignant cells. CONCLUSIONS: Prostate carcinogenesis involves molecular changes leading to the paracrine and/or autocrine production of a series of neurotrophins. This is coupled to the ectopic expression of trk B and trk C, as well as to the continued expression of trk A, and the loss of expression of p75NTR receptors. These changes result in the acquisition by malignant prostate cells of a unique requirement for trk signaling pathways for survival. Based on these findings, trk inhibition is a novel, rational approach for prostate cancer therapy.

Animals↗
PubMed2002

Osteoblasts produce soluble factors that induce a gene expression pattern in non-metastatic prostate cancer cells, similar to that found in bone metastatic prostate cancer cells.

BACKGROUND: Progressive prostate cancer typically metastasizes to bone where prostate cancer cells gain an osteoblast-like phenotype and induce osteoblastic metastases through unknown mechanisms. To investigate the biology of prostate cancer skeletal metastases, we compared gene expression between the non-metastatic LNCaP cell line and its derivative cell line C4-2B that metastasizes to bone. METHODS: Total RNA from LNCaP and C4-2B cell lines was isolated and used to probe membrane-based gene arrays (Comparison 1). Additionally, LNCaP cells were incubated in the absence or presence of conditioned media (CM) from a human osteoblast-like cell line (HOBIT) and total RNA from these cells was used to probe gene arrays (Comparison 2). Differential expression of genes was confirmed by RT-PCR. RESULTS: Of the 1,176 genes screened, 35 were differentially expressed between LNCaP and C4-2B cells (Comparison 1). HOBIT-CM induced differential expression of 30 genes in LNCaP cells (Comparison 2). Interestingly, 19 genes that were differentially expressed in C4-2B vs. LNCaP also displayed a similar expression pattern in LNCaPs grown in HOBIT-CM. These genes are primarily involved in motility, metabolism, signal transduction, tumorigenesis, and apoptosis. CONCLUSIONS: These results suggest that osteoblasts produce soluble factors that contribute to the progression of prostate cancer skeletal metastases, including their transition to an osteoblast-like phenotype. Additionally, these data provide targets to explore for further investigations towards defining the biology of skeletal metastases.

Bone Neoplasms↗
PubMed2001

Interleukin-6 and prostate cancer progression.

Prostate cancer, while initially dependent on androgens for proliferation, progresses to an androgen-independent state. Evidence has been accumulating that interleukin-6 (IL-6) may contribute to prostate cancer progression. Serum levels of IL-6 correlate with prostate tumor burden and patient morbidity. The prostate tissue itself appears to be a source of IL-6 and its receptor. Furthermore, experimental data suggest that IL-6 is an autocrine and paracrine growth factor for androgen-independent prostate cancer cell lines. For example, inhibition of IL-6, with anti-IL-6 antibody, sensitizes androgen-independent prostate cancer cells to chemotherapeutic agents in vitro. Finally, IL-6 activates a variety of signal transduction cascades, some which stimulate androgen receptor activity, in prostate cancer cells. These data suggest that targeting IL-6 may have multiple benefits in prostate cancer patients.

Animals↗
PubMed2003

Prostate cancer cell-adipocyte interaction: leptin mediates androgen-independent prostate cancer cell proliferation through c-Jun NH2-terminal kinase.

Prostate cancer is one of the leading causes of death among men in the United States, and acquisition of hormone resistance (androgen independence) by cancer cells is a fatal event during the natural history of prostate cancer. Obesity is another serious health problem and has been shown to be associated with prostate cancer. However, little is known about the molecular basis of this association. Here we show that factor(s) secreted from adipocytes stimulate prostate cancer cell proliferation. Leptin is one of the major adipose cytokines, and it controls body weight homeostasis through food intake and energy expenditure. We identify leptin as a novel growth factor in androgen-independent prostate cancer cell growth. Strikingly, leptin stimulates cell proliferation specifically in androgen-independent DU145 and PC-3 prostate cancer cells but not in androgen-dependent LNCaP-FGC cells, although both cell types express functional leptin receptor isoforms. c-Jun NH2-terminal kinase (JNK) has been shown recently to play a crucial role in obesity and insulin resistance. Intriguingly, leptin induces JNK activation in androgen-independent prostate cancer cells, and the pharmacological inhibition of JNK blocked the leptin stimulation of androgen-independent prostate cancer cell proliferation. This suggests that JNK activation is required for leptin-mediated, androgen-independent prostate cancer cell proliferation. Furthermore, other cytokines produced by adipocytes and critical for body weight homeostasis cooperate with leptin in androgen-independent prostate cancer cell proliferation: interleukin-6 and insulin-like growth factor I demonstrate additive and synergistic effects on the leptin stimulation of androgen-independent prostate cancer cell proliferation, respectively. Therefore, adipose cytokines, as well as JNK, are key mediators between obesity and hormone-resistant prostate cancer and could be therapeutic targets.

Adipocytes↗
PubMed1988

Prediction of time to progression after orchiectomy by the nuclear androgen receptor content from multiple biopsy specimens in patients with advanced prostate cancer.

The nuclear androgen receptor (ARn) content of cancerous prostatic tissue has been investigated as a prognosticator for time to progression under endocrine therapy. In 1981 a prospective study was started to investigate whether the ARn content in biopsy specimens of patients with prostatic carcinoma predicts the duration of response following hormonal treatment. ARn was estimated by a microassay which involves extraction of nuclear pellets with a heparin-containing buffer, exchange labeling of the nuclear extract with 3H-R1881, and quantitation of the receptor with protamine sulphate precipitation. One hundred and fifteen patients with prostatic cancer entered this study; 47 patients had evidence of metastatic disease as proven by bone scan. Forty-two patients were treated by orchiectomy; 37 of these patients are evaluable with a minimal follow-up of 30 months. A relationship between the nuclear androgen receptor content and the time to progression following orchiectomy in these patients with metastatic disease of the prostate was not found. This could possibly be attributed to the heterogeneous nature of the prostatic tumor tissue with respect to the distribution of the ARn. We conclude that androgen receptor assay in needle biopsies, at least in this study, had no value for the prediction of the time to progression after orchiectomy.

Aged↗
PubMed1999

Prospects and limitations of recombinant poxviruses for prostate cancer immunotherapy.

Prostate cancer is a disease that may be amenable to immunotherapy approaches, as evidenced by the ability to induce human cytotoxic immune responses against prostate cancer cells. Recent interest in recombinant poxvirus vaccines coupled with the need for new prostate cancer therapies has led to the development of several recombinant poxvirus agents designed for prostate cancer treatment. Whether these agents will be effective in treating prostate cancer is under investigation in several ongoing and upcoming clinical trials. In the meantime, data from preclinical tumor models have provided information that may aid in improving recombinant poxviruses for clinical use. While animal studies have shown the ability of recombinant poxvirus vaccination to induce an immune response that protects against lethal tumor, these antitumor effects are variable and depend on a number of factors. Co-expression of immunomodulating gene products, such as cytokines and costimulatory molecules, have been shown to influence antitumor immunity; in fact, cytokine delivery alone can be enough to protect against tumor-related death. Patterns and levels of recombinant antigen expression also affect the immune response to that antigen, as seen by studies of various poxvirus promoters and cell compartment-targeting sequences. In addition, vaccine strategies targeting self-antigens have shown that immunological tolerance can negatively impact the induction of antitumor and antigen-specific immunity. Although vaccinia virus has been most intensely studied thus far, other poxviruses, including fowlpox and canarypox, are also promising vaccine candidates. These alternative vectors may circumvent some of the disadvantages associated with vaccinia virus, such as pre-existing vaccinia immunity. A deeper understanding of these factors and others that impact the development of antitumor immunity will be necessary to guide the development of recombinant poxviruses for prostate cancer therapy.

Adenocarcinoma↗
PubMedDate not supplied

Different phenotypes in human prostate cancer: alpha6 or alpha3 integrin in cell-extracellular adhesion sites.

The distribution of alpha6/alpha3 integrin in adhesion complexes at the basal membrane in human normal and cancer prostate glands was analyzed in 135 biopsies from 61 patients. The levels of the polarized alpha6/alpha3 integrin expression at the basal membrane of prostate tumor glands were determined by quantitative immunohistochemistry. The alpha6/alpha3 integrin expression was compared with Gleason sum score, pathological stage, and preoperative serum prostate-specific antigen (PSA). The associations were assessed by statistical methods. Eighty percent of the tumors expressed the alpha6 or alpha3 integrin and 20% was integrin-negative. Gleason sum score, but not serum PSA, was associated with the integrin expression. Low Gleason sum score correlated with increased integrin expression, high Gleason sum score with low and negative integrin expression. Three prostate tumor phenotypes were distinguished based on differential integrin expression. Type I coexpressed both alpha6 and alpha3 subunits, type II exclusively expressed alpha6 integrin, and type III expressed alpha3 integrin only. Fifteen cases were further examined for the codistribution of vinculin, paxillin, and CD 151 on frozen serial sections using confocal laser scanning microscopy. The alpha6/alpha3 integrins, CD151, paxillin, and vinculin were present within normal glands. In prostate carcinoma, alpha6 integrin was colocalized with CD 151, but not with vinculin or paxillin. In tumor phenotype I, the alpha6 subunit did not colocalize with the alpha subunit indicating the existence of two different adhesion complexes. Human prostate tumors display on their cell surface the alpha6beta1 and/or alpha3beta1 integrins. Three tumor phenotypes associated with two different adhesion complexes were identified, suggesting a reorganization of cell adhesion structures in prostate cancer.

Alleles↗
PubMed2000

Screening for early prostate cancer: what is the problem?

Screening has been applied to normal populations to detect early cancers. Prostate cancer is very common and can be detected at an early stage. Screening has not been introduced in the UK for this disease and the possible reasons for this are discussed. There is a strong case for evaluation of screening programmes for this disease.

Humans↗
PubMed1999

Genistein inhibits NF-kappa B activation in prostate cancer cells.

Prostate cancer is the second leading cause of cancer-related deaths in men in the United States. Epidemiological studies indicate that susceptibility to prostate cancer may be partly due to environmental influences, especially diet. An association has been shown between decreased prostate cancer risk and mortality with increased consumption of soy products, resulting in increased levels of isoflavones. We previously demonstrated that the soy isoflavone genistein inhibits cell growth and induces apoptosis in prostate cancer cells. To further elucidate the molecular mechanism by which genistein elicits its apoptotic effect, we investigated the role of a transcription factor, nuclear factor-kappa B (NF-kappa B), in the androgen-sensitive cell line LNCaP and the androgen-insensitive cell line PC3. Here we show that genistein decreases NF-kappa B DNA binding and abrogates NF-kappa B activation by DNA-damaging agents, H2O2 and tumor necrosis factor-alpha, in prostate cancer cells regardless of androgen sensitivity. Additionally, we have demonstrated that genistein reduces phosphorylation of the inhibitory protein I kappa B alpha and blocks the nuclear translocation of NF-kappa B, prohibiting DNA binding and preventing NF-kappa B activation. These results provide a mechanism by which genistein induces apoptosis in prostate cancer cells: the inactivation of NF-kappa B. Furthermore, genistein's ability to abrogate NF-kappa B activation by DNA-damaging agents strongly supports genistein's role as a chemopreventive agent.

Anticarcinogenic Agents↗
PubMed2006

Sex-determining region Y box 4 is a transforming oncogene in human prostate cancer cells.

Prostate cancer is the most commonly diagnosed noncutaneous neoplasm and second most common cause of cancer-related mortality in western men. To investigate the mechanisms of prostate cancer development and progression, we did expression profiling of human prostate cancer and benign tissues. We show that the SOX4 is overexpressed in prostate tumor samples compared with benign tissues by microarray analysis, real-time PCR, and immunohistochemistry. We also show that SOX4 expression is highly correlated with Gleason score at the mRNA and protein level using tissue microarrays. Genes affected by SOX4 expression were also identified, including BCL10, CSF1, and NcoA4/ARA70. TLE-1 and BBC3/PUMA were identified as direct targets of SOX4. Silencing of SOX4 by small interfering RNA transfection induced apoptosis of prostate cancer cells, suggesting that SOX4 could be a therapeutic target for prostate cancer. Stable transfection of SOX4 into nontransformed prostate cells enabled colony formation in soft agar, suggesting that, in the proper cellular context, SOX4 can be a transforming oncogene.

Apoptosis↗
PubMed2005

Active surveillance for prostate cancer: for whom?

Prostate-specific antigen (PSA) -based prostate cancer screening results in the diagnosis of prostate cancer in many men who are not destined to have clinical progression during their lifetime. Good-risk prostate cancer, defined as a Gleason score of 6 or less, PSA < 10, and T1c to T2a, now constitutes 50% of newly diagnosed prostate cancer. In most of these patients, the disease is indolent and slow growing. The challenge is to identify those patients who are unlikely to experience significant progression while offering radical therapy to those who are at risk. The approach to favorable-risk prostate cancer described in this article uses estimation of PSA doubling time (PSA DT) to stratify patients according to the risk of progression. Patients who select this approach are managed initially with active surveillance. Those who have a PSA DT of 3 years or less (based on a minimum of three determinations over 6 months) are offered radical intervention. The remainder are closely monitored with serial PSA and periodic prostate rebiopsies (at 2, 5, and 10 years). In this series of 299 patients, the median DT was 7 years. Forty-two percent had a PSA DT > 10 years, and 20% had a PSA DT > 100 years. The majority of patients on this study remain under surveillance. The approach of active surveillance with selective delayed intervention based on PSA DT represents a practical compromise between radical therapy for all (which results in overtreatment for patients with indolent disease) and watchful waiting with palliative therapy only (which results in undertreatment for those with aggressive disease).

Biomarkers, Tumor↗
PubMed2000

Early results of LH-RH agonist treatment with or without chlormadinone acetate for hormone therapy of naive localized or locally advanced prostate cancer: a prospective and randomized study. The Prostate Cancer Study Group.

BACKGROUND: The majority of patients with localized and some cases of locally advanced prostate cancer undergo radical prostatectomy. However, radical prostatectomy cannot always be selected for those patients. In this situation, primary hormone therapy is an alternative treatment option. We have designed a prospective randomized study of the effects of primary hormone therapy for such patients. METHODS: A total of 151 patients with T1b, T1c, T2a, T2b or T3a prostate cancer who were not scheduled for radical prostatectomy were enrolled into this study. Patients were randomly allocated into two groups; Group I received luteinizing hormone-releasing hormone (LH-RH) agonist monotherapy (leuprorelin acetate depot, 3.75 mg monthly) and Group II received LH-RH agonist in combination with chlormadinone acetate (100 mg/day). Effects on serum prostate-specific antigen level, progression-free survival and survival were observed for 2 years. RESULTS: The reasons why radical prostatectomy was not scheduled were poor risk for surgery (38%), patient's wish (32%) and physician's recommendation (30%). After 12 weeks of treatment, 49% of the patients in both groups showed a complete response (CR). Of the patients showing a partial response (PR) after 12 weeks of treatment, 25% in Group I and 52% in Group II improved to CR 1 year later (p<0.05). Group II showed a longer progression-free survival (p <0.05). Progression-free survival rates were 62% (Group I) and 91% (Group II) in T2b patients and 43% (Group I) and 73% (Group II) in T3 patients. Only one patient in each group died from prostate cancer. CONCLUSIONS: Early primary hormone therapy is a reasonable treatment option for localized or locally advanced prostate cancer patients if radical prostatectomy was not scheduled. Chlormadinone acetate showed an additive effect with LH-RH agonist, at least in 2 years' observation.

Aged↗
PubMed2005

[The study landscape for prostate cancer].

Current prostate cancer studies in Germany encompass the indications "adjuvant therapy", "rising PSA following radical prostatectomy", "metastasized, hormone sensitive prostate cancer", and "hormone refractory prostate cancer". In the adjuvant field, the potential of zoledronic acid for the prevention of bone metastases is being investigated in a large phase III trial. The activity of imatinib in low volume prostate cancer is being tested in patients with rising PSA following radical prostatectomy (phase II). The randomized phase III trial intermittent versus continuous hormone therapy in D1 and D2 patients has finished accrual and follow-up will be extended until the end of 2006. In hormone refractory prostate cancer(HRPC), the results of a recent phase II study (Association of Urological Oncology; AOU AP 33/02) were promising. This led to a currently activate phase III trial comparing intermittent with continuous chemotherapy in HRPC. The interdisciplinary study group of the AUO (Urology) and the ARO (Radio-oncology) has developed several new protocols which are currently under review by the German Cancer Aid (Deutsche Krebshilfe).

Antineoplastic Agents↗
PubMed2000

Identification of two distinct regions of allelic imbalance on chromosome 18Q in metastatic prostate cancer.

Like most cancers, prostate cancer (CaP) is believed to be the result of the accumulation of genetic alterations within cells. Previous studies have implicated numerous chromosomal regions with elevated rates of allelic imbalance (AI), using mostly primary CaPs with an unknown disease outcome. These regions of AI are proposed sites for tumor suppressor genes. One of the regions previously implicated as coding for at least one tumor suppressor gene is the long arm of chromosome 18 (18q). To confirm this observation, as well as to narrow the critical region for this putative tumor suppressor, we analyzed 32 metastatic CaP specimens for AI on chromosome 18q. Thirty-one of these 32 specimens (96.8%) exhibited AI at one or more loci on chromosome 18q. Our analysis using 17 polymorphic markers revealed statistically significant AI on chromosome 18q at 3 markers, D18S35, D18S64 and D18S461. Using these markers as a guide, we have been able to identify 2 distinct minimum regions of AI on 18q. The first region is between the genetic markers D18S1119 and D18S64. The second region lies more distal on the long arm of the chromosome and is between the genetic markers D18S848 and D18S58. To determine if 18q loss is a late event in the progression of CaP, we also examined prostatic intraepithelial neoplasia (PIN) and primary prostate tumors from 17 patients for AI with a subset of 18q markers. We found significantly higher AI in the metastatic samples. Our results are consistent with 18q losses occurring late in CaP progression.

Carcinoma in Situ↗
PubMed2004

Defective DNA strand break repair after DNA damage in prostate cancer cells: implications for genetic instability and prostate cancer progression.

Together with cell cycle checkpoint control, DNA repair plays a pivotal role in protecting the genome from endogenous and exogenous DNA damage. Although increased genetic instability has been associated with prostate cancer progression, the relative role of DNA double-strand break repair in malignant versus normal prostate epithelial cells is not known. In this study, we determined the RNA and protein expression of a series of DNA double-strand break repair genes in both normal (PrEC-epithelial and PrSC-stromal) and malignant (LNCaP, DU-145, and PC-3) prostate cultures. Expression of genes downstream of ATM after ionizing radiation-induced DNA damage reflected the p53 status of the cell lines. In the malignant prostate cell lines, mRNA and protein levels of the Rad51, Xrcc3, Rad52, and Rad54 genes involved in homologous recombination were elevated approximately 2- to 5-fold in comparison to normal PrEC cells. The XRCC1, DNA polymerase-beta and -delta proteins were also elevated. There were no consistent differences in gene expression relating to the nonhomologous end-joining pathway. Despite increased expression of DNA repair genes, malignant prostate cancer cells had defective repair of DNA breaks, alkali-labile sites, and oxidative base damage. Furthermore, after ionizing radiation and mitomycin C treatment, chromosomal aberration assays confirmed that malignant prostate cells had defective DNA repair. This discordance between expression and function of DNA repair genes in malignant prostate cancer cells supports the hypothesis that prostate tumor progression may reflect aberrant DNA repair. Our findings support the development of novel treatment strategies designed to reinstate normal DNA repair in prostate cancer cells.

Animals↗