Regulation of migration of primary prostate epithelial cells by secreted factors from prostate stromal cells

Stromal-epithelial interactions, which regulate the migration of prostate epithelial cells, play an important role in prostate development, prostatic hyperplasia, and prostate cancer. The objective of this study was to determine how the prostate stroma stimulates the migration of primary prostate epithelial cells (PECs). In the Boyden chamber assay, PEC migration was strongly induced by the conditioned medium of primary prostate stromal cells (PSC-CM). Stimulation of PEC migration depended on the concerted action of adhesion and motility factors in the PSC-CM. Immobilized proteins from PSC-CM mediated adhesion, spreading, and head-to-tail polarization of PECs. Migration induced by immobilized PSC-CM proteins was significantly increased by hepatocyte growth factor/scatter factor (HGF/SF). Inhibition of P13-kinase or Src-family kinases, but not MEK or PLCchi, abolished migration in the Boyden chamber assay. Consistent with their concerted activity in migration assays, the combination of adhesion and motility factors was required for efficient activation of the P13-kinase/Akt pathway. HGF/SF in the PSC-CM was the principal stimulator of the P13-kinase/Akt pathway and an important mediator of PSC-CM-induced PEC migration. In conclusion, our data show that the migration of primary PECs is regulated by the P13-kinase and Src-family kinase signaling pathways and that the activation of the P13-kinase pathway requires adhesion and motility factors from the prostate stroma.     

The use of PSA as biomarker in nutritional intervention studies of prostate cancer

Epidemiological evidence suggests that environmental factors, such as diet, play a role in the development and progression of prostate cancer (PC). The number of potential protective dietary compounds or whole dietary products that are indicated to have preventive effects is piling up and demands further evaluation. The number of options urges for a reliable high-throughput screening system. To face this growing field, we suggest a strategy that combines prostate-specific antigen (PSA)-based clinical trials with experimental human xenograft studies to evaluate potential chemopreventive agents for PC. This review describes the first results that have come available using this method. In Rotterdam, two nutrition-based tertiary chemoprevention trials were conducted in patients aiming to delay progression of minimal PC. In these studies two different supplements were used both consisting of a (different) mixture of components reported to be related to cancer prevention. PC patients that were locally treated but had rising levels of circulating PSA of unknown origin were randomised into a double-blind, placebo-controlled study with a crossover design. PSA kinetics was followed during the two intervention periods. The time frame of the study design was 6 months. Results of these intervention studies showed increased PSA doubling times after dietary supplementation as compared to placebo. The lack of information on tumor burden in these patients requires the need for additional xenograft studies that can provide supplement-induced PSA and tumor responses. Such parallel experimental studies will enable to validate PSA as a biomarker for tumor volume response and may link clinical PSA kinetics to actual tumor response. For one of the clinical study, such an experimental confirmation study was performed. The dietary supplement similar to what was used in the clinical study was administered to animals that were injected intraprostatically with human PC-346C cells. Responses on tumor growth and PSA were recorded over time and allowed to monitor a potential differential effect on PSA or tumor growth. This animal study revealed no difference in response as determined by tumor volume or PSA release between supplemented and placebo mice, and confirmed that PSA levels reflected tumor response under this specific dietary intervention. We propose that the strategy of PSA-based early phase II clinical trials accompanied by experimental human xenograft studies, to assess the reliability of PSA response to reflect tumor response, allows for a concise, relatively fast test system that is able to screen the various treatment options for chemoprevention in a relatively short period of time.     

The impact of PSA and digital rectal examination on the risk of prostate cancer specific mortality in men with a PSA level <2.5 ng/ml

IntroductionIt is unknown whether a normal range, diagnostic serum prostate specific antigen (PSA) level's influence on prostate cancer specific mortality (PCSM) is dependent upon digital rectal examination (DRE) findings.MethodsBetween 2004 and 2007, 9081 men diagnosed with non-palpable (T1c, N = 1710) or palpable (T2–T4, N = 7371) and non-metastatic prostate cancer (PC) were identified from surveillance, epidemiology, and end results data, selected based on pre-treatment PSA < 2.5 ng/ml. A multivariable competing risks regression model evaluated whether DRE findings interacted with PSA level in predicting risk of PCSM.ResultsAfter median follow-up of 2.83 years, 118 of 548 deaths (21.5%) were due to PC. Increasing diagnostic PSA was associated with increased risk of PCSM (AHR = 3.52; 95% CI: 1.25–9.89; P = .017) in men with T1c, Gleason score 7–10 PC, but decreased PCSM risk (AHR = 0.66; 95% CI: 0.52–0.83; P < .001) for men with T2–T4 PC and any Gleason score.DiscussionFor men with diagnostic PSA level <2.5 ng/ml and palpable PC, risk of early PCSM increases by 34% for a 1 point decrease in PSA from 2. This suggests the existence of clinically detectable, low PSA secreting disease with an elevated risk of early PCSM, highlighting the importance of the DRE in men with PC and normal range, diagnostic PSA.     

Results of combined radiotherapy and hormonal treatment of prostate cancer patients with initial PSA value >40 ng/ml

AimTo evaluate the outcome of prostate cancer patients with initial PSA value >40 ng/ml.BackgroundThe outcome of prostate cancer patients with very high initial PSA value is not known and patients are frequently treated with palliative intent. We analyzed the outcome of radical combined hormonal treatment and radiotherapy in prostate cancer patients with initial PSA value >40 ng/ml.MethodsBetween January 2003 and December 2007 we treated, with curative intent, 56 patients with non-metastatic prostate cancer and initial PSA value >40 ng/ml. The treatment consisted of two months of neoadjuvant hormonal treatment (LHRH analog), radical radiotherapy (68–78 Gy, conformal technique) and an optional two-year adjuvant hormonal treatment.ResultsThe median time of follow up was 61 months. 5-Year overall survival was 90%. 5-Year biochemical disease free survival was 62%. T stage, Gleason score, PSA value, and radiotherapy dose did not significantly influence the outcome. Late genitourinal and gastrointestinal toxicity was acceptable.ConclusionRadical treatment in combination with hormonal treatment and radiotherapy can be recommended for this subgroup of prostate cancer patients with good performance status and life expectancy.     

Adipose-derived stromal cells inhibit prostate cancer cell proliferation inducing apoptosis

Mesenchymal stem cells (MSCs) have generated a great deal of interest in the field of regenerative medicine. Adipose-derived stromal cells (AdSCs) are known to exhibit extensive proliferation potential and can undergo multilineage differentiation, sharing similar characteristics to bone marrow-derived MSCs. However, as the effect of AdSCs on tumor growth has not been studied sufficiently, we assessed the degree to which AdSCs affect the proliferation of prostate cancer (PCa) cell. Human AdSCs exerted an inhibitory effect on the proliferation of androgen-responsive (LNCaP) and androgen-nonresponsive (PC3) human PCa cells, while normal human dermal fibroblasts (NHDFs) did not, and in fact promoted PCa cell proliferation to a degree. Moreover, AdSCs induced apoptosis of LNCaP cells and PC3 cells, activating the caspase3/7 signaling pathway. cDNA microarray analysis suggested that AdSC-induced apoptosis in both LNCaP and PC3 cells was related to the TGF-β signaling pathway. Consistent with our in vitro observations, local transplantation of AdSCs delayed the growth of tumors derived from both LNCaP- and PC3-xenografts in immunodeficient mice. This is the first preclinical study to have directly demonstrated that AdSC-induced PCa cell apoptosis may occur via the TGF-β signaling pathway, irrespective of androgen-responsiveness. Since autologous AdSCs can be easily isolated from adipose tissue without any ethical concerns, we suggest that therapy with these cells could be a novel approach for patients with PCa.     

Increased infiltrated macrophages in benign prostatic hyperplasia (BPH): role of stromal androgen receptor in macrophage-induced prostate stromal cell proliferation

Infiltrated macrophages may play important roles in the development and progression of benign prostatic hyperplasia (BPH), but the underlying mechanisms remain largely unknown. We found increased macrophages infiltration in human and mouse BPH tissues. By establishing a co-culture transwell system, we found increased migration of macrophages and proliferation of prostate stromal cells during co-culture. Importantly, stromal androgen receptor (AR) could enhance the migration of macrophages and macrophage-mediated stromal cell proliferation. We identified CCL3 as an AR downstream player, and found CCL3 levels were notably increased in human and mouse BPH prostates. Ablation of prostate stromal AR in a mouse BPH model significantly reduced CCL3 expression levels in prostates. Consistently, targeting AR via an AR degradation enhancer, ASC-J9§, or neutralization of CCL3 with an antibody, resulted in suppression of macrophage migration and prostate stromal cell growth. Our study provides mechanistic insights on the regulation of prostate stromal cells by macrophages via stromal AR/CCL3 signaling pathways, which could potentially allow the development of therapeutic approaches for battling BPH with persistent inflammation.     

Survival and clinical metastases among prostate cancer patients treated with androgen deprivation therapy in Sweden

ObjectivesTo examine the incidence of metastases and clinical course of prostate cancer patients who are without confirmed metastasis when initiating androgen deprivation therapy (ADT).MethodsRetrospective cohort study conducted using electronic medical records from Swedish outpatient urology clinics linked to national mandatory registries to capture medical and demographic data. Prostate cancer patients initiating ADT between 2000 and 2010 were followed from initiation of ADT to metastasis, death, and/or end of follow-up.ResultsThe 5-year cumulative incidence (CI) of metastasis was 18%. Survival was 60% after 5 years; results were similar for bone metastasis-free survival. The 5-year CI of castration-resistant prostate cancer (CRPC) was 50% and the median survival from CRPC development was 2.7 years. Serum prostate-specific antigen (PSA) levels and PSA doubling time were strong predictors of bone metastasis, any metastasis, and death.ConclusionThis study provides understanding of the clinical course of prostate cancer patients without confirmed metastasis treated with ADT in Sweden. Greater PSA values and shorter PSA doubling time (particularly ≤ 6 months) were associated with increased risk of bone metastasis, any metastasis, and death.     

EGFR signaling pathway negatively regulates PSA expression and secretion via the PI3K-Akt pathway in LNCaP prostate cancer cells

Epidermal growth factor (EGF) and its receptor (EGFR) are involved in hormone-refractory growth and poor prognosis of a subgroup of human prostate cancer. In this communication, we investigated the regulation of PSA by the EGFR signaling pathway using LNCaP C-81 prostate cancer cells. Administration of EGF stimulated the growth of LNCaP C-81 cells, however, PSA expression and secretion were suppressed. An EGFR inhibitor, AG1478, abrogated the PSA suppression effect by EGF, in concurrence with the suppression of tyro-phosphorylation levels of EGFR. Interestingly, the AR level was also decreased in EGF-treated LNCaP C-81 cells. Moreover, LY294002, but not PD98059, inhibited the PSA and AR suppression effect by EGF in concurrence with the suppression of phosphorylation levels of Akt. In conclusion, our results strongly suggest the existence of a novel androgen-independent PSA regulatory mechanism, i.e., the EGFR signaling pathway negatively regulates PSA expression which may be induced by the alteration of AR expression via the PI3K-Akt pathway in LNCaP C-81 cells.     

Trends in Prostate Specific Antigen (PSA) testing and prostate cancer incidence and mortality in Australia: A critical analysis

BackgroundPopulation trends in PSA testing and prostate cancer incidence do not perfectly correspond. We aimed to better understand relationships between trends in PSA testing, prostate cancer incidence and mortality in Australia and factors that influence them.MethodsWe calculated and described standardised time trends in PSA tests, prostate biopsies, treatment of benign prostatic hypertrophy (BPH) and prostate cancer incidence and mortality in Australia in men aged 45–74, 75–84, and 85 + years.ResultsPSA testing increased from its introduction in 1989 to a peak in 2008 before declining in men aged 45–84 years. Prostate biopsies and cancer incidence fell from 1995 to 2000 in parallel with decrease in trans-urethral resections of the prostate (TURP) and, latterly, changes in pharmaceutical management of BPH. After 2000, changes in biopsies and incidence paralleled changes in PSA screening in men 45–84 years, while in men ≥85 years biopsy rates stabilised, and incidence fell. Prostate cancer mortality in men aged 45–74 years remained low throughout. Mortality in men 75–84 years gradually increased until mid 1990s, then gradually decreased. Mortality in men ≥ 85 years increased until mid 1990s, then stabilised.ConclusionAge specific prostate cancer incidence largely mirrors PSA testing rates. Most deviation from this pattern may be explained by less use of TURP in management of BPH and consequent less incidental cancer detection in TURP tissue specimens. Mortality from prostate cancer initially rose and then fell below what it was when PSA testing began. Its initial rise and fall may be explained by a possible initial tendency to over-attribute deaths of uncertain cause in older men with a diagnosis of prostate cancer to prostate cancer. Decreases in mortality rates were many fold smaller than the increases in incidence, suggesting substantial overdiagnosis of prostate cancer after introduction of PSA testing.     

Secretion of endogenous kallikreins 2 and 3 by androgen receptor-transfected PC-3 prostate cancer cells

Androgen independent PC-3 cells lack androgen receptor (AR) expression and do not produce kallikrein 2 (hK2) or 3 (prostate-specific antigen, PSA). In this paper, we examined the ability of androgens to stimulate PSA and hK2 production in AR transfected PC-3 cells (PC-3(AR)) and compared this to LNCaP cells. PSA and hK2 were measured in the culture medium and cell lysates using an ELISA-based immunofluorometric assay. Only androgens were able to induce PSA and hK2 secretion in PC-3(AR) cells in a dose- and time-dependent manner depending on the level of AR present. The level of androgen-induced PSA and hK2 secretion in PC-3(AR) cells was approximately 1.5 and 0.9% that induced in LNCaP cells, respectively. Insulin-like growth factor-I (IGF-I), which has been shown to activate AR in the absence of ligand, did not activate PSA secretion in the absence of androgen, but further increased the dihydrotestosterone-induced PSA secretion in PC-3(AR) cells. The lack of PSA and hK2 production in parental PC-3 cells is thus a result of their lack of AR expression. PSA and/or hK2 production in PC-3(AR) cells can thus serve as an endogenous reporter system to investigate AR action or to screen putative endocrine disrupters.     

Interleukin 6 mediates the lysophosphatidic acid-regulated cross-talk between stromal and epithelial prostate cancer cells

The interaction between stromal and epithelial cells is critical for the initiation and progression of prostate cancer, but the molecular determinants responsible for the cross-talk between these two cell types remain largely unknown. Here, we used a co-culture cell assay to identify messengers involved in the cross-talk between human prostate stromal PS30 and epithelial LNCaP cells. Stimulation with lysophosphatidic acid (LPA) activates the mitogenic ERK signaling pathway in PS30, but not LNCaP, cells. The co-culture of PS30 and LNCaP cells results in the activation of ERK in LNCaP cells and that is further increased in response to stimulation with LPA. Physiologic relevance of the interaction between PS30 and LNCaP cells is demonstrated using LNCaP xenograft tumor assays. Animals implanted with a mixture of both cell types develop larger tumors with higher frequency compared with those injected with LNCaP cells alone. Conditioned medium transfer experiments reveal the PS30-derived inducing factor is soluble and promotes mitogenic ERK and STAT3 signaling pathways in LNCaP cells. Protein analysis demonstrates that treatment of the PS30 cells with LPA induces synthesis of interleukin 6 (IL-6). Antibody neutralization experiments reveal that IL-6 is responsible for the LPA-induced mitogenic signaling and growth of the LNCaP cells. Our findings reveal that the LPA-regulated secretion of IL-6 is an important messenger linking stromal and epithelial prostate cells, which may be exploited for the effective treatment of patients with advanced prostate cancer.     

Thomsen-Friedenreich (TF) antigen as a target for prostate cancer vaccine: clinical trial results with TF cluster (c)-KLH plus QS21 conjugate vaccine in patients with biochemically relapsed prostate cancer

The differential overexpression of self-antigens on tumor cells is a prime feature of malignant transformation. Thomsen-Friedenreich (TF), a core disaccharide of O-glycosylated complex glycoproteins, is one of many self antigens expressed on malignantly transformed cells that has served as a target for immune recognition and attack. Previously, we conducted clinical trials with a series of synthetic glycolipid, peptide and carbohydrate antigens conjugated to the immunological carrier keyhole limpet hemocyanin (KLH) mixed with the immunological saponin adjuvant, QS21. These trials resulted in the generation of high-titer IgM and IgG antibody responses specific for the individual antigens, and, in several cases, the capacity of those antibodies to mediate complement lysis. Four groups of five patients who had evidence of a biochemical relapse defined as rising prostate-specific antigens (PSAs) following primary therapy for prostate cancer with either prostatectomy or radiation were treated with escalating doses of 1, 3, 10 and 30 g of synthetic TF in a clustered formation (c) which was conjugated to KLH and given with 100 g of QS21. Patients received a total of five subcutaneous vaccines over 6 months and were monitored expectantly with scans every 3–4 months. Serum samples were obtained at weeks 1, 2, 3, 7, 9, 13, 19, 26, 50 and every 3 months. Antibody titers were monitored by ELISA and antibody binding to the cell surface of prostate cell lines was performed by flow cytometry. Complement-dependent cytotoxicity was performed on selected patients. Twenty evaluable patients were accrued to the study, of whom only one did not receive all six vaccinations. All patients developed maximum IgM and IgG antibody titers by week 9. The median IgM antibody titer by week 7 was 1/1,280 at 10 g, 1/320 at 30 g, 1/1,280 at 3 g and 1/1,280 at 1 g dose groups. The IgM titers from all groups remained greater than 1/320 by week 32 and beyond through week 50. We report here the results of a dose-escalating trial of a TF(c)-KLH conjugate vaccine in patients in the clinical state of a rising PSA in the absence of radiographic disease. For the first time, a synthetically made TF trimer or cluster (c) was made with three TF disaccharides attached to three sequential threonines on a peptide backbone. TF(c) doses of 1, 3, 10 and 30 g were conjugated to KLH and administered with QS21. All doses induced high-titer IgM and IgG antibodies against TF. Unlike our findings in previous dose-escalating phase I trials, there did not appear to be increased antibody production with increasing doses of vaccine; higher titers of IgM and IgG antibodies developed at the lowest dose level (1 g). An anti-tumor effect in the form of a change in post-treatment versus pretreatment logPSA slopes was also observed. The results justify the inclusion of TF(c) at a dose of 1 g as a relevant antigenic target in a multivalent phase II vaccine trial in patients in the high-risk minimal disease state.Supported by The Prostate Cancer Foundation, The PepsiCo Foundation, The Lawrence and Selma Ruben Foundation, The Sara Chait Foundation, The Breast Cancer Research Foundation and The Carroll Ann Mazzella Fund     

Proteomic analysis of cancer stem cells in human prostate cancer cells

Results from recent studies support the hypothesis that cancer stem cells (CSCs) are responsible for tumor initiation and formation. Here, we applied a proteome profiling approach to investigate the mechanisms of CSCs and to identify potential biomarkers in the prostate cancer cell line DU145. Using MACS, the DU145 prostate cancer cell line was isolated into CD44+ or CD44− cells. In sphere culture, CD44+ cells possessed stem cell characteristics and highly expressed genes known to be important in stem cell maintenance. In addition, they showed strong tumorigenic potential in the clonogenic assay and soft agar colony formation assay. We then analyzed and identified proteins that were differentially expressed between CD44+ and CD44− using two-dimensional gel electrophoresis and LC-MS/MS. Cofilin and Annexin A5, which are associated with proliferation or metastasis in cancer, were found to be positively correlated with CD44 expression. These results provide information that will be important to the development of new cancer diagnostic tools and understanding the mechanisms of CSCs although a more detailed study is necessary to investigate the roles of Cofilin and Annexin A5 in CSCs.     

Telomerase-immortalized non-malignant human prostate epithelial cells retain the properties of multipotent stem cells

Understanding prostate stem cells may provide insight into the origin of prostate cancer. Primary cells have been cultured from human prostate tissue but they usually survive only 15-20 population doublings before undergoing senescence. We report here that RC-170N/h/clone 7 cells, a clonal cell line from hTERT-immortalized primary non-malignant tissue-derived human prostate epithelial cell line (RC170N/h), retain multipotent stem cell properties. The RC-170N/h/clone 7 cells expressed a human embryonic stem cell marker, Oct-4, and potential prostate epithelial stem cell markers, CD133, integrin alpha2beta1(hi) and CD44. The RC-170N/h/clone 7 cells proliferated in KGM and Dulbecco's Modified Eagle Medium with 10% fetal bovine serum and 5 microg/ml insulin (DMEM+10% FBS+Ins.) medium, and differentiated into epithelial stem cells that expressed epithelial cell markers, including CK5/14, CD44, p63 and cytokeratin 18 (CK18); as well as the mesenchymal cell markers, vimentin, desmin; the neuron and neuroendocrine cell marker, chromogranin A. Furthermore the RC170 N/h/clone 7 cells differentiated into multi tissues when transplanted into the sub-renal capsule and subcutaneously of NOD-SCID mice. The results indicate that RC170N/h/clone 7 cells retain the properties of multipotent stem cells and will be useful as a novel cell model for studying the mechanisms of human prostate stem cell differentiation and transformation.