Markers Of Prostate Cancer Progression Research Articles

P16INK4a, PTEN, E-cadherin, Bcl-2 and Ki-67 Expression in Prostate Cancer: Its Relationship with the Metastatic Potential and Known Prognostic Factors

BACKGROUNDAt present, adequate prognostic markers for prostate cancer progression are still lacking, in spite of intensive investigation. Accordingly, our study examined the relationship between expression of candidate biomarkers and metastasis in prostate cancer patients. Correlation of molecular markers with prostate-specific antigen (PSA) level, Gleason sum score and tumor stage were also evaluated.METHODSA total of 105 prostate tumor specimens and specimens from 19 cases of nodular hyperplasia were obtained through Yeungnam University Hospital from 2007 to 2008. Immunohistochemical analyses for p16INK4a, phosphatase and tensin homolog (PTEN), E-cadherin, Ki-67 and Bcl-2 were performed.RESULTSOverexpression of Bcl-2 was significantly related to bone (p = 0.006) and nodal metastases (p = 0.017). Other biomarkers were not related to metastatic potential. There were statistically significant relationships between increased PSA level and loss of expression of PTEN (p = 0.019) and E-cadherin (p = 0.001). High Ki-67 index was significantly correlated with nodal metastasis (p = 0.029) as well as with loss of p16INK4a expression (p = 0.002) and high Gleason score (p = 0.011).CONCLUSIONSHigh Gleason score, Bcl-2 overexpression and increased Ki-67 labeling have significant predictive value in assessing the potential for prostate cancer metastasis. In addition, a high Ki-67 index is related to high Gleason score and loss of p16INK4a expression.

Promoter Methylation in APC, RUNX3, and GSTP1 and Mortality in Prostate Cancer Patients

PURPOSE There is a need to better understand prostate cancer progression and identify new prognostic markers for this tumor. We investigated the association between promoter methylation in a priori selected genes and survival in two independent large series of prostate cancer patients. METHODS We followed up with two cohorts of patients (216 patients diagnosed in 1982 to 1988 and 243 patients diagnosed in 1993 to 1996) diagnosed at one hospital pathology ward in Turin, Italy. DNA was obtained from paraffin-embedded tumor tissues and evaluated for promoter methylation status in glutathione S-transferase (GSTP1), adenomatous polyposis coli (APC), and runt-related transcription factor 3 (RUNX3). Results The two cohorts had different prevalences of methylation in APC (P = .047), GSTP1 (P = .002), and RUNX3 (P < .001). Methylation in APC was associated with an increased risk of prostate cancer-specific mortality (hazard ratio [HR] = 1.42; 95% CI, 0.98 to 2.07 in the 1980s cohort; HR = 1.57; 95% CI, 0.95 to 2.62 in the 1990s cohort; HR = 1.49; 95% CI, 1.11 to 2.00 in the two cohorts combined). In subgroup analyses, the HRs were higher among patients with a Gleason score less than 8 (HR = 1.52; 95% CI, 0.85 to 2.73 in the 1980s cohort; HR = 2.09; 95% CI, 1.02 to 4.28 in the 1990s cohort). Methylation in RUNX3 was associated with prostate cancer mortality only in the 1990s cohort, and methylation in GSTP1 did not predict mortality in either cohort. CONCLUSION The pattern of hypermethylation may have changed after the introduction of prostate-specific antigen testing in the beginning of the 1990s. Promoter methylation in APC was identified as a marker for prostate cancer progression.

A Study of Diffusion-Weighted Magnetic Resonance Imaging in Men with Untreated Localised Prostate Cancer on Active Surveillance

BackgroundMarkers that predict the behaviour of localised prostate cancer are needed to identify patients that require treatment. ObjectiveWe have analysed the apparent diffusion coefficient (ADC) generated from diffusion-weighted magnetic resonance imaging (DW-MRI) with respect to repeat biopsy findings and time to radical treatment in patients in a prospective study of active surveillance. Design, setting, and participantsSome 86 men recruited between 2002 and 2006 were followed for a median of 29 mo. Patients had clinical stage T1/T2a N0/Nx M0/Mx adenocarcinoma of the prostate, prostate-specific antigen (PSA) level <15 ng/ml, Gleason score ≤7, primary Gleason grade ≤3, and positive biopsy cores (pbc) ≤50%. MeasurementsAll patients had DW-MRI in addition to standard MRI sequences. Tumour regions of interest (ROIs) were identified using T2-weighted fast-spin echo images as focal areas of restricted diffusion. Univariate analyses including all clinical variables and tumour ADC data were performed with respect to repeat biopsy findings and time to radical treatment. Receiver operating curves (ROC) compared predictive variables. Results and limitationsPatients in the study had a median age of 66 yr and a median initial PSA level of 6.7 ng/ml. Some 39 patients (45%) received deferred radical treatment, and 34 patients (40%) had adverse histology on repeat biopsy. According to univariate analysis, tumour ADC was a significant predictor of both adverse repeat biopsy findings (p<0.0001; hazard ratio [HR]: 1.3; 95% confidence interval [CI]: 1.1–1.6), and time to radical treatment (p<0.0001; HR: 1.5; 95% CI: 1.2–1.8). ROC curves for ADC showed an area under the curve (AUC) of 0.7 for prediction of adverse repeat biopsy findings and an AUC of 0.83 for prediction of radical treatment. ConclusionsIn patients with low-risk, localised disease, tumour ADC on DW-MRI may be a useful marker of prostate cancer progression and may help to identify patients who stand to benefit from radical treatment. This possibility warrants further study.

Moderate Expression of Prostate-Specific Membrane Antigen, a Tissue Differentiation Antigen and Folate Hydrolase, Facilitates Prostate Carcinogenesis

Increased expression of PSMA, a differentiation antigen with folate hydrolase activity, is an independent marker of prostate cancer progression. Mice expressing moderate levels of human PSMA in their prostate develop PIN-like lesions by 9 months. The aim of this study was to determine whether PSMA is involved in prostate carcinogenesis and progression and, if so, the possible mechanism by which PSMA may exert its effects. Using prostates from PSMA-transgenic mice, we developed a tissue recombinant model that exhibits small atypical glands with features of adenocarcinoma. This was not observed in tissue recombinants that were composed of prostate tissues from the wild-type siblings. Cells from PSMA-transgenic tissue recombinants have the ability to form colonies in semisolid agar. PSMA may facilitate this phenotype by increasing the invasive ability of cells. Ectopic PSMA expression on PC-3 cells increased the invasive capacity of cells in in vitro invasion assays, which could be competed out by folic acid. These results suggest PSMA facilitates the development of prostate cancer, and the invasive ability of these cells may be modulated by folate levels. These findings show a novel mechanism that may contribute to the known role of folate in cancer prevention, and may lead to the use of PSMA inhibitors as novel chemopreventive agents for prostate cancer. Moreover, our model should prove useful for further dissecting pathways involved in prostate carcinogenesis and progression.

Validation of NF-kappaB p65 as a prostate cancer prognostic marker on a large cohort of European patients

11055 Background: In recent years, NF-kB p65 has become a candidate molecular marker of prostate cancer progression. We and others have shown that the nuclear expression of p65 can predict biochemi...

Phase IIb clinical trial of selenium in prostate cancer patients on active surveillance

5060 Background: The Nutritional Prevention of Cancer Trial demonstrated a 52% lower incidence of prostate cancer in its selenium (Se) arm. Consequently, this trial was designed to assess if Se supplementation would reduce the progression of prostate cancer in subjects on active surveillance for their disease. Methods: A Phase 2b randomized, double-blind placebo-controlled clinical trial was conducted in men with localized prostate cancer who had elected to forego therapy for active surveillance. Subjects <85 years of age with biopsy proven non- metastatic prostate cancer, prostate specific antigen (PSA) levels <50ng/ml, Gleason score <8, no other treatment for prostate cancer, and life expectancy ≥3 years were recruited. A total of 140 men were randomized to placebo (n=46), 200μg/day (n=47) or 800μg/day (n=47) Se p.o. (as selenized yeast) and followed every 3 months for up to 5 years. The primary endpoint was PSA velocity, a surrogate marker of prostate cancer progression. Serum levels of PSA and Se were determined at baseline and at 3-month intervals thereafter. Variance-stabilizing transformation ln(PSA+1) was carried out and PSA velocity (slope of ln(PSA+1)) was estimated using mixed effects regression models. Results: Following adjustment for age, body mass index, serum selenium levels, pack-years of smoking at baseline, duration on study, race, PSA analysis method, and Gleason score; percent changes in PSA velocity (90% CI) for 200 μg/day and 800 μg/day treatment groups vs. placebo were -2.85% (-7.19, 1.70) and -0.70% (-5.16, 3.98), respectively. Estimated mean PSA velocities and PSA doubling times for placebo, 200 μg/day and 800 μg/day treatment groups were 0.09, 0.07, and 0.09 ng/mL/yr; and 4.92, 5.86 and 5.34 years, respectively. Upon secondary analyses, PSA velocity was statistically significantly higher in smokers (vs. non-smokers) (percent change in PSA velocity and 90% CI: 0.09 (0.03, 0.14)). Conclusions: Selenium supplementation did not significantly affect PSA velocity in subjects with non-aggressive disease. Longitudinal analyses also suggest that active surveillance was an appropriate choice for these subjects. Cigarette smoking may influence prostate cancer progression and needs further investigation. This work was supported by PHS CA079080 and CA023074. No significant financial relationships to disclose.

CD6, a novel cell surface marker for prostate cancer progression?

CD6 is involved in cell–cell interactions via binding with CD166. Over‐expression of CD166 is a marker for disease progression in prostate, colon, and breast cancer, whereas the expression of CD6 by epithelial tumor cells has not yet been described.We studied CD6 and CD166 expression, by immunohistochemistry, in 14 prostate primary tumors of Gleason Scores (GS) 6 to 9, 3 metastatic lymph nodes (LNs), and, by flow cytometry in 2 prostate cancer cell lines (PC3 and DU145).We show that prostate tumor cells express CD166, with a stronger expression in high GS. 6/9 specimens of GS 6 and 7 did not show any tumor cells expressing CD6. Few CD166+CD6+ cells were respectively detected in 1/3 and 1/6 specimens of GS 6 and 7. In contrast, large areas with numerous CD166+CD6+ tumor cells were detected in all (5/5) specimens of GS 8 and 9, and 1/6 GS7. Infiltration by CD6 expressing tumor cells was detected in all 3 invaded LNs. CD6 was strongly expressed by 15% of the PC3 and DU145 cells, while most of these cells weakly expressed CD6, and a few were CD6‐. Interestingly all MUC‐1 positive PC3 cells strongly expressed CD6.Our study shows for the first time CD6 expression in prostate cancer, in high GS specimens and LNs, and suggests that CD6/CD166 might be involved in cancer progression. Further studies are necessary to assess the functional phenotype of tumor cells subsets depending on CD6 and CD166 expression.

Estrone sulfate (E 1S), a prognosis marker for tumor aggressiveness in prostate cancer (PCa)

Seeking insight into the possible role of estrogens in prostate cancer (PCa) evolution, we assayed serum E 2, estrone (E 1), and estrone sulfate (E 1S) in 349 PCa and 100 benign prostatic hyperplasia (BPH) patients, and in 208 control subjects in the same age range (50–74 years). E 1 (pmol/L ± S.D.) and E 1S (nmol/L ± S.D.) in the PCa and BPH patients (respectively 126.1 ± 66.1 and 2.82 ± 1.78, and 127.8 ± 56.4 and 2.78 ± 2.12) were significantly higher than in the controls (113.8 ± 47.6 and 2.11 ± 0.96). E 2 was not significantly different among the PCa, BPH, and control groups. These assays were also carried out in PCa patients after partition by prognosis (PSA, Gleason score (GS), histological stage, and surgical margins (SM)). Significantly higher E 1S levels were found in PCa with: PSA > 10 ng/L (3.05 ± 1.92) versus PSA ≤ 10 ng/mL (2.60 ± 1.55), stage pT3-T4 (2.99 ± 1.80) versus pT2 (2.58 ± 1.58), and positive (3.26 ± 1.95) versus negative margins (2.52 ± 1.48). E 1 was higher in poor- than in better-prognosis PCa. E 2 was significantly higher in PCa with GS ≥ 4 + 3 (109.5 ± 43.8) versus GS ≤ 3 + 4 (100.6 ± 36.5) and increased significantly when GS increased from 3 + 3 to 4 + 4. Estrogens, especially E 1S appeared to be possible markers of PCa progression. Attempting to identify potential sources of E 2 in PCa according to prognosis, as well as in BPH, we found a significant correlation coefficient between E 1S and E 2 (0.266–0.347) in poor-prognosis PCa and no correlation in BPH (0.026) and better-prognosis PCa (0.013–0.104). It is as though during progression of PCa from good to poor prognosis there were a shift in the E 1 to E 2 metabolic pathway from predominantly oxidative to predominantly reductive.

Polycyclic Aromatic Hydrocarbon–DNA Adducts in Prostate and Biochemical Recurrence after Prostatectomy

DNA adduct levels may be influenced by metabolic activity, DNA repair capabilities, and genomic integrity, all of which play a role in cancer progression. To determine if elevated DNA adducts are a marker for prostate cancer progression, we measured polycyclic aromatic hydrocarbon-DNA adducts by immunohistochemistry in prostate cells of 368 surgical prostate cancer patients treated at the Henry Ford Hospital in Detroit, Michigan, between September 1999 and July 2004. Patients were followed up to 5 years after surgery with relative risk for biochemical recurrence (BCR) estimated with a Cox proportional hazards model that adjusted for standard clinical risk factors. At 1 year of follow-up, patients with adduct levels above the median in tumor cells [hazard ratio (HR), 2.40; 95% confidence interval (95% CI), 1.10-5.27] and nontumor cells (HR, 3.22; 95% CI, 1.40-7.39) had significant increased risk of BCR, but these HRs decreased to 1.12 (95% CI, 0.68-1.83) and 1.46 (95% CI, 0.89-2.41) in tumor and nontumor cells at 5 years postsurgery. When we restricted our analysis to patients with advanced-stage (III+) disease, those with high adduct levels in either tumor (53.5% versus 30.2%; P = 0.07) or nontumor (55.2% versus 28.6%; P = 0.02) cells had BCR rates almost 2-fold higher. In race-stratified analyses, the greatest risk of BCR associated with high adduct levels (in nontumor cells) was for African American patients younger than 60 years old (HR, 3.79; 95% CI, 1.01-14.30). High polycyclic aromatic hydrocarbon-DNA adduct levels in nontumor prostate cells are most strongly associated with BCR between 1 and 2 years after surgery and in patient subsets defined by younger age, advanced tumor stage, and African American race.

Adiponectin as a potential marker of prostate cancer progression: studies in organ-confined and locally advanced prostate cancer

Serum levels of adiponectin were measured in patients with benign prostatic hyperplasia and prostate cancer of pT2 and pT3 stage. Adiponectin ELISA assay, immunohistochemistry, and selected metabolic and biochemical parameters measurement was performed in 25 patients with benign prostatic hyperplasia and 43 with prostate cancer (17 patients with organ-confined and 26 patients with locally advanced disease). Serum adiponectin levels did not differ between prostate benign hyperplasia and cancer clinical stage T2, but was significantly higher in pT3 relative to pT2 group (14.51+/-4.92 vs. 21.41+/-8.12, P = 0.003). Tissue immunohistochemistry showed enhanced staining in neoplastic prostate glands and intraepithelial neoplasia relative to benign prostatic hyperplasia without distinction between disease grade and stage. Serum adiponectin levels are higher in locally advanced relative to organ-confined prostate cancer and may thus serve as an auxiliary marker providing further improvement for discrimination between pT2 and pT3 stages.

PrLZ Is Expressed in Normal Prostate Development and in Human Prostate Cancer Progression

We previously reported the isolation and characterization of PrLZ, a novel prostate-specific and androgen-responsive gene of the tumor protein D52 family at chromosome 8q21.1. PrLZ is the only known gene in this locus with prostate specificity. Expression level of PrLZ was elevated specifically in cancer cells, suggesting its association with malignancy. To define its biological function in the morphogenesis, development, and functional maturation of the prostate gland and to gain further insight into its role in prostate cancer, we examined PrLZ expression in prostate specimens during early embryonic development and in adult tissue. PrLZ first appears in the nuclei of the prostate epithelia at 16 weeks of gestation before its distribution in the cytoplasm at later ages. Its expression peaks at 24 years of age, declines at 31 years of age, and maintains a minimal level in later age. On prostate cancer development, PrLZ expression is reactivated, and its expression increases from primary localized tumor to bone metastasis. Overexpression of PrLZ in prostate cancer cells accelerates their growth in vitro and tumor formation in vivo. This work identifies PrLZ as a marker for prostate cancer progression and metastasis, and its pattern of expression is suggestive of a proto-oncogene.

SELDI protein profiling of dunning R‐3327 derived cell lines: Identification of molecular markers of prostate cancer progression

We recently demonstrated the protein expression profiling of Dunning rat tumor cell lines of varying metastatic potential (G (0%), AT-1 ( approximately 20%), and MLL (100%)) using SELDI-TOF-MS. As a parallel effort, we have been pursuing the identification of the protein(s) comprising the individual discriminatory "peaks" and evaluating their utility as potential biomarkers for prostate cancer progression. To identify the observed SELDI-TOF-MS m/z (mass/charge) values with discriminatory expression between different sublines, we employed a combination of chemical pre-fractionation, liquid chromatography, gel electrophoresis and tandem mass spectroscopy. Identified proteins were then verified by immuno-assay and Western analysis. A 17.5 K m/z SELDI-TOF-MS peak was found to retain discriminatory value in each of two separate study-sets with an increased expression in the metastatic MLL line. Sequence identification and subsequent immunoassays verified that Histone H2B is the observed 17.5 K m/z SELDI peak. SELDI-based immuno-assay and Western Blotting revealed that Histone H2B is specifically over-expressed in metastatic MLL lines. SELDI-TOF MS analysis of the Dunning prostate cancer cell lines confirmed the consistent overexpression of a 17.5 K m/z peak in metastatic MLL subline. The 17.5 kDa protein from MLL has been isolated and identified as Histone H2B.

Targeting Bone Metastasis in Prostate Cancer with Endothelin Receptor Antagonists

Recent advances in the understanding of prostate cancer biology and its progression to bone metastasis have led to the development of drugs directed against precise molecular alterations in the prostate tumor cell and host cells in the normal bone environment such as osteoclasts and osteoblasts. Endothelins (ETs) and their receptors have emerged as a potential target in prostate cancer bone metastasis. By activating the ETA receptor, ET-1 is pathogenically involved in facilitating several aspects of prostate cancer progression, including proliferation, escape from apoptosis, invasion, and new bone formation, processes that are general to many malignancies. Notwithstanding, there are a number of features specifically driven by the ET axis in prostate cancer, such as creating and perpetuating a unique interaction between the metastatic prostate cancer cell and the bone microenvironment (osteoblast, osteoclast, and stroma) or altering the equilibrium in pain modulation. These features have led to the preferential clinical evaluation of atrasentan (ABT-627) as a biological therapy in prostate carcinoma, first in hormone-refractory prostate cancer. Biological activity of atrasentan in patients with prostate cancer has been shown by the suppression of biochemical markers of prostate cancer progression in bone, and clinical activity is evidenced by a consistent trend demonstrating a delay in time to disease progression when compared with placebo, especially in patients with bone metastases. Further studies of atrasentan and other selective ET-1 antagonists (ZD4054) are ongoing.

Nuclear Localization of Nuclear Factor-κB p65 in Primary Prostate Tumors Is Highly Predictive of Pelvic Lymph Node Metastases

Lymph node invasion (LNI) is associated with increased risk of prostate cancer progression. Unfortunately, pelvic lymph node dissections are fraught with a high rate of false-negative findings, emphasizing the need for highly accurate markers of LNI. Because nuclear factor-kappaB (NF-kappaB) is a candidate marker of prostate cancer progression, we tested the association between nuclear localization of NF-kappaB in radical prostatectomy specimens and the presence of LNI. NF-kappaB expression in radical prostatectomy specimens was assessed with a monoclonal NF-kappaB p65 antibody, in 20 patients with LNI and in 31 controls with no LNI and no biochemical relapse 5 years after radical prostatectomy. Univariate and multivariate logistic regression models were used. The accuracy of multivariate predictions with and without NF-kappaB was quantified with the area under the receiver operating characteristics curve and 200 bootstrap resamples were used to reduce overfit bias. Univariate regression models showed a 7% increase in the odds of observing LNI for each 1% increase in NF-kappaB nuclear staining (odds ratio, 1.07; P = 0.003). In multivariate models, each 1% increase in NF-kappaB was associated with an 8% increase in the odds of LNI (odds ratio, 1.08; P = 0.03) and its statistical significance was only surpassed by the presence of seminal vesicle invasion (P = 0.003). Addition of NF-kappaB to all other predictors increased the accuracy of LNI prediction by 2.3% (from 84.8% to 87.1%; P < 0.001). This is the first study that shows that the extent of nuclear localization of NF-kappaB in primary prostate tumors is highly accurately capable of predicting the probability of locoregional spread of prostate cancer.

Androgen dependent regulation of protein kinase A subunits in prostate cancer cells

Neuroendocrine (NE) cells may play a role in prostate cancer progression. Both androgen deprivation and cAMP are well known inducers of NE differentiation (NED) in the prostate. Gene-expression profiling of LNCaP cells, incubated in androgen stripped medium, showed that the Cβ isoform of PKA is up-regulated during NE differentiation. Furthermore, by using semi-quantitative RT-PCR and immunoblotting analysis, we observed that the Cβ splice variants are differentially regulated during this process. Whereas the Cβ2 splice variant is down-regulated in growth arrested LNCaP cells, the Cβ1, Cβ3 and Cβ4 variants, as well as the RIIβ subunit of PKA, are induced in NE-like LNCaP cells. The opposite effect of Cβ expression could be mimicked by androgen stimulation, implying the Cβ gene of PKA as a putative new target gene for the androgen receptor in prostate cancer. Moreover, to investigate expression of PKA subunits during prostate cancer progression, we did immunoblotting of several prostatic cell lines and normal and tumor tissue from prostate cancer patients. Interestingly, multiple Cβ subunits were also observed in human prostate specimens, and the Cβ2 variant was up-regulated in tumor cells. In conclusion, it seems that the Cβ isoforms play different roles in proliferation and differentiation and could therefore be potential markers for prostate cancer progression.

Fluorescence in situ hybridization analysis of c‐myc amplification in stage T3N0M0 prostate cancer in Japanese patients

Genetic aberration such as the amplification of c-myc has been commonly found in advanced prostate cancer. The aim of this study was to elucidate chromosome 8 alteration, including a gain and amplification of 8q24 (c-myc gene), related to the progression and survival in advanced (Stage C) prostate cancer. We used dual-probe fluorescence in situ hybridization with a centromere-specific probe for chromosome 8 (8cen), and with a region-specific probe for c-myc (8q24) to evaluate genetic changes in tumor samples from 50 patients who had undergone radical retropubic prostatectomy from 1986 to 2001. We classified the 8cen and c-myc copy numbers as normal, gain and amplification. The carcinoma foci with extra copies of c-myc, which was defined in 35 cases (70%), were divided into two groups: (a) a simple gain of the whole chromosome 8 (no increase in the c-myc copy number relative to the chromosome 8 centromere), which was identified in 15 cases (30%); and (b) a substantial amplification of c-myc (additional increases [AI] in the c-myc copy number relative to the chromosome 8 centromere), which was detected in 20 cases (40%). AI-c-myc was strongly associated with higher histopathological grades and Gleason's scores (P = 0.0330, 0.0190, respectively). Patients with the AI-c-myc had earlier disease progression (P = 0.0029) and earlier cancer death (P = 0.0087) than did patients with normal patterns. Identification of an AI-c-myc may serve as a potential marker of prostate cancer progression.

Anoikis and Survival Connections in the Tumor Microenvironment: Is There a Role in Prostate Cancer Metastasis?

Overcoming the androgen independence of prostate tumors is considered the most critical therapeutic end point for improving survival in patients with metastatic prostate cancer. Normal epithelial and endothelial cells can undergo apoptosis when detached from the extracellular matrix (ECM), via the anoikis phenomenon. In contrast, tumor cells upon detachment from the ECM are capable of evading anoikis and metastasizing to different distant organs. Is the biological repertoire of the epithelial and endothelial cells sufficient to account for the events associated with the process of anoikis during prostate cancer metastasis? Although there is no clear answer to this question, what has become increasingly evident from the existing evidence is that molecules that induce anoikis in tumor epithelial and endothelial cells provide exciting new leads into effective therapeutic targeting as well as markers of prostate cancer progression and prediction of therapeutic resistance. This review analyzes recent findings on anoikis regulators and discusses the relevance of this unique apoptosis mode in the development of metastatic prostate cancer and identification of molecular signatures for treatment of advanced disease.

Tocopherol-Associated Protein Suppresses Prostate Cancer Cell Growth by Inhibition of the Phosphoinositide 3-Kinase Pathway

Epidemiologic studies suggested that vitamin E has a protective effect against prostate cancer. We showed here that tocopherol-associated protein (TAP), a vitamin E-binding protein, promoted vitamin E uptake and facilitated vitamin E antiproliferation effect in prostate cancer cells. Interestingly, without vitamin E treatment, overexpression of TAP in prostate cancer cells significantly suppressed cell growth; knockdown of endogenous TAP by TAP small interfering RNA (siRNA) in nonmalignant prostate HPr-1 cells increased cell growth. Further mechanism dissection studies suggested that the tumor suppressor function of TAP was via down-regulation of phosphoinositide 3-kinase (PI3K)/Akt signaling, but not by modulating cell cycle arrest or androgen receptor signaling. Immunoprecipitation results indicated that TAP inhibited the interaction of PI3K subunits, p110 with p85, and subsequently reduced Akt activity. Constitutively active Akt could negate the TAP-suppressive activity on prostate cancer cell growth. Moreover, stable transfection of TAP in LNCaP cells suppressed LNCaP tumor incidence and growth rate in nude mice. Furthermore, TAP mRNA and protein expression levels were significantly down-regulated in human prostate cancer tissue samples compared with benign prostate tissues as measured by reverse transcription-PCR, in situ hybridization, and immunohistochemistry. Together, our data suggest that TAP not only mediates vitamin E absorption to facilitate vitamin E antiproliferation effect in prostate cancer cells, but also functions like a tumor suppressor gene to control cancer cell viability through a non-vitamin E manner. Therefore, TAP may represent a new prognostic marker for prostate cancer progression.

PTOV1 gene expression in prostate cancer

9632 Background: Identification of molecular markers for prostate cancer progression is critical for prognosis and therapeutic targeting. PTOV1 (prostate tumor over expressed) expression has recently been identified as a novel gene involved in promoting prostate cell proliferation by driving cells to enter S phase with an associated increase in cyclin D expression. PTOV1 levels are undetectable in normal prostate tissue and in prostate adenoma, but high in prostate carcinoma and prostate intraepithelial carcinoma. Additionally, PTOV1 has been correlated with PSA levels, making PTOV1 a potential marker for early disease detection and progression. However, PTOV1 levels did not correlate with low p27 levels or high Gleason score, both indicators of aggressive disease. Methods: In order to further characterize the association between PTOV1 and different stages of prostate cancer, we obtained fresh prostate tissue specimens from six advanced prostate carcinoma patients undergoing transurethral resection of prostate due to bladder outlet obstruction. All patients were receiving androgen deprivation. Tissue was also collected from nine patients with newly local stage cancer undergoing prostatectomy. mRNA was isolated from each specimen, and PTOV1 expression was measured by quantitative real-time RT-PCR. Results: All specimens analyzed in both groups expressed PTOV1. The mean expression level of PTOV1 (relative to normalized control, 18s) was lower (p<0.001) in the advanced prostate cancer group (3.75±0.45) compared to the early stage prostate cancer group (6.37±0.37). Conclusion: This study provides direct evidence that PTOV1 expression is decreased in advanced prostate cancer and may not correlate with later events in prostate carcinogenesis. It is not clear whether decreased expression in advanced stage disease is secondary to down-regulation of expression pathways associated with disease progression or due to the effect of androgen deprivation. To define this, further studies will focus on expression analysis in early stage disease patients undergoing neo-adjuvant androgen deprivation followed by prostatectomy to better define the role of hormonal influences on PTOV1 expression. No significant financial relationships to disclose.

Expression of core 2 β1,6-N-acetylglucosaminyltransferase facilitates prostate cancer progression

Cell surface carbohydrates expressed on epithelial cells are thought to play an important role in tumor progression. Previously, we have shown that expression of core 2-branched O-glycans is closely correlated with vessel invasion and depth of invasion in colon and lung carcinomas. In this study, we found that expression of core 2 beta1,6-N-acetylglucosaminyltransferase-1, Core2GnT, is positively correlated with the progression of prostate cancer in human patients. Statistical analysis demonstrated that Core2GnT is an independent predictor for progressed pathological stage (pT3) and for prostate-specific antigen (PSA) relapse. To determine directly the roles of Core2GnT in prostate cancer progression, we set up an experimental tumor model using the LNCaP prostate cancer cell line. Because this line does not express Core2GnT, we established an LNCaP line stably expressing Core2GnT, LNCap-Core2GnT, by transfecting cDNA encoding Core2GnT. When mock-transfected LNCaP cells and LNCaP-Core2GnT were inoculated in the prostate of nude mice, LNCaP-Core2GnT cells produced three times heavier prostate tumors than mock-transfected LNCaP cells. Furthermore, we found that LNCaP-Core2GnT cells adhered more strongly to prostate stromal cells, type IV collagen and laminin than did LNCaP-mock cells, but LNCaP and LNCaP-Core2GnT cells grew almost at the same rate on plates coated with type IV collagen or laminin. These results indicate that Core2GnT is an extremely useful prognostic marker for prostate cancer progression. The results also suggest that acquiring Core2GnT in prostate carcinoma cells facilitates adhesion to type IV collagen and laminin, and this increased adhesion may be a cause for aggressive tumor formation by prostate cancer cells expressing Core2GnT.