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Prostate cancer has become a major public health issue and the search for etiologic risk factors and the development of chemopreventive agents has gained momentum over the last decade. An important epidemiologic finding has been the association between the consumption of tomato products and a lower risk of prostate cancer. Several investigators have proposed that lycopene, a carotenoid consumed largely from tomato products, may be the component responsible for lowering the risk of prostate cancer. Laboratory and clinical studies have been initiated with the goal of assessing the ability of pure lycopene to serve as a chemopreventive agent for prostate cancer. The focus on lycopene should continue, and an improved understanding of lycopene absorption, distribution, role in antioxidant reactions, and metabolism is critical in the quest to elucidate mechanisms whereby this compound may possibly reduce prostate cancer risk.
Prostate cancer tends to become transformed to androgen-independent disease over time when treated by androgen-deprivation therapy. We used two variants of the human prostate cancer cell line LNCaP to study gene expression differences during prostate cancer progression to androgen-independent disease. Production of prostate-specific antigen was regarded as a marker of androgen-dependence and loss of prostate-specific antigen was regarded as a marker of androgen-independence. mRNA from both cell lines was used for cDNA microarray screening. Differential expression of several genes was confirmed by Northern blotting. Monoamine oxidase A, an Expressed Sequence Tag (EST) similar to rat P044, and EST AA412049 were highly overexpressed in androgen-dependent LNCaP cells. Tissue-type plasminogen activator, interferon-inducible protein p78 (MxB), an EST similar to galectin-1, follistatin, fatty acid-binding protein 5, EST AA609749, annexin I, the interferon-inducible gene 1-8U, and phospholipase D1 were highly overexpressed in androgen-independent LNCaP cells. All studied genes had low or no expression in PC-3 cells. The EST similar to rat P044, the EST similar to galectin-1, follistatin, annexin I, and the interferon-inducible gene 1-8U were also expressed in benign prostatic hyperplasia tissue. The Y-linked ribosomal protein S4, Mat-8, and EST AA307912 were highly expressed in benign prostatic hyperplasia tissue. Additionally, both confirmation of differential expression in Northern blots and in situ hybridization were carried out for monoamine oxidase A, the EST similar to rat P044, the EST similar to galectin-1, fatty acid-binding protein 5, and the interferon-inducible gene 1-8U. We identified several potential prostate cancer markers, indicating that the method used is a useful tool for the screening of cancer markers, but other methods, such as in situ hybridization, are needed to further investigate the observations.
The interplay in prostate cancer bone metastases between the 'seed' (the prostate cancer cells) and the 'soil' (the bone microenvironment) has been increasingly recognized as integral to the remarkable tropism for bone shown by prostate cancer. Increasing research into this area is elucidating the mechanisms involved in this complex 'cross-talk'. Recent developments, including the use of bisphosphonates in metastatic disease, highlight the important role of bone cells in the development and progression of metastatic prostate cancer. We review the current reports emphasising these possible mechanisms and indicating possible factors for future treatment directions.
UNLABELLED: Triiodothyronine is the active thyroid hormone produced by de-iodination of the precursor thyroxine that is necessary for the growth of prostate cancer cells in vitro. For this reason we assessed serum triiodothyronine levels in men with localized prostate cancer, benign prostatic hyperplasia (BPH) and controls in the same age group. MATERIALS AND METHODS: We studied 161 men referred for treatment of localized prostate cancer, 20 with BPH and 27 controls. Serum triiodothyronine was determined by fluorometric immunoassay and a commercially available instrument. RESULTS: Men with BPH had the highest triiodothyronine levels, followed by those with prostate cancer. Controls had the lowest triiodothyronine. There was significant triiodothyronine variation among the 3 groups (1-way ANOVA p = 0.001). In men with BPH serum triiodothyronine was significantly different from that in men with prostate cancer (Tukey's multiple range test p = 0.013). Men with prostate cancer had serum triiodothyronine that was significantly different than in controls (p = 0.048), as did those with BPH (p <0.001). Because serum triiodothyronine normally decreases with age, we performed multivariate analysis of variance controlling for age. There was a significant decrease in serum triiodothyronine with age (p = 0.020). There was also significant triiodothyronine variation among the 3 subject groups independent of age (p <0.001). CONCLUSIONS: Urologists are actively seeking additional biomarkers of prostate cancer aggressiveness. Many prostate cancers are quite indolent and may never cause a problem but it is impossible to identify such tumors with certainty. With more and better biomarkers many older men with prostate cancer may be spared the rigors of radiation therapy and/or surgery as well as complications. Triiodothyronine may be such a biomarker. Also, new prostate cancer and BPH therapies may be directed toward inhibiting the mitogenic effects of triiodothyronine.
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Prostate Cancer Shared Decision, a CD-ROM program produced with the guidance of leading prostate cancer specialists, educates prostate cancer patients and suggests possible treatments. As the first portable, interactive prostate cancer decision-making tool, Prostate Cancer Shared Decision offers expert, plain-language explanations of prostate anatomy, cancer diagnosis, and treatment options. Through answers to lifestyle and attitude questions entered into a series of user-friendly questionnaire screens, Prostate Cancer Shared Decision helps patients understand their disease and feel comfortable with their treatment decision. This type of educational tool is representative of the new technology that is becoming available to patients with prostate cancer.
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PURPOSE: Fatty acid-binding protein (FABP) expression patterns were evaluated as potential markers and therapeutic targets for prostate cancer. EXPERIMENTAL DESIGN: FABP expression levels were determined by reverse transcription-PCR in cultured prostate normal and tumor cells and in human biopsy samples. Regulation of cellular processes was examined using FABP antisense constructs. RESULTS: Prostate cells express a variety of different FABPs. Liver (L)- and intestine-FABPs were elevated 5-9-fold in prostate cancer compared with normal primary prostate cells. In contrast, adipose- and epidermal-FABPs were markedly down-regulated (3-20-fold) in cancer versus normal cells. Similar expression patterns were found in human tissue biopsy samples. However, brain-FABP had a distinct pattern of expression: it was overexpressed only in LNCaP cells and in well-differentiated tissue samples, suggesting a stage-specific expression profile. Secretion of L-FABP protein was observed from DU 145 prostate cancer cells, but not in the culture fluid of normal prostate epithelial cells. Antisense oligodeoxynucleotides, designed to block production of epidermal-FABP (a marker for normal prostate cells), caused increased proliferation in DU 145 prostate cancer cells. In vivid contrast, antisense oligodeoxynucleotides to L-FABP (overexpressed in prostate cancer) decreased proliferation and caused apoptosis. CONCLUSIONS: We propose that there is a distinct balance between these groups of FABPs, whose altered regulation in cells may play a role in prostate cancer. Furthermore, the pattern of expression and secretion of FABPs have the potential to serve as a diagnostic marker for an aggressive phenotype of prostate cancer.
Insulin-like growth factor-I (IGF-I) plays an important role in prostate growth, hyperplasia, and carcinogenesis. Circulating IGF-I levels may be modulated by a genetic cytosine-adenine (CA) repeat polymorphism in the promoter region of IGF-I. The association of the polymorphism with the risk of prostate cancer and benign prostatic hyperplasia (BPH) was explored in 303 patients with prostate cancer, 219 patients with BPH and 262 controls. The number of CA repeats ranged from 15 to 22 in case and control subjects. The 19-CA-repeat allele (19-allele) was more frequently observed in both the prostate cancer and BPH patients compared with the controls (prostate cancer versus control: P<0.001; BPH versus control: P=0.001). Compared with non-carriers of the 19-allele, men homo-zygous for the 19-allele had a significantly increased risk of prostate cancer [age-adjusted odds ratio (aOR) = 3.36, 95% confidence intervals (CI) = 1.30-8.67, P=0.012] or BPH (aOR = 3.53, 95% CI = 1.32-9.46, P=0.012), and those heterozygous for the 19-allele also had an intermediate increased risk of prostate cancer (aOR = 1.78, 95% CI = 1.25-2.53, P=0.001) or BPH (aOR = 1.66, 95% CI = 1.14-2.43, P=0.009). A gene dosage effect for the aORs was found with an increasing number for the 19-allele (P<0.001 in prostate cancer and P=0.001 in BPH). No significant association was found between the presence of the 19-allele and the tumor stage and grade at the time of diagnosis. In conclusion, the 19-allele of IGF-I appears to increase the risk of prostate cancer and BPH with a gene dosage effect in the Japanese population.
A prospective randomized trial was conducted to compare the effects of the nonsteroidal antiandrogen flutamide (250 mg. 3 times daily) plus the luteinizing hormone-releasing hormone analogue goserelin acetate (Zoladex) (3.6 mg. subcutaneous depot injection every 28 days) with goserelin acetate alone in advanced prostatic carcinoma. A total of 571 eligible patients, of whom 57% had distant metastases, showed no difference in subjective or objective response rates, interval to progression, treatment failure or survival after a median followup of 2 years. In the combination group more patients had an early decrease in elevated levels of tumor markers and the small number of patients with an increase in signs and symptoms within the first 4 weeks showed a significant decrease. However, increased gastrointestinal and hepatic toxicity in the combination group resulted in 44 patients being withdrawn from the trial. These results indicate that the combination of goserelin acetate with flutamide provides no long-term clinical benefit in patients with advanced prostatic carcinoma compared to goserelin acetate alone.
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BACKGROUND: Prostate cancer is the most common cancer in American men and the second leading cause of cancer death. All clinical observations correlate poorly differentiated high-grade prostate cancer with disease-specific mortality. The HER2 cell membrane tyrosine kinase, a member of the epidermal growth factor receptor family that is the transcription product of the erbB2neu oncogene, and HER3, a receptor protein of the same family, are overexpressed in prostate cancer and prostatic intraepithelial neoplasia. The ligand for these receptors and another related family member, HER4, has recently been identified by independent investigator groups and called neu differentiation factor (NDF) or heregulin. In vitro treatment of HER2- and HER3- or HER2- and HER4-expressing breast cancer cells stimulates tyrosine phosphorylation of HER2 and produces changes in the rate of proliferation, degree of cellular differentiation, and synthesis of physiologic secretion products. There are no published reports on the expression of NDF and HER4 in prostate cancer or the in vitro effects of NDF in prostate cancer cells. METHODS: Expression of NDF, HER2, HER3, and HER4 was studied in 24 frozen prostatectomy specimens by immunohistochemistry. The biologic effect of human recombinant NDF was studied in vitro, using the LNCaP, PC3, and DU145 human prostate cancer cell lines. HER and NDF protein expression was studied by immunohistochemistry. NDF mRNA was analyzed using reverse transcriptase polymerase chain reaction from whole RNA. The biologic effects of NDF on prostate cancer cells in vitro included cell proliferation, thymidine synthesis, induction of prostate-specific antigen mRNA, anchorage-dependent and anchorage-independent cell growth, and ploidy analysis. Data analysis was performed using Student's t test. RESULTS: Observations in clinical prostatectomy specimens: Immunohistochemistry studies in clinical prostatectomy specimens demonstrate absence of significant NDF expression in prostate cancer, whereas it is expressed in 100% of the stroma, 100% of basal epithelial cells, and 58% of luminal cells in normal and benign hyperplastic prostatic tissue. The HER4 receptor protein is strongly expressed by normal prostate luminal cells, but not prostate cancer. Benign prostate tissue exhibits strong expression of HER2, HER3, and HER4 by basal cells, but only luminal cells significantly express HER4. Only 23% of prostate cancer specimens express HER4, while 95% express HER3 and 82% HER2. Prostatic intraepithelial neoplasia stained similarly to cancer for all proteins studied. Observations in prostate cancer cell lines: In vitro treatment with NDF significantly reduces aneuploidy and proliferation and growth of androgen-sensitive prostate cancer cells. Incubation with NDF also induces prostate-specific antigen mRNA in prostate cancer cells. In spite of displaying NDF mRNA, prostate cancer cells do not produce detectable NDF protein, but express HER2 and HER3 proteins. DISCUSSION: These data suggest that NDF may be a paracrine differentiation factor involved in normal adult prostate physiology and that functional loss of the NDF/HER ligand/ receptor loop may be an early event associated with prostate tumorigenesis.
Prostate cancer risk may be influenced by single genetic variants in the hormone-regulating genes androgen receptor (AR), cytochrome P450 (CYP17), and steroid-5-alpha-reductase type 2 (SRD5A2). In this study, we comprehensively investigated polymorphisms in these three loci and their joint effect in a large population-based study. We selected 23 haplotype-tagging single-nucleotide polymorphisms (htSNP) that could uniquely describe >95% of the haplotypes (6 in AR, 6 in CYP17, and 11 in SRD5A2). These htSNPs were then genotyped in the Cancer Prostate in Sweden population (2,826 case subjects and 1,705 controls). We observed significant association for several SNPs in the AR gene (P = 0.004-0.02) and CYP17 (P = 0.009-0.05) and one SNP in SRD5A2 (P = 0.02). Carriers of the most common AR haplotype had a significant excess risk to develop prostate cancer [odds ratio (OR), 1.25; 95% confidence interval (95% CI), 1.1-1.5; P = 0.002], yielding an estimated population attributable risk of 16% (95% CI, 0.06-0.25). Combining risk alleles from these genes yielded a 12% risk increase for each additional high-risk allele carried (95% CI, 1.1-1.2; P for trend = 9.2 x 10(-5)), with an overall OR of 1.87 (95% CI, 1.0-3.4) for carriers of all five included risk alleles, an OR of 2.13 (P for trend = 8 x 10(-4)) for advanced disease, and an OR of 4.35 (P for trend = 7 x 10(-5)) for disease onset before age 65 years. Genetic variation in key genes in the androgen pathway is important for development of prostate cancer and may account for a considerable proportion of all prostate cancers. Carriers of five high-risk alleles in the AR, CYP17, and SRD5A2 genes are at approximately 2-fold excess risk to develop prostate cancer.
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