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Background: This study determined the effects of S-allylmercaptocysteine (SAMC), a phytoconstituent from garlic, on the expression of androgen-responsive biomarkers, prostate specific antigen (PSA), and prostate specific membrane antigen (PSMA), in human prostatic carcinoma cells (LNCaP)., Methods: Secretion of PSA was determined as well as the activity of PSMA measured as a function of its ability to hydrolyze poly-gamma-glutamated folate and N-acetylaspartylglutamate (NAAG). Folate hydrolase capacity was also determined in SAMC-treated cells grown in charcoal stripped fetal calf serum (CS-FCS). In addition, testosterone disappearance was measured from culture media of SAMC-treated LNCaP and PC-3 cells as well as from cell free lysates., Results: PSA secretions were significantly decreased compared to control values at 1 day (8.4 +/- 2.6 vs. 18.9 +/- 1.7, P < 0.01), 4 days (18.9 +/- 5.3 vs. 73.8 +/- 4. 4, P < 0.001), and 6 days (35.6 +/- 2.1 vs. 96.5 +/- 17.9 ng/10(5) cells, P < 0.01; mean +/- SD). By contrast, PSMA activity measured as either folate hydrolase or NAAG dipeptidase (NAALADase) activity increased in cells treated with SAMC. PSMA-folate hydrolase activity in SAMC-treated cells grown in CS-FCS increased beyond that observed in cells grown in CS-FCS alone. Pre-exposure of LNCaP cells to SAMC resulted in enhanced rate of testosterone disappearance from culture media at 6 hr (P < 0.01) and at 48 hr (P < 0.001) compared to media from cells not previously exposed to SAMC. Results similar to these were also observed in androgen-independent PC-3 cells treated with SAMC. In lysates of SAMC-treated LNCaP cells, the rate of testosterone catabolism was twice that from phosphate buffered saline (PBS)-treated cells. SAMC-treated LNCaP cells grown in media supplemented with testosterone temporarily exhibited enhanced growth over a 2 day period but cell numbers declined later to levels similar to those of SAMC treatment., Conclusions: These results show that SAMC exhibits differential effects on recognized biomarkers for LNCaP cells similar to those produced by androgen deprivation and strongly suggests that this effect may be mediated, in part, by diminishing the trophic effects of testosterone, likely by converting it to metabolites less reactive toward androgen receptors., (Copyright 2000 Wiley-Liss, Inc.)

Background: Prostate-specific membrane antigen (PSMA) is abundantly expressed in virtually 100% of prostate cancers and metastases. In addition, unlike prostate-specific antigen (PSA), PSMA is upregulated under conditions of androgen deprivation. Therefore, PSMA is an attractive therapeutic target for advanced prostate cancer. Recently, both the promoter and the enhancer driving prostate-specific expression of the PSMA gene were cloned. We describe here our analysis of the PSMA enhancer for the most active region(s) and present a way of using the enhancer in combination with the E. coli cytosine deaminase gene for suicide-driven gene therapy that converts the nontoxic prodrug 5-fluorocytosine (5-FC) into the cytotoxic drug 5-fluorouracil (5-FU) in prostate cancer cells., Methods: Deletion constructs of the full-length PSMA enhancer were subcloned into a luciferase reporter vector containing either the PSMA or SV-40 promoter. The most active portion of the enhancer was then determined via luciferase activity in the C4-2 cell line. We then replaced the luciferase gene with the E. coli cytosine deaminase gene in the subclone that showed the most luciferase activity. The specificity of this technique was examined in vitro, using the prostate cancer cell line LNCaP, its androgen-independent derivative C4-2, and a number of nonprostatic cell lines. The toxicity of 5-FC and 5-FU on transiently transfected cell lines was then compared., Results: The enhancer region originally isolated from the PSMA gene was approximately 2 kb. Deletion constructs revealed that at least two distinct regions seem to contribute to expression of the gene in prostate cancer cells, and therefore the best construct for prostate-specific expression was determined to be 1, 648 bp long. The IC(50) of 5-FC was similar in all cell lines tested (>10 mM). However, transfection with the 1648 nt PSMA enhancer and the PSMA promoter to drive the cytosine deaminase gene enhanced toxicity in a dose-dependent manner more than 50-fold, while cells that did not express the PSMA gene were not significantly sensitized by transfection., Conclusions: Suicide gene therapy using the PSMA enhancer may be of benefit to patients who have undergone androgen ablation therapy and are suffering a relapse of disease., (Copyright 2000 Wiley-Liss, Inc.)

We describe a novel technique for tumor implantation into the prostate of a nude mouse, using a perineal approach. This technique offers the benefit of being able to accurately implant malignant cells into the dorsal prostate without entering the abdominal cavity.

Background: In an effort to discover new prostate-specific antigens (PSAs) to enhance our understanding of the functions and behavior of the prostate and the complex processes involved in prostate tumor progression, the structure and function of the PSM antigen has been elucidated., Methods: The PSM antigen was recognized using the 7E11-C5.3 monoclonal antibody, generated against the LNCaP human prostate adenocarcinoma cell line. The PSM cDNA was isolated by PCR, using tryptic peptides of immunoprecipitated PSM to design degenerate primers., Results: The prostate specific membrane antigen (PSM) is a 100 KD glycoprotein which appears to be a type II integral membrane protein. The protein and cDNA have been extensively characterized and the findings reviewed in the report., Conclusions: PSM, a new prostate antigen is valuable as a marker for hematogenous micro-metastatic tumor dissemination as detected in RT-PCR assays of peripheral blood. PSM has many properties that may be potentially useful as a molecular target in monoclonal antibody directed strategies of tumor imaging and therapy.

In order to develop an animal model that more closely simulates the organ environment and metastatic routes of human prostatic cancer, R3327-MatLyLu tumors were induced by orthotopic implantation in the ventral prostatic lobe of Copenhagen rats. This procedure reproducibly resulted in metastatic spread of the intraprostatic tumor to the pelvic and retroperitoneal lymph nodes, and invariably to the lungs. Further, a tumor recurrence model was established using an approach that combined orthotopic tumor implantation and subsequent surgical resection of the primary tumor. When prostatectomy was carried out 4 days or more after induction, tumors recurred locally in all animals. The surgical procedures described may provide an animal model to test the in vivo response to experimental adjuvant treatment protocols for advanced prostate cancer. Immunological studies are now in progress using cytokine gene-modified prostatic tumor cells as cellular antitumor vaccines in orthotopically established R3327-MatLyLu tumors.

Prostatic tissue extracts from patients with benign prostatic hyperplasia (BPH) and prostatic carcinoma were fractionated using heparin-Sepharose chromatography. The mitogenic activity of eluted fractions on quiescent subconfluent Swiss Albino 3T3 fibroblasts was tested employing a tritiated-thymidine-incorporation assay. Two peaks of activity were consistently noted--one in the void volume and a second fraction which eluted with 1.3-1.6 M NaCl and contained the majority of the mitogenic activity. Both non-heparin- and heparin-binding fractions increased tritiated incorporation into a mouse osteoblast cell line (MC3T3), while only the heparin-binding fractions stimulated a human umbilical vein endothelial cell line (HUV). No increased uptake of thymidine was seen using a human prostatic carcinoma cell line (PC-3). Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE) of lyophilized active fractions showed a persistent band at 17,500 daltons. The purified protein demonstrated angiogenic properties using the chick embryo chorioallantoic membrane (CAM) assay. Western blot analysis using antibodies specific to basic fibroblast growth factor (bFGF) or acidic FGF (aFGF) demonstrated that the former, but not the latter, bound to prostatic growth factor (PrGF), and inhibited its mitogenic activity as well. It appears that PrGF shares homology with basic fibroblast growth factors.

The R3327 MAT-Ly Lu is a prostate derived, anaplastic, hormone independent carcinoma. It spreads primarily to regional lymph nodes, followed by lung metastases. Combination therapy with surgery (tumor removal with or without regional lymphadenectomy) and chemotherapy (ICRF-159) was more effective treatment than either one alone. Primary tumor excision plus lymphadenectomy appeared to reduce the number of pulmonary metastases.

Radiolabeled putrescine is a potential imaging agent for carcinoma of the prostate. The intrinsically high uptake of putrescine into the rat prostate and prostatic carcinoma can be further stimulated by pretreatment of the animals with alpha-difluoromethylornithine (DFMO) uptake, a polyamine synthesis inhibitor. Pharmacological castration of the animals followed by androgen stimulation and DFMO pretreatment achieved a 30:1 prostate/muscle ratio of 14C-putrescine uptake in elderly rats.