Induction of metachromasia in experimentally induced hyperplastic/hypertrophic changes in the prostate of the cynomolgus monkey (Macaca fascicularis)

Adoptive immunotherapy prevents prostate cancer in a transgenic animal model

Cancer-related mortality can be decreased by prevention, early detection and improved therapies. Although animal models should be used to evaluate the success of cancer therapies, their usefulness is controversial. Many cancer therapies that have cured tumors in mice have not met with similar success when attempted in humans. Current animal models rely mainly on inoculating cell lines into animals, a method that does not reproduce the natural development of the tumor, both for the kinetics of induction and the anatomical site concerned. In this study, we have used an SV40 T-antigen-transgenic mouse model of prostate cancer in which the tumor spontaneously develops orthotopically with a disease progression that closely resembles the progression of human prostate cancer. We have used this model to test the suitability of adoptive cellular immunotherapy. Transfer of naive cells obtained from a T-antigen-negative congenic animal had significant but partial effects: it prevented development of malignant tumors, leaving just minor foci of residual tumor and/or hyperplasia. Adoptive transfer of memory lymphocytes specific for T-antigen, which is a prostatic self antigen in this model, prevented tumor development and progression without affecting the morphology and function of involved tissues. Treated animals were able to breed, and their survival was greatly increased. These results strongly suggest that adoptive immunotherapy should be successful in treating early stages of human prostate cancer.

Human prostatic smooth muscle cells in culture: estradiol enhances expression of smooth muscle cell-specific markers

Smooth muscle cells (SMCs) constitute a major cellular component of prostatic stroma. SMC tension plays an important role in urethral obstruction secondary to benign prostatic hyperplasia (BPH). We have developed an in vitro procedure for the propagation of human prostatic SMCs. Tissue specimens from patients undergoing radical prostatectomy or cystectomy were enzymatically disaggregated and cultured in MCDB-131 medium supplemented with horse serum, insulin, conditioned medium from the tumor cell line CRL-5813, and steroid hormones. The medium was assembled on the basis of the effects these supplements have on the growth of SMC cultures and on the expression of the two markers desmin and smooth muscle myosin. Addition of 0.1 microM of estradiol to the growth medium dramatically increased expression of these SMC-specific markers. Dihydrotestosterone (DHT) and hydrocortisone had a similar, albeit less pronounced effect. At three to five passages, about two thirds of the cells were immunohistologically positive for smooth muscle myosin or desmin. Almost all cells were positive for the myofibroblast marker smooth muscle alpha-actin throughout 10 passages and more. In SMC cultures, cells staining for smooth muscle myosin and desmin were found to seek direct contact to myofibroblasts. They grew in aggregates on a layer of myofibroblasts which adhered to the surface of the culture vessel. As revealed by transmission electron microscopy the cultured cells exhibited morphological features of myofibroblasts. Characteristics of smooth muscle cells, such as prominent bundles of microfilaments associated with dense bodies, basal laminae investing the cells, and numerous caveolae at the cell surfaces were regularly observed in cultures of low passages. After several passages, these features were markedly decreased and organelles of the biosynthetic system became more prominent. In summary, we present an in vitro model of prostatic SMCs and demonstrate that steroid hormones have characteristic effects on these cells. SMC cultures are expected to facilitate investigation of the functions and properties of human prostatic SMCs.

Prostate cancer in a transgenic mouse

Progress toward understanding the biology of prostate cancer has been slow due to the few animal research models available to study the spectrum of this uniquely human disease. To develop an animal model for prostate cancer, several lines of transgenic mice were generated by using the prostate-specific rat probasin promoter to derive expression of the simian virus 40 large tumor antigen-coding region. Mice expressing high levels of the transgene display progressive forms of prostatic disease that histologically resemble human prostate cancer, ranging from mild intraepithelial hyperplasia to large multinodular malignant neoplasia. Prostate tumors have been detected specifically in the prostate as early as 10 weeks of age. Immunohistochemical analysis of tumor tissue has demonstrated that dorsolateral prostate-specific secretory proteins were confined to well-differentiated ductal epithelial cells adjacent to, or within, the poorly differentiated tumor mass. Prostate tumors in the mice also display elevated levels of nuclear p53 and a decreased heterogeneous pattern of androgen-receptor expression, as observed in advanced human prostate cancer. The establishment of breeding lines of transgenic mice that reproducibly develop prostate cancer provides an animal model system to study the molecular basis of transformation of normal prostatic cells and the factors influencing the progression to metastatic prostate cancer.

Management of benign prostatic hyperplasia with particular emphasis on aromatase inhibitors

The pathogenesis of human benign prostatic hyperplasia (BPH) has not been fully elucidated. There is, however, evidence that estrogens--besides other factors--might play an important role for the growth of the prostate. Consequently, estrogen deprivation might be a new, useful principle for a conservative treatment of BPH. Atamestane, a new, highly selective steroidal aromatase inhibitor has been proven to be successful in antagonizing experimentally-induced estrogen-related stromal overgrowth of the prostate in dogs and monkeys. Double-blind placebo controlled studies are now underway in Europe and the U.S.A. It is anticipated that these studies will give us a definite answer of the clinical validity of this concept in BPH patients in the near future. However, it is very important to take into consideration that for an effective treatment of BPH, a reduction of both the glandular and stromal elements has to be achieved. In other words, both androgens and estrogens seem to be involved in the regulation of (over)growth of the prostate. Therefore, a combination of an androgen and estrogen deprivation might be a more promising approach than any single treatment.

Atamestane: an aromatase inhibitor for the treatment of benign prostatic hyperplasia. A short review

Benign prostatic hyperplasia (BPH) is the most common neoplastic growth in men and is the most frequent cause of urinary flow obstruction at the bladder neck. In addition to the clear evidence in favor of the androgen dependency of BPH, the involvement of the stroma, stromal-epithelial interaction and the role of estrogens have gained much interest in connection with the pathogenesis of this disease. For this reason, specific aromatase inhibitors such as atamestane (1-methyl-1,4-androstadiene-3,17-dione) have recently attracted attention due to their potential use in the treatment of BPH. The pharmacological action of atamestane as a new competitive and irreversible inhibitor of estrogen biosynthesis has been evaluated in mice, rats, rabbits, dogs, monkeys and in man. In all species tested so far, atamestane lacks other intrinsic hormonal or antihormonal activities and shows no inhibition of other cytochrome-P450 dependent enzymes of adrenal steroidogenesis. However, it inhibits the estrogen-related negative feed-back. The extent and consequence of the induced counter-regulation of the pituitary-hypothalamic axis show major sex- and species-specific differences. In BPH animal models, atamestane is highly effective in inhibiting estrogen-induced hyperplastic changes in the fibromuscular stroma of the prostate in androstenedione-treated dogs and monkeys. In male volunteers and BPH patients, atamestane induces an expected dose-dependent reduction of serum estrogen concentrations with slight increases in androgen level. In conclusion, all available results indicate that atamestane is a selective (no inhibition of adrenal function), pure (= specific--no endocrine side-effects) and highly effective steroidal aromatase inhibitor with excellent safety profile. Based on our preliminary results aromatase inhibitors seem to be promising compounds for the treatment of BPH.