Role of peptide growth factors in the prostate: a review

Nitric oxide control of lower genitourinary tract functions: a review

It is apparent that evolving concepts of the regulatory basis for functions in the pelvis must take into account the role exerted by nitric oxide. A recently characterized messenger molecule, nitric oxide has been associated with numerous physiologic processes. Intense investigations of this molecule have extended its importance to several genitourinary functions. Penile erection, micturition, peristalsis of the male excurrent duct system, contractile properties of the prostate, and lumbosacral spinal cord neurotransmission are all functions that may transpire under some degree of control by nitric oxide. Impotence, urinary obstruction, or ejaculatory problems, in turn, may represent alterations of nitric oxide production or action. The strategic manipulation of nitric oxide or its mechanism of action, possibly by pharmacologic means, may restore or produce desired functional effects. These possibilities, therefore, suggest that the advancing knowledge of nitric oxide in the genitourinary tract may be of enormous clinical value in the future.

Effects of hormones on the prostate in adult and aging men and animals

Literature on the effect of steroid hormones (androgens, estrogens, and other steroids), of peptide hormones (e.g., prolactin), and growth factors (e.g., EGF, FGF, TGF-beta), on the effect of castration and of experimental hormone application on the prostate is reviewed. Androgens have inductive, repressive, and interactive effects. They counterbalance an agonistic effect on proliferation and an antagonistic effect on cell death; they may influence DNA synthesis and induce the synthesis of substances with mitogenic effects on the prostate. Estrogens exert direct and indirect effects on the prostate. They suppress the secretion of gonatropins, thus repressing testicular androgen secretion. They stimulate the fibromuscular stroma and induce squamous metaplasia of the epithelium. Estrogens may also be involved in the onset of benign prostatic hyperplasia. Prolactin is preferentially bound in the diseased human prostate. An abundance of information has been gained on EGF, FGF, TGF-beta, and other growth factors. They may be involved in the development of prostatic hyperplasia. Castration leads to a striking reduction in prostatic size in a short period of time due to autophagic and heterophagic processes. In castrated individuals, the prostate is enriched in androgen-independent cells. Experimental hormone application involves the substitution of androgens as well as anti-androgens, long-term application of different hormones, and application of combinations of drugs. The results of several studies are described. Further directions in the field of prostate research should concentrate on the role of growth factors in prostate development and pathology and on the effect of certain lectins on prostate diseases. We think that the investigation of interactions between steroid hormones and growth factors in normal and pathological neovascularization of the prostate is important.

Analysis of cell death and cell proliferation in embryonic stages, normal adult, and aging prostates in human and animals

Homeostasis in the prostate is recognized to be maintained by a complex interplay between the opposing actions of cell proliferation and cell death. Growth regulatory factors that promote or inhibit cell proliferation and promote cellular death have been identified in the prostate. The integration of these forces involves cellular cooperation between the prostatic stroma and epithelium. Hormone-regulated production of growth regulatory factors by one cell type may determine growth stimulation, inhibition, or cell death in a reciprocal cell partner. Imbalance between net cell proliferation and net cell death rates may result in abnormal growth leading to BPH. Additional study of the growth regulatory factors associated with distal vs. proximal epithelial cells and stroma and comparison of growth factor expression by the neonatal, postnatal growing, adult quiescent, and aging prostates will likely provide further insight into the regulation of prostate cell division and death.

Establishment and characterization of an immortalized but non-transformed human prostate epithelial cell line: BPH-1

This report describes the development and characterization of an epithelial cell line (BPH-1) from human prostate tissue obtained by transurethral resection. Primary epithelial cell cultures were immortalized with SV40 large T antigen. One of the isolated clones was designated BPH-1. These cells have a cobblestone appearance in monolayer culture and are non-tumorigenic in nude mice following subcutaneous injection or subrenal capsule grafting. They express the SV40 large T antigen and exhibit increased levels of p53, as determined by immunocytochemistry. Cytogenetic analysis by G-banding demonstrated an aneuploid karyotype with a modal chromosome number of 76 (range 71 to 79, n = 28) and 6 to 8 marker chromosomes. Some structurally rearranged chromosomes were observed, but the Y chromosome was normal. The expressed cytokeratin profile was consistent with a prostatic luminal epithelial cell. This profile was the same as that of primary prostatic epithelial cultures from which the BPH-1 cells were derived. In serum-free culture in plastic dishes epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, fibroblast growth factor (FGF) 1 (aFGF), and FGF 7 (KGF) induced increased proliferation in these cells whereas FGF 2 (bFGF), TGF-beta 1, and TGF-beta 2 inhibited proliferative activity. Testosterone had no direct effect on the proliferative rate of BPH-1 cells. 5 alpha-Reductase, 3 alpha-hydroxysteroid oxidoreductase, and 17 beta-hydroxy-steroid oxidoreductase activities were detected in BPH-1 cells. Expression of androgen receptors and the secretory markers, prostate specific antigen and prostatic acid phosphatase, were not detectable by immunocytochemistry, biochemical assay, or RT-PCR analysis.

Comparative analysis of epidermal growth factor receptor gene expression and protein product in benign, premalignant, and malignant prostate tissue

In order to more clearly define the status of epidermal growth factor receptor (EGFR) in prostate cancer, expression of EGFR transcript and protein was analyzed in paired samples of benign and malignant tissues from 30 radical prostatectomy specimens. Prostate tumors and high grade prostatic intraepithelial neoplasias (PINs) expressed significantly less EGFR protein than benign tissues or low grade PINs (P < 0.001). Expression of EGFR mRNA was analyzed in a subset of the same samples, and was higher in more prostate tumors than benign specimens (P < 0.05). However, differences in mean mRNA expression between malignant and benign tissues were not significant. EGFR mRNA was expressed at moderate or low levels in equivalent numbers of PIN lesions. These results suggest that, although EGFR mRNA expression is somewhat elevated in prostate tumors, EGFR protein expression may be down-regulated in the same malignant tissues. Furthermore, our data demonstrate phenotypic similarity between prostate tumors and high grade PIN at the level of EGFR protein expression.

Differential immunoreactivity of transforming growth factor alpha in benign, dysplastic and malignant prostatic tissues

Immunohistochemical examination of radical prostatectomy specimens from 57 patients was performed to determine the differential expression of transforming growth factor alpha in the human prostate. In addition, epidermal growth factor receptor (EGFr) immunoreactivity was assessed in each case. Stromal versus epithelial staining was determined for each histological subtype: benign prostatic hypertrophy (BPH), prostatic intra-epithelial neoplasia (PIN), and prostatic cancer (CaP) by a single pathologist reviewer. TGFa staining was predominant in stroma while EGFr was localized to the epithelial basal cell layer. Immunoreactivity of both TGFa (P = 0.002) and EGFr (P < 0.001) revealed a significant reduction in CaP compared to BPH or PIN. Autocrine stimulation of EGFr by TGFa or other unrecognized factors may be present in CaP. Conversely, altered stromal influence of CaP via TGFa may be present. These observations could form the basis for future cancer therapeutic strategies using antagonist factors.

Molecular mechanisms of androgen action

Androgens directly regulate a vast number of physiological events. These direct androgen effects are mediated by a nuclear receptor that exhibits four major functions or activities: steroid binding, DNA binding, transactivation, and nuclear localization. The SBD consists of a hydrophobic pocket of amino acids that exhibits high-affinity, androgen-specific binding. Based on studies of mutant AR, it appears that a number of different amino acids contribute to the steroid binding characteristics of the AR. The DNA binding domain confers sequence-specific binding to structures called androgen-responsive elements. The specificity of steroid binding and DNA binding provides a crucial basis for androgen-specific regulation of target genes. The nuclear localization signal shares homology with known nuclear localization signals and, coupled with the presence of androgens, is responsible for localizing the AR to the nucleus. The transactivation functions reside mostly in the NH2 terminus but the responsible domains are as yet poorly defined. Though the different domains can act as independent moieties, one domain can clearly alter the behavior of another domain. For instance, the SBD appears to inhibit the transactivating functions until steroid is bound and the amino terminus prevents DNA binding activity until steroid is bound. The relative ease of introducing mutations with polymerase chain reaction technology will facilitate further delineation of critical amino acids and domains responsible for the various activities of the AR. The recent cloning and characterization of AR promoters revealed that the AR genes are driven by a TATA-less promoter characteristics of housekeeping genes. Analysis of transcription rates, mRNA levels, and protein levels indicates that androgens and pkA and pkC pathways modulate expression of AR mRNA and protein. This indicates that the same signal pathways that interact to regulate androgen target genes also regulate the levels of AR in the target tissues. Surprisingly few androgen-regulated genes have been well characterized for the mechanisms by which androgen regulates the gene. The C(3), Slp, probasin, PSA, and hKLK2 genes have provided examples where androgens regulate transcription. Posttranscriptional regulation by androgens has been demonstrated for the SVP1, 2, 3, and 4 and AR genes. The mechanisms underlying posttranscriptional regulation are poorly defined but substantial progress has been made in defining the critical elements that mediate transcriptional effects of androgens. Transcriptional effects are mediated through binding of androgen-AR complexes to specific DNA sequences called AREs. Simple AREs such as those found in C(3) and kallikrein genes tend to be permissive in that GR and PR can also act through the same element.(ABSTRACT TRUNCATED AT 400 WORDS)