Sex steroids and epidermal growth factor in benign prostatic hyperplasia (BPH)

Adult body size, sexual history and adolescent sexual development, may predict risk of developing prostate cancer: Results from the New South Wales Lifestyle and Evaluation of Risk Study (CLEAR)

Prostate cancer (PC) is the most common non-cutaneous cancer in men worldwide. The relationships between PC and possible risk factors for PC cases (n = 1,181) and male controls (n = 875) from the New South Wales (NSW) Cancer, Lifestyle and Evaluation of Risk Study (CLEAR) were examined in this study. The associations between PC risk and paternal history of PC, body mass index (BMI), medical conditions, sexual behaviour, balding pattern and puberty, after adjusting for age, income, region of birth, place of residence, and PSA testing, were examined. Adjusted risk of PC was higher for men with a paternal history of PC (OR = 2.31; 95%CI: 1.70-3.14), personal history of prostatitis (OR = 2.30; 95%CI: 1.44-3.70), benign prostatic hyperplasia (OR = 2.29; 95%CI: 1.79-2.93), being overweight (vs. normal; OR = 1.24; 95%CI: 0.99-1.55) or obese (vs. normal; OR = 1.44; 95%CI: 1.09-1.89), having reported more than seven sexual partners in a lifetime (vs. < 3 partners; OR = 2.00; 95%CI: 1.49-2.68), and having reported more than 5 orgasms a month prior to PC diagnosis (vs. ≤3 orgasms; OR = 1.59; 95%CI: 1.18-2.15). PC risk was lower for men whose timing of puberty was later than their peers (vs. same as peers; OR = 0.75; 95%CI: 0.59-0.97), and a smaller risk reduction of was observed in men whose timing of puberty was earlier than their peers (vs. same as peers; OR = 0.85; 95%CI: 0.61-1.17). No associations were found between PC risk and vertex balding, erectile function, acne, circumcision, vasectomy, asthma or diabetes. These results support a role for adult body size, sexual activity, and adolescent sexual development in PC development.

Action, localization and structure-function relationship of growth factors and their receptors in the prostate

Whereas the direct action of sex steroids, namely of androgens, on prostate cell division was questioned as early as in the 1970s, and remains so, the interest in prostatic growth factors (GFs) is rather recent but has expanded tremendously in the last five years. This lag period can be partly explained by the fact that, at the time, androgen receptors had just been discovered, and newly developed hormonal regimens or strategies to treat patients with prostate carcinoma (PCa) or epithelioma had generated great enthusiasm and hopes in the medical and scientific community. Another point to consider was the difficulty in maintaining prostate tissues in organ cultures and the relative novelty of culturing prostate epithelial cells in monolayers. Failures of sex steroids to elicit a direct positive response on prostate cell divisionin vitro, as seenin vivo, were interpreted as resulting from inappropriate models or culture conditions. However, the increasing number of reports confirming the lack of mitogenic activity of sex steroidsin vitro, coupled with the powerful mitogenic activity of GFs displayed in other systems, the discovery of GF receptors (GF-Rs), and the elucidation of their signalling pathways showing sex steroid receptors as potential substrates of GF-activated protein kinases gradually led to an increased interest in the putative role of GFs in prostate physiopathology. Of utmost importance was the recognition that hormone refractiveness was responsible for PCa progression, and for the poor outcome of patients with advanced disease under endocrine therapies. This problem remains a major issue and it raises several key questions that need to be solved at the fundamental and clinical levels.

Testosterone metabolism, dose-response relationships and receptor polymorphisms: selected pharmacological/toxicological considerations on benefits versus risks of testosterone therapy in men

In this review selected toxicological problems related to testosterone therapy in hypogonadal men are discussed. Applying "classical" pharmacological/toxicological findings (e.g. animal studies on short- and long-term toxicity) to clinical situations is not very helpful. Molecular biological knowledge and especially evaluation of epidemiological studies, as well as intervention studies, on testosterone therapy in hypogonadal men are more useful. Potential risks include overdosage for lifestyle reasons, e.g. excessive muscle building and reduction of visceral obesity, when erythrocytosis occurs concomitantly. Modern galenic formulations of testosterone administration (e.g. transdermal gel, suitable testosterone esters for intramuscular application and newer oral preparations) avoid supraphysiological serum concentrations, therefore significantly reducing the toxicological risk. A hypothetical model of the toxicological risks of testosterone therapy is given that is based on the influence of testosterone metabolism (aromatization vs. reduction) of the respective parameter/target chosen. Finally, the great influence of polymorphisms of the androgen receptor on the assessment of toxicological risk and on the individualization of androgen therapy is shown. Already existing national, continental and international guidelines or recommendations for the testosterone therapy should be harmonized.

Epidermal growth factor induces cyclin D1 in a human prostate cancer cell line

BACKGROUND

The human prostate carcinoma cell line, LNCaP, proliferates under stimulation by a limited number of mitogenic signals, which include members of the growth factor and steroid hormone families. Androgens and epidermal growth factor (EGF) are among the LNCaP cell mitogens. We tested the hypothesis that these mitogens stimulate LNCaP cell proliferation at least in part through the induction of cyclin D1, a protein requisite for cell cycle progression, which is expressed in the G1 phase of the cell cycle.

METHODS

LNCaP cells were grown in serum-free medium with 10 ng/ml or 100 ng/ml EGF, 0.1 nM or 1.0 nM mibolerone (a potent androgen agonist), or vehicle (distilled water or 0.01% ethanol). Expression of cyclin D, mRNA, and protein were assessed by Northern and Western blot analyses. Transcription regulation was assessed by nuclear runoff assay.

RESULTS

Western analyses demonstrated that EGF stimulated cyclin D1 protein expression 4-fold over 12 hr. Northern analyses showed a 4-fold increase in mRNA expression, peaking within 4 hr of EGF stimulation. There were no effects on cyclin D1 protein or mRNA expression with mibolerone treatments. We further explored the mechanism of cyclin D1 induction. LNCaP cells stimulated for 1 hr with EGF demonstrated a 2-fold increase in cyclin D1 message, as assayed by nuclear runoff transcription assay. In addition, we demonstrated the involvement of the protein kinase C pathway in mediating the EGF induction of cyclin D1.

CONCLUSIONS

We conclude that one of the mechanisms by which growth factors such as EGF may stimulate prostate cell proliferation is through the direct induction of cyclin proteins, which are necessary for entry of cells into mitosis.

The regulatory biology of the human pilosebaceous unit

The last few years have witnessed an acceleration in our understanding of the regulation of the human pilosebaceous unit. Recombination and histochemical experiments are beginning to elucidate the role of homeotic genes, transcription factors, growth factors and adhesion molecules in pilosebaceous embryology. Histochemical studies, experiments in gene-modified animals, and in vitro studies on growing human hairs, have identified a number of growth factors that are central to normal hair growth. Thus epidermal growth factor and transforming growth factor-alpha appear to be involved in the triggering of both anagen and catagen. Insulin-like growth factor-I appears to sustain normal anagen growth, transforming growth factor-beta will inhibit anagen growth, while interleukin-1-alpha and tumour necrosis factor-alpha will induce matrix cell death. These complex growth factor effects are beginning to be moulded into an integrated model of pilosebaceous regulation. The role of steroid hormones in modulating these growth factor effects is also beginning to be understood.