Effects of androgen blockade with ketoconazole and megestrol acetate on human prostatic protein patterns

The role of adrenal derived androgens in castration resistant prostate cancer

Castration resistant prostate cancer (CRPC) remains androgen dependant despite castrate levels of circulating testosterone following androgen deprivation therapy, the first line of treatment for advanced metstatic prostate cancer. CRPC is characterized by alterations in the expression levels of steroidgenic enzymes that enable the tumour to derive potent androgens from circulating adrenal androgen precursors. Intratumoral androgen biosynthesis leads to the localized production of both canonical androgens such as 5α-dihydrotestosterone (DHT) as well as less well characterized 11-oxygenated androgens, which until recently have been overlooked in the context of CRPC. In this review we discuss the contribution of both canonical and 11-oxygenated androgen precursors to the intratumoral androgen pool in CRPC. We present evidence that CRPC remains androgen dependent and discuss the alterations in steroidogenic enzyme expression and how these affect the various pathways to intratumoral androgen biosynthesis. Finally we summarize the current treatment strategies for targeting adrenal derived androgen biosynthesis.

Canonical and Noncanonical Androgen Metabolism and Activity

Androgens are critical drivers of prostate cancer. In this chapter we first discuss the canonical pathways of androgen metabolism and their alterations in prostate cancer progression, including the classical, backdoor and 5α-dione pathways, the role of pre-receptor DHT metabolism, and recent findings on oncogenic splicing of steroidogenic enzymes. Next, we discuss the activity and metabolism of non-canonical 11-oxygenated androgens that can activate wild-type AR and are less susceptible to glucuronidation and inactivation than the canonical androgens, thereby serving as an under-recognized reservoir of active ligands. We then discuss an emerging literature on the potential non-canonical role of androgen metabolizing enzymes in driving prostate cancer. We conclude by discussing the potential implications of these findings for prostate cancer progression, particularly in context of new agents such as abiraterone and enzalutamide, which target the AR-axis for prostate cancer therapy, including mechanisms of response and resistance and implications of these findings for future therapy.

Combined blockade of testicular and locally made androgens in prostate cancer: a highly significant medical progress based upon intracrinology

Recently two drugs, namely the antiandrogen MDV-3100 and the inhibitor of 17α-hydroxylase abiraterone have been accepted by the FDA for the treatment of castration-resistant prostate cancer (CRPC) with or without previous chemotherapy, with a prolongation of overall survival of 2.2-4.8 months. While medical (GnRH agonist) or surgical castration reduces the serum levels of testosterone by about 97%, an important concentration of testosterone and dihydrotestosterone remains in the prostate and activates the androgen receptor (AR), thus offering an explanation for the positive data obtained in CRPC. In fact, explanation of the response observed with MDV-3100 or enzalutamide in CRPC is essentially a blockade of the action or formation of intraprostatic androgens. In addition to the inhibition of the action or formation of androgens made locally by the mechanisms of intracrinology, increased AR levels and AR mutations can be involved, especially in very advanced disease. Future developments look at more efficient inhibitors of the action or formation of intraprostatic androgens and starting treatment earlier when blockade of androgens can exert long-term control and even cure prostate cancer treated at a stage before the appearance of metastases. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Castration-resistant prostate cancer: targeting androgen metabolic pathways in recurrent disease

Emerging evidence suggests that despite testicular androgen ablation, residual androgens, likely of adrenal--though potentially of prostatic--origin, play a critical role in the progression of prostate cancer to recurrent "castration-resistant" disease. Thus, a reassessment of the concept of total androgen deprivation is warranted. Current treatment strategies may not only lack optimal efficacy, but may actually contribute to the selection of neoplastic clones adapted to exist and proliferate in a low (but not zero) androgen environment. Moreover, the adequacy of androgen receptor (AR) pathway inhibition cannot be surmised from serum or plasma androgen levels, but must be ascertained at the tissue and molecular level prior to drawing conclusions regarding clinical efficacy or failure. Recent studies by our group and others indicate that prostate cancers undergo an adaptive response to castration that is associated with the up-regulation of transcripts encoding enzymes involved in the biosynthesis of androgens. Targeting these metabolic enzymes either individually or using combinations of agents to inhibit testicular, adrenal, and intracrine sources may provide enhanced clinical responses in the setting of both localized and metastatic disease.

Endocrine treatment of benign prostatic hypertrophy: current concepts

To summarize the endocrine approach for the treatment of BPH: much clinical data have accumulated over the past forty years. Until recently, scientists and physicians mainly concentrated on the reduction of androgens as a possible solution. We have come a long way from surgical castration, through the administration of hormones such as estrogen and progesterone, gonadotropin-releasing hormone agonists to the inhibition of an enzymatic reaction reducing testosterone to DHT--the now recognized active intracellular androgen metabolite. Recently, the role of estrogens has been emphasized with the finding that stromal hyperplasia is the main change occurring in BPH. Lately, research has been initiated to examine the clinical effect aromatase inhibitors would have in the treatment of human BPH. Since there is enough evidence that both the epithelial and stromal components of the human prostate undergo hyperplasia in BPH, and individuals vary with respect to their relative epithelial/stromal components, both structures would have to be reduced for therapy to be successful. Therefore, the combination of an antiandrogenic and antiestrogenic effect is theoretically promising. Indeed, prostates of beagles shrunken after treatment with an aromatase inhibitor, further decreased in weight after additional treatment with cyproterone acetate, an antiandrogen. We are now approaching the stage where these "antihormones" are both enzyme inhibitors with actually no side effects that preclude the use of the earlier generation's "antihormonal" hormonal drugs. Furthermore, it has recently been reported that the aromatase inhibitor, 4-hydroxy-androstenedione also inhibits human prostatic 5-alpha reductase, at least in vitro. The in vivo relevance of this finding awaits further classification. Thus, a good hormonal treatment that will be both scientifically sound, and clinically safe and effective, seems feasible in the near future. Two main factors have encouraged our interest and research into methods of inhibiting prostatic growth or reducing its obstructive symptomatology: the enormous cost of prostatic operations for outlet obstruction secondary to BPH, and the natural aging process of the population accompanied by deteriorated health precluding anesthesia and prostatic surgery. Medical treatment of BPH has to result in symptomatic improvement, elimination of residual urine, and improvement of flow to be considered successful. These are usually accomplished by surgery and results at least as good as those obtained by operation should be aimed at, if medical treatment is to replace surgery. Although indications for surgery and outcome of operations are well-defined, this is not the case when alternatives to prostatectomy are chosen.(ABSTRACT TRUNCATED AT 400 WORDS)