One of the mechanisms through which advanced prostate cancer (PCa) usually relapses after androgen deprivation therapy (ADT) is the adaptation to residual androgens in PCa tissue. It has been observed that androgen biosynthesis in PCa tissue plays an important role in this adaptation. In the present study, we investigated how stromal cells affect adrenal androgen dehydroepiandrosterone (DHEA) metabolism in androgen-sensitive PCa LNCaP cells. DHEA alone had little effect on prostate-specific antigen (PSA) promoter activity and the proliferation of LNCaP cells. However, the addition of prostate stromal cells or PCa-derived stromal cells (PCaSC) increased DHEA-induced PSA promoter activity via androgen receptor activation in the LNCaP cells. Moreover, PCaSC stimulated the proliferation of LNCaP cells under physiological concentrations of DHEA. Biosynthesis of testosterone or dihydrotestosterone from DHEA in stromal cells and LNCaP cells was involved in this stimulation of LNCaP cell proliferation. Androgen biosynthesis from DHEA depended upon the activity of various steroidogenic enzymes present in stromal cells. Finally, the dual 5α-reductase inhibitor dutasteride appears to function not only as a 5α-reductase inhibitor but also as a 3β-hydroxysteroid dehydrogenase inhibitor in LNCaP cells. Taken together, this coculture assay system provides new insights of coordinate androgen biosynthesis under the microenvironment of PCa cells before and after ADT, and offers a model system for the identification of important steroidogenic enzymes involved in PCa progression and for the development of the corresponding inhibitors of androgen biosynthesis.
Atsushi Mizokami, Eitetsu Koh, Kouji Izumi, Kazutaka Narimoto, Masashi Takeda, Seijiro Honma, Jinlu Dai, Evan T Keller and Mikio Namiki
Jonathan W Nyce
The activation of TP53 is well known to exert tumor suppressive effects. We have detected a primate-specific adrenal androgen-mediated tumor suppression system in which circulating DHEAS is converted to DHEA specifically in cells in which TP53 has been inactivated. DHEA is an uncompetitive inhibitor of glucose-6-phosphate dehydrogenase (G6PD), an enzyme indispensable for maintaining reactive oxygen species within limits survivable by the cell. Uncompetitive inhibition is otherwise unknown in natural systems because it becomes irreversible in the presence of high concentrations of substrate and inhibitor. In addition to primate-specific circulating DHEAS, a unique, primate-specific sequence motif that disables an activating regulatory site in the glucose-6-phosphatase (G6PC) promoter was also required to enable function of this previously unrecognized tumor suppression system. In human somatic cells, loss of TP53 thus triggers activation of DHEAS transport proteins and steroid sulfatase, which converts circulating DHEAS into intracellular DHEA, and hexokinase which increases glucose-6-phosphate substrate concentration. The triggering of these enzymes in the TP53-affected cell combines with the primate-specific G6PC promoter sequence motif that enables G6P substrate accumulation, driving uncompetitive inhibition of G6PD to irreversibility and ROS-mediated cell death. By this catastrophic ‘kill switch’ mechanism, TP53 mutations are effectively prevented from initiating tumorigenesis in the somatic cells of humans, the primate with the highest peak levels of circulating DHEAS. TP53 mutations in human tumors therefore represent fossils of kill switch failure resulting from an age-related decline in circulating DHEAS, a potentially reversible artifact of hominid evolution.
M J Reed, A Purohit, L W L Woo and B V L Potter
Steroid sulphatases regulate many important physiological processes, including the formation of neurosteroids, some aspects of reproductive function and part of the immune response. Dehydroepiandrosterone sulphatase in macrophages regulates the progression of T0 helper cells to the Th1 phenotype (Daynes et al. 1993, Rook et al. 1994) which secrete cytokines which may be involved in the development of some autoimmune diseases. However, their pivotal role in regulating oestrogen synthesis in endocrine-dependent tumours has been the greatest stimulus in developing potent steroid sulphatase inhibitors. Carlstrom et al. (1984a) made the initial observation that danazol, an isoxazole derivative of 17α-ethinyl testosterone, possessed steroid sulphatase inhibitory properties when it was found that the ratio of dehydroepiandrosterone sulphate (DHEA-S) to unconjugated DHEA increased in women treated with this drug for endometriosis. Subsequent in vitro studies confirmed the ability of danazol to inhibit DHEA sulphatase activity in breast tissues (Carlstrom et al. 1984b).
Christy G Woolcott, Yurii B Shvetsov, Frank Z Stanczyk, Lynne R Wilkens, Kami K White, Christian Caberto, Brian E Henderson, Loïc Le Marchand, Laurence N Kolonel and Marc T Goodman
To add to the existing evidence that comes mostly from White populations, we conducted a nested case–control study to examine the association between sex hormones and breast cancer risk within the Multiethnic Cohort that includes Japanese American, White, Native Hawaiian, African American, and Latina women. Of the postmenopausal women for whom we had a plasma sample, 132 developed breast cancer during follow-up. Two controls per case, matched on study area (Hawaii, Los Angeles), ethnicity/race, birth year, date and time of blood draw and time fasting, were randomly selected from the women who had not developed breast cancer. Levels of estradiol (E2), estrone (E1), androstenedione, dehydroepiandrosterone (DHEA), and testosterone were quantified by RIA after organic extraction and Celite column partition chromatography. E1 sulfate, DHEA sulfate (DHEAS), and sex hormone-binding globulin (SHBG) were quantified by direct immunoassays. Based on conditional logistic regression, the sex hormones were positively associated and SHBG was negatively associated with breast cancer risk. All associations, except those with DHEAS and testosterone showed a significant linear trend. The odds ratio (OR) associated with a doubling of E2 levels was 2.26 (95% confidence interval (CI) 1.58–3.25), and the OR associated with a doubling of testosterone levels was 1.34 (95% CI 0.98–1.82). The associations in Japanese American women, who constituted 54% of our sample, were similar to or nonsignificantly stronger than in the overall group. This study provides the best evidence to date that the association between sex hormones and breast cancer risk is generalizable to an ethnically diverse population.
R Kaaks, S Rinaldi, T J Key, F Berrino, P H M Peeters, C Biessy, L Dossus, A Lukanova, S Bingham, K-T Khaw, N E Allen, H B Bueno-de-Mesquita, C H van Gils, D Grobbee, H Boeing, P H Lahmann, G Nagel, J Chang-Claude, F Clavel-Chapelon, A Fournier, A Thiébaut, C A González, J R Quirós, M-J Tormo, E Ardanaz, P Amiano, V Krogh, D Palli, S Panico, R Tumino, P Vineis, A Trichopoulou, V Kalapothaki, D Trichopoulos, P Ferrari, T Norat, R Saracci and E Riboli
Considerable experimental and epidemiological evidence suggests that elevated endogenous sex steroids — notably androgens and oestrogens — promote breast tumour development. In spite of this evidence, postmenopausal androgen replacement therapy with dehydroepiandrosterone (DHEA) or testosterone has been advocated for the prevention of osteoporosis and improved sexual well-being. We have conducted a case–control study nested within the European Prospective Investigation into Cancer and Nutrition. Levels of DHEA sulphate (DHEAS), (Δ4-androstenedione), testosterone, oestrone, oestradiol and sex-hormone binding globulin (SHBG) were measured in prediagnostic serum samples of 677 postmenopausal women who subsequently developed breast cancer and 1309 matched control subjects. Levels of free testosterone and free oestradiol were calculated from absolute concentrations of testosterone, oestradiol and SHBG. Logistic regression models were used to estimate relative risks of breast cancer by quintiles of hormone concentrations. For all sex steroids –the androgens as well as the oestrogens – elevated serum levels were positively associated with breast cancer risk, while SHBG levels were inversely related to risk. For the androgens, relative risk estimates (95% confidence intervals) between the top and bottom quintiles of the exposure distribution were: DHEAS 1.69 (1.23–2.33), androstenedione 1.94 (1.40–2.69), testosterone 1.85 (1.33–2.57) and free testosterone 2.50 (1.76–3.55). For the oestrogens, relative risk estimates were: oestrone 2.07 (1.42–3.02), oestradiol 2.28 (1.61–3.23) and free oestradiol (odds ratios 2.13 (1.52–2.98)). Adjustments for body mass index or other potential confounding factors did not substantially alter any of these relative risk estimates. Our results have shown that, among postmenopausal women, not only elevated serum oestrogens but also serum androgens are associated with increased breast cancer risk. Since DHEAS and androstenedione are largely of adrenal origin in postmenopausal women, our results indicated that elevated adrenal androgen synthesis is a risk factor for breast cancer. The results from this study caution against the use of DHEA(S), or other androgens, for postmenopausal androgen replacement therapy.
The discovery of medical castration with GnRH agonists in 1979 rapidly replaced surgical castration and high doses of estrogens for the treatment of prostate cancer. Soon afterwards, it was discovered that androgens were made locally in the prostate from the inactive precursor DHEA of adrenal origin, a mechanism called intracrinology. Taking into account these novel facts, combined androgen blockade (CAB) using a pure antiandrogen combined with castration in order to block the two sources of androgens was first published in 1982. CAB was the first treatment shown in randomized and placebo-controlled trials to prolong life in prostate cancer, even at the metastatic stage. Most importantly, the results recently obtained with the novel pure antiandrogen enzalutamide as well as with abiraterone, an inhibitor of 17α-hydroxylase in castration-resistant prostate cancer, has revitalized the CAB concept. The effects of CAB observed on survival of heavily pretreated patients further demonstrates the importance of the androgens made locally in the prostate and are a strong motivation to apply CAB to efficiently block all sources of androgens earlier at start of treatment and, even better, before metastasis occurs. The future of research in this field thus seems to be centered on the development of more potent blockers of androgens formation and action in order to obtain better results at the metastatic stage and, for the localized stage, reduce the duration of treatment required to achieve complete apoptosis and control of prostate cancer proliferation before it reaches the metastatic or noncurable stage.
Christina Wei and Elizabeth C Crowne
Endocrine abnormalities are common among childhood cancer survivors. Abnormalities of the hypothalamic–pituitary–adrenal axis (HPAA) are relatively less common, but the consequences are severe if missed. Patients with tumours located and/or had surgery performed near the hypothalamic–pituitary region and those treated with an accumulative cranial radiotherapy dose of over 30 Gy are most at risk of adrenocorticotrophic hormone (ACTH) deficiency. Primary adrenal insufficiency may occur in patients with tumours located in or involving one or both adrenals. The effects of adjunct therapies also need to be considered, particularly, new immunotherapies. High-dose and/or prolonged courses of glucocorticoid treatment can result in secondary adrenal insufficiency, which may take months to resolve and hence reassessment is important to ensure patients are not left on long-term replacement steroids inappropriately. The prevalence and cumulative incidences of HPAA dysfunction are difficult to quantify because of its non-specific presentation and lack of consensus regarding its investigations. The insulin tolerance test remains the gold standard for the diagnosis of central cortisol deficiency, but due to its risks, alternative methods with reduced diagnostic sensitivities are often used and must be interpreted with caution. ACTH deficiency may develop many years after the completion of oncological treatment alongside other pituitary hormone deficiencies. It is essential that health professionals involved in the long-term follow-up of childhood cancer survivors are aware of individuals at risk of developing HPAA dysfunction and implement appropriate monitoring and treatment.
Breast cancer is the most frequently diagnosed and the second cause of cancer death in women, thus making breast cancer a most feared disease. Since breast cancer metastasizes early and it is unlikely that improvements in the treatment of metastatic disease could permit a cure in most cases in the foreseeable future, it is clear that prevention is essential in order practically to eliminate deaths from breast cancer. Tamoxifen is the only selective estrogen receptor modulator (SERM) currently registered for use in breast cancer prevention; the tamoxifen versus raloxifene study should indicate the efficacy of this compound compared with raloxifene. The recent benefits of aromatase inhibitors over tamoxifen indicate the advantages of a blockade of estrogens more complete than the one achieved with tamoxifen, a SERM having some estrogenic activity in the mammary gland and an even higher estrogenic action in the uterus. However, it is unlikely that the general estrogen ablation achieved with aromatase inhibitors will be acceptable for the long-term use required for prevention. It is thus important to develop SERMs with highly potent and pure antagonistic activity in the mammary gland and uterus while possessing estrogen-like activity in tissues of particular importance for women’s health, namely the bones and the cardiovascular system. However, it is expected that a SERM alone will not meet all the requirements of women’s health at the postmenopause when ovarian estrogen secretion has ceased and peripheral formation of androgens and estrogens from DHEA by intracrine mechanisms is decreased by 60% or more. One possibility is to combine a SERM with DHEA, a precursor of sex steroids that permits, somewhat like SERMs, tissue-specific formation of androgens and/or estrogens according to the level of expression of the steroidogenic and steroid-inactivating enzymes. DHEA could thus compensate for the important loss of androgens that accompanies aging and could also permit sex steroid formation and action in the brain while breast cancer prevention would be achieved by the SERM.
Takako Araki, Ning-Ai Liu, Yukiko Tone, Daniel Cuevas-Ramos, Roy Heltsley, Masahide Tone and Shlomo Melmed
Cushing’s syndrome is caused by excessive adrenocorticotropic hormone (ACTH) secretion derived from pituitary corticotroph tumors (Cushing disease) or from non-pituitary tumors (ectopic Cushing’s syndrome). Hypercortisolemic features of ectopic Cushing’s syndrome are severe, and no definitive treatment for paraneoplastic ACTH excess is available. We aimed to identify subcellular therapeutic targets by elucidating transcriptional regulation of the human ACTH precursor POMC (proopiomelanocortin) and ACTH production in non-pituitary tumor cells and in cell lines derived from patients with ectopic Cushing’s syndrome. We show that ectopic hPOMC transcription proceeds independently of pituitary-specific Tpit/Pitx1 and demonstrate a novel E2F1-mediated transcriptional mechanism regulating hPOMC. We identify an E2F1 cluster binding to the proximal hPOMC promoter region (−42 to +68), with DNA-binding activity determined by the phosphorylation at Ser-337. hPOMC mRNA expression in cancer cells was upregulated (up to 40-fold) by the co-expression of E2F1 and its heterodimer partner DP1. Direct and indirect inhibitors of E2F1 activity suppressed hPOMC gene expression and ACTH by modifying E2F1 DNA-binding activity in ectopic Cushing’s cell lines and primary tumor cells, and also suppressed paraneoplastic ACTH and cortisol levels in xenografted mice. E2F1-mediated hPOMC transcription is a potential target for suppressing ACTH production in ectopic Cushing’s syndrome.
Dimitra A Vassiliadi and Stylianos Tsagarakis
Primary bilateral macronodular adrenal hyperplasia (PBMAH) is a highly heterogeneous entity. The incidental identification of an increasing number of cases has shifted its clinical expression from the rarely encountered severe forms, regarding both cortisol excess and adrenal enlargement, to mild forms of asymptomatic or oligosymptomatic cases with less impressive imaging phenotypes. Activation of cAMP/PKA pathway, either due to alterations of the different downstream signaling pathways or through aberrantly expressed G-protein-coupled receptors, relates to both cortisol secretion and adrenal growth. Germline ARMC5 mutations are a frequent genetic defect. The diagnostic approach consists of both imaging and hormonal characterization. Imaging characterization should be done separately for each lesion. Endocrine evaluation in cases with clinically overt Cushing’s syndrome (CS) is similar to that applied for all forms of CS. In incidentally detected PBMAH, hormonal evaluation includes testing for primary aldosteronism, pheochromocytoma and evaluation for autonomous cortisol secretion, using the 1 mg overnight dexamethasone suppression test. Midnight cortisol or 24-h urinary free cortisol may aid in establishing the degree of cortisol excess. In patients with hypercortisolism, ACTH levels should be measured in order to establish ACTH independency. At variance with other forms of CS, PBMAH may be characterized by a distinct pattern of inefficient steroidogenesis. The appropriate management of PBMAH remains controversial. Bilateral adrenalectomy results in lifetime steroid dependency and is better reserved only for patients with severe CS. Unilateral adrenalectomy might be considered in selected patients. In cases where the regulation of cortisol secretion is mediated by aberrant receptors there is some potential for medical therapy.