Cancer chemoprevention with the adrenocortical steroid dehydroepiandrosterone and structural analogs

DHEA, important source of sex steroids in men and even more in women

A major achievement from 500 million years of evolution is the establishment of a high secretion rate of dehydroepiandrosterone (DHEA) by the human adrenal glands coupled with the indroduction of menopause which stops secretion of estrogens by the ovary. Cessation of estrogen secretion at menopause eliminates the risks of endometrial hyperplasia and cancer which would result from non-opposed estrogen stimulation during the post-menopausal years. In fact, from the time of menopause, DHEA becomes the exclusive and tissue-specific source of sex steroids for all tissues except the uterus. Intracrinology, a term coined in 1988, describes the local formation, action and inactivation of sex steroids from the inactive sex steroid precursor DHEA. Over the past 25 years most, if not all, the genes encoding the human steroidogenic and steroid-inactivating enzymes have been cloned and sequenced and their enzymatic activity characterized. The problem with DHEA, however, is that its secretion decreases from the age of 30 years and is already decreased, on average, by 60% at time of menopause. In addition, there is a large variability in the circulating levels of DHEA with some post-menopausal women having barely detectable serum concentrations of the steroid while others have normal values. Since there is no feedback mechanism controlling DHEA secretion within 'normal' values, women with low DHEA will remain with such a deficit of sex steroids for their remaining lifetime. Since there is no other significant source of sex steroids after menopause, one can reasonably believe that low DHEA is involved, in association with the aging process, in a series of medical problems classically associated with post-menopause, namely osteoporosis, muscle loss, vaginal atrophy, fat accumulation, hot flashes, skin atrophy, type 2 diabetes, memory loss, cognition loss and possibly Alzheimer's disease. A recent randomized, placebo-controlled study has shown that all the signs and symptoms of vaginal atrophy, a classical problem recognized to be due to the hormone deficiency of menopause, can be rapidly improved or corrected by local administration of DHEA without systemic exposure to estrogens. In addition, the four domains of sexual dysfucntion are improved. For the other problems of menopause, although similar large scale, randomized and placebo-controlled studies usually remain to be performed, the available evidence already strongly suggests that they could be improved, corrected or even prevented by exogenous DHEA. In men, the contribution of adrenal DHEA to the total androgen pool has been measured at 40% in 65-75-year-old men. Such data stress the necessity of blocking both the testicular and adrenal sources of androgens in order to achieve optimal benefits in prostate cancer therapy. On the other hand, the comparable decrease in serum DHEA levels observed in both sexes has less consequence in men who continue to receive a practically constant supply of testicular sex steroids during their whole life. In fact, in men, the appearance of hormone-deficiency symptoms common to women is observed at a later age and with a lower degree of severity. Consequently, DHEA replacement has shown much more easily measurable beneficial effects in women. Most importantly, despite the non-scientific and unfortunate availability of DHEA as a food supplement in the United States, a situation that discourages rigorous clinical trials on the crucial physiological and therapeutic role of DHEA, no serious adverse event related to DHEA has ever been reported in the world literature (thousands of subjects exposed) or in the monitoring of adverse events by the FDA (millions of subjects exposed), thus indicating, as expected from its known physiology, the excellent safety profile of DHEA. With today's knowledge, one can reasonably suggest that DHEA offers the promise of a safe and efficient replacement therapy for the multiple problems related to hormone deficiency after menopause without the risks associated with estrogen-based or any other treatments.

Might DHEA be considered a beneficial replacement therapy in the elderly?

Dehydroepiandrosterone (DHEA) [prasterone] is typically secreted by the adrenal glands and its secretory rate changes throughout the human lifespan. When human development is completed and adulthood is reached, DHEA and DHEA sulphate (DHEAS) [PB-008] levels start to decline so that at 70-80 years of age, peak DHEAS concentrations are only 10-20% of those in young adults. This age-associated decrease has been termed 'adrenopause', and since many age-related disturbances have been reported to begin with the decline of DHEA/DHEAS levels, this provides a potential opportunity for use of DHEA as replacement therapy. For these reasons, use of DHEA as a replacement therapy in aging men and women has been proposed and this paper outlines the reported beneficial effects of such treatment in humans. Many interesting results have been obtained in experimental animals suggesting that DHEA positively modulates most age-related disturbances. However, renewed interest in DHEA has arisen as a result of recent studies suggesting that DHEA appears to be beneficial in hypoandrogenic men as well as in postmenopausal and aging women. Menopause is the event in a woman's life that induces a dramatic change in the steroid milieu, and use of DHEA as 'replacement treatment' has been reported to restore both the androgenic and estrogenic environment and reduce most of the symptoms of this change. As menopause is the beginning of the biological transition of women towards senescence, it is of great interest to better understand how DHEA might help to solve and/or overcome the problems of this complex stage of life. In men with adrenal insufficiency and hypogonadism without androgen replacement, DHEA administration results in a significant increase in circulating androgens. Though most data are suggestive for use of DHEA as hormonal replacement treatment, more defined and specific clinical trials are needed to uncover all of the 'secrets' and features of this steroid before it can be used as a standard treatment. Furthermore, DHEA is perceived differently around the world, being considered only a 'dietary supplement' in the US, while in many European countries it is considered a 'true hormone' that has not been approved for use as a hormonal treatment by the European health authorities. This overview offers some points of view on use of DHEA as an experimental hormonal replacement therapy.

Cooperation between Myc and YY1 provides novel silencing transcriptional targets of alpha3beta1-integrin in tumour cells

We show that human osteosarcoma cells (Saos-2) have downregulation of alpha3beta1-integrin compared to normal bone cells; this was further described in human osteosarcomas and in a primary murine sarcoma. The alpha3 gene was silenced in Saos-2 cells causing a low expression of alpha3beta1-integrin and reduction in collagen attachment with increasing migratory capacity. Chromatin immunoprecipitation assay performed on alpha3 promoter established that Myc and Yin Yang protein (YY1) cooperate in tandem to downregulate the alpha3 gene. This silencing mechanism involves the binding of Myc and YY1 to DNA and formation of complexes among Myc/Max, YY1, CREB-binding protein and deacetylation activity. The promoter containing deletions of E-boxes or YY1 cassettes failed to downregulate the transcription of a reporter gene as well as the inhibition of deacetylation activity. Overexpression of both Myc and YY1 was necessary to determine the alpha3-integrin promoter downregulation in normal osteoblasts. This downregulation of alpha3beta1-integrin can contribute to the acquisition of a more aggressive phenotype. YY1 regulated negatively the Myc activity through a direct interaction with the Myc/Max and deacetylase complexes. This represents a novel silencing mechanism with broad implications in the transcription machinery of tumours.

Dehydroepiandrosterone induces apoptosis of thymocyte through Fas/Fas-L pathway

Dehydroepiandrosterone (DHEA), the most plentiful steroid hormone, has been convincingly known to have many biological effects and diverse influence in various types of cells, tissues and organs. The effects of DHEA on the humoral and cellular immune response are widely tested, but it is unclear whether DHEA itself serves as an activator of immune function and the literature pertaining to the in vitro effects of DHEA remains contested. In the present paper, the effects of DHEA on the thymocytes in vitro were studied. The results showed that DHEA could enhance the expression of Fas and Fas-L and induce thymocyte apoptosis. This suggests that dehydroepiandrosterone may induce the apoptosis of thymocyte through Fas/Fas-L pathway.

The involvement of glucose metabolism in the regulation of inducible nitric oxide synthase gene expression in glial cells: possible role of glucose-6-phosphate dehydrogenase and CCAAT/enhancing binding protein

In rat glial cells the lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) gene expression was enhanced by extracellular glucose concentration in a dose-dependent manner. On the other hand, 2-deoxy-d-glucose decreased the LPS-induced iNOS gene expression even in the presence of glucose (6 gm/l), suggesting that glucose metabolism is linked to the regulation of iNOS gene expression. The intracellular NADPH/NADP+ directly correlated with the extracellular glucose concentration, and the reduction of NADPH generation via a block of glucose-6-phosphate dehydrogenase (G6PD) by treatment with dehydroepiandrosterone or the antisense DNA oligomer of G6PD mRNA resulted in the inhibition of iNOS gene expression. Gel shift assays showed that CAAT/enhancing binding protein (C/EBP), rather than AP-1 or NF-kappaB, correlated better with a glucose-dependent increase in iNOS gene expression. The induction of C/EBP DNA binding activity by LPS and glucose was attributable mainly to the increase in C/EBP-delta protein. The cotransfection with wild-type C/EBP-delta increased the iNOS promoter activity to the level achieved with a higher glucose concentration in the presence of LPS. Therefore, our results suggest that C/EBP-delta may be a critical mediator in glucose-mediated regulation of iNOS gene expression.

A novel dehydroepiandrosterone analog improves functional recovery in a rat traumatic brain injury model

The purpose of this study was to investigate the efficacy of a novel steroid, fluasterone (DHEF, a dehydroepiandrosterone (DHEA) analog), at improving functional recovery in a rat model of traumatic brain injury (TBI). The lateral cortical impact model was utilized in two studies of efficacy and therapeutic window. DHEF was given (25 mg/kg, intraperitoneally) at the initial time point and once a day for 2 more days. Study A included four groups: sham injury, vehicle treated (n = 22); injured, vehicle treated (n = 30); injured, pretreated (5-10 min prior to injury, n = 24); and injured, posttreated (initial dose 30 min postinjury, n = 15). Study B (therapeutic window) included five groups: sham injury, vehicle treated (n = 17); injured, vehicle treated (n = 26); and three posttreatment groups: initial dose at 30 min (n = 18), 2 h (n = 23), or 12 h (n = 16) postinjury. Three criteria were used to grade functional recovery. In study A, DHEF improved beam walk performance both with pretreatment (79%) and 30-min posttreatment group (54%; p < 0.01, Dunnett vs. injured vehicle). In study B, the 12-h posttreatment group showed a 97% improvement in beam walk performance (p < 0.01, Dunnett). The 30-min and 12-h posttreatment groups showed a decreased incidence of falls from the beam, which reached statistical significance (p < 0.05, Dunnett). Tests of memory (Morris water maze) and neurological reflexes both revealed significant improvements in all DHEF treatment groups. In cultured rat mesangial cells, DHEF (and DHEA) potently inhibited interleukin-1beta-induced cyclooxygenase-2 (COX2) mRNA and prostaglandin (PGE2) production. In contrast, DHEF treatment did not alter injury-induced COX2 mRNA levels in the cortex or hippocampus. However, DHEF (and DHEA) relaxed ex vivo bovine middle cerebral artery preparations by about 30%, with an IC(50) approximately 40 microM. This was a direct effect on the vascular smooth muscle, independent of the endothelial cell layer. Fluasterone (DHEF) treatments improved functional recovery in a rat TBI model. Possible mechanisms of action for this novel DHEA analog are discussed. These findings suggest an exciting potential use for this agent in the clinical treatment of traumatic brain injury.

A synthetic androstene derivative and a natural androstene metabolite inhibit relapsing-remitting EAE

Experimental allergic encephalomyelitis (EAE), a Th1 polarized demyelinating disease of the central nervous system (CNS), shares many pathological and clinical similarities with multiple sclerosis (MS), and thus represents an attractive animal model for this disease. The goal of this study was to evaluate the suppressive effects of fluasterone (HE2500), a synthetic androstene derivative, and androstenetriol (HE2200), a natural androstene hormone on EAE. SJL mice were immunized with proteolipid protein (PLP) 139-151 peptide/CFA to induce EAE. Starting on day -7, animals were given daily injections (s.c.) of derivatives (3.0 mg) in vehicle, or vehicle alone for 33 days. Both HE2500 and HE2200 significantly delayed the onset, reduced the peak clinical score and cumulative disease index of EAE, and prevented or significantly attenuated relapses. Lower doses or other routes of administration were less effective. Moreover, T cells from treated mice had significantly reduced PLP 139-151-specific T cell proliferation responses and reduced numbers of TNF-alpha- and IFN-gamma-producing cells in the CNS. Daily treatment of B10.PL mice with HE2500, starting on day 0, completely prevented the development of disease in these animals. Finally, SJL mice treated with HE2500 at EAE onset showed significantly reduced mean clinical scores. Thus, these compounds, which have been reported to have a few androgenic or estrogenic side effects, appear to have a potent inhibitory activity in EAE. These observations suggest that HE2500 and/or HE2200 limit the production of autoimmune Th1 associated cytokines, and ultimately may be beneficial for patients with MS or other autoimmune diseases.

[DHEA: an unknown star]

PURPOSE

To clarify the physiological function of dehydroepiandrosterone (DHEA), the most abundant steroid in human plasma, which remains poorly understood. To analyse the beneficial effects of a supplementation in order to alleviate its decrease in ageing and improve well-being.

CURRENT KNOWLEDGE AND KEY POINTS

DHEA (and its sulfate) acts on peripheral tissues as an androgenic and estrogenic precursor. It is also considered as a neurosteroid. DHEA administration in several pathological animal models is promising, especially in metabolic diseases such as obesity and insulin resistance. It appears like a factor of immunomodulation and facilitates cognitive acquisition. In humans there is little evidence that DHEA may be useful in characterized pathologies apart from adrenal insufficiency. An interesting effect was also noted in severe systemic lupus erythematosus. The effects on cognitive and neuropsychiatric diseases such as midlife dysthymia are not yet convincing. Prospective studies of supplementation versus placebo indicate inconstant improvement in well-being in the post-menopausal state. DHEA is not a panacea against ageing despite there being a well-established aging-related decrease of DHEA. Contrary to some assertions there are no proven relations between cardiovascular or cancer risk.

FUTURE PROSPECTS AND PROJECTS

Until now adrenal insufficiency has been the only well-documented indication of an oral DHEA supplementation. However, DHEA may be a good way for androgen supplementation in menopausal men. Further investigations are needed to better know the anti-inflammatory and immunomodulation properties of DHEA. At the least, prospective studies on large populations are necessary to assess the true benefits and dangers of DHEA in prevention of ageing.

Suppression of 12-O-tetradecanoylphorbol-13-acetate-induced epidermal hyperplasia and inflammation by the dehydroepiandrosterone analog 16alpha-fluoro-5-androsten-17-one and its reversal by NADPH liposomes

Dehydroepiandrosterone and related steroids produce cancer-preventive and other potentially important therapeutic effects in laboratory animals. These steroids are potent uncompetitive inhibitors of mammalian glucose-6-phosphate dehydrogenase, the first enzyme in the pentose phosphate pathway. Inhibition of this pathway could have profound effects on the supply of 5-carbon sugars required for nucleic acid synthesis as well as on the availability of nicotinamide adenine dinucleotide phosphate (NADPH) and the cellular redox state. NADPH is a source of reducing equivalents for the production of oxygen free radicals, which act as intermediate messengers stimulating mitogenesis and up-regulating the inflammatory response. Using a mixture of NADPH and cationic liposomes to facilitate uptake of the normally impenetrable dinucleotide, we found that intradermal injections of NADPH-liposomes reversed the anti-inflammatory and anti-hyperplastic effects of the dehydroepiandrosterone analog, 16alpha-fluoro-5-androsten-17-one, in mouse skin treated with 12-O-tetradecanoylphorbol-13-acetate, whereas similar treatment had no apparent effect on the anti-hyperplastic and anti-inflammatory effect of corticosterone.

Protein kinase Calpha promotes apoptotic cell death in gastric cancer cells depending upon loss of anchorage

Disruption of interactions between epithelial cells and extracellular matrix proteins leads to apoptosis of the cells, a phenomenon termed anoikis. Anoikis seems to play important roles in control of cellular positioning and inhibition of inappropriate cell growth. Here we found that a protein kinase C (PKC) activator phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) promoted cell death in human gastric cancer cell lines MKN45 and MKN74 only when they lost anchorage. Loss of anchorage slightly increased enzymatic activity of PKCalpha, and an addition of TPA promoted cell death with further increase of PKCalpha activity, but not PKCbeta in MKN45 cells, implicating an involvement of PKCalpha in anoikis. Furthermore, vaccinia virus-mediated overexpression of PKCalpha strongly increased CPP32 activity in the detached MKN45 and MKN74 cells, and augmented anoikis, however it had little effect on viability and CPP32 activity in the attached cells. Taken together, PKCalpha promotes apoptotic cell death in gastric cancer cells depending upon loss of anchorage, thereby may be a modulator of anoikis.

Increase in hepatic content of oleic acid induced by dehydroepiandrosterone in the rat

The effects of dehydroepiandrosterone (DHEA) on the acyl composition of lipids in rat liver were studied. The content of oleic acid (18:1) in hepatic lipids was increased markedly by feeding rats a diet containing 0.5% (w/w) DHEA for 14 days. Treatment of rats with DHEA caused an increase in the activity of the terminal desaturase of the stearoyl-CoA desaturation system, without changing either the activity of NADH-cytochrome b5 reductase or the microsomal content of cytochrome b5. Among the changes observed in hepatic lipids, the increase in 18:1 content in phosphatidylcholine (PtdCho) was the most prominent; an approximately 2.5-fold increase in the proportion of 18:1 was induced at position 2, but not at position 1, by DHEA. This selective elevation of 18:1 at position 2 of PtdCho seems to be produced by the concerted actions of the induced 1-acylglycerophosphocholine (1-acyl-GPC) acyltransferase and the induced stearoyl-CoA desaturase. The content of 18:1 in serum lipids was unchanged by DHEA treatment, suggesting that secretion of lipids containing 18:1 into the circulation was not affected by DHEA. These results suggest that the elevation of hepatic content of 18:1 caused by DHEA treatment is mainly due to the induction of stearoyl-CoA desaturase.

Postmenopausal dehydroepiandrosterone administration increases free insulin-like growth factor-I and decreases high-density lipoprotein: a six-month trial

OBJECTIVE

To determine the effect of administering 6 months of oral postmenopausal DHEA therapy on serum DHEA, DHEAS, and T levels and on physiologic endpoints including lipoproteins and insulin-like growth factor-I (IGF-I).

DESIGN

Randomized, double-blind, parallel trial.

SETTING

Academic referral practice.

PATIENT(S)

Thirteen normal-weight or overweight, healthy, nonsmoking, postmenopausal women.

INTERVENTION(S)

Administration of oral micronized DHEA (25 mg/d).

MAIN OUTCOME MEASURE(S)

Monthly fasting 23 hours postdose levels of serum DHEA, DHEAS, T, lipoproteins, IGF-I, IGF binding protein-3 (IGFBP-3), and liver function tests. Morphometric indices by dual-energy x-ray absorptiometry scan (percent body fat; lean body mass), immune indices, and insulin sensitivity.

RESULT(S)

Levels of DHEA, DHEAS, and T all rose into premenopausal ranges, but after 6 months, levels of DHEA and T did not differ from baseline or placebo. At 3 months, the ratio of IGF-I to IGFBP-3 rose by 36.1% +/- 12.7%, but it fell to placebo values by 6 months. High-density lipoprotein and apolipoprotein A1 levels declined.

CONCLUSION(S)

Patients appeared to tolerate 6 months of DHEA therapy well. Given the small study size, no statistically significant differences in morphometric indices, immune indices, or insulin-sensitizing properties were observed, but significant attenuation of bioavailability occurred. Supplementation with DHEA increased IGF-I/IGFBP-3 levels at 3 months and decreased high-density lipoprotein and apolipoprotein A1 levels at 6 months.

Natural products and their derivatives as cancer chemopreventive agents

This review summarizes currently available data on the chemopreventive efficacies, proposed mechanisms of action and relationships between activities and structures of natural products like vitamin D, calcium, dehydroepidandrosterone, coenzyme Q10, celery seed oil, parsley leaf oil, sulforaphane, isoflavonoids, lignans, protease inhibitors, tea polyphenols, curcumin, and polysaccharides from Acanthopanax genus.

Role of glucose-6-phosphate dehydrogenase inhibition in the antiproliferative effects of dehydroepiandrosterone on human breast cancer cells

Epidemiological and experimental studies suggest that dehydroepiandrosterone (DHEA) exerts a protective effect against breast cancer. It has been proposed that the non-competitive inhibition of glucose-6-phosphate dehydrogenase (G6PD) contributes to DHEA antitumor action. We evaluated the effects of DHEA on G6PD activity and on the in vitro proliferation of two human breast cancer cell lines, MCF-7 (steroid receptor positive) and MDA-MB-231 (steroid receptor negative), in a serum-free assay. DHEA inhibition of G6PD was only found to occur at concentrations above 10 microM; at these high concentrations, the growth curve was parallel to the enzyme inhibition curve in both cell lines. In contrast, at concentrations in the in vivo breast tissue concentration range, neither cell growth nor enzyme activity was inhibited. The results failed to confirm DHEA's putative anti-tumor action on breast cancer through G6PD inhibition, as the enzyme blockade only becomes apparent at pharmacological concentrations of the steroid.

Antioxidant activity of dioscorea and dehydroepiandrosterone (DHEA) in older humans

Dioscorea is a yam steroid extract used in commercial steroid synthesis and consumed by people. DHEA is a steroid which declines with age, but without known activity. This study was designed to determine whether dioscorea supplementation could increase serum dehydroepiandrosterone sulfate (DHEAS) in humans and modulate lipid levels in older people. The subjects were selected volunteers aged 65-82 years. The serum DHEAS level, lipid peroxidation and lipid profile were assessed. Three weeks of dioscorea supplementation had no affect on serum DHEAS level. However DHEA intake of 85 mg/day increased serum DHEA levels 100.3%. DHEA and dioscorea significantly reduced serum lipid peroxidation, lowered serum triglycerides, phospholipid and increased HDL levels. Both DHEA and the steroid yam extract, dioscorea, have significant activities as antioxidant to modify serum lipid levels.

A review of dehydroepiandrosterone (DHEA)

Dehydroepiandrosterone (DHEA) is quantitatively the most abundant hormone in humans and mammals, with a wide variety of physiological effects, including major regulatory effects upon the immune system. Two of the most striking aspects of DHEA are a steady decline in DHEA with age and a significant deficiency in DHEA in patients with several major diseases, including cancer, atherosclerosis, and Alzheimer's disease. The hormone is secreted in a non-sulfated (DHEA) and sulfated form (DHEA-S). The two are apparently interchangeable, and it appears likely that its physiological effects are achieved by derivative molecules that have yet to be identified.