Vitamin KJune 2007
Future perspectives of selective estrogen receptor modulators used alone and in combination with DHEA.
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.
Endocr Relat Cancer. 2006 Jun;13(2):335-55
A guide to issues in microarray analysis: application to endometrial biology.
Within the last decade, the development of DNA microarray technology has enabled the simultaneous measurement of thousands of gene transcripts in a biological sample. Conducting a microarray study is a multi-step process; starting with a well-defined biological question, moving through experimental design, target RNA preparation, microarray hybridisation, image acquisition and data analysis--finishing with a biological interpretation requiring further study. Advances continue to be made in microarray quality and methods of statistical analysis, improving the reliability and therefore appeal of microarray analysis for a wide range of biological questions. The purpose of this review is to provide both an introduction to microarray methodology, as well as a practical guide to the use of microarrays for gene expression analysis, using endometrial biology as an example of the applications of this technology. While recommendations are based on previous experience in our laboratory, this review also summarises the methods currently considered to be best practice in the field.
Reproduction. 2005 Jul;130(1):1-13
Validation of array-based gene expression profiles by real-time (kinetic) RT-PCR.
We evaluated real-time (kinetic) reverse transcription-polymerase chain reaction (RT-PCR) to validate differentially expressed genes identified by DNA arrays. Gene expression of two keratinocyte subclones differing in the physical state of human papillomavirus (episomal or integrated) was used as a model system. High-density filter arrays identified 444 of 588 genes as either negative or expressed with less than twofold difference, and the other 144 genes as expressed uniquely or with more than twofold difference between the two subclones. Real-time RT-PCR used LightCycler-based SYBR Green I dye detection and melting curve analysis to validate the relative change in gene expression. Real-time RT-PCR confirmed the change in expression of 17 of 24 (71%) genes identified by high-density filter arrays. Genes with strong hybridization signals and at least twofold difference were likely to be validated by real-time RT-PCR. This data suggests that (i) both hybridization intensity and the level of differential expression determine the likelihood of validating high-density filter array results and (ii) genes identified by DNA arrays with a two- to fourfold difference in expression cannot be eliminated as false nor be accepted as true without validation. Real-time RT-PCR based on LightCycler technology is well-suited to validate DNA array results because it is quantitative, rapid, and requires 1000-fold less RNA than conventional assays.
J Mol Diagn. 2001 Feb;3(1):26-31
DHT and testosterone, but not DHEA or E2, differentially modulate IGF-I, IGFBP-2, and IGFBP-3 in human prostatic stromal cells.
Prostate cancer is one of the four most common cancers in the United States, affecting one of six men. Increased serum levels of androgens and IGF-I are associated with an augmented risk of prostate cancer. Dihydrotestosterone (DHT) and testosterone (T) stimulate prostate cancer cell growth, development, and function, whereas the effects of DHT and T in prostate stromal cells, and of dehydroepiandrosterone (DHEA) in prostate cancer or stromal cells, are uncertain. We investigated the actions of DHT, T, DHEA, and estradiol (E2) on insulin-like growth factor (IGF)-I, IGF-II, IGF-I receptor (R), IGF-binding protein (IGFBP)-2, IGFBP-3, and IGFBP-5 in primary cultures of human prostatic stromal cells by assessing cell proliferation, mRNA expression, and protein secretion by MTT growth assay, quantitative real-time PCR, and ELISA, respectively. DHT and T each increased IGF-I (7-fold) and decreased IGFBP-3 (2-fold) mRNA expression and protein secretion in a dose- and time-dependent manner and increased IGFBP-2 (2-fold) mRNA in a dose- and time-dependent manner. DHEA and E2 did not significantly alter these measures. Flutamide abolished the DHT-modulated increases in IGF-I and IGFBP-2, suggesting that the influences of DHT and T on these measures were androgen receptor mediated. None of the four steroids significantly affected IGF-IR, IGF-II, or IGFBP-5 mRNA levels or stromal cell proliferation. The effects of DHT on IGF-I, IGFBP-2, and IGFBP-3 were more pronounced in stromal cultures that did not express desmin. These data suggest that DHT and T promote prostate growth partly via modulation of the stromal cell IGF axis, with potential paracrine effects on prostate epithelial cells.
Am J Physiol Endocrinol Metab. 2006 May;290(5):E952-60
Comparative effects of DHEA vs. testosterone, dihydrotestosterone, and estradiol on proliferation and gene expression in human LNCaP prostate cancer cells.
Serum levels of the adrenal androgen dehydroepiandrosterone (DHEA) peak in men and women in the third decade of life and decrease progressively with age. Increasing numbers of middle-aged and older individuals consume over-the-counter preparations of DHEA, hoping it will retard aging by increasing muscle and bone mass and strength, decreasing fat, and improving immunologic and neurobehavioral functions. Because DHEA can serve as a precursor to more potent androgens and estrogens, like testosterone (T), dihydrotestosterone (DHT), and 17beta-estradiol (E2), supplemental DHEA use may pose a cancer risk in patients with nascent or occult prostate cancer. The steroid-responsive human LNCaP prostate cancer cells, containing a functional but mutated androgen receptor (AR), were used to compare effects of DHEA with those of T, DHT, and E2 on cell proliferation and protein and/or gene expression of AR, prostate-specific antigen (PSA), IGF-I, IGF-I receptor (IGF-IR), IGF-II, IGF-binding proteins-2, -3, and -5, (IGFBPs-2, -3, and -5), and estrogen receptor-beta (ERbeta). Cell proliferation assays revealed significant stimulation by all four steroids. DHEA- and E2-induced responses were similar but delayed and reduced compared with that of T and DHT. All four hormones increased gene and/or protein expression of PSA, IGF-IR, IGF-I, and IGFBP-2 and decreased that of AR, ERbeta, IGF-II, and IGFBP-3. There were no significant effects of hormone treatment on IGFBP-5 mRNA. DHEA and E2 responses were similar, and distinct from those of DHT and T, in time- and dose-dependent studies. Further studies of the mechanisms of DHEA effects on prostate cancer epithelial cells of varying AR status, as well as on prostate stromal cells, will be required to discern the implications of DHEA supplementation on prostatic health.
Am J Physiol Endocrinol Metab. 2005 Mar;288(3):E573-84
High bioavailability of dehydroepiandrosterone administered percutaneously in the rat.
Dehydroepiandrosterone (DHEA) administered percutaneously by twice daily application for 7 days to the dorsal skin of the rat stimulates an increase in ventral prostate weight with approximately one third the potency of the compound given by subcutaneous injection. The doses required to achieve a 50% reversal of the inhibitory effect of orchiectomy are approximately 3 and 1 mg respectively. By the oral route, on the other hand. DHEA has only 10-15% of the activity of the compound given percutaneously. Taking the bioavailability obtained by the subcutaneous route as 100%, it is estimated that the potencies of DHEA by the percutaneous and oral routes are approximately 33 and 3% respectively. Similar ratios of activity were obtained when dorsal prostate and seminal vesicle weight were used as parameters of androgenic activity. When examined on an estrogen-sensitive parameter, namely uterine weight in ovariectomized rats, the stimulatory effect of DHEA was much less potent than its androgenic activity measured in the male animal, a 50% reversal of the inhibitory effect of ovariectomy on uterine weight being observed at the 3 and 30 mg doses of DHEA administered by the subcutaneous and percutaneous routes respectively. When measured on uterine weight, percutaneous DHEA thus shows a 10% potency compared with the subcutaneous route. The sulfate of DHEA (DHEA-S), on the other hand, was approximately 50% as potent as DHEA at increasing ventral prostate weight after subcutaneous or percutaneous administration. When the effect was measured on dorsal prostate and seminal vesicle weight, percutaneous DHEA-S had 10-25% of the activity of DHEA. DHEA decreased serum LH levels in ovariectomized animals, an effect which was completely reversed by treatment with the antiandrogen flutamide. On the other hand, flutamide had no significant effect on the increase in uterine weight caused by DHEA, thus suggesting a predominant estrogenic effect of DHEA at the level of the uterus and an estrogenic effect on the feedback control of LH secretion. The present data show a relatively high bioavailability of percutaneous DHEA as measured by its androgenic and/or estrogenic biological activity in well-characterized peripheral target intracrime tissues in the rat.
J Endocrinol. 1996 Sep;150 Suppl:S107-18