Biomedical subjects

M Sprong

Publications and source records attributed to M Sprong.

5 recordsLinked to original sources

PubMed2002

Effect of tibolone (Org OD14) and its metabolites on aromatase and estrone sulfatase activity in human breast adipose stromal cells and in MCF-7 and T47D breast cancer cells.

Tibolone (Org OD14) is a synthetic steroid used for post-menopausal hormone replacement therapy (HRT). Since HRT might increase breast cancer risk, it is important to determine the possible effects of tibolone on breast tissues. Tibolone and its metabolites Org 4094, Org 30126 and Org OM38 have been reported to inhibit estrone sulfatase activity in MCF-7 and T47D breast cancer cell lines, which suggest beneficial effects on hormone dependent breast cancer by reducing local production of free estrogens. Breast adipose stromal cells (ASCs) contain aromatase activity-an obligatory step in the biosynthesis of estrogens-and possibly contain sulfatase activity. We investigated the effects of tibolone, its metabolites and the pure progestin Org 2058 on PGE(2)-stimulated aromatase activity and on sulfatase activity in human ASC primary cultures and on sulfatase activity in MCF-7 and T47D cell lines. In MCF-7, tibolone and metabolites, but not Org 2058, were found to inhibit sulfatase activity. In T47D, tibolone inhibited sulfatase only at 10(-6)M, although weakly. ASC had high sulfatase activity, which was inhibited by 10(-6)M of tibolone, Org 4094 and Org 30126, but not by Org OM38 or Org 2058. Surprisingly, aromatase activity in ASC was increased by both tibolone and Org 2058 at 10(-6)M. As ligand binding assay results and immunohistochemistry indicated the absence of progesterone and estrogen receptors in ASC, these effects on aromatase and sulfatase activity in ASC likely take place by other routes. Because tibolone and its metabolites inhibit sulfatase activity, and because tibolone only increases aromatase activity at a high concentration, we conclude that effects of tibolone on the breast are probably safe.

17-Hydroxysteroid Dehydrogenases↗

PubMed2002

Progesterone receptor, bc1-2 and bax expression in meningiomas.

Meningiomas are generally benign central nervous system neoplasms, which frequently express progesterone receptor (PR) and only rarely express the estrogen receptor (ER). For breast cancer, a relation between steroid hormone receptors and proteins involved in the apoptotic process has been described. For meningiomas, the exact relation between PR and these proteins is not known. In this study, ER, PR, bcl-2 and bcl-2-associated x protein (Bax) expression levels were determined in meningioma cytosols. As a reference for our experimental conditions, we also determined these proteins in breast cancer cytosols. PR and ER were determined with a ligand-binding assay and scatchard-plot analysis. The expression levels of the anti- and pro-apoptotic proteins, bcl-2 and Bax, respectively, were determined by immunoblotting. In 65% of the meningioma, bcl-2 expression was found in variable amounts. In contrast to breast cancer, a significant negative association between PR and bcl-2 was found (P < 0.01). Bax expression appeared constitutive, not related to PR, and 2.6 times higher than breast cancer. As both PR and bcl-2 appear positively associated with prognosis, the negative relationship between bcl-2 and PR found in this study might have some biological and clinical significance.

Apoptosis↗

PubMed2001

Progesterone receptor isoform expression in human meningiomas.

The majority of meningiomas express the progesterone receptor (PR), and therefore meningiomas are considered to be progesterone-responsive. In addition, an association has been reported between PR and prognosis. At least two PR isoforms exist, PR-B (116--120 kDa) and PR-A (81 kDa), each of which are likely to have different biological functions. Knowledge of the differential expression of both isoforms is necessary to understand the effects of progesterone on meningioma growth. Therefore, in this study, PR-A and PR-B expression levels were determined in 61 human meningiomas by immunoblotting. Total PR expression levels were determined with a ligand binding assay (LBA) (total PR(LBA)). Both PR isoforms and an additional PR 78 kDa protein (PR-78) were expressed in the meningiomas. Meningiomas expressing more PR-A than PR-B had significantly higher total PR(LBA) levels (P<0.001). The PR-78 band intensity was negatively associated with that of PR-B (r(s)=-0.76, P<0.0001). PR-78 may represent an endogenous degradation product, but a similar regulation pathway in the biogenesis of both PR-B and PR-78 is not excluded. Meningiomas contain both PR isoforms, but in highly variable ratios and this variability may have some biological significance. Most meningiomas express more PR-A than PR-B. Therefore in meningioma, assuming that PR-B is more transcriptionally active than PR-A, progesterone responsiveness could be based on transrepression rather than on transactivation of target genes, and progesterone blockade may only be effective in certain subsets of meningiomas.

Aged↗

PubMed2001

Levels of estrogen and progesterone receptors in the myometrium and leiomyoma tissue after suppression of estrogens with gonadotropin releasing hormone analogs.

Gonadotropin releasing hormone (GnRH) agonists are successfully used in the treatment of uterine leiomyomas. Different GnRH agonists may have different local effects on steroid receptors. This study was designed to evaluate potential differences in this respect between triptorelin (Decapeptyl) and goserelin (Zoladex) in a randomized controlled multicenter study using untreated patients during the luteal phase of their menstrual cycle as controls. Estrogen receptors (ERs) and progestin receptors (PRs) were measured by ligand binding assay in myoma and myometrium tissue following a 4-month treatment course with one of the GnRH analogs. In 18 untreated patients median values of ER and PR contents were comparable in myoma and myometrium: for ER at median levels of 56 and 43 fmol/mg protein, respectively; and for PR, median binding capacities were 690 and 730 fmol/mg protein, respectively. Both types of GnRH treatment (total number of patients 34) were associated with significant rises in ER in myoma (to a median level of 279 fmol/mg protein, p<0.001) and myometrium (to a median level of 109 fmol/mg protein, p<0.01). The increase in ER in myomas was significantly (p<0.001) greater than in myometria of the same patients (n=30). After treatment, PR in myomas (median level 520 fmol/mg protein) did not change significantly, but a significant (p<0.05) decrease was found for myometria (median level of 320 fmol/mg protein). Thus, ER and PR concentrations in myoma and myometrium are comparable before treatment, but estrogen suppression with GnRH analogs leads to a larger increase of ER level in leiomyomas than in myometrium, without an effect on PR, whereas myometria had lower PR levels. Therefore, leiomyoma reacts differently from myometrium towards lowered steroid concentrations in the circulation. Since the PR is considered to be a marker of estrogenic stimulation, this indicates remaining estrogenic effects on leiomyomas despite the large decrease of plasma estrogen concentrations.

Estradiol↗

PubMedDate not supplied

TP53 mutations in human meningiomas.

Overexpression of p53 has been reported to play a role in the development of neoplasms of the central nervous system. Meningiomas are generally benign intracranial tumors originating from the meninges. Overexpression of the p53 protein in meningiomas and an association with histological type and recurrence has been reported. Mutation of the TP53 gene leads to a more stable p53 protein in quantities high enough for detection by immunohistochemistry. In the search for these mutations the core domain of the TP53 gene of meningiomas has been analyzed. Only a very low incidence of mutations was reported. The apparent discordance between overexpression of p53 protein and TP53 gene mutations may be explained by mutations located outside the core domain. This issue was addressed in the present study. All 11 exons of 17 meningiomas were analyzed for DNA alterations by PCR single-strand conformation polymorphism (PCR-SSCP) analysis with subsequent sequencing. PCR-SSCP analysis showed a various number of band shifts and nucleotide alterations, caused either by alterations in the flanking introns or common polymorphisms (codon 36 and 72). The allele frequencies of the polymorphisms found in this small population of tumors resemble the frequencies reported in the literature. In addition, three nucleotide changes located in introns 2, 3 and 7 were found in 11, 3 and 4, respectively, of 17 specimens. Based on this study and on reports by others we conclude that it is not very likely that TP53 mutations are involved in the etiology of meningiomas.

Adult↗