http://repub.eur.nl/res/aut/6128/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/10130/ 2003-01-01T00:00:00Z Tibolone, a synthetic steroid acting in a tissue-specific manner and used in hormone replacement therapy, is converted into three active metabolites: a Delta(4) isomer (exerting progestogenic and androgenic effects) and two hydroxy metabolites, 3 alpha-hydroxytibolone (3 alpha-OH-tibolone) and 3beta-OH-tibolone (exerting estrogenic effects). In the present study an endometrial carcinoma cell line (Ishikawa PRAB-36) was used to investigate the progestogenic properties of tibolone and its metabolites. This cell line contains progesterone receptors A and B, but lacks estrogen and androgen receptors. When tibolone was added to the cells, complete conversion into the progestogenic/androgenic Delta(4) isomer was observed within 6 d. Furthermore, when cells were cultured with tibolone or when the Delta(4) isomer or the established progestagen medroxyprogesterone acetate was added to the medium, marked inhibition of growth was observed. Interestingly, 3 beta-OH-tibolone also induces some inhibition of growth. These growth inhibitions were not observed in progesterone receptor-negative parental Ishikawa cells, and progestagen-induced growth inhibition of PRAB-36 cells could readily be reversed using the antiprogestagen Org-31489. Upon measuring the expression of two progesterone-regulated genes (fibronectin and IGF-binding protein-3), tibolone, the Delta(4) isomer and medroxyprogesterone acetate showed similar gene expression regulation. These results indicate that tibolone, the Delta(4) metabolite, and to some extent 3 beta-OH-tibolone exert progestogenic effects. Tibolone and most likely 3 beta-OH-tibolone are converted into the Delta(4) metabolite. http://repub.eur.nl/res/pub/10230/ 2003-01-01T00:00:00Z PURPOSE: In endometrial cancer, loss of progesterone receptors (PR) is associated with more advanced disease. This study aimed to investigate the mechanism of action of progesterone and the loss of its receptors (PRA and PRB) in development of endometrial cancer. EXPERIMENTAL DESIGN: A 9600-cDNA microarray analysis was performed to study regulation of gene expression in the human endometrial cancer subcell line Ishikawa PRAB-36 by the progestagen medroxy progesterone acetate (MPA). Five MPA-regulated genes were selected for additional investigation. Expression of these genes was studied by Northern blot and by immunohistochemistry in Ishikawa subcell lines expressing different PR isoforms. Additionally, endometrial cancer tissue samples were immunohistochemically stained to study the in vivo protein expression of the selected genes. RESULTS: In the PRAB-36 cell line, MPA was found to regulate the expression of a number of invasion- and metastasis-related genes. On additional investigation of five of these genes (CD44, CSPG/Versican, Tenascin-C, Fibronectin-1, and Integrin-beta 1), it was observed that expression and progesterone regulation of expression of these genes varied in subcell lines expressing different PR isoforms. Furthermore, in advanced endometrial cancer, it was shown that loss of expression of both PR and E-cadherin was associated with increased expression CD44 and CSPG/Versican. CONCLUSION: The present study shows that progestagens exert a modulatory effect on the expression of genes involved in tumor cell invasion. As a consequence, loss of PR expression in human endometrial cancer may lead to development of a more invasive phenotype of the respective tumor. http://repub.eur.nl/res/pub/31987/ 2002-10-16T00:00:00Z The first observations indicative of a role of genetic factors in carcinogenesis were made as early as 1912, when Rous demonstrated that a filterable agent (i.e. virus) could induce cancer in chicken (Rous 1965). In 1914, Boveri postulated a "genetic" theory on carcinogenesis by hypothesizing that the development of malignant tumor cells is caused by either the predominance of chromosomes which promote cell division, or by the elimination of chromosomes which inhibit cell division (Boveri, 1914). In the last decade, research techniques in molecular biology have advanced rapidly. As a result, biological science has recently made huge steps forward in understanding the human genome. The disclosure of the human genome seems imminent, as, in February 2001, two research groups (the Human Genome Project (HGP) and Celera Genomics) published their draft sequences of the near complete human genome (Lander, Linton et al. 2001; Venter, Adams et al. 2001). With the knowledge of the human genome sequence and new molecular research techniques it is now possible to monitor gene expression levels on a genomic scale. These new data promise to enhance the fundamental understanding of life at the molecular level. As, in general, genetic alterations are thought to play a major role in tumor development and tumor progression ((Fearon and Vogel stein 1990); (Knudson 1993)), knowledge of molecular genetics seems essential in understanding the etiology and the biological behavior of cancer.