| Research Abstract |
Proliferation and metastatic behavior of cancer are clearly associated with over-expression of the junctional protein ezrin and ezrin is necessary for in vitro invasive behavior of estrogen-sensitive endometrial cancer cells. In this study, we tested the effect and mechanism of action of 17β-estradiol (E_2) and Selective Estrogen Receptor Modulators (SERMs) on ovarian cancer (OVCA) cell motility, invasive behavior and cell growth and correlated the effects with the expression of ezrin. Following 24 hr in serum-free medium, OVCA cell lines SKOV3 (estrogen receptor (ERα>β-positive), and DOV13 (ERβ>α-positive) were treated with E_2 or tamoxifen (TMX) or raloxifene (RLX) alone or in combination during incubation on Matrigel membranes for 3-24 hr. The number of cells that penetrated the membrane were counted and the cells immunostained for ezrin. In separate studies the effects of E_2 on cell number, ezrin expression (Western blots) and cFOS were determined. E_2 stimulation of ezrin express
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ion, OVCA cell proliferation, motility and Matrigel penetration was apparent by 3 hrs and lasted for 24 hrs. the SKOV3 cells' response was 〜two-fold that of DOV13 cells. There was development of an invasive phenotype (ruffles and processes capped by pseudopodia) and translocation of heavy ezrin staining to cell edges, especially in the bases of the pseudopodia and ruffles. Although on their own TMX and RLX had agonistic effects, adding them to E_2 blocked ezrin over-expression and invasive behavior. The correlation between immuno-reactive ezrin expression with E_2 was highly statistically significant (R=0.86), while there was no correlation between ezrin in untreated controls and incubations combining E_2 and TMX or RLX (R<0.50). Since the ezrin over-expression was demonstrable by 3h we measured cFos and showed it to also be elevated from 3-24 hrs.
Platinum based multi-drug chemotherapy is the first choice for advanced ovarian, endometrial and cervical cancers either in adjuvant or neo-adjuvant settings. These treatments have been shown to increase progression but no significant prolongation of survival was achieved yet. Eventually, patients with advanced stage diseases would develop chemo-resistance and may succumb to the disease. Therefore control of the recurrence by suppressing the development of chemo-resistance is the most important pathways towards the successful disease control. Several factors contributing to the development of chemo-resistance have been shown. Aneuploidity, expression of MDR genes, expression of Gestapo and excisional repair genes have been shown to confer chemo-resistant phenotypes. In our recent study, we have mapped gene expression in cis-platinum sensitive cell line as well as in the resistant sub-clone using gene array analysis. The study showed clear difference in GSTpi expression in the resistant cells but the mechanism is not known. One of the potential pathways to induce GSTpi expression may involve steroid and xenobiotic receptors (SXR), which have been implicated as a controlling system of GSTpi expression. However, the SXR and GSTpi relationship with chemo-resistant phenotype in endometrial cancers is not known. Thus, we attempted to study control mechanisms of the SXR-GSTpi expression in endometrial cancers. Less
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