Overexpression of p21, cyclin E and decreased expression of p27 in DMBA (7, 12-dimethylbenzanthracene)-induced rat ovarian carcinogenesis

Calcium supplementation does not rescue the programmed adult bone deficits associated with perinatal growth restriction

Low birth weight and poor childhood growth program a variety of adult diseases including bone disorders such as osteoporosis. We have previously reported that offspring born small, as a result of uteroplacental insufficiency, have shorter femurs, lower bone mineral content and a bone strength deficit as adults. The aim of this study was to determine the effects of calcium supplementation from adolescence on growth restricted male and female offspring which have a programmed bone deficit. Bilateral uterine vessel ligation (Restricted) or sham surgery (Control) was performed on gestational day 18 in WKY rats to induce uteroplacental insufficiency and growth restriction. At 2 months pups were allocated to one of four diet groups: diet 1-constant normal calcium diet, diet 2-variable normal calcium diet, diet 3-constant high calcium diet, diet 4-variable high calcium diet. Diet groups 1 and 3 were fed their respective diets constantly for the duration of the study. In groups 2 and 4, rats were fed one diet for 5 days, followed by a switch to a low calcium diet for the next 5 days. At 6 months Dual Energy Xray Absorptiometry (DXA) and Peripheral Quantitative Computed Tomography (pQCT) were performed on the right femur. Bone turnover markers were measured at 4 months. Male and female Restricted offspring were born 14% lighter compared to Controls (p<0.05). At 6 months both male and female Restricted offspring remained smaller and had shorter femurs compared to Controls (p<0.05). Restricted males and females had reduced trabecular and cortical content compared to Controls, regardless of diet (p<0.05). Trabecular bone density was lower in Restricted females only (p<0.05). A constant high calcium diet increased cortical BMD in Restricted male and both female groups (p<0.05). Measures of bone geometry indicated that Restricted offspring have narrower bones with preservation of absolute cortical thickness (p<0.05). Importantly, the stress strain index of bone bending strength was lower in male and female Restricted offspring, regardless of diet by up to 9.0% and 7.8%, respectively. DXA results were similar to pQCT results. Being born small, due to uteroplacental insufficiency, programs reduced adult femur length, dimensions and stress strain index. Supplementation with a high calcium diet from adolescence can increase adult cortical bone density in low birth weight males and females, and normal weight females. This increase in bone density was not sufficient to rescue the bone dimension and strength deficits which were programmed in utero, suggesting that the early life environment is critical for bone programming.

Enhanced efficiency and specificity of ovarian cancer gene therapy in rats with a novel nonviral gene delivery system (GE7) via intraovarian artery perfusion approach

Transfer of the herpes simplex virus type I-thymidine kinase gene, followed by the administration of ganciclovir (HSV1-tk/GCV) into ovarian cancer-derived cell line either in vitro or transplanted into nude mice has been shown to provide a potential strategy for the gene therapy of ovarian cancer. We investigated the antitumor effects of HSV1-tk/GCV strategy with a chemically induced rat ovarian cancer model and a tumor-selective gene delivery by a novel nonviral gene delivery system (GE7) through the ovarian artery and tail vein. We demonstrated the expression of a reporter gene, beta-gal gene, as well as HSV1-tk gene in tumors and other organs, evaluated the overall antitumor effects after the GCV treatment and analyzed the tumor cell cycle phase distribution. Via the ovarian artery route, the expressions of beta-gal and HSV1-tk in tumors were significantly stronger than those expressed in such organs as the hearts, livers, spleens, lungs and kidneys. However, no beta-gal and HSV1-tk were detected in the tumor tissues when administrated via the tail vein, and little was found in other organs. The cell cycle analysis showed that the total S-phase of tumor cells in the test intra-arterial treatment group was considerably higher than that of the controls. The weight of the tumor tissues in the group treated by the intra-arterial route (4.06+/-2.12 g) was much less than the group treated intravenously (18.25+/-8.34 g) (P<.01). These findings indicated that the administration of GE7/HSV1-tk complex via the ovarian artery route could be a promising avenue of future human ovarian cancer treatment.

p27(Kip1) stabilization and G(1) arrest by 1,25-dihydroxyvitamin D(3) in ovarian cancer cells mediated through down-regulation of cyclin E/cyclin-dependent kinase 2 and Skp1-Cullin-F-box protein/Skp2 ubiquitin ligase

p27(Kip1) (p27) is a tumor suppressor whose stability is controlled by proteasome-mediated degradation, a process directed in part by cyclin-dependent kinase 2 (CDK2)-mediated phosphorylation of p27 at Thr(187) and its subsequent interaction with the Skp1-Cullin-F-box protein/Skp2 (Skp2) ubiquitin ligase. The present study shows that 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) arrests ovarian cancer cells in G(1) by stabilizing the p27 protein. 1,25(OH)(2)D(3) initiates a chain of events by decreasing the amounts of cyclin E and cyclin E-associated CDK2 activity. As a result, p27 phosphorylation at Thr(187) and consequently the interaction with Skp2 are decreased. 1,25(OH)(2)D(3) also increases p27 stability by decreasing the abundance of Skp2. It is the combined effect of 1,25(OH)(2)D(3) on both the CDK2-dependent phosphorylation of p27, and thus its affinity for Skp2, and Skp2 expression that dramatically increases the stability of the p27 protein. Similar to its effects in ovarian cancer cells, 1,25(OH)(2)D(3) induces p27 accumulation in wild type mouse embryo fibroblasts and arrests wild type but not p27-null mouse embryo fibroblasts in G(1). Stable expression of Skp2 in OVCAR3 cells diminishes the G(1) arrest and decreases the growth response to 1,25(OH)(2)D(3). Taken together, the results of this study identify p27 as the key mediator of 1,25(OH)(2)D(3)-induced growth suppression in G(1) and show that the hormone achieves this by decreasing the activity of CDK2 and reducing the abundance of Skp2, which act together to degrade p27.