Does VEGF facilitate local tumor growth and spread into the abdominal cavity by suppressing endothelial cell adhesion, thus increasing vascular peritoneal permeability followed by ascites production in ovarian cancer?

BACKGROUND: Ovarian cancer is mostly associated with pathologically regulated permeability of peritoneal vessels, leading to ascites. Here, we investigated the molecular regulation of endothelial permeability by the vascular endothelial growth factor (VEGF) and both tight and adherens junction proteins (VE-cadherin and claudin 5) with regards to the tumor biology of different ovarian cancer types. METHODS: Serum and ascites samples before and after surgery, as well as peritoneal biopsies of 68 ovarian cancer patients and 20 healthy controls were collected. In serum and ascites VEGF protein was measured by ELISA. In peritoneal biopsies co-localization of VE-cadherin and claudin 5 was investigated using immunohistochemical dual staining. In addition, the gene expression of VE-cadherin and claudin 5 was quantified by Real-time PCR. Differences in VEGF levels, VE-cadherin and claudin 5 gene expression were analyzed in relation to various tumor characteristics (tumor stage, grading, histological subtypes, resection status after surgery) and then compared to controls. Furthermore, human primary ovarian cancer cells were co-cultured with human umbilical vein endothelial cells (HUVEC) and changes in VE-cadherin and claudin 5 were investigated after VEGF inhibition. RESULTS: VEGF was significantly increased in tumor patients in comparison to controls and accumulates in ascites. The highest VEGF levels were found in patients diagnosed with advanced tumor stages, with tumors of poor differentiation, or in the group of solid / cystic-solid tumors. Patients with residual tumor after operation showed significantly higher levels of VEGF both before and after surgery as compared to tumor-free resected patients. Results of an immunohistochemical double-staining experiment indicated co-localization of VE-cadherin and claudin 5 in the peritoneal vasculature. Compared to controls, expression of VE-cadherin and claudin 5 was significantly suppressed in peritoneal vessels of tumor patients, but there were no significant differences regarding VE-cadherin and claudin 5 expression in relation to different tumor characteristics. A significant positive correlation was found between VE-cadherin and claudin 5 expression. VEGF inhibition in vitro was associated with significant increase in VE-cadherin and claudin 5. CONCLUSIONS: Our results indicate that increased peritoneal permeability in ovarian cancer is due to down-regulation of adhesion proteins via tumor derived VEGF. Advanced ovarian cancer with aggressive tumor biology may be associated with early dysregulation of vascular permeability leading to ascites. These patients may benefit from therapeutic VEGF inhibition.

Macrocyclic statine-based inhibitors of BACE-1.

Minimal sequence requirements for binding of substrate-derived statine peptides to the aspartyl enzyme were established on the basis of the X-ray cocrystal structure of the hydroxyethylene-octapeptide OM00-3 in complexation with BACE-1. With this information to hand, macrocyclic compounds that conformationally restrict and preorganize the peptide backbone for an entropically favoured binding to the enzyme active site cleft were designed. By means of a side chain-to-side chain ring closure between two aspartyl residues in the P2 and P3' positions through phenylene-1,3-dimethanamine, a 23-membered ring structure was obtained; this structure retained an extended conformation of the peptide backbone, including the transition state analogue statine for tight interactions with the two aspartyl residues of the active centre. The conformational preorganization of the inhibitor molecule was verified by NMR structural analysis and was then confirmed by the crystal structure of the BACE-1/inhibitor complex. Detailed insights into the binding mode of this macrocyclic inhibitor explained its moderate binding affinity in cell-free assays (K(i)=2.5 microM) and yielded precious information for possible structural optimization in view of the lack of steric clashes of the macrocycle with the flap domain of the enzyme.

Cooperative effect of adenoviral p53 gene therapy and standard chemotherapy in ovarian cancer cells independent of the endogenous p53 status.

Clinical adenoviral p53 gene therapy has been shown by us and others to inhibit tumor growth of ovarian cancer with endogenous mutant p53. This study was designed to test the cooperative antitumor effect of standard combination chemotherapy using paclitaxel and carboplatin together with adenoviral p53 gene transfer in the presence of wild-type and mutant p53. Seven ovarian cancer cell lines with mutant p53 and seven ovarian cancer cell lines with wild-type p53 were tested. An E1-deleted adenovirus type 5 expressing p53 (ACNp53) was used for p53 gene transfer. p53 gene transfer at 50% transduction efficiency significantly reduced IC50 of carboplatin chemotherapy up to 49-fold, of paclitaxel chemotherapy up to six-fold, and of paclitaxel/carboplatin chemotherapy up to 19-fold in the wild-type p53 cell line OV-MZ-5. Synergism between ACNp53 and chemotherapy calculated by median-effect analysis was found at low drug concentrations in all cell lines independent of the p53 mutational status. In conclusion, adenoviral p53 gene transfer significantly increased the sensitivity of ovarian tumor cells to paclitaxel, to carboplatin and/or to the combination of both.

p53 autoantibodies can be indicative of the development of breast cancer relapse.

BACKGROUND: Serum autoantibodies (AAb) against mutated p53 protein have been detected in patients with invasive breast cancer of all stages. The present pilot study was conducted to investigate the use of p53 AAb titers in monitoring patients with recurrent breast cancer. PATIENTS AND METHODS: Sequential sera of 24 patients with primary non-metastatic breast cancer were retrospectively ELISA-tested for the presence of p53 AAb before therapy and during the clinical follow-up until relapse. RESULTS: At the time of first diagnosis the prevalence of p53 AAb was 11 out of 24 (46%). In 7 out of 11 initially positive-tested patients, therapy was paralleled by decreasing p53 AAb titers. In four of these patients relapse was preceded by an increase of the titer. In 2 out of 11 patients, the titers remained positive throughout follow-up, possibly indicating a lack of therapy response. Two patients, who initially tested negative, seroconverted to p53 AAb positivity upon relapse. CONCLUSION: Monitoring of p53 AAb during follow-up can be informative about the clinical course of the disease. The development of breast cancer relapse can be preceded by an increase of p53 AAb titer.