Ovarian cancers metastasize by attaching to and invading through the mesothelium, a single layer of mesothelial cells lining the peritoneal cavity. The presence of invasive peritoneal metastases is associated with a poor prognosis for ovarian cancer (5-year survival <25%). Vascular cell adhesion molecule-1 (VCAM-1) is a cell surface receptor that mediates leukocyte attachment and extravasation across endothelial and mesothelial monolayers at sites of inflammation. Membranous VCAM-1 expression was observed on the mesothelium of 13 of 14 women with ovarian cancer compared with 6 of 15 who were cancer-free. Using a cell culture model system of mesothelial invasion, highly tumorigenic SKOV-3 and ES-2 cells were 2.5 to 3 times more efficient in transmigration through the mesothelial monolayer compared with poorly tumorigenic OVCAR-3 cells. Blocking antibodies to, or small interfering RNA knockdown of, VCAM-1 or its ligand A 4 B 1 integrin significantly decreased, but did not completely inhibit, transmigration of SKOV-3 cells through mesothelial monolayers. Furthermore, using a mouse model of ovarian cancer metastasis, treatment with VCAM-1 function-blocking antibodies decreased tumor burden and increased survival. Together, these observations implicate VCAM-1-A 4 B 1 integrin interactions in the regulation of ovarian cancer cell mesothelial invasion and metastatic progression and offer the possibility of novel therapeutic targets.

The inability to successfully treat women with ovarian cancer is due in large part to the advanced stage of disease at diagnosis, the development of platinum resistance, and the lack of sensitive methods to monitor tumor progression and response to treatment. Vascular cell adhesion molecule-1 (VCAM-1) is expressed on the mesothelium of ovarian cancer patients. We investigated VCAM-1 expression as a marker of peritoneal metastasis and tumor response to platinum-based chemotherapy. Methods Peritoneal or omental biopsies obtained from women diagnosed with Stage I, Stage II or Stage III/IV ovarian cancer were evaluated by immunohistochemistry. The effects of carboplatin on mesothelial VCAM-1 expression were determined in cultured cells by Western blot. Radiolabeled VCAM-1-specific peptide imaging probes and single photon emission computed tomography (SPECT) were employed in a mouse model of ovarian cancer peritoneal metastasis to identify VCAM-1 as a viable imaging target. Results VCAM-1 expression correlated with tumor stage. All specimens from Stage I patients were negative, while 29% of Stage II patients and the 73% of Stage III/IV patients were positive. While the majority of women with advanced stage disease expressed VCAM-1, the incidence of expression was reduced among women who received neoadjuvant chemotherapy, suggesting a role for chemotherapy in regulating VCAM-1 expression. Treatment of mesothelial cells in culture with carboplatin resulted in a transient decrease in VCAM-1 expression 4 hours after treatment that returned to baseline within 16 to 24 hours. In vivo imaging of VCAM-1 also demonstrated an acute decrease in expression 4 hours after carboplatin administration that recovered within 48 hours in mice harboring platinum-resistant tumors. Chronic VCAM-1 expression reflected the effect of platinum-based treatment on tumor burden. Specifically, carboplatin treatment of mice with platinum-sensitive tumors showed reduced VCAM-1 expression, which correlated with reduced tumor burden; mice with platinum-resistant tumors retained elevated VCAM-1 expression and tumor burden following treatment. Conclusions Clinically relevant VCAM-1-specific imaging probes identify VCAM-1 expression as an indicator of ovarian cancer peritoneal metastasis and therapeutic response to platinum-based agents. These observations support testing the utility of VCAM-1 imaging probes to monitor treatment response in ovarian cancer patients, thus providing the potential to improve management of women with this disease.

The suprachiasmatic nucleus (SCN) is the dominant circadian pacemaker in mammals. To understand better the ontogeny of mouse SCN and the role of the pacemaker in peptide expression, the authors examined the distribution of cells that were immunoreactive for vasopressin (AVP) or vasoactive intestinal polypeptide (VIP) in wild type and Clock mutant mice at two developmental stages. Clock homozygous mice failed to show the dramatic increase in the number of VIP-immunoreactive (VIP-ir) neurons from postnatal day 6 (P6) to P30 that was found in the SCN of wild type mice. The number of AVP-ir neurons was relatively constant in the postnatal SCN but was significantly reduced in Clock/Clock mice. The effects of the Clock mutation varied with position in the SCN for both peptides. Densitometry of immunolabeled brains indicated that the Clock mutation reduced AVP expression specifically in the SCN and not in other brain areas. The SCN did not significantly change shape or size with age or Clock genotype. Taken together, these results indicate that the neonatal mouse SCN has its full complement of cells, some of which are not yet mature in their neuropeptide content. Furthermore, the observation that the Clock mutation appears to act on a subset of AVP and VIP cells suggests heterogeneity within these cell classes in the SCN.

Objective The inability to successfully treat women with ovarian cancer is due to the presence of metastatic disease at diagnosis and the development of platinum resistance. Ovarian cancer metastasizes throughout the peritoneal cavity by attaching to and invading through the mesothelium lining the peritoneum using a mechanism that involves α4β1 integrin and its ligand (vascular cell adhesion molecule) VCAM-1. Integrin α4β1 expression on tumor cells is known to confer protection from therapy in other cancers, notably multiple myeloma. We evaluated the role of α4β1 integrin in response to platinum-based therapy in a mouse model of peritoneal ovarian cancer metastasis by treatment with a humanized anti-α4β1 integrin function-blocking antibody. Methods Integrin α4β1 expression on primary human ovarian cancer cells, fallopian tube and ovarian surface epithelium and fresh tumor was assessed by flow-cytometry. The therapeutic impact of anti- α4β1 treatment was assessed in murine models of platinum-resistant peritoneal disease and in vitro using the platinum resistant ovarian cancer cell lines. Results Treatment of tumor-bearing mice with human-specific α4β1 integrin function-blocking antibodies, anti-VCAM-1 antibody or carboplatin alone had no effect on tumor burden compared to the IgG control group. However, the combined treatment of anti-α4β1 integrin or anti-VCAM-1 with carboplatin significantly reduced tumor burden. In vitro, the combination of carboplatin and anti-α4β1 integrin antibodies resulted in increased cell death and doubling time. Conclusions Our findings support a role for α4β1 integrin in regulating treatment response to carboplatin, implicating α4β1 integrin as a potential therapeutic target to influence platinum responsiveness in otherwise resistant disease.