Abstract 3193: Valosin containing protein (VCP) is a potential novel serum marker for ovarian cancer

Abstract

Abstract The measurement of various serum markers (estradiol, inhibin, MIS) is often performed as an ancillary diagnostic technique for ovarian granulosa cell tumor (GCT), and is widely used for postoperative surveillance for disease recurrence. However, both the sensitivity and specificity of these markers has been repeatedly questioned, and a truly reliable serum marker for GCT has yet to be identified. We have recently developed the Ctnnb1tm1Mmt/+;Ptentm1Hwu/tm1Hwu;Amhr2tm3(cre)Bhr/+ (CPA) transgenic mouse model, which features genetic modifications that mimic pathologically relevant genetic lesions and signaling processes that occur in GCT in women. CPA mice develop anaplastic, highly aggressive GCTs that can spread both by forming distant metastases and by seeding into the peritoneal cavity, which are the main modes of GCT dissemination in women. Due to the biological similarities between GCT in women and in CPA mice, we hypothesized that the CPA model could be used in a translational approach to identify novel serum markers for GCT. To test this, granulosa cells from control mice and GCT cells from CPA mice were placed in culture, and differential secretion or shedding of proteins into the culture supernatant was analyzed by SDSPAGE and silver staining. Proteins bands present in the experimental samples but absent (or present at much lower levels) in control media were isolated from the gels and identified by tryptic digestion followed by LC/MS/MS analyses. By this method, VCL, VCP, HSPA4, HSP90A, HSP70, SPARC, WIF1, CTSB, FAM3C, TIMP2, CFL2 and B2M were found to be selectively secreted/shed by CPA GCT cells. An in vivo validation step was then performed to determined if these proteins were overexpressed in the serum of CPA mice relative to controls. Western blotting showed that CPA mice had elevated (P<0.05) serum levels of VCP, HSP4, CTSB, TIMP2 and B2M. The latter proteins were therefore tested as potential serum diagnostic markers for GCT in a small cohort of women with GCT (n=10) and healthy women (n=7), as well as in patients with ovarian epithelial carcinomas (n=8) to provide an initial assessment of marker specificity. Of the proteins tested, mean serum levels of Valosin Containing Protein (VCP) were found to be over 9-fold higher in women with GCT or ovarian carcinoma relative to healthy women (P<0.01) by western blotting. Furthermore, 90% of women with GCT and 100% of women with ovarian carcinomas had serum VCP levels above the highest level measured in the reference group. While these results indicate that VCP is unlikely to serve as a GCT-specific serum marker, it may nonetheless provide a valuable tool for the diagnosis of ovarian cancer. Analyses of larger cohorts will be required to determine the sensitivity, specificity and predictive values of VCP measurement for various forms and stages of ovarian cancer, as well as to determine if non-ovarian cancers also affect serum VCP levels. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3193. doi:10.1158/1538-7445.AM2011-3193