Changes in Nucleolin Expression during Malignant Transformation Leading to Ovarian High-Grade Serous Carcinoma

Simple Summary Ovarian cancer (OVCA) is one of the most fatal gynecologic malignancies with most cases detected in late stages. High mortality rates are due, in part, to the lack of an effective early detection test. Tumor development and progression are associated with an increase in the expression of tissue proteins and/or their release into circulation. These proteins may offer potential markers for the early detection of OVCA. Nucleolin, a nuclear protein, is one such marker. This pilot study examined whether the tissue expression of nucleolin and its serum levels change in association with OVCA development and progression by using archived clinical samples and the laying hen model of spontaneous OVCA. Nucleolin was found to be highly expressed in ovaries and fimbriae with tumors and in serum levels compared to those without OVCA. This study also found that tumor-associated serum levels of nucleolin increase even before the tumor forms a detectable solid mass in the ovary or fimbria, suggesting that nucleolin may be involved in malignant transformation. A smaller sample size is a limitation of this study; however, it will lay the foundation for clinical studies with larger cohorts to examine the efficacy of nucleolin as a potential serum marker for the early detection of OVCA. Objective: Ovarian high-grade serous carcinoma (HGSC) is a fatal malignancy of women. Alterations in the expression of nuclear proteins are early steps in malignant transformation; nucleolin is one such protein. Changes in nucleolin expression and circulatory levels during ovarian HGSC development are unknown. The study goal was to determine if tissue and circulatory levels of nucleolin change in response to malignant transformation leading to ovarian HGSC. Methods: Sera, ovaries, and BRCA+ fimbria from healthy subjects, and sera and tumor tissues from patients (n = 10 each), and healthy hens and hens with HGSC were examined in exploratory and prospective studies for nucleolin expression by immunohistochemistry, immunoblotting, gene expression, and immunoassay, and analyzed by analysis of variance (ANOVA). Results: Compared with normal, nucleolin expression was higher in patients and hens with ovarian HGSC and in women with a risk of HGSC (P < 0.05). Compared with normal (1400 + 105 pg/mL, n = 8), serum nucleolin levels were 1.5 and 1.7-fold higher in patients with early- (n = 5) and late-stage (n = 5) HGSC, respectively. Additionally, serum nucleolin levels increased significantly (P < 0.05) prior to the formation of detectable masses. Conclusion: This pilot study concluded that tissue and serum levels of nucleolin increase in association with malignant changes in ovaries and fimbriae leading to ovarian HGSC.