Glucose-Regulated Protein 78 Is a Potential Serum and Imaging Marker for Early Detection of Ovarian Cancer

SIMPLE SUMMARY: Ovarian cancer (OVCA) is a fatal gynecological disease for which there is no early detection test. Glucose-regulated protein 78 (GRP78), a protein marker of stress, increases during chronic stress. Chronic stress has been suggested as a hallmark of cancer development. This study examined whether expression of GRP78 is associated with development of OVCA and whether GRP78 can predict OVCA at early stage. This study found GRP78 expression and its secretion in blood increased during OVCA development and progression. This study also developed a GRP78-targeted ultrasound scanning agent that detected ovarian tumors at early stages. Thus, a woman with high levels of GRP78 in her blood may be referred to have targeted-ultrasound scanning for confirming if she has ovarian tumors. These results will be a foundation for a clinical study to examine the feasibility of GRP78 as a potential marker of blood and ultrasound scanning for early detection of OVCA. ABSTRACT: Background: Understanding malignant transformation associated with ovarian cancer (OVCA) is important to establish early detection tests. This study examined whether expression of glucose-regulated protein 78 (GRP78, marker of cellular stress) increases during OVCA development, and whether GRP78 can be detected by targeted-transvaginal ultrasound (TVUS) imaging. Methods: Normal ovaries (n = 10), benign (n = 10) and malignant ovarian tumors at early (n = 8) and late stages (n = 16), hens with and without ovarian tumors at early and late stages (n = 10, each) were examined for GRP78 expression during OVCA development by immunohistochemistry, immunoblotting, gene expression and immunoassay. Feasibility of GRP78-targeted TVUS imaging in detecting early OVCA was examined. Results: Compared with normal ovaries and benign tumors, intensity of GRP78 expression was higher (p < 0.0001) in OVCA patients. Compared with normal (9007.76 ± 816.54 pg/mL), serum GRP78 levels were significantly higher (p < 0.05) in patients with early (12,730.59 ± 817.35 pg/mL) and late-stage OVCA (13,930.12 ± 202.35) (p < 0.01). Compared with normal (222.62 ± 181.69 pg/mL), serum GRP78 levels increased (p < 0.05) in hens with early (590.19 ± 198.18 pg/mL) and late-stage OVCA (1261.38 ± 372.85) (p < 0.01). Compared with non-targeted, GRP78-targeted imaging enhanced signal intensity of TVUS (p < 0.0001). Conclusions: Tissue and serum levels of GRP78 increase in association with OVCA. GRP78 offers a potential serum and imaging marker for early OVCA detection.