Background: The lack of an effective early detection test makes ovarian cancer (OVCA) a fatal malignancy of women. Changes in cellular metabolic processes during ovarian malignant transformation lead to the endoplasmic reticular (ER) and mitochondrial stress. Glucose-regulated protein of 78kDa (GRP78) is a marker of ER stress. Tumor-associated ER stress causes relocalization of GRP78 from ER to cell surface with an increase in its serum levels. Secreted GRP78 also stimulates tumor associated neoangiogenesis (TAN). Vascular endothelial growth factor receptor-2 (VEGFR-2) is a marker of ovarian TAN. Thus GRP78 represents a marker of ovarian malignant transformation and in association with VEGFR-2 may constitute an early detection test for OVCA. However, information on OVCA related changes in GRP78 expression and its association with ovarian TAN is unknown.
Objectives: The goals of this study were to examine (i) whether GRP78 expression increases during malignant changes in the ovary and (ii) whether the frequency of TAN vessels is associated with ovarian tumor-associated GRP78 expression at early stage of OVCA in the laying hen, a spontaneous model of human OVCA.
Materials and Methods: 3-4 years old White Leghorn laying hens with normal (n=25) or ovarian tumors (n=30) were selected by contrast enhanced transvaginal ultrasound scanning. Serum samples were collected, hens were euthanized, and ovarian tissues were processed for routine histology or immunohistochemistry (IHC) and protein extraction. Ovarian tumors were confirmed by gross morphology and microscopy. Expression of GRP78 by ovarian malignant cells and VEGFR-2 by TAN vessels was determined by IHC. IHC observations were confirmed by immunoproteomic studies.
Results: As compared with normal ovaries (n=25), the intensity of GRP78 expression was significantly (p<0.001) higher in hens with early stage OVCA (n=12) and increased further in hens with late stage OVCA (n=18) (p<0.05). GRP78 expression was higher in hens with serous OVCA followed by endometrioid OVCA and was least in hens with mucinous and clear cell OVCA irrespective of their stages of OVCA. A band of approximately 80kDa was observed for GRP78 in all ovaries examined and the patterns of expression were similar to that of IHC. The frequency of VEGFR-2 expressing TAN vessels was significantly (p<0.001) higher in OVCA hens than in normal hens. Increase in the frequency of VEGFR-2 expressing TAN vessels was positively correlated with the intensity of GRP78 expression.
Conclusion: The results of this study suggest that increase in the GRP78 expression is associated with ovarian malignant transformation, and this enhanced expression may stimulate ovarian tumor-associated neoangiogenesis. Thus GRP78 in combination with VEGFR-2 may constitute an early detection test for OVCA. These results will constitute a foundation for a clinical study to establish an early detection test for OVCA. Support: DOD Award # W81XWH-11-1-0510.
Citation Format: Doungkamol Alongkronrusmee, Pincas Bitterman, Jacques S. Abramowicz, Janice M. Bahr, Sanjib Basu, Salvatore Grasso, Sameer Sharma, Jacob Rotmensch, Animesh Barua. GRP78 in association with VEGFR-2 detects early stage ovarian cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4642. doi:10.1158/1538-7445.AM2013-4642