Nanog is highly expressed in ovarian serous cystadenocarcinoma and correlated with clinical stage and pathological grade.

Objective: Nanog is overexpressed in embryonic stem cells for cell self-renewal and differentiation. We investigated whether the Nanog expression is associated with the occurrence and development of ovarian cancer.

Methods: Immunohistochemistry was used to examine the expression of Nanog in 43 normal ovarian epithelia, 110 serous cystadenomas, 80 borderline serous cystadenomas, and 107 serous cystadenocarcinomas. In the meantime, their association with various clinicopathologic features was assessed.

Results: The expression intensity of Nanog in normal ovarian tissue, benign, borderline, and malignant tumors showed a gradual rising trend. Among the serous cystadenocarcinomas, 42.86% were detected to be positive for stage I, 70.97% for stage II, 95.31% for stage III, and 100% for stage IV. There was a strong correlation between Nanog and clinical stage (r = 0.418, p = 0.000). Besides, there was a 55.56% positive expression of grade I, 73.68% of grade II, and 96.67% of grade III. The correlation between Nanog and differentiation grade was dramatic (r = 0.692, p = 0.000).

Conclusions: Nanog was highly expressed in ovarian serous cystadenocarcinoma, and showed a positive correlation with clinical stage and grade. Nanog may play an important role in the development of dedifferentiation and progression of serous ovarian carcinoma.