||Ovarian carcinoma has poor prognosis with a high mortality rate in gynecologic malignancy. The epithelial ovarian cancers account for 90% of ovarian malignancy. They have been considered arising from the surface epithelium covering the ovary. The major types of epithelial ovarian cancers include serous, endometrioid, mucinous and clear cell carcinomas. |
DLK-1(Delta-Like 1 Homolog) is a transmembranous and secreted protein belonging to the epidermal growth factor-like homeotic family. Although expressed widely during embryonic development, only few types of tissue retain DLK-1 expression in adults. DLK-1 plays important roles in regulating cell differentiation, such as adipogenesis and osteogenesis. Aberrant expression of DLK1 has been found in various types of human cancers, including neuroblastoma, hepatocellular carcinoma, glioma and prostate cancer, but its expression in ovarian cancer has not yet been studied.CD44 is known as a stem cell marker. Previous studies showed that CD44 expressed higher level in ovarian cancer tissues and has been identified as a biomarker of ovarian carcinoma. Vimentin is a type III intermediate filament protein that is widely expressed in mesenchymal tissue, and is considered an important marker for epithelial-mesenchymal transition (EMT). E-cadherin is widely expressed in epithelial cells and acts as a pivotal tumor suppressor. Loss of E-cadherin expression has been known to be involved in epithelial-mesenchymal transition.
This study was aimed to discover the significance of DLK-1 expression and its correlation with tumor stemness and EMT in various types of epithelial ovarian cancer. The expression of DLK-1, CD44, vimentin and E-cadherin were analyzed in 283 ovarian carcinomas by immunohistochemistry on tissue microarray. The result showed positive correlation among DLK-1, CD44 and Vimentin expressions (P ＜ 0.01). Although there was no statistical significance (P ＝ 0.237), a reversed correlation was noted between the expressions of DLK-1 and E-cadherin in ovarian carcinomas. Our study revealed that DLK-1 is overexpressed in epithelial ovarian cancers, especially in endometrioid carcinoma.
In summary, DLK-1 may correlate with EMT and tumor stemness of ovarian carcinoma. Further study is needed to assess the potential use of DLK-1 for therapeutic strategy and prognosis evaluation.