Table 1.
The ovarian cancer stem cell markers and their features.
| Protein Names | Features | References |
|---|---|---|
| Cell surface markers of ovarian CSCs | ||
| CD44 | CD44 is the most common CSC marker in the ovary, breast, and pancreas. CD44+ cells have been found in primary, metastatic, and malignant ascites of ovarian carcinoma. | [29,33,34,35,36] |
| CD117 | CD117 has been known as c-kit. CD117 is a receptor tyrosine kinase related to survival, proliferation, migration, tumor progression, and stemness. CD117 is expressed in hematopoietic, mesenchymal, embryonic stem cells. CD117 is involved in stemness and chemoresistance in ovarian cancer. | [19,43,44,45] |
| CD24 | CD24 has been verified as a critical CSC marker in several cancers involving ovarian and colorectal cancers. CD24 is known as the regulation of proliferation, self-renewal, and chemoresistance in ovarian cancer. CD24 positive expressed ovarian cancer patients is poor survival. | [50,51,54,55,56,57] |
| CD133 | CD133 is a glycosylated transmembrane protein and associated with maintaining cancer stemness and tumor metastasis. CD133 has been identified as a prognostic marker in several cancers such as ovarian, glioblastoma, and prostate cancer. CD133 also is correlated with chemoresistance and poor prognosis in ovarian cancer. | [58,59,60,61,62,65] |
| CD166/ALCAM | CD166 is a transmembrane glycoprotein of the immunoglobulin superfamily. CD166 is overexpressed and is associated with a poor prognosis in various cancers. CD166 induced intracellular cancer stem markers such as OCT4, SOX2, and ALDH1A1. CD166 also is associated with maintaining CSC properties and chemoresistance. | [66,67,68,69,70,71,76] |
| Intracellular markers of ovarian CSCs | ||
| ALDH1 | ALDH1 is an enzyme to detoxify reactive aldehydes. ALDH composes three classes. ALDH1 consists of three isozymes; ALDH1A1 is predominantly a CSC marker. ALDH elevated stem-cell marker expression, self-renewal, proliferation, and differentiation potential. ALDH is also associated with invasion, drug resistance, and worse progression-free survival in ovarian cancer. | [78,79,80,81,82,83,84,85,86] |
| Autotaxin | Autotaxin possesses lysophospholipase D activity and produces lysophosphatidic acid (LPA). Autotaxin is expressed in several tissues, including body fluid, and it is highly expressed in the breast, glioblastoma, prostate, hepatocellular carcinoma, and melanoma. Autotaxin enhances migration, sphere formation, and cancer stemness markers. | [87,88,89,90,91,92,93,94,95] |
| Pluripotency-associated factors | OCT4, SOX2, and NANOG are the most common intracellular cancer stem markers in normal and cancer stem cells. Among these factors, SOX2 plays a more substantial role in early tumor initiation and tumor relapse in ovarian cancer, including breast, gastric, and lung. The knock-down SOX2 inhibits ovarian CSC survival and spheroid formation. | [12,97,98,101,102] |
| HIF-1α | Hif1a is one of the hypoxia-inducible factors and master regulators of hypoxia. Hif1a is correlated with growth, survival, and metastasis during hypoxia conditions. Hif1a can elevate the expression of pluripotent stem markers and plays an essential role in maintaining CSC properties. | [102,103,104,105,107] |