Role of cancer stem cells in ovarian carcinogenesis

Ovarian cancer (OC) is an aggressive malignant tumor (MT) with a relapsing course and a low 5-year survival rate. Most cases are diagnosed at advanced stages, while treatment options for OC are limited. Thus, the development of primary or secondary resistance to standard chemotherapy is often fatal for patients. MT heterogeneity contributes to the survival of the most adapted cells during the selection; such cells need high tumorigenicity in the site of a disease for further expansion of the surviving clone and fixation of a stable phenotype in the focus. Cancer stem cells (CSCs) combine these characteristics and are at the top of the hierarchical tumor structure. Their biological properties, such as the ability to self-renewal, and multilinear differentiation, are similar to those of normal human stem cells. Phenotypic plasticity and interaction with other parenchyma components, tumor stroma, and extra-tumor elements allow CSCs to withstand unfavorable conditions, such as chemotherapy, immunological surveillance, physical damaging factors and anoikis in the blood and lymphatic bed, and unusual microenvironment of targeted metastasis organs in the case of distant metastasis. More and more research articles are devoted to finding ways to use CSCs as a predictive and prognostic biomarker and as a target for therapy. However, unambiguous identification of CSCs, their counting, and specific elimination are a difficult problem. Currently, science is at the stage of accumulating data on this topic. The review summarizes current advances in understanding CSC biology and their impact on OC clinical progression. The literature search was carried out in PubMed, Google Scholar, and eLibrary databases.