NF-κB Participates in the Stem Cell Phenotype of Ovarian Cancer Cells

Background. NF-kappa B is a transcription factor involved in cancer stem cells maintenance of many tumors. Little is known about the specific stem-associated upstream regulators of this pathway in ovarian cancer. The Aim of the study was to analyze the role of the canonical and non-canonical NF-kappa B pathways in stem cells of ovarian cancer cell lines. Methods. Stem cells were isolated using sorting cytometry. Western blot and RT-PCR were used to quantify protein and messenger RNA levels. Loss and gain of function assays were performed using siRNAs and dominant-negative proteins, respectively. NF-kappa B binding activity was measured with a reporter gene assay. The stem phenotype was estimated with clonogenic assays using soft agar, colony formation, ovospheres formation and in vivo tumorigenicity assays. Results. The CD44+ subpopulation of SKOV3 ovarian cancer cell line presented higher mRNA levels of key sternness genes, an increased tumorigenic capacity and higher expression of the RelA, RelB and IKK alpha. When the canonical pathway was inhibited by means of a dominant-negative version of IkB alpha, the stem cell population was reduced, as shown by a reduced CD44+ subpopulation, a decrease in the expression of the sternness genes and a reduction of the stem phenotype. In addition, IKK alpha, the main upstream non-canonical kinase, was highly expressed in the CSC population. Accordingly, when IKK alpha was inhibited using shRNAs, the expression of the sternness genes was reduced. Conclusions. This report is the first to show the importance of several elements of both NF-kappa B pathway in maintaining the ovarian cancer stem cell population. (C) 2017 IMSS. Published by Elsevier Inc.