Epithelial Ovarian Cancer Stem-Like Cells Are Resistant To The Cellular Lysis Of Cytokine-Induced Killer Cells Via Hif1a-Mediated Downregulation Of Icam-1

Epithelial ovarian cancer (EOC) is the most lethal of all gynecologic tumors. Cancer spheroid culture is a widely used model to study cancer stem cells. Previous studies have demonstrated the effectiveness of cytokine-induced killer (CIK) cell-based therapies against cancer and cancer stem cells. However, it is not clear how EOC spheroid cells respond to CIK-mediated cellular lysis, and the mechanisms involved have never been reported before. A flow cytometry-based method was used to evaluate the anti-cancer effects of CIK cells against adherent A2780 cells and A2780 spheroids. To demonstrate the association between hypoxia inducible factor-1 alpha (HIF1A) and intercellular adhesion molecule-1 (ICAM-1), two HIF1A short hairpin RNA (shRNA) stable transfected cell lines were established. Furthermore, the protein expression levels of hypoxia/HIF1A-associated signaling pathways were evaluated, including transforming growth factor-beta 1 (TGF-beta 1)/mothers against decapentaplegic homologs (SMADs) and nuclear factor-kappa B (NF-kappa B) signaling pathways, comparing A2780 adherent cells and cancer spheroids. Flow cytometry revealed that A2780 spheroid cells were more resistant to CIK-mediated cellular lysis, which was partially reversed by an anti-ICAM-1 antibody. HIF1A was significantly upregulated in A2780 spheroids compared with adherent cells. Using HIF1A shRNA stable transfected cell lines and cobalt chloride, it was revealed that hypoxia/HIF1A contributed to downregulation of ICAM-1 in A2780 spheroid cells and adherent cells. Furthermore, hypoxia/HIF1A-associated signaling pathways, TGF-beta 1/SMADs and NF-kappa B, were activated in A2780 spheroid cells by using western blotting. The findings indicate that EOC stem-like cells resist the CIK-mediated cellular lysis via HIF1A-mediated downregulation of ICAM-1, which may be instructive for optimizing and enhancing CIK-based therapies.