Liver cancer stem cells (LCSCs) are derived from damaged and transformed hepatic progenitor cells (HPCs) during precancerous cirrhosis stage. Ras/Raf/MAPK and PI3K/AKT/mTOR signaling pathways are significantly deregulated in liver cancer. The activation of PI3K/AKT/mTOR pathway in LCSC population is one of the reasons for acquired resistance to sorafenib in advanced hepatocellular carcinoma (HCC) patients. Therefore, identifying novel inhibitors targeting this pathway acting on LCSCs is highly essential. We, therefore, elucidated the bioactivities of small-molecule kinase inhibitors on LCSCs acting through PI3K/Akt/mTOR pathway in comparison with DAPT (CSC inhibitor), DNA intercalators and sorafenib. For this purpose, CD133+/EpCAM+ cells originated from HCC cells were analyzed by flow cytometry and effective inhibitors on LCSCs were further tested for their potential combinatorial effects. Treatment of cells with sorafenib and DNA intercalators resulted in enrichment of CD133+/EpCAM+ cells. Yet, rapamycin, LY294002 and DAPT significantly reduced CD133/EpCAM positivity. Combination studies revealed that sequential treatment strategy decreased the ratio of LCSCs as opposed to sorafenib treatment alone. The effects of the inhibitors were also demonstrated with LCSC sphere formation. Additionally, a large panel of genes involved in cancer pathways was analyzed using Nanostring® nCounter® Technology to identify the differentially expressed genes in rapamycin, sorafenib or DAPT treated cells. Systematic pathway analysis using Cytoscape ScoreFlow algorithm application allowed us to identify differential response genes involved in stemness. While the stemness genes were downregulated in cells treated with rapamycin or DAPT, JAG1 gene was found to be upregulated in sorafenib-treated cells. Interleukin 8 (IL-8) was downregulated upon treatment with DAPT, yet upregulated upon sorafenib treatment. Following IL-8 inhibition with repaxirin, CD133/EpCAM positivity of cells decreased significantly, indicating that IL-8 signaling is crucial for the conservation of stemness features of cancer cells. The combination of sorafenib and reparixin resulted in lower levels of SOX2 and Nanog proteins. Conclusion: PI3K/Akt/mTOR pathway inhibitors alter hepatic CSC composition and gene expression in favor or to the detriment of cancer stem cell survival. Blockade of IL-8 signaling provides a promising therapeutic approach for prevention of LCSC enrichment.

Citation Format: Deniz C. Kahraman, Tamer Kahraman, Rengul Cetin Atalay. Differential alteration of IL-8 in liver cancer stem cell enrichment in response to PI3K/Akt/mTOR inhibitors and sorafenib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3937.

©2018 American Association for Cancer Research.
2018
American Association for Cancer Research.