Browsing by Author "Azbazdar, Yagmur"

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Citation - WoS: 44
Citation - Scopus: 48
Changes in Wnt and Tgf-Beta Signaling Mediate the Development of Regorafenib Resistance in Hepatocellular Carcinoma Cell Line Huh7
(Frontiers Media Sa, 2021) Karabiçici, Mustafa; Azbazdar, Yagmur; Ozhan, Gunes; Senturk, Serif; Firtina Karagonlar, Zeynep; Erdal, Esra
Hepatocellular carcinoma (HCC) is an aggressive, chemo resistant neoplasm with poor prognosis and limited treatment options. Exploring activated pathways upon drug treatment can be used to discover more effective anticancer agents to overcome therapy resistance and enhance therapeutic outcomes for patients with advanced HCC. Human tumor-derived cell lines recapitulate HCC diversity and are widely used for studying mechanisms that drive drug resistance in HCC. In this study, we show that regorafenib treatment activates Wnt/beta-catenin signaling only in hepatoblast-like HCC cell lines and induces enrichment of markers associated with hepatic stem/progenitor cells. Moreover, activation of Wnt/beta-catenin signaling via Wnt3a/R-Spo1 treatment protects these cells from regorafenib induced apoptosis. On the other hand, regorafenib resistant cells established by long-term regorafenib treatment demonstrate diminished Wnt/beta-catenin signaling activity while TGF-beta signaling activity of these cells is significantly enhanced. Regorafenib resistant cells (RRCs) also show increased expression of several mesenchymal genes along with an induction of CD24 and CD133 cancer stem cell markers. Moreover, regorafenib resistant cells also exhibit significantly augmented in vitro and in vivo migration capacity which could be reversed by TGF-beta type 1 receptor (TGFb -R1) inhibition. When combined with regorafenib treatment, TGF beta-R1 inhibition also significantly decreased colony formation ability and augmented cell death in resistant spheroids. Importantly, when we knocked down TGF beta-R1 using a lentiviral plasmid, regorafenib resistant cells entered senescence indicating that this pathway is important for their survival. Treatment of RRCs with TGF beta-R1 inhibitor and regorafenib significantly abolished pSTAT3, pSMAD2 and pERK (44/42) expression suggesting the involvement of both canonical and non-canonical pathways. In conclusion, our data suggest that HCC tumors with aberrant activation in the Wnt/beta-catenin pathway, might have higher intrinsic regorafenib resistance and the inhibition of this pathway along with regorafenib administration might increase regorafenib-induced cell death in combinational therapies. However, to resolve acquired regorafenib resistance developed in HCC patients, the combined use of TGF-beta pathway inhibitors and Regorafenib constitute a promising approach that can increase regorafenib sensitization and prevent tumor recurrence.
Citation - WoS: 24
Citation - Scopus: 22
Lgr5/R-spo1 Axis Promotes Stemness and Aggressive Phenotype in Hepatoblast-Like Hepatocellular Carcinoma Cell Lines
(Elsevier Science Inc, 2021) Akbari, Soheil; Kunter, Imge; Azbazdar, Yagmur; Ozhan, Gunes; Atabey, Nese; Karagonlar, Zeynep Firtina; Erdal, Esra
Leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) is a newly defined stem cell marker in endoderm-derived organs such as the small intestine, colon and pancreas. Recently, LGR5 was demonstrated to be an important factor in liver regeneration and stem cell maintenance. Moreover, LGR5 expression is highly upregulated in various cancers including hepatocellular carcinoma. Herein, we demonstrate that LGR5 expression is specifically observed in certain subset of HCC cell lines with ?hepatoblast-like? appearance, characterized by the expression of liver fetal/progenitor markers. Notably, the activation of the canonical Wnt pathway significantly increases the expression of LGR5 in this subset of cell lines, whereas it does not cause any induction of LGR5 expression in mesenchymal like cell lines SNU-475 and SNU-449. Furthermore, we showed that treatment of the hepatoblast-like HCC cell lines HuH-7 and Hep3B with LGR5 ligand R-Spo1 significantly amplifies the induction of LGR5 expression, the phosphorylation of LRP6 and ?-catenin resulting in enhanced TCF/LEF activity either alone or in combination with Wnt3a. Consistently, the silencing of the LGR5 gene attenuates the co-stimulatory effect of R-Spo1/Wnt3a on TCF/LEF activity while overexpression of LGR5 enhances it. On the contrary, overexpression of LGR5 does not change TCF/LEF activity induced by R-Spo1/Wnt3a in mesenchymal-like HCC line, SNU-449. Importantly, LGR5-overexpressing cells have increased expression of several Wnt target genes and stemness-related genes including EpCAM and CK19 upon R-Spo1/Wnt3a treatment. LGR5-overexpressing cells also have increased spheroid forming, migration and invasion abilities and stimulation with R-Spo1/Wnt3a augments these abilities of LGR5-overexpressing cells. In addition, ectopic overexpression of LGR5 significantly increases cell proliferation rate independent of R-Spo1/Wnt3a stimulation. Moreover, in vitro tubulogenesis assay demonstrates that treatment with R-Spo1/Wnt3a enhances the sprouting of capillary tubules in only LGR5overexpressing cells. Finally, R-Spo1/Wnt3a significantly promotes dissemination of LGR5-overexpressing cells in vivo in a zebrafish xenograft model. Our study unravels a tumor-promoting role for LGR5 through activation of canonical Wnt/?-catenin signaling in the hepatoblast-like HCCs. In conclusion, our results suggest that LGR5/RSpo1/Wnt3a generates an axis that mediates the acquisition of aggressive phenotype specifically in hepatoblastlike subset of HCCs and might represent a valuable target for treatment of HCC tumors with aberrant activation of Wnt/?-catenin pathway.