ANALYSIS OF SIGNAL TRANSDUCTION PATHWAYS THAT MEDIATE RESISTANCE OF LIVER CANCER STEM CELLS TO SORAFENIB

Peng Liu^{1, 2, 3 ,#}, Yongwei Chen^{1, 2, 3, #}, Che Liu^{1, 2, 3}, Yintao Wu^{1, 2, 3}, Congyong Li⁴, Xuefei Huang⁴, Chunyan Zhang^{4, *}

¹Faculty of Hepato-Pancreato-Biliary Surgery, Chinese PLA General Hospital. 28 Fuxing Road, Beijing 100853, China - ²Institute of Hepatobiliary Surgery of Chinese PLA. Chinese PLA General Hospital. 28 Fuxing Road, Beijing 100853, China - ³Key Laboratory of Digital Hepatobiliary Surgery, Institute of Hepatobiliary Surgery of Chinese PLA. 28 Fuxing Road, Beijing 100853, China - ⁴The sixth section of health care department, The Second Medical Center & National Clinical Research Center for Geriatric Diseases, Chinese PLA General Hospital, 6 Fucheng Road, Beijing 100048, China

Background: The aim of the present study was to compare the difference in drug resistance between CSCs and their original hepatocellular carcinoma (HCC) cells by analyzing the expression of genes and activity of signaling pathways associated with drug resistance, in an attempt to identify specific molecules involved in sorafenib resistance.

Methods: Cell cycle and apoptosis analyses were performed with flow cytometry. The sensitivity of the cell lines to chemotherapeutic drugs was measured using the cell counting Kit-8. RNA-Seq is used to identify differentially expressed genes between Human cancer cell lines and CSCs. RT-PCR and Immunofluorescence analysis are used to analyze candidate genes that were associated with sorafenib resistance of liver CSCs. Finally, the signal transduction pathways associated with sorafenib resistance were detected by western blotting

Results: CSC cell lines are more resistant to sorafenib than their original HCC cells. After Sorafenib treatment, the number of G1-phase liver cancer cells increased significantly, indicating that sorafenib can stop the cell cycle. The MAPK pathway is susceptible to sorafenib treatment in liver cancer cells, and the expression of ERK1/2 is decreased as a response to increasing concentrations of sorafenib administration. Among genes associated with sorafenib resistance, PDGFRB is specifically downregulated in liver CSCs. Moreover, the MAPK pathway inhibitor U0126 combined with sorafenib can effectively inhibit the viability of liver CSCs and increase their sensitivity to sorafenib.

Conclusions: These findings may serve as a theoretical basis for developing liver CSC-targeted therapies for sorafenib-resistant HCC to improve the clinical outcome of patients with advanced HCC.