TLR2 and TLR4 Exhibit Distinct Regulation of Cancer Cell Stemness Mediated by Cell Death-Induced HMGB1

Summary: The high-mobility group box 1 protein (HMGB1), a chromatin associated nuclear protein and extracellular damage associated molecular pattern molecule, are overexpressed in several solid tumors including pancreatic carcinoma. We previously observed radiotherapy induced dying cells to secrete HMGB1 and accelerate pancreatic carcinoma progression, with mechanism remaining elusive. In this study, we show for the first time that radiation-associated dying cell derived HMGB1 maintained the pancreatic cancer cell stemness and contribute to the self-renewal of CD133 cancer stem cells in vitro and in vivo. Using overexpressing and silencing experiments, we demonstrate that the process is activated by TLR2 receptor, whereas TLR4 receptor displays antagonistic effect on HMGB1-TLR2 signals. Furthermore, Wnt/β- catenin signaling is involved in HMGB1-TLR2 mediated stemness of CD133 cancer cells. Our results provide new information how irradiation-induced cell death might enhance stemness of resident cancer cells, and indicates HMGB1-TLR2 signaling as a potential therapy target for preventing pancreatic cancer recurrence.Funding Statement: This study was supported by grants from the National Natural Science Foundation of China (Grant no.81502663), the Social Development Foundation of Jiangsu Province (Grant no. BE2018691), Young medical talents of Jiangsu (QNRC2016831, QNRC2016833, QNRC2016839), Jinshan talent project of Zhenjiang City, the Social Development Foundation of Zhenjiang City (SH2017027).Declaration of Interests: The authors declare no conflict of interests.Ethics Approval Statement: Animal studies were approved by the Committee on the Use of Live Animals for Teaching and Research of the Jiangsu University.