Hepatic stellate cells (HSCs) activating HSF1-mediated COMP secretion promote liver metastasis of pancreatic cancer through CD36/AKT/FOXM1 signaling
Authors: L. Sun, Y. Wang, Q. Li, L. Wang, C. Wang, B. Yao, Z. Liu, T. Song, K. Tu, Q. Liu
Journal: Annals of Oncology (2018)

Introduction: Previous studies demonstrated that primary pancreatic cancer cells can release circulating factors or exosomes into the liver to form premetastatic niches. HSCs are important in forming premetastatic niches because they can transdifferentiate into the tumor-associated myofibroblasts, and then promote metastasis and growth of pancreatic cancer cells. The transcriptional regulator heat shock factor 1 (HSF1) is frequently activated in tumor stroma, and Cartilage oligomeric matrix protein (COMP) is a 524 kDa soluble glycoprotein particularly expressed in fibrotic conditions. However, the role of HSF1 and COMP in activated HSCs of premetastatic niches to facilitate metastasis and growth of pancreatic cancer remains to be elucidated. Methods: Elisa assay was used to detect expression of COMP in serums of pancreatic cancer patients with or without liver metastasis. Human primary HSCs and LX2 cells were activated by the conditioned medium (CMpcs) of pancreatic cancer cells (Panc-1) in vitro. The expression of HSF1, HSP90, HSP47, COMP in HSCs; CD36, p-AKT, AKT and Forkhead box M1 (FOXM1) in Panc-1 cells was determined by qRT-PCR, western blotting and immunofluorescence. CHIP-qPCR assay and dual-luciferase reporter system were used to explore the correlation between HSF1and COMP. The conditioned medium (CMhscs/lx2) of activated HSCs or LX2 was collected after treated with or without anti-COMP neutralizing antibody, KRIBB11 (an inhibitor of HSF1) or si-HSF1for 48 h, and indirect co-culture model was established to examine the effects of activated HSCs on the invasion and growth of pancreatic cancer cells. Intrasplenic tumor injection was used to establish a standard liver metastasis model of pancreatic cancer. Results: The secretion of COMP in serums is higher in pancreatic cancer patients than that in normal individuals, and it is highest in pancreatic cancer patients with liver metastasis. The expression of HSF1, HSP90, HSP47, COMP, α-SMA and collagen I were elevated in activated human primary HSCs and LX2 cells co-cultured with CMpcs. Double immunofluorescence staining showed that the expression of COMP and nuclear translocation of HSF1 was prominently enhanced in activated HSCs and LX2, and it was reversed in the presence of KRIBB11or si-HSF1. The secretion of COMP in CMhscs/lx2 of activated HSCs or LX2 was also increased. CHIP-qPCR assay and dual-luciferase reporter system showed that HSF1 can act on the promoter region of COMP. The results of indirect co-culture model displayed that CMhscs/lx2 can notably facilitate the invasion of Panc-1cells, increase the expression of EMT markers, p-AKT, FOXM1, and promote the nuclear translocation of FOXM1. These effects were reserved by silencing CD36 (a receptor of COMP), si-FOXM1, treated with LY294002 (an inhibitor of AKT), or added with Anti-COMP neutralizing antibody. In the liver metastasis model in nude mice, KRIBB11 or anti-COMP neutralizing antibody, could inhibit the metastasis of pancreatic cancer cells. Conclusion: Our study demonstrated that HSCs in premetastatic niches activating HSF1-mediated COMP secretion promote liver metastasis of pancreatic cancer cells through CD36/AKT/FOXM1 signaling, which may provide a new strategy to prevent the metastasis of pancreatic cancer.