Toll-like receptor-4 agonist inhibits motility and invasion of hepatoblastoma HepG2 cells in vitro

Background: Expression of toll-like receptor-4 (TLR4) on tumor cells is known to mediate innate immune responses that influence tumor cell growth and migration. This study aimed to characterize TLR4 expression and elucidate its functional significance in human hepatoblastoma (HB) cells. Procedure: Immunohistochemistry (IHC) was used to determine TLR4 expression level and its distribution pattern in HB liver tissues. Transcripts of tumor necrosis factor (TNF)-α, interleukin (IL)-8, matrix metalloproteinase (MMP)-2, MMP-13, tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2 in HB HepG2 cells with lipopolysacharide (LPS) treatment were measured by quantitative PCR. Soluble cytokines and peptides in conditioned media were measured by ELISA. MMP-2 activity was determined by using gelatin zymography. Cell motility and invasiveness was determined using wound healing migration and Matrigel invasion assays, respectively. Results: TLR4 IHC staining demonstrated that TLR4 overexpression in HB liver tissues dramatically vanished after chemotherapy. In vitro study using an HB cell line, HepG2, showed that TLR4 agonist, LPS, significantly decreased transcripts of IL-8 and TNF-α, but did not affect MMP-13 mRNA level. By contrast, LPS only down-regulated IL-8 production and MMP-2 gelatinolytic activity. The latter might be in part due to the increased levels of MMP-2/TIMP-2 complex in conditioned media, thus leading to the decreased motility and invasiveness of HepG2 cells. Conclusions: HB cells overexpress TLR4, whereas TLR4 agonistic treatment inhibits migration and invasion of HB HepG2 cells. These findings suggest that TLR4 signaling pathway is a potential therapeutic target for control of HB tumor progression.