Transthyretin promotes the invasion of combined hepatocellular cholangiocarcinoma by tumor‐associated macrophages

BACKGROUND: Patients with combined hepatocellular‐cholangiocarcinoma (cHCC‐CCA) have limited treatment options and poor prognosis. Tumor‐associated macrophages (TAMs) are the most abundant infiltrating immune cells in the tumor microenvironment and promote tumor stemness, proliferation, invasion and metastasis. Evidence suggested that transthyretin (TTR) influenced the prolifetation and invasion functions of different tumors and play an essential role in the tumor microenvironment. AIMS: To investigate the involvement of TTR in TAMs affecting the invasion of cHCC‐CCA. METHODS AND RESULTS: Data sets obtained from the Gene Expression Omnibus database were integrated. Differentially expressed genes (DEGs) were obtained using R software, and modules associated with cHCC‐CCA were screened by weighted gene co‐expression network analysis (WGCNA). Human THP‐1 cells were induced to differentiate into macrophages and then co‐cultured with HCCC9810 cells and tumor necrosis factor‐α (TNF‐α) to simulate the inflammatory microenvironment of cHCC‐CAA. In addition, small interfering RNA against TTR was transfected into HCCC9810 cells, and recombinant TTR and ERK and AKT‐specific inhibitors were added to HCCC9810 cells, respectively; after that, the levels of NF‐κB protein and phosphorylated ERK and AKT were measured. The invasive abilities of HCCC9810 cells were also tested. One hundred forty‐five DEGs were associated with cHCC‐CCA, of which TTR was up‐regulated. Turquoise modules containing TTR in WGCNA were most significantly associated with cHCC‐CCA. TTR was highly expressed in HCCC9810 compared to Huh‐28. HCCC9810 showed enhanced invasive capacity after co‐culture with TNF‐α + macrophages (p < .05). After interfering with TTR, the invasive ability of HCCC9810 was diminished, accompanied by decreased expression of NF‐κB, p‐ERK1/2, and p‐AKT (p < .05). After treating HCCC9810 with ERK and AKT‐specific inhibitors, the invasive ability of HCCC9810 was diminished, accompanied by decreased expression of NF‐κB and TTR (p < .05). CONCLUSION: TTR can promote the invasive ability of cHCC‐CCA by regulating AKT/NF‐κB and ERK pathways with the assistance of TAMs.