Triggering receptors expressed on myeloid cells 1 (TREM-1) is a novel molecule that modulates inflammatory responses. Hepatocellular carcinoma (HCC) is a well-known type of inflammation-related cancer. However, TREM-1 expression and its direct effects on HCC cells have not been previously determined.

Western blotting, quantitative reverse transcription-PCR (qRT-PCR), and immunofluorescence were used to detect TREM-1 expression. TREM-1 upregulation by pcDNA (mammalian expression vector with the CMV promoter) and its downregulation by shRNA (short hairpin RNA) were used to determine the function of this molecule. Transwell, CCK-8, cell cycle, and apoptosis assays were used to detect the effects of TREM-1 on HCC cells. Immunohistochemical staining of samples from a cohort of 322 HCC patients was used to determine the prognostic value of TREM-1.

TREM-1 investigation through Western blot, qRT-PCR, and immunofluorescence analyses revealed that TREM-1 was expressed in HCC cells and tumor tissues. Functional experiments suggested that TREM-1 significantly promoted proliferation, invasion, and inhibited apoptosis of HCC cells. Inflammatory cytokine profiles under TREM-1 up- or downregulation indicated the majority of proinflammation cytokines significantly and positively correlated with TREM-1 expression, including IL-1β, TNF-α, and MCP-1. Western blot analyses revealed that p65, STAT3, ERK, and AKT might be the downstream effectors of TREM-1 signal transduction. High TREM-1 expression correlated significantly with increased recurrence and poorer survival in HCC patients, and it was an independent prognostic factor for recurrence (P = 0.009).

TREM-1 was found to be expressed in HCC cells and to be a prognostic factor for the clinical outcome of HCC.