Lipopolysaccharide-induced M1-type Macrophages Enhance T Cell Activity and Promote the Apoptosis of Hepatocellular Carcinoma Cells.

[INTRODUCTION] Hepatocellular carcinoma (HCC) is the most common type of liver cancer. M1 macrophages exhibit dual roles in the tumor microenvironment (TME), but the specific mechanisms underlying their involvement in HCC remain unclear.

[METHODS] M1-polarized macrophages were differentiated from THP-1 monocytes employing Phorbol 12-Myristate 13-Acetate (PMA) and lipopolysaccharide (LPS). Then, macrophage activity was determined based on Mean Fluorescence Intensity (MFI), and their metabolic capacity was assessed according to extracellular acidification rate (ECAR) and Oxygen Consumption Rate (OCR). Quantitative Real-Time PCR (qRT-PCR) was performed to assess the expression of polarization- related genes.

[RESULTS] The results showed that LPS at a concentration higher than 10 ng/mL significantly affected the viability of macrophages differentiated from THP-1 monocytes but promoted the MFI of CD86. At the same time, LPS treatment notably enhanced the M1 polarization of macrophages, as evidenced by the upregulated expression of markers related to the M1 phenotype. Moreover, the mitochondrial oxidative metabolism of M1 macrophages shifted toward aerobic glycolysis under LPS treatment. When T-cells and HCC cells were co-cultured with M1 macrophages, the reactivity of T cells was enhanced, and the level of Bax (an apoptosis-enhancer) was increased. At the same time, the expression of Bcl-2 (an apoptosis-suppressor) was suppressed.

[DISCUSSION] LPS-induced M1 macrophages exert antitumor effects through metabolic reprogramming and immune modulation, though further mechanistic studies are needed.

[CONCLUSIONS] M1 macrophages inhibit HCC progression by activating T cells and inducing tumor cell apoptosis, offering novel insights for HCC immunotherapy.