Inhibition of the VEGF signaling pathway attenuates tumor‑associated macrophage activity in liver cancer

Abstract

Tumor-associated macrophage (TAMs) are paramount for tumor progression and immune tolerance in the tumor microenvironment of various types of cancer, including liver cancer. The aim of the present study was to investigate the effect of vascular endothelial growth factor (VEGF) inhibition on TAM polarization and function during their interactions with macrophages and liver cancer cells. TAMs were induced by culturing M0 macrophages with cancer cell-conditioned medium. TAMs cultured with cancer cell-conditioned medium and vascular endothelial growth factor (VEGF) inhibitor were defined as modified TAMs, and the expression levels of TAM-associated markers and VEGF receptor 2 were evaluated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The effects of TAMs and modified TAMs on cancer cell proliferation and migration were investigated using conditioned medium. Programmed death-ligand 1 (PD-L1) mRNA expression in modified TAMs and cancer cells cultured in modified TAM-conditioned medium (TAM-CM) for 48 h was examined using RT-qPCR. In order to investigate signaling pathways in macrophages, western blot analysis was performed. CD163 and CD206 and M2 macrophage marker expression was upregulated in TAMs and modified TAMs. Modified TAM-CM exhibited a decreased ability to promote cancer cell proliferation and migration in comparison with the use of TAM-CM. The VEGF concentration was significantly higher in the TAMs than in M0 macrophages; however, the modified TAMs displayed a significantly lower VEGF secretion than TAMs. PD-L1 expression was decreased in modified TAMs as compared with TAMs. Western blot analysis revealed that the Akt/mTOR signaling pathway was significantly suppressed in the modified TAMs compared with TAMs. It was observed that TAMs cultured in a VEGF-depleted environment displayed lower secretion levels of cytokines involved in tumor progression and a decreased immune tolerance-inducing ability. On the whole, the results of the present study suggested that VEGF inhibition in TAMs may be a potential therapeutic target for liver cancer.

Multiplexed analysis of signalling proteins at the single-immune cell level

“…36,37 Therefore, we hypothesize that the VEGF from MCF-7 cells is a factor that is involved in the polarization of the macrophages towards TAMs. In addition, and in line with previous observations, 35 TAMs secrete in turn higher amounts of VEGF when polarized in VEGF-containing media compared to polarization in VEGF-depleted media.…”

“…In addition, and in line with previous observations 35 , TAMs secrete in turn higher amounts of VEGF when polarized in VEGFcontaining medium compared to polarization in VEGF-depleted media. Please do not adjust margins Please do not adjust margins proteins IL-10 and VEGF are more highly expressed in cells that do not express the tumour-suppressive protein TNF-α.…”

“…Additionally, we incubated unpolarized macrophages in the upconcentrated supernatant of breast cancer cells (MCF-7 cell line) to simulate the impact of the tumour microenvironment on the polarization of macrophages 35 . These macrophages show a protein pattern similar to M2 macrophages with a significantly increased expression of all measured proteins (median IL-10: 1,12 ng/mL, TNF-α: 1.43 ng/mL, VEGF: 4.81 ng/mL).…”

Effect of duodenal-jejunal bypass on diabetes in the early postoperative period

“…RT-qPCR was performed as previously described 52 . Briefly, an RNeasy Mini Kit (Qiagen, Hilden, Germany) was used to extract RNA, according to the manufacturer’s instructions.…”

Macrophages as a Potential Immunotherapeutic Target in Solid Cancers

“…Tumor-derived VEGF induces macrophage polarization, which then secretes more VEGF to further induce angiogenesis. In a recent study, inhibition of VEGF prevented TAM polarization and attenuated the TAM-mediated secretion of tumor-promoting cytokines [ 74 ]. In addition, the presence of VEGF receptors on TAMs also forms an autocrine loop that receives autocrine signals upon VEGF binding with the receptors and enhances the pro-angiogenic properties of TAMs.…”