Abstract
The aim of this study was to determine the polarization of macrophages in the tumor microenvironment, as well as the effect of soluble factors secreted from these polarized macrophages on etoposide-induced cancer cell apoptosis. We investigated the effect of soluble factors secreted from the supernatant of PC3 cells treated with TLR4 and TLR8 agonists, and etoposide on macrophage polarization at the protein level through flow cytometry and enzyme-linked immunosorbent assay. We further explored the cell cycle distribution and phagocytic activity of THP-1 cells by flow cytometry. To imitate the relationship between cancer cells and tumor-associated macrophages (TAMs), we cocultured macrophages with etoposide-treated PC3 cells. After the incubation, the apoptosis in cancer cells was assessed through FACS analysis and by annexin V and PI staining. Our results demonstrate that protein expression of M1 and M2 markers confirmed the upregulation of M1 markers upon etoposide treatment, and mixed M1/M2 phenotype upon treatment with TLR agonists-treated PC3 supernatant. In coculture methods, our results demonstrate that the apoptosis of etoposide-treated cancer cells increases in the presence of M0 macrophages and THP-1 cells incubated with the supernatant of TLR4 agonists-treated PC3 cells. These results indicate clear protective effects of M0 macrophages and THP-1 cells incubated with the supernatant of PC3 cells treated with TLR4 agonists (THP-1 + SUP + TLR4a) on etoposide-induced cancer cell apoptosis.