Background: Gastric cancer (GC) is one of the most common causes of cancer death. Hypoxia is an important property of the tumor microenvironment of GC. Increasing evidence demonstrates that tumor-associated macrophages are related to the metastasis of GC, while the precise mechanism of how hypoxic macrophages affect tumor progression is still not fully understood.
Aims: To examine whether the mediators released from hypoxic macrophages contribute to the invasion and proliferation of GC cells.
Methods: Cell Counting Kit-8 was utilized to determine the proliferation of SGC7901 and MKN45 cells. The invasion of SGC7901 and MKN45 cells was measured by transwell invasion assay. Expression of VEGF mRNA in THP-1-derived macrophages was determined by RT-PCR, and protein level of VEGF in the culture medium was detected by ELISA.
Results: The proliferation and invasion of SGC7901 and MKN45 cells were dramatically increased after treatment with conditioned medium (CM) collected from THP-1-derived macrophages under hypoxia (H-CM), and the phosphorylation of Akt and p38 in SGC7901 and MKN45 cells was also up-regulated by H-CM stimulation. Notably, blockage of PI3K-Akt or p38 MAP kinase abolished the effects of H-CM on the proliferation and invasion of SGC7901 and MKN45 cells. Furthermore, VEGF was increased in macrophages after hypoxia and administration with nintedanib, an inhibitor of VEGFR, significantly decreases the phosphorylation of Akt and p38, as well as the proliferation and invasion of SGC7901 and MKN45 cells in response to H-CM.
Conclusions: Our findings suggest that hypoxia-injured macrophages contribute to the proliferation and invasion of GC cells through the release of mediators such as VEGF.
Keywords: Gastric cancer; Hypoxia; Macrophage; VEGF.