Hypoxia and Macrophages Act in Concert Towards a Beneficial Outcome in Colon Cancer

Abstract

In colon cancer, the prognostic value of macrophages is controversial, and it is still unknown how hypoxia modulates macrophage-cancer cell crosstalk. To unravel this, co-cultures of human primary macrophages and colon cancer cells were performed at 20% and 1% O₂, followed by characterization of both cellular components. Different colon cancer patient cohorts were analyzed for hypoxia and immune markers, and their association with patient overall survival was established. A positive correlation between <i>HIF1A</i> and <i>CD68</i> in colon cancer patients was identified but, unexpectedly, in cases with higher macrophage infiltration, <i>HIF1A</i> expression was associated with a better prognosis, in contrast to breast, gastric, and lung cancers. Under hypoxia, co-cultures' secretome indicated a shift towards a pro-inflammatory phenotype. These alterations occurred along with increased macrophage phagocytic activity and decreased SIRPα expression. Cancer cells were more invasive and exhibited higher CD47 expression. We hypothesize that the better prognosis associated with <i>HIF1A</i>^High<i>CD68</i>^High tumors could occur due to macrophagic pro-inflammatory pressure. Indeed, we found that tumors <i>HIF1A</i>^High<i>CD68</i>^High expressed increased levels of <i>CD8A</i>, which is positively correlated with <i>HIF1A</i>. In conclusion, we show that in colon cancer, hypoxia drives macrophages into a pro-inflammatory phenotype, concomitant with increased infiltration of anti-tumor immune cells, favoring better disease outcome.