Exosomes secreted from ST3G5high cancer cells (ST3G5high‐cExos) were found to contain high levels of hypoxia‐inducible factor 1‐alpha (HIF1α) and accumulated in MSs via uptake in macrophages (MΦs) owing to increased expression of sialic acid‐binding Ig‐like lectin 1 (CD169; also known as SIGLEC1). Here, HIF1A is linked to cancer.