HIF1A and neoplasm: HIF-1α, which is regulated at the protein level by oxygen dependent enzymes and, hence, allows for tissue hypoxia detection, showed nuclear positive staining in all the tumor tissues from the three groups but with a less prominent intensity in exosomes-inoculated tumors in comparison with vehicle (p < 0.001) and lysed exosomes-inoculated tumors (p < 0.01) (Figure 7E).