STAT3 and glioblastoma: The key proteins loaded to hypoxic exosomes include, for example, HIF-1α (nasopharyngeal carcinoma) [153], lysyl oxidases, PDGFs, thrombospondin-1 (TSP-1), plasminogen activator inhibitor 1 (PAI1), caveolin-1 (all in glioblastoma) [154–156], annexin II (prostate cancer) [157], or signal transducer and activator of transcription 3 (STAT3) (ovarian cancer) [152].