Hypoxia-derived exosomes induce putative altered pathways in biosynthesis and ion regulatory channels in glioblastoma cells

Abstract

Hypoxia, a hallmark characteristic of glioblastoma (GBM) induces changes in the transcriptome and the proteome of tumor cells. We discovered that hypoxic stress produces significant qualitative and quantitative changes in the protein content of secreted exosomes from GBM cells. Among the proteins found to be selectively elevated in hypoxic exosomes were protein-lysine 6-oxidase (LOX), thrombospondin-1 (TSP1), vascular derived endothelial factor (VEGF) and a disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1), well studied contributors to tumor progression, metastasis and angiogenesis. Our findings demonstrate that hypoxic exosomes induce differential gene expression in recipient glioma cells. Glioma cells stimulated with hypoxic exosomes showed a marked upregulation of small nucleolar RNA, C/D box 116–21 (SNORD116-21) transcript among others while significantly downregulated the potassium voltage-gated channel subfamily J member 3 (KCNJ3) message. This differential expression of certain genes is governed by the protein cargo being transferred via exosomes. Additionally, compared to normoxic exosomes, hypoxic exosomes increased various angiogenic related parameters vis-à-vis, overall tube length, branching intervals and length of isolated branches studied in tube formation assay with endothelial progenitor cells (EPCs). Thus, the intercellular communication facilitated via exosomes secreted from hypoxic GBM cells induce marked changes in the expression of genes in neighboring normoxic tumor cells and possibly in surrounding stromal cells, many of which are involved in cancer progression and treatment resistance mechanisms.

How hypoxia regulate exosomes in ischemic diseases and cancer microenvironment?

“…Endothelial progenitor cells also exhibited elevated expression of angiogenic‐related factors after exposure to hypoxic exosomes. All these findings suggested that GBM cells respond to hypoxia stress through changing the transcriptome and proteome of their exosomes, and mediate their angiogenesis, progression, and treatment resistance mechanisms …”

Triple-Negative Primary Breast Tumors Induce Supportive Premetastatic Changes in the Extracellular Matrix and Soluble Components of the Lung Microenvironment

“…EV Isolation Human breast cancer cells (MCF10A, T47D, MCF7, SUM159, MDA-MB-231, 231-LM, 231-BoM and LRCP17) were grown to approximately 80% confluency in normal growth media. Culture media were replaced with serum-free media, and cells were incubated under hypoxic culture conditions (37 • C, 1% CO 2 ) for 48 h to enhance EV production and packaging [46,47]. Culture media were harvested, and EVs were isolated as previously described [48].…”

Human Cardiac Progenitor Cells Enhance Exosome Release and Promote Angiogenesis Under Physoxia

“…A study of MSC-EVs observed increased proliferation, migration, and tube formation with hypoxia-derived EVs (1% O 2 for 72 h) as compared to those from normoxic conditions (Bian et al, 2014). Another study on glioma cells observed significantly increased tube formation by endothelial progenitor cells when treated with hypoxia (<0.5% O 2 for undisclosed time) versus normoxiaderived EVs; however, the treatments equally protected glioma cells from oxidative stress (Kore et al, 2018). Similarly, human cardiosphere-derived EVs isolated under 18 and 1% O 2 showed increased tube formation as compared to PBS control.…”