Akt Regulates Extracellular Vesicle Secretion in Hypoxia-adapted Multiple Myeloma RPMI8226 Cells

Hypoxia, a characteristic of the tumor microenvironment, affects tumor cell behavior by altering the secretion pattern of extracellular vesicles (EVs). We investigated the regulatory mechanism and biological significance of EV secretion in multiple myeloma (MM) cells grown under hypoxic culture conditions.

Human MM cell lines (RPMI8226 and AMO1) were exposed to long-term hypoxia to generate hypoxia-adapted (HA) cells. EVs released into the culture supernatant were quantified by enzyme-linked immunosorbent assay. The expression of proteins involved in hypoxia-induced signaling was analyzed by western blotting. EV secretion was inhibited using GW4869.

Exposure to hypoxia altered the amount of EVs secreted and the phosphorylation levels of Akt and its target molecule AS160. Pharmacological inhibition of Akt phosphorylation suppressed the increase in EV secretion and phosphorylated AS160 expression in HA RPMI8226 cells. GW4869 induced apoptosis in HA RPMI8226 cells, but not in the parental cell line, in the presence or absence of the secretome including EVs. GW4869 altered the expression of proteins related to glycolysis (HK2) and autophagy (LC3).

Akt signaling modulates EV secretion to maintain homeostasis in RPMI8226 cells exposed to hypoxic conditions.