Case CCC Molecular Oncology Program member Khalid Sossey-Alaoui, PhD, and Thomas Jefferson University's Lucia Languino, PhD, conducted a collaborative study that appears in a recent Journal of Extracellular Vesicles. The study, Expression of the αVβ3 integrin affects prostate cancer sEV cargo and density and promotes sEV pro-tumorigenic activity in vivo through a GPI-anchored receptor, NgR2, examines the importance of extracellular vesicles and integrins in the progression and metastasis of prostate cancer through the modulation of the tumor microenvironment.
It is known that small extracellular vesicles (sEVs) are released from cancer cells and contribute to cancer progression via crosstalk with recipient cells. To examine the impact of αVβ3 expression on sEV protein content, density, and function, the team isolated sEVs by iodixanol density gradients and characterized them by nanoparticle tracking analysis, immunoblotting, and single vesicle analysis. The team's proteomic profile of sEVs containing αVβ3 showed downregulation of typical effectors involved in apoptosis and necrosis and upregulation of tumor cell survival factors compared to control sEVs.
Furthermore, they demonstrated that the expression of αVβ3 in sEVs caused a distinct reposition of EV markers (Alix, CD81, CD9) to a low-density sEV subpopulation which is independent of extracellular matrix (ECM) protein interactions with sEVs. This sEV subset contained αVβ3 and an αVβ3 downstream effector, NgR2, a novel marker for NEPrCa. The study also indicated that sEVs containing αVβ3 are loaded with higher amounts of NgR2 as compared to sEVs that do not express αVβ3.
Mechanistically, Sossey-Alaoui, Languino, and colleagues demonstrated that sEVs containing NgR2 did not affect the sEV marker profile, but when injected in vivo intratumorally, they promoted tumor growth and induced NED, and that sEVs expressing NgR2 increased the activation of focal adhesion kinase (FAK), a known promoter of cancer cell proliferation, in recipient cells. Finally, the study indicated that NgR2 mimics the effect of sEVs containing αVβ3 since it displays increased growth of NgR2 transfectants in vivo, as compared to control cells. Overall, the results of the collaborative effort describe the changes that occur in cargo, density, and functions of cancer cell-derived sEVs containing the αVβ3 integrin and its effector, NgR2, without affecting the sEV tetraspanin profiles.