Osteopontin mediates glioblastoma-associated macrophage infiltration and is a potential therapeutic target.
J Clin Invest 2018 Nov 19 [Epub ahead of print]
Glioblastoma is highly enriched with macrophages, and osteopontin (OPN) expression levels correlate with glioma grade and the degree of macrophage infiltration; thus, we studied whether OPN plays a crucial role in immune modulation. Quantitative PCR, immunoblotting, and ELISA were used to determine OPN expression. Knockdown of OPN was achieved using complementary siRNA, shRNA, and CRISPR/Cas9 techniques, followed by a series of in vitro functional migration and immunological assays. OPN gene-deficient mice were used to examine the roles of non-tumor-derived OPN on survival of mice harboring intracranial gliomas. Patients with mesenchymal glioblastoma multiforme (GBM) show high OPN expression, a negative survival prognosticator. OPN is a potent chemokine for macrophages, and its blockade significantly impaired the ability of glioma cells to recruit macrophages. Integrin αvβ5 (ITGαvβ5) is highly expressed on glioblastoma-infiltrating macrophages and constitutes a major OPN receptor. OPN maintains the M2 macrophage gene signature and phenotype. Both tumor-derived and host-derived OPN were critical for glioma development. OPN deficiency in either innate immune or glioma cells resulted in a marked reduction in M2 macrophages and elevated T cell effector activity infiltrating the glioma. Furthermore, OPN deficiency in the glioma cells sensitized them to direct CD8+ T cell cytotoxicity. Systemic administration in mice of 4-1BB-OPN bispecific aptamers was efficacious, increasing median survival time by 68% (P < 0.05). OPN is thus an important chemokine for recruiting macrophages to glioblastoma, mediates crosstalk between tumor cells and the innate immune system, and has the potential to be exploited as a therapeutic target.
Wei, Jun; Marisetty, Anantha; Schrand, Brett; Gabrusiewicz, Konrad; Hashimoto, Yuuri; Ott, Martina; Grami, Zacharia; Kong, Ling-Yuan; Ling, Xiaoyang; Caruso, Hillary; Zhou, Shouhao; Wang, Y Alan; Fuller, Gregory N; Huse, Jason; Gilboa, Eli; Kang, Nannan; Huang, Xingxu; Verhaak, Roel G W; Li, Shulin; and Heimberger, Amy B, "Osteopontin mediates glioblastoma-associated macrophage infiltration and is a potential therapeutic target." (2018). Faculty Research Ahead of Print. 133.