Estrogen‐related receptor β activation and isoform shifting by cdc2‐like kinase inhibition restricts migration and intracranial tumor growth in glioblastoma

Glioblastoma (GBM; grade 4 glioma) is a highly aggressive and incurable tumor. GBM has recently been characterized as highly dependent on alternative splicing, a critical driver of tumor heterogeneity and plasticity. Estrogen‐related receptor β (ERR‐β) is an orphan nuclear receptor expressed in the brain, where alternative splicing of the 3' end of the pre‐mRNA leads to the production of 3 validated ERR‐β protein products: ERR‐β short form (ERR‐βsf), ERR‐β2, and ERR‐β exon 10 deleted. Our prior studies have shown the ERR‐β2 isoform to play a role in G2/M cell cycle arrest and induction of apoptosis, in contrast to the function of the shorter ERR‐βsf isoform in senescence and G1 cell cycle arrest. In this study, we sought to better define the role of the proapoptotic ERR‐β2 isoform in GBM. We show that the ERR‐β2 isoform is located not only in the nucleus but also in the cytoplasm. ERR‐β2 suppresses GBM cell migration and interacts with the actin nucleation‐promoting factor cortactin, and an ERR‐β agonist is able to remodel the actin cytoskeleton and similarly suppress GBM cell migration. We further show that inhibition of the splicing regulatory cdc2‐like kinases in combination with an ERR‐β agonist shifts isoform expression in favor of ERR‐β2 and potentiates inhibition of growth and migration in GBM cells and intracranial tumors.—Tiek, D. M., Khatib, S. A., Trepicchio, C. J., Heckler, M. M., Divekar, S. D., Sarkaria, J. N., Glasgow, E., Riggins, R. B. Estrogen‐related receptor β activation and isoform shifting by cdc2‐like kinase inhibition restricts migration and intracranial tumor growth in glioblastoma. FASEB J. 33, 13476–13491 (2019). www.fasebj.org