PI3K Inhibition by BKM120 Results in Antiproliferative Effects on Corticotroph Tumor Cells

Purpose: Cushing’s disease is associated with significant morbidity, thus additional tumor-directed drugs with the potential to exert antineoplastic effects on corticotroph adenoma cells are desired. The PI3K (phosphoinositide-3-kinase)/AKT (protein kinase B) pathway, which plays regulatory roles in cell survival and proliferation, is activated in pituitary adenomas. The present study evaluated the effects of BKM120 (Buparlisib), an oral PI3K inhibitor, in corticotroph tumor cells. Methods: AtT-20/D16v-F2 mouse pituitary corticotroph tumor cells were treated with increasing concentrations of BKM120 or vehicle. Cell viability was measured using MTS-based assay. Apoptosis was evaluated by Annexin V staining. ACTH levels were measured in the culture supernatants by chemiluminescent immunometric assay. Cell cycle analysis was performed by propidium iodide DNA staining and flow cytometry. Gene expression of cell cycle regulators (Cdkn1b, Rb1, Ccnd1, Cdk4, Cdk2, and Myc) was assessed by qPCR. Protein expression of p27, p70 S6 Kinase, p85 S6 Kinase, and phosphorylated AKT was assessed by Western blot. Results: Treatment with BKM120 decreased AtT-20/D16v-F2 cell proliferation and ACTH levels in the cell culture supernatants. Furthermore, BKM120 treatment diminished the phosphorylation of AKT at residue 473, increased p27 expression and induced a G0/G1 cell cycle arrest. Conclusion:In vitro inhibition of PI3K/AKT pathway by BKM120 resulted in antiproliferative effects on corticotroph tumor cells, decreasing cell viability and ACTH production. These encouraging findings shape the path for further experiments with the inhibition of PI3K/AKT pathway in Cushing’s disease.