Prostaglandin E2 stimulates cAMP signaling and re-sensitizes human leukemia cells to glucocorticoid-induced cell death.

Glucocorticoid (GC) resistance remains a clinical challenge in pediatric acute lymphoblastic leukemia (ALL) where response to GC is a reliable prognostic indicator. To identify GC resistance pathways, we conducted a genome-wide, survival-based, shRNA screen in murine T cell acute lymphoblastic leukemia (T-ALL) cells. Genes identified in the screen interfere with cAMP signaling and are under-expressed in GC resistant or relapsed ALL patients. Silencing of the cAMP activating guanine nucleotide binding protein, alpha stimulating Gnas gene, interfered with GC-induced gene expression, resulting in dexamethasone resistance in vitro and in vivo. We demonstrate that cAMP signaling synergizes with dexamethasone to enhance cell death in GC resistant human T-ALL cells. We find the E prostanoid receptor 4 expressed in T-ALL samples and demonstrate that Prostaglandin E2 (PGE2) increases intracellular cAMP, potentiates GC-induced gene expression and sensitizes human T-ALL samples to dexamethasone in vitro and in vivo. These findings identify PGE2 as a target for GC re-sensitization in relapsed pediatric T-ALL.