Cox-2 expression and PGE2 generation are ARC/IL1β-dependent. The apoptosis repressor with caspase recruitment domain (ARC) protein, regulated by β-catenin, is an integral component of an IL1β/PGE2/β-catenin circuit. Cox-2/PGE2, regulated by ARC and induced by AML-MSC co-culture contributes to MSC-mediated chemoprotection in AML. The gene discussed is IL1B; the disease is acute myeloid leukemia.