Because prostaglandin E1 was identified in a connectivity map analysis to elicit changes in gene expression similar to those in Tcf1–/–Lef1–/– LSCs, and prostaglandin E1 impairs the activity of LSCs, it is possible that prostaglandins also regulate KLF4 in CML, as seen during macrophage polarization61–63. The gene discussed is LEF1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.