On the contrary, activation of EP4 with the FDA-approved agonist misoprostol or PGE1 reduced CD34+ cells in a xenograft model of chronic myelogenous leukemia (CML) (Li F. et al., 2017), suggesting a context-dependent effect of prostaglandins in stemness. Here, CD34 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.