PTGER4 and acute myeloid leukemia: The most highly expressed GPCRs in AML are CXCR4, CD97, PTGER4, PTGER2, EMR2, GPR183, FPR1, C3AR1 and C5AR1. Except for FPR1 and C5AR1, these GPCRs show little inter-specimen variability (Figure 1 and Supplementary Table 5).