FZD6 and acute myeloid leukemia: This list includes GPCRs previously described as important for AML cell biology, such as CXCR4,24 as well as GPCRs that have a role in hematopoietic stem cell engraftment, such as C3AR1 and PTGER2. 25, 26 In addition, 19 receptors are downregulated in AML cells including adhesion GPCRs like LPHN1, GPR125, GPR56, CELSR3 and GPR126, protease-activated receptors (F2R and F2RL1) and the Frizzled family members SMO and FZD6.