RACK1 and acute myeloid leukemia: Just recently, it was reported that Rack1 promoted proliferation of THP-1 cell, one acute myeloid leukemia (AML) cell line, by enhancing glycogen synthase kinase 3β (GSK3β) activity through de-phosphorylation at Ser9, whereas Rack1 knockdown did not enhance phosphorylation of GSK3β in THP1 cells, indicating that other mechanisms might be involved9.