CD27 and acute myeloid leukemia: Protein levels of p-C-raf and p-MEK1/2 were significantly increased when CD27-AS1 was upregulated, and knockdown of CD27-AS1 led to opposite effects in both HL-60 and KG-1 cells (Fig. 5a, b), indicating that CD27-AS1 activated MAPK signaling pathway in the AML cells.