For verifying whether erythroid differentiation associated with CDK9 on chronic myeloid leukemia cell lines and primary CML cells, we first constructed lentiviral recombinants expressing shRNA targeting CDK9 gene on K562 cells and evaluated knock down efficiency by using RT-qPCR (Additional file 1: Fig. S1a). Here, CDK9 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.