苏州大学 赵昀 博士
TWIST2 was deregulated in human acute myeloid leukemia and might play a tumor suppressor role
Twist is a kind of bHLH factor, which specifies the mesoderm development of Drosophila. Mammalian Twist contains two members, Twist-1 and Twist-2, which are essential regulators of osteoblasts and muscle development. In addition, they have critical implications in normal EMT (epithelia-mesenchymal transition) process, cancer initiation and metastasis. Recently Twist-2 was identified as a negative regulator of normal myeloid progenitor cells in Twist-2 deficient mice, which made it appealing to explore the expression and function of its human homology in normal and leukemic progenitor cells.
To address this, we initially found that the transcript expression of TWIST2 from CD34+ cells of 30 AML patients (2 M0, 8 M1, 7 M2, 4 M4, 7 M5 and 2 M6) in comparison with those of their normal counterparts from 6 healthy donors was nearly 5-fold decreased (P<0.05).
A lentiviral vector to overexpress TWIST2 was then constructed, which could efficiently deliver TWIST2 into AML cells. TWIST2 dramatically suppressed the growth of several AML cell lines.
Moreover, the tumourgenesis capacities of control and TWIST2 overexpressed cells were assessed in nude mice (7/7 vs. 0/8 for Dami cells and 6/7 vs. 1/8 for THP-1 cells), which strongly demonstrated the inhibitory role of TWIST2.
To obtain molecular insights of how TWIST2 suppressed the proliferation and tumourgenesis capacities, the differentially expressed genes between TWIST2 overexpressed and control THP-1cells were analyzed with microarray (Agilent 44K, 4 independent experiments). 139 genes including CCND1, TERT and BCL11A were down-regulated in TWIST2 overexpressed cells compared with control cells; conversely, 523 genes including CDKN1A (p21Cip1), CDKN2D (p19), and ID2 were up-regulated (P<0.05). The validation of 15 out of 17 genes with Q-RT-PCR using THP-1 cells was consistent with the microarray data (n=4, P<0.05).
As several cell cycle regulators were differentially expressed upon TWIST2 overexpression, cell cycle analysis was carried out to show that more TWIST2 overexpressed cells resided in the G0/G1 phase (61% vs. 44%, n=2, P<0.05) and accordingly less in the G2/S/M phase (39% vs. 56%, n=2, P<0.05) compared with control cells. The differential expression of CCND1 was further confirmed with western blots.
Thus we have demonstrated that the novel hematopoietic regulator TWIST2 was deregulated in AML, and its overexpression was capable to suppress the growth and tumourgenesis capacity of these cells. The global gene expression data and their validations suggested that TWIST2 had a novel function in AML cells potentially as a “tumor suppressor” partially through the regulation of cell cycle.