Novel WT1 Target Genes: IL-2, IL-2RB, and IL-2RG Discovered during WT1 Silencing Using Lentiviral-Based RNAi in Myeloid Leukemia Cells

Wilms' tumor 1 (WT1) is a transcription factor which plays a major role in cell proliferation, differentiation, survival, and apoptosis. WT1 was first identified as a tumor suppressor gene in Wilms' tumor. However, overexpression of WT1 has been detected in several types of malignancy including some types of leukemia. To investigate the molecular mechanism underlying WT1-mediated leukemogenesis, lentiviral-based siRNA was employed as a tool to suppress WT1 expression in the myeloid leukemia cell line, K562. Successfully, both WT1 RNA and protein levels were downregulated in the leukemia cells. The silencing of WT1 resulted in significant growth inhibition in WT1-siRNA-treated cells for 40 ± 7.0%, 44 ± 9.5%, and 88 ± 9.1% at 48, 72, and 96 hours posttransduction as compared with the control cells, respectively. By using apoptosis detection assays (caspase-3/7 activity and Annexin V-FITC/PI assays), WT1 silencing induced a higher degree of early and late apoptosis in siRNA-treated K562 as compared with the control cells. Interestingly, the expression of survival signaling genes, IL-2, IL-2RB, and IL-2RG, was also suppressed after WT1-siRNA treatment. In addition, the WT1 silencing also inhibited the S phase of the cell cycle and induced cell death. Our results indicated that WT1 silencing by siRNA can suppress cellular proliferation, induce apoptosis, and reduce S phase fraction of K562 cells. Moreover, transcriptional modulation of IL-2, IL-2RB, and IL2-2RG expression by WT1 was likely involved in this phenotypic change. Overall, this study confirmed the oncogenic role of WT1 in myeloid leukemia and discovered the new target genes of WT1 which are likely involved in WT1-mediated leukemogenesis.