The expression and function of E3 ligase SIAH2 in acute T lymphoblastic leukemia

The seven in absentia homolog 2 (SIAH2) protein plays a significant role in human cancer by regulating hypoxia-inducible factor-a (HIF-1α); however, its role in T-cell acute lymphoblastic leukemia (T-ALL) is less clear.

Immunofluorescence evaluation of SIAH2 protein expression and location were conducted in Jurkat cell (a T-ALL cell line) as well as in bone marrow mononuclear cells (BMMNCs) from T-ALL and idiopathic thrombocytopenic purpura (ITP) patients. The expression of SIAH2 mRNA was also examined by quantitative real-time PCR (qRT-PCR) in these cells. Lentivirus-packed shRNA targeting on SIAH2 (Lv-shSIAH2) was used to knock down SIAH2 expression in Jurkat cells. Cell proliferation, apoptosis, invasion and protein levels were then determined by CCK-8 assay, annexin V-PI assay, transwell and Western blotting, respectively.

The mRNA expression of SIAH2 in BMMNCs from primary T-ALL patients was significantly higher than cells from ITP patients (P=0.0312); There were significant positive associations between SIAH2 expression and the extramedullary infiltration (EMI) (P=0.0003), especially with the mediastinal lymph node metastasis (P=0.0168) and the pleural effusion (P=0.014). However, SIAH2 expression in T-ALL BMMNCs was not correlated with age, gender, white cell count or the clinical risk classification. SIAH2 knockdown by shRNA led to increased apoptosis and decreased proliferation, migration and invasion of Jurkat cells. Moreover, Prolyl Hydroxylase (PHD), P27 and Caspase3 were upregulated and HIF-1α, VEGF, VEGF Receptor 2, MMP-13, CyclinE1, C-myc and BCL2 were downregulated in SIAH2 knockdown Jurkat cells.

Our results suggest that SIAH2 regulates multi processes in T-ALL and may be an attractive therapeutic target.