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Open Access Research

Notch1 is required for hypoxia-induced proliferation, invasion and chemoresistance of T-cell acute lymphoblastic leukemia cells

Jie Zou1, Peng Li1, Fei Lu1, Na Liu1, Jianjian Dai1, Jingjing Ye1, Xun Qu2, Xiulian Sun3, Daoxin Ma1, Jino Park4 and Chunyan Ji1*

Author Affiliations

1 Department of Hematology, Qilu Hospital of Shandong University, Jinan, Shandong, 107 West Wenhua Road, Jinan, Shandong, 250012, People’s Republic of China

2 Institute of Basic Medical Sciences, Qilu Hospital of, Shandong University,, Jinan, Shandong, Pepole’s Republic of China

3 Otolaryngology Laboratory, Qilu Hospital, of Shandong University, Jinan, Shandong, People’s Republic of China

4 Mary Babb Randolph Cancer Center, West Virginia University School of Medicine, Morgantown, WV, USA

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Journal of Hematology & Oncology 2013, 6:3  doi:10.1186/1756-8722-6-3

Published: 5 January 2013

Abstract

Background

Notch1 is a potent regulator known to play an oncogenic role in many malignancies including T-cell acute lymphoblastic leukemia (T-ALL). Tumor hypoxia and increased hypoxia-inducible factor-1α (HIF-1α) activity can act as major stimuli for tumor aggressiveness and progression. Although hypoxia-mediated activation of the Notch1 pathway plays an important role in tumor cell survival and invasiveness, the interaction between HIF-1α and Notch1 has not yet been identified in T-ALL. This study was designed to investigate whether hypoxia activates Notch1 signalling through HIF-1α stabilization and to determine the contribution of hypoxia and HIF-1α to proliferation, invasion and chemoresistance in T-ALL.

Methods

T-ALL cell lines (Jurkat, Sup-T1) transfected with HIF-1α or Notch1 small interference RNA (siRNA) were incubated in normoxic or hypoxic conditions. Their potential for proliferation and invasion was measured by WST-8 and transwell assays. Flow cytometry was used to detect apoptosis and assess cell cycle regulation. Expression and regulation of components of the HIF-1α and Notch1 pathways and of genes related to proliferation, invasion and apoptosis were assessed by quantitative real-time PCR or Western blot.

Results

Hypoxia potentiated Notch1 signalling via stabilization and activation of the transcription factor HIF-1α. Hypoxia/HIF-1α-activated Notch1 signalling altered expression of cell cycle regulatory proteins and accelerated cell proliferation. Hypoxia-induced Notch1 activation increased the expression of matrix metalloproteinase-2 (MMP2) and MMP9, which increased invasiveness. Of greater clinical significance, knockdown of Notch1 prevented the protective effect of hypoxia/HIF-1α against dexamethasone-induced apoptosis. This sensitization correlated with losing the effect of hypoxia/HIF-1α on Bcl-2 and Bcl-xL expression.

Conclusions

Notch1 signalling is required for hypoxia/HIF-1α-induced proliferation, invasion and chemoresistance in T-ALL. Pharmacological inhibitors of HIF-1α or Notch1 signalling may be attractive interventions for T-ALL treatment.

Keywords:
T-cell acute lymphoblastic leukemia; Hypoxia; HIF-1α; Notch1; Proliferation; Invasion; Chemoresistance