Eriocalyxin B induces apoptosis in lymphoma cells through multiple cellular signaling pathways
Received 7 August 2009; received in revised form 7 December 2009; accepted 22 December 2009. published online 04 January 2010.
Objective
Eriocalyxin B (EriB) is a natural diterpenoid purified from Isodon eriocalyx var. laxiflora and possesses strong antileukemic activity. In this study, we further investigated its effect and mechanism of action in human lymphoma.
Materials and Methods
In vitro, a series of B- and T-lymphoma cells were treated with EriB. Cell apoptosis was analyzed using flow cytometric assay. Expression of proteins related to apoptosis and cell signal transduction were assessed using Western blot. In vivo antitumor activity of EriB was examined in murine xenograft B- and T-lymphoma models, with in situ cell apoptosis detected by terminal deoxytransferase-catalyzed DNA nick-end labeling assay.
Results
EriB significantly inhibited lymphoma cell proliferation and induced apoptosis in association with caspase activation. Antiapoptotic Bcl-2 family members Bcl-2 and Bcl-xL were downregulated, with proapoptotic member Bax stable or upregulated, resulting in reduced Bcl-2/Bax and Bcl-xL/Bax ratios. Meanwhile, multiple signal transduction pathways were involved in lymphoma cell apoptosis in response to EriB, including inhibition of nuclear factor (NF)-κB and AKT pathways, and the activation of extracellular signal-related kinase (ERK) pathway. AKT inactivation was related to increased expression of cyclin-dependent kinase inhibitor P21, decreased expression of antiapoptotic phosphorylated form of Bad, and NF-κB activator IκB kinase α/β. ERK activation corresponded to reactive oxygen species production and could be blocked by antioxidant dithiothreitol. In murine xenograft lymphoma models, EriB remarkably inhibited tumor growth and induced in situ tumor cell apoptosis.
Conclusion
These findings broaden the value of EriB as a promising candidate targeting apoptosis cascade in treatment of hematological malignancies.
aState Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
bPôle de Recherches Franco-Chinois en Science du Vivant et Génomique, Laboratory of Molecular Pathology, Shanghai, China
cState Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
Offprint requests to: Wei-Li Zhao, M.D., Ph.D., State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, 197 Rui Jin Er Road, Shanghai 200025, China
∗ Drs. Zhang, Jiang, and Q.-S. Chen equally contributed to this work.
ABSTRACT