Eriocalyxin B induces apoptosis in lymphoma cells through multiple cellular signaling pathways.
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.


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)-kappaB 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-kappaB activator IkappaB kinase alpha/beta. 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.


CONCLUSIONS
These findings broaden the value of EriB as a promising candidate targeting apoptosis cascade in treatment of hematological malignancies.
Zhang
Yi-Wen
YW
State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Jiang
Xiao-Xing
XX
Chen
Qiu-Sheng
QS
Shi
Wen-Yu
WY
Wang
Lan
L
Sun
Han-Dong
HD
Shen
Zhi-Xiang
ZX
Chen
Zhu
Z
Chen
Sai-Juan
SJ
Zhao
Wei-Li
WL
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004224:Diterpenes / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases; D005434:Flow Cytometry; D006801:Humans; D020287:In Situ Nick-End Labeling; D019169:Jurkat Cells; D008223:Lymphoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism
D004224:Diterpenes; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C516552:eriocalyxin B; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D053148:Caspase 3