Fusion toxin BLyS-gelonin inhibits growth of malignant human B cell lines in vitro and in vivo.
B lymphocyte stimulator (BLyS) is a member of the TNF superfamily of cytokines. The biological activity of BLyS is mediated by three cell surface receptors: BR3/BAFF-R, TACI and BCMA. The expression of these receptors is highly restricted to B cells, both normal and malignant. A BLyS-gelonin fusion toxin (BLyS-gel) was generated consisting of the recombinant plant-derived toxin gelonin fused to the N-terminus of BLyS and tested against a large and diverse panel of B-NHL cell lines. Interestingly, B-NHL subtypes mantle cell lymphoma (MCL), diffuse large B cell lymphoma (DLBCL) and B cell precursor-acute lymphocytic leukemia (BCP-ALL) were preferentially sensitive to BLyS-gel mediated cytotoxicity, with low picomolar EC(50) values. BLyS receptor expression did not guarantee sensitivity to BLyS-gel, even though the construct was internalized by both sensitive and resistant cells. Resistance to BLyS-gel could be overcome by treatment with the endosomotropic drug chloroquine, suggesting BLyS-gel may become trapped within endosomal/lysosomal compartments in resistant cells. BLyS-gel induced cell death was caspase-independent and shown to be at least partially mediated by the "ribotoxic stress response." This response involves activation of p38 MAPK and JNK/SAPK, and BLyS-gel mediated cytotoxicity was inhibited by the p38/JNK inhibitor SB203580. Finally, BLyS-gel treatment was shown to localize to sites of disease, rapidly reduce tumor burden, and significantly prolong survival in xenograft mouse models of disseminated BCP-ALL, DLBCL, and MCL. Together, these findings suggest BLyS has significant potential as a targeting ligand for the delivery of cytotoxic "payloads" to malignant B cells.
Department of Oncology Research, Human Genome Sciences, Inc., Rockville, Maryland, United States of America.
Troy A
TA
Luster
Ipsita
I
Mukherjee
Jeffrey A
JA
Carrell
Yun Hee
YH
Cho
Jeffrey
J
Gill
Lizbeth
L
Kelly
Andy
A
Garcia
Christopher
C
Ward
Luke
L
Oh
Stephen J
SJ
Ullrich
Thi-Sau
TS
Migone
Robin
R
Humphreys
D000818:Animals; D053264:B-Cell Activating Factor / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016393:Lymphoma, B-Cell / Q000188:drug therapy*; D051379:Mice; D016513:Mice, SCID; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use*; D054789:Ribosome Inactivating Proteins, Type 1 / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
D053264:B-Cell Activating Factor; D011993:Recombinant Fusion Proteins; D054789:Ribosome Inactivating Proteins, Type 1; C025674:GEL protein, Gelonium multiflorum